v2.2.2

* GSN support

Add base Context contract

Add GSNContext and tests

Add RelayHub deployment to tests

Add RelayProvider integration, complete GSNContext tests

Switch dependency to openzeppelin-gsn-provider

Add default txfee to provider

Add basic signing recipient

Sign more values

Add comment clarifying RelayHub's msg.data

Make context constructors internal

Rename SigningRecipient to GSNRecipientSignedData

Add ERC20Charge recipients

Harcode RelayHub address into GSNContext

Fix Solidity linter errors

Run server from binary, use gsn-helpers to fund it

Migrate to published @openzeppelin/gsn-helpers

Silence false-positive compiler warning

Use GSN helper assertions

Rename meta-tx to gsn, take out of drafts

Merge ERC20 charge recipients into a single one

Rename GSNRecipients to Bouncers

Add GSNBouncerUtils to decouple the bouncers from GSNRecipient

Add _upgradeRelayHub

Store RelayHub address using unstructored storage

Add IRelayHub

Add _withdrawDeposits to GSNRecipient

Add relayHub version to recipient

Make _acceptRelayedCall and _declineRelayedCall easier to use

Rename GSNBouncerUtils to GSNBouncerBase, make it IRelayRecipient

Improve GSNBouncerBase, make pre and post sender-protected and optional

Fix GSNBouncerERC20Fee, add tests

Add missing GSNBouncerSignature test

Override transferFrom in __unstable__ERC20PrimaryAdmin

Rhub address slot reduced by 1

Rename relay hub changed event

Use released gsn-provider

* move gsn to all caps

* update to gsn contracts in solidity/master

* Adapt for ethereum-package

* update gsn related packages

* update dependencies to match contracts repo

* remove mocha bail option

* add changelog entry

* add constructors to mocks

* use unstructured storage for bouncer implementations

.circleci/config.yml

@@ -0,0 +1,82 @@
+version: 2
+# 2.1 does not yet support local run
+# unless with workaround. For simplicity just use it.
+# https://github.com/CircleCI-Public/circleci-cli/issues/79
+
+aliases:
+  - &defaults
+    docker:
+      - image: circleci/node:8
+
+  - &npm_install_if_necessary
+    run:
+      name: Install npm dependencies
+      command: |
+        if [ ! -d node_modules ]; then
+          npm ci
+        fi
+
+  - &cache_key_node_modules
+    key: v1-node_modules-{{ checksum "package-lock.json" }}
+
+jobs:
+  dependencies:
+    <<: *defaults
+    steps:
+      - checkout
+      - restore_cache:
+          <<: *cache_key_node_modules
+      - *npm_install_if_necessary
+      - save_cache:
+          paths:
+            - node_modules
+          <<: *cache_key_node_modules
+
+  lint:
+    <<: *defaults
+    steps:
+      - checkout
+      - restore_cache:
+          <<: *cache_key_node_modules
+      - *npm_install_if_necessary
+      - run:
+          name: Linter
+          command: npm run lint
+  test:
+    <<: *defaults
+    steps:
+      - checkout
+      - restore_cache:
+          <<: *cache_key_node_modules
+      - *npm_install_if_necessary
+      - run:
+          name: Unit tests
+          command: npm run test
+  coverage:
+    docker:
+      - image: circleci/node:8
+    steps:
+      - checkout
+      - restore_cache:
+          <<: *cache_key_node_modules
+      - *npm_install_if_necessary
+      - run:
+          name: Unit tests with coverage report
+          command: npm run coverage
+
+      # TODO(xinbenlv, #1839): run SOLC_NIGHTLY to be run but allow it to fail.
+
+workflows:
+  version: 2
+  everything:
+    jobs:
+      - dependencies
+      - lint:
+          requires:
+            - dependencies
+      - test:
+          requires:
+            - dependencies
+      - coverage:
+          requires:
+            - dependencies

.env.example

@@ -1,5 +0,0 @@
-# configure your infura api key (not technically required)
-INFURA_API_KEY=
-
-# change the mnemonic that your hd wallet is seeded with
-MNEMONIC=

.eslintrc

@@ -1,22 +1,23 @@
 {
   "extends" : [
     "standard",
-    "plugin:promise/recommended"
+    "plugin:promise/recommended",
   ],
   "plugins": [
-    "promise"
+    "mocha-no-only",
+    "promise",
   ],
   "env": {
     "browser" : true,
     "node"    : true,
     "mocha"   : true,
-    "jest"    : true
+    "jest"    : true,
   },
   "globals" : {
     "artifacts": false,
     "contract": false,
     "assert": false,
-    "web3": false
+    "web3": false,
   },
   "rules": {
 
@@ -49,6 +50,8 @@
     "semi": ["error", "always"],
     "space-before-function-paren": ["error", "always"],
 
+    "mocha-no-only/mocha-no-only": ["error"],
+
     "promise/always-return": "off",
     "promise/avoid-new": "off",
   }

.github/ISSUE_TEMPLATE.md

@@ -1,34 +0,0 @@
-## 🎉 Description
-
-<!-- Briefly describe the issue you are experiencing (or the feature you want to see added to OpenZeppelin). Tell us what you were trying to do and what happened instead. **Remember, this is _not_ a place to ask for help debugging code; for that, we welcome you in the [OpenZeppelin Slack Channel](https://slack.openzeppelin.org/).** -->
-
-- [ ] 🐛 This is a bug report.
-- [ ] 📈 This is a feature request.
-
-<!-- Please check one of the above by placing an x in the box. -->
-
-## 💻 Environment
-
-Next, we need to know what your environment looks like.
-
-- Which version of OpenZeppelin are you using?
-- What network are you deploying to? Ganache? Ropsten?
-- How are you deploying your OpenZeppelin-backed contracts? truffle? Remix? Let us know!
-
-## 📝 Details
-
-Describe the problem you have been experiencing in more detail. Include as much information as you think is relevant. Keep in mind that transactions can fail for many reasons; context is key here.
-
-## 🔢 Code To Reproduce Issue [ Good To Have ]
-
-Please remember that with sample code it's easier to reproduce the bug and it's much faster to fix it.
-
-```
-insert short code snippets here
-```
-
-<!-- If your code is larger, consider linking us to a repo illustrating your issue. -->
-
-## 👍 Other Information
-
-<!-- List any other information that is relevant to your issue. Error logs, related issues, suggestions on how to fix, Stack Overflow links, forum links, etc. -->

.github/ISSUE_TEMPLATE/bug_report.md

@@ -0,0 +1,21 @@
+---
+name: Bug report
+about: Report a bug in OpenZeppelin
+
+---
+
+<!-- Briefly describe the issue you're experiencing. Tell us what you were trying to do and what happened instead. -->
+
+<!-- Remember, this is not a place to ask for help debugging code. For that, we welcome you in the OpenZeppelin Slack channel: https://slack.openzeppelin.org/. -->
+
+**💻 Environment**
+
+<!-- Tell us what version of OpenZeppelin you're using, and how you're using it: Truffle, Remix, etc. -->
+
+**📝 Details**
+
+<!-- Describe the problem you have been experiencing in more detail. Include as much information as you think is relevant. Keep in mind that transactions can fail for many reasons; context is key here. -->
+
+**🔢 Code to reproduce bug**
+
+<!-- We will be able to better help if you provide a minimal example that triggers the bug. -->

.github/ISSUE_TEMPLATE/feature_request.md

@@ -0,0 +1,14 @@
+---
+name: Feature request
+about: Suggest an idea for OpenZeppelin
+
+---
+
+**🧐 Motivation**
+<!-- Is your feature request related to a specific problem? Is it just a crazy idea? Tell us about it! -->
+
+**📝 Details**
+<!-- Please describe your feature request in detail. -->
+
+<!-- Make sure that you have reviewed the OpenZeppelin Contributor Guidelines. -->
+<!-- https://github.com/OpenZeppelin/openzeppelin-solidity/blob/master/CONTRIBUTING.md -->

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,17 +1,22 @@
 <!-- 0. 🎉 Thank you for submitting a PR! -->
 
-<!-- 1. **Does this close any open issues?** If so, list them here. If not, remove the `Fixes #` line. -->
+<!-- 1. Does this close any open issues? Please list them below. -->
+
+<!-- Keep in mind that new features have a better chance of being merged fast if
+they were first discussed and designed with the maintainers. If there is no
+corresponding issue, please consider opening one for discussion first! -->
 
 Fixes #
 
-# 🚀 Description
-
-<!-- 2. Describe the changes introduced in this pull request -->
+<!-- 2. Describe the changes introduced in this pull request. -->
 <!--    Include any context necessary for understanding the PR's purpose. -->
 
-<!-- 3. Before submitting, please review the following checklist: -->
-
-- [ ] 📘 I've reviewed the [OpenZeppelin Contributor Guidelines](../blob/master/CONTRIBUTING.md)
-- [ ] ✅ I've added tests where applicable to test my new functionality.
-- [ ] 📖 I've made sure that my contracts are well-documented.
-- [ ] 🎨 I've run the JS/Solidity linters and fixed any issues (`npm run lint:fix`).
+<!-- 3. Before submitting, please make sure that you have:
+  - reviewed the OpenZeppelin Contributor Guidelines
+    (https://github.com/OpenZeppelin/openzeppelin-solidity/blob/master/CONTRIBUTING.md),
+  - added tests where applicable to test new functionality,
+  - made sure that your contracts are well-documented,
+  - run the Solidity linter (`npm run lint:sol`) and fixed any issues,
+  - run the JS linter and fixed any issues (`npm run lint:fix`), and
+  - updated the changelog, if applicable.
+-->

.gitignore

@@ -32,8 +32,13 @@ npm-debug.log
 # truffle build directory
 build/
 
-# lol macs
-.DS_Store/
+# macOS
+.DS_Store
 
 # truffle
 .node-xmlhttprequest-*
+
+.openzeppelin/.session
+
+# IntelliJ IDE
+.idea

.node-version

@@ -1 +0,0 @@
-v8.9.1

.openzeppelin/kovan.json

@@ -0,0 +1,923 @@
+{
+  "contracts": {
+    "PaymentSplitter": {
+      "address": "0x6CE7dEca802e0c5c133f7cbbE719B1da305A6Ae5",
+      "constructorCode": "608060405234801561001057600080fd5b50610be3806100206000396000f3fe",
+      "bodyBytecodeHash": "6f1453b45140bc5e426ffccfcae058daa1fc53439580e3c9e6b7f73aac54c5d8",
+      "localBytecodeHash": "1b0f3688284b1c14c41ce636762c4504188969cb0e5a052159b61b87cbd4e8a8",
+      "deployedBytecodeHash": "1b0f3688284b1c14c41ce636762c4504188969cb0e5a052159b61b87cbd4e8a8",
+      "types": {
+        "t_bool": {
+          "id": "t_bool",
+          "kind": "elementary",
+          "label": "bool"
+        },
+        "t_uint256": {
+          "id": "t_uint256",
+          "kind": "elementary",
+          "label": "uint256"
+        },
+        "t_array:50<t_uint256>": {
+          "id": "t_array:50<t_uint256>",
+          "valueType": "t_uint256",
+          "length": "50",
+          "kind": "array",
+          "label": "uint256[50]"
+        },
+        "t_mapping<t_uint256>": {
+          "id": "t_mapping<t_uint256>",
+          "valueType": "t_uint256",
+          "label": "mapping(key => uint256)",
+          "kind": "mapping"
+        },
+        "t_address": {
+          "id": "t_address",
+          "kind": "elementary",
+          "label": "address"
+        },
+        "t_array:dyn<t_address>": {
+          "id": "t_array:dyn<t_address>",
+          "valueType": "t_address",
+          "length": "dyn",
+          "kind": "array",
+          "label": "address[]"
+        }
+      },
+      "storage": [
+        {
+          "contract": "Initializable",
+          "path": "@openzeppelin/upgrades/contracts/Initializable.sol",
+          "label": "initialized",
+          "astId": 13400,
+          "type": "t_bool",
+          "src": "757:24:153"
+        },
+        {
+          "contract": "Initializable",
+          "path": "@openzeppelin/upgrades/contracts/Initializable.sol",
+          "label": "initializing",
+          "astId": 13402,
+          "type": "t_bool",
+          "src": "876:25:153"
+        },
+        {
+          "contract": "Initializable",
+          "path": "@openzeppelin/upgrades/contracts/Initializable.sol",
+          "label": "______gap",
+          "astId": 13458,
+          "type": "t_array:50<t_uint256>",
+          "src": "1951:29:153"
+        },
+        {
+          "contract": "PaymentSplitter",
+          "path": "contracts/payment/PaymentSplitter.sol",
+          "label": "_totalShares",
+          "astId": 9541,
+          "type": "t_uint256",
+          "src": "555:28:120"
+        },
+        {
+          "contract": "PaymentSplitter",
+          "path": "contracts/payment/PaymentSplitter.sol",
+          "label": "_totalReleased",
+          "astId": 9543,
+          "type": "t_uint256",
+          "src": "589:30:120"
+        },
+        {
+          "contract": "PaymentSplitter",
+          "path": "contracts/payment/PaymentSplitter.sol",
+          "label": "_shares",
+          "astId": 9547,
+          "type": "t_mapping<t_uint256>",
+          "src": "626:43:120"
+        },
+        {
+          "contract": "PaymentSplitter",
+          "path": "contracts/payment/PaymentSplitter.sol",
+          "label": "_released",
+          "astId": 9551,
+          "type": "t_mapping<t_uint256>",
+          "src": "675:45:120"
+        },
+        {
+          "contract": "PaymentSplitter",
+          "path": "contracts/payment/PaymentSplitter.sol",
+          "label": "_payees",
+          "astId": 9554,
+          "type": "t_array:dyn<t_address>",
+          "src": "726:25:120"
+        },
+        {
+          "contract": "PaymentSplitter",
+          "path": "contracts/payment/PaymentSplitter.sol",
+          "label": "______gap",
+          "astId": 9800,
+          "type": "t_array:50<t_uint256>",
+          "src": "3251:29:120"
+        }
+      ],
+      "warnings": {
+        "hasConstructor": false,
+        "hasSelfDestruct": false,
+        "hasDelegateCall": false,
+        "hasInitialValuesInDeclarations": false,
+        "uninitializedBaseContracts": [],
+        "storageUncheckedVars": [],
+        "storageDiff": []
+      }
+    },
+    "StandaloneERC20": {
+      "address": "0x65e22dDa13EFa3A7fadd3EF62afC815110748308",
+      "constructorCode": "608060405234801561001057600080fd5b5061290d806100206000396000f3fe",
+      "bodyBytecodeHash": "fffcccf2a7439f83b3eb59e01f5217ea14764c782fde08c6edd511f0c7d1e742",
+      "localBytecodeHash": "be0848d29ef0345b76e9810a67328a1deb1a7b07dd050c9212d3099430cf4222",
+      "deployedBytecodeHash": "be0848d29ef0345b76e9810a67328a1deb1a7b07dd050c9212d3099430cf4222",
+      "types": {
+        "t_bool": {
+          "id": "t_bool",
+          "kind": "elementary",
+          "label": "bool"
+        },
+        "t_uint256": {
+          "id": "t_uint256",
+          "kind": "elementary",
+          "label": "uint256"
+        },
+        "t_array:50<t_uint256>": {
+          "id": "t_array:50<t_uint256>",
+          "valueType": "t_uint256",
+          "length": "50",
+          "kind": "array",
+          "label": "uint256[50]"
+        },
+        "t_string": {
+          "id": "t_string",
+          "kind": "elementary",
+          "label": "string"
+        },
+        "t_uint8": {
+          "id": "t_uint8",
+          "kind": "elementary",
+          "label": "uint8"
+        },
+        "t_mapping<t_uint256>": {
+          "id": "t_mapping<t_uint256>",
+          "valueType": "t_uint256",
+          "label": "mapping(key => uint256)",
+          "kind": "mapping"
+        },
+        "t_struct<Roles.Role>": {
+          "id": "t_struct<Roles.Role>",
+          "kind": "struct",
+          "label": "Roles.Role",
+          "members": [
+            {
+              "label": "bearer",
+              "astId": 1222,
+              "type": "t_mapping<t_bool>",
+              "src": "150:32:8"
+            }
+          ]
+        },
+        "t_mapping<t_bool>": {
+          "id": "t_mapping<t_bool>",
+          "valueType": "t_bool",
+          "label": "mapping(key => bool)",
+          "kind": "mapping"
+        }
+      },
+      "storage": [
+        {
+          "contract": "Initializable",
+          "path": "@openzeppelin/upgrades/contracts/Initializable.sol",
+          "label": "initialized",
+          "astId": 13400,
+          "type": "t_bool",
+          "src": "757:24:153"
+        },
+        {
+          "contract": "Initializable",
+          "path": "@openzeppelin/upgrades/contracts/Initializable.sol",
+          "label": "initializing",
+          "astId": 13402,
+          "type": "t_bool",
+          "src": "876:25:153"
+        },
+        {
+          "contract": "Initializable",
+          "path": "@openzeppelin/upgrades/contracts/Initializable.sol",
+          "label": "______gap",
+          "astId": 13458,
+          "type": "t_array:50<t_uint256>",
+          "src": "1951:29:153"
+        },
+        {
+          "contract": "ERC20Detailed",
+          "path": "contracts/token/ERC20/ERC20Detailed.sol",
+          "label": "_name",
+          "astId": 10735,
+          "type": "t_string",
+          "src": "397:20:128"
+        },
+        {
+          "contract": "ERC20Detailed",
+          "path": "contracts/token/ERC20/ERC20Detailed.sol",
+          "label": "_symbol",
+          "astId": 10737,
+          "type": "t_string",
+          "src": "423:22:128"
+        },
+        {
+          "contract": "ERC20Detailed",
+          "path": "contracts/token/ERC20/ERC20Detailed.sol",
+          "label": "_decimals",
+          "astId": 10739,
+          "type": "t_uint8",
+          "src": "451:23:128"
+        },
+        {
+          "contract": "ERC20Detailed",
+          "path": "contracts/token/ERC20/ERC20Detailed.sol",
+          "label": "______gap",
+          "astId": 10791,
+          "type": "t_array:50<t_uint256>",
+          "src": "1112:29:128"
+        },
+        {
+          "contract": "ERC20",
+          "path": "contracts/token/ERC20/ERC20.sol",
+          "label": "_balances",
+          "astId": 10239,
+          "type": "t_mapping<t_uint256>",
+          "src": "767:46:125"
+        },
+        {
+          "contract": "ERC20",
+          "path": "contracts/token/ERC20/ERC20.sol",
+          "label": "_allowed",
+          "astId": 10245,
+          "type": "t_mapping<t_uint256>",
+          "src": "820:66:125"
+        },
+        {
+          "contract": "ERC20",
+          "path": "contracts/token/ERC20/ERC20.sol",
+          "label": "_totalSupply",
+          "astId": 10247,
+          "type": "t_uint256",
+          "src": "893:28:125"
+        },
+        {
+          "contract": "ERC20",
+          "path": "contracts/token/ERC20/ERC20.sol",
+          "label": "______gap",
+          "astId": 10612,
+          "type": "t_array:50<t_uint256>",
+          "src": "7729:29:125"
+        },
+        {
+          "contract": "MinterRole",
+          "path": "contracts/access/roles/MinterRole.sol",
+          "label": "_minters",
+          "astId": 1448,
+          "type": "t_struct<Roles.Role>",
+          "src": "286:27:10"
+        },
+        {
+          "contract": "MinterRole",
+          "path": "contracts/access/roles/MinterRole.sol",
+          "label": "______gap",
+          "astId": 1547,
+          "type": "t_array:50<t_uint256>",
+          "src": "1096:29:10"
+        },
+        {
+          "contract": "ERC20Mintable",
+          "path": "contracts/token/ERC20/ERC20Mintable.sol",
+          "label": "______gap",
+          "astId": 10840,
+          "type": "t_array:50<t_uint256>",
+          "src": "760:29:129"
+        },
+        {
+          "contract": "PauserRole",
+          "path": "contracts/access/roles/PauserRole.sol",
+          "label": "_pausers",
+          "astId": 1567,
+          "type": "t_struct<Roles.Role>",
+          "src": "286:27:11"
+        },
+        {
+          "contract": "PauserRole",
+          "path": "contracts/access/roles/PauserRole.sol",
+          "label": "______gap",
+          "astId": 1666,
+          "type": "t_array:50<t_uint256>",
+          "src": "1096:29:11"
+        },
+        {
+          "contract": "Pausable",
+          "path": "contracts/lifecycle/Pausable.sol",
+          "label": "_paused",
+          "astId": 5401,
+          "type": "t_bool",
+          "src": "367:20:42"
+        },
+        {
+          "contract": "Pausable",
+          "path": "contracts/lifecycle/Pausable.sol",
+          "label": "______gap",
+          "astId": 5482,
+          "type": "t_array:50<t_uint256>",
+          "src": "1444:29:42"
+        },
+        {
+          "contract": "ERC20Pausable",
+          "path": "contracts/token/ERC20/ERC20Pausable.sol",
+          "label": "______gap",
+          "astId": 10963,
+          "type": "t_array:50<t_uint256>",
+          "src": "1209:29:130"
+        }
+      ],
+      "warnings": {
+        "hasConstructor": false,
+        "hasSelfDestruct": false,
+        "hasDelegateCall": false,
+        "hasInitialValuesInDeclarations": false,
+        "uninitializedBaseContracts": [],
+        "storageUncheckedVars": [
+          {
+            "contract": "MinterRole",
+            "path": "contracts/access/roles/MinterRole.sol",
+            "label": "_minters",
+            "astId": 1448,
+            "type": "t_struct<Roles.Role>",
+            "src": "286:27:10"
+          },
+          {
+            "contract": "PauserRole",
+            "path": "contracts/access/roles/PauserRole.sol",
+            "label": "_pausers",
+            "astId": 1567,
+            "type": "t_struct<Roles.Role>",
+            "src": "286:27:11"
+          }
+        ],
+        "storageDiff": [
+          {
+            "action": "rename",
+            "updated": {
+              "index": 8,
+              "contract": "ERC20",
+              "path": "contracts/token/ERC20/ERC20.sol",
+              "label": "_allowed",
+              "astId": 10245,
+              "type": "t_mapping<t_uint256>",
+              "src": "820:66:125"
+            },
+            "original": {
+              "index": 8,
+              "contract": "ERC20",
+              "path": "contracts/token/ERC20/ERC20.sol",
+              "label": "_allowances",
+              "astId": 9135,
+              "type": "t_mapping<t_uint256>",
+              "src": "1410:69:115"
+            }
+          }
+        ]
+      }
+    },
+    "TokenVesting": {
+      "address": "0x94CeBcF32a18eA573C85293883f7D3352b360ec1",
+      "constructorCode": "608060405234801561001057600080fd5b506114d8806100206000396000f3fe",
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+        },
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+          "type": "t_bool",
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+        },
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+          "label": "______gap",
+          "astId": 13458,
+          "type": "t_array:50<t_uint256>",
+          "src": "1951:29:153"
+        },
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+          "label": "_owner",
+          "astId": 9325,
+          "type": "t_address",
+          "src": "317:22:118"
+        },
+        {
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+          "label": "______gap",
+          "astId": 9436,
+          "type": "t_array:50<t_uint256>",
+          "src": "2277:29:118"
+        },
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+          "label": "_beneficiary",
+          "astId": 4658,
+          "type": "t_address",
+          "src": "1148:28:36"
+        },
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+          "label": "_cliff",
+          "astId": 4660,
+          "type": "t_uint256",
+          "src": "1278:22:36"
+        },
+        {
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+          "label": "_start",
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+          "type": "t_uint256",
+          "src": "1306:22:36"
+        },
+        {
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+          "label": "_duration",
+          "astId": 4664,
+          "type": "t_uint256",
+          "src": "1334:25:36"
+        },
+        {
+          "contract": "TokenVesting",
+          "path": "contracts/drafts/TokenVesting.sol",
+          "label": "_revocable",
+          "astId": 4666,
+          "type": "t_bool",
+          "src": "1366:23:36"
+        },
+        {
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+          "label": "_released",
+          "astId": 4670,
+          "type": "t_mapping<t_uint256>",
+          "src": "1396:46:36"
+        },
+        {
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+          "label": "_revoked",
+          "astId": 4674,
+          "type": "t_mapping<t_bool>",
+          "src": "1448:42:36"
+        },
+        {
+          "contract": "TokenVesting",
+          "path": "contracts/drafts/TokenVesting.sol",
+          "label": "______gap",
+          "astId": 5016,
+          "type": "t_array:50<t_uint256>",
+          "src": "5852:29:36"
+        }
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+        "uninitializedBaseContracts": [],
+        "storageUncheckedVars": [],
+        "storageDiff": []
+      }
+    },
+    "StandaloneERC721": {
+      "address": "0xB1a160cD691cF3754AA4AE91ba6e2E18798CcE36",
+      "constructorCode": "608060405234801561001057600080fd5b506135c8806100206000396000f3fe",
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+        },
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+          "kind": "struct",
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+              "type": "t_uint256",
+              "src": "1021:14:30"
+            }
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+              "type": "t_mapping<t_bool>",
+              "src": "150:32:8"
+            }
+          ]
+        }
+      },
+      "storage": [
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+          "label": "initialized",
+          "astId": 13400,
+          "type": "t_bool",
+          "src": "757:24:153"
+        },
+        {
+          "contract": "Initializable",
+          "path": "@openzeppelin/upgrades/contracts/Initializable.sol",
+          "label": "initializing",
+          "astId": 13402,
+          "type": "t_bool",
+          "src": "876:25:153"
+        },
+        {
+          "contract": "Initializable",
+          "path": "@openzeppelin/upgrades/contracts/Initializable.sol",
+          "label": "______gap",
+          "astId": 13458,
+          "type": "t_array:50<t_uint256>",
+          "src": "1951:29:153"
+        },
+        {
+          "contract": "ERC165",
+          "path": "contracts/introspection/ERC165.sol",
+          "label": "_supportedInterfaces",
+          "astId": 5191,
+          "type": "t_mapping<t_bool>",
+          "src": "511:52:39"
+        },
+        {
+          "contract": "ERC165",
+          "path": "contracts/introspection/ERC165.sol",
+          "label": "______gap",
+          "astId": 5235,
+          "type": "t_array:50<t_uint256>",
+          "src": "1244:29:39"
+        },
+        {
+          "contract": "ERC721",
+          "path": "contracts/token/ERC721/ERC721.sol",
+          "label": "_tokenOwner",
+          "astId": 11595,
+          "type": "t_mapping<t_address>",
+          "src": "844:48:135"
+        },
+        {
+          "contract": "ERC721",
+          "path": "contracts/token/ERC721/ERC721.sol",
+          "label": "_tokenApprovals",
+          "astId": 11599,
+          "type": "t_mapping<t_address>",
+          "src": "948:52:135"
+        },
+        {
+          "contract": "ERC721",
+          "path": "contracts/token/ERC721/ERC721.sol",
+          "label": "_ownedTokensCount",
+          "astId": 11603,
+          "type": "t_mapping<t_struct<Counters.Counter>>",
+          "src": "1058:63:135"
+        },
+        {
+          "contract": "ERC721",
+          "path": "contracts/token/ERC721/ERC721.sol",
+          "label": "_operatorApprovals",
+          "astId": 11609,
+          "type": "t_mapping<t_bool>",
+          "src": "1176:73:135"
+        },
+        {
+          "contract": "ERC721",
+          "path": "contracts/token/ERC721/ERC721.sol",
+          "label": "______gap",
+          "astId": 12132,
+          "type": "t_array:50<t_uint256>",
+          "src": "11673:29:135"
+        },
+        {
+          "contract": "ERC721Enumerable",
+          "path": "contracts/token/ERC721/ERC721Enumerable.sol",
+          "label": "_ownedTokens",
+          "astId": 12183,
+          "type": "t_mapping<t_array:dyn<t_uint256>>",
+          "src": "460:50:137"
+        },
+        {
+          "contract": "ERC721Enumerable",
+          "path": "contracts/token/ERC721/ERC721Enumerable.sol",
+          "label": "_ownedTokensIndex",
+          "astId": 12187,
+          "type": "t_mapping<t_uint256>",
+          "src": "580:53:137"
+        },
+        {
+          "contract": "ERC721Enumerable",
+          "path": "contracts/token/ERC721/ERC721Enumerable.sol",
+          "label": "_allTokens",
+          "astId": 12190,
+          "type": "t_array:dyn<t_uint256>",
+          "src": "694:28:137"
+        },
+        {
+          "contract": "ERC721Enumerable",
+          "path": "contracts/token/ERC721/ERC721Enumerable.sol",
+          "label": "_allTokensIndex",
+          "astId": 12194,
+          "type": "t_mapping<t_uint256>",
+          "src": "793:51:137"
+        },
+        {
+          "contract": "ERC721Enumerable",
+          "path": "contracts/token/ERC721/ERC721Enumerable.sol",
+          "label": "______gap",
+          "astId": 12523,
+          "type": "t_array:50<t_uint256>",
+          "src": "8816:29:137"
+        },
+        {
+          "contract": "ERC721Metadata",
+          "path": "contracts/token/ERC721/ERC721Metadata.sol",
+          "label": "_name",
+          "astId": 12590,
+          "type": "t_string",
+          "src": "281:20:140"
+        },
+        {
+          "contract": "ERC721Metadata",
+          "path": "contracts/token/ERC721/ERC721Metadata.sol",
+          "label": "_symbol",
+          "astId": 12592,
+          "type": "t_string",
+          "src": "328:22:140"
+        },
+        {
+          "contract": "ERC721Metadata",
+          "path": "contracts/token/ERC721/ERC721Metadata.sol",
+          "label": "_tokenURIs",
+          "astId": 12596,
+          "type": "t_mapping<t_string>",
+          "src": "396:45:140"
+        },
+        {
+          "contract": "ERC721Metadata",
+          "path": "contracts/token/ERC721/ERC721Metadata.sol",
+          "label": "______gap",
+          "astId": 12725,
+          "type": "t_array:50<t_uint256>",
+          "src": "2849:29:140"
+        },
+        {
+          "contract": "MinterRole",
+          "path": "contracts/access/roles/MinterRole.sol",
+          "label": "_minters",
+          "astId": 1448,
+          "type": "t_struct<Roles.Role>",
+          "src": "286:27:10"
+        },
+        {
+          "contract": "MinterRole",
+          "path": "contracts/access/roles/MinterRole.sol",
+          "label": "______gap",
+          "astId": 1547,
+          "type": "t_array:50<t_uint256>",
+          "src": "1096:29:10"
+        },
+        {
+          "contract": "ERC721MetadataMintable",
+          "path": "contracts/token/ERC721/ERC721MetadataMintable.sol",
+          "label": "______gap",
+          "astId": 12795,
+          "type": "t_array:50<t_uint256>",
+          "src": "1055:29:141"
+        },
+        {
+          "contract": "PauserRole",
+          "path": "contracts/access/roles/PauserRole.sol",
+          "label": "_pausers",
+          "astId": 1567,
+          "type": "t_struct<Roles.Role>",
+          "src": "286:27:11"
+        },
+        {
+          "contract": "PauserRole",
+          "path": "contracts/access/roles/PauserRole.sol",
+          "label": "______gap",
+          "astId": 1666,
+          "type": "t_array:50<t_uint256>",
+          "src": "1096:29:11"
+        },
+        {
+          "contract": "Pausable",
+          "path": "contracts/lifecycle/Pausable.sol",
+          "label": "_paused",
+          "astId": 5401,
+          "type": "t_bool",
+          "src": "367:20:42"
+        },
+        {
+          "contract": "Pausable",
+          "path": "contracts/lifecycle/Pausable.sol",
+          "label": "______gap",
+          "astId": 5482,
+          "type": "t_array:50<t_uint256>",
+          "src": "1444:29:42"
+        },
+        {
+          "contract": "ERC721Pausable",
+          "path": "contracts/token/ERC721/ERC721Pausable.sol",
+          "label": "______gap",
+          "astId": 12940,
+          "type": "t_array:50<t_uint256>",
+          "src": "865:29:143"
+        }
+      ],
+      "warnings": {
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+        "hasSelfDestruct": false,
+        "hasDelegateCall": false,
+        "hasInitialValuesInDeclarations": false,
+        "uninitializedBaseContracts": [],
+        "storageUncheckedVars": [
+          {
+            "contract": "ERC721",
+            "path": "contracts/token/ERC721/ERC721.sol",
+            "label": "_ownedTokensCount",
+            "astId": 11603,
+            "type": "t_mapping<t_struct<Counters.Counter>>",
+            "src": "1058:63:135"
+          },
+          {
+            "contract": "MinterRole",
+            "path": "contracts/access/roles/MinterRole.sol",
+            "label": "_minters",
+            "astId": 1448,
+            "type": "t_struct<Roles.Role>",
+            "src": "286:27:10"
+          },
+          {
+            "contract": "PauserRole",
+            "path": "contracts/access/roles/PauserRole.sol",
+            "label": "_pausers",
+            "astId": 1567,
+            "type": "t_struct<Roles.Role>",
+            "src": "286:27:11"
+          }
+        ],
+        "storageDiff": []
+      }
+    }
+  },
+  "solidityLibs": {},
+  "proxies": {},
+  "manifestVersion": "2.2",
+  "frozen": true,
+  "app": {
+    "address": "0xf5829D56998ccC1405B7eAbCCAC78164AF270D39"
+  },
+  "package": {
+    "address": "0xB6F8F11b166D526932ee04ffe4D25B810f619E34"
+  },
+  "provider": {
+    "address": "0x6290189B262fe198A51e3a3ac06A09c4782D3bD3"
+  },
+  "version": "2.2.2"
+}

.openzeppelin/mainnet.json

@@ -0,0 +1,882 @@
+{
+  "contracts": {
+    "PaymentSplitter": {
+      "address": "0xc6FBEe275DC5a4e7c6bc94bEd156fe10ee09eAba",
+      "constructorCode": "608060405234801561001057600080fd5b50610be3806100206000396000f3fe",
+      "bodyBytecodeHash": "6f1453b45140bc5e426ffccfcae058daa1fc53439580e3c9e6b7f73aac54c5d8",
+      "localBytecodeHash": "1b0f3688284b1c14c41ce636762c4504188969cb0e5a052159b61b87cbd4e8a8",
+      "deployedBytecodeHash": "1b0f3688284b1c14c41ce636762c4504188969cb0e5a052159b61b87cbd4e8a8",
+      "types": {
+        "t_bool": {
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+          "kind": "elementary",
+          "label": "bool"
+        },
+        "t_uint256": {
+          "id": "t_uint256",
+          "kind": "elementary",
+          "label": "uint256"
+        },
+        "t_array:50<t_uint256>": {
+          "id": "t_array:50<t_uint256>",
+          "valueType": "t_uint256",
+          "length": "50",
+          "kind": "array",
+          "label": "uint256[50]"
+        },
+        "t_mapping<t_uint256>": {
+          "id": "t_mapping<t_uint256>",
+          "valueType": "t_uint256",
+          "label": "mapping(key => uint256)",
+          "kind": "mapping"
+        },
+        "t_address": {
+          "id": "t_address",
+          "kind": "elementary",
+          "label": "address"
+        },
+        "t_array:dyn<t_address>": {
+          "id": "t_array:dyn<t_address>",
+          "valueType": "t_address",
+          "length": "dyn",
+          "kind": "array",
+          "label": "address[]"
+        }
+      },
+      "storage": [
+        {
+          "contract": "Initializable",
+          "path": "@openzeppelin/upgrades/contracts/Initializable.sol",
+          "label": "initialized",
+          "astId": 13400,
+          "type": "t_bool",
+          "src": "757:24:153"
+        },
+        {
+          "contract": "Initializable",
+          "path": "@openzeppelin/upgrades/contracts/Initializable.sol",
+          "label": "initializing",
+          "astId": 13402,
+          "type": "t_bool",
+          "src": "876:25:153"
+        },
+        {
+          "contract": "Initializable",
+          "path": "@openzeppelin/upgrades/contracts/Initializable.sol",
+          "label": "______gap",
+          "astId": 13458,
+          "type": "t_array:50<t_uint256>",
+          "src": "1951:29:153"
+        },
+        {
+          "contract": "PaymentSplitter",
+          "path": "contracts/payment/PaymentSplitter.sol",
+          "label": "_totalShares",
+          "astId": 9541,
+          "type": "t_uint256",
+          "src": "555:28:120"
+        },
+        {
+          "contract": "PaymentSplitter",
+          "path": "contracts/payment/PaymentSplitter.sol",
+          "label": "_totalReleased",
+          "astId": 9543,
+          "type": "t_uint256",
+          "src": "589:30:120"
+        },
+        {
+          "contract": "PaymentSplitter",
+          "path": "contracts/payment/PaymentSplitter.sol",
+          "label": "_shares",
+          "astId": 9547,
+          "type": "t_mapping<t_uint256>",
+          "src": "626:43:120"
+        },
+        {
+          "contract": "PaymentSplitter",
+          "path": "contracts/payment/PaymentSplitter.sol",
+          "label": "_released",
+          "astId": 9551,
+          "type": "t_mapping<t_uint256>",
+          "src": "675:45:120"
+        },
+        {
+          "contract": "PaymentSplitter",
+          "path": "contracts/payment/PaymentSplitter.sol",
+          "label": "_payees",
+          "astId": 9554,
+          "type": "t_array:dyn<t_address>",
+          "src": "726:25:120"
+        },
+        {
+          "contract": "PaymentSplitter",
+          "path": "contracts/payment/PaymentSplitter.sol",
+          "label": "______gap",
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+        },
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+          "label": "_allowed",
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+          "type": "t_mapping<t_uint256>",
+          "src": "820:66:125"
+        },
+        {
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+          "label": "_totalSupply",
+          "astId": 10247,
+          "type": "t_uint256",
+          "src": "893:28:125"
+        },
+        {
+          "contract": "ERC20",
+          "path": "contracts/token/ERC20/ERC20.sol",
+          "label": "______gap",
+          "astId": 10612,
+          "type": "t_array:50<t_uint256>",
+          "src": "7729:29:125"
+        },
+        {
+          "contract": "MinterRole",
+          "path": "contracts/access/roles/MinterRole.sol",
+          "label": "_minters",
+          "astId": 1448,
+          "type": "t_struct<Roles.Role>",
+          "src": "286:27:10"
+        },
+        {
+          "contract": "MinterRole",
+          "path": "contracts/access/roles/MinterRole.sol",
+          "label": "______gap",
+          "astId": 1547,
+          "type": "t_array:50<t_uint256>",
+          "src": "1096:29:10"
+        },
+        {
+          "contract": "ERC20Mintable",
+          "path": "contracts/token/ERC20/ERC20Mintable.sol",
+          "label": "______gap",
+          "astId": 10840,
+          "type": "t_array:50<t_uint256>",
+          "src": "760:29:129"
+        },
+        {
+          "contract": "PauserRole",
+          "path": "contracts/access/roles/PauserRole.sol",
+          "label": "_pausers",
+          "astId": 1567,
+          "type": "t_struct<Roles.Role>",
+          "src": "286:27:11"
+        },
+        {
+          "contract": "PauserRole",
+          "path": "contracts/access/roles/PauserRole.sol",
+          "label": "______gap",
+          "astId": 1666,
+          "type": "t_array:50<t_uint256>",
+          "src": "1096:29:11"
+        },
+        {
+          "contract": "Pausable",
+          "path": "contracts/lifecycle/Pausable.sol",
+          "label": "_paused",
+          "astId": 5401,
+          "type": "t_bool",
+          "src": "367:20:42"
+        },
+        {
+          "contract": "Pausable",
+          "path": "contracts/lifecycle/Pausable.sol",
+          "label": "______gap",
+          "astId": 5482,
+          "type": "t_array:50<t_uint256>",
+          "src": "1444:29:42"
+        },
+        {
+          "contract": "ERC20Pausable",
+          "path": "contracts/token/ERC20/ERC20Pausable.sol",
+          "label": "______gap",
+          "astId": 10963,
+          "type": "t_array:50<t_uint256>",
+          "src": "1209:29:130"
+        }
+      ],
+      "warnings": {
+        "hasConstructor": false,
+        "hasSelfDestruct": false,
+        "hasDelegateCall": false,
+        "hasInitialValuesInDeclarations": false,
+        "uninitializedBaseContracts": []
+      }
+    }
+  },
+  "solidityLibs": {},
+  "proxies": {},
+  "manifestVersion": "2.2",
+  "frozen": true,
+  "app": {
+    "address": "0x2Ba1a8C7352a5B5Ea3ea3408F89e1bA7920d36CE"
+  },
+  "package": {
+    "address": "0x778dddF23Ec1B5Cb18394c6C110480CaaDB3B0f6"
+  },
+  "provider": {
+    "address": "0xd49C0d11A4a7E49c64d954261570FD2d1589f5d2"
+  },
+  "version": "2.2.2"
+}

.openzeppelin/project.json

@@ -0,0 +1,19 @@
+{
+  "manifestVersion": "2.2",
+  "name": "@openzeppelin/contracts-ethereum-package",
+  "publish": true,
+  "version": "2.2.2",
+  "contracts": {
+    "StandaloneERC20": "StandaloneERC20",
+    "StandaloneERC721": "StandaloneERC721",
+    "TokenVesting": "TokenVesting",
+    "PaymentSplitter": "PaymentSplitter"
+  },
+  "dependencies": {},
+  "compiler": {
+    "manager": "truffle",
+    "compilerSettings": {
+      "optimizer": {}
+    }
+  }
+}

.openzeppelin/rinkeby.json

@@ -0,0 +1,923 @@
+{
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+          "label": "address[]"
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+      },
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+          "src": "589:30:120"
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+          "src": "726:25:120"
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+          "label": "______gap",
+          "astId": 9800,
+          "type": "t_array:50<t_uint256>",
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+          "astId": 13458,
+          "type": "t_array:50<t_uint256>",
+          "src": "1951:29:153"
+        },
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+          "label": "_name",
+          "astId": 10735,
+          "type": "t_string",
+          "src": "397:20:128"
+        },
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+          "label": "_symbol",
+          "astId": 10737,
+          "type": "t_string",
+          "src": "423:22:128"
+        },
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+          "label": "_decimals",
+          "astId": 10739,
+          "type": "t_uint8",
+          "src": "451:23:128"
+        },
+        {
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+          "type": "t_array:50<t_uint256>",
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+          "type": "t_array:50<t_uint256>",
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+        },
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+          "label": "_paused",
+          "astId": 5401,
+          "type": "t_bool",
+          "src": "367:20:42"
+        },
+        {
+          "contract": "Pausable",
+          "path": "contracts/lifecycle/Pausable.sol",
+          "label": "______gap",
+          "astId": 5482,
+          "type": "t_array:50<t_uint256>",
+          "src": "1444:29:42"
+        },
+        {
+          "contract": "ERC20Pausable",
+          "path": "contracts/token/ERC20/ERC20Pausable.sol",
+          "label": "______gap",
+          "astId": 10963,
+          "type": "t_array:50<t_uint256>",
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+          "astId": 13458,
+          "type": "t_array:50<t_uint256>",
+          "src": "1951:29:153"
+        },
+        {
+          "contract": "Ownable",
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+          "label": "_owner",
+          "astId": 9325,
+          "type": "t_address",
+          "src": "317:22:118"
+        },
+        {
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+          "type": "t_array:50<t_uint256>",
+          "src": "2277:29:118"
+        },
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+          "label": "_beneficiary",
+          "astId": 4658,
+          "type": "t_address",
+          "src": "1148:28:36"
+        },
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+        },
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+          "src": "1306:22:36"
+        },
+        {
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+          "label": "_duration",
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+          "type": "t_uint256",
+          "src": "1334:25:36"
+        },
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+          "label": "_revocable",
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+          "type": "t_bool",
+          "src": "1366:23:36"
+        },
+        {
+          "contract": "TokenVesting",
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+          "label": "_released",
+          "astId": 4670,
+          "type": "t_mapping<t_uint256>",
+          "src": "1396:46:36"
+        },
+        {
+          "contract": "TokenVesting",
+          "path": "contracts/drafts/TokenVesting.sol",
+          "label": "_revoked",
+          "astId": 4674,
+          "type": "t_mapping<t_bool>",
+          "src": "1448:42:36"
+        },
+        {
+          "contract": "TokenVesting",
+          "path": "contracts/drafts/TokenVesting.sol",
+          "label": "______gap",
+          "astId": 5016,
+          "type": "t_array:50<t_uint256>",
+          "src": "5852:29:36"
+        }
+      ],
+      "warnings": {
+        "hasConstructor": false,
+        "hasSelfDestruct": false,
+        "hasDelegateCall": false,
+        "hasInitialValuesInDeclarations": false,
+        "uninitializedBaseContracts": [],
+        "storageUncheckedVars": [],
+        "storageDiff": []
+      }
+    },
+    "StandaloneERC721": {
+      "address": "0xfcdA0Ae8c7181521c632550de92B1FB3937D166C",
+      "constructorCode": "608060405234801561001057600080fd5b506135c8806100206000396000f3fe",
+      "bodyBytecodeHash": "b71f19d62583c08240fd85bec42565407f679b1873d7f6e97295a894c7864e2d",
+      "localBytecodeHash": "2e71874460f43d0696496418b1abf57ed58ce1dc524044860260dda9d7de7fab",
+      "deployedBytecodeHash": "2e71874460f43d0696496418b1abf57ed58ce1dc524044860260dda9d7de7fab",
+      "types": {
+        "t_bool": {
+          "id": "t_bool",
+          "kind": "elementary",
+          "label": "bool"
+        },
+        "t_uint256": {
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+          "kind": "elementary",
+          "label": "uint256"
+        },
+        "t_array:50<t_uint256>": {
+          "id": "t_array:50<t_uint256>",
+          "valueType": "t_uint256",
+          "length": "50",
+          "kind": "array",
+          "label": "uint256[50]"
+        },
+        "t_mapping<t_bool>": {
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+          "valueType": "t_bool",
+          "label": "mapping(key => bool)",
+          "kind": "mapping"
+        },
+        "t_address": {
+          "id": "t_address",
+          "kind": "elementary",
+          "label": "address"
+        },
+        "t_mapping<t_address>": {
+          "id": "t_mapping<t_address>",
+          "valueType": "t_address",
+          "label": "mapping(key => address)",
+          "kind": "mapping"
+        },
+        "t_struct<Counters.Counter>": {
+          "id": "t_struct<Counters.Counter>",
+          "kind": "struct",
+          "label": "Counters.Counter",
+          "members": [
+            {
+              "label": "_value",
+              "astId": 3632,
+              "type": "t_uint256",
+              "src": "1021:14:30"
+            }
+          ]
+        },
+        "t_mapping<t_struct<Counters.Counter>>": {
+          "id": "t_mapping<t_struct<Counters.Counter>>",
+          "valueType": "t_struct<Counters.Counter>",
+          "label": "mapping(key => Counters.Counter)",
+          "kind": "mapping"
+        },
+        "t_array:dyn<t_uint256>": {
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+          "valueType": "t_uint256",
+          "length": "dyn",
+          "kind": "array",
+          "label": "uint256[]"
+        },
+        "t_mapping<t_array:dyn<t_uint256>>": {
+          "id": "t_mapping<t_array:dyn<t_uint256>>",
+          "valueType": "t_array:dyn<t_uint256>",
+          "label": "mapping(key => uint256[])",
+          "kind": "mapping"
+        },
+        "t_mapping<t_uint256>": {
+          "id": "t_mapping<t_uint256>",
+          "valueType": "t_uint256",
+          "label": "mapping(key => uint256)",
+          "kind": "mapping"
+        },
+        "t_string": {
+          "id": "t_string",
+          "kind": "elementary",
+          "label": "string"
+        },
+        "t_mapping<t_string>": {
+          "id": "t_mapping<t_string>",
+          "valueType": "t_string",
+          "label": "mapping(key => string)",
+          "kind": "mapping"
+        },
+        "t_struct<Roles.Role>": {
+          "id": "t_struct<Roles.Role>",
+          "kind": "struct",
+          "label": "Roles.Role",
+          "members": [
+            {
+              "label": "bearer",
+              "astId": 1222,
+              "type": "t_mapping<t_bool>",
+              "src": "150:32:8"
+            }
+          ]
+        }
+      },
+      "storage": [
+        {
+          "contract": "Initializable",
+          "path": "@openzeppelin/upgrades/contracts/Initializable.sol",
+          "label": "initialized",
+          "astId": 13400,
+          "type": "t_bool",
+          "src": "757:24:153"
+        },
+        {
+          "contract": "Initializable",
+          "path": "@openzeppelin/upgrades/contracts/Initializable.sol",
+          "label": "initializing",
+          "astId": 13402,
+          "type": "t_bool",
+          "src": "876:25:153"
+        },
+        {
+          "contract": "Initializable",
+          "path": "@openzeppelin/upgrades/contracts/Initializable.sol",
+          "label": "______gap",
+          "astId": 13458,
+          "type": "t_array:50<t_uint256>",
+          "src": "1951:29:153"
+        },
+        {
+          "contract": "ERC165",
+          "path": "contracts/introspection/ERC165.sol",
+          "label": "_supportedInterfaces",
+          "astId": 5191,
+          "type": "t_mapping<t_bool>",
+          "src": "511:52:39"
+        },
+        {
+          "contract": "ERC165",
+          "path": "contracts/introspection/ERC165.sol",
+          "label": "______gap",
+          "astId": 5235,
+          "type": "t_array:50<t_uint256>",
+          "src": "1244:29:39"
+        },
+        {
+          "contract": "ERC721",
+          "path": "contracts/token/ERC721/ERC721.sol",
+          "label": "_tokenOwner",
+          "astId": 11595,
+          "type": "t_mapping<t_address>",
+          "src": "844:48:135"
+        },
+        {
+          "contract": "ERC721",
+          "path": "contracts/token/ERC721/ERC721.sol",
+          "label": "_tokenApprovals",
+          "astId": 11599,
+          "type": "t_mapping<t_address>",
+          "src": "948:52:135"
+        },
+        {
+          "contract": "ERC721",
+          "path": "contracts/token/ERC721/ERC721.sol",
+          "label": "_ownedTokensCount",
+          "astId": 11603,
+          "type": "t_mapping<t_struct<Counters.Counter>>",
+          "src": "1058:63:135"
+        },
+        {
+          "contract": "ERC721",
+          "path": "contracts/token/ERC721/ERC721.sol",
+          "label": "_operatorApprovals",
+          "astId": 11609,
+          "type": "t_mapping<t_bool>",
+          "src": "1176:73:135"
+        },
+        {
+          "contract": "ERC721",
+          "path": "contracts/token/ERC721/ERC721.sol",
+          "label": "______gap",
+          "astId": 12132,
+          "type": "t_array:50<t_uint256>",
+          "src": "11673:29:135"
+        },
+        {
+          "contract": "ERC721Enumerable",
+          "path": "contracts/token/ERC721/ERC721Enumerable.sol",
+          "label": "_ownedTokens",
+          "astId": 12183,
+          "type": "t_mapping<t_array:dyn<t_uint256>>",
+          "src": "460:50:137"
+        },
+        {
+          "contract": "ERC721Enumerable",
+          "path": "contracts/token/ERC721/ERC721Enumerable.sol",
+          "label": "_ownedTokensIndex",
+          "astId": 12187,
+          "type": "t_mapping<t_uint256>",
+          "src": "580:53:137"
+        },
+        {
+          "contract": "ERC721Enumerable",
+          "path": "contracts/token/ERC721/ERC721Enumerable.sol",
+          "label": "_allTokens",
+          "astId": 12190,
+          "type": "t_array:dyn<t_uint256>",
+          "src": "694:28:137"
+        },
+        {
+          "contract": "ERC721Enumerable",
+          "path": "contracts/token/ERC721/ERC721Enumerable.sol",
+          "label": "_allTokensIndex",
+          "astId": 12194,
+          "type": "t_mapping<t_uint256>",
+          "src": "793:51:137"
+        },
+        {
+          "contract": "ERC721Enumerable",
+          "path": "contracts/token/ERC721/ERC721Enumerable.sol",
+          "label": "______gap",
+          "astId": 12523,
+          "type": "t_array:50<t_uint256>",
+          "src": "8816:29:137"
+        },
+        {
+          "contract": "ERC721Metadata",
+          "path": "contracts/token/ERC721/ERC721Metadata.sol",
+          "label": "_name",
+          "astId": 12590,
+          "type": "t_string",
+          "src": "281:20:140"
+        },
+        {
+          "contract": "ERC721Metadata",
+          "path": "contracts/token/ERC721/ERC721Metadata.sol",
+          "label": "_symbol",
+          "astId": 12592,
+          "type": "t_string",
+          "src": "328:22:140"
+        },
+        {
+          "contract": "ERC721Metadata",
+          "path": "contracts/token/ERC721/ERC721Metadata.sol",
+          "label": "_tokenURIs",
+          "astId": 12596,
+          "type": "t_mapping<t_string>",
+          "src": "396:45:140"
+        },
+        {
+          "contract": "ERC721Metadata",
+          "path": "contracts/token/ERC721/ERC721Metadata.sol",
+          "label": "______gap",
+          "astId": 12725,
+          "type": "t_array:50<t_uint256>",
+          "src": "2849:29:140"
+        },
+        {
+          "contract": "MinterRole",
+          "path": "contracts/access/roles/MinterRole.sol",
+          "label": "_minters",
+          "astId": 1448,
+          "type": "t_struct<Roles.Role>",
+          "src": "286:27:10"
+        },
+        {
+          "contract": "MinterRole",
+          "path": "contracts/access/roles/MinterRole.sol",
+          "label": "______gap",
+          "astId": 1547,
+          "type": "t_array:50<t_uint256>",
+          "src": "1096:29:10"
+        },
+        {
+          "contract": "ERC721MetadataMintable",
+          "path": "contracts/token/ERC721/ERC721MetadataMintable.sol",
+          "label": "______gap",
+          "astId": 12795,
+          "type": "t_array:50<t_uint256>",
+          "src": "1055:29:141"
+        },
+        {
+          "contract": "PauserRole",
+          "path": "contracts/access/roles/PauserRole.sol",
+          "label": "_pausers",
+          "astId": 1567,
+          "type": "t_struct<Roles.Role>",
+          "src": "286:27:11"
+        },
+        {
+          "contract": "PauserRole",
+          "path": "contracts/access/roles/PauserRole.sol",
+          "label": "______gap",
+          "astId": 1666,
+          "type": "t_array:50<t_uint256>",
+          "src": "1096:29:11"
+        },
+        {
+          "contract": "Pausable",
+          "path": "contracts/lifecycle/Pausable.sol",
+          "label": "_paused",
+          "astId": 5401,
+          "type": "t_bool",
+          "src": "367:20:42"
+        },
+        {
+          "contract": "Pausable",
+          "path": "contracts/lifecycle/Pausable.sol",
+          "label": "______gap",
+          "astId": 5482,
+          "type": "t_array:50<t_uint256>",
+          "src": "1444:29:42"
+        },
+        {
+          "contract": "ERC721Pausable",
+          "path": "contracts/token/ERC721/ERC721Pausable.sol",
+          "label": "______gap",
+          "astId": 12940,
+          "type": "t_array:50<t_uint256>",
+          "src": "865:29:143"
+        }
+      ],
+      "warnings": {
+        "hasConstructor": false,
+        "hasSelfDestruct": false,
+        "hasDelegateCall": false,
+        "hasInitialValuesInDeclarations": false,
+        "uninitializedBaseContracts": [],
+        "storageUncheckedVars": [
+          {
+            "contract": "ERC721",
+            "path": "contracts/token/ERC721/ERC721.sol",
+            "label": "_ownedTokensCount",
+            "astId": 11603,
+            "type": "t_mapping<t_struct<Counters.Counter>>",
+            "src": "1058:63:135"
+          },
+          {
+            "contract": "MinterRole",
+            "path": "contracts/access/roles/MinterRole.sol",
+            "label": "_minters",
+            "astId": 1448,
+            "type": "t_struct<Roles.Role>",
+            "src": "286:27:10"
+          },
+          {
+            "contract": "PauserRole",
+            "path": "contracts/access/roles/PauserRole.sol",
+            "label": "_pausers",
+            "astId": 1567,
+            "type": "t_struct<Roles.Role>",
+            "src": "286:27:11"
+          }
+        ],
+        "storageDiff": []
+      }
+    }
+  },
+  "solidityLibs": {},
+  "proxies": {},
+  "manifestVersion": "2.2",
+  "frozen": true,
+  "app": {
+    "address": "0x291439E6444dAEc9e47Ae359Aa79FD1811A42679"
+  },
+  "package": {
+    "address": "0xa44bb80b290dE8a465d17B14269dF53CF0B9Bf4f"
+  },
+  "provider": {
+    "address": "0x3629bdF19982A06a7a2Fdfac75aC2dA7F5BC3359"
+  },
+  "version": "2.2.2"
+}

.openzeppelin/ropsten.json

@@ -0,0 +1,923 @@
+{
+  "contracts": {
+    "StandaloneERC721": {
+      "address": "0x55C0f7e0B33d414B5541147CFe04E4F6d0dF3616",
+      "constructorCode": "608060405234801561001057600080fd5b506135c8806100206000396000f3fe",
+      "bodyBytecodeHash": "b71f19d62583c08240fd85bec42565407f679b1873d7f6e97295a894c7864e2d",
+      "localBytecodeHash": "2e71874460f43d0696496418b1abf57ed58ce1dc524044860260dda9d7de7fab",
+      "deployedBytecodeHash": "2e71874460f43d0696496418b1abf57ed58ce1dc524044860260dda9d7de7fab",
+      "types": {
+        "t_bool": {
+          "id": "t_bool",
+          "kind": "elementary",
+          "label": "bool"
+        },
+        "t_uint256": {
+          "id": "t_uint256",
+          "kind": "elementary",
+          "label": "uint256"
+        },
+        "t_array:50<t_uint256>": {
+          "id": "t_array:50<t_uint256>",
+          "valueType": "t_uint256",
+          "length": "50",
+          "kind": "array",
+          "label": "uint256[50]"
+        },
+        "t_mapping<t_bool>": {
+          "id": "t_mapping<t_bool>",
+          "valueType": "t_bool",
+          "label": "mapping(key => bool)",
+          "kind": "mapping"
+        },
+        "t_address": {
+          "id": "t_address",
+          "kind": "elementary",
+          "label": "address"
+        },
+        "t_mapping<t_address>": {
+          "id": "t_mapping<t_address>",
+          "valueType": "t_address",
+          "label": "mapping(key => address)",
+          "kind": "mapping"
+        },
+        "t_struct<Counters.Counter>": {
+          "id": "t_struct<Counters.Counter>",
+          "kind": "struct",
+          "label": "Counters.Counter",
+          "members": [
+            {
+              "label": "_value",
+              "astId": 3632,
+              "type": "t_uint256",
+              "src": "1021:14:30"
+            }
+          ]
+        },
+        "t_mapping<t_struct<Counters.Counter>>": {
+          "id": "t_mapping<t_struct<Counters.Counter>>",
+          "valueType": "t_struct<Counters.Counter>",
+          "label": "mapping(key => Counters.Counter)",
+          "kind": "mapping"
+        },
+        "t_array:dyn<t_uint256>": {
+          "id": "t_array:dyn<t_uint256>",
+          "valueType": "t_uint256",
+          "length": "dyn",
+          "kind": "array",
+          "label": "uint256[]"
+        },
+        "t_mapping<t_array:dyn<t_uint256>>": {
+          "id": "t_mapping<t_array:dyn<t_uint256>>",
+          "valueType": "t_array:dyn<t_uint256>",
+          "label": "mapping(key => uint256[])",
+          "kind": "mapping"
+        },
+        "t_mapping<t_uint256>": {
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+          "valueType": "t_uint256",
+          "label": "mapping(key => uint256)",
+          "kind": "mapping"
+        },
+        "t_string": {
+          "id": "t_string",
+          "kind": "elementary",
+          "label": "string"
+        },
+        "t_mapping<t_string>": {
+          "id": "t_mapping<t_string>",
+          "valueType": "t_string",
+          "label": "mapping(key => string)",
+          "kind": "mapping"
+        },
+        "t_struct<Roles.Role>": {
+          "id": "t_struct<Roles.Role>",
+          "kind": "struct",
+          "label": "Roles.Role",
+          "members": [
+            {
+              "label": "bearer",
+              "astId": 1222,
+              "type": "t_mapping<t_bool>",
+              "src": "150:32:8"
+            }
+          ]
+        }
+      },
+      "storage": [
+        {
+          "contract": "Initializable",
+          "path": "@openzeppelin/upgrades/contracts/Initializable.sol",
+          "label": "initialized",
+          "astId": 13400,
+          "type": "t_bool",
+          "src": "757:24:153"
+        },
+        {
+          "contract": "Initializable",
+          "path": "@openzeppelin/upgrades/contracts/Initializable.sol",
+          "label": "initializing",
+          "astId": 13402,
+          "type": "t_bool",
+          "src": "876:25:153"
+        },
+        {
+          "contract": "Initializable",
+          "path": "@openzeppelin/upgrades/contracts/Initializable.sol",
+          "label": "______gap",
+          "astId": 13458,
+          "type": "t_array:50<t_uint256>",
+          "src": "1951:29:153"
+        },
+        {
+          "contract": "ERC165",
+          "path": "contracts/introspection/ERC165.sol",
+          "label": "_supportedInterfaces",
+          "astId": 5191,
+          "type": "t_mapping<t_bool>",
+          "src": "511:52:39"
+        },
+        {
+          "contract": "ERC165",
+          "path": "contracts/introspection/ERC165.sol",
+          "label": "______gap",
+          "astId": 5235,
+          "type": "t_array:50<t_uint256>",
+          "src": "1244:29:39"
+        },
+        {
+          "contract": "ERC721",
+          "path": "contracts/token/ERC721/ERC721.sol",
+          "label": "_tokenOwner",
+          "astId": 11595,
+          "type": "t_mapping<t_address>",
+          "src": "844:48:135"
+        },
+        {
+          "contract": "ERC721",
+          "path": "contracts/token/ERC721/ERC721.sol",
+          "label": "_tokenApprovals",
+          "astId": 11599,
+          "type": "t_mapping<t_address>",
+          "src": "948:52:135"
+        },
+        {
+          "contract": "ERC721",
+          "path": "contracts/token/ERC721/ERC721.sol",
+          "label": "_ownedTokensCount",
+          "astId": 11603,
+          "type": "t_mapping<t_struct<Counters.Counter>>",
+          "src": "1058:63:135"
+        },
+        {
+          "contract": "ERC721",
+          "path": "contracts/token/ERC721/ERC721.sol",
+          "label": "_operatorApprovals",
+          "astId": 11609,
+          "type": "t_mapping<t_bool>",
+          "src": "1176:73:135"
+        },
+        {
+          "contract": "ERC721",
+          "path": "contracts/token/ERC721/ERC721.sol",
+          "label": "______gap",
+          "astId": 12132,
+          "type": "t_array:50<t_uint256>",
+          "src": "11673:29:135"
+        },
+        {
+          "contract": "ERC721Enumerable",
+          "path": "contracts/token/ERC721/ERC721Enumerable.sol",
+          "label": "_ownedTokens",
+          "astId": 12183,
+          "type": "t_mapping<t_array:dyn<t_uint256>>",
+          "src": "460:50:137"
+        },
+        {
+          "contract": "ERC721Enumerable",
+          "path": "contracts/token/ERC721/ERC721Enumerable.sol",
+          "label": "_ownedTokensIndex",
+          "astId": 12187,
+          "type": "t_mapping<t_uint256>",
+          "src": "580:53:137"
+        },
+        {
+          "contract": "ERC721Enumerable",
+          "path": "contracts/token/ERC721/ERC721Enumerable.sol",
+          "label": "_allTokens",
+          "astId": 12190,
+          "type": "t_array:dyn<t_uint256>",
+          "src": "694:28:137"
+        },
+        {
+          "contract": "ERC721Enumerable",
+          "path": "contracts/token/ERC721/ERC721Enumerable.sol",
+          "label": "_allTokensIndex",
+          "astId": 12194,
+          "type": "t_mapping<t_uint256>",
+          "src": "793:51:137"
+        },
+        {
+          "contract": "ERC721Enumerable",
+          "path": "contracts/token/ERC721/ERC721Enumerable.sol",
+          "label": "______gap",
+          "astId": 12523,
+          "type": "t_array:50<t_uint256>",
+          "src": "8816:29:137"
+        },
+        {
+          "contract": "ERC721Metadata",
+          "path": "contracts/token/ERC721/ERC721Metadata.sol",
+          "label": "_name",
+          "astId": 12590,
+          "type": "t_string",
+          "src": "281:20:140"
+        },
+        {
+          "contract": "ERC721Metadata",
+          "path": "contracts/token/ERC721/ERC721Metadata.sol",
+          "label": "_symbol",
+          "astId": 12592,
+          "type": "t_string",
+          "src": "328:22:140"
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+        "hasSelfDestruct": false,
+        "hasDelegateCall": false,
+        "hasInitialValuesInDeclarations": false,
+        "uninitializedBaseContracts": [],
+        "storageUncheckedVars": [],
+        "storageDiff": []
+      }
+    }
+  },
+  "solidityLibs": {},
+  "proxies": {},
+  "manifestVersion": "2.2",
+  "frozen": true,
+  "app": {
+    "address": "0x27a09abCA2c4d9F914dbC7BeA164b0e6b74Ce7a9"
+  },
+  "package": {
+    "address": "0x2a9e7B63514438906A83a1e320dBBD814D417002"
+  },
+  "provider": {
+    "address": "0xdE16eC017431009ebE329E54D399CB4d5e161B8d"
+  },
+  "version": "2.2.2"
+}

.solhint.json

@@ -0,0 +1,11 @@
+{
+  "extends": "default",
+  "rules": {
+    "indent": ["error", 4],
+
+    "bracket-align": false,
+    "compiler-fixed": false,
+    "no-simple-event-func-name": false,
+    "two-lines-top-level-separator": false
+  }
+}

.soliumignore

@@ -1 +0,0 @@
-node_modules

.soliumrc.json

@@ -1,21 +0,0 @@
-{
-  "extends": "solium:all",
-  "plugins": ["security"],
-  "rules": {
-    "blank-lines": "off",
-    "error-reason": "off",
-    "indentation": ["error", 2],
-    "lbrace": "off",
-    "linebreak-style": ["error", "unix"],
-    "max-len": ["error", 79],
-    "no-constant": ["error"],
-    "no-empty-blocks": "off",
-    "quotes": ["error", "double"],
-    "uppercase": "off",
-    "visibility-first": "error",
-
-    "security/enforce-explicit-visibility": ["error"],
-    "security/no-block-members": ["warning"],
-    "security/no-inline-assembly": ["warning"]
-  }
-}

.travis.yml

@@ -1,56 +0,0 @@
-dist: trusty
-sudo: false
-group: beta
-language: node_js
-node_js:
-  - "8"
-
-cache:
-  directories:
-    - node_modules
-
-jobs:
-  # XXX fast_finish doesn't work with stages yet. See
-  # https://github.com/travis-ci/travis-ci/issues/8425
-  # --elopio - 20180531
-  fast_finish: true
-  allow_failures:
-    - env: SOLIDITY_COVERAGE=true
-    - env: SOLC_NIGHTLY=true
-  include:
-    # Run the unit test suite three times in parallel.
-    # The first one gets results faster and is the only one required to pass.
-    # The second one generates the coverage report.
-    # The third one is to keep us informed about possible issues with the
-    # upcoming solidity release.
-    - stage: tests
-      name: "unit tests"
-      script: npm run test
-    - stage: tests
-      name: "unit tests with coverage"
-      script: npm run test
-      env: SOLIDITY_COVERAGE=true
-    - stage: tests
-      name: "unit tests with solc nightly"
-      script: npm run test
-      env: SOLC_NIGHTLY=true
-    # solidity and javascript style tests.
-    - stage: tests
-      name: "static tests"
-      script: npm run lint
-    - stage: update docs
-      if: tag =~ ^v[0-9]+\.[0-9]+\.[0-9]+$
-      addons:
-        apt:
-          packages:
-            - curl
-      script:
-        - ./scripts/ci/trigger_docs_update "${TRAVIS_TAG}"
-
-notifications:
-  slack:
-    rooms:
-      - secure: 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
-    on_success: change
-    on_failure: always
-    on_pull_requests: false

CHANGELOG.md

@@ -0,0 +1,70 @@
+# Changelog
+
+## 2.2.2 (2019-08-12)
+
+### New features:
+ * Facilities to make metatransaction-enabled contracts through the Gas Station Network. Backported from [#1844](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/1844).
+
+## 2.2.1 (2019-07-22)
+
+### Changes:
+* Renamed package to `@openzeppelin/contracts-ethereum-package`. ([#54](https://github.com/OpenZeppelin/openzeppelin-contracts-ethereum-package/pull/54))
+
+## 2.2.0 (2019-03-14)
+
+### New features:
+ * `ERC20Snapshot`: create snapshots on demand of the token balances and total supply, to later retrieve and e.g. calculate dividends at a past time. ([#1617](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1617))
+ * `SafeERC20`: `ERC20` contracts with no return value (i.e. that revert on failure) are now supported. ([#1655](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/))
+ * `ERC20`: added internal `_approve(address owner, address spender, uint256 value)`, allowing derived contracts to set the allowance of arbitrary accounts. ([#1609](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1609))
+ * `ERC20Metadata`: added internal `_setTokenURI(string memory tokenURI)`. ([#1618](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1618))
+ * `TimedCrowdsale`: added internal `_extendTime(uint256 newClosingTime)` as well as `TimedCrowdsaleExtended(uint256 prevClosingTime, uint256 newClosingTime)` event allowing to extend the crowdsale, as long as it hasn't already closed.
+
+### Improvements:
+ * Upgraded the minimum compiler version to v0.5.2: this removes many Solidity warnings that were false positives. ([#1606](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1606))
+ * `ECDSA`: `recover` no longer accepts malleable signatures (those using upper-range values for `s`, or 0/1 for `v`). ([#1622](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1622))
+ * `ERC721`'s transfers are now more gas efficient due to removal of unnecessary `SafeMath` calls. ([#1610](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1610))
+ * `Counter`'s API has been improved, and is now used by `ERC721` (though it is still in `drafts`). ([#1610](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1610))
+ * Fixed variable shadowing issues. ([#1606](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1606))
+
+### Bugfixes:
+ * (minor) `SafeERC20`: `safeApprove` wasn't properly checking for a zero allowance when attempting to set a non-zero allowance. ([#1647](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1647))
+
+### Breaking changes:
+ * `TokenMetadata` (in drafts) has been renamed to `ERC20Metadata`. ([#1618](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1618))
+
+## 2.1.3 (2019-02-26)
+ * Backported `SafeERC20.safeApprove` bugfix. ([#1647](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1647))
+
+## 2.1.2 (2019-01-17)
+ * Removed most of the test suite from the npm package, except `PublicRole.behavior.js`, which may be useful to users testing their own `Roles`.
+
+## 2.1.1 (2019-01-04)
+ * Version bump to avoid conflict in the npm registry.
+
+## 2.1.0 (2019-01-04)
+
+### New features:
+ * Now targeting the 0.5.x line of Solidity compilers. For 0.4.24 support, use version 2.0 of OpenZeppelin.
+ * `WhitelistCrowdsale`: a crowdsale where only whitelisted accounts (`WhitelistedRole`) can purchase tokens. Adding or removing accounts from the whitelist is done by whitelist admins (`WhitelistAdminRole`). Similar to the pre-2.0 `WhitelistedCrowdsale`. ([#1525](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1525), [#1589](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1589))
+ * `RefundablePostDeliveryCrowdsale`: replacement for `RefundableCrowdsale` (deprecated, see below) where tokens are only granted once the crowdsale ends (if it meets its goal). ([#1543](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1543))
+ * `PausableCrowdsale`: allows for pausers (`PauserRole`) to pause token purchases. Other crowdsale operations (e.g. withdrawals and refunds, if applicable) are not affected. ([#832](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/832))
+ * `ERC20`: `transferFrom` and `_burnFrom ` now emit `Approval` events, to represent the token's state comprehensively through events. ([#1524](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1524))
+ * `ERC721`: added `_burn(uint256 tokenId)`, replacing the similar deprecated function (see below). ([#1550](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1550))
+ * `ERC721`: added `_tokensOfOwner(address owner)`, allowing to internally retrieve the array of an account's owned tokens. ([#1522](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1522))
+ * Crowdsales: all constructors are now `public`, meaning it is not necessary to extend these contracts in order to deploy them. The exception is `FinalizableCrowdsale`, since it is meaningless unless extended. ([#1564](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1564))
+ * `SignedSafeMath`: added overflow-safe operations for signed integers (`int256`). ([#1559](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1559), [#1588](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1588))
+
+### Improvements:
+ * The compiler version required by `Array` was behind the rest of the libray so it was updated to `v0.4.24`. ([#1553](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1553))
+ * Now conforming to a 4-space indentation code style. ([1508](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1508))
+ * `ERC20`: more gas efficient due to removed redundant `require`s. ([#1409](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1409))
+ * `ERC721`: fixed a bug that prevented internal data structures from being properly cleaned, missing potential gas refunds. ([#1539](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1539) and [#1549](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1549))
+ * `ERC721`: general gas savings on `transferFrom`, `_mint` and `_burn`, due to redudant `require`s and `SSTORE`s. ([#1549](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1549))
+
+### Bugfixes:
+
+### Breaking changes:
+
+### Deprecations:
+ * `ERC721._burn(address owner, uint256 tokenId)`: due to the `owner` parameter being unnecessary. ([#1550](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1550))
+ * `RefundableCrowdsale`: due to trading abuse potential on crowdsales that miss their goal. ([#1543](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1543))

README.md

@@ -1,42 +1,100 @@
-# <img src="logo.png" alt="OpenZeppelin" width="400px">
+# <img src="logo.png" alt="OpenZeppelin" height="40px">
 
-[![NPM Package](https://img.shields.io/npm/v/openzeppelin-solidity.svg?style=flat-square)](https://www.npmjs.org/package/openzeppelin-solidity)
-[![Build Status](https://img.shields.io/travis/OpenZeppelin/openzeppelin-solidity.svg?branch=master&style=flat-square)](https://travis-ci.org/OpenZeppelin/openzeppelin-solidity)
-[![Coverage Status](https://img.shields.io/coveralls/github/OpenZeppelin/openzeppelin-solidity/master.svg?style=flat-square)](https://coveralls.io/github/OpenZeppelin/openzeppelin-solidity?branch=master)
+## OpenZeppelin Contracts Ethereum Package
 
-**OpenZeppelin is a library for secure smart contract development.** It provides implementations of standards like ERC20 and ERC721 which you can deploy as-is or extend to suit your needs, as well as Solidity components to build custom contracts and more complex decentralized systems.
+[![NPM Package](https://img.shields.io/npm/v/@openzeppelin/contracts-ethereum-package.svg)](https://www.npmjs.org/package/@openzeppelin/contracts-ethereum-package)
+[![Build Status](https://circleci.com/gh/OpenZeppelin/openzeppelin-contracts-ethereum-package.svg?style=shield)](https://circleci.com/gh/OpenZeppelin/openzeppelin-contracts-ethereum-package)
+
+**OpenZeppelin Contracts is a library for secure smart contract development.** It provides implementations of standards like ERC20 and ERC721 which you can deploy as-is or extend to suit your needs, as well as Solidity components to build custom contracts and more complex decentralized systems.
+
+This fork of OpenZeppelin is set up as a **reusable Ethereum Package**. It is deployed to the kovan, rinkeby, and ropsten test networks, as well as to the main Ethereum network. You can reuse any of the pre-deployed on-chain contracts by simply linking to them using the [OpenZeppelin SDK](https://github.com/openzeppelin/openzeppelin-sdk), or reuse their Solidity source code as with the [vanilla version of OpenZeppelin Contracts](https://github.com/OpenZeppelin/openzeppelin-contracts).
+
+## Differences with openzeppelin-contracts
+
+This package contains the same contracts as the vanilla [openzeppelin-contracts](https://github.com/openZeppelin/openzeppelin-contracts). The main difference is that _all contracts in this package are potentially upgradeable_: you will notice that no contracts have constructors defined, but use [initializer functions](https://docs.zeppelinos.org/docs/writing_contracts.html#initializers) instead. Also, this package is set up as an Ethereum package, and provides a small set of pre-deployed logic contracts that can be used directly via the OpenZeppelin SDK, without needing to deploy them again.
+
+All in all, **you should use this package instead of openzeppelin-solidity if you are managing your project via the OpenZeppelin CLI**.
 
 ## Install
 
 ```
-npm install openzeppelin-solidity
+npm install @openzeppelin/contracts-ethereum-package
 ```
 
-## Usage
+## Deployed logic contracts
 
-To write your custom contracts, import ours and extend them through inheritance.
+- [StandaloneERC20](contracts/token/ERC20/StandaloneERC20.sol): ERC20 token implementation, optionally mintable and pausable.
+- [StandaloneERC721](contracts/token/ERC721/StandaloneERC721.sol): ERC721 non-fungible token implementation with metadata and enumerable extensions, optionally mintable and pausable.
+- [TokenVesting](contracts/drafts/TokenVesting.sol): tToken holder contract that can release its token balance gradually like a typical vesting scheme, with a cliff and vesting period, optionally revocable.
+- [PaymentSplitter](contracts/payment/PaymentSplitter.sol): Splits payments among a group of addresses proportionately to some number of shares they own.
+
+## Using via the OpenZeppelin CLI
+
+You can easily create upgradeable instances of any of the logic contracts listed above using the OpenZeppelin CLI. This will rely on the pre-deployed instances in mainnet, kovan, ropsten, or rinkeby, greatly reducing your gas deployment costs. To do this, just [create a new OpenZeppelin SDK project](https://docs.zeppelinos.org/docs/deploying.html) and [link to this package](https://docs.zeppelinos.org/docs/linking.html).
+
+```bash
+$ npm install -g @openzeppelin/cli
+$ openzeppelin init
+$ openzeppelin link @openzeppelin/contracts-ethereum-package
+> Installing...
+$ openzeppelin create @openzeppelin/contracts-ethereum-package/StandaloneERC20
+> Creating...
+```
+
+To create an instance of a contract, use the `openzeppelin create` command. As an example, you can run the following to create an upgradeable ERC20 named MyToken, with symbol TKN and 8 decimals, and an initial supply of 100 tokens assigned to the address HOLDER, with a MINTER and a PAUSER. Remember to replace $HOLDER, $MINTER, and $PAUSER with actual addresses when you run this command; you can specify more than one (or none at all) minters and pausers.
+
+```
+$ openzeppelin create
+? Pick a contract to instantiate: @openzeppelin/contracts-ethereum-package/StandaloneERC20
+? Pick a network: development
+✓ Deploying @openzeppelin/contracts-ethereum-package dependency to network
+? Do you want to call a function on the instance after creating it?: Yes
+? Select which function: * initialize(name: string, symbol: string, decimals: uint8, initialSupply: uint256, initialHolder: address, minters: address[], pausers: address[])
+? name (string): MyToken
+? symbol (string): MYT
+? decimals (uint8): 18
+? initialSupply (uint256): 100e18
+? initialHolder (address): 0x90f8bf6a479f320ead074411a4b0e7944ea8c9c1
+? minters (address[]):
+? pausers (address[]):
+✓ Setting everything up to create contract instances
+✓ Instance created at 0x2612Af3A521c2df9EAF28422Ca335b04AdF3ac66
+```
+
+OpenZeppelin will create an upgradeable ERC20 instance and keep track of its address in the `.openzeppelin/rinkeby.json` file. Should you update your version of the openzeppelin contracts ethereum package later down the road, you can simply run `openzeppelin update` to upgrade all your ERC20 instances to the latest version.
+
+You can also deploy a ERC721 token by choosing the `StandaloneERC721` contract when running `openzeppelin create`. Refer to the `initialize` function of each of the predeployed logic contracts to see which parameters are required for initialization.
+
+## Extending contracts
+
+If you prefer to write your custom contracts, import the ones from this package and extend them through inheritance. Note that **you must use this package and not `@openzeppelin/contracts` if you are [writing upgradeable contracts](https://docs.zeppelinos.org/docs/writing_contracts.html)**.
 
 ```solidity
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.0;
 
-import 'openzeppelin-solidity/contracts/token/ERC721/ERC721Full.sol';
-import 'openzeppelin-solidity/contracts/token/ERC721/ERC721Mintable.sol';
+import '@openzeppelin/upgrades/contracts/Initializable.sol';
+import '@openzeppelin/contracts-ethereum-package/contracts/token/ERC721/ERC721Full.sol';
+import '@openzeppelin/contracts-ethereum-package/contracts/token/ERC721/ERC721Mintable.sol';
 
-contract MyNFT is ERC721Full, ERC721Mintable {
-  constructor() ERC721Full("MyNFT", "MNFT") public {
+contract MyNFT is Initializable, ERC721Full, ERC721Mintable {
+  function initialize() public initializer {
+    ERC721.initialize();
+    ERC721Enumerable.initialize();
+    ERC721Metadata.initialize("MyNFT", "MNFT");
+    ERC721Mintable.initialize(msg.sender);
   }
 }
 ```
 
-> You need an ethereum development framework for the above import statements to work! Check out these guides for [Truffle] or [Embark].
-
-On our site you will find a few [guides] to learn about the diferent parts of OpenZeppelin, as well as [documentation for the API][API docs]. Keep in mind that the API docs are work in progress, and don’t hesitate to ask questions in [our Slack][Slack].
+On our site you will find a few [guides] to learn about the different parts of OpenZeppelin, as well as [documentation for the API][API docs]. Keep in mind that the API docs are work in progress, and don’t hesitate to ask questions in [our forum][forum].
 
 ## Security
 
-OpenZeppelin the project is maintained by [Zeppelin] the company, and developed following our high standards for code quality and security. OpenZeppelin is meant to provide tested and community-audited code, but please use common sense when doing anything that deals with real money! We take no responsibility for your implementation decisions and any security problems you might experience.
+OpenZeppelin Contracts is maintained by [OpenZeppelin](https://openzeppelin.com) the company, and developed following our high standards for code quality and security. OpenZeppelin Contracts is meant to provide tested and community-audited code, but please use common sense when doing anything that deals with real money! We take no responsibility for your implementation decisions and any security problems you might experience.
 
-The core development principles and strategies that OpenZeppelin is based on include: security in depth, simple and modular code, clarity-driven naming conventions, comprehensive unit testing, pre-and-post-condition sanity checks, code consistency, and regular audits.
+The core development principles and strategies that OpenZeppelin Contracts is based on include: security in depth, simple and modular code, clarity-driven naming conventions, comprehensive unit testing, pre-and-post-condition sanity checks, code consistency, and regular audits.
+
+The latest audit was done on October 2018 on version 2.0.0.
 
 Please report any security issues you find to security@openzeppelin.org.
 
@@ -48,11 +106,7 @@ OpenZeppelin exists thanks to its contributors. There are many ways you can part
 
 OpenZeppelin is released under the [MIT License](LICENSE).
 
-
-[API docs]: https://openzeppelin.org/api/docs/token_ERC721_ERC721BasicToken.html
-[guides]: https://openzeppelin.org/api/docs/get-started.html
-[Slack]: https://slack.openzeppelin.org
-[Zeppelin]: https://zeppelin.solutions
+[API docs]: https://docs.openzeppelin.org/v2.3.0/api/token/erc20
+[guides]: https://docs.openzeppelin.org/v2.3.0/get-started
+[forum]: https://forum.zeppelin.solutions
 [contribution guide]: CONTRIBUTING.md
-[Truffle]: https://truffleframework.com/docs/truffle/quickstart
-[Embark]: https://embark.status.im/docs/quick_start.html

RELEASING.md

@@ -34,7 +34,7 @@ git push upstream vX.Y.Z-rc.R
 
 Draft the release notes in our [GitHub releases](https://github.com/OpenZeppelin/openzeppelin-solidity/releases). Make sure to mark it as a pre-release! Try to be consistent with our previous release notes in the title and format of the text. Release candidates don't need a detailed changelog, but make sure to include a link to GitHub's compare page.
 
-Once the CI run for the new tag is green, publish on npm under the `next` tag.
+Once the CI run for the new tag is green, publish on npm under the `next` tag. You should see the contracts compile automatically.
 
 ```
 npm publish --tag next
@@ -51,18 +51,21 @@ git checkout release-vX.Y.Z
 git pull upstream
 ```
 
+Before starting the release process, make one final commit to CHANGELOG.md, including the date of the release.
+
 Change the version string in `package.json`, `package-lock.json` and `ethpm.json` removing the "-rc.R" suffix. Commit these changes and tag the commit as `vX.Y.Z`.
 
 ```
 git add package.json package-lock.json ethpm.json
 git commit -m "Release vX.Y.Z"
 git tag -a vX.Y.Z
+git push upstream release-vX.Y.Z
 git push upstream vX.Y.Z
 ```
 
 Draft the release notes in GitHub releases. Try to be consistent with our previous release notes in the title and format of the text. Make sure to include a detailed changelog.
 
-Once the CI run for the new tag is green, publish on npm.
+Once the CI run for the new tag is green, publish on npm. You should see the contracts compile automatically.
 
 ```
 npm publish

contracts/GSN/Context.sol

@@ -0,0 +1,27 @@
+pragma solidity ^0.5.0;
+
+/*
+ * @dev Provides information about the current execution context, including the
+ * sender of the transaction and its data. While these are generally available
+ * via msg.sender and msg.data, they not should not be accessed in such a direct
+ * manner, since when dealing with GSN meta-transactions the account sending and
+ * paying for execution may not be the actual sender (as far as an application
+ * is concerned).
+ *
+ * This contract is only required for intermediate, library-like contracts.
+ */
+contract Context {
+    // Empty internal constructor, to prevent people from mistakenly deploying
+    // an instance of this contract, with should be used via inheritance.
+    constructor () internal { }
+    // solhint-disable-previous-line no-empty-blocks
+
+    function _msgSender() internal view returns (address) {
+        return msg.sender;
+    }
+
+    function _msgData() internal view returns (bytes memory) {
+        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
+        return msg.data;
+    }
+}

contracts/GSN/GSNContext.sol

@@ -0,0 +1,103 @@
+pragma solidity ^0.5.0;
+
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
+import "./Context.sol";
+
+/*
+ * @dev Enables GSN support on `Context` contracts by recognizing calls from
+ * RelayHub and extracting the actual sender and call data from the received
+ * calldata.
+ *
+ * > This contract does not perform all required tasks to implement a GSN
+ * recipient contract: end users should use `GSNRecipient` instead.
+ */
+contract GSNContext is Initializable, Context {
+    // We use a random storage slot to allow proxy contracts to enable GSN support in an upgrade without changing their
+    // storage layout. This value is calculated as: keccak256('gsn.relayhub.address'), minus 1.
+    bytes32 private constant RELAY_HUB_ADDRESS_STORAGE_SLOT = 0x06b7792c761dcc05af1761f0315ce8b01ac39c16cc934eb0b2f7a8e71414f262;
+
+    event RelayHubChanged(address indexed oldRelayHub, address indexed newRelayHub);
+
+    function initialize() public initializer {
+        _upgradeRelayHub(0xD216153c06E857cD7f72665E0aF1d7D82172F494);
+    }
+
+    function _getRelayHub() internal view returns (address relayHub) {
+        bytes32 slot = RELAY_HUB_ADDRESS_STORAGE_SLOT;
+        // solhint-disable-next-line no-inline-assembly
+        assembly {
+            relayHub := sload(slot)
+        }
+    }
+
+    function _upgradeRelayHub(address newRelayHub) internal {
+        address currentRelayHub = _getRelayHub();
+        require(newRelayHub != address(0), "GSNContext: new RelayHub is the zero address");
+        require(newRelayHub != currentRelayHub, "GSNContext: new RelayHub is the current one");
+
+        emit RelayHubChanged(currentRelayHub, newRelayHub);
+
+        bytes32 slot = RELAY_HUB_ADDRESS_STORAGE_SLOT;
+        // solhint-disable-next-line no-inline-assembly
+        assembly {
+            sstore(slot, newRelayHub)
+        }
+    }
+
+    // Overrides for Context's functions: when called from RelayHub, sender and
+    // data require some pre-processing: the actual sender is stored at the end
+    // of the call data, which in turns means it needs to be removed from it
+    // when handling said data.
+
+    function _msgSender() internal view returns (address) {
+        if (msg.sender != _getRelayHub()) {
+            return msg.sender;
+        } else {
+            return _getRelayedCallSender();
+        }
+    }
+
+    function _msgData() internal view returns (bytes memory) {
+        if (msg.sender != _getRelayHub()) {
+            return msg.data;
+        } else {
+            return _getRelayedCallData();
+        }
+    }
+
+    function _getRelayedCallSender() private pure returns (address result) {
+        // We need to read 20 bytes (an address) located at array index msg.data.length - 20. In memory, the array
+        // is prefixed with a 32-byte length value, so we first add 32 to get the memory read index. However, doing
+        // so would leave the address in the upper 20 bytes of the 32-byte word, which is inconvenient and would
+        // require bit shifting. We therefore subtract 12 from the read index so the address lands on the lower 20
+        // bytes. This can always be done due to the 32-byte prefix.
+
+        // The final memory read index is msg.data.length - 20 + 32 - 12 = msg.data.length. Using inline assembly is the
+        // easiest/most-efficient way to perform this operation.
+
+        // These fields are not accessible from assembly
+        bytes memory array = msg.data;
+        uint256 index = msg.data.length;
+
+        // solhint-disable-next-line no-inline-assembly
+        assembly {
+            // Load the 32 bytes word from memory with the address on the lower 20 bytes, and mask those.
+            result := and(mload(add(array, index)), 0xffffffffffffffffffffffffffffffffffffffff)
+        }
+        return result;
+    }
+
+    function _getRelayedCallData() private pure returns (bytes memory) {
+        // RelayHub appends the sender address at the end of the calldata, so in order to retrieve the actual msg.data,
+        // we must strip the last 20 bytes (length of an address type) from it.
+
+        uint256 actualDataLength = msg.data.length - 20;
+        bytes memory actualData = new bytes(actualDataLength);
+
+        for (uint256 i = 0; i < actualDataLength; ++i) {
+            actualData[i] = msg.data[i];
+        }
+
+        return actualData;
+    }
+}

contracts/GSN/GSNRecipient.sol

@@ -0,0 +1,33 @@
+pragma solidity ^0.5.0;
+
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
+import "./IRelayRecipient.sol";
+import "./GSNContext.sol";
+import "./bouncers/GSNBouncerBase.sol";
+import "./IRelayHub.sol";
+
+/*
+ * @dev Base GSN recipient contract, adding the recipient interface and enabling
+ * GSN support. Not all interface methods are implemented, derived contracts
+ * must do so themselves.
+ */
+contract GSNRecipient is Initializable, IRelayRecipient, GSNContext, GSNBouncerBase {
+    function initialize() public initializer {
+        GSNContext.initialize();
+    }
+
+    function getHubAddr() public view returns (address) {
+        return _getRelayHub();
+    }
+
+    // This function is view for future-proofing, it may require reading from
+    // storage in the future.
+    function relayHubVersion() public view returns (string memory) {
+        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
+        return "1.0.0";
+    }
+
+    function _withdrawDeposits(uint256 amount, address payable payee) internal {
+        IRelayHub(_getRelayHub()).withdraw(amount, payee);
+    }
+}

contracts/GSN/IRelayHub.sol

@@ -0,0 +1,188 @@
+pragma solidity ^0.5.0;
+
+contract IRelayHub {
+    // Relay management
+
+    // Add stake to a relay and sets its unstakeDelay.
+    // If the relay does not exist, it is created, and the caller
+    // of this function becomes its owner. If the relay already exists, only the owner can call this function. A relay
+    // cannot be its own owner.
+    // All Ether in this function call will be added to the relay's stake.
+    // Its unstake delay will be assigned to unstakeDelay, but the new value must be greater or equal to the current one.
+    // Emits a Staked event.
+    function stake(address relayaddr, uint256 unstakeDelay) external payable;
+
+    // Emited when a relay's stake or unstakeDelay are increased
+    event Staked(address indexed relay, uint256 stake, uint256 unstakeDelay);
+
+    // Registers the caller as a relay.
+    // The relay must be staked for, and not be a contract (i.e. this function must be called directly from an EOA).
+    // Emits a RelayAdded event.
+    // This function can be called multiple times, emitting new RelayAdded events. Note that the received transactionFee
+    // is not enforced by relayCall.
+    function registerRelay(uint256 transactionFee, string memory url) public;
+
+    // Emitted when a relay is registered or re-registerd. Looking at these events (and filtering out RelayRemoved
+    // events) lets a client discover the list of available relays.
+    event RelayAdded(address indexed relay, address indexed owner, uint256 transactionFee, uint256 stake, uint256 unstakeDelay, string url);
+
+    // Removes (deregisters) a relay. Unregistered (but staked for) relays can also be removed. Can only be called by
+    // the owner of the relay. After the relay's unstakeDelay has elapsed, unstake will be callable.
+    // Emits a RelayRemoved event.
+    function removeRelayByOwner(address relay) public;
+
+    // Emitted when a relay is removed (deregistered). unstakeTime is the time when unstake will be callable.
+    event RelayRemoved(address indexed relay, uint256 unstakeTime);
+
+    // Deletes the relay from the system, and gives back its stake to the owner. Can only be called by the relay owner,
+    // after unstakeDelay has elapsed since removeRelayByOwner was called.
+    // Emits an Unstaked event.
+    function unstake(address relay) public;
+
+    // Emitted when a relay is unstaked for, including the returned stake.
+    event Unstaked(address indexed relay, uint256 stake);
+
+    // States a relay can be in
+    enum RelayState {
+        Unknown, // The relay is unknown to the system: it has never been staked for
+        Staked, // The relay has been staked for, but it is not yet active
+        Registered, // The relay has registered itself, and is active (can relay calls)
+        Removed    // The relay has been removed by its owner and can no longer relay calls. It must wait for its unstakeDelay to elapse before it can unstake
+    }
+
+    // Returns a relay's status. Note that relays can be deleted when unstaked or penalized.
+    function getRelay(address relay) external view returns (uint256 totalStake, uint256 unstakeDelay, uint256 unstakeTime, address payable owner, RelayState state);
+
+    // Balance management
+
+    // Deposits ether for a contract, so that it can receive (and pay for) relayed transactions. Unused balance can only
+    // be withdrawn by the contract itself, by callingn withdraw.
+    // Emits a Deposited event.
+    function depositFor(address target) public payable;
+
+    // Emitted when depositFor is called, including the amount and account that was funded.
+    event Deposited(address indexed recipient, address indexed from, uint256 amount);
+
+    // Returns an account's deposits. These can be either a contnract's funds, or a relay owner's revenue.
+    function balanceOf(address target) external view returns (uint256);
+
+    // Withdraws from an account's balance, sending it back to it. Relay owners call this to retrieve their revenue, and
+    // contracts can also use it to reduce their funding.
+    // Emits a Withdrawn event.
+    function withdraw(uint256 amount, address payable dest) public;
+
+    // Emitted when an account withdraws funds from RelayHub.
+    event Withdrawn(address indexed account, address indexed dest, uint256 amount);
+
+    // Relaying
+
+    // Check if the RelayHub will accept a relayed operation. Multiple things must be true for this to happen:
+    //  - all arguments must be signed for by the sender (from)
+    //  - the sender's nonce must be the current one
+    //  - the recipient must accept this transaction (via acceptRelayedCall)
+    // Returns a PreconditionCheck value (OK when the transaction can be relayed), or a recipient-specific error code if
+    // it returns one in acceptRelayedCall.
+    function canRelay(
+        address relay,
+        address from,
+        address to,
+        bytes memory encodedFunction,
+        uint256 transactionFee,
+        uint256 gasPrice,
+        uint256 gasLimit,
+        uint256 nonce,
+        bytes memory signature,
+        bytes memory approvalData
+    ) public view returns (uint256 status, bytes memory recipientContext);
+
+    // Preconditions for relaying, checked by canRelay and returned as the corresponding numeric values.
+    enum PreconditionCheck {
+        OK,                         // All checks passed, the call can be relayed
+        WrongSignature,             // The transaction to relay is not signed by requested sender
+        WrongNonce,                 // The provided nonce has already been used by the sender
+        AcceptRelayedCallReverted,  // The recipient rejected this call via acceptRelayedCall
+        InvalidRecipientStatusCode  // The recipient returned an invalid (reserved) status code
+    }
+
+    // Relays a transaction. For this to suceed, multiple conditions must be met:
+    //  - canRelay must return PreconditionCheck.OK
+    //  - the sender must be a registered relay
+    //  - the transaction's gas price must be larger or equal to the one that was requested by the sender
+    //  - the transaction must have enough gas to not run out of gas if all internal transactions (calls to the
+    // recipient) use all gas available to them
+    //  - the recipient must have enough balance to pay the relay for the worst-case scenario (i.e. when all gas is
+    // spent)
+    //
+    // If all conditions are met, the call will be relayed and the recipient charged. preRelayedCall, the encoded
+    // function and postRelayedCall will be called in order.
+    //
+    // Arguments:
+    //  - from: the client originating the request
+    //  - recipient: the target IRelayRecipient contract
+    //  - encodedFunction: the function call to relay, including data
+    //  - transactionFee: fee (%) the relay takes over actual gas cost
+    //  - gasPrice: gas price the client is willing to pay
+    //  - gasLimit: gas to forward when calling the encoded function
+    //  - nonce: client's nonce
+    //  - signature: client's signature over all previous params, plus the relay and RelayHub addresses
+    //  - approvalData: dapp-specific data forwared to acceptRelayedCall. This value is *not* verified by the Hub, but
+    //    it still can be used for e.g. a signature.
+    //
+    // Emits a TransactionRelayed event.
+    function relayCall(
+        address from,
+        address to,
+        bytes memory encodedFunction,
+        uint256 transactionFee,
+        uint256 gasPrice,
+        uint256 gasLimit,
+        uint256 nonce,
+        bytes memory signature,
+        bytes memory approvalData
+    ) public;
+
+    // Emitted when an attempt to relay a call failed. This can happen due to incorrect relayCall arguments, or the
+    // recipient not accepting the relayed call. The actual relayed call was not executed, and the recipient not charged.
+    // The reason field contains an error code: values 1-10 correspond to PreconditionCheck entries, and values over 10
+    // are custom recipient error codes returned from acceptRelayedCall.
+    event CanRelayFailed(address indexed relay, address indexed from, address indexed to, bytes4 selector, uint256 reason);
+
+    // Emitted when a transaction is relayed. Note that the actual encoded function might be reverted: this will be
+    // indicated in the status field.
+    // Useful when monitoring a relay's operation and relayed calls to a contract.
+    // Charge is the ether value deducted from the recipient's balance, paid to the relay's owner.
+    event TransactionRelayed(address indexed relay, address indexed from, address indexed to, bytes4 selector, RelayCallStatus status, uint256 charge);
+
+    // Reason error codes for the TransactionRelayed event
+    enum RelayCallStatus {
+        OK,                      // The transaction was successfully relayed and execution successful - never included in the event
+        RelayedCallFailed,       // The transaction was relayed, but the relayed call failed
+        PreRelayedFailed,        // The transaction was not relayed due to preRelatedCall reverting
+        PostRelayedFailed,       // The transaction was relayed and reverted due to postRelatedCall reverting
+        RecipientBalanceChanged  // The transaction was relayed and reverted due to the recipient's balance changing
+    }
+
+    // Returns how much gas should be forwarded to a call to relayCall, in order to relay a transaction that will spend
+    // up to relayedCallStipend gas.
+    function requiredGas(uint256 relayedCallStipend) public view returns (uint256);
+
+    // Returns the maximum recipient charge, given the amount of gas forwarded, gas price and relay fee.
+    function maxPossibleCharge(uint256 relayedCallStipend, uint256 gasPrice, uint256 transactionFee) public view returns (uint256);
+
+    // Relay penalization. Any account can penalize relays, removing them from the system immediately, and rewarding the
+    // reporter with half of the relay's stake. The other half is burned so that, even if the relay penalizes itself, it
+    // still loses half of its stake.
+
+    // Penalize a relay that signed two transactions using the same nonce (making only the first one valid) and
+    // different data (gas price, gas limit, etc. may be different). The (unsigned) transaction data and signature for
+    // both transactions must be provided.
+    function penalizeRepeatedNonce(bytes memory unsignedTx1, bytes memory signature1, bytes memory unsignedTx2, bytes memory signature2) public;
+
+    // Penalize a relay that sent a transaction that didn't target RelayHub's registerRelay or relayCall.
+    function penalizeIllegalTransaction(bytes memory unsignedTx, bytes memory signature) public;
+
+    event Penalized(address indexed relay, address sender, uint256 amount);
+
+    function getNonce(address from) external view returns (uint256);
+}
+

contracts/GSN/IRelayRecipient.sol

@@ -0,0 +1,30 @@
+pragma solidity ^0.5.0;
+
+/*
+ * @dev Interface for a contract that will be called via the GSN from RelayHub.
+ */
+contract IRelayRecipient {
+    /**
+     * @dev Returns the address of the RelayHub instance this recipient interacts with.
+     */
+    function getHubAddr() public view returns (address);
+
+    function acceptRelayedCall(
+        address relay,
+        address from,
+        bytes calldata encodedFunction,
+        uint256 transactionFee,
+        uint256 gasPrice,
+        uint256 gasLimit,
+        uint256 nonce,
+        bytes calldata approvalData,
+        uint256 maxPossibleCharge
+    )
+        external
+        view
+        returns (uint256, bytes memory);
+
+    function preRelayedCall(bytes calldata context) external returns (bytes32);
+
+    function postRelayedCall(bytes calldata context, bool success, uint actualCharge, bytes32 preRetVal) external;
+}

contracts/GSN/bouncers/GSNBouncerBase.sol

@@ -0,0 +1,92 @@
+pragma solidity ^0.5.0;
+
+import "../IRelayRecipient.sol";
+
+/*
+ * @dev Base contract used to implement GSNBouncers.
+ *
+ * > This contract does not perform all required tasks to implement a GSN
+ * recipient contract: end users should use `GSNRecipient` instead.
+ */
+contract GSNBouncerBase is IRelayRecipient {
+    uint256 constant private RELAYED_CALL_ACCEPTED = 0;
+    uint256 constant private RELAYED_CALL_REJECTED = 11;
+
+    // How much gas is forwarded to postRelayedCall
+    uint256 constant internal POST_RELAYED_CALL_MAX_GAS = 100000;
+
+    // Base implementations for pre and post relayedCall: only RelayHub can invoke them, and data is forwarded to the
+    // internal hook.
+
+    /**
+     * @dev See `IRelayRecipient.preRelayedCall`.
+     *
+     * This function should not be overriden directly, use `_preRelayedCall` instead.
+     *
+     * * Requirements:
+     *
+     * - the caller must be the `RelayHub` contract.
+     */
+    function preRelayedCall(bytes calldata context) external returns (bytes32) {
+        require(msg.sender == getHubAddr(), "GSNBouncerBase: caller is not RelayHub");
+        return _preRelayedCall(context);
+    }
+
+    /**
+     * @dev See `IRelayRecipient.postRelayedCall`.
+     *
+     * This function should not be overriden directly, use `_postRelayedCall` instead.
+     *
+     * * Requirements:
+     *
+     * - the caller must be the `RelayHub` contract.
+     */
+    function postRelayedCall(bytes calldata context, bool success, uint256 actualCharge, bytes32 preRetVal) external {
+        require(msg.sender == getHubAddr(), "GSNBouncerBase: caller is not RelayHub");
+        _postRelayedCall(context, success, actualCharge, preRetVal);
+    }
+
+    /**
+     * @dev Return this in acceptRelayedCall to proceed with the execution of a relayed call. Note that this contract
+     * will be charged a fee by RelayHub
+     */
+    function _approveRelayedCall() internal pure returns (uint256, bytes memory) {
+        return _approveRelayedCall("");
+    }
+
+    /**
+     * @dev See `GSNBouncerBase._approveRelayedCall`.
+     *
+     * This overload forwards `context` to _preRelayedCall and _postRelayedCall.
+     */
+    function _approveRelayedCall(bytes memory context) internal pure returns (uint256, bytes memory) {
+        return (RELAYED_CALL_ACCEPTED, context);
+    }
+
+    /**
+     * @dev Return this in acceptRelayedCall to impede execution of a relayed call. No fees will be charged.
+     */
+    function _rejectRelayedCall(uint256 errorCode) internal pure returns (uint256, bytes memory) {
+        return (RELAYED_CALL_REJECTED + errorCode, "");
+    }
+
+    // Empty hooks for pre and post relayed call: users only have to define these if they actually use them.
+
+    function _preRelayedCall(bytes memory) internal returns (bytes32) {
+        // solhint-disable-previous-line no-empty-blocks
+    }
+
+    function _postRelayedCall(bytes memory, bool, uint256, bytes32) internal {
+        // solhint-disable-previous-line no-empty-blocks
+    }
+
+    /*
+     * @dev Calculates how much RelaHub will charge a recipient for using `gas` at a `gasPrice`, given a relayer's
+     * `serviceFee`.
+     */
+    function _computeCharge(uint256 gas, uint256 gasPrice, uint256 serviceFee) internal pure returns (uint256) {
+        // The fee is expressed as a percentage. E.g. a value of 40 stands for a 40% fee, so the recipient will be
+        // charged for 1.4 times the spent amount.
+        return (gas * gasPrice * (100 + serviceFee)) / 100;
+    }
+}

contracts/GSN/bouncers/GSNBouncerERC20Fee.sol

@@ -0,0 +1,143 @@
+pragma solidity ^0.5.0;
+
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
+import "./GSNBouncerBase.sol";
+import "../../math/SafeMath.sol";
+import "../../ownership/Secondary.sol";
+import "../../token/ERC20/SafeERC20.sol";
+import "../../token/ERC20/ERC20.sol";
+import "../../token/ERC20/ERC20Detailed.sol";
+
+contract GSNBouncerERC20Fee is Initializable, GSNBouncerBase {
+    using SafeERC20 for __unstable__ERC20PrimaryAdmin;
+    using SafeMath for uint256;
+
+    enum GSNBouncerERC20FeeErrorCodes {
+        INSUFFICIENT_BALANCE
+    }
+
+    // We use a random storage slot to allow proxy contracts to enable GSN support in an upgrade without changing their
+    // storage layout. This value is calculated as: keccak256('gsn.bouncer.signature.token'), minus 1.
+    bytes32 constant private TOKEN_STORAGE_SLOT = 0xd918b70a5a5c95a8c0cac8acbdd59e1b4acd0645f53c0461d64b41f8825c8828;
+
+    function initialize(string memory name, string memory symbol, uint8 decimals) initializer public {
+        // TODO: Should we inject this token, instead of creating it, in order to make it upgradeable?
+        // However, that would mean removing it from unstable and making in an official contract
+        _setToken(new __unstable__ERC20PrimaryAdmin(name, symbol, decimals));
+    }
+
+    function token() public view returns (IERC20) {
+        return IERC20(_getToken());
+    }
+
+    function _mint(address account, uint256 amount) internal {
+        _getToken().mint(account, amount);
+    }
+
+    function acceptRelayedCall(
+        address,
+        address from,
+        bytes calldata,
+        uint256 transactionFee,
+        uint256 gasPrice,
+        uint256,
+        uint256,
+        bytes calldata,
+        uint256 maxPossibleCharge
+    )
+        external
+        view
+        returns (uint256, bytes memory)
+    {
+        if (_getToken().balanceOf(from) < maxPossibleCharge) {
+            return _rejectRelayedCall(uint256(GSNBouncerERC20FeeErrorCodes.INSUFFICIENT_BALANCE));
+        }
+
+        return _approveRelayedCall(abi.encode(from, maxPossibleCharge, transactionFee, gasPrice));
+    }
+
+    function _preRelayedCall(bytes memory context) internal returns (bytes32) {
+        (address from, uint256 maxPossibleCharge) = abi.decode(context, (address, uint256));
+
+        // The maximum token charge is pre-charged from the user
+        _getToken().safeTransferFrom(from, address(this), maxPossibleCharge);
+    }
+
+    function _postRelayedCall(bytes memory context, bool, uint256 actualCharge, bytes32) internal {
+        (address from, uint256 maxPossibleCharge, uint256 transactionFee, uint256 gasPrice) =
+            abi.decode(context, (address, uint256, uint256, uint256));
+
+        // actualCharge is an _estimated_ charge, which assumes postRelayedCall will use all available gas.
+        // This implementation's gas cost can be roughly estimated as 10k gas, for the two SSTORE operations in an
+        // ERC20 transfer.
+        uint256 overestimation = _computeCharge(POST_RELAYED_CALL_MAX_GAS.sub(10000), gasPrice, transactionFee);
+        actualCharge = actualCharge.sub(overestimation);
+
+        // After the relayed call has been executed and the actual charge estimated, the excess pre-charge is returned
+        _getToken().safeTransfer(from, maxPossibleCharge.sub(actualCharge));
+    }
+
+    function _getToken() private view returns (__unstable__ERC20PrimaryAdmin token) {
+      bytes32 slot = TOKEN_STORAGE_SLOT;
+      // solhint-disable-next-line no-inline-assembly
+      assembly {
+        token := sload(slot)
+      }
+    }
+
+    function _setToken(__unstable__ERC20PrimaryAdmin token) private {
+      bytes32 slot = TOKEN_STORAGE_SLOT;
+      // solhint-disable-next-line no-inline-assembly
+      assembly {
+        sstore(slot, token)
+      }
+    }
+}
+
+/**
+ * @title __unstable__ERC20PrimaryAdmin
+ * @dev An ERC20 token owned by another contract, which has minting permissions and can use transferFrom to receive
+ * anyone's tokens. This contract is an internal helper for GSNRecipientERC20Fee, and should not be used
+ * outside of this context.
+ */
+// solhint-disable-next-line contract-name-camelcase
+contract __unstable__ERC20PrimaryAdmin is ERC20, ERC20Detailed, Secondary {
+    uint256 private constant UINT256_MAX = 2**256 - 1;
+
+    constructor(string memory name, string memory symbol, uint8 decimals) public {
+        Secondary.initialize(msg.sender);
+        ERC20Detailed.initialize(name, symbol, decimals);
+    }
+
+    // The primary account (GSNRecipientERC20Fee) can mint tokens
+    function mint(address account, uint256 amount) public onlyPrimary {
+        _mint(account, amount);
+    }
+
+    // The primary account has 'infinite' allowance for all token holders
+    function allowance(address owner, address spender) public view returns (uint256) {
+        if (spender == primary()) {
+            return UINT256_MAX;
+        } else {
+            return super.allowance(owner, spender);
+        }
+    }
+
+    // Allowance for the primary account cannot be changed (it is always 'infinite')
+    function _approve(address owner, address spender, uint256 value) internal {
+        if (spender == primary()) {
+            return;
+        } else {
+            super._approve(owner, spender, value);
+        }
+    }
+
+    function transferFrom(address sender, address recipient, uint256 amount) public returns (bool) {
+        if (recipient == primary()) {
+            _transfer(sender, recipient, amount);
+            return true;
+        } else {
+            return super.transferFrom(sender, recipient, amount);
+        }
+    }
+}

contracts/GSN/bouncers/GSNBouncerSignature.sol

@@ -0,0 +1,70 @@
+pragma solidity ^0.5.0;
+
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
+import "./GSNBouncerBase.sol";
+import "../../cryptography/ECDSA.sol";
+
+contract GSNBouncerSignature is Initializable, GSNBouncerBase {
+    using ECDSA for bytes32;
+
+    // We use a random storage slot to allow proxy contracts to enable GSN support in an upgrade without changing their
+    // storage layout. This value is calculated as: keccak256('gsn.bouncer.signature.trustedSigner'), minus 1.
+    bytes32 constant private TRUSTED_SIGNER_STORAGE_SLOT = 0xe7b237a4017a399d277819456dce32c2356236bbc518a6d84a9a8d1cfdf1e9c5;
+
+    enum GSNBouncerSignatureErrorCodes {
+        INVALID_SIGNER
+    }
+
+    function initialize(address trustedSigner) public initializer {
+        _setTrustedSigner(trustedSigner);
+    }
+
+    function acceptRelayedCall(
+        address relay,
+        address from,
+        bytes calldata encodedFunction,
+        uint256 transactionFee,
+        uint256 gasPrice,
+        uint256 gasLimit,
+        uint256 nonce,
+        bytes calldata approvalData,
+        uint256
+    )
+        external
+        view
+        returns (uint256, bytes memory)
+    {
+        bytes memory blob = abi.encodePacked(
+            relay,
+            from,
+            encodedFunction,
+            transactionFee,
+            gasPrice,
+            gasLimit,
+            nonce, // Prevents replays on RelayHub
+            getHubAddr(), // Prevents replays in multiple RelayHubs
+            address(this) // Prevents replays in multiple recipients
+        );
+        if (keccak256(blob).toEthSignedMessageHash().recover(approvalData) == _getTrustedSigner()) {
+            return _approveRelayedCall();
+        } else {
+            return _rejectRelayedCall(uint256(GSNBouncerSignatureErrorCodes.INVALID_SIGNER));
+        }
+    }
+
+    function _getTrustedSigner() private view returns (address trustedSigner) {
+      bytes32 slot = TRUSTED_SIGNER_STORAGE_SLOT;
+      // solhint-disable-next-line no-inline-assembly
+      assembly {
+        trustedSigner := sload(slot)
+      }
+    }
+
+    function _setTrustedSigner(address trustedSigner) private {
+      bytes32 slot = TRUSTED_SIGNER_STORAGE_SLOT;
+      // solhint-disable-next-line no-inline-assembly
+      assembly {
+        sstore(slot, trustedSigner)
+      }
+    }
+}

contracts/access/Roles.sol

@@ -1,44 +1,40 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
 /**
  * @title Roles
  * @dev Library for managing addresses assigned to a Role.
  */
 library Roles {
-  struct Role {
-    mapping (address => bool) bearer;
-  }
+    struct Role {
+        mapping (address => bool) bearer;
+    }
 
-  /**
-   * @dev give an account access to this role
-   */
-  function add(Role storage role, address account) internal {
-    require(account != address(0));
-    require(!has(role, account));
+    /**
+     * @dev give an account access to this role
+     */
+    function add(Role storage role, address account) internal {
+        require(account != address(0));
+        require(!has(role, account));
 
-    role.bearer[account] = true;
-  }
+        role.bearer[account] = true;
+    }
 
-  /**
-   * @dev remove an account's access to this role
-   */
-  function remove(Role storage role, address account) internal {
-    require(account != address(0));
-    require(has(role, account));
+    /**
+     * @dev remove an account's access to this role
+     */
+    function remove(Role storage role, address account) internal {
+        require(account != address(0));
+        require(has(role, account));
 
-    role.bearer[account] = false;
-  }
+        role.bearer[account] = false;
+    }
 
-  /**
-   * @dev check if an account has this role
-   * @return bool
-   */
-  function has(Role storage role, address account)
-    internal
-    view
-    returns (bool)
-  {
-    require(account != address(0));
-    return role.bearer[account];
-  }
+    /**
+     * @dev check if an account has this role
+     * @return bool
+     */
+    function has(Role storage role, address account) internal view returns (bool) {
+        require(account != address(0));
+        return role.bearer[account];
+    }
 }

contracts/access/roles/CapperRole.sol

@@ -1,43 +1,49 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
 import "../Roles.sol";
 
-contract CapperRole {
-  using Roles for Roles.Role;
 
-  event CapperAdded(address indexed account);
-  event CapperRemoved(address indexed account);
+contract CapperRole is Initializable {
+    using Roles for Roles.Role;
 
-  Roles.Role private cappers;
+    event CapperAdded(address indexed account);
+    event CapperRemoved(address indexed account);
 
-  constructor() internal {
-    _addCapper(msg.sender);
-  }
+    Roles.Role private _cappers;
 
-  modifier onlyCapper() {
-    require(isCapper(msg.sender));
-    _;
-  }
+    function initialize(address sender) public initializer {
+        if (!isCapper(sender)) {
+            _addCapper(sender);
+        }
+    }
 
-  function isCapper(address account) public view returns (bool) {
-    return cappers.has(account);
-  }
+    modifier onlyCapper() {
+        require(isCapper(msg.sender));
+        _;
+    }
 
-  function addCapper(address account) public onlyCapper {
-    _addCapper(account);
-  }
+    function isCapper(address account) public view returns (bool) {
+        return _cappers.has(account);
+    }
 
-  function renounceCapper() public {
-    _removeCapper(msg.sender);
-  }
+    function addCapper(address account) public onlyCapper {
+        _addCapper(account);
+    }
 
-  function _addCapper(address account) internal {
-    cappers.add(account);
-    emit CapperAdded(account);
-  }
+    function renounceCapper() public {
+        _removeCapper(msg.sender);
+    }
 
-  function _removeCapper(address account) internal {
-    cappers.remove(account);
-    emit CapperRemoved(account);
-  }
+    function _addCapper(address account) internal {
+        _cappers.add(account);
+        emit CapperAdded(account);
+    }
+
+    function _removeCapper(address account) internal {
+        _cappers.remove(account);
+        emit CapperRemoved(account);
+    }
+
+    uint256[50] private ______gap;
 }

contracts/access/roles/MinterRole.sol

@@ -1,43 +1,49 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
 import "../Roles.sol";
 
-contract MinterRole {
-  using Roles for Roles.Role;
 
-  event MinterAdded(address indexed account);
-  event MinterRemoved(address indexed account);
+contract MinterRole is Initializable {
+    using Roles for Roles.Role;
 
-  Roles.Role private minters;
+    event MinterAdded(address indexed account);
+    event MinterRemoved(address indexed account);
 
-  constructor() internal {
-    _addMinter(msg.sender);
-  }
+    Roles.Role private _minters;
 
-  modifier onlyMinter() {
-    require(isMinter(msg.sender));
-    _;
-  }
+    function initialize(address sender) public initializer {
+        if (!isMinter(sender)) {
+            _addMinter(sender);
+        }
+    }
 
-  function isMinter(address account) public view returns (bool) {
-    return minters.has(account);
-  }
+    modifier onlyMinter() {
+        require(isMinter(msg.sender));
+        _;
+    }
 
-  function addMinter(address account) public onlyMinter {
-    _addMinter(account);
-  }
+    function isMinter(address account) public view returns (bool) {
+        return _minters.has(account);
+    }
 
-  function renounceMinter() public {
-    _removeMinter(msg.sender);
-  }
+    function addMinter(address account) public onlyMinter {
+        _addMinter(account);
+    }
 
-  function _addMinter(address account) internal {
-    minters.add(account);
-    emit MinterAdded(account);
-  }
+    function renounceMinter() public {
+        _removeMinter(msg.sender);
+    }
 
-  function _removeMinter(address account) internal {
-    minters.remove(account);
-    emit MinterRemoved(account);
-  }
+    function _addMinter(address account) internal {
+        _minters.add(account);
+        emit MinterAdded(account);
+    }
+
+    function _removeMinter(address account) internal {
+        _minters.remove(account);
+        emit MinterRemoved(account);
+    }
+
+    uint256[50] private ______gap;
 }

contracts/access/roles/PauserRole.sol

@@ -1,43 +1,49 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
 import "../Roles.sol";
 
-contract PauserRole {
-  using Roles for Roles.Role;
 
-  event PauserAdded(address indexed account);
-  event PauserRemoved(address indexed account);
+contract PauserRole is Initializable {
+    using Roles for Roles.Role;
 
-  Roles.Role private pausers;
+    event PauserAdded(address indexed account);
+    event PauserRemoved(address indexed account);
 
-  constructor() internal {
-    _addPauser(msg.sender);
-  }
+    Roles.Role private _pausers;
 
-  modifier onlyPauser() {
-    require(isPauser(msg.sender));
-    _;
-  }
+    function initialize(address sender) public initializer {
+        if (!isPauser(sender)) {
+            _addPauser(sender);
+        }
+    }
 
-  function isPauser(address account) public view returns (bool) {
-    return pausers.has(account);
-  }
+    modifier onlyPauser() {
+        require(isPauser(msg.sender));
+        _;
+    }
 
-  function addPauser(address account) public onlyPauser {
-    _addPauser(account);
-  }
+    function isPauser(address account) public view returns (bool) {
+        return _pausers.has(account);
+    }
 
-  function renouncePauser() public {
-    _removePauser(msg.sender);
-  }
+    function addPauser(address account) public onlyPauser {
+        _addPauser(account);
+    }
 
-  function _addPauser(address account) internal {
-    pausers.add(account);
-    emit PauserAdded(account);
-  }
+    function renouncePauser() public {
+        _removePauser(msg.sender);
+    }
 
-  function _removePauser(address account) internal {
-    pausers.remove(account);
-    emit PauserRemoved(account);
-  }
+    function _addPauser(address account) internal {
+        _pausers.add(account);
+        emit PauserAdded(account);
+    }
+
+    function _removePauser(address account) internal {
+        _pausers.remove(account);
+        emit PauserRemoved(account);
+    }
+
+    uint256[50] private ______gap;
 }

contracts/access/roles/SignerRole.sol

@@ -1,43 +1,49 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
 import "../Roles.sol";
 
-contract SignerRole {
-  using Roles for Roles.Role;
 
-  event SignerAdded(address indexed account);
-  event SignerRemoved(address indexed account);
+contract SignerRole is Initializable {
+    using Roles for Roles.Role;
 
-  Roles.Role private signers;
+    event SignerAdded(address indexed account);
+    event SignerRemoved(address indexed account);
 
-  constructor() internal {
-    _addSigner(msg.sender);
-  }
+    Roles.Role private _signers;
 
-  modifier onlySigner() {
-    require(isSigner(msg.sender));
-    _;
-  }
+    function initialize(address sender) public initializer {
+        if (!isSigner(sender)) {
+            _addSigner(sender);
+        }
+    }
 
-  function isSigner(address account) public view returns (bool) {
-    return signers.has(account);
-  }
+    modifier onlySigner() {
+        require(isSigner(msg.sender));
+        _;
+    }
 
-  function addSigner(address account) public onlySigner {
-    _addSigner(account);
-  }
+    function isSigner(address account) public view returns (bool) {
+        return _signers.has(account);
+    }
 
-  function renounceSigner() public {
-    _removeSigner(msg.sender);
-  }
+    function addSigner(address account) public onlySigner {
+        _addSigner(account);
+    }
 
-  function _addSigner(address account) internal {
-    signers.add(account);
-    emit SignerAdded(account);
-  }
+    function renounceSigner() public {
+        _removeSigner(msg.sender);
+    }
 
-  function _removeSigner(address account) internal {
-    signers.remove(account);
-    emit SignerRemoved(account);
-  }
+    function _addSigner(address account) internal {
+        _signers.add(account);
+        emit SignerAdded(account);
+    }
+
+    function _removeSigner(address account) internal {
+        _signers.remove(account);
+        emit SignerRemoved(account);
+    }
+
+    uint256[50] private ______gap;
 }

contracts/access/roles/WhitelistAdminRole.sol

@@ -0,0 +1,53 @@
+pragma solidity ^0.5.2;
+
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
+
+import "../Roles.sol";
+
+/**
+ * @title WhitelistAdminRole
+ * @dev WhitelistAdmins are responsible for assigning and removing Whitelisted accounts.
+ */
+contract WhitelistAdminRole is Initializable {
+    using Roles for Roles.Role;
+
+    event WhitelistAdminAdded(address indexed account);
+    event WhitelistAdminRemoved(address indexed account);
+
+    Roles.Role private _whitelistAdmins;
+
+    function initialize(address sender) public initializer {
+        if (!isWhitelistAdmin(sender)) {
+            _addWhitelistAdmin(sender);
+        }
+    }
+
+    modifier onlyWhitelistAdmin() {
+        require(isWhitelistAdmin(msg.sender));
+        _;
+    }
+
+    function isWhitelistAdmin(address account) public view returns (bool) {
+        return _whitelistAdmins.has(account);
+    }
+
+    function addWhitelistAdmin(address account) public onlyWhitelistAdmin {
+        _addWhitelistAdmin(account);
+    }
+
+    function renounceWhitelistAdmin() public {
+        _removeWhitelistAdmin(msg.sender);
+    }
+
+    function _addWhitelistAdmin(address account) internal {
+        _whitelistAdmins.add(account);
+        emit WhitelistAdminAdded(account);
+    }
+
+    function _removeWhitelistAdmin(address account) internal {
+        _whitelistAdmins.remove(account);
+        emit WhitelistAdminRemoved(account);
+    }
+
+    uint256[50] private ______gap;
+}

contracts/access/roles/WhitelistedRole.sol

@@ -0,0 +1,58 @@
+pragma solidity ^0.5.2;
+
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
+
+import "../Roles.sol";
+import "./WhitelistAdminRole.sol";
+
+/**
+ * @title WhitelistedRole
+ * @dev Whitelisted accounts have been approved by a WhitelistAdmin to perform certain actions (e.g. participate in a
+ * crowdsale). This role is special in that the only accounts that can add it are WhitelistAdmins (who can also remove
+ * it), and not Whitelisteds themselves.
+ */
+contract WhitelistedRole is Initializable, WhitelistAdminRole {
+    using Roles for Roles.Role;
+
+    event WhitelistedAdded(address indexed account);
+    event WhitelistedRemoved(address indexed account);
+
+    Roles.Role private _whitelisteds;
+
+    modifier onlyWhitelisted() {
+        require(isWhitelisted(msg.sender));
+        _;
+    }
+
+    function initialize(address sender) public initializer {
+        WhitelistAdminRole.initialize(sender);
+    }
+
+    function isWhitelisted(address account) public view returns (bool) {
+        return _whitelisteds.has(account);
+    }
+
+    function addWhitelisted(address account) public onlyWhitelistAdmin {
+        _addWhitelisted(account);
+    }
+
+    function removeWhitelisted(address account) public onlyWhitelistAdmin {
+        _removeWhitelisted(account);
+    }
+
+    function renounceWhitelisted() public {
+        _removeWhitelisted(msg.sender);
+    }
+
+    function _addWhitelisted(address account) internal {
+        _whitelisteds.add(account);
+        emit WhitelistedAdded(account);
+    }
+
+    function _removeWhitelisted(address account) internal {
+        _whitelisteds.remove(account);
+        emit WhitelistedRemoved(account);
+    }
+
+    uint256[50] private ______gap;
+}

contracts/crowdsale/Crowdsale.sol

@@ -1,5 +1,6 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
 import "../token/ERC20/IERC20.sol";
 import "../math/SafeMath.sol";
 import "../token/ERC20/SafeERC20.sol";
@@ -11,231 +12,194 @@ import "../utils/ReentrancyGuard.sol";
  * allowing investors to purchase tokens with ether. This contract implements
  * such functionality in its most fundamental form and can be extended to provide additional
  * functionality and/or custom behavior.
- * The external interface represents the basic interface for purchasing tokens, and conform
- * the base architecture for crowdsales. They are *not* intended to be modified / overridden.
+ * The external interface represents the basic interface for purchasing tokens, and conforms
+ * the base architecture for crowdsales. It is *not* intended to be modified / overridden.
  * The internal interface conforms the extensible and modifiable surface of crowdsales. Override
  * the methods to add functionality. Consider using 'super' where appropriate to concatenate
  * behavior.
  */
-contract Crowdsale is ReentrancyGuard {
-  using SafeMath for uint256;
-  using SafeERC20 for IERC20;
+contract Crowdsale is Initializable, ReentrancyGuard {
+    using SafeMath for uint256;
+    using SafeERC20 for IERC20;
 
-  // The token being sold
-  IERC20 private _token;
+    // The token being sold
+    IERC20 private _token;
 
-  // Address where funds are collected
-  address private _wallet;
+    // Address where funds are collected
+    address payable private _wallet;
 
-  // How many token units a buyer gets per wei.
-  // The rate is the conversion between wei and the smallest and indivisible token unit.
-  // So, if you are using a rate of 1 with a ERC20Detailed token with 3 decimals called TOK
-  // 1 wei will give you 1 unit, or 0.001 TOK.
-  uint256 private _rate;
+    // How many token units a buyer gets per wei.
+    // The rate is the conversion between wei and the smallest and indivisible token unit.
+    // So, if you are using a rate of 1 with a ERC20Detailed token with 3 decimals called TOK
+    // 1 wei will give you 1 unit, or 0.001 TOK.
+    uint256 private _rate;
 
-  // Amount of wei raised
-  uint256 private _weiRaised;
+    // Amount of wei raised
+    uint256 private _weiRaised;
 
-  /**
-   * Event for token purchase logging
-   * @param purchaser who paid for the tokens
-   * @param beneficiary who got the tokens
-   * @param value weis paid for purchase
-   * @param amount amount of tokens purchased
-   */
-  event TokensPurchased(
-    address indexed purchaser,
-    address indexed beneficiary,
-    uint256 value,
-    uint256 amount
-  );
+    /**
+     * Event for token purchase logging
+     * @param purchaser who paid for the tokens
+     * @param beneficiary who got the tokens
+     * @param value weis paid for purchase
+     * @param amount amount of tokens purchased
+     */
+    event TokensPurchased(address indexed purchaser, address indexed beneficiary, uint256 value, uint256 amount);
 
-  /**
-   * @param rate Number of token units a buyer gets per wei
-   * @dev The rate is the conversion between wei and the smallest and indivisible
-   * token unit. So, if you are using a rate of 1 with a ERC20Detailed token
-   * with 3 decimals called TOK, 1 wei will give you 1 unit, or 0.001 TOK.
-   * @param wallet Address where collected funds will be forwarded to
-   * @param token Address of the token being sold
-   */
-  constructor(uint256 rate, address wallet, IERC20 token) internal {
-    require(rate > 0);
-    require(wallet != address(0));
-    require(token != address(0));
+    /**
+     * @param rate Number of token units a buyer gets per wei
+     * @dev The rate is the conversion between wei and the smallest and indivisible
+     * token unit. So, if you are using a rate of 1 with a ERC20Detailed token
+     * with 3 decimals called TOK, 1 wei will give you 1 unit, or 0.001 TOK.
+     * @param wallet Address where collected funds will be forwarded to
+     * @param token Address of the token being sold
+     */
+    function initialize(uint256 rate, address payable wallet, IERC20 token) public initializer {
+        require(rate > 0);
+        require(wallet != address(0));
+        require(address(token) != address(0));
 
-    _rate = rate;
-    _wallet = wallet;
-    _token = token;
-  }
+        _rate = rate;
+        _wallet = wallet;
+        _token = token;
+    }
 
-  // -----------------------------------------
-  // Crowdsale external interface
-  // -----------------------------------------
+    /**
+     * @dev fallback function ***DO NOT OVERRIDE***
+     * Note that other contracts will transfer funds with a base gas stipend
+     * of 2300, which is not enough to call buyTokens. Consider calling
+     * buyTokens directly when purchasing tokens from a contract.
+     */
+    function () external payable {
+        buyTokens(msg.sender);
+    }
 
-  /**
-   * @dev fallback function ***DO NOT OVERRIDE***
-   * Note that other contracts will transfer fund with a base gas stipend
-   * of 2300, which is not enough to call buyTokens. Consider calling
-   * buyTokens directly when purchasing tokens from a contract.
-   */
-  function () external payable {
-    buyTokens(msg.sender);
-  }
+    /**
+     * @return the token being sold.
+     */
+    function token() public view returns (IERC20) {
+        return _token;
+    }
 
-  /**
-   * @return the token being sold.
-   */
-  function token() public view returns(IERC20) {
-    return _token;
-  }
+    /**
+     * @return the address where funds are collected.
+     */
+    function wallet() public view returns (address payable) {
+        return _wallet;
+    }
 
-  /**
-   * @return the address where funds are collected.
-   */
-  function wallet() public view returns(address) {
-    return _wallet;
-  }
+    /**
+     * @return the number of token units a buyer gets per wei.
+     */
+    function rate() public view returns (uint256) {
+        return _rate;
+    }
 
-  /**
-   * @return the number of token units a buyer gets per wei.
-   */
-  function rate() public view returns(uint256) {
-    return _rate;
-  }
+    /**
+     * @return the amount of wei raised.
+     */
+    function weiRaised() public view returns (uint256) {
+        return _weiRaised;
+    }
 
-  /**
-   * @return the amount of wei raised.
-   */
-  function weiRaised() public view returns (uint256) {
-    return _weiRaised;
-  }
+    /**
+     * @dev low level token purchase ***DO NOT OVERRIDE***
+     * This function has a non-reentrancy guard, so it shouldn't be called by
+     * another `nonReentrant` function.
+     * @param beneficiary Recipient of the token purchase
+     */
+    function buyTokens(address beneficiary) public nonReentrant payable {
+        uint256 weiAmount = msg.value;
+        _preValidatePurchase(beneficiary, weiAmount);
 
-  /**
-   * @dev low level token purchase ***DO NOT OVERRIDE***
-   * This function has a non-reentrancy guard, so it shouldn't be called by
-   * another `nonReentrant` function.
-   * @param beneficiary Recipient of the token purchase
-   */
-  function buyTokens(address beneficiary) public nonReentrant payable {
+        // calculate token amount to be created
+        uint256 tokens = _getTokenAmount(weiAmount);
 
-    uint256 weiAmount = msg.value;
-    _preValidatePurchase(beneficiary, weiAmount);
+        // update state
+        _weiRaised = _weiRaised.add(weiAmount);
 
-    // calculate token amount to be created
-    uint256 tokens = _getTokenAmount(weiAmount);
+        _processPurchase(beneficiary, tokens);
+        emit TokensPurchased(msg.sender, beneficiary, weiAmount, tokens);
 
-    // update state
-    _weiRaised = _weiRaised.add(weiAmount);
+        _updatePurchasingState(beneficiary, weiAmount);
 
-    _processPurchase(beneficiary, tokens);
-    emit TokensPurchased(
-      msg.sender,
-      beneficiary,
-      weiAmount,
-      tokens
-    );
+        _forwardFunds();
+        _postValidatePurchase(beneficiary, weiAmount);
+    }
 
-    _updatePurchasingState(beneficiary, weiAmount);
+    function _hasBeenInitialized() internal view returns (bool) {
+        return ((_rate > 0) && (_wallet != address(0)) && (address(_token) != address(0)));
+    }
 
-    _forwardFunds();
-    _postValidatePurchase(beneficiary, weiAmount);
-  }
+    /**
+     * @dev Validation of an incoming purchase. Use require statements to revert state when conditions are not met.
+     * Use `super` in contracts that inherit from Crowdsale to extend their validations.
+     * Example from CappedCrowdsale.sol's _preValidatePurchase method:
+     *     super._preValidatePurchase(beneficiary, weiAmount);
+     *     require(weiRaised().add(weiAmount) <= cap);
+     * @param beneficiary Address performing the token purchase
+     * @param weiAmount Value in wei involved in the purchase
+     */
+    function _preValidatePurchase(address beneficiary, uint256 weiAmount) internal view {
+        require(beneficiary != address(0));
+        require(weiAmount != 0);
+    }
 
-  // -----------------------------------------
-  // Internal interface (extensible)
-  // -----------------------------------------
+    /**
+     * @dev Validation of an executed purchase. Observe state and use revert statements to undo rollback when valid
+     * conditions are not met.
+     * @param beneficiary Address performing the token purchase
+     * @param weiAmount Value in wei involved in the purchase
+     */
+    function _postValidatePurchase(address beneficiary, uint256 weiAmount) internal view {
+        // solhint-disable-previous-line no-empty-blocks
+    }
 
-  /**
-   * @dev Validation of an incoming purchase. Use require statements to revert state when conditions are not met. Use `super` in contracts that inherit from Crowdsale to extend their validations.
-   * Example from CappedCrowdsale.sol's _preValidatePurchase method:
-   *   super._preValidatePurchase(beneficiary, weiAmount);
-   *   require(weiRaised().add(weiAmount) <= cap);
-   * @param beneficiary Address performing the token purchase
-   * @param weiAmount Value in wei involved in the purchase
-   */
-  function _preValidatePurchase(
-    address beneficiary,
-    uint256 weiAmount
-  )
-    internal
-    view
-  {
-    require(beneficiary != address(0));
-    require(weiAmount != 0);
-  }
+    /**
+     * @dev Source of tokens. Override this method to modify the way in which the crowdsale ultimately gets and sends
+     * its tokens.
+     * @param beneficiary Address performing the token purchase
+     * @param tokenAmount Number of tokens to be emitted
+     */
+    function _deliverTokens(address beneficiary, uint256 tokenAmount) internal {
+        _token.safeTransfer(beneficiary, tokenAmount);
+    }
 
-  /**
-   * @dev Validation of an executed purchase. Observe state and use revert statements to undo rollback when valid conditions are not met.
-   * @param beneficiary Address performing the token purchase
-   * @param weiAmount Value in wei involved in the purchase
-   */
-  function _postValidatePurchase(
-    address beneficiary,
-    uint256 weiAmount
-  )
-    internal
-    view
-  {
-    // optional override
-  }
+    /**
+     * @dev Executed when a purchase has been validated and is ready to be executed. Doesn't necessarily emit/send
+     * tokens.
+     * @param beneficiary Address receiving the tokens
+     * @param tokenAmount Number of tokens to be purchased
+     */
+    function _processPurchase(address beneficiary, uint256 tokenAmount) internal {
+        _deliverTokens(beneficiary, tokenAmount);
+    }
 
-  /**
-   * @dev Source of tokens. Override this method to modify the way in which the crowdsale ultimately gets and sends its tokens.
-   * @param beneficiary Address performing the token purchase
-   * @param tokenAmount Number of tokens to be emitted
-   */
-  function _deliverTokens(
-    address beneficiary,
-    uint256 tokenAmount
-  )
-    internal
-  {
-    _token.safeTransfer(beneficiary, tokenAmount);
-  }
+    /**
+     * @dev Override for extensions that require an internal state to check for validity (current user contributions,
+     * etc.)
+     * @param beneficiary Address receiving the tokens
+     * @param weiAmount Value in wei involved in the purchase
+     */
+    function _updatePurchasingState(address beneficiary, uint256 weiAmount) internal {
+        // solhint-disable-previous-line no-empty-blocks
+    }
 
-  /**
-   * @dev Executed when a purchase has been validated and is ready to be executed. Doesn't necessarily emit/send tokens.
-   * @param beneficiary Address receiving the tokens
-   * @param tokenAmount Number of tokens to be purchased
-   */
-  function _processPurchase(
-    address beneficiary,
-    uint256 tokenAmount
-  )
-    internal
-  {
-    _deliverTokens(beneficiary, tokenAmount);
-  }
+    /**
+     * @dev Override to extend the way in which ether is converted to tokens.
+     * @param weiAmount Value in wei to be converted into tokens
+     * @return Number of tokens that can be purchased with the specified _weiAmount
+     */
+    function _getTokenAmount(uint256 weiAmount) internal view returns (uint256) {
+        return weiAmount.mul(_rate);
+    }
 
-  /**
-   * @dev Override for extensions that require an internal state to check for validity (current user contributions, etc.)
-   * @param beneficiary Address receiving the tokens
-   * @param weiAmount Value in wei involved in the purchase
-   */
-  function _updatePurchasingState(
-    address beneficiary,
-    uint256 weiAmount
-  )
-    internal
-  {
-    // optional override
-  }
+    /**
+     * @dev Determines how ETH is stored/forwarded on purchases.
+     */
+    function _forwardFunds() internal {
+        _wallet.transfer(msg.value);
+    }
 
-  /**
-   * @dev Override to extend the way in which ether is converted to tokens.
-   * @param weiAmount Value in wei to be converted into tokens
-   * @return Number of tokens that can be purchased with the specified _weiAmount
-   */
-  function _getTokenAmount(uint256 weiAmount)
-    internal view returns (uint256)
-  {
-    return weiAmount.mul(_rate);
-  }
-
-  /**
-   * @dev Determines how ETH is stored/forwarded on purchases.
-   */
-  function _forwardFunds() internal {
-    _wallet.transfer(msg.value);
-  }
+    uint256[50] private ______gap;
 }

contracts/crowdsale/distribution/FinalizableCrowdsale.sol

@@ -1,50 +1,50 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
 import "../../math/SafeMath.sol";
 import "../validation/TimedCrowdsale.sol";
 
 /**
  * @title FinalizableCrowdsale
- * @dev Extension of Crowdsale with a one-off finalization action, where one
+ * @dev Extension of TimedCrowdsale with a one-off finalization action, where one
  * can do extra work after finishing.
  */
-contract FinalizableCrowdsale is TimedCrowdsale {
-  using SafeMath for uint256;
+contract FinalizableCrowdsale is Initializable, TimedCrowdsale {
+    using SafeMath for uint256;
 
-  bool private _finalized;
+    bool private _finalized;
 
-  event CrowdsaleFinalized();
+    event CrowdsaleFinalized();
 
-  constructor() internal {
-    _finalized = false;
-  }
+    /**
+     * @return true if the crowdsale is finalized, false otherwise.
+     */
+    function finalized() public view returns (bool) {
+        return _finalized;
+    }
 
-  /**
-   * @return true if the crowdsale is finalized, false otherwise.
-   */
-  function finalized() public view returns (bool) {
-    return _finalized;
-  }
+    /**
+     * @dev Must be called after crowdsale ends, to do some extra finalization
+     * work. Calls the contract's finalization function.
+     */
+    function finalize() public {
+        require(!_finalized);
+        require(hasClosed());
 
-  /**
-   * @dev Must be called after crowdsale ends, to do some extra finalization
-   * work. Calls the contract's finalization function.
-   */
-  function finalize() public {
-    require(!_finalized);
-    require(hasClosed());
+        _finalized = true;
 
-    _finalized = true;
+        _finalization();
+        emit CrowdsaleFinalized();
+    }
 
-    _finalization();
-    emit CrowdsaleFinalized();
-  }
+    /**
+     * @dev Can be overridden to add finalization logic. The overriding function
+     * should call super._finalization() to ensure the chain of finalization is
+     * executed entirely.
+     */
+    function _finalization() internal {
+        // solhint-disable-previous-line no-empty-blocks
+    }
 
-  /**
-   * @dev Can be overridden to add finalization logic. The overriding function
-   * should call super._finalization() to ensure the chain of finalization is
-   * executed entirely.
-   */
-  function _finalization() internal {
-  }
+    uint256[50] private ______gap;
 }

contracts/crowdsale/distribution/PostDeliveryCrowdsale.sol

@@ -1,5 +1,6 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
 import "../validation/TimedCrowdsale.sol";
 import "../../math/SafeMath.sol";
 
@@ -7,44 +8,38 @@ import "../../math/SafeMath.sol";
  * @title PostDeliveryCrowdsale
  * @dev Crowdsale that locks tokens from withdrawal until it ends.
  */
-contract PostDeliveryCrowdsale is TimedCrowdsale {
-  using SafeMath for uint256;
+contract PostDeliveryCrowdsale is Initializable, TimedCrowdsale {
+    using SafeMath for uint256;
 
-  mapping(address => uint256) private _balances;
+    mapping(address => uint256) private _balances;
 
-  constructor() internal {}
+    /**
+     * @dev Withdraw tokens only after crowdsale ends.
+     * @param beneficiary Whose tokens will be withdrawn.
+     */
+    function withdrawTokens(address beneficiary) public {
+        require(hasClosed());
+        uint256 amount = _balances[beneficiary];
+        require(amount > 0);
+        _balances[beneficiary] = 0;
+        _deliverTokens(beneficiary, amount);
+    }
 
-  /**
-   * @dev Withdraw tokens only after crowdsale ends.
-   * @param beneficiary Whose tokens will be withdrawn.
-   */
-  function withdrawTokens(address beneficiary) public {
-    require(hasClosed());
-    uint256 amount = _balances[beneficiary];
-    require(amount > 0);
-    _balances[beneficiary] = 0;
-    _deliverTokens(beneficiary, amount);
-  }
+    /**
+     * @return the balance of an account.
+     */
+    function balanceOf(address account) public view returns (uint256) {
+        return _balances[account];
+    }
 
-  /**
-   * @return the balance of an account.
-   */
-  function balanceOf(address account) public view returns(uint256) {
-    return _balances[account];
-  }
-
-  /**
-   * @dev Overrides parent by storing balances instead of issuing tokens right away.
-   * @param beneficiary Token purchaser
-   * @param tokenAmount Amount of tokens purchased
-   */
-  function _processPurchase(
-    address beneficiary,
-    uint256 tokenAmount
-  )
-    internal
-  {
-    _balances[beneficiary] = _balances[beneficiary].add(tokenAmount);
-  }
+    /**
+     * @dev Overrides parent by storing balances instead of issuing tokens right away.
+     * @param beneficiary Token purchaser
+     * @param tokenAmount Amount of tokens purchased
+     */
+    function _processPurchase(address beneficiary, uint256 tokenAmount) internal {
+        _balances[beneficiary] = _balances[beneficiary].add(tokenAmount);
+    }
 
+    uint256[50] private ______gap;
 }

contracts/crowdsale/distribution/RefundableCrowdsale.sol

@@ -1,91 +1,92 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
 import "../../math/SafeMath.sol";
 import "./FinalizableCrowdsale.sol";
 import "../../payment/escrow/RefundEscrow.sol";
 
 /**
  * @title RefundableCrowdsale
- * @dev Extension of Crowdsale contract that adds a funding goal, and
- * the possibility of users getting a refund if goal is not met.
- * WARNING: note that if you allow tokens to be traded before the goal 
- * is met, then an attack is possible in which the attacker purchases 
- * tokens from the crowdsale and when they sees that the goal is 
- * unlikely to be met, they sell their tokens (possibly at a discount).
- * The attacker will be refunded when the crowdsale is finalized, and
- * the users that purchased from them will be left with worthless 
- * tokens. There are many possible ways to avoid this, like making the
- * the crowdsale inherit from PostDeliveryCrowdsale, or imposing 
- * restrictions on token trading until the crowdsale is finalized.
- * This is being discussed in 
- * https://github.com/OpenZeppelin/openzeppelin-solidity/issues/877
- * This contract will be updated when we agree on a general solution
- * for this problem.
+ * @dev Extension of FinalizableCrowdsale contract that adds a funding goal, and the possibility of users
+ * getting a refund if goal is not met.
+ *
+ * Deprecated, use RefundablePostDeliveryCrowdsale instead. Note that if you allow tokens to be traded before the goal
+ * is met, then an attack is possible in which the attacker purchases tokens from the crowdsale and when they sees that
+ * the goal is unlikely to be met, they sell their tokens (possibly at a discount). The attacker will be refunded when
+ * the crowdsale is finalized, and the users that purchased from them will be left with worthless tokens.
  */
-contract RefundableCrowdsale is FinalizableCrowdsale {
-  using SafeMath for uint256;
+contract RefundableCrowdsale is Initializable, FinalizableCrowdsale {
+    using SafeMath for uint256;
 
-  // minimum amount of funds to be raised in weis
-  uint256 private _goal;
+    // minimum amount of funds to be raised in weis
+    uint256 private _goal;
 
-  // refund escrow used to hold funds while crowdsale is running
-  RefundEscrow private _escrow;
+    // refund escrow used to hold funds while crowdsale is running
+    RefundEscrow private _escrow;
 
-  /**
-   * @dev Constructor, creates RefundEscrow.
-   * @param goal Funding goal
-   */
-  constructor(uint256 goal) internal {
-    require(goal > 0);
-    _escrow = new RefundEscrow(wallet());
-    _goal = goal;
-  }
+    /**
+     * @dev Constructor, creates RefundEscrow.
+     * @param goal Funding goal
+     */
+    function initialize(uint256 goal) public initializer {
+        // FinalizableCrowdsale depends on TimedCrowdsale
+        assert(TimedCrowdsale._hasBeenInitialized());
 
-  /**
-   * @return minimum amount of funds to be raised in wei.
-   */
-  function goal() public view returns(uint256) {
-    return _goal;
-  }
-
-  /**
-   * @dev Investors can claim refunds here if crowdsale is unsuccessful
-   * @param beneficiary Whose refund will be claimed.
-   */
-  function claimRefund(address beneficiary) public {
-    require(finalized());
-    require(!goalReached());
-
-    _escrow.withdraw(beneficiary);
-  }
-
-  /**
-   * @dev Checks whether funding goal was reached.
-   * @return Whether funding goal was reached
-   */
-  function goalReached() public view returns (bool) {
-    return weiRaised() >= _goal;
-  }
-
-  /**
-   * @dev escrow finalization task, called when finalize() is called
-   */
-  function _finalization() internal {
-    if (goalReached()) {
-      _escrow.close();
-      _escrow.beneficiaryWithdraw();
-    } else {
-      _escrow.enableRefunds();
+        require(goal > 0);
+        // conditional added to make initializer idempotent in case of diamond inheritance
+        if (address(_escrow) == address(0)) {
+            _escrow = new RefundEscrow();
+            _escrow.initialize(wallet(), address(this));
+        }
+        _goal = goal;
     }
 
-    super._finalization();
-  }
+    /**
+     * @return minimum amount of funds to be raised in wei.
+     */
+    function goal() public view returns (uint256) {
+        return _goal;
+    }
 
-  /**
-   * @dev Overrides Crowdsale fund forwarding, sending funds to escrow.
-   */
-  function _forwardFunds() internal {
-    _escrow.deposit.value(msg.value)(msg.sender);
-  }
+    /**
+     * @dev Investors can claim refunds here if crowdsale is unsuccessful
+     * @param refundee Whose refund will be claimed.
+     */
+    function claimRefund(address payable refundee) public {
+        require(finalized());
+        require(!goalReached());
 
+        _escrow.withdraw(refundee);
+    }
+
+    /**
+     * @dev Checks whether funding goal was reached.
+     * @return Whether funding goal was reached
+     */
+    function goalReached() public view returns (bool) {
+        return weiRaised() >= _goal;
+    }
+
+    /**
+     * @dev escrow finalization task, called when finalize() is called
+     */
+    function _finalization() internal {
+        if (goalReached()) {
+            _escrow.close();
+            _escrow.beneficiaryWithdraw();
+        } else {
+            _escrow.enableRefunds();
+        }
+
+        super._finalization();
+    }
+
+    /**
+     * @dev Overrides Crowdsale fund forwarding, sending funds to escrow.
+     */
+    function _forwardFunds() internal {
+        _escrow.deposit.value(msg.value)(msg.sender);
+    }
+
+    uint256[50] private ______gap;
 }

contracts/crowdsale/distribution/RefundablePostDeliveryCrowdsale.sol

@@ -0,0 +1,23 @@
+pragma solidity ^0.5.2;
+
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
+
+import "./RefundableCrowdsale.sol";
+import "./PostDeliveryCrowdsale.sol";
+
+/**
+ * @title RefundablePostDeliveryCrowdsale
+ * @dev Extension of RefundableCrowdsale contract that only delivers the tokens
+ * once the crowdsale has closed and the goal met, preventing refunds to be issued
+ * to token holders.
+ */
+contract RefundablePostDeliveryCrowdsale is Initializable, RefundableCrowdsale, PostDeliveryCrowdsale {
+    function withdrawTokens(address beneficiary) public {
+        require(finalized());
+        require(goalReached());
+
+        super.withdrawTokens(beneficiary);
+    }
+
+    uint256[50] private ______gap;
+}

contracts/crowdsale/emission/AllowanceCrowdsale.sol

@@ -1,5 +1,6 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
 import "../Crowdsale.sol";
 import "../../token/ERC20/IERC20.sol";
 import "../../token/ERC20/SafeERC20.sol";
@@ -10,50 +11,46 @@ import "../../math/Math.sol";
  * @title AllowanceCrowdsale
  * @dev Extension of Crowdsale where tokens are held by a wallet, which approves an allowance to the crowdsale.
  */
-contract AllowanceCrowdsale is Crowdsale {
-  using SafeMath for uint256;
-  using SafeERC20 for IERC20;
+contract AllowanceCrowdsale is Initializable, Crowdsale {
+    using SafeMath for uint256;
+    using SafeERC20 for IERC20;
 
-  address private _tokenWallet;
+    address private _tokenWallet;
 
-  /**
-   * @dev Constructor, takes token wallet address.
-   * @param tokenWallet Address holding the tokens, which has approved allowance to the crowdsale
-   */
-  constructor(address tokenWallet) internal {
-    require(tokenWallet != address(0));
-    _tokenWallet = tokenWallet;
-  }
+    /**
+     * @dev Constructor, takes token wallet address.
+     * @param tokenWallet Address holding the tokens, which has approved allowance to the crowdsale
+     */
+    function initialize(address tokenWallet) public initializer {
+        assert(Crowdsale._hasBeenInitialized());
 
-  /**
-   * @return the address of the wallet that will hold the tokens.
-   */
-  function tokenWallet() public view returns(address) {
-    return _tokenWallet;
-  }
+        require(tokenWallet != address(0));
+        _tokenWallet = tokenWallet;
+    }
 
-  /**
-   * @dev Checks the amount of tokens left in the allowance.
-   * @return Amount of tokens left in the allowance
-   */
-  function remainingTokens() public view returns (uint256) {
-    return Math.min(
-      token().balanceOf(_tokenWallet),
-      token().allowance(_tokenWallet, this)
-    );
-  }
+    /**
+     * @return the address of the wallet that will hold the tokens.
+     */
+    function tokenWallet() public view returns (address) {
+        return _tokenWallet;
+    }
 
-  /**
-   * @dev Overrides parent behavior by transferring tokens from wallet.
-   * @param beneficiary Token purchaser
-   * @param tokenAmount Amount of tokens purchased
-   */
-  function _deliverTokens(
-    address beneficiary,
-    uint256 tokenAmount
-  )
-    internal
-  {
-    token().safeTransferFrom(_tokenWallet, beneficiary, tokenAmount);
-  }
+    /**
+     * @dev Checks the amount of tokens left in the allowance.
+     * @return Amount of tokens left in the allowance
+     */
+    function remainingTokens() public view returns (uint256) {
+        return Math.min(token().balanceOf(_tokenWallet), token().allowance(_tokenWallet, address(this)));
+    }
+
+    /**
+     * @dev Overrides parent behavior by transferring tokens from wallet.
+     * @param beneficiary Token purchaser
+     * @param tokenAmount Amount of tokens purchased
+     */
+    function _deliverTokens(address beneficiary, uint256 tokenAmount) internal {
+        token().safeTransferFrom(_tokenWallet, beneficiary, tokenAmount);
+    }
+
+    uint256[50] private ______gap;
 }

contracts/crowdsale/emission/MintedCrowdsale.sol

@@ -1,5 +1,6 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
 import "../Crowdsale.sol";
 import "../../token/ERC20/ERC20Mintable.sol";
 
@@ -8,22 +9,16 @@ import "../../token/ERC20/ERC20Mintable.sol";
  * @dev Extension of Crowdsale contract whose tokens are minted in each purchase.
  * Token ownership should be transferred to MintedCrowdsale for minting.
  */
-contract MintedCrowdsale is Crowdsale {
-  constructor() internal {}
+contract MintedCrowdsale is Initializable, Crowdsale {
+    /**
+     * @dev Overrides delivery by minting tokens upon purchase.
+     * @param beneficiary Token purchaser
+     * @param tokenAmount Number of tokens to be minted
+     */
+    function _deliverTokens(address beneficiary, uint256 tokenAmount) internal {
+        // Potentially dangerous assumption about the type of the token.
+        require(ERC20Mintable(address(token())).mint(beneficiary, tokenAmount));
+    }
 
-  /**
-   * @dev Overrides delivery by minting tokens upon purchase.
-   * @param beneficiary Token purchaser
-   * @param tokenAmount Number of tokens to be minted
-   */
-  function _deliverTokens(
-    address beneficiary,
-    uint256 tokenAmount
-  )
-    internal
-  {
-    // Potentially dangerous assumption about the type of the token.
-    require(
-      ERC20Mintable(address(token())).mint(beneficiary, tokenAmount));
-  }
+    uint256[50] private ______gap;
 }

contracts/crowdsale/price/IncreasingPriceCrowdsale.sol

@@ -1,5 +1,6 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
 import "../validation/TimedCrowdsale.sol";
 import "../../math/SafeMath.sol";
 
@@ -9,73 +10,74 @@ import "../../math/SafeMath.sol";
  * Note that what should be provided to the constructor is the initial and final _rates_, that is,
  * the amount of tokens per wei contributed. Thus, the initial rate must be greater than the final rate.
  */
-contract IncreasingPriceCrowdsale is TimedCrowdsale {
-  using SafeMath for uint256;
+contract IncreasingPriceCrowdsale is Initializable, TimedCrowdsale {
+    using SafeMath for uint256;
 
-  uint256 private _initialRate;
-  uint256 private _finalRate;
+    uint256 private _initialRate;
+    uint256 private _finalRate;
 
-  /**
-   * @dev Constructor, takes initial and final rates of tokens received per wei contributed.
-   * @param initialRate Number of tokens a buyer gets per wei at the start of the crowdsale
-   * @param finalRate Number of tokens a buyer gets per wei at the end of the crowdsale
-   */
-  constructor(uint256 initialRate, uint256 finalRate) internal {
-    require(finalRate > 0);
-    require(initialRate > finalRate);
-    _initialRate = initialRate;
-    _finalRate = finalRate;
-  }
+    /**
+     * @dev Constructor, takes initial and final rates of tokens received per wei contributed.
+     * @param initialRate Number of tokens a buyer gets per wei at the start of the crowdsale
+     * @param finalRate Number of tokens a buyer gets per wei at the end of the crowdsale
+     */
+    function initialize(uint256 initialRate, uint256 finalRate) public initializer {
+        assert(TimedCrowdsale._hasBeenInitialized());
 
-  /**
-   * The base rate function is overridden to revert, since this crowdsale doens't use it, and
-   * all calls to it are a mistake.
-   */
-  function rate() public view returns(uint256) {
-    revert();
-  }
-
-  /**
-   * @return the initial rate of the crowdsale.
-   */
-  function initialRate() public view returns(uint256) {
-    return _initialRate;
-  }
-
-  /**
-   * @return the final rate of the crowdsale.
-   */
-  function finalRate() public view returns (uint256) {
-    return _finalRate;
-  }
-
-  /**
-   * @dev Returns the rate of tokens per wei at the present time.
-   * Note that, as price _increases_ with time, the rate _decreases_.
-   * @return The number of tokens a buyer gets per wei at a given time
-   */
-  function getCurrentRate() public view returns (uint256) {
-    if (!isOpen()) {
-      return 0;
+        require(finalRate > 0);
+        require(initialRate > finalRate);
+        _initialRate = initialRate;
+        _finalRate = finalRate;
     }
 
-    // solium-disable-next-line security/no-block-members
-    uint256 elapsedTime = block.timestamp.sub(openingTime());
-    uint256 timeRange = closingTime().sub(openingTime());
-    uint256 rateRange = _initialRate.sub(_finalRate);
-    return _initialRate.sub(elapsedTime.mul(rateRange).div(timeRange));
-  }
+    /**
+     * The base rate function is overridden to revert, since this crowdsale doesn't use it, and
+     * all calls to it are a mistake.
+     */
+    function rate() public view returns (uint256) {
+        revert();
+    }
 
-  /**
-   * @dev Overrides parent method taking into account variable rate.
-   * @param weiAmount The value in wei to be converted into tokens
-   * @return The number of tokens _weiAmount wei will buy at present time
-   */
-  function _getTokenAmount(uint256 weiAmount)
-    internal view returns (uint256)
-  {
-    uint256 currentRate = getCurrentRate();
-    return currentRate.mul(weiAmount);
-  }
+    /**
+     * @return the initial rate of the crowdsale.
+     */
+    function initialRate() public view returns (uint256) {
+        return _initialRate;
+    }
 
+    /**
+     * @return the final rate of the crowdsale.
+     */
+    function finalRate() public view returns (uint256) {
+        return _finalRate;
+    }
+
+    /**
+     * @dev Returns the rate of tokens per wei at the present time.
+     * Note that, as price _increases_ with time, the rate _decreases_.
+     * @return The number of tokens a buyer gets per wei at a given time
+     */
+    function getCurrentRate() public view returns (uint256) {
+        if (!isOpen()) {
+            return 0;
+        }
+
+        // solhint-disable-next-line not-rely-on-time
+        uint256 elapsedTime = block.timestamp.sub(openingTime());
+        uint256 timeRange = closingTime().sub(openingTime());
+        uint256 rateRange = _initialRate.sub(_finalRate);
+        return _initialRate.sub(elapsedTime.mul(rateRange).div(timeRange));
+    }
+
+    /**
+     * @dev Overrides parent method taking into account variable rate.
+     * @param weiAmount The value in wei to be converted into tokens
+     * @return The number of tokens _weiAmount wei will buy at present time
+     */
+    function _getTokenAmount(uint256 weiAmount) internal view returns (uint256) {
+        uint256 currentRate = getCurrentRate();
+        return currentRate.mul(weiAmount);
+    }
+
+    uint256[50] private ______gap;
 }

contracts/crowdsale/validation/CappedCrowdsale.sol

@@ -1,5 +1,6 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
 import "../../math/SafeMath.sol";
 import "../Crowdsale.sol";
 
@@ -7,49 +8,46 @@ import "../Crowdsale.sol";
  * @title CappedCrowdsale
  * @dev Crowdsale with a limit for total contributions.
  */
-contract CappedCrowdsale is Crowdsale {
-  using SafeMath for uint256;
+contract CappedCrowdsale is Initializable, Crowdsale {
+    using SafeMath for uint256;
 
-  uint256 private _cap;
+    uint256 private _cap;
 
-  /**
-   * @dev Constructor, takes maximum amount of wei accepted in the crowdsale.
-   * @param cap Max amount of wei to be contributed
-   */
-  constructor(uint256 cap) internal {
-    require(cap > 0);
-    _cap = cap;
-  }
+    /**
+     * @dev Constructor, takes maximum amount of wei accepted in the crowdsale.
+     * @param cap Max amount of wei to be contributed
+     */
+    function initialize(uint256 cap) public initializer {
+        assert(Crowdsale._hasBeenInitialized());
 
-  /**
-   * @return the cap of the crowdsale.
-   */
-  function cap() public view returns(uint256) {
-    return _cap;
-  }
+        require(cap > 0);
+        _cap = cap;
+    }
 
-  /**
-   * @dev Checks whether the cap has been reached.
-   * @return Whether the cap was reached
-   */
-  function capReached() public view returns (bool) {
-    return weiRaised() >= _cap;
-  }
+    /**
+     * @return the cap of the crowdsale.
+     */
+    function cap() public view returns (uint256) {
+        return _cap;
+    }
 
-  /**
-   * @dev Extend parent behavior requiring purchase to respect the funding cap.
-   * @param beneficiary Token purchaser
-   * @param weiAmount Amount of wei contributed
-   */
-  function _preValidatePurchase(
-    address beneficiary,
-    uint256 weiAmount
-  )
-    internal
-    view
-  {
-    super._preValidatePurchase(beneficiary, weiAmount);
-    require(weiRaised().add(weiAmount) <= _cap);
-  }
+    /**
+     * @dev Checks whether the cap has been reached.
+     * @return Whether the cap was reached
+     */
+    function capReached() public view returns (bool) {
+        return weiRaised() >= _cap;
+    }
 
+    /**
+     * @dev Extend parent behavior requiring purchase to respect the funding cap.
+     * @param beneficiary Token purchaser
+     * @param weiAmount Amount of wei contributed
+     */
+    function _preValidatePurchase(address beneficiary, uint256 weiAmount) internal view {
+        super._preValidatePurchase(beneficiary, weiAmount);
+        require(weiRaised().add(weiAmount) <= _cap);
+    }
+
+    uint256[50] private ______gap;
 }

contracts/crowdsale/validation/IndividuallyCappedCrowdsale.sol

@@ -1,5 +1,6 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
 import "../../math/SafeMath.sol";
 import "../Crowdsale.sol";
 import "../../access/roles/CapperRole.sol";
@@ -8,74 +9,64 @@ import "../../access/roles/CapperRole.sol";
  * @title IndividuallyCappedCrowdsale
  * @dev Crowdsale with per-beneficiary caps.
  */
-contract IndividuallyCappedCrowdsale is Crowdsale, CapperRole {
-  using SafeMath for uint256;
+contract IndividuallyCappedCrowdsale is Initializable, Crowdsale, CapperRole {
+    using SafeMath for uint256;
 
-  mapping(address => uint256) private _contributions;
-  mapping(address => uint256) private _caps;
+    mapping(address => uint256) private _contributions;
+    mapping(address => uint256) private _caps;
 
-  constructor() internal {}
+    function initialize(address sender) public initializer {
+        assert(Crowdsale._hasBeenInitialized());
 
-  /**
-   * @dev Sets a specific beneficiary's maximum contribution.
-   * @param beneficiary Address to be capped
-   * @param cap Wei limit for individual contribution
-   */
-  function setCap(address beneficiary, uint256 cap) external onlyCapper {
-    _caps[beneficiary] = cap;
-  }
+        CapperRole.initialize(sender);
+    }
 
-  /**
-   * @dev Returns the cap of a specific beneficiary.
-   * @param beneficiary Address whose cap is to be checked
-   * @return Current cap for individual beneficiary
-   */
-  function getCap(address beneficiary) public view returns (uint256) {
-    return _caps[beneficiary];
-  }
+    /**
+     * @dev Sets a specific beneficiary's maximum contribution.
+     * @param beneficiary Address to be capped
+     * @param cap Wei limit for individual contribution
+     */
+    function setCap(address beneficiary, uint256 cap) external onlyCapper {
+        _caps[beneficiary] = cap;
+    }
 
-  /**
-   * @dev Returns the amount contributed so far by a specific beneficiary.
-   * @param beneficiary Address of contributor
-   * @return Beneficiary contribution so far
-   */
-  function getContribution(address beneficiary)
-    public view returns (uint256)
-  {
-    return _contributions[beneficiary];
-  }
+    /**
+     * @dev Returns the cap of a specific beneficiary.
+     * @param beneficiary Address whose cap is to be checked
+     * @return Current cap for individual beneficiary
+     */
+    function getCap(address beneficiary) public view returns (uint256) {
+        return _caps[beneficiary];
+    }
 
-  /**
-   * @dev Extend parent behavior requiring purchase to respect the beneficiary's funding cap.
-   * @param beneficiary Token purchaser
-   * @param weiAmount Amount of wei contributed
-   */
-  function _preValidatePurchase(
-    address beneficiary,
-    uint256 weiAmount
-  )
-    internal
-    view
-  {
-    super._preValidatePurchase(beneficiary, weiAmount);
-    require(
-      _contributions[beneficiary].add(weiAmount) <= _caps[beneficiary]);
-  }
+    /**
+     * @dev Returns the amount contributed so far by a specific beneficiary.
+     * @param beneficiary Address of contributor
+     * @return Beneficiary contribution so far
+     */
+    function getContribution(address beneficiary) public view returns (uint256) {
+        return _contributions[beneficiary];
+    }
 
-  /**
-   * @dev Extend parent behavior to update beneficiary contributions
-   * @param beneficiary Token purchaser
-   * @param weiAmount Amount of wei contributed
-   */
-  function _updatePurchasingState(
-    address beneficiary,
-    uint256 weiAmount
-  )
-    internal
-  {
-    super._updatePurchasingState(beneficiary, weiAmount);
-    _contributions[beneficiary] = _contributions[beneficiary].add(
-      weiAmount);
-  }
+    /**
+     * @dev Extend parent behavior requiring purchase to respect the beneficiary's funding cap.
+     * @param beneficiary Token purchaser
+     * @param weiAmount Amount of wei contributed
+     */
+    function _preValidatePurchase(address beneficiary, uint256 weiAmount) internal view {
+        super._preValidatePurchase(beneficiary, weiAmount);
+        require(_contributions[beneficiary].add(weiAmount) <= _caps[beneficiary]);
+    }
 
+    /**
+     * @dev Extend parent behavior to update beneficiary contributions
+     * @param beneficiary Token purchaser
+     * @param weiAmount Amount of wei contributed
+     */
+    function _updatePurchasingState(address beneficiary, uint256 weiAmount) internal {
+        super._updatePurchasingState(beneficiary, weiAmount);
+        _contributions[beneficiary] = _contributions[beneficiary].add(weiAmount);
+    }
+
+    uint256[50] private ______gap;
 }

contracts/crowdsale/validation/PausableCrowdsale.sol

@@ -0,0 +1,31 @@
+pragma solidity ^0.5.2;
+
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
+
+import "../Crowdsale.sol";
+import "../../lifecycle/Pausable.sol";
+
+/**
+ * @title PausableCrowdsale
+ * @dev Extension of Crowdsale contract where purchases can be paused and unpaused by the pauser role.
+ */
+contract PausableCrowdsale is Initializable, Crowdsale, Pausable {
+    function initialize(address sender) public initializer {
+        assert(Crowdsale._hasBeenInitialized());
+
+        Pausable.initialize(sender);
+    }
+
+    /**
+     * @dev Validation of an incoming purchase. Use require statements to revert state when conditions are not met.
+     * Use super to concatenate validations.
+     * Adds the validation that the crowdsale must not be paused.
+     * @param _beneficiary Address performing the token purchase
+     * @param _weiAmount Value in wei involved in the purchase
+     */
+    function _preValidatePurchase(address _beneficiary, uint256 _weiAmount) internal view whenNotPaused {
+        return super._preValidatePurchase(_beneficiary, _weiAmount);
+    }
+
+    uint256[50] private ______gap;
+}

contracts/crowdsale/validation/TimedCrowdsale.sol

@@ -1,5 +1,6 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
 import "../../math/SafeMath.sol";
 import "../Crowdsale.sol";
 
@@ -7,79 +8,98 @@ import "../Crowdsale.sol";
  * @title TimedCrowdsale
  * @dev Crowdsale accepting contributions only within a time frame.
  */
-contract TimedCrowdsale is Crowdsale {
-  using SafeMath for uint256;
+contract TimedCrowdsale is Initializable, Crowdsale {
+    using SafeMath for uint256;
 
-  uint256 private _openingTime;
-  uint256 private _closingTime;
+    uint256 private _openingTime;
+    uint256 private _closingTime;
 
-  /**
-   * @dev Reverts if not in crowdsale time range.
-   */
-  modifier onlyWhileOpen {
-    require(isOpen());
-    _;
-  }
+    /**
+     * Event for crowdsale extending
+     * @param newClosingTime new closing time
+     * @param prevClosingTime old closing time
+     */
+    event TimedCrowdsaleExtended(uint256 prevClosingTime, uint256 newClosingTime);
 
-  /**
-   * @dev Constructor, takes crowdsale opening and closing times.
-   * @param openingTime Crowdsale opening time
-   * @param closingTime Crowdsale closing time
-   */
-  constructor(uint256 openingTime, uint256 closingTime) internal {
-    // solium-disable-next-line security/no-block-members
-    require(openingTime >= block.timestamp);
-    require(closingTime > openingTime);
+    /**
+     * @dev Reverts if not in crowdsale time range.
+     */
+    modifier onlyWhileOpen {
+        require(isOpen());
+        _;
+    }
 
-    _openingTime = openingTime;
-    _closingTime = closingTime;
-  }
+    /**
+     * @dev Constructor, takes crowdsale opening and closing times.
+     * @param openingTime Crowdsale opening time
+     * @param closingTime Crowdsale closing time
+     */
+    function initialize(uint256 openingTime, uint256 closingTime) public initializer {
+        assert(Crowdsale._hasBeenInitialized());
 
-  /**
-   * @return the crowdsale opening time.
-   */
-  function openingTime() public view returns(uint256) {
-    return _openingTime;
-  }
+        // solhint-disable-next-line not-rely-on-time
+        require(openingTime >= block.timestamp);
+        require(closingTime > openingTime);
 
-  /**
-   * @return the crowdsale closing time.
-   */
-  function closingTime() public view returns(uint256) {
-    return _closingTime;
-  }
+        _openingTime = openingTime;
+        _closingTime = closingTime;
+    }
 
-  /**
-   * @return true if the crowdsale is open, false otherwise.
-   */
-  function isOpen() public view returns (bool) {
-    // solium-disable-next-line security/no-block-members
-    return block.timestamp >= _openingTime && block.timestamp <= _closingTime;
-  }
+    /**
+     * @return the crowdsale opening time.
+     */
+    function openingTime() public view returns (uint256) {
+        return _openingTime;
+    }
 
-  /**
-   * @dev Checks whether the period in which the crowdsale is open has already elapsed.
-   * @return Whether crowdsale period has elapsed
-   */
-  function hasClosed() public view returns (bool) {
-    // solium-disable-next-line security/no-block-members
-    return block.timestamp > _closingTime;
-  }
+    /**
+     * @return the crowdsale closing time.
+     */
+    function closingTime() public view returns (uint256) {
+        return _closingTime;
+    }
 
-  /**
-   * @dev Extend parent behavior requiring to be within contributing period
-   * @param beneficiary Token purchaser
-   * @param weiAmount Amount of wei contributed
-   */
-  function _preValidatePurchase(
-    address beneficiary,
-    uint256 weiAmount
-  )
-    internal
-    onlyWhileOpen
-    view
-  {
-    super._preValidatePurchase(beneficiary, weiAmount);
-  }
+    /**
+     * @return true if the crowdsale is open, false otherwise.
+     */
+    function isOpen() public view returns (bool) {
+        // solhint-disable-next-line not-rely-on-time
+        return block.timestamp >= _openingTime && block.timestamp <= _closingTime;
+    }
 
+    /**
+     * @dev Checks whether the period in which the crowdsale is open has already elapsed.
+     * @return Whether crowdsale period has elapsed
+     */
+    function hasClosed() public view returns (bool) {
+        // solhint-disable-next-line not-rely-on-time
+        return block.timestamp > _closingTime;
+    }
+
+    function _hasBeenInitialized() internal view returns (bool) {
+        return ((_openingTime > 0) && (_closingTime > 0));
+    }
+
+    /**
+     * @dev Extend parent behavior requiring to be within contributing period
+     * @param beneficiary Token purchaser
+     * @param weiAmount Amount of wei contributed
+     */
+    function _preValidatePurchase(address beneficiary, uint256 weiAmount) internal onlyWhileOpen view {
+        super._preValidatePurchase(beneficiary, weiAmount);
+    }
+
+    /**
+     * @dev Extend crowdsale
+     * @param newClosingTime Crowdsale closing time
+     */
+    function _extendTime(uint256 newClosingTime) internal {
+        require(!hasClosed());
+        require(newClosingTime > _closingTime);
+
+        emit TimedCrowdsaleExtended(_closingTime, newClosingTime);
+        _closingTime = newClosingTime;
+    }
+
+    uint256[50] private ______gap;
 }

contracts/crowdsale/validation/WhitelistCrowdsale.sol

@@ -0,0 +1,29 @@
+pragma solidity ^0.5.2;
+import "../Crowdsale.sol";
+import "../../access/roles/WhitelistedRole.sol";
+
+
+/**
+ * @title WhitelistCrowdsale
+ * @dev Crowdsale in which only whitelisted users can contribute.
+ */
+contract WhitelistCrowdsale is Initializable, WhitelistedRole, Crowdsale {
+    function initialize(address sender) public initializer {
+        WhitelistedRole.initialize(sender);
+
+        assert(Crowdsale._hasBeenInitialized());
+    }
+
+    /**
+     * @dev Extend parent behavior requiring beneficiary to be whitelisted. Note that no
+     * restriction is imposed on the account sending the transaction.
+     * @param _beneficiary Token beneficiary
+     * @param _weiAmount Amount of wei contributed
+     */
+    function _preValidatePurchase(address _beneficiary, uint256 _weiAmount) internal view {
+        require(isWhitelisted(_beneficiary));
+        super._preValidatePurchase(_beneficiary, _weiAmount);
+    }
+
+    uint256[50] private ______gap;
+}

contracts/cryptography/ECDSA.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
 /**
  * @title Elliptic curve signature operations
@@ -8,64 +8,60 @@ pragma solidity ^0.4.24;
  */
 
 library ECDSA {
+    /**
+     * @dev Recover signer address from a message by using their signature
+     * @param hash bytes32 message, the hash is the signed message. What is recovered is the signer address.
+     * @param signature bytes signature, the signature is generated using web3.eth.sign()
+     */
+    function recover(bytes32 hash, bytes memory signature) internal pure returns (address) {
+        // Check the signature length
+        if (signature.length != 65) {
+            return (address(0));
+        }
 
-  /**
-   * @dev Recover signer address from a message by using their signature
-   * @param hash bytes32 message, the hash is the signed message. What is recovered is the signer address.
-   * @param signature bytes signature, the signature is generated using web3.eth.sign()
-   */
-  function recover(bytes32 hash, bytes signature)
-    internal
-    pure
-    returns (address)
-  {
-    bytes32 r;
-    bytes32 s;
-    uint8 v;
+        // Divide the signature in r, s and v variables
+        bytes32 r;
+        bytes32 s;
+        uint8 v;
 
-    // Check the signature length
-    if (signature.length != 65) {
-      return (address(0));
+        // ecrecover takes the signature parameters, and the only way to get them
+        // currently is to use assembly.
+        // solhint-disable-next-line no-inline-assembly
+        assembly {
+            r := mload(add(signature, 0x20))
+            s := mload(add(signature, 0x40))
+            v := byte(0, mload(add(signature, 0x60)))
+        }
+
+        // EIP-2 still allows signature malleability for ecrecover(). Remove this possibility and make the signature
+        // unique. Appendix F in the Ethereum Yellow paper (https://ethereum.github.io/yellowpaper/paper.pdf), defines
+        // the valid range for s in (281): 0 < s < secp256k1n ÷ 2 + 1, and for v in (282): v ∈ {27, 28}. Most
+        // signatures from current libraries generate a unique signature with an s-value in the lower half order.
+        //
+        // If your library generates malleable signatures, such as s-values in the upper range, calculate a new s-value
+        // with 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141 - s1 and flip v from 27 to 28 or
+        // vice versa. If your library also generates signatures with 0/1 for v instead 27/28, add 27 to v to accept
+        // these malleable signatures as well.
+        if (uint256(s) > 0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF5D576E7357A4501DDFE92F46681B20A0) {
+            return address(0);
+        }
+
+        if (v != 27 && v != 28) {
+            return address(0);
+        }
+
+        // If the signature is valid (and not malleable), return the signer address
+        return ecrecover(hash, v, r, s);
     }
 
-    // Divide the signature in r, s and v variables
-    // ecrecover takes the signature parameters, and the only way to get them
-    // currently is to use assembly.
-    // solium-disable-next-line security/no-inline-assembly
-    assembly {
-      r := mload(add(signature, 0x20))
-      s := mload(add(signature, 0x40))
-      v := byte(0, mload(add(signature, 0x60)))
+    /**
+     * toEthSignedMessageHash
+     * @dev prefix a bytes32 value with "\x19Ethereum Signed Message:"
+     * and hash the result
+     */
+    function toEthSignedMessageHash(bytes32 hash) internal pure returns (bytes32) {
+        // 32 is the length in bytes of hash,
+        // enforced by the type signature above
+        return keccak256(abi.encodePacked("\x19Ethereum Signed Message:\n32", hash));
     }
-
-    // Version of signature should be 27 or 28, but 0 and 1 are also possible versions
-    if (v < 27) {
-      v += 27;
-    }
-
-    // If the version is correct return the signer address
-    if (v != 27 && v != 28) {
-      return (address(0));
-    } else {
-      // solium-disable-next-line arg-overflow
-      return ecrecover(hash, v, r, s);
-    }
-  }
-
-  /**
-   * toEthSignedMessageHash
-   * @dev prefix a bytes32 value with "\x19Ethereum Signed Message:"
-   * and hash the result
-   */
-  function toEthSignedMessageHash(bytes32 hash)
-    internal
-    pure
-    returns (bytes32)
-  {
-    // 32 is the length in bytes of hash,
-    // enforced by the type signature above
-    return keccak256(
-      abi.encodePacked("\x19Ethereum Signed Message:\n32", hash)
-    );
-  }
 }

contracts/cryptography/MerkleProof.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
 /**
  * @title MerkleProof
@@ -6,37 +6,29 @@ pragma solidity ^0.4.24;
  * https://github.com/ameensol/merkle-tree-solidity/blob/master/src/MerkleProof.sol
  */
 library MerkleProof {
-  /**
-   * @dev Verifies a Merkle proof proving the existence of a leaf in a Merkle tree. Assumes that each pair of leaves
-   * and each pair of pre-images are sorted.
-   * @param proof Merkle proof containing sibling hashes on the branch from the leaf to the root of the Merkle tree
-   * @param root Merkle root
-   * @param leaf Leaf of Merkle tree
-   */
-  function verify(
-    bytes32[] proof,
-    bytes32 root,
-    bytes32 leaf
-  )
-    internal
-    pure
-    returns (bool)
-  {
-    bytes32 computedHash = leaf;
+    /**
+     * @dev Verifies a Merkle proof proving the existence of a leaf in a Merkle tree. Assumes that each pair of leaves
+     * and each pair of pre-images are sorted.
+     * @param proof Merkle proof containing sibling hashes on the branch from the leaf to the root of the Merkle tree
+     * @param root Merkle root
+     * @param leaf Leaf of Merkle tree
+     */
+    function verify(bytes32[] memory proof, bytes32 root, bytes32 leaf) internal pure returns (bool) {
+        bytes32 computedHash = leaf;
 
-    for (uint256 i = 0; i < proof.length; i++) {
-      bytes32 proofElement = proof[i];
+        for (uint256 i = 0; i < proof.length; i++) {
+            bytes32 proofElement = proof[i];
 
-      if (computedHash < proofElement) {
-        // Hash(current computed hash + current element of the proof)
-        computedHash = keccak256(abi.encodePacked(computedHash, proofElement));
-      } else {
-        // Hash(current element of the proof + current computed hash)
-        computedHash = keccak256(abi.encodePacked(proofElement, computedHash));
-      }
+            if (computedHash < proofElement) {
+                // Hash(current computed hash + current element of the proof)
+                computedHash = keccak256(abi.encodePacked(computedHash, proofElement));
+            } else {
+                // Hash(current element of the proof + current computed hash)
+                computedHash = keccak256(abi.encodePacked(proofElement, computedHash));
+            }
+        }
+
+        // Check if the computed hash (root) is equal to the provided root
+        return computedHash == root;
     }
-
-    // Check if the computed hash (root) is equal to the provided root
-    return computedHash == root;
-  }
 }

contracts/drafts/Counter.sol

@@ -1,28 +0,0 @@
-pragma solidity ^0.4.24;
-
-/**
- * @title Counter
- * @author Matt Condon (@shrugs)
- * @dev Provides an incrementing uint256 id acquired by the `Counter#next` getter.
- * Use this for issuing ERC721 ids or keeping track of request ids, anything you want, really.
- *
- * Include with `using Counter for Counter.Counter;`
- * @notice Does not allow an Id of 0, which is popularly used to signify a null state in solidity.
- * Does not protect from overflows, but if you have 2^256 ids, you have other problems.
- * (But actually, it's generally impossible to increment a counter this many times, energy wise
- * so it's not something you have to worry about.)
- */
-library Counter {
-
-  struct Counter {
-    uint256 current; // default: 0
-  }
-
-  function next(Counter storage index)
-    internal
-    returns (uint256)
-  {
-    index.current += 1;
-    return index.current;
-  }
-}

contracts/drafts/Counters.sol

@@ -0,0 +1,37 @@
+pragma solidity ^0.5.2;
+
+import "../math/SafeMath.sol";
+
+/**
+ * @title Counters
+ * @author Matt Condon (@shrugs)
+ * @dev Provides counters that can only be incremented or decremented by one. This can be used e.g. to track the number
+ * of elements in a mapping, issuing ERC721 ids, or counting request ids
+ *
+ * Include with `using Counters for Counters.Counter;`
+ * Since it is not possible to overflow a 256 bit integer with increments of one, `increment` can skip the SafeMath
+ * overflow check, thereby saving gas. This does assume however correct usage, in that the underlying `_value` is never
+ * directly accessed.
+ */
+library Counters {
+    using SafeMath for uint256;
+
+    struct Counter {
+        // This variable should never be directly accessed by users of the library: interactions must be restricted to
+        // the library's function. As of Solidity v0.5.2, this cannot be enforced, though there is a proposal to add
+        // this feature: see https://github.com/ethereum/solidity/issues/4637
+        uint256 _value; // default: 0
+    }
+
+    function current(Counter storage counter) internal view returns (uint256) {
+        return counter._value;
+    }
+
+    function increment(Counter storage counter) internal {
+        counter._value += 1;
+    }
+
+    function decrement(Counter storage counter) internal {
+        counter._value = counter._value.sub(1);
+    }
+}

contracts/drafts/ERC1046/ERC20Metadata.sol

@@ -0,0 +1,27 @@
+pragma solidity ^0.5.2;
+
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
+import "../../token/ERC20/IERC20.sol";
+
+/**
+ * @title ERC-1047 Token Metadata
+ * @dev See https://eips.ethereum.org/EIPS/eip-1046
+ * @dev tokenURI must respond with a URI that implements https://eips.ethereum.org/EIPS/eip-1047
+ */
+contract ERC20Metadata is Initializable {
+    string private _tokenURI;
+
+    function initialize(string memory tokenURI_) public {
+        _setTokenURI(tokenURI_);
+    }
+
+    function tokenURI() external view returns (string memory) {
+        return _tokenURI;
+    }
+
+    function _setTokenURI(string memory tokenURI_) internal {
+        _tokenURI = tokenURI_;
+    }
+
+    uint256[50] private ______gap;
+}

contracts/drafts/ERC1046/TokenMetadata.sol

@@ -1,27 +0,0 @@
-pragma solidity ^0.4.24;
-
-import "../../token/ERC20/IERC20.sol";
-
-/**
- * @title ERC-1047 Token Metadata
- * @dev See https://eips.ethereum.org/EIPS/eip-1046
- * @dev tokenURI must respond with a URI that implements https://eips.ethereum.org/EIPS/eip-1047
- * @dev TODO - update https://github.com/OpenZeppelin/openzeppelin-solidity/blob/master/contracts/token/ERC721/IERC721.sol#L17 when 1046 is finalized
- */
-contract ERC20TokenMetadata is IERC20 {
-  function tokenURI() external view returns (string);
-}
-
-contract ERC20WithMetadata is ERC20TokenMetadata {
-  string private _tokenURI;
-
-  constructor(string tokenURI)
-    public
-  {
-    _tokenURI = tokenURI;
-  }
-
-  function tokenURI() external view returns (string) {
-    return _tokenURI;
-  }
-}

contracts/drafts/ERC20Migrator.sol

@@ -1,5 +1,6 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
 import "../token/ERC20/IERC20.sol";
 import "../token/ERC20/ERC20Mintable.sol";
 import "../token/ERC20/SafeERC20.sol";
@@ -17,13 +18,13 @@ import "../math/Math.sol";
  * OpenZeppelin's ERC20Mintable, but the only functions that are needed are
  * `isMinter(address)` and `mint(address, amount)`. The migrator will check
  * that it is a minter for the token.
- * The balance from the legacy token will be transfered to the migrator, as it
+ * The balance from the legacy token will be transferred to the migrator, as it
  * is migrated, and remain there forever.
  * Although this contract can be used in many different scenarios, the main
  * motivation was to provide a way to migrate ERC20 tokens into an upgradeable
- * version of it using ZeppelinOS. To read more about how this can be done
+ * version of it using the OpenZeppelin SDK. To read more about how this can be done
  * using this implementation, please follow the official documentation site of
- * ZeppelinOS: https://docs.zeppelinos.org/docs/erc20_onboarding.html
+ * the OpenZeppelinSDK: https://docs.zeppelinos.org/docs/erc20_onboarding.html
  * Example of usage:
  * ```
  * const migrator = await ERC20Migrator.new(legacyToken.address);
@@ -31,70 +32,73 @@ import "../math/Math.sol";
  * await migrator.beginMigration(newToken.address);
  * ```
  */
-contract ERC20Migrator {
-  using SafeERC20 for IERC20;
+contract ERC20Migrator is Initializable {
+    using SafeERC20 for IERC20;
 
-  /// Address of the old token contract
-  IERC20 private _legacyToken;
+    /// Address of the old token contract
+    IERC20 private _legacyToken;
 
-  /// Address of the new token contract
-  ERC20Mintable private _newToken;
+    /// Address of the new token contract
+    ERC20Mintable private _newToken;
 
-  /**
-   * @param legacyToken address of the old token contract
-   */
-  constructor(IERC20 legacyToken) public {
-    require(legacyToken != address(0));
-    _legacyToken = legacyToken;
-  }
+    /**
+     * @param legacyToken address of the old token contract
+     */
+    function initialize(IERC20 legacyToken) public initializer {
+        require(address(legacyToken) != address(0));
+        _legacyToken = legacyToken;
+    }
 
-  /**
-   * @dev Returns the legacy token that is being migrated.
-   */
-  function legacyToken() public view returns (IERC20) {
-    return _legacyToken;
-  }
+    /**
+     * @dev Returns the legacy token that is being migrated.
+     */
+    function legacyToken() public view returns (IERC20) {
+        return _legacyToken;
+    }
 
-  /**
-   * @dev Returns the new token to which we are migrating.
-   */
-  function newToken() public view returns (IERC20) {
-    return _newToken;
-  }
+    /**
+     * @dev Returns the new token to which we are migrating.
+     */
+    function newToken() public view returns (IERC20) {
+        return _newToken;
+    }
 
-  /**
-   * @dev Begins the migration by setting which is the new token that will be
-   * minted. This contract must be a minter for the new token.
-   * @param newToken the token that will be minted
-   */
-  function beginMigration(ERC20Mintable newToken) public {
-    require(_newToken == address(0));
-    require(newToken != address(0));
-    require(newToken.isMinter(this));
+    /**
+     * @dev Begins the migration by setting which is the new token that will be
+     * minted. This contract must be a minter for the new token.
+     * @param newToken_ the token that will be minted
+     */
+    function beginMigration(ERC20Mintable newToken_) public {
+        require(address(_newToken) == address(0));
+        require(address(newToken_) != address(0));
+        require(newToken_.isMinter(address(this)));
 
-    _newToken = newToken;
-  }
+        _newToken = newToken_;
+    }
 
-  /**
-   * @dev Transfers part of an account's balance in the old token to this
-   * contract, and mints the same amount of new tokens for that account.
-   * @param account whose tokens will be migrated
-   * @param amount amount of tokens to be migrated
-   */
-  function migrate(address account, uint256 amount) public {
-    _legacyToken.safeTransferFrom(account, this, amount);
-    _newToken.mint(account, amount);
-  }
+    /**
+     * @dev Transfers part of an account's balance in the old token to this
+     * contract, and mints the same amount of new tokens for that account.
+     * @param account whose tokens will be migrated
+     * @param amount amount of tokens to be migrated
+     */
+    function migrate(address account, uint256 amount) public {
+        require(address(_newToken) != address(0));
+        _legacyToken.safeTransferFrom(account, address(this), amount);
+        _newToken.mint(account, amount);
+    }
 
-  /**
-   * @dev Transfers all of an account's allowed balance in the old token to
-   * this contract, and mints the same amount of new tokens for that account.
-   * @param account whose tokens will be migrated
-   */
-  function migrateAll(address account) public {
-    uint256 balance = _legacyToken.balanceOf(account);
-    uint256 allowance = _legacyToken.allowance(account, this);
-    uint256 amount = Math.min(balance, allowance);
-    migrate(account, amount);
-  }
+    /**
+     * @dev Transfers all of an account's allowed balance in the old token to
+     * this contract, and mints the same amount of new tokens for that account.
+     * @param account whose tokens will be migrated
+     */
+    function migrateAll(address account) public {
+        uint256 balance = _legacyToken.balanceOf(account);
+        uint256 allowance = _legacyToken.allowance(account, address(this));
+        uint256 amount = Math.min(balance, allowance);
+        migrate(account, amount);
+    }
+
+    uint256[50] private ______gap;
 }

contracts/drafts/ERC20Snapshot.sol

@@ -0,0 +1,142 @@
+pragma solidity ^0.5.2;
+
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
+import "../math/SafeMath.sol";
+import "../utils/Arrays.sol";
+import "../drafts/Counters.sol";
+import "../token/ERC20/ERC20.sol";
+
+/**
+ * @title ERC20 token with snapshots.
+ * @dev Inspired by Jordi Baylina's MiniMeToken to record historical balances:
+ * https://github.com/Giveth/minime/blob/ea04d950eea153a04c51fa510b068b9dded390cb/contracts/MiniMeToken.sol
+ * When a snapshot is made, the balances and totalSupply at the time of the snapshot are recorded for later
+ * access.
+ *
+ * To make a snapshot, call the `snapshot` function, which will emit the `Snapshot` event and return a snapshot id.
+ * To get the total supply from a snapshot, call the function `totalSupplyAt` with the snapshot id.
+ * To get the balance of an account from a snapshot, call the `balanceOfAt` function with the snapshot id and the
+ * account address.
+ * @author Validity Labs AG <info@validitylabs.org>
+ */
+contract ERC20Snapshot is Initializable, ERC20 {
+    using SafeMath for uint256;
+    using Arrays for uint256[];
+    using Counters for Counters.Counter;
+
+    // Snapshotted values have arrays of ids and the value corresponding to that id. These could be an array of a
+    // Snapshot struct, but that would impede usage of functions that work on an array.
+    struct Snapshots {
+        uint256[] ids;
+        uint256[] values;
+    }
+
+    mapping (address => Snapshots) private _accountBalanceSnapshots;
+    Snapshots private _totalSupplySnaphots;
+
+    // Snapshot ids increase monotonically, with the first value being 1. An id of 0 is invalid.
+    Counters.Counter private _currentSnapshotId;
+
+    event Snapshot(uint256 id);
+
+    // Creates a new snapshot id. Balances are only stored in snapshots on demand: unless a snapshot was taken, a
+    // balance change will not be recorded. This means the extra added cost of storing snapshotted balances is only paid
+    // when required, but is also flexible enough that it allows for e.g. daily snapshots.
+    function snapshot() public returns (uint256) {
+        _currentSnapshotId.increment();
+
+        uint256 currentId = _currentSnapshotId.current();
+        emit Snapshot(currentId);
+        return currentId;
+    }
+
+    function balanceOfAt(address account, uint256 snapshotId) public view returns (uint256) {
+        (bool snapshotted, uint256 value) = _valueAt(snapshotId, _accountBalanceSnapshots[account]);
+
+        return snapshotted ? value : balanceOf(account);
+    }
+
+    function totalSupplyAt(uint256 snapshotId) public view returns(uint256) {
+        (bool snapshotted, uint256 value) = _valueAt(snapshotId, _totalSupplySnaphots);
+
+        return snapshotted ? value : totalSupply();
+    }
+
+    // _transfer, _mint and _burn are the only functions where the balances are modified, so it is there that the
+    // snapshots are updated. Note that the update happens _before_ the balance change, with the pre-modified value.
+    // The same is true for the total supply and _mint and _burn.
+    function _transfer(address from, address to, uint256 value) internal {
+        _updateAccountSnapshot(from);
+        _updateAccountSnapshot(to);
+
+        super._transfer(from, to, value);
+    }
+
+    function _mint(address account, uint256 value) internal {
+        _updateAccountSnapshot(account);
+        _updateTotalSupplySnapshot();
+
+        super._mint(account, value);
+    }
+
+    function _burn(address account, uint256 value) internal {
+        _updateAccountSnapshot(account);
+        _updateTotalSupplySnapshot();
+
+        super._burn(account, value);
+    }
+
+    // When a valid snapshot is queried, there are three possibilities:
+    //  a) The queried value was not modified after the snapshot was taken. Therefore, a snapshot entry was never
+    //  created for this id, and all stored snapshot ids are smaller than the requested one. The value that corresponds
+    //  to this id is the current one.
+    //  b) The queried value was modified after the snapshot was taken. Therefore, there will be an entry with the
+    //  requested id, and its value is the one to return.
+    //  c) More snapshots were created after the requested one, and the queried value was later modified. There will be
+    //  no entry for the requested id: the value that corresponds to it is that of the smallest snapshot id that is
+    //  larger than the requested one.
+    //
+    // In summary, we need to find an element in an array, returning the index of the smallest value that is larger if
+    // it is not found, unless said value doesn't exist (e.g. when all values are smaller). Arrays.findUpperBound does
+    // exactly this.
+    function _valueAt(uint256 snapshotId, Snapshots storage snapshots)
+        private view returns (bool, uint256)
+    {
+        require(snapshotId > 0);
+        require(snapshotId <= _currentSnapshotId.current());
+
+        uint256 index = snapshots.ids.findUpperBound(snapshotId);
+
+        if (index == snapshots.ids.length) {
+            return (false, 0);
+        } else {
+            return (true, snapshots.values[index]);
+        }
+    }
+
+    function _updateAccountSnapshot(address account) private {
+        _updateSnapshot(_accountBalanceSnapshots[account], balanceOf(account));
+    }
+
+    function _updateTotalSupplySnapshot() private {
+        _updateSnapshot(_totalSupplySnaphots, totalSupply());
+    }
+
+    function _updateSnapshot(Snapshots storage snapshots, uint256 currentValue) private {
+        uint256 currentId = _currentSnapshotId.current();
+        if (_lastSnapshotId(snapshots.ids) < currentId) {
+            snapshots.ids.push(currentId);
+            snapshots.values.push(currentValue);
+        }
+    }
+
+    function _lastSnapshotId(uint256[] storage ids) private view returns (uint256) {
+        if (ids.length == 0) {
+            return 0;
+        } else {
+            return ids[ids.length - 1];
+        }
+    }
+
+    uint256[50] private ______gap;
+}

contracts/drafts/SignatureBouncer.sol

@@ -1,5 +1,6 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
 import "../access/roles/SignerRole.sol";
 import "../cryptography/ECDSA.sol";
 
@@ -29,118 +30,94 @@ import "../cryptography/ECDSA.sol";
  * @notice A method that uses the `onlyValidSignatureAndData` modifier must make
  * the _signature parameter the "last" parameter. You cannot sign a message that
  * has its own signature in it so the last 128 bytes of msg.data (which
- * represents the length of the _signature data and the _signaature data itself)
+ * represents the length of the _signature data and the _signature data itself)
  * is ignored when validating. Also non fixed sized parameters make constructing
  * the data in the signature much more complex.
  * See https://ethereum.stackexchange.com/a/50616 for more details.
  */
-contract SignatureBouncer is SignerRole {
-  using ECDSA for bytes32;
+contract SignatureBouncer is Initializable, SignerRole {
+    using ECDSA for bytes32;
 
-  // Function selectors are 4 bytes long, as documented in
-  // https://solidity.readthedocs.io/en/v0.4.24/abi-spec.html#function-selector
-  uint256 private constant _METHOD_ID_SIZE = 4;
-  // Signature size is 65 bytes (tightly packed v + r + s), but gets padded to 96 bytes
-  uint256 private constant _SIGNATURE_SIZE = 96;
+    // Function selectors are 4 bytes long, as documented in
+    // https://solidity.readthedocs.io/en/v0.4.24/abi-spec.html#function-selector
+    uint256 private constant _METHOD_ID_SIZE = 4;
+    // Signature size is 65 bytes (tightly packed v + r + s), but gets padded to 96 bytes
+    uint256 private constant _SIGNATURE_SIZE = 96;
 
-  constructor() internal {}
-
-  /**
-   * @dev requires that a valid signature of a signer was provided
-   */
-  modifier onlyValidSignature(bytes signature)
-  {
-    require(_isValidSignature(msg.sender, signature));
-    _;
-  }
-
-  /**
-   * @dev requires that a valid signature with a specifed method of a signer was provided
-   */
-  modifier onlyValidSignatureAndMethod(bytes signature)
-  {
-    require(_isValidSignatureAndMethod(msg.sender, signature));
-    _;
-  }
-
-  /**
-   * @dev requires that a valid signature with a specifed method and params of a signer was provided
-   */
-  modifier onlyValidSignatureAndData(bytes signature)
-  {
-    require(_isValidSignatureAndData(msg.sender, signature));
-    _;
-  }
-
-  /**
-   * @dev is the signature of `this + sender` from a signer?
-   * @return bool
-   */
-  function _isValidSignature(address account, bytes signature)
-    internal
-    view
-    returns (bool)
-  {
-    return _isValidDataHash(
-      keccak256(abi.encodePacked(address(this), account)),
-      signature
-    );
-  }
-
-  /**
-   * @dev is the signature of `this + sender + methodId` from a signer?
-   * @return bool
-   */
-  function _isValidSignatureAndMethod(address account, bytes signature)
-    internal
-    view
-    returns (bool)
-  {
-    bytes memory data = new bytes(_METHOD_ID_SIZE);
-    for (uint i = 0; i < data.length; i++) {
-      data[i] = msg.data[i];
+    function initialize(address sender) public initializer {
+        SignerRole.initialize(sender);
     }
-    return _isValidDataHash(
-      keccak256(abi.encodePacked(address(this), account, data)),
-      signature
-    );
-  }
 
-  /**
-    * @dev is the signature of `this + sender + methodId + params(s)` from a signer?
-    * @notice the signature parameter of the method being validated must be the "last" parameter
-    * @return bool
-    */
-  function _isValidSignatureAndData(address account, bytes signature)
-    internal
-    view
-    returns (bool)
-  {
-    require(msg.data.length > _SIGNATURE_SIZE);
-    bytes memory data = new bytes(msg.data.length - _SIGNATURE_SIZE);
-    for (uint i = 0; i < data.length; i++) {
-      data[i] = msg.data[i];
+    /**
+     * @dev requires that a valid signature of a signer was provided
+     */
+    modifier onlyValidSignature(bytes memory signature) {
+        require(_isValidSignature(msg.sender, signature));
+        _;
     }
-    return _isValidDataHash(
-      keccak256(abi.encodePacked(address(this), account, data)),
-      signature
-    );
-  }
 
-  /**
-   * @dev internal function to convert a hash to an eth signed message
-   * and then recover the signature and check it against the signer role
-   * @return bool
-   */
-  function _isValidDataHash(bytes32 hash, bytes signature)
-    internal
-    view
-    returns (bool)
-  {
-    address signer = hash
-      .toEthSignedMessageHash()
-      .recover(signature);
+    /**
+     * @dev requires that a valid signature with a specified method of a signer was provided
+     */
+    modifier onlyValidSignatureAndMethod(bytes memory signature) {
+        require(_isValidSignatureAndMethod(msg.sender, signature));
+        _;
+    }
 
-    return signer != address(0) && isSigner(signer);
-  }
+    /**
+     * @dev requires that a valid signature with a specified method and params of a signer was provided
+     */
+    modifier onlyValidSignatureAndData(bytes memory signature) {
+        require(_isValidSignatureAndData(msg.sender, signature));
+        _;
+    }
+
+    /**
+     * @dev is the signature of `this + account` from a signer?
+     * @return bool
+     */
+    function _isValidSignature(address account, bytes memory signature) internal view returns (bool) {
+        return _isValidDataHash(keccak256(abi.encodePacked(address(this), account)), signature);
+    }
+
+    /**
+     * @dev is the signature of `this + account + methodId` from a signer?
+     * @return bool
+     */
+    function _isValidSignatureAndMethod(address account, bytes memory signature) internal view returns (bool) {
+        bytes memory data = new bytes(_METHOD_ID_SIZE);
+        for (uint i = 0; i < data.length; i++) {
+            data[i] = msg.data[i];
+        }
+        return _isValidDataHash(keccak256(abi.encodePacked(address(this), account, data)), signature);
+    }
+
+    /**
+     * @dev is the signature of `this + account + methodId + params(s)` from a signer?
+     * @notice the signature parameter of the method being validated must be the "last" parameter
+     * @return bool
+     */
+    function _isValidSignatureAndData(address account, bytes memory signature) internal view returns (bool) {
+        require(msg.data.length > _SIGNATURE_SIZE);
+
+        bytes memory data = new bytes(msg.data.length - _SIGNATURE_SIZE);
+        for (uint i = 0; i < data.length; i++) {
+            data[i] = msg.data[i];
+        }
+
+        return _isValidDataHash(keccak256(abi.encodePacked(address(this), account, data)), signature);
+    }
+
+    /**
+     * @dev internal function to convert a hash to an eth signed message
+     * and then recover the signature and check it against the signer role
+     * @return bool
+     */
+    function _isValidDataHash(bytes32 hash, bytes memory signature) internal view returns (bool) {
+        address signer = hash.toEthSignedMessageHash().recover(signature);
+
+        return signer != address(0) && isSigner(signer);
+    }
+
+    uint256[50] private ______gap;
 }

contracts/drafts/SignedSafeMath.sol

@@ -0,0 +1,60 @@
+pragma solidity ^0.5.2;
+
+/**
+ * @title SignedSafeMath
+ * @dev Signed math operations with safety checks that revert on error
+ */
+library SignedSafeMath {
+    int256 constant private INT256_MIN = -2**255;
+
+    /**
+     * @dev Multiplies two signed integers, reverts on overflow.
+     */
+    function mul(int256 a, int256 b) internal pure returns (int256) {
+        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
+        // benefit is lost if 'b' is also tested.
+        // See: https://github.com/OpenZeppelin/openzeppelin-solidity/pull/522
+        if (a == 0) {
+            return 0;
+        }
+
+        require(!(a == -1 && b == INT256_MIN)); // This is the only case of overflow not detected by the check below
+
+        int256 c = a * b;
+        require(c / a == b);
+
+        return c;
+    }
+
+    /**
+     * @dev Integer division of two signed integers truncating the quotient, reverts on division by zero.
+     */
+    function div(int256 a, int256 b) internal pure returns (int256) {
+        require(b != 0); // Solidity only automatically asserts when dividing by 0
+        require(!(b == -1 && a == INT256_MIN)); // This is the only case of overflow
+
+        int256 c = a / b;
+
+        return c;
+    }
+
+    /**
+     * @dev Subtracts two signed integers, reverts on overflow.
+     */
+    function sub(int256 a, int256 b) internal pure returns (int256) {
+        int256 c = a - b;
+        require((b >= 0 && c <= a) || (b < 0 && c > a));
+
+        return c;
+    }
+
+    /**
+     * @dev Adds two signed integers, reverts on overflow.
+     */
+    function add(int256 a, int256 b) internal pure returns (int256) {
+        int256 c = a + b;
+        require((b >= 0 && c >= a) || (b < 0 && c < a));
+
+        return c;
+    }
+}

contracts/drafts/TokenVesting.sol

@@ -1,7 +1,6 @@
-/* solium-disable security/no-block-members */
-
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
 import "../token/ERC20/SafeERC20.sol";
 import "../ownership/Ownable.sol";
 import "../math/SafeMath.sol";
@@ -12,164 +11,167 @@ import "../math/SafeMath.sol";
  * typical vesting scheme, with a cliff and vesting period. Optionally revocable by the
  * owner.
  */
-contract TokenVesting is Ownable {
-  using SafeMath for uint256;
-  using SafeERC20 for IERC20;
+contract TokenVesting is Initializable, Ownable {
+    // The vesting schedule is time-based (i.e. using block timestamps as opposed to e.g. block numbers), and is
+    // therefore sensitive to timestamp manipulation (which is something miners can do, to a certain degree). Therefore,
+    // it is recommended to avoid using short time durations (less than a minute). Typical vesting schemes, with a
+    // cliff period of a year and a duration of four years, are safe to use.
+    // solhint-disable not-rely-on-time
 
-  event TokensReleased(address token, uint256 amount);
-  event TokenVestingRevoked(address token);
+    using SafeMath for uint256;
+    using SafeERC20 for IERC20;
 
-  // beneficiary of tokens after they are released
-  address private _beneficiary;
+    event TokensReleased(address token, uint256 amount);
+    event TokenVestingRevoked(address token);
 
-  uint256 private _cliff;
-  uint256 private _start;
-  uint256 private _duration;
+    // beneficiary of tokens after they are released
+    address private _beneficiary;
 
-  bool private _revocable;
+    // Durations and timestamps are expressed in UNIX time, the same units as block.timestamp.
+    uint256 private _cliff;
+    uint256 private _start;
+    uint256 private _duration;
 
-  mapping (address => uint256) private _released;
-  mapping (address => bool) private _revoked;
+    bool private _revocable;
 
-  /**
-   * @dev Creates a vesting contract that vests its balance of any ERC20 token to the
-   * beneficiary, gradually in a linear fashion until start + duration. By then all
-   * of the balance will have vested.
-   * @param beneficiary address of the beneficiary to whom vested tokens are transferred
-   * @param cliffDuration duration in seconds of the cliff in which tokens will begin to vest
-   * @param start the time (as Unix time) at which point vesting starts
-   * @param duration duration in seconds of the period in which the tokens will vest
-   * @param revocable whether the vesting is revocable or not
-   */
-  constructor(
-    address beneficiary,
-    uint256 start,
-    uint256 cliffDuration,
-    uint256 duration,
-    bool revocable
-  )
-    public
-  {
-    require(beneficiary != address(0));
-    require(cliffDuration <= duration);
-    require(duration > 0);
-    require(start.add(duration) > block.timestamp);
+    mapping (address => uint256) private _released;
+    mapping (address => bool) private _revoked;
 
-    _beneficiary = beneficiary;
-    _revocable = revocable;
-    _duration = duration;
-    _cliff = start.add(cliffDuration);
-    _start = start;
-  }
+    /**
+     * @dev Creates a vesting contract that vests its balance of any ERC20 token to the
+     * beneficiary, gradually in a linear fashion until start + duration. By then all
+     * of the balance will have vested.
+     * @param beneficiary address of the beneficiary to whom vested tokens are transferred
+     * @param cliffDuration duration in seconds of the cliff in which tokens will begin to vest
+     * @param start the time (as Unix time) at which point vesting starts
+     * @param duration duration in seconds of the period in which the tokens will vest
+     * @param revocable whether the vesting is revocable or not
+     */
+    function initialize(address beneficiary, uint256 start, uint256 cliffDuration, uint256 duration, bool revocable, address sender) public initializer {
+        Ownable.initialize(sender);
 
-  /**
-   * @return the beneficiary of the tokens.
-   */
-  function beneficiary() public view returns(address) {
-    return _beneficiary;
-  }
+        require(beneficiary != address(0));
+        require(cliffDuration <= duration);
+        require(duration > 0);
+        require(start.add(duration) > block.timestamp);
 
-  /**
-   * @return the cliff time of the token vesting.
-   */
-  function cliff() public view returns(uint256) {
-    return _cliff;
-  }
-
-  /**
-   * @return the start time of the token vesting.
-   */
-  function start() public view returns(uint256) {
-    return _start;
-  }
-
-  /**
-   * @return the duration of the token vesting.
-   */
-  function duration() public view returns(uint256) {
-    return _duration;
-  }
-
-  /**
-   * @return true if the vesting is revocable.
-   */
-  function revocable() public view returns(bool) {
-    return _revocable;
-  }
-
-  /**
-   * @return the amount of the token released.
-   */
-  function released(address token) public view returns(uint256) {
-    return _released[token];
-  }
-
-  /**
-   * @return true if the token is revoked.
-   */
-  function revoked(address token) public view returns(bool) {
-    return _revoked[token];
-  }
-
-  /**
-   * @notice Transfers vested tokens to beneficiary.
-   * @param token ERC20 token which is being vested
-   */
-  function release(IERC20 token) public {
-    uint256 unreleased = _releasableAmount(token);
-
-    require(unreleased > 0);
-
-    _released[token] = _released[token].add(unreleased);
-
-    token.safeTransfer(_beneficiary, unreleased);
-
-    emit TokensReleased(token, unreleased);
-  }
-
-  /**
-   * @notice Allows the owner to revoke the vesting. Tokens already vested
-   * remain in the contract, the rest are returned to the owner.
-   * @param token ERC20 token which is being vested
-   */
-  function revoke(IERC20 token) public onlyOwner {
-    require(_revocable);
-    require(!_revoked[token]);
-
-    uint256 balance = token.balanceOf(address(this));
-
-    uint256 unreleased = _releasableAmount(token);
-    uint256 refund = balance.sub(unreleased);
-
-    _revoked[token] = true;
-
-    token.safeTransfer(owner(), refund);
-
-    emit TokenVestingRevoked(token);
-  }
-
-  /**
-   * @dev Calculates the amount that has already vested but hasn't been released yet.
-   * @param token ERC20 token which is being vested
-   */
-  function _releasableAmount(IERC20 token) private view returns (uint256) {
-    return _vestedAmount(token).sub(_released[token]);
-  }
-
-  /**
-   * @dev Calculates the amount that has already vested.
-   * @param token ERC20 token which is being vested
-   */
-  function _vestedAmount(IERC20 token) private view returns (uint256) {
-    uint256 currentBalance = token.balanceOf(this);
-    uint256 totalBalance = currentBalance.add(_released[token]);
-
-    if (block.timestamp < _cliff) {
-      return 0;
-    } else if (block.timestamp >= _start.add(_duration) || _revoked[token]) {
-      return totalBalance;
-    } else {
-      return totalBalance.mul(block.timestamp.sub(_start)).div(_duration);
+        _beneficiary = beneficiary;
+        _revocable = revocable;
+        _duration = duration;
+        _cliff = start.add(cliffDuration);
+        _start = start;
     }
-  }
+
+    /**
+     * @return the beneficiary of the tokens.
+     */
+    function beneficiary() public view returns (address) {
+        return _beneficiary;
+    }
+
+    /**
+     * @return the cliff time of the token vesting.
+     */
+    function cliff() public view returns (uint256) {
+        return _cliff;
+    }
+
+    /**
+     * @return the start time of the token vesting.
+     */
+    function start() public view returns (uint256) {
+        return _start;
+    }
+
+    /**
+     * @return the duration of the token vesting.
+     */
+    function duration() public view returns (uint256) {
+        return _duration;
+    }
+
+    /**
+     * @return true if the vesting is revocable.
+     */
+    function revocable() public view returns (bool) {
+        return _revocable;
+    }
+
+    /**
+     * @return the amount of the token released.
+     */
+    function released(address token) public view returns (uint256) {
+        return _released[token];
+    }
+
+    /**
+     * @return true if the token is revoked.
+     */
+    function revoked(address token) public view returns (bool) {
+        return _revoked[token];
+    }
+
+    /**
+     * @notice Transfers vested tokens to beneficiary.
+     * @param token ERC20 token which is being vested
+     */
+    function release(IERC20 token) public {
+        uint256 unreleased = _releasableAmount(token);
+
+        require(unreleased > 0);
+
+        _released[address(token)] = _released[address(token)].add(unreleased);
+
+        token.safeTransfer(_beneficiary, unreleased);
+
+        emit TokensReleased(address(token), unreleased);
+    }
+
+    /**
+     * @notice Allows the owner to revoke the vesting. Tokens already vested
+     * remain in the contract, the rest are returned to the owner.
+     * @param token ERC20 token which is being vested
+     */
+    function revoke(IERC20 token) public onlyOwner {
+        require(_revocable);
+        require(!_revoked[address(token)]);
+
+        uint256 balance = token.balanceOf(address(this));
+
+        uint256 unreleased = _releasableAmount(token);
+        uint256 refund = balance.sub(unreleased);
+
+        _revoked[address(token)] = true;
+
+        token.safeTransfer(owner(), refund);
+
+        emit TokenVestingRevoked(address(token));
+    }
+
+    /**
+     * @dev Calculates the amount that has already vested but hasn't been released yet.
+     * @param token ERC20 token which is being vested
+     */
+    function _releasableAmount(IERC20 token) private view returns (uint256) {
+        return _vestedAmount(token).sub(_released[address(token)]);
+    }
+
+    /**
+     * @dev Calculates the amount that has already vested.
+     * @param token ERC20 token which is being vested
+     */
+    function _vestedAmount(IERC20 token) private view returns (uint256) {
+        uint256 currentBalance = token.balanceOf(address(this));
+        uint256 totalBalance = currentBalance.add(_released[address(token)]);
+
+        if (block.timestamp < _cliff) {
+            return 0;
+        } else if (block.timestamp >= _start.add(_duration) || _revoked[address(token)]) {
+            return totalBalance;
+        } else {
+            return totalBalance.mul(block.timestamp.sub(_start)).div(_duration);
+        }
+    }
+
+    uint256[50] private ______gap;
 }

contracts/examples/SampleCrowdsale.sol

@@ -1,5 +1,6 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
 import "../crowdsale/validation/CappedCrowdsale.sol";
 import "../crowdsale/distribution/RefundableCrowdsale.sol";
 import "../crowdsale/emission/MintedCrowdsale.sol";
@@ -11,8 +12,13 @@ import "../token/ERC20/ERC20Detailed.sol";
  * @dev Very simple ERC20 Token that can be minted.
  * It is meant to be used in a crowdsale contract.
  */
-contract SampleCrowdsaleToken is ERC20Mintable, ERC20Detailed {
-  constructor() public ERC20Detailed("Sample Crowdsale Token", "SCT", 18) {}
+contract SampleCrowdsaleToken is Initializable, ERC20Mintable, ERC20Detailed {
+    function initialize(address sender) public initializer {
+        ERC20Mintable.initialize(sender);
+        ERC20Detailed.initialize("Sample Crowdsale Token", "SCT", 18);
+    }
+
+    uint256[50] private ______gap;
 }
 
 /**
@@ -28,30 +34,29 @@ contract SampleCrowdsaleToken is ERC20Mintable, ERC20Detailed {
  * After adding multiple features it's good practice to run integration tests
  * to ensure that subcontracts works together as intended.
  */
-// XXX There doesn't seem to be a way to split this line that keeps solium
-// happy. See:
-// https://github.com/duaraghav8/Solium/issues/205
-// --elopio - 2018-05-10
-// solium-disable-next-line max-len
-contract SampleCrowdsale is CappedCrowdsale, RefundableCrowdsale, MintedCrowdsale {
+contract SampleCrowdsale is Initializable, Crowdsale, CappedCrowdsale, RefundableCrowdsale, MintedCrowdsale {
 
-  constructor(
-    uint256 openingTime,
-    uint256 closingTime,
-    uint256 rate,
-    address wallet,
-    uint256 cap,
-    ERC20Mintable token,
-    uint256 goal
-  )
-    public
-    Crowdsale(rate, wallet, token)
-    CappedCrowdsale(cap)
-    TimedCrowdsale(openingTime, closingTime)
-    RefundableCrowdsale(goal)
-  {
-    //As goal needs to be met for a successful crowdsale
-    //the value needs to less or equal than a cap which is limit for accepted funds
-    require(goal <= cap);
-  }
+    function initialize(
+        uint256 openingTime,
+        uint256 closingTime,
+        uint256 rate,
+        address payable wallet,
+        uint256 cap,
+        ERC20Mintable token,
+        uint256 goal
+    )
+        public
+        initializer
+    {
+        Crowdsale.initialize(rate, wallet, token);
+        CappedCrowdsale.initialize(cap);
+        TimedCrowdsale.initialize(openingTime, closingTime);
+        RefundableCrowdsale.initialize(goal);
+
+        //As goal needs to be met for a successful crowdsale
+        //the value needs to less or equal than a cap which is limit for accepted funds
+        require(goal <= cap);
+    }
+
+    uint256[50] private ______gap;
 }

contracts/examples/SimpleToken.sol

@@ -1,6 +1,8 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
 import "../token/ERC20/ERC20.sol";
+import "../token/ERC20/ERC20Detailed.sol";
 
 /**
  * @title SimpleToken
@@ -8,19 +10,17 @@ import "../token/ERC20/ERC20.sol";
  * Note they can later distribute these tokens as they wish using `transfer` and other
  * `ERC20` functions.
  */
-contract SimpleToken is ERC20 {
+contract SimpleToken is Initializable, ERC20, ERC20Detailed {
+    uint8 public constant DECIMALS = 18;
+    uint256 public constant INITIAL_SUPPLY = 10000 * (10 ** uint256(DECIMALS));
 
-  string public constant name = "SimpleToken";
-  string public constant symbol = "SIM";
-  uint8 public constant decimals = 18;
-
-  uint256 public constant INITIAL_SUPPLY = 10000 * (10 ** uint256(decimals));
-
-  /**
-   * @dev Constructor that gives msg.sender all of existing tokens.
-   */
-  constructor() public {
-    _mint(msg.sender, INITIAL_SUPPLY);
-  }
+    /**
+     * @dev Constructor that gives msg.sender all of existing tokens.
+     */
+    function initialize(address sender) public initializer {
+        ERC20Detailed.initialize("SimpleToken", "SIM", DECIMALS);
+        _mint(sender, INITIAL_SUPPLY);
+    }
 
+    uint256[50] private ______gap;
 }

contracts/introspection/ERC165.sol

@@ -1,5 +1,6 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
 import "./IERC165.sol";
 
 /**
@@ -7,47 +8,40 @@ import "./IERC165.sol";
  * @author Matt Condon (@shrugs)
  * @dev Implements ERC165 using a lookup table.
  */
-contract ERC165 is IERC165 {
+contract ERC165 is Initializable, IERC165 {
+    bytes4 private constant _INTERFACE_ID_ERC165 = 0x01ffc9a7;
+    /*
+     * 0x01ffc9a7 ===
+     *     bytes4(keccak256('supportsInterface(bytes4)'))
+     */
 
-  bytes4 private constant _InterfaceId_ERC165 = 0x01ffc9a7;
-  /**
-   * 0x01ffc9a7 ===
-   *   bytes4(keccak256('supportsInterface(bytes4)'))
-   */
+    /**
+     * @dev a mapping of interface id to whether or not it's supported
+     */
+    mapping(bytes4 => bool) private _supportedInterfaces;
 
-  /**
-   * @dev a mapping of interface id to whether or not it's supported
-   */
-  mapping(bytes4 => bool) private _supportedInterfaces;
+    /**
+     * @dev A contract implementing SupportsInterfaceWithLookup
+     * implement ERC165 itself
+     */
+    function initialize() public initializer {
+        _registerInterface(_INTERFACE_ID_ERC165);
+    }
 
-  /**
-   * @dev A contract implementing SupportsInterfaceWithLookup
-   * implement ERC165 itself
-   */
-  constructor()
-    internal
-  {
-    _registerInterface(_InterfaceId_ERC165);
-  }
+    /**
+     * @dev implement supportsInterface(bytes4) using a lookup table
+     */
+    function supportsInterface(bytes4 interfaceId) public view returns (bool) {
+        return _supportedInterfaces[interfaceId];
+    }
 
-  /**
-   * @dev implement supportsInterface(bytes4) using a lookup table
-   */
-  function supportsInterface(bytes4 interfaceId)
-    external
-    view
-    returns (bool)
-  {
-    return _supportedInterfaces[interfaceId];
-  }
+    /**
+     * @dev internal method for registering an interface
+     */
+    function _registerInterface(bytes4 interfaceId) internal {
+        require(interfaceId != 0xffffffff);
+        _supportedInterfaces[interfaceId] = true;
+    }
 
-  /**
-   * @dev internal method for registering an interface
-   */
-  function _registerInterface(bytes4 interfaceId)
-    internal
-  {
-    require(interfaceId != 0xffffffff);
-    _supportedInterfaces[interfaceId] = true;
-  }
+    uint256[50] private ______gap;
 }

contracts/introspection/ERC165Checker.sol

@@ -1,146 +1,123 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
 /**
  * @title ERC165Checker
  * @dev Use `using ERC165Checker for address`; to include this library
- * https://github.com/ethereum/EIPs/blob/master/EIPS/eip-165.md
+ * https://eips.ethereum.org/EIPS/eip-165
  */
 library ERC165Checker {
-  // As per the EIP-165 spec, no interface should ever match 0xffffffff
-  bytes4 private constant _InterfaceId_Invalid = 0xffffffff;
+    // As per the EIP-165 spec, no interface should ever match 0xffffffff
+    bytes4 private constant _INTERFACE_ID_INVALID = 0xffffffff;
 
-  bytes4 private constant _InterfaceId_ERC165 = 0x01ffc9a7;
-  /**
-   * 0x01ffc9a7 ===
-   *   bytes4(keccak256('supportsInterface(bytes4)'))
-   */
+    bytes4 private constant _INTERFACE_ID_ERC165 = 0x01ffc9a7;
+    /*
+     * 0x01ffc9a7 ===
+     *     bytes4(keccak256('supportsInterface(bytes4)'))
+     */
 
-  /**
-   * @notice Query if a contract supports ERC165
-   * @param account The address of the contract to query for support of ERC165
-   * @return true if the contract at account implements ERC165
-   */
-  function _supportsERC165(address account)
-    internal
-    view
-    returns (bool)
-  {
-    // Any contract that implements ERC165 must explicitly indicate support of
-    // InterfaceId_ERC165 and explicitly indicate non-support of InterfaceId_Invalid
-    return _supportsERC165Interface(account, _InterfaceId_ERC165) &&
-      !_supportsERC165Interface(account, _InterfaceId_Invalid);
-  }
-
-  /**
-   * @notice Query if a contract implements an interface, also checks support of ERC165
-   * @param account The address of the contract to query for support of an interface
-   * @param interfaceId The interface identifier, as specified in ERC-165
-   * @return true if the contract at account indicates support of the interface with
-   * identifier interfaceId, false otherwise
-   * @dev Interface identification is specified in ERC-165.
-   */
-  function _supportsInterface(address account, bytes4 interfaceId)
-    internal
-    view
-    returns (bool)
-  {
-    // query support of both ERC165 as per the spec and support of _interfaceId
-    return _supportsERC165(account) &&
-      _supportsERC165Interface(account, interfaceId);
-  }
-
-  /**
-   * @notice Query if a contract implements interfaces, also checks support of ERC165
-   * @param account The address of the contract to query for support of an interface
-   * @param interfaceIds A list of interface identifiers, as specified in ERC-165
-   * @return true if the contract at account indicates support all interfaces in the
-   * interfaceIds list, false otherwise
-   * @dev Interface identification is specified in ERC-165.
-   */
-  function _supportsAllInterfaces(address account, bytes4[] interfaceIds)
-    internal
-    view
-    returns (bool)
-  {
-    // query support of ERC165 itself
-    if (!_supportsERC165(account)) {
-      return false;
+    /**
+     * @notice Query if a contract supports ERC165
+     * @param account The address of the contract to query for support of ERC165
+     * @return true if the contract at account implements ERC165
+     */
+    function _supportsERC165(address account) internal view returns (bool) {
+        // Any contract that implements ERC165 must explicitly indicate support of
+        // InterfaceId_ERC165 and explicitly indicate non-support of InterfaceId_Invalid
+        return _supportsERC165Interface(account, _INTERFACE_ID_ERC165) &&
+            !_supportsERC165Interface(account, _INTERFACE_ID_INVALID);
     }
 
-    // query support of each interface in _interfaceIds
-    for (uint256 i = 0; i < interfaceIds.length; i++) {
-      if (!_supportsERC165Interface(account, interfaceIds[i])) {
-        return false;
-      }
+    /**
+     * @notice Query if a contract implements an interface, also checks support of ERC165
+     * @param account The address of the contract to query for support of an interface
+     * @param interfaceId The interface identifier, as specified in ERC-165
+     * @return true if the contract at account indicates support of the interface with
+     * identifier interfaceId, false otherwise
+     * @dev Interface identification is specified in ERC-165.
+     */
+    function _supportsInterface(address account, bytes4 interfaceId) internal view returns (bool) {
+        // query support of both ERC165 as per the spec and support of _interfaceId
+        return _supportsERC165(account) &&
+            _supportsERC165Interface(account, interfaceId);
     }
 
-    // all interfaces supported
-    return true;
-  }
+    /**
+     * @notice Query if a contract implements interfaces, also checks support of ERC165
+     * @param account The address of the contract to query for support of an interface
+     * @param interfaceIds A list of interface identifiers, as specified in ERC-165
+     * @return true if the contract at account indicates support all interfaces in the
+     * interfaceIds list, false otherwise
+     * @dev Interface identification is specified in ERC-165.
+     */
+    function _supportsAllInterfaces(address account, bytes4[] memory interfaceIds) internal view returns (bool) {
+        // query support of ERC165 itself
+        if (!_supportsERC165(account)) {
+            return false;
+        }
 
-  /**
-   * @notice Query if a contract implements an interface, does not check ERC165 support
-   * @param account The address of the contract to query for support of an interface
-   * @param interfaceId The interface identifier, as specified in ERC-165
-   * @return true if the contract at account indicates support of the interface with
-   * identifier interfaceId, false otherwise
-   * @dev Assumes that account contains a contract that supports ERC165, otherwise
-   * the behavior of this method is undefined. This precondition can be checked
-   * with the `supportsERC165` method in this library.
-   * Interface identification is specified in ERC-165.
-   */
-  function _supportsERC165Interface(address account, bytes4 interfaceId)
-    private
-    view
-    returns (bool)
-  {
-    // success determines whether the staticcall succeeded and result determines
-    // whether the contract at account indicates support of _interfaceId
-    (bool success, bool result) = _callERC165SupportsInterface(
-      account, interfaceId);
+        // query support of each interface in _interfaceIds
+        for (uint256 i = 0; i < interfaceIds.length; i++) {
+            if (!_supportsERC165Interface(account, interfaceIds[i])) {
+                return false;
+            }
+        }
 
-    return (success && result);
-  }
-
-  /**
-   * @notice Calls the function with selector 0x01ffc9a7 (ERC165) and suppresses throw
-   * @param account The address of the contract to query for support of an interface
-   * @param interfaceId The interface identifier, as specified in ERC-165
-   * @return success true if the STATICCALL succeeded, false otherwise
-   * @return result true if the STATICCALL succeeded and the contract at account
-   * indicates support of the interface with identifier interfaceId, false otherwise
-   */
-  function _callERC165SupportsInterface(
-    address account,
-    bytes4 interfaceId
-  )
-    private
-    view
-    returns (bool success, bool result)
-  {
-    bytes memory encodedParams = abi.encodeWithSelector(
-      _InterfaceId_ERC165,
-      interfaceId
-    );
-
-    // solium-disable-next-line security/no-inline-assembly
-    assembly {
-      let encodedParams_data := add(0x20, encodedParams)
-      let encodedParams_size := mload(encodedParams)
-
-      let output := mload(0x40)  // Find empty storage location using "free memory pointer"
-      mstore(output, 0x0)
-
-      success := staticcall(
-        30000,                 // 30k gas
-        account,              // To addr
-        encodedParams_data,
-        encodedParams_size,
-        output,
-        0x20                   // Outputs are 32 bytes long
-      )
-
-      result := mload(output)  // Load the result
+        // all interfaces supported
+        return true;
+    }
+
+    /**
+     * @notice Query if a contract implements an interface, does not check ERC165 support
+     * @param account The address of the contract to query for support of an interface
+     * @param interfaceId The interface identifier, as specified in ERC-165
+     * @return true if the contract at account indicates support of the interface with
+     * identifier interfaceId, false otherwise
+     * @dev Assumes that account contains a contract that supports ERC165, otherwise
+     * the behavior of this method is undefined. This precondition can be checked
+     * with the `supportsERC165` method in this library.
+     * Interface identification is specified in ERC-165.
+     */
+    function _supportsERC165Interface(address account, bytes4 interfaceId) private view returns (bool) {
+        // success determines whether the staticcall succeeded and result determines
+        // whether the contract at account indicates support of _interfaceId
+        (bool success, bool result) = _callERC165SupportsInterface(account, interfaceId);
+
+        return (success && result);
+    }
+
+    /**
+     * @notice Calls the function with selector 0x01ffc9a7 (ERC165) and suppresses throw
+     * @param account The address of the contract to query for support of an interface
+     * @param interfaceId The interface identifier, as specified in ERC-165
+     * @return success true if the STATICCALL succeeded, false otherwise
+     * @return result true if the STATICCALL succeeded and the contract at account
+     * indicates support of the interface with identifier interfaceId, false otherwise
+     */
+    function _callERC165SupportsInterface(address account, bytes4 interfaceId)
+        private
+        view
+        returns (bool success, bool result)
+    {
+        bytes memory encodedParams = abi.encodeWithSelector(_INTERFACE_ID_ERC165, interfaceId);
+
+        // solhint-disable-next-line no-inline-assembly
+        assembly {
+            let encodedParams_data := add(0x20, encodedParams)
+            let encodedParams_size := mload(encodedParams)
+
+            let output := mload(0x40)    // Find empty storage location using "free memory pointer"
+            mstore(output, 0x0)
+
+            success := staticcall(
+                30000,                   // 30k gas
+                account,                 // To addr
+                encodedParams_data,
+                encodedParams_size,
+                output,
+                0x20                     // Outputs are 32 bytes long
+            )
+
+            result := mload(output)      // Load the result
+        }
     }
-  }
 }

contracts/introspection/IERC165.sol

@@ -1,19 +1,15 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
 /**
  * @title IERC165
- * @dev https://github.com/ethereum/EIPs/blob/master/EIPS/eip-165.md
+ * @dev https://eips.ethereum.org/EIPS/eip-165
  */
 interface IERC165 {
-
-  /**
-   * @notice Query if a contract implements an interface
-   * @param interfaceId The interface identifier, as specified in ERC-165
-   * @dev Interface identification is specified in ERC-165. This function
-   * uses less than 30,000 gas.
-   */
-  function supportsInterface(bytes4 interfaceId)
-    external
-    view
-    returns (bool);
+    /**
+     * @notice Query if a contract implements an interface
+     * @param interfaceId The interface identifier, as specified in ERC-165
+     * @dev Interface identification is specified in ERC-165. This function
+     * uses less than 30,000 gas.
+     */
+    function supportsInterface(bytes4 interfaceId) external view returns (bool);
 }

contracts/lifecycle/Pausable.sol

@@ -1,57 +1,62 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
 import "../access/roles/PauserRole.sol";
 
 /**
  * @title Pausable
  * @dev Base contract which allows children to implement an emergency stop mechanism.
  */
-contract Pausable is PauserRole {
-  event Paused(address account);
-  event Unpaused(address account);
+contract Pausable is Initializable, PauserRole {
+    event Paused(address account);
+    event Unpaused(address account);
 
-  bool private _paused;
+    bool private _paused;
 
-  constructor() internal {
-    _paused = false;
-  }
+    function initialize(address sender) public initializer {
+        PauserRole.initialize(sender);
 
-  /**
-   * @return true if the contract is paused, false otherwise.
-   */
-  function paused() public view returns(bool) {
-    return _paused;
-  }
+        _paused = false;
+    }
 
-  /**
-   * @dev Modifier to make a function callable only when the contract is not paused.
-   */
-  modifier whenNotPaused() {
-    require(!_paused);
-    _;
-  }
+    /**
+     * @return true if the contract is paused, false otherwise.
+     */
+    function paused() public view returns (bool) {
+        return _paused;
+    }
 
-  /**
-   * @dev Modifier to make a function callable only when the contract is paused.
-   */
-  modifier whenPaused() {
-    require(_paused);
-    _;
-  }
+    /**
+     * @dev Modifier to make a function callable only when the contract is not paused.
+     */
+    modifier whenNotPaused() {
+        require(!_paused);
+        _;
+    }
 
-  /**
-   * @dev called by the owner to pause, triggers stopped state
-   */
-  function pause() public onlyPauser whenNotPaused {
-    _paused = true;
-    emit Paused(msg.sender);
-  }
+    /**
+     * @dev Modifier to make a function callable only when the contract is paused.
+     */
+    modifier whenPaused() {
+        require(_paused);
+        _;
+    }
 
-  /**
-   * @dev called by the owner to unpause, returns to normal state
-   */
-  function unpause() public onlyPauser whenPaused {
-    _paused = false;
-    emit Unpaused(msg.sender);
-  }
+    /**
+     * @dev called by the owner to pause, triggers stopped state
+     */
+    function pause() public onlyPauser whenNotPaused {
+        _paused = true;
+        emit Paused(msg.sender);
+    }
+
+    /**
+     * @dev called by the owner to unpause, returns to normal state
+     */
+    function unpause() public onlyPauser whenPaused {
+        _paused = false;
+        emit Unpaused(msg.sender);
+    }
+
+    uint256[50] private ______gap;
 }

contracts/math/Math.sol

@@ -1,31 +1,31 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
 /**
  * @title Math
  * @dev Assorted math operations
  */
 library Math {
-  /**
-  * @dev Returns the largest of two numbers.
-  */
-  function max(uint256 a, uint256 b) internal pure returns (uint256) {
-    return a >= b ? a : b;
-  }
+    /**
+     * @dev Returns the largest of two numbers.
+     */
+    function max(uint256 a, uint256 b) internal pure returns (uint256) {
+        return a >= b ? a : b;
+    }
 
-  /**
-  * @dev Returns the smallest of two numbers.
-  */
-  function min(uint256 a, uint256 b) internal pure returns (uint256) {
-    return a < b ? a : b;
-  }
+    /**
+     * @dev Returns the smallest of two numbers.
+     */
+    function min(uint256 a, uint256 b) internal pure returns (uint256) {
+        return a < b ? a : b;
+    }
 
-  /**
-  * @dev Calculates the average of two numbers. Since these are integers,
-  * averages of an even and odd number cannot be represented, and will be
-  * rounded down.
-  */
-  function average(uint256 a, uint256 b) internal pure returns (uint256) {
-    // (a + b) / 2 can overflow, so we distribute
-    return (a / 2) + (b / 2) + ((a % 2 + b % 2) / 2);
-  }
+    /**
+     * @dev Calculates the average of two numbers. Since these are integers,
+     * averages of an even and odd number cannot be represented, and will be
+     * rounded down.
+     */
+    function average(uint256 a, uint256 b) internal pure returns (uint256) {
+        // (a + b) / 2 can overflow, so we distribute
+        return (a / 2) + (b / 2) + ((a % 2 + b % 2) / 2);
+    }
 }

contracts/math/SafeMath.sol

@@ -1,65 +1,65 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
 /**
  * @title SafeMath
- * @dev Math operations with safety checks that revert on error
+ * @dev Unsigned math operations with safety checks that revert on error
  */
 library SafeMath {
+    /**
+     * @dev Multiplies two unsigned integers, reverts on overflow.
+     */
+    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
+        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
+        // benefit is lost if 'b' is also tested.
+        // See: https://github.com/OpenZeppelin/openzeppelin-solidity/pull/522
+        if (a == 0) {
+            return 0;
+        }
 
-  /**
-  * @dev Multiplies two numbers, reverts on overflow.
-  */
-  function mul(uint256 a, uint256 b) internal pure returns (uint256) {
-    // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
-    // benefit is lost if 'b' is also tested.
-    // See: https://github.com/OpenZeppelin/openzeppelin-solidity/pull/522
-    if (a == 0) {
-      return 0;
+        uint256 c = a * b;
+        require(c / a == b);
+
+        return c;
     }
 
-    uint256 c = a * b;
-    require(c / a == b);
+    /**
+     * @dev Integer division of two unsigned integers truncating the quotient, reverts on division by zero.
+     */
+    function div(uint256 a, uint256 b) internal pure returns (uint256) {
+        // Solidity only automatically asserts when dividing by 0
+        require(b > 0);
+        uint256 c = a / b;
+        // assert(a == b * c + a % b); // There is no case in which this doesn't hold
 
-    return c;
-  }
+        return c;
+    }
 
-  /**
-  * @dev Integer division of two numbers truncating the quotient, reverts on division by zero.
-  */
-  function div(uint256 a, uint256 b) internal pure returns (uint256) {
-    require(b > 0); // Solidity only automatically asserts when dividing by 0
-    uint256 c = a / b;
-    // assert(a == b * c + a % b); // There is no case in which this doesn't hold
+    /**
+     * @dev Subtracts two unsigned integers, reverts on overflow (i.e. if subtrahend is greater than minuend).
+     */
+    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
+        require(b <= a);
+        uint256 c = a - b;
 
-    return c;
-  }
+        return c;
+    }
 
-  /**
-  * @dev Subtracts two numbers, reverts on overflow (i.e. if subtrahend is greater than minuend).
-  */
-  function sub(uint256 a, uint256 b) internal pure returns (uint256) {
-    require(b <= a);
-    uint256 c = a - b;
+    /**
+     * @dev Adds two unsigned integers, reverts on overflow.
+     */
+    function add(uint256 a, uint256 b) internal pure returns (uint256) {
+        uint256 c = a + b;
+        require(c >= a);
 
-    return c;
-  }
+        return c;
+    }
 
-  /**
-  * @dev Adds two numbers, reverts on overflow.
-  */
-  function add(uint256 a, uint256 b) internal pure returns (uint256) {
-    uint256 c = a + b;
-    require(c >= a);
-
-    return c;
-  }
-
-  /**
-  * @dev Divides two numbers and returns the remainder (unsigned integer modulo),
-  * reverts when dividing by zero.
-  */
-  function mod(uint256 a, uint256 b) internal pure returns (uint256) {
-    require(b != 0);
-    return a % b;
-  }
+    /**
+     * @dev Divides two unsigned integers and returns the remainder (unsigned integer modulo),
+     * reverts when dividing by zero.
+     */
+    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
+        require(b != 0);
+        return a % b;
+    }
 }

contracts/mocks/Acknowledger.sol

@@ -0,0 +1,19 @@
+pragma solidity ^0.5.2;
+
+contract Acknowledger {
+    event AcknowledgeFoo(uint256 a);
+    event AcknowledgeBarSingle(uint256 a);
+    event AcknowledgeBarDouble(uint256 a, uint256 b);
+
+    function foo(uint256 a) public {
+        emit AcknowledgeFoo(a);
+    }
+
+    function bar(uint256 a) public {
+        emit AcknowledgeBarSingle(a);
+    }
+
+    function bar(uint256 a, uint256 b) public {
+        emit AcknowledgeBarDouble(a, b);
+    }
+}

contracts/mocks/AddressImpl.sol

@@ -1,14 +1,9 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
 import "../utils/Address.sol";
 
 contract AddressImpl {
-  function isContract(address account)
-    external
-    view
-    returns (bool)
-  {
-    return Address.isContract(account); 
-  }
-  
+    function isContract(address account) external view returns (bool) {
+        return Address.isContract(account);
+    }
 }

contracts/mocks/AllowanceCrowdsaleImpl.sol

@@ -1,20 +1,13 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
 import "../token/ERC20/IERC20.sol";
 import "../crowdsale/emission/AllowanceCrowdsale.sol";
 
 contract AllowanceCrowdsaleImpl is AllowanceCrowdsale {
-
-  constructor (
-    uint256 rate,
-    address wallet,
-    IERC20 token,
-    address tokenWallet
-  )
-    public
-    Crowdsale(rate, wallet, token)
-    AllowanceCrowdsale(tokenWallet)
-  {
-  }
-
+    constructor (uint256 rate, address payable wallet, IERC20 token, address tokenWallet)
+        public
+    {
+        Crowdsale.initialize(rate, wallet, token);
+        AllowanceCrowdsale.initialize(tokenWallet);
+    }
 }

contracts/mocks/ArraysImpl.sol

@@ -1,18 +1,17 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
 import "../utils/Arrays.sol";
 
 contract ArraysImpl {
+    using Arrays for uint256[];
 
-  using Arrays for uint256[];
+    uint256[] private array;
 
-  uint256[] private array;
+    constructor (uint256[] memory _array) public {
+        array = _array;
+    }
 
-  constructor(uint256[] _array) public {
-    array = _array;
-  }
-
-  function findUpperBound(uint256 _element) external view returns (uint256) {
-    return array.findUpperBound(_element);
-  }
+    function findUpperBound(uint256 _element) external view returns (uint256) {
+        return array.findUpperBound(_element);
+    }
 }

contracts/mocks/CappedCrowdsaleImpl.sol

@@ -1,20 +1,13 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
 import "../token/ERC20/IERC20.sol";
 import "../crowdsale/validation/CappedCrowdsale.sol";
 
 contract CappedCrowdsaleImpl is CappedCrowdsale {
-
-  constructor (
-    uint256 rate,
-    address wallet,
-    IERC20 token,
-    uint256 cap
-  )
-    public
-    Crowdsale(rate, wallet, token)
-    CappedCrowdsale(cap)
-  {
-  }
-
+    constructor (uint256 rate, address payable wallet, IERC20 token, uint256 cap)
+        public
+    {
+        Crowdsale.initialize(rate, wallet, token);
+        CappedCrowdsale.initialize(cap);
+    }
 }

contracts/mocks/CapperRoleMock.sol

@@ -1,17 +1,22 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
 import "../access/roles/CapperRole.sol";
 
 contract CapperRoleMock is CapperRole {
-  function removeCapper(address account) public {
-    _removeCapper(account);
-  }
+    constructor() public {
+        CapperRole.initialize(msg.sender);
+    }
 
-  function onlyCapperMock() public view onlyCapper {
-  }
+    function removeCapper(address account) public {
+        _removeCapper(account);
+    }
 
-  // Causes a compilation error if super._removeCapper is not internal
-  function _removeCapper(address account) internal {
-    super._removeCapper(account);
-  }
+    function onlyCapperMock() public view onlyCapper {
+        // solhint-disable-previous-line no-empty-blocks
+    }
+
+    // Causes a compilation error if super._removeCapper is not internal
+    function _removeCapper(address account) internal {
+        super._removeCapper(account);
+    }
 }

contracts/mocks/ConditionalEscrowMock.sol

@@ -1,16 +1,20 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
 import "../payment/escrow/ConditionalEscrow.sol";
 
 // mock class using ConditionalEscrow
 contract ConditionalEscrowMock is ConditionalEscrow {
-  mapping(address => bool) private _allowed;
+    mapping(address => bool) private _allowed;
 
-  function setAllowed(address payee, bool allowed) public {
-    _allowed[payee] = allowed;
-  }
+    constructor() public {
+        ConditionalEscrow.initialize(msg.sender);
+    }
 
-  function withdrawalAllowed(address payee) public view returns (bool) {
-    return _allowed[payee];
-  }
+    function setAllowed(address payee, bool allowed) public {
+        _allowed[payee] = allowed;
+    }
+
+    function withdrawalAllowed(address payee) public view returns (bool) {
+        return _allowed[payee];
+    }
 }

contracts/mocks/ContextMock.sol

@@ -0,0 +1,27 @@
+pragma solidity ^0.5.0;
+
+import "../GSN/Context.sol";
+
+contract ContextMock is Context {
+    event Sender(address sender);
+
+    function msgSender() public {
+        emit Sender(_msgSender());
+    }
+
+    event Data(bytes data, uint256 integerValue, string stringValue);
+
+    function msgData(uint256 integerValue, string memory stringValue) public {
+        emit Data(_msgData(), integerValue, stringValue);
+    }
+}
+
+contract ContextMockCaller {
+    function callSender(ContextMock context) public {
+        context.msgSender();
+    }
+
+    function callData(ContextMock context, uint256 integerValue, string memory stringValue) public {
+        context.msgData(integerValue, stringValue);
+    }
+}

contracts/mocks/CounterImpl.sol

@@ -1,20 +0,0 @@
-pragma solidity ^0.4.24;
-
-import "../drafts/Counter.sol";
-
-contract CounterImpl {
-  using Counter for Counter.Counter;
-
-  uint256 public theId;
-
-  // use whatever key you want to track your counters
-  mapping(string => Counter.Counter) private _counters;
-
-  function doThing(string key)
-    public
-    returns (uint256)
-  {
-    theId = _counters[key].next();
-    return theId;
-  }
-}

contracts/mocks/CountersImpl.sol

@@ -0,0 +1,21 @@
+pragma solidity ^0.5.2;
+
+import "../drafts/Counters.sol";
+
+contract CountersImpl {
+    using Counters for Counters.Counter;
+
+    Counters.Counter private _counter;
+
+    function current() public view returns (uint256) {
+        return _counter.current();
+    }
+
+    function increment() public {
+        _counter.increment();
+    }
+
+    function decrement() public {
+        _counter.decrement();
+    }
+}

contracts/mocks/CrowdsaleMock.sol

@@ -1,9 +1,9 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
 import "../crowdsale/Crowdsale.sol";
 
 contract CrowdsaleMock is Crowdsale {
-  constructor(uint256 rate, address wallet, IERC20 token) public
-    Crowdsale(rate, wallet, token) {
-  }
+    constructor (uint256 rate, address payable wallet, IERC20 token) public {
+        Crowdsale.initialize(rate, wallet, token);
+    }
 }

contracts/mocks/DetailedERC20Mock.sol

@@ -1,15 +0,0 @@
-pragma solidity ^0.4.24;
-
-import "../token/ERC20/ERC20.sol";
-import "../token/ERC20/ERC20Detailed.sol";
-
-contract ERC20DetailedMock is ERC20, ERC20Detailed {
-  constructor(
-    string name,
-    string symbol,
-    uint8 decimals
-  )
-    ERC20Detailed(name, symbol, decimals)
-    public
-  {}
-}

contracts/mocks/ECDSAMock.sol

@@ -1,23 +1,15 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
 import "../cryptography/ECDSA.sol";
 
 contract ECDSAMock {
-  using ECDSA for bytes32;
+    using ECDSA for bytes32;
 
-  function recover(bytes32 hash, bytes signature)
-    public
-    pure
-    returns (address)
-  {
-    return hash.recover(signature);
-  }
+    function recover(bytes32 hash, bytes memory signature) public pure returns (address) {
+        return hash.recover(signature);
+    }
 
-  function toEthSignedMessageHash(bytes32 hash)
-    public
-    pure
-    returns (bytes32)
-  {
-    return hash.toEthSignedMessageHash();
-  }
+    function toEthSignedMessageHash(bytes32 hash) public pure returns (bytes32) {
+        return hash.toEthSignedMessageHash();
+    }
 }

contracts/mocks/ERC165/ERC165InterfacesSupported.sol

@@ -1,66 +1,57 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
 import "../../introspection/IERC165.sol";
 
 /**
- * https://github.com/ethereum/EIPs/blob/master/EIPS/eip-214.md#specification
- * > Any attempts to make state-changing operations inside an execution instance with STATIC set to true will instead throw an exception.
+ * https://eips.ethereum.org/EIPS/eip-214#specification
+ * From the specification:
+ * > Any attempts to make state-changing operations inside an execution instance with STATIC set to true will instead
+ * throw an exception.
  * > These operations include [...], LOG0, LOG1, LOG2, [...]
  *
  * therefore, because this contract is staticcall'd we need to not emit events (which is how solidity-coverage works)
  * solidity-coverage ignores the /mocks folder, so we duplicate its implementation here to avoid instrumenting it
  */
 contract SupportsInterfaceWithLookupMock is IERC165 {
+    bytes4 public constant INTERFACE_ID_ERC165 = 0x01ffc9a7;
+    /*
+     * 0x01ffc9a7 ===
+     *     bytes4(keccak256('supportsInterface(bytes4)'))
+     */
 
-  bytes4 public constant InterfaceId_ERC165 = 0x01ffc9a7;
-  /**
-   * 0x01ffc9a7 ===
-   *   bytes4(keccak256('supportsInterface(bytes4)'))
-   */
+    /**
+     * @dev a mapping of interface id to whether or not it's supported
+     */
+    mapping(bytes4 => bool) private _supportedInterfaces;
 
-  /**
-   * @dev a mapping of interface id to whether or not it's supported
-   */
-  mapping(bytes4 => bool) private _supportedInterfaces;
+    /**
+     * @dev A contract implementing SupportsInterfaceWithLookup
+     * implement ERC165 itself
+     */
+    constructor () public {
+        _registerInterface(INTERFACE_ID_ERC165);
+    }
 
-  /**
-   * @dev A contract implementing SupportsInterfaceWithLookup
-   * implement ERC165 itself
-   */
-  constructor()
-    public
-  {
-    _registerInterface(InterfaceId_ERC165);
-  }
+    /**
+     * @dev implement supportsInterface(bytes4) using a lookup table
+     */
+    function supportsInterface(bytes4 interfaceId) external view returns (bool) {
+        return _supportedInterfaces[interfaceId];
+    }
 
-  /**
-   * @dev implement supportsInterface(bytes4) using a lookup table
-   */
-  function supportsInterface(bytes4 interfaceId)
-    external
-    view
-    returns (bool)
-  {
-    return _supportedInterfaces[interfaceId];
-  }
-
-  /**
-   * @dev private method for registering an interface
-   */
-  function _registerInterface(bytes4 interfaceId)
-    internal
-  {
-    require(interfaceId != 0xffffffff);
-    _supportedInterfaces[interfaceId] = true;
-  }
+    /**
+     * @dev private method for registering an interface
+     */
+    function _registerInterface(bytes4 interfaceId) internal {
+        require(interfaceId != 0xffffffff);
+        _supportedInterfaces[interfaceId] = true;
+    }
 }
 
 contract ERC165InterfacesSupported is SupportsInterfaceWithLookupMock {
-  constructor (bytes4[] interfaceIds)
-    public
-  {
-    for (uint256 i = 0; i < interfaceIds.length; i++) {
-      _registerInterface(interfaceIds[i]);
+    constructor (bytes4[] memory interfaceIds) public {
+        for (uint256 i = 0; i < interfaceIds.length; i++) {
+            _registerInterface(interfaceIds[i]);
+        }
     }
-  }
 }

contracts/mocks/ERC165/ERC165NotSupported.sol

@@ -1,5 +1,5 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
 contract ERC165NotSupported {
-
+    // solhint-disable-previous-line no-empty-blocks
 }

contracts/mocks/ERC165CheckerMock.sol

@@ -1,31 +1,19 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
 import "../introspection/ERC165Checker.sol";
 
 contract ERC165CheckerMock {
-  using ERC165Checker for address;
+    using ERC165Checker for address;
 
-  function supportsERC165(address account)
-    public
-    view
-    returns (bool)
-  {
-    return account._supportsERC165();
-  }
+    function supportsERC165(address account) public view returns (bool) {
+        return account._supportsERC165();
+    }
 
-  function supportsInterface(address account, bytes4 interfaceId)
-    public
-    view
-    returns (bool)
-  {
-    return account._supportsInterface(interfaceId);
-  }
+    function supportsInterface(address account, bytes4 interfaceId) public view returns (bool) {
+        return account._supportsInterface(interfaceId);
+    }
 
-  function supportsAllInterfaces(address account, bytes4[] interfaceIds)
-    public
-    view
-    returns (bool)
-  {
-    return account._supportsAllInterfaces(interfaceIds);
-  }
+    function supportsAllInterfaces(address account, bytes4[] memory interfaceIds) public view returns (bool) {
+        return account._supportsAllInterfaces(interfaceIds);
+    }
 }

contracts/mocks/ERC165Mock.sol

@@ -1,11 +1,13 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
 import "../introspection/ERC165.sol";
 
 contract ERC165Mock is ERC165 {
-  function registerInterface(bytes4 interfaceId)
-    public
-  {
-    _registerInterface(interfaceId);
-  }
+    constructor() public {
+        ERC165.initialize();
+    }
+
+    function registerInterface(bytes4 interfaceId) public {
+        _registerInterface(interfaceId);
+    }
 }

contracts/mocks/ERC20BurnableMock.sol

@@ -1,11 +1,9 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
 import "../token/ERC20/ERC20Burnable.sol";
 
 contract ERC20BurnableMock is ERC20Burnable {
-
-  constructor(address initialAccount, uint256 initialBalance) public {
-    _mint(initialAccount, initialBalance);
-  }
-
+    constructor(address initialAccount, uint256 initialBalance) public {
+        _mint(initialAccount, initialBalance);
+    }
 }

contracts/mocks/ERC20CappedMock.sol

@@ -0,0 +1,13 @@
+pragma solidity ^0.5.0;
+
+import "../token/ERC20/ERC20Capped.sol";
+import "./MinterRoleMock.sol";
+
+
+contract ERC20CappedMock is ERC20Capped, MinterRoleMock {
+
+    constructor(uint256 cap) public {
+        ERC20Capped.initialize(cap, msg.sender);
+    }
+
+}

contracts/mocks/ERC20DetailedMock.sol

@@ -0,0 +1,12 @@
+pragma solidity ^0.5.2;
+
+import "../token/ERC20/ERC20.sol";
+import "../token/ERC20/ERC20Detailed.sol";
+
+contract ERC20DetailedMock is ERC20, ERC20Detailed {
+    constructor (string memory name, string memory symbol, uint8 decimals)
+        public
+    {
+        ERC20Detailed.initialize(name, symbol, decimals);
+    }
+}

contracts/mocks/ERC20MetadataMock.sol

@@ -0,0 +1,14 @@
+pragma solidity ^0.5.0;
+
+import "../token/ERC20/ERC20.sol";
+import "../drafts/ERC1046/ERC20Metadata.sol";
+
+contract ERC20MetadataMock is ERC20, ERC20Metadata {
+    constructor (string memory tokenURI) public {
+        ERC20Metadata.initialize(tokenURI);
+    }
+
+    function setTokenURI(string memory tokenURI) public {
+        _setTokenURI(tokenURI);
+    }
+}

contracts/mocks/ERC20MigratorMock.sol

@@ -0,0 +1,12 @@
+pragma solidity ^0.5.0;
+
+import "../drafts/ERC20Migrator.sol";
+
+
+contract ERC20MigratorMock is ERC20Migrator {
+
+    constructor(IERC20 legacyToken) public {
+        ERC20Migrator.initialize(legacyToken);
+    }
+
+}

contracts/mocks/ERC20MintableMock.sol

@@ -1,7 +1,10 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
 import "../token/ERC20/ERC20Mintable.sol";
 import "./MinterRoleMock.sol";
 
 contract ERC20MintableMock is ERC20Mintable, MinterRoleMock {
+    constructor() public {
+        ERC20Mintable.initialize(msg.sender);
+    }
 }

contracts/mocks/ERC20Mock.sol

@@ -1,24 +1,26 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
 import "../token/ERC20/ERC20.sol";
 
 // mock class using ERC20
 contract ERC20Mock is ERC20 {
+    constructor (address initialAccount, uint256 initialBalance) public {
+        _mint(initialAccount, initialBalance);
+    }
 
-  constructor(address initialAccount, uint256 initialBalance) public {
-    _mint(initialAccount, initialBalance);
-  }
+    function mint(address account, uint256 amount) public {
+        _mint(account, amount);
+    }
 
-  function mint(address account, uint256 amount) public {
-    _mint(account, amount);
-  }
+    function burn(address account, uint256 amount) public {
+        _burn(account, amount);
+    }
 
-  function burn(address account, uint256 amount) public {
-    _burn(account, amount);
-  }
-
-  function burnFrom(address account, uint256 amount) public {
-    _burnFrom(account, amount);
-  }
+    function burnFrom(address account, uint256 amount) public {
+        _burnFrom(account, amount);
+    }
 
+    function approveInternal(address owner, address spender, uint256 value) public {
+        _approve(owner, spender, value);
+    }
 }

contracts/mocks/ERC20PausableMock.sol

@@ -1,13 +1,12 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
 import "../token/ERC20/ERC20Pausable.sol";
 import "./PauserRoleMock.sol";
 
 // mock class using ERC20Pausable
 contract ERC20PausableMock is ERC20Pausable, PauserRoleMock {
-
-  constructor(address initialAccount, uint initialBalance) public {
-    _mint(initialAccount, initialBalance);
-  }
-
+    constructor (address initialAccount, uint initialBalance) public {
+        ERC20Pausable.initialize(msg.sender);
+        _mint(initialAccount, initialBalance);
+    }
 }

contracts/mocks/ERC20SnapshotMock.sol

@@ -0,0 +1,18 @@
+pragma solidity ^0.5.2;
+
+import "../drafts/ERC20Snapshot.sol";
+
+
+contract ERC20SnapshotMock is ERC20Snapshot {
+    constructor(address initialAccount, uint256 initialBalance) public {
+        _mint(initialAccount, initialBalance);
+    }
+
+    function mint(address account, uint256 amount) public {
+        _mint(account, amount);
+    }
+
+    function burn(address account, uint256 amount) public {
+        _burn(account, amount);
+    }
+}

contracts/mocks/ERC20WithMetadataMock.sol

@@ -1,11 +0,0 @@
-pragma solidity ^0.4.24;
-
-import "../token/ERC20/ERC20.sol";
-import "../drafts/ERC1046/TokenMetadata.sol";
-
-contract ERC20WithMetadataMock is ERC20, ERC20WithMetadata {
-  constructor(string tokenURI) public
-    ERC20WithMetadata(tokenURI)
-  {
-  }
-}

contracts/mocks/ERC721FullMock.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
 import "../token/ERC721/ERC721Full.sol";
 import "../token/ERC721/ERC721Mintable.sol";
@@ -7,26 +7,27 @@ import "../token/ERC721/ERC721Burnable.sol";
 
 /**
  * @title ERC721FullMock
- * This mock just provides a public mint and burn functions for testing purposes,
- * and a public setter for metadata URI
+ * This mock just provides public functions for setting metadata URI, getting all tokens of an owner,
+ * checking token existence, removal of a token from an address
  */
-contract ERC721FullMock
-  is ERC721Full, ERC721Mintable, ERC721MetadataMintable, ERC721Burnable {
+contract ERC721FullMock is ERC721Full, ERC721Mintable, ERC721MetadataMintable, ERC721Burnable {
+    constructor (string memory name, string memory symbol) public {
+        ERC721.initialize();
+        ERC721Metadata.initialize(name, symbol);
+        ERC721Enumerable.initialize();
+        ERC721Mintable.initialize(msg.sender);
+        ERC721MetadataMintable.initialize(msg.sender);
+    }
 
-  constructor(string name, string symbol) public
-    ERC721Mintable()
-    ERC721Full(name, symbol)
-  {}
+    function exists(uint256 tokenId) public view returns (bool) {
+        return _exists(tokenId);
+    }
 
-  function exists(uint256 tokenId) public view returns (bool) {
-    return _exists(tokenId);
-  }
+    function tokensOfOwner(address owner) public view returns (uint256[] memory) {
+        return _tokensOfOwner(owner);
+    }
 
-  function setTokenURI(uint256 tokenId, string uri) public {
-    _setTokenURI(tokenId, uri);
-  }
-
-  function removeTokenFrom(address from, uint256 tokenId) public {
-    _removeTokenFrom(from, tokenId);
-  }
+    function setTokenURI(uint256 tokenId, string memory uri) public {
+        _setTokenURI(tokenId, uri);
+    }
 }

contracts/mocks/ERC721MintableBurnableImpl.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
 import "../token/ERC721/ERC721Full.sol";
 import "../token/ERC721/ERC721Mintable.sol";
@@ -8,13 +8,12 @@ import "../token/ERC721/ERC721Burnable.sol";
 /**
  * @title ERC721MintableBurnableImpl
  */
-contract ERC721MintableBurnableImpl
-  is ERC721Full, ERC721Mintable, ERC721MetadataMintable, ERC721Burnable {
-
-  constructor()
-    ERC721Mintable()
-    ERC721Full("Test", "TEST")
-    public
-  {
-  }
+contract ERC721MintableBurnableImpl is ERC721Full, ERC721Mintable, ERC721MetadataMintable, ERC721Burnable {
+    constructor () public {
+        ERC721.initialize();
+        ERC721Metadata.initialize("Test", "TEST");
+        ERC721Enumerable.initialize();
+        ERC721Mintable.initialize(msg.sender);
+        ERC721MetadataMintable.initialize(msg.sender);
+    }
 }

contracts/mocks/ERC721Mock.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.2;
 
 import "../token/ERC721/ERC721.sol";
 
@@ -7,11 +7,19 @@ import "../token/ERC721/ERC721.sol";
  * This mock just provides a public mint and burn functions for testing purposes
  */
 contract ERC721Mock is ERC721 {
-  function mint(address to, uint256 tokenId) public {
-    _mint(to, tokenId);
-  }
+    constructor() public {
+        ERC721.initialize();
+    }
 
-  function burn(uint256 tokenId) public {
-    _burn(ownerOf(tokenId), tokenId);
-  }
+    function mint(address to, uint256 tokenId) public {
+        _mint(to, tokenId);
+    }
+
+    function burn(address owner, uint256 tokenId) public {
+        _burn(owner, tokenId);
+    }
+
+    function burn(uint256 tokenId) public {
+        _burn(tokenId);
+    }
 }