4.3.3

Co-authored-by: Francisco Giordano <frangio.1@gmail.com>
(cherry picked from commit 4088540aef)

.circleci/config.yml

@@ -1,84 +0,0 @@
-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:10
-
-  - &cache_key_node_modules
-    key: v1-node_modules-{{ checksum "package-lock.json" }}
-
-jobs:
-  dependencies:
-    <<: *defaults
-    steps:
-      - checkout
-      - restore_cache:
-          <<: *cache_key_node_modules
-      - run:
-          name: Install npm dependencies and prepare
-          command: |
-            if [ ! -d node_modules ]; then
-              npm ci
-            else
-              npm run prepare
-            fi
-      - persist_to_workspace:
-          root: .
-          paths:
-            - node_modules
-            - build
-      - save_cache:
-          paths:
-            - node_modules
-          <<: *cache_key_node_modules
-
-  lint:
-    <<: *defaults
-    steps:
-      - checkout
-      - attach_workspace:
-          at: .
-      - run:
-          name: Linter
-          command: npm run lint
-  test:
-    <<: *defaults
-    steps:
-      - checkout
-      - attach_workspace:
-          at: .
-      - run:
-          name: Unit tests
-          command: npm run test
-
-  coverage:
-    <<: *defaults
-    steps:
-      - checkout
-      - attach_workspace:
-          at: .
-      - 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
-

.codecov.yml

@@ -1,3 +1,11 @@
 comment: off
+github_checks:
+  annotations: false
 coverage:
-  range: "100...100"
+  status:
+    patch:
+      default:
+        target: 95%
+    project:
+      default:
+        threshold: 1%

.dependabot/config.yml

@@ -1,7 +0,0 @@
-version: 1
-
-update_configs:
-  - package_manager: "javascript"
-    directory: "/"
-    update_schedule: "weekly"
-    version_requirement_updates: "increase_versions"

.editorconfig

@@ -8,7 +8,7 @@ charset = utf-8
 end_of_line = lf
 indent_style = space
 insert_final_newline = true
-trim_trailing_whitespace = true
+trim_trailing_whitespace = false
 max_line_length = 120
 
 [*.sol]
@@ -16,3 +16,6 @@ indent_size = 4
 
 [*.js]
 indent_size = 2
+
+[*.adoc]
+max_line_length = 0

.eslintrc

@@ -18,6 +18,8 @@
     "contract": false,
     "assert": false,
     "web3": false,
+    "usePlugin": false,
+    "extendEnvironment": false,
   },
   "rules": {
 

.github/ISSUE_TEMPLATE/feature_request.md

@@ -10,5 +10,5 @@ about: Suggest an idea for OpenZeppelin Contracts
 **📝 Details**
 <!-- Please describe your feature request in detail. -->
 
-<!-- Make sure that you have reviewed the OpenZeppelin Contributor Guidelines. -->
+<!-- Make sure that you have reviewed the OpenZeppelin Contracts Contributor Guidelines. -->
 <!-- https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/CONTRIBUTING.md -->

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,22 +1,20 @@
-<!-- 0. 🎉 Thank you for submitting a PR! -->
+<!-- Thank you for your interest in contributing to OpenZeppelin! -->
 
-<!-- 1. Does this close any open issues? Please list them below. -->
+<!-- Consider opening an issue for discussion prior to submitting a PR. -->
+<!-- New features will be merged faster if they were first discussed and designed with the team. -->
 
-<!-- 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 #???? <!-- Fill in with issue number -->
 
-Fixes #
+<!-- Describe the changes introduced in this pull request. -->
+<!-- Include any context necessary for understanding the PR's purpose. -->
 
-<!-- 2. Describe the changes introduced in this pull request. -->
-<!--    Include any context necessary for understanding the PR's purpose. -->
 
-<!-- 3. Before submitting, please make sure that you have:
-  - reviewed the OpenZeppelin Contributor Guidelines
-    (https://github.com/OpenZeppelin/openzeppelin-contracts/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.
--->
+#### PR Checklist
+
+<!-- Before merging the pull request all of the following must be complete. -->
+<!-- Feel free to submit a PR or Draft PR even if some items are pending. -->
+<!-- Some of the items may not apply. -->
+
+- [ ] Tests
+- [ ] Documentation
+- [ ] Changelog entry

.github/stale.yml

@@ -1,67 +0,0 @@
-# Configuration for probot-stale - https://github.com/probot/stale
-
-# Number of days of inactivity before an Issue or Pull Request becomes stale
-daysUntilStale: 15
-
-# Number of days of inactivity before an Issue or Pull Request with the stale label is closed.
-# Set to false to disable. If disabled, issues still need to be closed manually, but will remain marked as stale.
-daysUntilClose: 15
-
-# Issues or Pull Requests with these labels will never be considered stale. Set to `[]` to disable
-exemptLabels:
-  - on hold
-  - meta
-
-# Set to true to ignore issues in a project (defaults to false)
-exemptProjects: false
-
-# Set to true to ignore issues in a milestone (defaults to false)
-exemptMilestones: false
-
-# Set to true to ignore issues with an assignee (defaults to false)
-exemptAssignees: false
-
-# Label to use when marking as stale
-staleLabel: stale
-
-# Comment to post when marking as stale. Set to `false` to disable
-markComment: >
-  Hi all!
-
-  This Pull Request has not had any recent activity, is it still relevant? If so, what is blocking it?
-  Is there anything we can do to help move it forward?
-
-  Thanks!
-
-
-# Comment to post when removing the stale label.
-# unmarkComment: >
-#   Your comment here.
-
-# Comment to post when closing a stale Issue or Pull Request.
-closeComment: >
-  Hi folks!
-
-  This Pull Request is being closed as there was no response to the previous prompt.
-  However, please leave a comment whenever you're ready to resume, so it can be reopened.
-
-  Thanks again!
-
-
-# Limit the number of actions per hour, from 1-30. Default is 30
-limitPerRun: 30
-
-# Limit to only `issues` or `pulls`
-only: pulls
-
-# Optionally, specify configuration settings that are specific to just 'issues' or 'pulls':
-# pulls:
-#   daysUntilStale: 30
-#   markComment: >
-#     This pull request has been automatically marked as stale because it has not had
-#     recent activity. It will be closed if no further activity occurs. Thank you
-#     for your contributions.
-
-# issues:
-#   exemptLabels:
-#     - confirmed

.github/workflows/test.yml

@@ -0,0 +1,56 @@
+name: Test
+
+on:
+  push:
+    branches:
+      - master
+      - release-v*
+  pull_request: {}
+  workflow_dispatch: {}
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/setup-node@v2
+        with:
+          node-version: 12.x
+      - uses: actions/cache@v2
+        id: cache
+        with:
+          path: '**/node_modules'
+          key: npm-v2-${{ hashFiles('**/package-lock.json') }}
+          restore-keys: npm-v2-
+      - run: npm ci
+        if: steps.cache.outputs.cache-hit != 'true'
+      - run: npm run lint
+      - run: npm run test
+        env:
+          FORCE_COLOR: 1
+          ENABLE_GAS_REPORT: true
+      - run: npm run test:inheritance 
+      - name: Print gas report
+        run: cat gas-report.txt
+
+  coverage:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+        with:
+          fetch-depth: 2
+      - uses: actions/setup-node@v2
+        with:
+          node-version: 12.x
+      - uses: actions/cache@v2
+        id: cache
+        with:
+          path: '**/node_modules'
+          key: npm-v2-${{ hashFiles('**/package-lock.json') }}
+          restore-keys: npm-v2-
+      - run: npm ci
+        if: steps.cache.outputs.cache-hit != 'true'
+      - run: npm run coverage
+        env:
+          NODE_OPTIONS: --max_old_space_size=4096
+      - uses: codecov/codecov-action@v2

.github/workflows/upgradeable.yml

@@ -0,0 +1,23 @@
+name: Upgradeable Trigger
+
+on:
+  push:
+    branches:
+      - master
+      - release-v*
+
+jobs:
+  trigger:
+    runs-on: ubuntu-latest
+    steps:
+      - id: app
+        uses: getsentry/action-github-app-token@v1
+        with:
+          app_id: ${{ secrets.UPGRADEABLE_APP_ID }}
+          private_key: ${{ secrets.UPGRADEABLE_APP_PK }}
+      - run: |
+          curl -X POST \
+            https://api.github.com/repos/OpenZeppelin/openzeppelin-contracts-upgradeable/dispatches \
+            -H 'Accept: application/vnd.github.v3+json' \
+            -H 'Authorization: token ${{ steps.app.outputs.token }}' \
+            -d '{ "event_type": "Update", "client_payload": { "ref": "${{ github.ref }}" } }'

.gitignore

@@ -50,3 +50,10 @@ contracts/README.md
 
 # temporary artifact from solidity-coverage
 allFiredEvents
+.coverage_artifacts
+.coverage_cache
+.coverage_contracts
+
+# hardhat
+cache
+artifacts

.mocharc.js

@@ -0,0 +1,4 @@
+module.exports = {
+  require: 'hardhat/register',
+  timeout: 4000,
+};

.prettierrc

@@ -0,0 +1,11 @@
+{
+  "overrides": [
+    {
+      "files": "*.sol",
+      "options": {
+        "printWidth": 120,
+        "explicitTypes": "always"
+      }
+    }
+  ]
+}

.solcover.js

@@ -4,5 +4,12 @@ module.exports = {
     compileCommand: 'npm run compile',
     skipFiles: [
         'mocks',
-    ]
+    ],
+    providerOptions: {
+        default_balance_ether: '10000000000000000000000000',
+    },
+    mocha: {
+        fgrep: '[skip-on-coverage]',
+        invert: true,
+    },
 }

.solhint.json

@@ -1,10 +1,14 @@
 {
-  "extends": "solhint:recommended",
   "rules": {
-    "func-order": "off",
-    "mark-callable-contracts": "off",
-    "no-empty-blocks": "off",
-    "compiler-version": ["error", "^0.6.0"],
-    "private-vars-leading-underscore": "error"
+    "no-unused-vars": "error",
+    "const-name-snakecase": "error",
+    "contract-name-camelcase": "error",
+    "event-name-camelcase": "error",
+    "func-name-mixedcase": "error",
+    "func-param-name-mixedcase": "error",
+    "modifier-name-mixedcase": "error",
+    "private-vars-leading-underscore": "error",
+    "var-name-mixedcase": "error",
+    "imports-on-top": "error"
   }
 }

CHANGELOG.md

@@ -1,5 +1,186 @@
 # Changelog
 
+## 4.3.3 (2021-11-11)
+
+ * `ERC1155Supply`: Handle `totalSupply` changes by hooking into `_beforeTokenTransfer` to ensure consistency of balances and supply during `IERC1155Receiver.onERC1155Received` calls.
+
+## 4.3.2 (2021-09-14)
+
+ * `UUPSUpgradeable`: Add modifiers to prevent `upgradeTo` and `upgradeToAndCall` being executed on any contract that is not the active ERC1967 proxy. This prevents these functions being called on implementation contracts or minimal ERC1167 clones, in particular.
+
+## 4.3.1 (2021-08-26)
+
+ * `TimelockController`: Add additional isOperationReady check.
+
+## 4.3.0 (2021-08-17)
+
+ * `ERC2771Context`: use private variable from storage to store the forwarder address. Fixes issues where `_msgSender()` was not callable from constructors. ([#2754](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2754))
+ * `EnumerableSet`: add `values()` functions that returns an array containing all values in a single call. ([#2768](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2768))
+ * `Governor`: added a modular system of `Governor` contracts based on `GovernorAlpha` and `GovernorBravo`. ([#2672](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2672))
+ * Add an `interfaces` folder containing solidity interfaces to final ERCs. ([#2517](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2517))
+ * `ECDSA`: add `tryRecover` functions that will not throw if the signature is invalid, and will return an error flag instead. ([#2661](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2661))
+ * `SignatureChecker`: Reduce gas usage of the `isValidSignatureNow` function for the "signature by EOA" case. ([#2661](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2661))
+
+## 4.2.0 (2021-06-30)
+
+ * `ERC20Votes`: add a new extension of the `ERC20` token with support for voting snapshots and delegation. ([#2632](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2632))
+ * `ERC20VotesComp`: Variant of `ERC20Votes` that is compatible with Compound's `Comp` token interface but restricts supply to `uint96`. ([#2706](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2706))
+ * `ERC20Wrapper`: add a new extension of the `ERC20` token which wraps an underlying token. Deposit and withdraw guarantee that the total supply is backed by a corresponding amount of underlying token. ([#2633](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2633))
+ * Enumerables: Improve gas cost of removal in `EnumerableSet` and `EnumerableMap`.
+ * Enumerables: Improve gas cost of lookup in `EnumerableSet` and `EnumerableMap`.
+ * `Counter`: add a reset method. ([#2678](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2678))
+ * Tokens: Wrap definitely safe subtractions in `unchecked` blocks.
+ * `Math`: Add a `ceilDiv` method for performing ceiling division.
+ * `ERC1155Supply`: add a new `ERC1155` extension that keeps track of the totalSupply of each tokenId. ([#2593](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2593))
+ * `BitMaps`: add a new `BitMaps` library that provides a storage efficient datastructure for `uint256` to `bool` mapping with contiguous keys. ([#2710](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2710))
+
+### Breaking Changes
+
+ * `ERC20FlashMint` is no longer a Draft ERC. ([#2673](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2673)))
+
+**How to update:** Change your import paths by removing the `draft-` prefix from `@openzeppelin/contracts/token/ERC20/extensions/draft-ERC20FlashMint.sol`.
+
+> See [Releases and Stability: Drafts](https://docs.openzeppelin.com/contracts/4.x/releases-stability#drafts).
+
+## 4.1.0 (2021-04-29)
+
+ * `IERC20Metadata`: add a new extended interface that includes the optional `name()`, `symbol()` and `decimals()` functions. ([#2561](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2561))
+ * `ERC777`: make reception acquirement optional in `_mint`. ([#2552](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2552))
+ * `ERC20Permit`: add a `_useNonce` to enable further usage of ERC712 signatures. ([#2565](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2565))
+ * `ERC20FlashMint`: add an implementation of the ERC3156 extension for flash-minting ERC20 tokens. ([#2543](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2543))
+ * `SignatureChecker`: add a signature verification library that supports both EOA and ERC1271 compliant contracts as signers. ([#2532](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2532))
+ * `Multicall`: add abstract contract with `multicall(bytes[] calldata data)` function to bundle multiple calls together ([#2608](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2608))
+ * `ECDSA`: add support for ERC2098 short-signatures. ([#2582](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2582))
+ * `AccessControl`: add a `onlyRole` modifier to restrict specific function to callers bearing a specific role. ([#2609](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2609))
+ * `StorageSlot`: add a library for reading and writing primitive types to specific storage slots. ([#2542](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2542))
+ * UUPS Proxies: add `UUPSUpgradeable` to implement the UUPS proxy pattern together with `EIP1967Proxy`. ([#2542](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2542))
+
+### Breaking changes
+
+This release includes two small breaking changes in `TimelockController`.
+
+1. The `onlyRole` modifier in this contract was designed to let anyone through if the role was granted to `address(0)`,
+   allowing the possibility to to make a role "open", which can be used for `EXECUTOR_ROLE`. This modifier is now
+   replaced by `AccessControl.onlyRole`, which does not have this ability. The previous behavior was moved to the
+   modifier `TimelockController.onlyRoleOrOpenRole`.
+2. It was possible to make `PROPOSER_ROLE` an open role (as described in the previous item) if it was granted to
+   `address(0)`. This would affect the `schedule`, `scheduleBatch`, and `cancel` operations in `TimelockController`.
+   This ability was removed as it does not make sense to open up the `PROPOSER_ROLE` in the same way that it does for
+   `EXECUTOR_ROLE`.
+
+## 4.0.0 (2021-03-23)
+
+ * Now targeting the 0.8.x line of Solidity compilers. For 0.6.x (resp 0.7.x) support, use version 3.4.0 (resp 3.4.0-solc-0.7) of OpenZeppelin.
+ * `Context`: making `_msgData` return `bytes calldata` instead of `bytes memory` ([#2492](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2492))
+ * `ERC20`: removed the `_setDecimals` function and the storage slot associated to decimals. ([#2502](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2502))
+ * `Strings`: addition of a `toHexString` function.  ([#2504](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2504))
+ * `EnumerableMap`: change implementation to optimize for `key → value` lookups instead of enumeration. ([#2518](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2518))
+ * `GSN`: deprecate GSNv1 support in favor of upcoming support for GSNv2. ([#2521](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2521))
+ * `ERC165`: remove uses of storage in the base ERC165 implementation. ERC165 based contracts now use storage-less virtual functions. Old behavior remains available in the `ERC165Storage` extension. ([#2505](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2505))
+ * `Initializable`: make initializer check stricter during construction. ([#2531](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2531))
+ * `ERC721`: remove enumerability of tokens from the base implementation. This feature is now provided separately through the `ERC721Enumerable` extension. ([#2511](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2511))
+ * `AccessControl`: removed enumerability by default for a more lightweight contract. It is now opt-in through `AccessControlEnumerable`. ([#2512](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2512))
+ * Meta Transactions: add `ERC2771Context` and a `MinimalForwarder` for meta-transactions. ([#2508](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2508))
+ * Overall reorganization of the contract folder to improve clarity and discoverability. ([#2503](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2503))
+ * `ERC20Capped`: optimize gas usage by enforcing the check directly in `_mint`. ([#2524](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2524))
+ * Rename `UpgradeableProxy` to `ERC1967Proxy`. ([#2547](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2547))
+ * `ERC777`: optimize the gas costs of the constructor. ([#2551](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2551))
+ * `ERC721URIStorage`: add a new extension that implements the `_setTokenURI` behavior as it was available in 3.4.0. ([#2555](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2555))
+ * `AccessControl`: added ERC165 interface detection. ([#2562](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2562))
+ * `ERC1155`: make `uri` public so overloading function can call it using super. ([#2576](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2576))
+
+### Bug fixes for beta releases
+
+ * `AccessControlEnumerable`: Fixed `renounceRole` not updating enumerable set of addresses for a role. ([#2572](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2572))
+
+### How to upgrade from 3.x
+
+Since this version has moved a few contracts to different directories, users upgrading from a previous version will need to adjust their import statements. To make this easier, the package includes a script that will migrate import statements automatically. After upgrading to the latest version of the package, run:
+
+```
+npx openzeppelin-contracts-migrate-imports
+```
+
+Make sure you're using git or another version control system to be able to recover from any potential error in our script.
+
+### How to upgrade from 4.0-beta.x
+
+Some further changes have been done between the different beta iterations. Transitions made during this period are configured in the `migrate-imports` script. Consequently, you can upgrade from any previous 4.0-beta.x version using the same script as described in the *How to upgrade from 3.x* section.
+
+## 3.4.0 (2021-02-02)
+
+ * `BeaconProxy`: added new kind of proxy that allows simultaneous atomic upgrades. ([#2411](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2411))
+ * `EIP712`: added helpers to verify EIP712 typed data signatures on chain. ([#2418](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2418))
+ * `ERC20Permit`: added an implementation of the ERC20 permit extension for gasless token approvals. ([#2237](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2237))
+ * Presets: added token presets with preminted fixed supply `ERC20PresetFixedSupply` and `ERC777PresetFixedSupply`. ([#2399](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2399))
+ * `Address`: added `functionDelegateCall`, similar to the existing `functionCall`. ([#2333](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2333))
+ * `Clones`: added a library for deploying EIP 1167 minimal proxies. ([#2449](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2449))
+ * `Context`: moved from `contracts/GSN` to `contracts/utils`. ([#2453](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2453))
+ * `PaymentSplitter`: replace usage of `.transfer()` with `Address.sendValue` for improved compatibility with smart wallets. ([#2455](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2455))
+ * `UpgradeableProxy`: bubble revert reasons from initialization calls. ([#2454](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2454))
+ * `SafeMath`: fix a memory allocation issue by adding new `SafeMath.tryOp(uint,uint)→(bool,uint)` functions. `SafeMath.op(uint,uint,string)→uint` are now deprecated. ([#2462](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2462))
+ * `EnumerableMap`: fix a memory allocation issue by adding new `EnumerableMap.tryGet(uint)→(bool,address)` functions. `EnumerableMap.get(uint)→string` is now deprecated. ([#2462](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2462))
+ * `ERC165Checker`: added batch `getSupportedInterfaces`. ([#2469](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2469))
+ * `RefundEscrow`: `beneficiaryWithdraw` will forward all available gas to the beneficiary. ([#2480](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2480))
+ * Many view and pure functions have been made virtual to customize them via overrides. In many cases this will not imply that other functions in the contract will automatically adapt to the overridden definitions. People who wish to override should consult the source code to understand the impact and if they need to override any additional functions to achieve the desired behavior.
+
+### Security Fixes
+
+ * `ERC777`: fix potential reentrancy issues for custom extensions to `ERC777`. ([#2483](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2483))
+
+If you're using our implementation of ERC777 from version 3.3.0 or earlier, and you define a custom `_beforeTokenTransfer` function that writes to a storage variable, you may be vulnerable to a reentrancy attack. If you're affected and would like assistance please write to security@openzeppelin.com. [Read more in the pull request.](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2483)
+
+## 3.3.0 (2020-11-26)
+
+ * Now supports both Solidity 0.6 and 0.7. Compiling with solc 0.7 will result in warnings. Install the `solc-0.7` tag to compile without warnings.
+ * `Address`: added `functionStaticCall`, similar to the existing `functionCall`. ([#2333](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2333))
+ * `TimelockController`: added a contract to augment access control schemes with a delay. ([#2354](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2354))
+ * `EnumerableSet`: added `Bytes32Set`, for sets of `bytes32`. ([#2395](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2395))
+
+## 3.2.2-solc-0.7 (2020-10-28)
+ * Resolve warnings introduced by Solidity 0.7.4. ([#2396](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2396))
+
+## 3.2.1-solc-0.7 (2020-09-15)
+ * `ERC777`: Remove a warning about function state visibility in Solidity 0.7. ([#2327](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2327))
+
+## 3.2.0 (2020-09-10)
+
+### New features
+ * Proxies: added the proxy contracts from OpenZeppelin SDK. ([#2335](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2335))
+
+#### Proxy changes with respect to OpenZeppelin SDK
+
+Aside from upgrading them from Solidity 0.5 to 0.6, we've changed a few minor things from the proxy contracts as they were found in OpenZeppelin SDK.
+
+- `UpgradeabilityProxy` was renamed to `UpgradeableProxy`.
+- `AdminUpgradeabilityProxy` was renamed to `TransparentUpgradeableProxy`.
+- `Proxy._willFallback` was renamed to `Proxy._beforeFallback`.
+- `UpgradeabilityProxy._setImplementation` and `AdminUpgradeabilityProxy._setAdmin` were made private.
+
+### Improvements
+ * `Address.isContract`: switched from `extcodehash` to `extcodesize` for less gas usage. ([#2311](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2311))
+
+### Breaking changes
+ * `ERC20Snapshot`: switched to using `_beforeTokenTransfer` hook instead of overriding ERC20 operations. ([#2312](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2312))
+
+This small change in the way we implemented `ERC20Snapshot` may affect users who are combining this contract with
+other ERC20 flavors, since it no longer overrides `_transfer`, `_mint`, and `_burn`. This can result in having to remove Solidity `override(...)` specifiers in derived contracts for these functions, and to instead have to add it for `_beforeTokenTransfer`. See [Using Hooks](https://docs.openzeppelin.com/contracts/3.x/extending-contracts#using-hooks) in the documentation.
+
+## 3.1.0 (2020-06-23)
+
+### New features
+ * `SafeCast`: added functions to downcast signed integers (e.g. `toInt32`), improving usability of `SignedSafeMath`. ([#2243](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2243))
+ * `functionCall`: new helpers that replicate Solidity's function call semantics, reducing the need to rely on `call`. ([#2264](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2264))
+ * `ERC1155`: added support for a base implementation, non-standard extensions and a preset contract. ([#2014](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2014), [#2230](https://github.com/OpenZeppelin/openzeppelin-contracts/issues/2230))
+
+### Improvements
+ * `ReentrancyGuard`: reduced overhead of using the `nonReentrant` modifier. ([#2171](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2171))
+ * `AccessControl`: added a `RoleAdminChanged` event to `_setAdminRole`. ([#2214](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2214))
+ * Made all `public` functions in the token preset contracts `virtual`. ([#2257](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2257))
+
+### Deprecations
+ * `SafeERC20`: deprecated `safeApprove`. ([#2268](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2268))
+
 ## 3.0.2 (2020-06-08)
 
 ### Improvements

CODE_STYLE.md

@@ -1,69 +0,0 @@
-# Code Style
-
-We value clean code and consistency, and those are prerequisites for us to
-include new code in the repository. Before proposing a change, please read this
-document and take some time to familiarize yourself with the style of the
-existing codebase.
-
-## Solidity code
-
-In order to be consistent with all the other Solidity projects, we follow the
-[official recommendations documented in the Solidity style guide](http://solidity.readthedocs.io/en/latest/style-guide.html).
-
-Any exception or additions specific to our project are documented below.
-
-### Naming
-
-* Try to avoid acronyms and abbreviations.
-
-* All state variables should be private.
-
-* Private state variables should have an underscore prefix.
-
-    ```
-    contract TestContract {
-      uint256 private _privateVar;
-      uint256 internal _internalVar;
-    }
-    ```
-
-* Parameters must not be prefixed with an underscore.
-
-    ```
-    function test(uint256 testParameter1, uint256 testParameter2) {
-    ...
-    }
-    ```
-
-* Internal and private functions should have an underscore prefix.
-
-    ```
-    function _testInternal() internal {
-      ...
-    }
-    ```
-
-    ```
-    function _testPrivate() private {
-      ...
-    }
-    ```
-
-* Events should be emitted immediately after the state change that they
-  represent, and consequently they should be named in past tense.
-
-    ```
-    function _burn(address _who, uint256 _value) internal {
-      super._burn(_who, _value);
-      emit TokensBurned(_who, _value);
-    }
-    ```
-
-  Some standards (e.g. ERC20) use present tense, and in those cases the
-  standard specification prevails.
-  
-* Interface names should have a capital I prefix.
-
-    ```
-    interface IERC777 {
-    ```

CONTRIBUTING.md

@@ -44,21 +44,14 @@ npm test
 npm run lint
 ```
 
-or you can simply run CircleCI locally
-```bash
-circleci local execute --job build
-circleci local execute --job test
-```
-*Note*: requires installing CircleCI and docker locally on your machine.
-
 5) Go to [github.com/OpenZeppelin/openzeppelin-contracts](https://github.com/OpenZeppelin/openzeppelin-contracts) in your web browser and issue a new pull request.
 
 *IMPORTANT* Read the PR template very carefully and make sure to follow all the instructions. These instructions
 refer to some very important conditions that your PR must meet in order to be accepted, such as making sure that all tests pass, JS linting tests pass, Solidity linting tests pass, etc.
 
-6) Maintainers will review your code and possibly ask for changes before your code is pulled in to the main repository. We'll check that all tests pass, review the coding style, and check for general code correctness. If everything is OK, we'll merge your pull request and your code will be part of OpenZeppelin.
+6) Maintainers will review your code and possibly ask for changes before your code is pulled in to the main repository. We'll check that all tests pass, review the coding style, and check for general code correctness. If everything is OK, we'll merge your pull request and your code will be part of OpenZeppelin Contracts.
 
-*IMPORTANT* Please pay attention to the maintainer's feedback, since its a necessary step to keep up with the standards OpenZeppelin attains to.
+*IMPORTANT* Please pay attention to the maintainer's feedback, since its a necessary step to keep up with the standards OpenZeppelin Contracts attains to.
 
 ## All set!
 

DOCUMENTATION.md

@@ -10,7 +10,7 @@ program that extracts the API Reference from source code.
 
 The [`docs.openzeppelin.com`](https://github.com/OpenZeppelin/docs.openzeppelin.com)
 repository hosts the configuration for the entire site, which includes
-documetation for all of the OpenZeppelin projects.
+documentation for all of the OpenZeppelin projects.
 
-To run the docs locally you should run `npm run docs start` on this
+To run the docs locally you should run `npm run docs:watch` on this
 repository.

GUIDELINES.md

@@ -1,7 +1,7 @@
 Design Guidelines
 =======
 
-These are some global design goals in OpenZeppelin.
+These are some global design goals in OpenZeppelin Contracts.
 
 #### D0 - Security in Depth
 We strive to provide secure, tested, audited code. To achieve this, we need to match intention with function. Thus, documentation, code clarity, community review and security discussions are fundamental.
@@ -28,37 +28,78 @@ Consistency on the way classes are used is paramount to an easier understanding
 #### D6 - Regular Audits
 Following good programming practices is a way to reduce the risk of vulnerabilities, but professional code audits are still needed. We will perform regular code audits on major releases, and hire security professionals to provide independent review.
 
-## Style Guidelines
+# Style Guidelines
 
-The design guidelines have quite a high abstraction level. These style guidelines are more concrete and easier to apply, and also more opinionated.
+The design guidelines have quite a high abstraction level. These style guidelines are more concrete and easier to apply, and also more opinionated. We value clean code and consistency, and those are prerequisites for us to include new code in the repository. Before proposing a change, please read these guidelines and take some time to familiarize yourself with the style of the existing codebase.
 
-### General
+## Solidity code
 
-#### G0 - Default to Solidity's official style guide.
+In order to be consistent with all the other Solidity projects, we follow the
+[official recommendations documented in the Solidity style guide](http://solidity.readthedocs.io/en/latest/style-guide.html).
 
-Follow the official Solidity style guide: https://solidity.readthedocs.io/en/latest/style-guide.html
+Any exception or additions specific to our project are documented below.
 
-#### G1 - No Magic Constants
+* Try to avoid acronyms and abbreviations.
 
-Avoid constants in the code as much as possible. Magic strings are also magic constants.
+* All state variables should be private.
 
-#### G2 - Code that Fails Early
+* Private state variables should have an underscore prefix.
 
-We ask our code to fail as soon as possible when an unexpected input was provided or unexpected state was found.
+    ```
+    contract TestContract {
+      uint256 private _privateVar;
+      uint256 internal _internalVar;
+    }
+    ```
 
-#### G3 - Internal Amounts Must be Signed Integers and Represent the Smallest Units.
+* Parameters must not be prefixed with an underscore.
 
-Avoid representation errors by always dealing with weis when handling ether. GUIs can convert to more human-friendly representations. Use Signed Integers (int) to prevent underflow problems.
+    ```
+    function test(uint256 testParameter1, uint256 testParameter2) {
+    ...
+    }
+    ```
+
+* Internal and private functions should have an underscore prefix.
+
+    ```
+    function _testInternal() internal {
+      ...
+    }
+    ```
+
+    ```
+    function _testPrivate() private {
+      ...
+    }
+    ```
+
+* Events should be emitted immediately after the state change that they
+  represent, and consequently they should be named in past tense.
+
+    ```
+    function _burn(address who, uint256 value) internal {
+      super._burn(who, value);
+      emit TokensBurned(who, value);
+    }
+    ```
+
+  Some standards (e.g. ERC20) use present tense, and in those cases the
+  standard specification prevails.
+  
+* Interface names should have a capital I prefix.
+
+    ```
+    interface IERC777 {
+    ```
 
 
-### Testing
+## Tests
 
-#### T1 - Tests Must be Written Elegantly
+* Tests Must be Written Elegantly
 
-Style guidelines are not relaxed for tests. Tests are a good way to show how to use the library, and maintaining them is extremely necessary.
+    Tests are a good way to show how to use the library, and maintaining them is extremely necessary. Don't write long tests, write helper functions to make them be as short and concise as possible (they should take just a few lines each), and use good variable names.
 
-Don't write long tests, write helper functions to make them be as short and concise as possible (they should take just a few lines each), and use good variable names.
+* Tests Must not be Random
 
-#### T2 - Tests Must not be Random
-
-Inputs for tests should not be generated randomly. Accounts used to create test contracts are an exception, those can be random. Also, the type and structure of outputs should be checked.
+    Inputs for tests should not be generated randomly. Accounts used to create test contracts are an exception, those can be random. Also, the type and structure of outputs should be checked.

LICENSE

@@ -1,6 +1,6 @@
 The MIT License (MIT)
 
-Copyright (c) 2016-2019 zOS Global Limited
+Copyright (c) 2016-2020 zOS Global Limited
 
 Permission is hereby granted, free of charge, to any person obtaining
 a copy of this software and associated documentation files (the

README.md

@@ -1,8 +1,7 @@
-# <img src="logo.png" alt="OpenZeppelin" height="40px">
+# <img src="logo.svg" alt="OpenZeppelin" height="40px">
 
 [![Docs](https://img.shields.io/badge/docs-%F0%9F%93%84-blue)](https://docs.openzeppelin.com/contracts)
 [![NPM Package](https://img.shields.io/npm/v/@openzeppelin/contracts.svg)](https://www.npmjs.org/package/@openzeppelin/contracts)
-[![Build Status](https://circleci.com/gh/OpenZeppelin/openzeppelin-contracts.svg?style=shield)](https://circleci.com/gh/OpenZeppelin/openzeppelin-contracts)
 [![Coverage Status](https://codecov.io/gh/OpenZeppelin/openzeppelin-contracts/graph/badge.svg)](https://codecov.io/gh/OpenZeppelin/openzeppelin-contracts)
 
 **A library for secure smart contract development.** Build on a solid foundation of community-vetted code.
@@ -10,8 +9,8 @@
  * Implementations of standards like [ERC20](https://docs.openzeppelin.com/contracts/erc20) and [ERC721](https://docs.openzeppelin.com/contracts/erc721).
  * Flexible [role-based permissioning](https://docs.openzeppelin.com/contracts/access-control) scheme.
  * Reusable [Solidity components](https://docs.openzeppelin.com/contracts/utilities) to build custom contracts and complex decentralized systems.
- * First-class integration with the [Gas Station Network](https://docs.openzeppelin.com/contracts/gsn) for systems with no gas fees!
- * Audited by leading security firms (_last full audit on v2.0.0_).
+
+:mage: **Not sure how to get started?** Check out [Contracts Wizard](https://wizard.openzeppelin.com/) — an interactive smart contract generator.
 
 ## Overview
 
@@ -28,13 +27,12 @@ OpenZeppelin Contracts features a [stable API](https://docs.openzeppelin.com/con
 Once installed, you can use the contracts in the library by importing them:
 
 ```solidity
-pragma solidity ^0.5.0;
+pragma solidity ^0.8.0;
 
-import "@openzeppelin/contracts/token/ERC721/ERC721Full.sol";
-import "@openzeppelin/contracts/token/ERC721/ERC721Mintable.sol";
+import "@openzeppelin/contracts/token/ERC721/ERC721.sol";
 
-contract MyNFT is ERC721Full, ERC721Mintable {
-    constructor() ERC721Full("MyNFT", "MNFT") public {
+contract MyCollectible is ERC721 {
+    constructor() ERC721("MyCollectible", "MCO") {
     }
 }
 ```
@@ -45,7 +43,7 @@ To keep your system secure, you should **always** use the installed code as-is,
 
 ## Learn More
 
-The guides in the sidebar will teach about different concepts, and how to use the related contracts that OpenZeppelin Contracts provides:
+The guides in the [docs site](https://docs.openzeppelin.com/contracts) will teach about different concepts, and how to use the related contracts that OpenZeppelin Contracts provides:
 
 * [Access Control](https://docs.openzeppelin.com/contracts/access-control): decide who can perform each of the actions on your system.
 * [Tokens](https://docs.openzeppelin.com/contracts/tokens): create tradeable assets or collectives, and distribute them via [Crowdsales](https://docs.openzeppelin.com/contracts/crowdsales).
@@ -62,18 +60,20 @@ Finally, you may want to take a look at the [guides on our blog](https://blog.op
 
 ## Security
 
-This project is maintained by [OpenZeppelin](https://openzeppelin.com), 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.
+This project is maintained by [OpenZeppelin](https://openzeppelin.com), 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.
 
+Critical bug fixes will be backported to past major releases.
+
 ## Contribute
 
-OpenZeppelin exists thanks to its contributors. There are many ways you can participate and help build high quality software. Check out the [contribution guide](CONTRIBUTING.md)!
+OpenZeppelin Contracts exists thanks to its contributors. There are many ways you can participate and help build high quality software. Check out the [contribution guide](CONTRIBUTING.md)!
 
 ## License
 
-OpenZeppelin is released under the [MIT License](LICENSE).
+OpenZeppelin Contracts is released under the [MIT License](LICENSE).

RELEASING.md

@@ -10,10 +10,10 @@ Publish a release candidate with `npm run release rc`.
 
 Publish the final release with `npm run release final`.
 
-Follow the general [OpenZeppelin release checklist].
+Follow the general [OpenZeppelin Contracts release checklist].
 
 [details about release schedule]: https://docs.openzeppelin.com/contracts/releases-stability
-[OpenZeppelin release checklist]: https://github.com/OpenZeppelin/code-style/blob/master/RELEASE_CHECKLIST.md
+[OpenZeppelin Contracts release checklist]: https://github.com/OpenZeppelin/code-style/blob/master/RELEASE_CHECKLIST.md
 
 
 ## Merging the release branch

SECURITY.md

@@ -0,0 +1,18 @@
+# Security Policy
+
+## Supported Versions
+
+The recommendation is to use the latest version available.
+
+| Version | Supported                            |
+| ------- | ------------------------------------ |
+| 4.x     | :white_check_mark::white_check_mark: |
+| 3.4     | :white_check_mark:                   |
+| 2.5     | :white_check_mark:                   |
+| < 2.0   | :x:                                  |
+
+## Reporting a Vulnerability
+
+Please report any security issues you find to security@openzeppelin.org.
+
+Critical bug fixes will be backported to past major releases.

audit/2017-03.md

@@ -1,5 +1,7 @@
 # OpenZeppelin Audit
 
+NOTE ON 2021-07-19: This report makes reference to Zeppelin, OpenZeppelin, OpenZeppelin [C]ontracts, the OpenZeppelin team, and OpenZeppelin library. Many of these things have since been renamed and know that this audit applies to what is currently called the OpenZeppelin Contracts which are maintained by the OpenZeppelin Conracts Community.
+
 March, 2017
 Authored by Dennis Peterson and Peter Vessenes
 

contracts/GSN/GSNRecipient.sol

@@ -1,230 +0,0 @@
-// SPDX-License-Identifier: MIT
-
-pragma solidity ^0.6.0;
-
-import "./IRelayRecipient.sol";
-import "./IRelayHub.sol";
-import "./Context.sol";
-
-/**
- * @dev Base GSN recipient contract: includes the {IRelayRecipient} interface
- * and enables GSN support on all contracts in the inheritance tree.
- *
- * TIP: This contract is abstract. The functions {IRelayRecipient-acceptRelayedCall},
- *  {_preRelayedCall}, and {_postRelayedCall} are not implemented and must be
- * provided by derived contracts. See the
- * xref:ROOT:gsn-strategies.adoc#gsn-strategies[GSN strategies] for more
- * information on how to use the pre-built {GSNRecipientSignature} and
- * {GSNRecipientERC20Fee}, or how to write your own.
- */
-abstract contract GSNRecipient is IRelayRecipient, Context {
-    // Default RelayHub address, deployed on mainnet and all testnets at the same address
-    address private _relayHub = 0xD216153c06E857cD7f72665E0aF1d7D82172F494;
-
-    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;
-
-    /**
-     * @dev Emitted when a contract changes its {IRelayHub} contract to a new one.
-     */
-    event RelayHubChanged(address indexed oldRelayHub, address indexed newRelayHub);
-
-    /**
-     * @dev Returns the address of the {IRelayHub} contract for this recipient.
-     */
-    function getHubAddr() public view override returns (address) {
-        return _relayHub;
-    }
-
-    /**
-     * @dev Switches to a new {IRelayHub} instance. This method is added for future-proofing: there's no reason to not
-     * use the default instance.
-     *
-     * IMPORTANT: After upgrading, the {GSNRecipient} will no longer be able to receive relayed calls from the old
-     * {IRelayHub} instance. Additionally, all funds should be previously withdrawn via {_withdrawDeposits}.
-     */
-    function _upgradeRelayHub(address newRelayHub) internal virtual {
-        address currentRelayHub = _relayHub;
-        require(newRelayHub != address(0), "GSNRecipient: new RelayHub is the zero address");
-        require(newRelayHub != currentRelayHub, "GSNRecipient: new RelayHub is the current one");
-
-        emit RelayHubChanged(currentRelayHub, newRelayHub);
-
-        _relayHub = newRelayHub;
-    }
-
-    /**
-     * @dev Returns the version string of the {IRelayHub} for which this recipient implementation was built. If
-     * {_upgradeRelayHub} is used, the new {IRelayHub} instance should be compatible with this version.
-     */
-    // 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";
-    }
-
-    /**
-     * @dev Withdraws the recipient's deposits in `RelayHub`.
-     *
-     * Derived contracts should expose this in an external interface with proper access control.
-     */
-    function _withdrawDeposits(uint256 amount, address payable payee) internal virtual {
-        IRelayHub(_relayHub).withdraw(amount, payee);
-    }
-
-    // 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.
-
-    /**
-     * @dev Replacement for msg.sender. Returns the actual sender of a transaction: msg.sender for regular transactions,
-     * and the end-user for GSN relayed calls (where msg.sender is actually `RelayHub`).
-     *
-     * IMPORTANT: Contracts derived from {GSNRecipient} should never use `msg.sender`, and use {_msgSender} instead.
-     */
-    function _msgSender() internal view virtual override returns (address payable) {
-        if (msg.sender != _relayHub) {
-            return msg.sender;
-        } else {
-            return _getRelayedCallSender();
-        }
-    }
-
-    /**
-     * @dev Replacement for msg.data. Returns the actual calldata of a transaction: msg.data for regular transactions,
-     * and a reduced version for GSN relayed calls (where msg.data contains additional information).
-     *
-     * IMPORTANT: Contracts derived from {GSNRecipient} should never use `msg.data`, and use {_msgData} instead.
-     */
-    function _msgData() internal view virtual override returns (bytes memory) {
-        if (msg.sender != _relayHub) {
-            return msg.data;
-        } else {
-            return _getRelayedCallData();
-        }
-    }
-
-    // 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 memory context) public virtual override returns (bytes32) {
-        require(msg.sender == getHubAddr(), "GSNRecipient: caller is not RelayHub");
-        return _preRelayedCall(context);
-    }
-
-    /**
-     * @dev See `IRelayRecipient.preRelayedCall`.
-     *
-     * Called by `GSNRecipient.preRelayedCall`, which asserts the caller is the `RelayHub` contract. Derived contracts
-     * must implement this function with any relayed-call preprocessing they may wish to do.
-     *
-     */
-    function _preRelayedCall(bytes memory context) internal virtual returns (bytes32);
-
-    /**
-     * @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 memory context, bool success, uint256 actualCharge, bytes32 preRetVal) public virtual override {
-        require(msg.sender == getHubAddr(), "GSNRecipient: caller is not RelayHub");
-        _postRelayedCall(context, success, actualCharge, preRetVal);
-    }
-
-    /**
-     * @dev See `IRelayRecipient.postRelayedCall`.
-     *
-     * Called by `GSNRecipient.postRelayedCall`, which asserts the caller is the `RelayHub` contract. Derived contracts
-     * must implement this function with any relayed-call postprocessing they may wish to do.
-     *
-     */
-    function _postRelayedCall(bytes memory context, bool success, uint256 actualCharge, bytes32 preRetVal) internal virtual;
-
-    /**
-     * @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 `GSNRecipient._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, "");
-    }
-
-    /*
-     * @dev Calculates how much RelayHub 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;
-    }
-
-    function _getRelayedCallSender() private pure returns (address payable 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/GSNRecipientERC20Fee.sol

@@ -1,152 +0,0 @@
-// SPDX-License-Identifier: MIT
-
-pragma solidity ^0.6.0;
-
-import "./GSNRecipient.sol";
-import "../math/SafeMath.sol";
-import "../access/Ownable.sol";
-import "../token/ERC20/SafeERC20.sol";
-import "../token/ERC20/ERC20.sol";
-
-/**
- * @dev A xref:ROOT:gsn-strategies.adoc#gsn-strategies[GSN strategy] that charges transaction fees in a special purpose ERC20
- * token, which we refer to as the gas payment token. The amount charged is exactly the amount of Ether charged to the
- * recipient. This means that the token is essentially pegged to the value of Ether.
- *
- * The distribution strategy of the gas payment token to users is not defined by this contract. It's a mintable token
- * whose only minter is the recipient, so the strategy must be implemented in a derived contract, making use of the
- * internal {_mint} function.
- */
-contract GSNRecipientERC20Fee is GSNRecipient {
-    using SafeERC20 for __unstable__ERC20Owned;
-    using SafeMath for uint256;
-
-    enum GSNRecipientERC20FeeErrorCodes {
-        INSUFFICIENT_BALANCE
-    }
-
-    __unstable__ERC20Owned private _token;
-
-    /**
-     * @dev The arguments to the constructor are the details that the gas payment token will have: `name` and `symbol`. `decimals` is hard-coded to 18.
-     */
-    constructor(string memory name, string memory symbol) public {
-        _token = new __unstable__ERC20Owned(name, symbol);
-    }
-
-    /**
-     * @dev Returns the gas payment token.
-     */
-    function token() public view returns (IERC20) {
-        return IERC20(_token);
-    }
-
-    /**
-     * @dev Internal function that mints the gas payment token. Derived contracts should expose this function in their public API, with proper access control mechanisms.
-     */
-    function _mint(address account, uint256 amount) internal virtual {
-        _token.mint(account, amount);
-    }
-
-    /**
-     * @dev Ensures that only users with enough gas payment token balance can have transactions relayed through the GSN.
-     */
-    function acceptRelayedCall(
-        address,
-        address from,
-        bytes memory,
-        uint256 transactionFee,
-        uint256 gasPrice,
-        uint256,
-        uint256,
-        bytes memory,
-        uint256 maxPossibleCharge
-    )
-        public
-        view
-        virtual
-        override
-        returns (uint256, bytes memory)
-    {
-        if (_token.balanceOf(from) < maxPossibleCharge) {
-            return _rejectRelayedCall(uint256(GSNRecipientERC20FeeErrorCodes.INSUFFICIENT_BALANCE));
-        }
-
-        return _approveRelayedCall(abi.encode(from, maxPossibleCharge, transactionFee, gasPrice));
-    }
-
-    /**
-     * @dev Implements the precharge to the user. The maximum possible charge (depending on gas limit, gas price, and
-     * fee) will be deducted from the user balance of gas payment token. Note that this is an overestimation of the
-     * actual charge, necessary because we cannot predict how much gas the execution will actually need. The remainder
-     * is returned to the user in {_postRelayedCall}.
-     */
-    function _preRelayedCall(bytes memory context) internal virtual override returns (bytes32) {
-        (address from, uint256 maxPossibleCharge) = abi.decode(context, (address, uint256));
-
-        // The maximum token charge is pre-charged from the user
-        _token.safeTransferFrom(from, address(this), maxPossibleCharge);
-    }
-
-    /**
-     * @dev Returns to the user the extra amount that was previously charged, once the actual execution cost is known.
-     */
-    function _postRelayedCall(bytes memory context, bool, uint256 actualCharge, bytes32) internal virtual override {
-        (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
-        _token.safeTransfer(from, maxPossibleCharge.sub(actualCharge));
-    }
-}
-
-/**
- * @title __unstable__ERC20Owned
- * @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__ERC20Owned is ERC20, Ownable {
-    uint256 private constant _UINT256_MAX = 2**256 - 1;
-
-    constructor(string memory name, string memory symbol) public ERC20(name, symbol) { }
-
-    // The owner (GSNRecipientERC20Fee) can mint tokens
-    function mint(address account, uint256 amount) public onlyOwner {
-        _mint(account, amount);
-    }
-
-    // The owner has 'infinite' allowance for all token holders
-    function allowance(address tokenOwner, address spender) public view override returns (uint256) {
-        if (spender == owner()) {
-            return _UINT256_MAX;
-        } else {
-            return super.allowance(tokenOwner, spender);
-        }
-    }
-
-    // Allowance for the owner cannot be changed (it is always 'infinite')
-    function _approve(address tokenOwner, address spender, uint256 value) internal override {
-        if (spender == owner()) {
-            return;
-        } else {
-            super._approve(tokenOwner, spender, value);
-        }
-    }
-
-    function transferFrom(address sender, address recipient, uint256 amount) public override returns (bool) {
-        if (recipient == owner()) {
-            _transfer(sender, recipient, amount);
-            return true;
-        } else {
-            return super.transferFrom(sender, recipient, amount);
-        }
-    }
-}

contracts/GSN/GSNRecipientSignature.sol

@@ -1,72 +0,0 @@
-// SPDX-License-Identifier: MIT
-
-pragma solidity ^0.6.0;
-
-import "./GSNRecipient.sol";
-import "../cryptography/ECDSA.sol";
-
-/**
- * @dev A xref:ROOT:gsn-strategies.adoc#gsn-strategies[GSN strategy] that allows relayed transactions through when they are
- * accompanied by the signature of a trusted signer. The intent is for this signature to be generated by a server that
- * performs validations off-chain. Note that nothing is charged to the user in this scheme. Thus, the server should make
- * sure to account for this in their economic and threat model.
- */
-contract GSNRecipientSignature is GSNRecipient {
-    using ECDSA for bytes32;
-
-    address private _trustedSigner;
-
-    enum GSNRecipientSignatureErrorCodes {
-        INVALID_SIGNER
-    }
-
-    /**
-     * @dev Sets the trusted signer that is going to be producing signatures to approve relayed calls.
-     */
-    constructor(address trustedSigner) public {
-        require(trustedSigner != address(0), "GSNRecipientSignature: trusted signer is the zero address");
-        _trustedSigner = trustedSigner;
-    }
-
-    /**
-     * @dev Ensures that only transactions with a trusted signature can be relayed through the GSN.
-     */
-    function acceptRelayedCall(
-        address relay,
-        address from,
-        bytes memory encodedFunction,
-        uint256 transactionFee,
-        uint256 gasPrice,
-        uint256 gasLimit,
-        uint256 nonce,
-        bytes memory approvalData,
-        uint256
-    )
-        public
-        view
-        virtual
-        override
-        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) == _trustedSigner) {
-            return _approveRelayedCall();
-        } else {
-            return _rejectRelayedCall(uint256(GSNRecipientSignatureErrorCodes.INVALID_SIGNER));
-        }
-    }
-
-    function _preRelayedCall(bytes memory) internal virtual override returns (bytes32) { }
-
-    function _postRelayedCall(bytes memory, bool, uint256, bytes32) internal virtual override { }
-}

contracts/GSN/IRelayHub.sol

@@ -1,269 +0,0 @@
-// SPDX-License-Identifier: MIT
-
-pragma solidity ^0.6.0;
-
-/**
- * @dev Interface for `RelayHub`, the core contract of the GSN. Users should not need to interact with this contract
- * directly.
- *
- * See the https://github.com/OpenZeppelin/openzeppelin-gsn-helpers[OpenZeppelin GSN helpers] for more information on
- * how to deploy an instance of `RelayHub` on your local test network.
- */
-interface IRelayHub {
-    // Relay management
-
-    /**
-     * @dev Adds 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;
-
-    /**
-     * @dev Emitted when a relay's stake or unstakeDelay are increased
-     */
-    event Staked(address indexed relay, uint256 stake, uint256 unstakeDelay);
-
-    /**
-     * @dev 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).
-     *
-     * This function can be called multiple times, emitting new {RelayAdded} events. Note that the received
-     * `transactionFee` is not enforced by {relayCall}.
-     *
-     * Emits a {RelayAdded} event.
-     */
-    function registerRelay(uint256 transactionFee, string calldata url) external;
-
-    /**
-     * @dev 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);
-
-    /**
-     * @dev 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) external;
-
-    /**
-     * @dev 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) external;
-
-    /**
-     * @dev 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
-    }
-
-    /**
-     * @dev Returns a relay's status. Note that relays can be deleted when unstaked or penalized, causing this function
-     * to return an empty entry.
-     */
-    function getRelay(address relay) external view returns (uint256 totalStake, uint256 unstakeDelay, uint256 unstakeTime, address payable owner, RelayState state);
-
-    // Balance management
-
-    /**
-     * @dev 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 calling {withdraw}.
-     *
-     * Emits a {Deposited} event.
-     */
-    function depositFor(address target) external payable;
-
-    /**
-     * @dev Emitted when {depositFor} is called, including the amount and account that was funded.
-     */
-    event Deposited(address indexed recipient, address indexed from, uint256 amount);
-
-    /**
-     * @dev Returns an account's deposits. These can be either a contracts'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 use it to reduce their funding.
-     *
-     * Emits a {Withdrawn} event.
-     */
-    function withdraw(uint256 amount, address payable dest) external;
-
-    /**
-     * @dev Emitted when an account withdraws funds from `RelayHub`.
-     */
-    event Withdrawn(address indexed account, address indexed dest, uint256 amount);
-
-    // Relaying
-
-    /**
-     * @dev Checks 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 calldata encodedFunction,
-        uint256 transactionFee,
-        uint256 gasPrice,
-        uint256 gasLimit,
-        uint256 nonce,
-        bytes calldata signature,
-        bytes calldata approvalData
-    ) external 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
-    }
-
-    /**
-     * @dev Relays a transaction.
-     *
-     * For this to succeed, 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 that order.
-     *
-     * Parameters:
-     *  - `from`: the client originating the request
-     *  - `to`: 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
-     * `RelayHub`, but it still can be used for e.g. a signature.
-     *
-     * Emits a {TransactionRelayed} event.
-     */
-    function relayCall(
-        address from,
-        address to,
-        bytes calldata encodedFunction,
-        uint256 transactionFee,
-        uint256 gasPrice,
-        uint256 gasLimit,
-        uint256 nonce,
-        bytes calldata signature,
-        bytes calldata approvalData
-    ) external;
-
-    /**
-     * @dev 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` parameter 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);
-
-    /**
-     * @dev Emitted when a transaction is relayed.
-     * Useful when monitoring a relay's operation and relayed calls to a contract
-     *
-     * Note that the actual encoded function might be reverted: this is indicated in the `status` parameter.
-     *
-     * `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
-    }
-
-    /**
-     * @dev 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) external view returns (uint256);
-
-    /**
-     * @dev Returns the maximum recipient charge, given the amount of gas forwarded, gas price and relay fee.
-     */
-    function maxPossibleCharge(uint256 relayedCallStipend, uint256 gasPrice, uint256 transactionFee) external 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.
-
-    /**
-     * @dev 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 calldata unsignedTx1, bytes calldata signature1, bytes calldata unsignedTx2, bytes calldata signature2) external;
-
-    /**
-     * @dev Penalize a relay that sent a transaction that didn't target ``RelayHub``'s {registerRelay} or {relayCall}.
-     */
-    function penalizeIllegalTransaction(bytes calldata unsignedTx, bytes calldata signature) external;
-
-    /**
-     * @dev Emitted when a relay is penalized.
-     */
-    event Penalized(address indexed relay, address sender, uint256 amount);
-
-    /**
-     * @dev Returns an account's nonce in `RelayHub`.
-     */
-    function getNonce(address from) external view returns (uint256);
-}
-

contracts/GSN/IRelayRecipient.sol

@@ -1,76 +0,0 @@
-// SPDX-License-Identifier: MIT
-
-pragma solidity ^0.6.0;
-
-/**
- * @dev Base interface for a contract that will be called via the GSN from {IRelayHub}.
- *
- * TIP: You don't need to write an implementation yourself! Inherit from {GSNRecipient} instead.
- */
-interface IRelayRecipient {
-    /**
-     * @dev Returns the address of the {IRelayHub} instance this recipient interacts with.
-     */
-    function getHubAddr() external view returns (address);
-
-    /**
-     * @dev Called by {IRelayHub} to validate if this recipient accepts being charged for a relayed call. Note that the
-     * recipient will be charged regardless of the execution result of the relayed call (i.e. if it reverts or not).
-     *
-     * The relay request was originated by `from` and will be served by `relay`. `encodedFunction` is the relayed call
-     * calldata, so its first four bytes are the function selector. The relayed call will be forwarded `gasLimit` gas,
-     * and the transaction executed with a gas price of at least `gasPrice`. ``relay``'s fee is `transactionFee`, and the
-     * recipient will be charged at most `maxPossibleCharge` (in wei). `nonce` is the sender's (`from`) nonce for
-     * replay attack protection in {IRelayHub}, and `approvalData` is a optional parameter that can be used to hold a signature
-     * over all or some of the previous values.
-     *
-     * Returns a tuple, where the first value is used to indicate approval (0) or rejection (custom non-zero error code,
-     * values 1 to 10 are reserved) and the second one is data to be passed to the other {IRelayRecipient} functions.
-     *
-     * {acceptRelayedCall} is called with 50k gas: if it runs out during execution, the request will be considered
-     * rejected. A regular revert will also trigger a rejection.
-     */
-    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);
-
-    /**
-     * @dev Called by {IRelayHub} on approved relay call requests, before the relayed call is executed. This allows to e.g.
-     * pre-charge the sender of the transaction.
-     *
-     * `context` is the second value returned in the tuple by {acceptRelayedCall}.
-     *
-     * Returns a value to be passed to {postRelayedCall}.
-     *
-     * {preRelayedCall} is called with 100k gas: if it runs out during exection or otherwise reverts, the relayed call
-     * will not be executed, but the recipient will still be charged for the transaction's cost.
-     */
-    function preRelayedCall(bytes calldata context) external returns (bytes32);
-
-    /**
-     * @dev Called by {IRelayHub} on approved relay call requests, after the relayed call is executed. This allows to e.g.
-     * charge the user for the relayed call costs, return any overcharges from {preRelayedCall}, or perform
-     * contract-specific bookkeeping.
-     *
-     * `context` is the second value returned in the tuple by {acceptRelayedCall}. `success` is the execution status of
-     * the relayed call. `actualCharge` is an estimate of how much the recipient will be charged for the transaction,
-     * not including any gas used by {postRelayedCall} itself. `preRetVal` is {preRelayedCall}'s return value.
-     *
-     *
-     * {postRelayedCall} is called with 100k gas: if it runs out during execution or otherwise reverts, the relayed call
-     * and the call to {preRelayedCall} will be reverted retroactively, but the recipient will still be charged for the
-     * transaction's cost.
-     */
-    function postRelayedCall(bytes calldata context, bool success, uint256 actualCharge, bytes32 preRetVal) external;
-}

contracts/GSN/README.adoc

@@ -1,28 +0,0 @@
-= Gas Station Network (GSN)
-
-This set of contracts provide all the tools required to make a contract callable via the https://gsn.openzeppelin.com[Gas Station Network].
-
-TIP: If you're new to the GSN, head over to our xref:learn::sending-gasless-transactions.adoc[overview of the system] and basic guide to xref:ROOT:gsn.adoc[creating a GSN-capable contract].
-
-The core contract a recipient must inherit from is {GSNRecipient}: it includes all necessary interfaces, as well as some helper methods to make interacting with the GSN easier.
-
-Utilities to make writing xref:ROOT:gsn-strategies.adoc[GSN strategies] easy are available in {GSNRecipient}, or you can simply use one of our pre-made strategies:
-
-* {GSNRecipientERC20Fee} charges the end user for gas costs in an application-specific xref:ROOT:tokens.adoc#ERC20[ERC20 token]
-* {GSNRecipientSignature} accepts all relayed calls that have been signed by a trusted third party (e.g. a private key in a backend)
-
-You can also take a look at the two contract interfaces that make up the GSN protocol: {IRelayRecipient} and {IRelayHub}, but you won't need to use those directly.
-
-== Recipient
-
-{{GSNRecipient}}
-
-== Strategies
-
-{{GSNRecipientSignature}}
-{{GSNRecipientERC20Fee}}
-
-== Protocol
-
-{{IRelayRecipient}}
-{{IRelayHub}}

contracts/access/AccessControl.sol

@@ -1,14 +1,18 @@
 // SPDX-License-Identifier: MIT
 
-pragma solidity ^0.6.0;
+pragma solidity ^0.8.0;
 
-import "../utils/EnumerableSet.sol";
-import "../utils/Address.sol";
-import "../GSN/Context.sol";
+import "./IAccessControl.sol";
+import "../utils/Context.sol";
+import "../utils/Strings.sol";
+import "../utils/introspection/ERC165.sol";
 
 /**
  * @dev Contract module that allows children to implement role-based access
- * control mechanisms.
+ * control mechanisms. This is a lightweight version that doesn't allow enumerating role
+ * members except through off-chain means by accessing the contract event logs. Some
+ * applications may benefit from on-chain enumerability, for those cases see
+ * {AccessControlEnumerable}.
  *
  * Roles are referred to by their `bytes32` identifier. These should be exposed
  * in the external API and be unique. The best way to achieve this is by
@@ -41,65 +45,65 @@ import "../GSN/Context.sol";
  * grant and revoke this role. Extra precautions should be taken to secure
  * accounts that have been granted it.
  */
-abstract contract AccessControl is Context {
-    using EnumerableSet for EnumerableSet.AddressSet;
-    using Address for address;
-
+abstract contract AccessControl is Context, IAccessControl, ERC165 {
     struct RoleData {
-        EnumerableSet.AddressSet members;
+        mapping(address => bool) members;
         bytes32 adminRole;
     }
 
-    mapping (bytes32 => RoleData) private _roles;
+    mapping(bytes32 => RoleData) private _roles;
 
     bytes32 public constant DEFAULT_ADMIN_ROLE = 0x00;
 
     /**
-     * @dev Emitted when `account` is granted `role`.
+     * @dev Modifier that checks that an account has a specific role. Reverts
+     * with a standardized message including the required role.
      *
-     * `sender` is the account that originated the contract call, an admin role
-     * bearer except when using {_setupRole}.
+     * The format of the revert reason is given by the following regular expression:
+     *
+     *  /^AccessControl: account (0x[0-9a-f]{40}) is missing role (0x[0-9a-f]{64})$/
+     *
+     * _Available since v4.1._
      */
-    event RoleGranted(bytes32 indexed role, address indexed account, address indexed sender);
+    modifier onlyRole(bytes32 role) {
+        _checkRole(role, _msgSender());
+        _;
+    }
 
     /**
-     * @dev Emitted when `account` is revoked `role`.
-     *
-     * `sender` is the account that originated the contract call:
-     *   - if using `revokeRole`, it is the admin role bearer
-     *   - if using `renounceRole`, it is the role bearer (i.e. `account`)
+     * @dev See {IERC165-supportsInterface}.
      */
-    event RoleRevoked(bytes32 indexed role, address indexed account, address indexed sender);
+    function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
+        return interfaceId == type(IAccessControl).interfaceId || super.supportsInterface(interfaceId);
+    }
 
     /**
      * @dev Returns `true` if `account` has been granted `role`.
      */
-    function hasRole(bytes32 role, address account) public view returns (bool) {
-        return _roles[role].members.contains(account);
+    function hasRole(bytes32 role, address account) public view override returns (bool) {
+        return _roles[role].members[account];
     }
 
     /**
-     * @dev Returns the number of accounts that have `role`. Can be used
-     * together with {getRoleMember} to enumerate all bearers of a role.
-     */
-    function getRoleMemberCount(bytes32 role) public view returns (uint256) {
-        return _roles[role].members.length();
-    }
-
-    /**
-     * @dev Returns one of the accounts that have `role`. `index` must be a
-     * value between 0 and {getRoleMemberCount}, non-inclusive.
+     * @dev Revert with a standard message if `account` is missing `role`.
      *
-     * Role bearers are not sorted in any particular way, and their ordering may
-     * change at any point.
+     * The format of the revert reason is given by the following regular expression:
      *
-     * WARNING: When using {getRoleMember} and {getRoleMemberCount}, make sure
-     * you perform all queries on the same block. See the following
-     * https://forum.openzeppelin.com/t/iterating-over-elements-on-enumerableset-in-openzeppelin-contracts/2296[forum post]
-     * for more information.
+     *  /^AccessControl: account (0x[0-9a-f]{40}) is missing role (0x[0-9a-f]{64})$/
      */
-    function getRoleMember(bytes32 role, uint256 index) public view returns (address) {
-        return _roles[role].members.at(index);
+    function _checkRole(bytes32 role, address account) internal view {
+        if (!hasRole(role, account)) {
+            revert(
+                string(
+                    abi.encodePacked(
+                        "AccessControl: account ",
+                        Strings.toHexString(uint160(account), 20),
+                        " is missing role ",
+                        Strings.toHexString(uint256(role), 32)
+                    )
+                )
+            );
+        }
     }
 
     /**
@@ -108,7 +112,7 @@ abstract contract AccessControl is Context {
      *
      * To change a role's admin, use {_setRoleAdmin}.
      */
-    function getRoleAdmin(bytes32 role) public view returns (bytes32) {
+    function getRoleAdmin(bytes32 role) public view override returns (bytes32) {
         return _roles[role].adminRole;
     }
 
@@ -122,9 +126,7 @@ abstract contract AccessControl is Context {
      *
      * - the caller must have ``role``'s admin role.
      */
-    function grantRole(bytes32 role, address account) public virtual {
-        require(hasRole(_roles[role].adminRole, _msgSender()), "AccessControl: sender must be an admin to grant");
-
+    function grantRole(bytes32 role, address account) public virtual override onlyRole(getRoleAdmin(role)) {
         _grantRole(role, account);
     }
 
@@ -137,9 +139,7 @@ abstract contract AccessControl is Context {
      *
      * - the caller must have ``role``'s admin role.
      */
-    function revokeRole(bytes32 role, address account) public virtual {
-        require(hasRole(_roles[role].adminRole, _msgSender()), "AccessControl: sender must be an admin to revoke");
-
+    function revokeRole(bytes32 role, address account) public virtual override onlyRole(getRoleAdmin(role)) {
         _revokeRole(role, account);
     }
 
@@ -157,7 +157,7 @@ abstract contract AccessControl is Context {
      *
      * - the caller must be `account`.
      */
-    function renounceRole(bytes32 role, address account) public virtual {
+    function renounceRole(bytes32 role, address account) public virtual override {
         require(account == _msgSender(), "AccessControl: can only renounce roles for self");
 
         _revokeRole(role, account);
@@ -185,19 +185,25 @@ abstract contract AccessControl is Context {
 
     /**
      * @dev Sets `adminRole` as ``role``'s admin role.
+     *
+     * Emits a {RoleAdminChanged} event.
      */
     function _setRoleAdmin(bytes32 role, bytes32 adminRole) internal virtual {
+        bytes32 previousAdminRole = getRoleAdmin(role);
         _roles[role].adminRole = adminRole;
+        emit RoleAdminChanged(role, previousAdminRole, adminRole);
     }
 
     function _grantRole(bytes32 role, address account) private {
-        if (_roles[role].members.add(account)) {
+        if (!hasRole(role, account)) {
+            _roles[role].members[account] = true;
             emit RoleGranted(role, account, _msgSender());
         }
     }
 
     function _revokeRole(bytes32 role, address account) private {
-        if (_roles[role].members.remove(account)) {
+        if (hasRole(role, account)) {
+            _roles[role].members[account] = false;
             emit RoleRevoked(role, account, _msgSender());
         }
     }

contracts/access/AccessControlEnumerable.sol

@@ -0,0 +1,79 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "./IAccessControlEnumerable.sol";
+import "./AccessControl.sol";
+import "../utils/structs/EnumerableSet.sol";
+
+/**
+ * @dev Extension of {AccessControl} that allows enumerating the members of each role.
+ */
+abstract contract AccessControlEnumerable is IAccessControlEnumerable, AccessControl {
+    using EnumerableSet for EnumerableSet.AddressSet;
+
+    mapping(bytes32 => EnumerableSet.AddressSet) private _roleMembers;
+
+    /**
+     * @dev See {IERC165-supportsInterface}.
+     */
+    function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
+        return interfaceId == type(IAccessControlEnumerable).interfaceId || super.supportsInterface(interfaceId);
+    }
+
+    /**
+     * @dev Returns one of the accounts that have `role`. `index` must be a
+     * value between 0 and {getRoleMemberCount}, non-inclusive.
+     *
+     * Role bearers are not sorted in any particular way, and their ordering may
+     * change at any point.
+     *
+     * WARNING: When using {getRoleMember} and {getRoleMemberCount}, make sure
+     * you perform all queries on the same block. See the following
+     * https://forum.openzeppelin.com/t/iterating-over-elements-on-enumerableset-in-openzeppelin-contracts/2296[forum post]
+     * for more information.
+     */
+    function getRoleMember(bytes32 role, uint256 index) public view override returns (address) {
+        return _roleMembers[role].at(index);
+    }
+
+    /**
+     * @dev Returns the number of accounts that have `role`. Can be used
+     * together with {getRoleMember} to enumerate all bearers of a role.
+     */
+    function getRoleMemberCount(bytes32 role) public view override returns (uint256) {
+        return _roleMembers[role].length();
+    }
+
+    /**
+     * @dev Overload {grantRole} to track enumerable memberships
+     */
+    function grantRole(bytes32 role, address account) public virtual override(AccessControl, IAccessControl) {
+        super.grantRole(role, account);
+        _roleMembers[role].add(account);
+    }
+
+    /**
+     * @dev Overload {revokeRole} to track enumerable memberships
+     */
+    function revokeRole(bytes32 role, address account) public virtual override(AccessControl, IAccessControl) {
+        super.revokeRole(role, account);
+        _roleMembers[role].remove(account);
+    }
+
+    /**
+     * @dev Overload {renounceRole} to track enumerable memberships
+     */
+    function renounceRole(bytes32 role, address account) public virtual override(AccessControl, IAccessControl) {
+        super.renounceRole(role, account);
+        _roleMembers[role].remove(account);
+    }
+
+    /**
+     * @dev Overload {_setupRole} to track enumerable memberships
+     */
+    function _setupRole(bytes32 role, address account) internal virtual override {
+        super._setupRole(role, account);
+        _roleMembers[role].add(account);
+    }
+}

contracts/access/IAccessControl.sol

@@ -0,0 +1,87 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+/**
+ * @dev External interface of AccessControl declared to support ERC165 detection.
+ */
+interface IAccessControl {
+    /**
+     * @dev Emitted when `newAdminRole` is set as ``role``'s admin role, replacing `previousAdminRole`
+     *
+     * `DEFAULT_ADMIN_ROLE` is the starting admin for all roles, despite
+     * {RoleAdminChanged} not being emitted signaling this.
+     *
+     * _Available since v3.1._
+     */
+    event RoleAdminChanged(bytes32 indexed role, bytes32 indexed previousAdminRole, bytes32 indexed newAdminRole);
+
+    /**
+     * @dev Emitted when `account` is granted `role`.
+     *
+     * `sender` is the account that originated the contract call, an admin role
+     * bearer except when using {AccessControl-_setupRole}.
+     */
+    event RoleGranted(bytes32 indexed role, address indexed account, address indexed sender);
+
+    /**
+     * @dev Emitted when `account` is revoked `role`.
+     *
+     * `sender` is the account that originated the contract call:
+     *   - if using `revokeRole`, it is the admin role bearer
+     *   - if using `renounceRole`, it is the role bearer (i.e. `account`)
+     */
+    event RoleRevoked(bytes32 indexed role, address indexed account, address indexed sender);
+
+    /**
+     * @dev Returns `true` if `account` has been granted `role`.
+     */
+    function hasRole(bytes32 role, address account) external view returns (bool);
+
+    /**
+     * @dev Returns the admin role that controls `role`. See {grantRole} and
+     * {revokeRole}.
+     *
+     * To change a role's admin, use {AccessControl-_setRoleAdmin}.
+     */
+    function getRoleAdmin(bytes32 role) external view returns (bytes32);
+
+    /**
+     * @dev Grants `role` to `account`.
+     *
+     * If `account` had not been already granted `role`, emits a {RoleGranted}
+     * event.
+     *
+     * Requirements:
+     *
+     * - the caller must have ``role``'s admin role.
+     */
+    function grantRole(bytes32 role, address account) external;
+
+    /**
+     * @dev Revokes `role` from `account`.
+     *
+     * If `account` had been granted `role`, emits a {RoleRevoked} event.
+     *
+     * Requirements:
+     *
+     * - the caller must have ``role``'s admin role.
+     */
+    function revokeRole(bytes32 role, address account) external;
+
+    /**
+     * @dev Revokes `role` from the calling account.
+     *
+     * Roles are often managed via {grantRole} and {revokeRole}: this function's
+     * purpose is to provide a mechanism for accounts to lose their privileges
+     * if they are compromised (such as when a trusted device is misplaced).
+     *
+     * If the calling account had been granted `role`, emits a {RoleRevoked}
+     * event.
+     *
+     * Requirements:
+     *
+     * - the caller must be `account`.
+     */
+    function renounceRole(bytes32 role, address account) external;
+}

contracts/access/IAccessControlEnumerable.sol

@@ -0,0 +1,30 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "./IAccessControl.sol";
+
+/**
+ * @dev External interface of AccessControlEnumerable declared to support ERC165 detection.
+ */
+interface IAccessControlEnumerable is IAccessControl {
+    /**
+     * @dev Returns one of the accounts that have `role`. `index` must be a
+     * value between 0 and {getRoleMemberCount}, non-inclusive.
+     *
+     * Role bearers are not sorted in any particular way, and their ordering may
+     * change at any point.
+     *
+     * WARNING: When using {getRoleMember} and {getRoleMemberCount}, make sure
+     * you perform all queries on the same block. See the following
+     * https://forum.openzeppelin.com/t/iterating-over-elements-on-enumerableset-in-openzeppelin-contracts/2296[forum post]
+     * for more information.
+     */
+    function getRoleMember(bytes32 role, uint256 index) external view returns (address);
+
+    /**
+     * @dev Returns the number of accounts that have `role`. Can be used
+     * together with {getRoleMember} to enumerate all bearers of a role.
+     */
+    function getRoleMemberCount(bytes32 role) external view returns (uint256);
+}

contracts/access/Ownable.sol

@@ -1,8 +1,9 @@
 // SPDX-License-Identifier: MIT
 
-pragma solidity ^0.6.0;
+pragma solidity ^0.8.0;
+
+import "../utils/Context.sol";
 
-import "../GSN/Context.sol";
 /**
  * @dev Contract module which provides a basic access control mechanism, where
  * there is an account (an owner) that can be granted exclusive access to
@@ -15,7 +16,7 @@ import "../GSN/Context.sol";
  * `onlyOwner`, which can be applied to your functions to restrict their use to
  * the owner.
  */
-contract Ownable is Context {
+abstract contract Ownable is Context {
     address private _owner;
 
     event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);
@@ -23,16 +24,14 @@ contract Ownable is Context {
     /**
      * @dev Initializes the contract setting the deployer as the initial owner.
      */
-    constructor () internal {
-        address msgSender = _msgSender();
-        _owner = msgSender;
-        emit OwnershipTransferred(address(0), msgSender);
+    constructor() {
+        _setOwner(_msgSender());
     }
 
     /**
      * @dev Returns the address of the current owner.
      */
-    function owner() public view returns (address) {
+    function owner() public view virtual returns (address) {
         return _owner;
     }
 
@@ -40,7 +39,7 @@ contract Ownable is Context {
      * @dev Throws if called by any account other than the owner.
      */
     modifier onlyOwner() {
-        require(_owner == _msgSender(), "Ownable: caller is not the owner");
+        require(owner() == _msgSender(), "Ownable: caller is not the owner");
         _;
     }
 
@@ -52,8 +51,7 @@ contract Ownable is Context {
      * thereby removing any functionality that is only available to the owner.
      */
     function renounceOwnership() public virtual onlyOwner {
-        emit OwnershipTransferred(_owner, address(0));
-        _owner = address(0);
+        _setOwner(address(0));
     }
 
     /**
@@ -62,7 +60,12 @@ contract Ownable is Context {
      */
     function transferOwnership(address newOwner) public virtual onlyOwner {
         require(newOwner != address(0), "Ownable: new owner is the zero address");
-        emit OwnershipTransferred(_owner, newOwner);
+        _setOwner(newOwner);
+    }
+
+    function _setOwner(address newOwner) private {
+        address oldOwner = _owner;
         _owner = newOwner;
+        emit OwnershipTransferred(oldOwner, newOwner);
     }
 }

contracts/access/README.adoc

@@ -1,9 +1,21 @@
-= Access
+= Access Control
 
-Contract modules for authorization and access control mechanisms.
+[.readme-notice]
+NOTE: This document is better viewed at https://docs.openzeppelin.com/contracts/api/access
 
-== Contracts
+This directory provides ways to restrict who can access the functions of a contract or when they can do it.
+
+- {AccessControl} provides a general role based access control mechanism. Multiple hierarchical roles can be created and assigned each to multiple accounts.
+- {Ownable} is a simpler mechanism with a single owner "role" that can be assigned to a single account. This simpler mechanism can be useful for quick tests but projects with production concerns are likely to outgrow it.
+
+== Authorization
 
 {{Ownable}}
 
+{{IAccessControl}}
+
 {{AccessControl}}
+
+{{IAccessControlEnumerable}}
+
+{{AccessControlEnumerable}}

contracts/cryptography/ECDSA.sol

@@ -1,83 +0,0 @@
-// SPDX-License-Identifier: MIT
-
-pragma solidity ^0.6.0;
-
-/**
- * @dev Elliptic Curve Digital Signature Algorithm (ECDSA) operations.
- *
- * These functions can be used to verify that a message was signed by the holder
- * of the private keys of a given address.
- */
-library ECDSA {
-    /**
-     * @dev Returns the address that signed a hashed message (`hash`) with
-     * `signature`. This address can then be used for verification purposes.
-     *
-     * The `ecrecover` EVM opcode allows for malleable (non-unique) signatures:
-     * this function rejects them by requiring the `s` value to be in the lower
-     * half order, and the `v` value to be either 27 or 28.
-     *
-     * IMPORTANT: `hash` _must_ be the result of a hash operation for the
-     * verification to be secure: it is possible to craft signatures that
-     * recover to arbitrary addresses for non-hashed data. A safe way to ensure
-     * this is by receiving a hash of the original message (which may otherwise
-     * be too long), and then calling {toEthSignedMessageHash} on it.
-     */
-    function recover(bytes32 hash, bytes memory signature) internal pure returns (address) {
-        // Check the signature length
-        if (signature.length != 65) {
-            revert("ECDSA: invalid signature length");
-        }
-
-        // Divide the signature in r, s and v variables
-        bytes32 r;
-        bytes32 s;
-        uint8 v;
-
-        // 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) {
-            revert("ECDSA: invalid signature 's' value");
-        }
-
-        if (v != 27 && v != 28) {
-            revert("ECDSA: invalid signature 'v' value");
-        }
-
-        // If the signature is valid (and not malleable), return the signer address
-        address signer = ecrecover(hash, v, r, s);
-        require(signer != address(0), "ECDSA: invalid signature");
-
-        return signer;
-    }
-
-    /**
-     * @dev Returns an Ethereum Signed Message, created from a `hash`. This
-     * replicates the behavior of the
-     * https://github.com/ethereum/wiki/wiki/JSON-RPC#eth_sign[`eth_sign`]
-     * JSON-RPC method.
-     *
-     * See {recover}.
-     */
-    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/README.adoc

@@ -1,9 +0,0 @@
-= Cryptography
-
-This collection of libraries provides simple and safe ways to use different cryptographic primitives.
-
-== Libraries
-
-{{ECDSA}}
-
-{{MerkleProof}}

contracts/drafts/TokenVesting.sol

@@ -1,174 +0,0 @@
-pragma solidity ^0.6.0;
-
-import "../token/ERC20/SafeERC20.sol";
-import "../access/Ownable.sol";
-import "../math/SafeMath.sol";
-
-/**
- * @title TokenVesting
- * @dev A token holder contract that can release its token balance gradually like a
- * typical vesting scheme, with a cliff and vesting period. Optionally revocable by the
- * owner.
- */
-contract TokenVesting is 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
-
-    using SafeMath for uint256;
-    using SafeERC20 for IERC20;
-
-    event TokensReleased(address token, uint256 amount);
-    event TokenVestingRevoked(address token);
-
-    // beneficiary of tokens after they are released
-    address private _beneficiary;
-
-    // Durations and timestamps are expressed in UNIX time, the same units as block.timestamp.
-    uint256 private _cliff;
-    uint256 private _start;
-    uint256 private _duration;
-
-    bool private _revocable;
-
-    mapping (address => uint256) private _released;
-    mapping (address => bool) private _revoked;
-
-    /**
-     * @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), "TokenVesting: beneficiary is the zero address");
-        // solhint-disable-next-line max-line-length
-        require(cliffDuration <= duration, "TokenVesting: cliff is longer than duration");
-        require(duration > 0, "TokenVesting: duration is 0");
-        // solhint-disable-next-line max-line-length
-        require(start.add(duration) > block.timestamp, "TokenVesting: final time is before current time");
-
-        _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, "TokenVesting: no tokens are due");
-
-        _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, "TokenVesting: cannot revoke");
-        require(!_revoked[address(token)], "TokenVesting: token already revoked");
-
-        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);
-        }
-    }
-}

contracts/finance/PaymentSplitter.sol

@@ -1,9 +1,10 @@
 // SPDX-License-Identifier: MIT
 
-pragma solidity ^0.6.0;
+pragma solidity ^0.8.0;
 
-import "../GSN/Context.sol";
-import "../math/SafeMath.sol";
+import "../utils/Address.sol";
+import "../utils/Context.sol";
+import "../utils/math/SafeMath.sol";
 
 /**
  * @title PaymentSplitter
@@ -19,8 +20,6 @@ import "../math/SafeMath.sol";
  * function.
  */
 contract PaymentSplitter is Context {
-    using SafeMath for uint256;
-
     event PayeeAdded(address account, uint256 shares);
     event PaymentReleased(address to, uint256 amount);
     event PaymentReceived(address from, uint256 amount);
@@ -39,13 +38,12 @@ contract PaymentSplitter is Context {
      * All addresses in `payees` must be non-zero. Both arrays must have the same non-zero length, and there must be no
      * duplicates in `payees`.
      */
-    constructor (address[] memory payees, uint256[] memory shares) public payable {
-        // solhint-disable-next-line max-line-length
-        require(payees.length == shares.length, "PaymentSplitter: payees and shares length mismatch");
+    constructor(address[] memory payees, uint256[] memory shares_) payable {
+        require(payees.length == shares_.length, "PaymentSplitter: payees and shares length mismatch");
         require(payees.length > 0, "PaymentSplitter: no payees");
 
         for (uint256 i = 0; i < payees.length; i++) {
-            _addPayee(payees[i], shares[i]);
+            _addPayee(payees[i], shares_[i]);
         }
     }
 
@@ -58,7 +56,7 @@ contract PaymentSplitter is Context {
      * https://solidity.readthedocs.io/en/latest/contracts.html#fallback-function[fallback
      * functions].
      */
-    receive () external payable virtual {
+    receive() external payable virtual {
         emit PaymentReceived(_msgSender(), msg.value);
     }
 
@@ -104,15 +102,15 @@ contract PaymentSplitter is Context {
     function release(address payable account) public virtual {
         require(_shares[account] > 0, "PaymentSplitter: account has no shares");
 
-        uint256 totalReceived = address(this).balance.add(_totalReleased);
-        uint256 payment = totalReceived.mul(_shares[account]).div(_totalShares).sub(_released[account]);
+        uint256 totalReceived = address(this).balance + _totalReleased;
+        uint256 payment = (totalReceived * _shares[account]) / _totalShares - _released[account];
 
         require(payment != 0, "PaymentSplitter: account is not due payment");
 
-        _released[account] = _released[account].add(payment);
-        _totalReleased = _totalReleased.add(payment);
+        _released[account] = _released[account] + payment;
+        _totalReleased = _totalReleased + payment;
 
-        account.transfer(payment);
+        Address.sendValue(account, payment);
         emit PaymentReleased(account, payment);
     }
 
@@ -128,7 +126,7 @@ contract PaymentSplitter is Context {
 
         _payees.push(account);
         _shares[account] = shares_;
-        _totalShares = _totalShares.add(shares_);
+        _totalShares = _totalShares + shares_;
         emit PayeeAdded(account, shares_);
     }
 }

contracts/finance/README.adoc

@@ -0,0 +1,10 @@
+= Finance
+
+[.readme-notice]
+NOTE: This document is better viewed at https://docs.openzeppelin.com/contracts/api/finance
+
+This directory includes primitives for financial systems. We currently only offer the {PaymentSplitter} contract, but we want to grow this directory so we welcome ideas.
+
+== PaymentSplitter
+
+{{PaymentSplitter}}

contracts/governance/Governor.sol

@@ -0,0 +1,337 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "../utils/cryptography/ECDSA.sol";
+import "../utils/cryptography/draft-EIP712.sol";
+import "../utils/introspection/ERC165.sol";
+import "../utils/math/SafeCast.sol";
+import "../utils/Address.sol";
+import "../utils/Context.sol";
+import "../utils/Timers.sol";
+import "./IGovernor.sol";
+
+/**
+ * @dev Core of the governance system, designed to be extended though various modules.
+ *
+ * This contract is abstract and requires several function to be implemented in various modules:
+ *
+ * - A counting module must implement {quorum}, {_quorumReached}, {_voteSucceeded} and {_countVote}
+ * - A voting module must implement {getVotes}
+ * - Additionanly, the {votingPeriod} must also be implemented
+ *
+ * _Available since v4.3._
+ */
+abstract contract Governor is Context, ERC165, EIP712, IGovernor {
+    using SafeCast for uint256;
+    using Timers for Timers.BlockNumber;
+
+    bytes32 public constant BALLOT_TYPEHASH = keccak256("Ballot(uint256 proposalId,uint8 support)");
+
+    struct ProposalCore {
+        Timers.BlockNumber voteStart;
+        Timers.BlockNumber voteEnd;
+        bool executed;
+        bool canceled;
+    }
+
+    string private _name;
+
+    mapping(uint256 => ProposalCore) private _proposals;
+
+    /**
+     * @dev Restrict access to governor executing address. Some module might override the _executor function to make
+     * sure this modifier is consistant with the execution model.
+     */
+    modifier onlyGovernance() {
+        require(_msgSender() == _executor(), "Governor: onlyGovernance");
+        _;
+    }
+
+    /**
+     * @dev Sets the value for {name} and {version}
+     */
+    constructor(string memory name_) EIP712(name_, version()) {
+        _name = name_;
+    }
+
+    /**
+     * @dev See {IERC165-supportsInterface}.
+     */
+    function supportsInterface(bytes4 interfaceId) public view virtual override(IERC165, ERC165) returns (bool) {
+        return interfaceId == type(IGovernor).interfaceId || super.supportsInterface(interfaceId);
+    }
+
+    /**
+     * @dev See {IGovernor-name}.
+     */
+    function name() public view virtual override returns (string memory) {
+        return _name;
+    }
+
+    /**
+     * @dev See {IGovernor-version}.
+     */
+    function version() public view virtual override returns (string memory) {
+        return "1";
+    }
+
+    /**
+     * @dev See {IGovernor-hashProposal}.
+     *
+     * The proposal id is produced by hashing the RLC encoded `targets` array, the `values` array, the `calldatas` array
+     * and the descriptionHash (bytes32 which itself is the keccak256 hash of the description string). This proposal id
+     * can be produced from the proposal data which is part of the {ProposalCreated} event. It can even be computed in
+     * advance, before the proposal is submitted.
+     *
+     * Note that the chainId and the governor address are not part of the proposal id computation. Consequently, the
+     * same proposal (with same operation and same description) will have the same id if submitted on multiple governors
+     * accross multiple networks. This also means that in order to execute the same operation twice (on the same
+     * governor) the proposer will have to change the description in order to avoid proposal id conflicts.
+     */
+    function hashProposal(
+        address[] memory targets,
+        uint256[] memory values,
+        bytes[] memory calldatas,
+        bytes32 descriptionHash
+    ) public pure virtual override returns (uint256) {
+        return uint256(keccak256(abi.encode(targets, values, calldatas, descriptionHash)));
+    }
+
+    /**
+     * @dev See {IGovernor-state}.
+     */
+    function state(uint256 proposalId) public view virtual override returns (ProposalState) {
+        ProposalCore memory proposal = _proposals[proposalId];
+
+        if (proposal.executed) {
+            return ProposalState.Executed;
+        } else if (proposal.canceled) {
+            return ProposalState.Canceled;
+        } else if (proposal.voteStart.isPending()) {
+            return ProposalState.Pending;
+        } else if (proposal.voteEnd.isPending()) {
+            return ProposalState.Active;
+        } else if (proposal.voteEnd.isExpired()) {
+            return
+                _quorumReached(proposalId) && _voteSucceeded(proposalId)
+                    ? ProposalState.Succeeded
+                    : ProposalState.Defeated;
+        } else {
+            revert("Governor: unknown proposal id");
+        }
+    }
+
+    /**
+     * @dev See {IGovernor-proposalSnapshot}.
+     */
+    function proposalSnapshot(uint256 proposalId) public view virtual override returns (uint256) {
+        return _proposals[proposalId].voteStart.getDeadline();
+    }
+
+    /**
+     * @dev See {IGovernor-proposalDeadline}.
+     */
+    function proposalDeadline(uint256 proposalId) public view virtual override returns (uint256) {
+        return _proposals[proposalId].voteEnd.getDeadline();
+    }
+
+    /**
+     * @dev Amount of votes already cast passes the threshold limit.
+     */
+    function _quorumReached(uint256 proposalId) internal view virtual returns (bool);
+
+    /**
+     * @dev Is the proposal successful or not.
+     */
+    function _voteSucceeded(uint256 proposalId) internal view virtual returns (bool);
+
+    /**
+     * @dev Register a vote with a given support and voting weight.
+     *
+     * Note: Support is generic and can represent various things depending on the voting system used.
+     */
+    function _countVote(
+        uint256 proposalId,
+        address account,
+        uint8 support,
+        uint256 weight
+    ) internal virtual;
+
+    /**
+     * @dev See {IGovernor-propose}.
+     */
+    function propose(
+        address[] memory targets,
+        uint256[] memory values,
+        bytes[] memory calldatas,
+        string memory description
+    ) public virtual override returns (uint256) {
+        uint256 proposalId = hashProposal(targets, values, calldatas, keccak256(bytes(description)));
+
+        require(targets.length == values.length, "Governor: invalid proposal length");
+        require(targets.length == calldatas.length, "Governor: invalid proposal length");
+        require(targets.length > 0, "Governor: empty proposal");
+
+        ProposalCore storage proposal = _proposals[proposalId];
+        require(proposal.voteStart.isUnset(), "Governor: proposal already exists");
+
+        uint64 snapshot = block.number.toUint64() + votingDelay().toUint64();
+        uint64 deadline = snapshot + votingPeriod().toUint64();
+
+        proposal.voteStart.setDeadline(snapshot);
+        proposal.voteEnd.setDeadline(deadline);
+
+        emit ProposalCreated(
+            proposalId,
+            _msgSender(),
+            targets,
+            values,
+            new string[](targets.length),
+            calldatas,
+            snapshot,
+            deadline,
+            description
+        );
+
+        return proposalId;
+    }
+
+    /**
+     * @dev See {IGovernor-execute}.
+     */
+    function execute(
+        address[] memory targets,
+        uint256[] memory values,
+        bytes[] memory calldatas,
+        bytes32 descriptionHash
+    ) public payable virtual override returns (uint256) {
+        uint256 proposalId = hashProposal(targets, values, calldatas, descriptionHash);
+
+        ProposalState status = state(proposalId);
+        require(
+            status == ProposalState.Succeeded || status == ProposalState.Queued,
+            "Governor: proposal not successful"
+        );
+        _proposals[proposalId].executed = true;
+
+        emit ProposalExecuted(proposalId);
+
+        _execute(proposalId, targets, values, calldatas, descriptionHash);
+
+        return proposalId;
+    }
+
+    /**
+     * @dev Internal execution mechanism. Can be overriden to implement different execution mechanism
+     */
+    function _execute(
+        uint256, /* proposalId */
+        address[] memory targets,
+        uint256[] memory values,
+        bytes[] memory calldatas,
+        bytes32 /*descriptionHash*/
+    ) internal virtual {
+        string memory errorMessage = "Governor: call reverted without message";
+        for (uint256 i = 0; i < targets.length; ++i) {
+            (bool success, bytes memory returndata) = targets[i].call{value: values[i]}(calldatas[i]);
+            Address.verifyCallResult(success, returndata, errorMessage);
+        }
+    }
+
+    /**
+     * @dev Internal cancel mechanism: locks up the proposal timer, preventing it from being re-submitted. Marks it as
+     * canceled to allow distinguishing it from executed proposals.
+     *
+     * Emits a {IGovernor-ProposalCanceled} event.
+     */
+    function _cancel(
+        address[] memory targets,
+        uint256[] memory values,
+        bytes[] memory calldatas,
+        bytes32 descriptionHash
+    ) internal virtual returns (uint256) {
+        uint256 proposalId = hashProposal(targets, values, calldatas, descriptionHash);
+        ProposalState status = state(proposalId);
+
+        require(
+            status != ProposalState.Canceled && status != ProposalState.Expired && status != ProposalState.Executed,
+            "Governor: proposal not active"
+        );
+        _proposals[proposalId].canceled = true;
+
+        emit ProposalCanceled(proposalId);
+
+        return proposalId;
+    }
+
+    /**
+     * @dev See {IGovernor-castVote}.
+     */
+    function castVote(uint256 proposalId, uint8 support) public virtual override returns (uint256) {
+        address voter = _msgSender();
+        return _castVote(proposalId, voter, support, "");
+    }
+
+    /**
+     * @dev See {IGovernor-castVoteWithReason}.
+     */
+    function castVoteWithReason(
+        uint256 proposalId,
+        uint8 support,
+        string calldata reason
+    ) public virtual override returns (uint256) {
+        address voter = _msgSender();
+        return _castVote(proposalId, voter, support, reason);
+    }
+
+    /**
+     * @dev See {IGovernor-castVoteBySig}.
+     */
+    function castVoteBySig(
+        uint256 proposalId,
+        uint8 support,
+        uint8 v,
+        bytes32 r,
+        bytes32 s
+    ) public virtual override returns (uint256) {
+        address voter = ECDSA.recover(
+            _hashTypedDataV4(keccak256(abi.encode(BALLOT_TYPEHASH, proposalId, support))),
+            v,
+            r,
+            s
+        );
+        return _castVote(proposalId, voter, support, "");
+    }
+
+    /**
+     * @dev Internal vote casting mechanism: Check that the vote is pending, that it has not been cast yet, retrieve
+     * voting weight using {IGovernor-getVotes} and call the {_countVote} internal function.
+     *
+     * Emits a {IGovernor-VoteCast} event.
+     */
+    function _castVote(
+        uint256 proposalId,
+        address account,
+        uint8 support,
+        string memory reason
+    ) internal virtual returns (uint256) {
+        ProposalCore storage proposal = _proposals[proposalId];
+        require(state(proposalId) == ProposalState.Active, "Governor: vote not currently active");
+
+        uint256 weight = getVotes(account, proposal.voteStart.getDeadline());
+        _countVote(proposalId, account, support, weight);
+
+        emit VoteCast(account, proposalId, support, weight, reason);
+
+        return weight;
+    }
+
+    /**
+     * @dev Address through which the governor executes action. Will be overloaded by module that execute actions
+     * through another contract such as a timelock.
+     */
+    function _executor() internal view virtual returns (address) {
+        return address(this);
+    }
+}

contracts/governance/IGovernor.sol

@@ -0,0 +1,214 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "../utils/introspection/ERC165.sol";
+
+/**
+ * @dev Interface of the {Governor} core.
+ *
+ * _Available since v4.3._
+ */
+abstract contract IGovernor is IERC165 {
+    enum ProposalState {
+        Pending,
+        Active,
+        Canceled,
+        Defeated,
+        Succeeded,
+        Queued,
+        Expired,
+        Executed
+    }
+
+    /**
+     * @dev Emitted when a proposal is created.
+     */
+    event ProposalCreated(
+        uint256 proposalId,
+        address proposer,
+        address[] targets,
+        uint256[] values,
+        string[] signatures,
+        bytes[] calldatas,
+        uint256 startBlock,
+        uint256 endBlock,
+        string description
+    );
+
+    /**
+     * @dev Emitted when a proposal is canceled.
+     */
+    event ProposalCanceled(uint256 proposalId);
+
+    /**
+     * @dev Emitted when a proposal is executed.
+     */
+    event ProposalExecuted(uint256 proposalId);
+
+    /**
+     * @dev Emitted when a vote is cast.
+     *
+     * Note: `support` values should be seen as buckets. There interpretation depends on the voting module used.
+     */
+    event VoteCast(address indexed voter, uint256 proposalId, uint8 support, uint256 weight, string reason);
+
+    /**
+     * @notice module:core
+     * @dev Name of the governor instance (used in building the ERC712 domain separator).
+     */
+    function name() public view virtual returns (string memory);
+
+    /**
+     * @notice module:core
+     * @dev Version of the governor instance (used in building the ERC712 domain separator). Default: "1"
+     */
+    function version() public view virtual returns (string memory);
+
+    /**
+     * @notice module:voting
+     * @dev A description of the possible `support` values for {castVote} and the way these votes are counted, meant to
+     * be consumed by UIs to show correct vote options and interpret the results. The string is a URL-encoded sequence of
+     * key-value pairs that each describe one aspect, for example `support=bravo&quorum=for,abstain`.
+     *
+     * There are 2 standard keys: `support` and `quorum`.
+     *
+     * - `support=bravo` refers to the vote options 0 = For, 1 = Against, 2 = Abstain, as in `GovernorBravo`.
+     * - `quorum=bravo` means that only For votes are counted towards quorum.
+     * - `quorum=for,abstain` means that both For and Abstain votes are counted towards quorum.
+     *
+     * NOTE: The string can be decoded by the standard
+     * https://developer.mozilla.org/en-US/docs/Web/API/URLSearchParams[`URLSearchParams`]
+     * JavaScript class.
+     */
+    // solhint-disable-next-line func-name-mixedcase
+    function COUNTING_MODE() public pure virtual returns (string memory);
+
+    /**
+     * @notice module:core
+     * @dev Hashing function used to (re)build the proposal id from the proposal details..
+     */
+    function hashProposal(
+        address[] calldata targets,
+        uint256[] calldata values,
+        bytes[] calldata calldatas,
+        bytes32 descriptionHash
+    ) public pure virtual returns (uint256);
+
+    /**
+     * @notice module:core
+     * @dev Current state of a proposal, following Compound's convention
+     */
+    function state(uint256 proposalId) public view virtual returns (ProposalState);
+
+    /**
+     * @notice module:core
+     * @dev block number used to retrieve user's votes and quorum.
+     */
+    function proposalSnapshot(uint256 proposalId) public view virtual returns (uint256);
+
+    /**
+     * @notice module:core
+     * @dev timestamp at which votes close.
+     */
+    function proposalDeadline(uint256 proposalId) public view virtual returns (uint256);
+
+    /**
+     * @notice module:user-config
+     * @dev delay, in number of block, between the proposal is created and the vote starts. This can be increassed to
+     * leave time for users to buy voting power, of delegate it, before the voting of a proposal starts.
+     */
+    function votingDelay() public view virtual returns (uint256);
+
+    /**
+     * @notice module:user-config
+     * @dev delay, in number of blocks, between the vote start and vote ends.
+     *
+     * Note: the {votingDelay} can delay the start of the vote. This must be considered when setting the voting
+     * duration compared to the voting delay.
+     */
+    function votingPeriod() public view virtual returns (uint256);
+
+    /**
+     * @notice module:user-config
+     * @dev Minimum number of cast voted required for a proposal to be successful.
+     *
+     * Note: The `blockNumber` parameter corresponds to the snaphot used for counting vote. This allows to scale the
+     * quroum depending on values such as the totalSupply of a token at this block (see {ERC20Votes}).
+     */
+    function quorum(uint256 blockNumber) public view virtual returns (uint256);
+
+    /**
+     * @notice module:reputation
+     * @dev Voting power of an `account` at a specific `blockNumber`.
+     *
+     * Note: this can be implemented in a number of ways, for example by reading the delegated balance from one (or
+     * multiple), {ERC20Votes} tokens.
+     */
+    function getVotes(address account, uint256 blockNumber) public view virtual returns (uint256);
+
+    /**
+     * @notice module:voting
+     * @dev Returns weither `account` has cast a vote on `proposalId`.
+     */
+    function hasVoted(uint256 proposalId, address account) public view virtual returns (bool);
+
+    /**
+     * @dev Create a new proposal. Vote start {IGovernor-votingDelay} blocks after the proposal is created and ends
+     * {IGovernor-votingPeriod} blocks after the voting starts.
+     *
+     * Emits a {ProposalCreated} event.
+     */
+    function propose(
+        address[] memory targets,
+        uint256[] memory values,
+        bytes[] memory calldatas,
+        string memory description
+    ) public virtual returns (uint256 proposalId);
+
+    /**
+     * @dev Execute a successful proposal. This requires the quorum to be reached, the vote to be successful, and the
+     * deadline to be reached.
+     *
+     * Emits a {ProposalExecuted} event.
+     *
+     * Note: some module can modify the requirements for execution, for example by adding an additional timelock.
+     */
+    function execute(
+        address[] memory targets,
+        uint256[] memory values,
+        bytes[] memory calldatas,
+        bytes32 descriptionHash
+    ) public payable virtual returns (uint256 proposalId);
+
+    /**
+     * @dev Cast a vote
+     *
+     * Emits a {VoteCast} event.
+     */
+    function castVote(uint256 proposalId, uint8 support) public virtual returns (uint256 balance);
+
+    /**
+     * @dev Cast a with a reason
+     *
+     * Emits a {VoteCast} event.
+     */
+    function castVoteWithReason(
+        uint256 proposalId,
+        uint8 support,
+        string calldata reason
+    ) public virtual returns (uint256 balance);
+
+    /**
+     * @dev Cast a vote using the user cryptographic signature.
+     *
+     * Emits a {VoteCast} event.
+     */
+    function castVoteBySig(
+        uint256 proposalId,
+        uint8 support,
+        uint8 v,
+        bytes32 r,
+        bytes32 s
+    ) public virtual returns (uint256 balance);
+}

contracts/governance/README.adoc

@@ -0,0 +1,164 @@
+= Governance
+
+[.readme-notice]
+NOTE: This document is better viewed at https://docs.openzeppelin.com/contracts/api/governance
+
+This directory includes primitives for on-chain governance.
+
+== Governor
+
+This modular system of Governor contracts allows the deployment on-chain voting protocols similar to https://compound.finance/docs/governance[Compound's Governor Alpha & Bravo] and beyond, through the ability to easily customize multiple aspects of the protocol.
+
+[TIP]
+====
+For a guided experience, set up your Governor contract using https://wizard.openzeppelin.com/#governor[Contracts Wizard].
+
+For a written walkthrough, check out our guide on xref:ROOT:governance.adoc[How to set up on-chain governance].
+====
+
+* {Governor}: The core contract that contains all the logic and primitives. It is abstract and requires choosing one of each of the modules below, or custom ones.
+
+Votes modules determine the source of voting power, and sometimes quorum number.
+
+* {GovernorVotes}: Extracts voting weight from an {ERC20Votes} token.
+
+* {GovernorVotesComp}: Extracts voting weight from a COMP-like or {ERC20VotesComp} token.
+
+* {GovernorVotesQuorumFraction}: Combines with `GovernorVotes` to set the quorum as a fraction of the total token supply.
+
+Counting modules determine valid voting options.
+
+* {GovernorCountingSimple}: Simple voting mechanism with 3 voting options: Against, For and Abstain.
+
+Timelock extensions add a delay for governance decisions to be executed. The workflow is extended to require a `queue` step before execution. With these modules, proposals are executed by the external timelock contract, thus it is the timelock that has to hold the assets that are being governed.
+
+* {GovernorTimelockControl}: Connects with an instance of {TimelockController}. Allows multiple proposers and executors, in addition to the Governor itself.
+
+* {GovernorTimelockCompound}: Connects with an instance of Compound's https://github.com/compound-finance/compound-protocol/blob/master/contracts/Timelock.sol[`Timelock`] contract.
+
+Other extensions can customize the behavior or interface in multiple ways.
+
+* {GovernorCompatibilityBravo}: Extends the interface to be fully `GovernorBravo`-compatible. Note that events are compatible regardless of whether this extension is included or not.
+
+* {GovernorProposalThreshold}: Restricts proposals to delegates with a minimum voting power.
+
+In addition to modules and extensions, the core contract requires a few virtual functions to be implemented to your particular specifications:
+
+* <<Governor-votingDelay-,`votingDelay()`>>: Delay (in number of blocks) since the proposal is submitted until voting power is fixed and voting starts. This can be used to enforce a delay after a proposal is published for users to buy tokens, or delegate their votes.
+* <<Governor-votingPeriod-,`votingPeriod()`>>: Delay (in number of blocks) since the proposal starts until voting ends.
+* <<Governor-quorum-uint256-,`quorum(uint256 blockNumber)`>>: Quorum required for a proposal to be successful. This function includes a `blockNumber` argument so the quorum can adapt through time, for example, to follow a token's `totalSupply`.
+
+NOTE: Functions of the `Governor` contract do not include access control. If you want to restrict access, you should add these checks by overloading the particular functions. Among these, {Governor-_cancel} is internal by default, and you will have to expose it (which the right access control mechanism) yourself if this function is needed.
+
+=== Core
+
+{{IGovernor}}
+
+{{Governor}}
+
+=== Modules
+
+{{GovernorCountingSimple}}
+
+{{GovernorVotes}}
+
+{{GovernorVotesQuorumFraction}}
+
+{{GovernorVotesComp}}
+
+=== Extensions
+
+{{GovernorTimelockControl}}
+
+{{GovernorTimelockCompound}}
+
+{{GovernorProposalThreshold}}
+
+{{GovernorCompatibilityBravo}}
+
+== Timelock
+
+In a governance system, the {TimelockController} contract is in carge of introducing a delay between a proposal and its execution. It can be used with or without a {Governor}.
+
+{{TimelockController}}
+
+[[timelock-terminology]]
+==== Terminology
+
+* *Operation:* A transaction (or a set of transactions) that is the subject of the timelock. It has to be scheduled by a proposer and executed by an executor. The timelock enforces a minimum delay between the proposition and the execution (see xref:access-control.adoc#operation_lifecycle[operation lifecycle]). If the operation contains multiple transactions (batch mode), they are executed atomically. Operations are identified by the hash of their content.
+* *Operation status:*
+** *Unset:* An operation that is not part of the timelock mechanism.
+** *Pending:* An operation that has been scheduled, before the timer expires.
+** *Ready:* An operation that has been scheduled, after the timer expires.
+** *Done:* An operation that has been executed.
+* *Predecessor*: An (optional) dependency between operations. An operation can depend on another operation (its predecessor), forcing the execution order of these two operations.
+* *Role*:
+** *Admin:* An address (smart contract or EOA) that is in charge of granting the roles of Proposer and Executor.
+** *Proposer:* An address (smart contract or EOA) that is in charge of scheduling (and cancelling) operations.
+** *Executor:* An address (smart contract or EOA) that is in charge of executing operations once the timelock has expired. This role can be given to the zero address to allow anyone to execute operations.
+
+[[timelock-operation]]
+==== Operation structure
+
+Operation executed by the xref:api:governance.adoc#TimelockController[`TimelockController`] can contain one or multiple subsequent calls. Depending on whether you need to multiple calls to be executed atomically, you can either use simple or batched operations.
+
+Both operations contain:
+
+* *Target*, the address of the smart contract that the timelock should operate on.
+* *Value*, in wei, that should be sent with the transaction. Most of the time this will be 0. Ether can be deposited before-end or passed along when executing the transaction.
+* *Data*, containing the encoded function selector and parameters of the call. This can be produced using a number of tools. For example, a maintenance operation granting role `ROLE` to `ACCOUNT` can be encode using web3js as follows:
+
+```javascript
+const data = timelock.contract.methods.grantRole(ROLE, ACCOUNT).encodeABI()
+```
+
+* *Predecessor*, that specifies a dependency between operations. This dependency is optional. Use `bytes32(0)` if the operation does not have any dependency.
+* *Salt*, used to disambiguate two otherwise identical operations. This can be any random value.
+
+In the case of batched operations, `target`, `value` and `data` are specified as arrays, which must be of the same length.
+
+[[timelock-operation-lifecycle]]
+==== Operation lifecycle
+
+Timelocked operations are identified by a unique id (their hash) and follow a specific lifecycle:
+
+`Unset` -> `Pending` -> `Pending` + `Ready` -> `Done`
+
+* By calling xref:api:governance.adoc#TimelockController-schedule-address-uint256-bytes-bytes32-bytes32-uint256-[`schedule`] (or xref:api:governance.adoc#TimelockController-scheduleBatch-address---uint256---bytes---bytes32-bytes32-uint256-[`scheduleBatch`]), a proposer moves the operation from the `Unset` to the `Pending` state. This starts a timer that must be longer than the minimum delay. The timer expires at a timestamp accessible through the xref:api:governance.adoc#TimelockController-getTimestamp-bytes32-[`getTimestamp`] method.
+* Once the timer expires, the operation automatically gets the `Ready` state. At this point, it can be executed.
+* By calling xref:api:governance.adoc#TimelockController-TimelockController-execute-address-uint256-bytes-bytes32-bytes32-[`execute`] (or xref:api:governance.adoc#TimelockController-executeBatch-address---uint256---bytes---bytes32-bytes32-[`executeBatch`]), an executor triggers the operation's underlying transactions and moves it to the `Done` state. If the operation has a predecessor, it has to be in the `Done` state for this transition to succeed.
+* xref:api:governance.adoc#TimelockController-TimelockController-cancel-bytes32-[`cancel`] allows proposers to cancel any `Pending` operation. This resets the operation to the `Unset` state. It is thus possible for a proposer to re-schedule an operation that has been cancelled. In this case, the timer restarts when the operation is re-scheduled.
+
+Operations status can be queried using the functions:
+
+* xref:api:governance.adoc#TimelockController-isOperationPending-bytes32-[`isOperationPending(bytes32)`]
+* xref:api:governance.adoc#TimelockController-isOperationReady-bytes32-[`isOperationReady(bytes32)`]
+* xref:api:governance.adoc#TimelockController-isOperationDone-bytes32-[`isOperationDone(bytes32)`]
+
+[[timelock-roles]]
+==== Roles
+
+[[timelock-admin]]
+===== Admin
+
+The admins are in charge of managing proposers and executors. For the timelock to be self-governed, this role should only be given to the timelock itself. Upon deployment, both the timelock and the deployer have this role. After further configuration and testing, the deployer can renounce this role such that all further maintenance operations have to go through the timelock process.
+
+This role is identified by the *TIMELOCK_ADMIN_ROLE* value: `0x5f58e3a2316349923ce3780f8d587db2d72378aed66a8261c916544fa6846ca5`
+
+[[timelock-proposer]]
+===== Proposer
+
+The proposers are in charge of scheduling (and cancelling) operations. This is a critical role, that should be given to governing entities. This could be an EOA, a multisig, or a DAO.
+
+WARNING: *Proposer fight:* Having multiple proposers, while providing redundancy in case one becomes unavailable, can be dangerous. As proposer have their say on all operations, they could cancel operations they disagree with, including operations to remove them for the proposers.
+
+This role is identified by the *PROPOSER_ROLE* value: `0xb09aa5aeb3702cfd50b6b62bc4532604938f21248a27a1d5ca736082b6819cc1`
+
+[[timelock-executor]]
+===== Executor
+
+The executors are in charge of executing the operations scheduled by the proposers once the timelock expires. Logic dictates that multisig or DAO that are proposers should also be executors in order to guarantee operations that have been scheduled will eventually be executed. However, having additional executors can reduce the cost (the executing transaction does not require validation by the multisig or DAO that proposed it), while ensuring whoever is in charge of execution cannot trigger actions that have not been scheduled by the proposers. Alternatively, it is possible to allow _any_ address to execute a proposal once the timelock has expired by granting the executor role to the zero address.
+
+This role is identified by the *EXECUTOR_ROLE* value: `0xd8aa0f3194971a2a116679f7c2090f6939c8d4e01a2a8d7e41d55e5351469e63`
+
+WARNING: A live contract without at least one proposer and one executor is locked. Make sure these roles are filled by reliable entities before the deployer renounces its administrative rights in favour of the timelock contract itself. See the {AccessControl} documentation to learn more about role management.

contracts/governance/TimelockController.sol

@@ -0,0 +1,352 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "../access/AccessControl.sol";
+
+/**
+ * @dev Contract module which acts as a timelocked controller. When set as the
+ * owner of an `Ownable` smart contract, it enforces a timelock on all
+ * `onlyOwner` maintenance operations. This gives time for users of the
+ * controlled contract to exit before a potentially dangerous maintenance
+ * operation is applied.
+ *
+ * By default, this contract is self administered, meaning administration tasks
+ * have to go through the timelock process. The proposer (resp executor) role
+ * is in charge of proposing (resp executing) operations. A common use case is
+ * to position this {TimelockController} as the owner of a smart contract, with
+ * a multisig or a DAO as the sole proposer.
+ *
+ * _Available since v3.3._
+ */
+contract TimelockController is AccessControl {
+    bytes32 public constant TIMELOCK_ADMIN_ROLE = keccak256("TIMELOCK_ADMIN_ROLE");
+    bytes32 public constant PROPOSER_ROLE = keccak256("PROPOSER_ROLE");
+    bytes32 public constant EXECUTOR_ROLE = keccak256("EXECUTOR_ROLE");
+    uint256 internal constant _DONE_TIMESTAMP = uint256(1);
+
+    mapping(bytes32 => uint256) private _timestamps;
+    uint256 private _minDelay;
+
+    /**
+     * @dev Emitted when a call is scheduled as part of operation `id`.
+     */
+    event CallScheduled(
+        bytes32 indexed id,
+        uint256 indexed index,
+        address target,
+        uint256 value,
+        bytes data,
+        bytes32 predecessor,
+        uint256 delay
+    );
+
+    /**
+     * @dev Emitted when a call is performed as part of operation `id`.
+     */
+    event CallExecuted(bytes32 indexed id, uint256 indexed index, address target, uint256 value, bytes data);
+
+    /**
+     * @dev Emitted when operation `id` is cancelled.
+     */
+    event Cancelled(bytes32 indexed id);
+
+    /**
+     * @dev Emitted when the minimum delay for future operations is modified.
+     */
+    event MinDelayChange(uint256 oldDuration, uint256 newDuration);
+
+    /**
+     * @dev Initializes the contract with a given `minDelay`.
+     */
+    constructor(
+        uint256 minDelay,
+        address[] memory proposers,
+        address[] memory executors
+    ) {
+        _setRoleAdmin(TIMELOCK_ADMIN_ROLE, TIMELOCK_ADMIN_ROLE);
+        _setRoleAdmin(PROPOSER_ROLE, TIMELOCK_ADMIN_ROLE);
+        _setRoleAdmin(EXECUTOR_ROLE, TIMELOCK_ADMIN_ROLE);
+
+        // deployer + self administration
+        _setupRole(TIMELOCK_ADMIN_ROLE, _msgSender());
+        _setupRole(TIMELOCK_ADMIN_ROLE, address(this));
+
+        // register proposers
+        for (uint256 i = 0; i < proposers.length; ++i) {
+            _setupRole(PROPOSER_ROLE, proposers[i]);
+        }
+
+        // register executors
+        for (uint256 i = 0; i < executors.length; ++i) {
+            _setupRole(EXECUTOR_ROLE, executors[i]);
+        }
+
+        _minDelay = minDelay;
+        emit MinDelayChange(0, minDelay);
+    }
+
+    /**
+     * @dev Modifier to make a function callable only by a certain role. In
+     * addition to checking the sender's role, `address(0)` 's role is also
+     * considered. Granting a role to `address(0)` is equivalent to enabling
+     * this role for everyone.
+     */
+    modifier onlyRoleOrOpenRole(bytes32 role) {
+        if (!hasRole(role, address(0))) {
+            _checkRole(role, _msgSender());
+        }
+        _;
+    }
+
+    /**
+     * @dev Contract might receive/hold ETH as part of the maintenance process.
+     */
+    receive() external payable {}
+
+    /**
+     * @dev Returns whether an id correspond to a registered operation. This
+     * includes both Pending, Ready and Done operations.
+     */
+    function isOperation(bytes32 id) public view virtual returns (bool pending) {
+        return getTimestamp(id) > 0;
+    }
+
+    /**
+     * @dev Returns whether an operation is pending or not.
+     */
+    function isOperationPending(bytes32 id) public view virtual returns (bool pending) {
+        return getTimestamp(id) > _DONE_TIMESTAMP;
+    }
+
+    /**
+     * @dev Returns whether an operation is ready or not.
+     */
+    function isOperationReady(bytes32 id) public view virtual returns (bool ready) {
+        uint256 timestamp = getTimestamp(id);
+        return timestamp > _DONE_TIMESTAMP && timestamp <= block.timestamp;
+    }
+
+    /**
+     * @dev Returns whether an operation is done or not.
+     */
+    function isOperationDone(bytes32 id) public view virtual returns (bool done) {
+        return getTimestamp(id) == _DONE_TIMESTAMP;
+    }
+
+    /**
+     * @dev Returns the timestamp at with an operation becomes ready (0 for
+     * unset operations, 1 for done operations).
+     */
+    function getTimestamp(bytes32 id) public view virtual returns (uint256 timestamp) {
+        return _timestamps[id];
+    }
+
+    /**
+     * @dev Returns the minimum delay for an operation to become valid.
+     *
+     * This value can be changed by executing an operation that calls `updateDelay`.
+     */
+    function getMinDelay() public view virtual returns (uint256 duration) {
+        return _minDelay;
+    }
+
+    /**
+     * @dev Returns the identifier of an operation containing a single
+     * transaction.
+     */
+    function hashOperation(
+        address target,
+        uint256 value,
+        bytes calldata data,
+        bytes32 predecessor,
+        bytes32 salt
+    ) public pure virtual returns (bytes32 hash) {
+        return keccak256(abi.encode(target, value, data, predecessor, salt));
+    }
+
+    /**
+     * @dev Returns the identifier of an operation containing a batch of
+     * transactions.
+     */
+    function hashOperationBatch(
+        address[] calldata targets,
+        uint256[] calldata values,
+        bytes[] calldata datas,
+        bytes32 predecessor,
+        bytes32 salt
+    ) public pure virtual returns (bytes32 hash) {
+        return keccak256(abi.encode(targets, values, datas, predecessor, salt));
+    }
+
+    /**
+     * @dev Schedule an operation containing a single transaction.
+     *
+     * Emits a {CallScheduled} event.
+     *
+     * Requirements:
+     *
+     * - the caller must have the 'proposer' role.
+     */
+    function schedule(
+        address target,
+        uint256 value,
+        bytes calldata data,
+        bytes32 predecessor,
+        bytes32 salt,
+        uint256 delay
+    ) public virtual onlyRole(PROPOSER_ROLE) {
+        bytes32 id = hashOperation(target, value, data, predecessor, salt);
+        _schedule(id, delay);
+        emit CallScheduled(id, 0, target, value, data, predecessor, delay);
+    }
+
+    /**
+     * @dev Schedule an operation containing a batch of transactions.
+     *
+     * Emits one {CallScheduled} event per transaction in the batch.
+     *
+     * Requirements:
+     *
+     * - the caller must have the 'proposer' role.
+     */
+    function scheduleBatch(
+        address[] calldata targets,
+        uint256[] calldata values,
+        bytes[] calldata datas,
+        bytes32 predecessor,
+        bytes32 salt,
+        uint256 delay
+    ) public virtual onlyRole(PROPOSER_ROLE) {
+        require(targets.length == values.length, "TimelockController: length mismatch");
+        require(targets.length == datas.length, "TimelockController: length mismatch");
+
+        bytes32 id = hashOperationBatch(targets, values, datas, predecessor, salt);
+        _schedule(id, delay);
+        for (uint256 i = 0; i < targets.length; ++i) {
+            emit CallScheduled(id, i, targets[i], values[i], datas[i], predecessor, delay);
+        }
+    }
+
+    /**
+     * @dev Schedule an operation that is to becomes valid after a given delay.
+     */
+    function _schedule(bytes32 id, uint256 delay) private {
+        require(!isOperation(id), "TimelockController: operation already scheduled");
+        require(delay >= getMinDelay(), "TimelockController: insufficient delay");
+        _timestamps[id] = block.timestamp + delay;
+    }
+
+    /**
+     * @dev Cancel an operation.
+     *
+     * Requirements:
+     *
+     * - the caller must have the 'proposer' role.
+     */
+    function cancel(bytes32 id) public virtual onlyRole(PROPOSER_ROLE) {
+        require(isOperationPending(id), "TimelockController: operation cannot be cancelled");
+        delete _timestamps[id];
+
+        emit Cancelled(id);
+    }
+
+    /**
+     * @dev Execute an (ready) operation containing a single transaction.
+     *
+     * Emits a {CallExecuted} event.
+     *
+     * Requirements:
+     *
+     * - the caller must have the 'executor' role.
+     */
+    function execute(
+        address target,
+        uint256 value,
+        bytes calldata data,
+        bytes32 predecessor,
+        bytes32 salt
+    ) public payable virtual onlyRoleOrOpenRole(EXECUTOR_ROLE) {
+        bytes32 id = hashOperation(target, value, data, predecessor, salt);
+        _beforeCall(id, predecessor);
+        _call(id, 0, target, value, data);
+        _afterCall(id);
+    }
+
+    /**
+     * @dev Execute an (ready) operation containing a batch of transactions.
+     *
+     * Emits one {CallExecuted} event per transaction in the batch.
+     *
+     * Requirements:
+     *
+     * - the caller must have the 'executor' role.
+     */
+    function executeBatch(
+        address[] calldata targets,
+        uint256[] calldata values,
+        bytes[] calldata datas,
+        bytes32 predecessor,
+        bytes32 salt
+    ) public payable virtual onlyRoleOrOpenRole(EXECUTOR_ROLE) {
+        require(targets.length == values.length, "TimelockController: length mismatch");
+        require(targets.length == datas.length, "TimelockController: length mismatch");
+
+        bytes32 id = hashOperationBatch(targets, values, datas, predecessor, salt);
+        _beforeCall(id, predecessor);
+        for (uint256 i = 0; i < targets.length; ++i) {
+            _call(id, i, targets[i], values[i], datas[i]);
+        }
+        _afterCall(id);
+    }
+
+    /**
+     * @dev Checks before execution of an operation's calls.
+     */
+    function _beforeCall(bytes32 id, bytes32 predecessor) private view {
+        require(isOperationReady(id), "TimelockController: operation is not ready");
+        require(predecessor == bytes32(0) || isOperationDone(predecessor), "TimelockController: missing dependency");
+    }
+
+    /**
+     * @dev Checks after execution of an operation's calls.
+     */
+    function _afterCall(bytes32 id) private {
+        require(isOperationReady(id), "TimelockController: operation is not ready");
+        _timestamps[id] = _DONE_TIMESTAMP;
+    }
+
+    /**
+     * @dev Execute an operation's call.
+     *
+     * Emits a {CallExecuted} event.
+     */
+    function _call(
+        bytes32 id,
+        uint256 index,
+        address target,
+        uint256 value,
+        bytes calldata data
+    ) private {
+        (bool success, ) = target.call{value: value}(data);
+        require(success, "TimelockController: underlying transaction reverted");
+
+        emit CallExecuted(id, index, target, value, data);
+    }
+
+    /**
+     * @dev Changes the minimum timelock duration for future operations.
+     *
+     * Emits a {MinDelayChange} event.
+     *
+     * Requirements:
+     *
+     * - the caller must be the timelock itself. This can only be achieved by scheduling and later executing
+     * an operation where the timelock is the target and the data is the ABI-encoded call to this function.
+     */
+    function updateDelay(uint256 newDelay) external virtual {
+        require(msg.sender == address(this), "TimelockController: caller must be timelock");
+        emit MinDelayChange(_minDelay, newDelay);
+        _minDelay = newDelay;
+    }
+}

contracts/governance/compatibility/GovernorCompatibilityBravo.sol

@@ -0,0 +1,301 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "../../utils/Counters.sol";
+import "../../utils/math/SafeCast.sol";
+import "../extensions/IGovernorTimelock.sol";
+import "../extensions/GovernorProposalThreshold.sol";
+import "../Governor.sol";
+import "./IGovernorCompatibilityBravo.sol";
+
+/**
+ * @dev Compatibility layer that implements GovernorBravo compatibility on to of {Governor}.
+ *
+ * This compatibility layer includes a voting system and requires a {IGovernorTimelock} compatible module to be added
+ * through inheritance. It does not include token bindings, not does it include any variable upgrade patterns.
+ *
+ * _Available since v4.3._
+ */
+abstract contract GovernorCompatibilityBravo is
+    IGovernorTimelock,
+    IGovernorCompatibilityBravo,
+    Governor,
+    GovernorProposalThreshold
+{
+    using Counters for Counters.Counter;
+    using Timers for Timers.BlockNumber;
+
+    enum VoteType {
+        Against,
+        For,
+        Abstain
+    }
+
+    struct ProposalDetails {
+        address proposer;
+        address[] targets;
+        uint256[] values;
+        string[] signatures;
+        bytes[] calldatas;
+        uint256 forVotes;
+        uint256 againstVotes;
+        uint256 abstainVotes;
+        mapping(address => Receipt) receipts;
+        bytes32 descriptionHash;
+    }
+
+    mapping(uint256 => ProposalDetails) private _proposalDetails;
+
+    // solhint-disable-next-line func-name-mixedcase
+    function COUNTING_MODE() public pure virtual override returns (string memory) {
+        return "support=bravo&quorum=bravo";
+    }
+
+    // ============================================== Proposal lifecycle ==============================================
+    /**
+     * @dev See {IGovernor-propose}.
+     */
+    function propose(
+        address[] memory targets,
+        uint256[] memory values,
+        bytes[] memory calldatas,
+        string memory description
+    ) public virtual override(IGovernor, Governor, GovernorProposalThreshold) returns (uint256) {
+        _storeProposal(_msgSender(), targets, values, new string[](calldatas.length), calldatas, description);
+        return super.propose(targets, values, calldatas, description);
+    }
+
+    /**
+     * @dev See {IGovernorCompatibilityBravo-propose}.
+     */
+    function propose(
+        address[] memory targets,
+        uint256[] memory values,
+        string[] memory signatures,
+        bytes[] memory calldatas,
+        string memory description
+    ) public virtual override returns (uint256) {
+        _storeProposal(_msgSender(), targets, values, signatures, calldatas, description);
+        return propose(targets, values, _encodeCalldata(signatures, calldatas), description);
+    }
+
+    /**
+     * @dev See {IGovernorCompatibilityBravo-queue}.
+     */
+    function queue(uint256 proposalId) public virtual override {
+        ProposalDetails storage details = _proposalDetails[proposalId];
+        queue(
+            details.targets,
+            details.values,
+            _encodeCalldata(details.signatures, details.calldatas),
+            details.descriptionHash
+        );
+    }
+
+    /**
+     * @dev See {IGovernorCompatibilityBravo-execute}.
+     */
+    function execute(uint256 proposalId) public payable virtual override {
+        ProposalDetails storage details = _proposalDetails[proposalId];
+        execute(
+            details.targets,
+            details.values,
+            _encodeCalldata(details.signatures, details.calldatas),
+            details.descriptionHash
+        );
+    }
+
+    function cancel(uint256 proposalId) public virtual override {
+        ProposalDetails storage details = _proposalDetails[proposalId];
+
+        require(
+            _msgSender() == details.proposer || getVotes(details.proposer, block.number - 1) < proposalThreshold(),
+            "GovernorBravo: proposer above threshold"
+        );
+
+        _cancel(
+            details.targets,
+            details.values,
+            _encodeCalldata(details.signatures, details.calldatas),
+            details.descriptionHash
+        );
+    }
+
+    /**
+     * @dev Encodes calldatas with optional function signature.
+     */
+    function _encodeCalldata(string[] memory signatures, bytes[] memory calldatas)
+        private
+        pure
+        returns (bytes[] memory)
+    {
+        bytes[] memory fullcalldatas = new bytes[](calldatas.length);
+
+        for (uint256 i = 0; i < signatures.length; ++i) {
+            fullcalldatas[i] = bytes(signatures[i]).length == 0
+                ? calldatas[i]
+                : abi.encodeWithSignature(signatures[i], calldatas[i]);
+        }
+
+        return fullcalldatas;
+    }
+
+    /**
+     * @dev Store proposal metadata for later lookup
+     */
+    function _storeProposal(
+        address proposer,
+        address[] memory targets,
+        uint256[] memory values,
+        string[] memory signatures,
+        bytes[] memory calldatas,
+        string memory description
+    ) private {
+        bytes32 descriptionHash = keccak256(bytes(description));
+        uint256 proposalId = hashProposal(targets, values, _encodeCalldata(signatures, calldatas), descriptionHash);
+
+        ProposalDetails storage details = _proposalDetails[proposalId];
+        if (details.descriptionHash == bytes32(0)) {
+            details.proposer = proposer;
+            details.targets = targets;
+            details.values = values;
+            details.signatures = signatures;
+            details.calldatas = calldatas;
+            details.descriptionHash = descriptionHash;
+        }
+    }
+
+    // ==================================================== Views =====================================================
+    /**
+     * @dev Part of the Governor Bravo's interface: _"The number of votes required in order for a voter to become a proposer"_.
+     */
+    function proposalThreshold()
+        public
+        view
+        virtual
+        override(IGovernorCompatibilityBravo, GovernorProposalThreshold)
+        returns (uint256);
+
+    /**
+     * @dev See {IGovernorCompatibilityBravo-proposals}.
+     */
+    function proposals(uint256 proposalId)
+        public
+        view
+        virtual
+        override
+        returns (
+            uint256 id,
+            address proposer,
+            uint256 eta,
+            uint256 startBlock,
+            uint256 endBlock,
+            uint256 forVotes,
+            uint256 againstVotes,
+            uint256 abstainVotes,
+            bool canceled,
+            bool executed
+        )
+    {
+        id = proposalId;
+        eta = proposalEta(proposalId);
+        startBlock = proposalSnapshot(proposalId);
+        endBlock = proposalDeadline(proposalId);
+
+        ProposalDetails storage details = _proposalDetails[proposalId];
+        proposer = details.proposer;
+        forVotes = details.forVotes;
+        againstVotes = details.againstVotes;
+        abstainVotes = details.abstainVotes;
+
+        ProposalState status = state(proposalId);
+        canceled = status == ProposalState.Canceled;
+        executed = status == ProposalState.Executed;
+    }
+
+    /**
+     * @dev See {IGovernorCompatibilityBravo-getActions}.
+     */
+    function getActions(uint256 proposalId)
+        public
+        view
+        virtual
+        override
+        returns (
+            address[] memory targets,
+            uint256[] memory values,
+            string[] memory signatures,
+            bytes[] memory calldatas
+        )
+    {
+        ProposalDetails storage details = _proposalDetails[proposalId];
+        return (details.targets, details.values, details.signatures, details.calldatas);
+    }
+
+    /**
+     * @dev See {IGovernorCompatibilityBravo-getReceipt}.
+     */
+    function getReceipt(uint256 proposalId, address voter) public view virtual override returns (Receipt memory) {
+        return _proposalDetails[proposalId].receipts[voter];
+    }
+
+    /**
+     * @dev See {IGovernorCompatibilityBravo-quorumVotes}.
+     */
+    function quorumVotes() public view virtual override returns (uint256) {
+        return quorum(block.number - 1);
+    }
+
+    // ==================================================== Voting ====================================================
+    /**
+     * @dev See {IGovernor-hasVoted}.
+     */
+    function hasVoted(uint256 proposalId, address account) public view virtual override returns (bool) {
+        return _proposalDetails[proposalId].receipts[account].hasVoted;
+    }
+
+    /**
+     * @dev See {Governor-_quorumReached}. In this module, only forVotes count toward the quorum.
+     */
+    function _quorumReached(uint256 proposalId) internal view virtual override returns (bool) {
+        ProposalDetails storage details = _proposalDetails[proposalId];
+        return quorum(proposalSnapshot(proposalId)) < details.forVotes;
+    }
+
+    /**
+     * @dev See {Governor-_voteSucceeded}. In this module, the forVotes must be scritly over the againstVotes.
+     */
+    function _voteSucceeded(uint256 proposalId) internal view virtual override returns (bool) {
+        ProposalDetails storage details = _proposalDetails[proposalId];
+        return details.forVotes > details.againstVotes;
+    }
+
+    /**
+     * @dev See {Governor-_countVote}. In this module, the support follows Governor Bravo.
+     */
+    function _countVote(
+        uint256 proposalId,
+        address account,
+        uint8 support,
+        uint256 weight
+    ) internal virtual override {
+        ProposalDetails storage details = _proposalDetails[proposalId];
+        Receipt storage receipt = details.receipts[account];
+
+        require(!receipt.hasVoted, "GovernorCompatibilityBravo: vote already cast");
+        receipt.hasVoted = true;
+        receipt.support = support;
+        receipt.votes = SafeCast.toUint96(weight);
+
+        if (support == uint8(VoteType.Against)) {
+            details.againstVotes += weight;
+        } else if (support == uint8(VoteType.For)) {
+            details.forVotes += weight;
+        } else if (support == uint8(VoteType.Abstain)) {
+            details.abstainVotes += weight;
+        } else {
+            revert("GovernorCompatibilityBravo: invalid vote type");
+        }
+    }
+}

contracts/governance/compatibility/IGovernorCompatibilityBravo.sol

@@ -0,0 +1,118 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "../IGovernor.sol";
+
+/**
+ * @dev Interface extension that adds missing functions to the {Governor} core to provide `GovernorBravo` compatibility.
+ *
+ * _Available since v4.3._
+ */
+abstract contract IGovernorCompatibilityBravo is IGovernor {
+    /**
+     * @dev Proposal structure from Compound Governor Bravo. Not actually used by the compatibility layer, as
+     * {{proposal}} returns a very different structure.
+     */
+    struct Proposal {
+        uint256 id;
+        address proposer;
+        uint256 eta;
+        address[] targets;
+        uint256[] values;
+        string[] signatures;
+        bytes[] calldatas;
+        uint256 startBlock;
+        uint256 endBlock;
+        uint256 forVotes;
+        uint256 againstVotes;
+        uint256 abstainVotes;
+        bool canceled;
+        bool executed;
+        mapping(address => Receipt) receipts;
+    }
+
+    /**
+     * @dev Receipt structure from Compound Governor Bravo
+     */
+    struct Receipt {
+        bool hasVoted;
+        uint8 support;
+        uint96 votes;
+    }
+
+    /**
+     * @dev Part of the Governor Bravo's interface.
+     */
+    function quorumVotes() public view virtual returns (uint256);
+
+    /**
+     * @dev Part of the Governor Bravo's interface: _"The official record of all proposals ever proposed"_.
+     */
+    function proposals(uint256)
+        public
+        view
+        virtual
+        returns (
+            uint256 id,
+            address proposer,
+            uint256 eta,
+            uint256 startBlock,
+            uint256 endBlock,
+            uint256 forVotes,
+            uint256 againstVotes,
+            uint256 abstainVotes,
+            bool canceled,
+            bool executed
+        );
+
+    /**
+     * @dev Part of the Governor Bravo's interface: _"Function used to propose a new proposal"_.
+     */
+    function propose(
+        address[] memory targets,
+        uint256[] memory values,
+        string[] memory signatures,
+        bytes[] memory calldatas,
+        string memory description
+    ) public virtual returns (uint256);
+
+    /**
+     * @dev Part of the Governor Bravo's interface: _"Queues a proposal of state succeeded"_.
+     */
+    function queue(uint256 proposalId) public virtual;
+
+    /**
+     * @dev Part of the Governor Bravo's interface: _"Executes a queued proposal if eta has passed"_.
+     */
+    function execute(uint256 proposalId) public payable virtual;
+
+    /**
+     * @dev Cancels a proposal only if sender is the proposer, or proposer delegates dropped below proposal threshold.
+     */
+    function cancel(uint256 proposalId) public virtual;
+
+    /**
+     * @dev Part of the Governor Bravo's interface: _"Gets actions of a proposal"_.
+     */
+    function getActions(uint256 proposalId)
+        public
+        view
+        virtual
+        returns (
+            address[] memory targets,
+            uint256[] memory values,
+            string[] memory signatures,
+            bytes[] memory calldatas
+        );
+
+    /**
+     * @dev Part of the Governor Bravo's interface: _"Gets the receipt for a voter on a given proposal"_.
+     */
+    function getReceipt(uint256 proposalId, address voter) public view virtual returns (Receipt memory);
+
+    /**
+     * @dev Part of the Governor Bravo's interface: _"The number of votes required in order for a voter to become a proposer"_.
+     */
+    function proposalThreshold() public view virtual returns (uint256);
+}

contracts/governance/extensions/GovernorCountingSimple.sol

@@ -0,0 +1,105 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "../Governor.sol";
+
+/**
+ * @dev Extension of {Governor} for simple, 3 options, vote counting.
+ *
+ * _Available since v4.3._
+ */
+abstract contract GovernorCountingSimple is Governor {
+    /**
+     * @dev Supported vote types. Matches Governor Bravo ordering.
+     */
+    enum VoteType {
+        Against,
+        For,
+        Abstain
+    }
+
+    struct ProposalVote {
+        uint256 againstVotes;
+        uint256 forVotes;
+        uint256 abstainVotes;
+        mapping(address => bool) hasVoted;
+    }
+
+    mapping(uint256 => ProposalVote) private _proposalVotes;
+
+    /**
+     * @dev See {IGovernor-COUNTING_MODE}.
+     */
+    // solhint-disable-next-line func-name-mixedcase
+    function COUNTING_MODE() public pure virtual override returns (string memory) {
+        return "support=bravo&quorum=for,abstain";
+    }
+
+    /**
+     * @dev See {IGovernor-hasVoted}.
+     */
+    function hasVoted(uint256 proposalId, address account) public view virtual override returns (bool) {
+        return _proposalVotes[proposalId].hasVoted[account];
+    }
+
+    /**
+     * @dev Accessor to the internal vote counts.
+     */
+    function proposalVotes(uint256 proposalId)
+        public
+        view
+        virtual
+        returns (
+            uint256 againstVotes,
+            uint256 forVotes,
+            uint256 abstainVotes
+        )
+    {
+        ProposalVote storage proposalvote = _proposalVotes[proposalId];
+        return (proposalvote.againstVotes, proposalvote.forVotes, proposalvote.abstainVotes);
+    }
+
+    /**
+     * @dev See {Governor-_quorumReached}.
+     */
+    function _quorumReached(uint256 proposalId) internal view virtual override returns (bool) {
+        ProposalVote storage proposalvote = _proposalVotes[proposalId];
+
+        return quorum(proposalSnapshot(proposalId)) <= proposalvote.forVotes + proposalvote.abstainVotes;
+    }
+
+    /**
+     * @dev See {Governor-_voteSucceeded}. In this module, the forVotes must be scritly over the againstVotes.
+     */
+    function _voteSucceeded(uint256 proposalId) internal view virtual override returns (bool) {
+        ProposalVote storage proposalvote = _proposalVotes[proposalId];
+
+        return proposalvote.forVotes > proposalvote.againstVotes;
+    }
+
+    /**
+     * @dev See {Governor-_countVote}. In this module, the support follows the `VoteType` enum (from Governor Bravo).
+     */
+    function _countVote(
+        uint256 proposalId,
+        address account,
+        uint8 support,
+        uint256 weight
+    ) internal virtual override {
+        ProposalVote storage proposalvote = _proposalVotes[proposalId];
+
+        require(!proposalvote.hasVoted[account], "GovernorVotingSimple: vote already cast");
+        proposalvote.hasVoted[account] = true;
+
+        if (support == uint8(VoteType.Against)) {
+            proposalvote.againstVotes += weight;
+        } else if (support == uint8(VoteType.For)) {
+            proposalvote.forVotes += weight;
+        } else if (support == uint8(VoteType.Abstain)) {
+            proposalvote.abstainVotes += weight;
+        } else {
+            revert("GovernorVotingSimple: invalid value for enum VoteType");
+        }
+    }
+}

contracts/governance/extensions/GovernorProposalThreshold.sol

@@ -0,0 +1,34 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "../Governor.sol";
+
+/**
+ * @dev Extension of {Governor} for proposal restriction to token holders with a minimum balance.
+ *
+ * _Available since v4.3._
+ */
+abstract contract GovernorProposalThreshold is Governor {
+    /**
+     * @dev See {IGovernor-propose}.
+     */
+    function propose(
+        address[] memory targets,
+        uint256[] memory values,
+        bytes[] memory calldatas,
+        string memory description
+    ) public virtual override returns (uint256) {
+        require(
+            getVotes(msg.sender, block.number - 1) >= proposalThreshold(),
+            "GovernorCompatibilityBravo: proposer votes below proposal threshold"
+        );
+
+        return super.propose(targets, values, calldatas, description);
+    }
+
+    /**
+     * @dev Part of the Governor Bravo's interface: _"The number of votes required in order for a voter to become a proposer"_.
+     */
+    function proposalThreshold() public view virtual returns (uint256);
+}

contracts/governance/extensions/GovernorTimelockCompound.sol

@@ -0,0 +1,242 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "./IGovernorTimelock.sol";
+import "../Governor.sol";
+import "../../utils/math/SafeCast.sol";
+
+/**
+ * https://github.com/compound-finance/compound-protocol/blob/master/contracts/Timelock.sol[Compound's timelock] interface
+ */
+interface ICompoundTimelock {
+    receive() external payable;
+
+    // solhint-disable-next-line func-name-mixedcase
+    function GRACE_PERIOD() external view returns (uint256);
+
+    // solhint-disable-next-line func-name-mixedcase
+    function MINIMUM_DELAY() external view returns (uint256);
+
+    // solhint-disable-next-line func-name-mixedcase
+    function MAXIMUM_DELAY() external view returns (uint256);
+
+    function admin() external view returns (address);
+
+    function pendingAdmin() external view returns (address);
+
+    function delay() external view returns (uint256);
+
+    function queuedTransactions(bytes32) external view returns (bool);
+
+    function setDelay(uint256) external;
+
+    function acceptAdmin() external;
+
+    function setPendingAdmin(address) external;
+
+    function queueTransaction(
+        address target,
+        uint256 value,
+        string memory signature,
+        bytes memory data,
+        uint256 eta
+    ) external returns (bytes32);
+
+    function cancelTransaction(
+        address target,
+        uint256 value,
+        string memory signature,
+        bytes memory data,
+        uint256 eta
+    ) external;
+
+    function executeTransaction(
+        address target,
+        uint256 value,
+        string memory signature,
+        bytes memory data,
+        uint256 eta
+    ) external payable returns (bytes memory);
+}
+
+/**
+ * @dev Extension of {Governor} that binds the execution process to a Compound Timelock. This adds a delay, enforced by
+ * the external timelock to all successful proposal (in addition to the voting duration). The {Governor} needs to be
+ * the admin of the timelock for any operation to be performed. A public, unrestricted,
+ * {GovernorTimelockCompound-__acceptAdmin} is available to accept ownership of the timelock.
+ *
+ * Using this model means the proposal will be operated by the {TimelockController} and not by the {Governor}. Thus,
+ * the assets and permissions must be attached to the {TimelockController}. Any asset sent to the {Governor} will be
+ * inaccessible.
+ *
+ * _Available since v4.3._
+ */
+abstract contract GovernorTimelockCompound is IGovernorTimelock, Governor {
+    using SafeCast for uint256;
+    using Timers for Timers.Timestamp;
+
+    struct ProposalTimelock {
+        Timers.Timestamp timer;
+    }
+
+    ICompoundTimelock private _timelock;
+
+    mapping(uint256 => ProposalTimelock) private _proposalTimelocks;
+
+    /**
+     * @dev Emitted when the timelock controller used for proposal execution is modified.
+     */
+    event TimelockChange(address oldTimelock, address newTimelock);
+
+    /**
+     * @dev Set the timelock.
+     */
+    constructor(ICompoundTimelock timelockAddress) {
+        _updateTimelock(timelockAddress);
+    }
+
+    /**
+     * @dev See {IERC165-supportsInterface}.
+     */
+    function supportsInterface(bytes4 interfaceId) public view virtual override(IERC165, Governor) returns (bool) {
+        return interfaceId == type(IGovernorTimelock).interfaceId || super.supportsInterface(interfaceId);
+    }
+
+    /**
+     * @dev Overriden version of the {Governor-state} function with added support for the `Queued` and `Expired` status.
+     */
+    function state(uint256 proposalId) public view virtual override(IGovernor, Governor) returns (ProposalState) {
+        ProposalState status = super.state(proposalId);
+
+        if (status != ProposalState.Succeeded) {
+            return status;
+        }
+
+        uint256 eta = proposalEta(proposalId);
+        if (eta == 0) {
+            return status;
+        } else if (block.timestamp >= eta + _timelock.GRACE_PERIOD()) {
+            return ProposalState.Expired;
+        } else {
+            return ProposalState.Queued;
+        }
+    }
+
+    /**
+     * @dev Public accessor to check the address of the timelock
+     */
+    function timelock() public view virtual override returns (address) {
+        return address(_timelock);
+    }
+
+    /**
+     * @dev Public accessor to check the eta of a queued proposal
+     */
+    function proposalEta(uint256 proposalId) public view virtual override returns (uint256) {
+        return _proposalTimelocks[proposalId].timer.getDeadline();
+    }
+
+    /**
+     * @dev Function to queue a proposal to the timelock.
+     */
+    function queue(
+        address[] memory targets,
+        uint256[] memory values,
+        bytes[] memory calldatas,
+        bytes32 descriptionHash
+    ) public virtual override returns (uint256) {
+        uint256 proposalId = hashProposal(targets, values, calldatas, descriptionHash);
+
+        require(state(proposalId) == ProposalState.Succeeded, "Governor: proposal not successful");
+
+        uint256 eta = block.timestamp + _timelock.delay();
+        _proposalTimelocks[proposalId].timer.setDeadline(eta.toUint64());
+        for (uint256 i = 0; i < targets.length; ++i) {
+            require(
+                !_timelock.queuedTransactions(keccak256(abi.encode(targets[i], values[i], "", calldatas[i], eta))),
+                "GovernorTimelockCompound: identical proposal action already queued"
+            );
+            _timelock.queueTransaction(targets[i], values[i], "", calldatas[i], eta);
+        }
+
+        emit ProposalQueued(proposalId, eta);
+
+        return proposalId;
+    }
+
+    /**
+     * @dev Overriden execute function that run the already queued proposal through the timelock.
+     */
+    function _execute(
+        uint256 proposalId,
+        address[] memory targets,
+        uint256[] memory values,
+        bytes[] memory calldatas,
+        bytes32 /*descriptionHash*/
+    ) internal virtual override {
+        uint256 eta = proposalEta(proposalId);
+        require(eta > 0, "GovernorTimelockCompound: proposal not yet queued");
+        for (uint256 i = 0; i < targets.length; ++i) {
+            _timelock.executeTransaction{value: values[i]}(targets[i], values[i], "", calldatas[i], eta);
+        }
+    }
+
+    /**
+     * @dev Overriden version of the {Governor-_cancel} function to cancel the timelocked proposal if it as already
+     * been queued.
+     */
+    function _cancel(
+        address[] memory targets,
+        uint256[] memory values,
+        bytes[] memory calldatas,
+        bytes32 descriptionHash
+    ) internal virtual override returns (uint256) {
+        uint256 proposalId = super._cancel(targets, values, calldatas, descriptionHash);
+
+        uint256 eta = proposalEta(proposalId);
+        if (eta > 0) {
+            for (uint256 i = 0; i < targets.length; ++i) {
+                _timelock.cancelTransaction(targets[i], values[i], "", calldatas[i], eta);
+            }
+            _proposalTimelocks[proposalId].timer.reset();
+        }
+
+        return proposalId;
+    }
+
+    /**
+     * @dev Address through which the governor executes action. In this case, the timelock.
+     */
+    function _executor() internal view virtual override returns (address) {
+        return address(_timelock);
+    }
+
+    /**
+     * @dev Accept admin right over the timelock.
+     */
+    // solhint-disable-next-line private-vars-leading-underscore
+    function __acceptAdmin() public {
+        _timelock.acceptAdmin();
+    }
+
+    /**
+     * @dev Public endpoint to update the underlying timelock instance. Restricted to the timelock itself, so updates
+     * must be proposed, scheduled and executed using the {Governor} workflow.
+     *
+     * For security reason, the timelock must be handed over to another admin before setting up a new one. The two
+     * operations (hand over the timelock) and do the update can be batched in a single proposal.
+     *
+     * Note that if the timelock admin has been handed over in a previous operation, we refuse updates made through the
+     * timelock if admin of the timelock has already been accepted and the operation is executed outside the scope of
+     * governance.
+     */
+    function updateTimelock(ICompoundTimelock newTimelock) external virtual onlyGovernance {
+        _updateTimelock(newTimelock);
+    }
+
+    function _updateTimelock(ICompoundTimelock newTimelock) private {
+        emit TimelockChange(address(_timelock), address(newTimelock));
+        _timelock = newTimelock;
+    }
+}

contracts/governance/extensions/GovernorTimelockControl.sol

@@ -0,0 +1,153 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "./IGovernorTimelock.sol";
+import "../Governor.sol";
+import "../TimelockController.sol";
+
+/**
+ * @dev Extension of {Governor} that binds the execution process to an instance of {TimelockController}. This adds a
+ * delay, enforced by the {TimelockController} to all successful proposal (in addition to the voting duration). The
+ * {Governor} needs the proposer (an ideally the executor) roles for the {Governor} to work properly.
+ *
+ * Using this model means the proposal will be operated by the {TimelockController} and not by the {Governor}. Thus,
+ * the assets and permissions must be attached to the {TimelockController}. Any asset sent to the {Governor} will be
+ * inaccessible.
+ *
+ * _Available since v4.3._
+ */
+abstract contract GovernorTimelockControl is IGovernorTimelock, Governor {
+    TimelockController private _timelock;
+    mapping(uint256 => bytes32) private _timelockIds;
+
+    /**
+     * @dev Emitted when the timelock controller used for proposal execution is modified.
+     */
+    event TimelockChange(address oldTimelock, address newTimelock);
+
+    /**
+     * @dev Set the timelock.
+     */
+    constructor(TimelockController timelockAddress) {
+        _updateTimelock(timelockAddress);
+    }
+
+    /**
+     * @dev See {IERC165-supportsInterface}.
+     */
+    function supportsInterface(bytes4 interfaceId) public view virtual override(IERC165, Governor) returns (bool) {
+        return interfaceId == type(IGovernorTimelock).interfaceId || super.supportsInterface(interfaceId);
+    }
+
+    /**
+     * @dev Overriden version of the {Governor-state} function with added support for the `Queued` status.
+     */
+    function state(uint256 proposalId) public view virtual override(IGovernor, Governor) returns (ProposalState) {
+        ProposalState status = super.state(proposalId);
+
+        if (status != ProposalState.Succeeded) {
+            return status;
+        }
+
+        // core tracks execution, so we just have to check if successful proposal have been queued.
+        bytes32 queueid = _timelockIds[proposalId];
+        if (queueid == bytes32(0)) {
+            return status;
+        } else if (_timelock.isOperationDone(queueid)) {
+            return ProposalState.Executed;
+        } else {
+            return ProposalState.Queued;
+        }
+    }
+
+    /**
+     * @dev Public accessor to check the address of the timelock
+     */
+    function timelock() public view virtual override returns (address) {
+        return address(_timelock);
+    }
+
+    /**
+     * @dev Public accessor to check the eta of a queued proposal
+     */
+    function proposalEta(uint256 proposalId) public view virtual override returns (uint256) {
+        uint256 eta = _timelock.getTimestamp(_timelockIds[proposalId]);
+        return eta == 1 ? 0 : eta; // _DONE_TIMESTAMP (1) should be replaced with a 0 value
+    }
+
+    /**
+     * @dev Function to queue a proposal to the timelock.
+     */
+    function queue(
+        address[] memory targets,
+        uint256[] memory values,
+        bytes[] memory calldatas,
+        bytes32 descriptionHash
+    ) public virtual override returns (uint256) {
+        uint256 proposalId = hashProposal(targets, values, calldatas, descriptionHash);
+
+        require(state(proposalId) == ProposalState.Succeeded, "Governor: proposal not successful");
+
+        uint256 delay = _timelock.getMinDelay();
+        _timelockIds[proposalId] = _timelock.hashOperationBatch(targets, values, calldatas, 0, descriptionHash);
+        _timelock.scheduleBatch(targets, values, calldatas, 0, descriptionHash, delay);
+
+        emit ProposalQueued(proposalId, block.timestamp + delay);
+
+        return proposalId;
+    }
+
+    /**
+     * @dev Overriden execute function that run the already queued proposal through the timelock.
+     */
+    function _execute(
+        uint256, /* proposalId */
+        address[] memory targets,
+        uint256[] memory values,
+        bytes[] memory calldatas,
+        bytes32 descriptionHash
+    ) internal virtual override {
+        _timelock.executeBatch{value: msg.value}(targets, values, calldatas, 0, descriptionHash);
+    }
+
+    /**
+     * @dev Overriden version of the {Governor-_cancel} function to cancel the timelocked proposal if it as already
+     * been queued.
+     */
+    function _cancel(
+        address[] memory targets,
+        uint256[] memory values,
+        bytes[] memory calldatas,
+        bytes32 descriptionHash
+    ) internal virtual override returns (uint256) {
+        uint256 proposalId = super._cancel(targets, values, calldatas, descriptionHash);
+
+        if (_timelockIds[proposalId] != 0) {
+            _timelock.cancel(_timelockIds[proposalId]);
+            delete _timelockIds[proposalId];
+        }
+
+        return proposalId;
+    }
+
+    /**
+     * @dev Address through which the governor executes action. In this case, the timelock.
+     */
+    function _executor() internal view virtual override returns (address) {
+        return address(_timelock);
+    }
+
+    /**
+     * @dev Public endpoint to update the underlying timelock instance. Restricted to the timelock itself, so updates
+     * must be proposed, scheduled and executed using the {Governor} workflow.
+     */
+    function updateTimelock(TimelockController newTimelock) external virtual onlyGovernance {
+        _updateTimelock(newTimelock);
+    }
+
+    function _updateTimelock(TimelockController newTimelock) private {
+        emit TimelockChange(address(_timelock), address(newTimelock));
+        _timelock = newTimelock;
+    }
+}

contracts/governance/extensions/GovernorVotes.sol

@@ -0,0 +1,27 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "../Governor.sol";
+import "../../token/ERC20/extensions/ERC20Votes.sol";
+import "../../utils/math/Math.sol";
+
+/**
+ * @dev Extension of {Governor} for voting weight extraction from an {ERC20Votes} token.
+ *
+ * _Available since v4.3._
+ */
+abstract contract GovernorVotes is Governor {
+    ERC20Votes public immutable token;
+
+    constructor(ERC20Votes tokenAddress) {
+        token = tokenAddress;
+    }
+
+    /**
+     * Read the voting weight from the token's built in snapshot mechanism (see {IGovernor-getVotes}).
+     */
+    function getVotes(address account, uint256 blockNumber) public view virtual override returns (uint256) {
+        return token.getPastVotes(account, blockNumber);
+    }
+}

contracts/governance/extensions/GovernorVotesComp.sol

@@ -0,0 +1,26 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "../Governor.sol";
+import "../../token/ERC20/extensions/ERC20VotesComp.sol";
+
+/**
+ * @dev Extension of {Governor} for voting weight extraction from a Comp token.
+ *
+ * _Available since v4.3._
+ */
+abstract contract GovernorVotesComp is Governor {
+    ERC20VotesComp public immutable token;
+
+    constructor(ERC20VotesComp token_) {
+        token = token_;
+    }
+
+    /**
+     * Read the voting weight from the token's built in snapshot mechanism (see {IGovernor-getVotes}).
+     */
+    function getVotes(address account, uint256 blockNumber) public view virtual override returns (uint256) {
+        return token.getPriorVotes(account, blockNumber);
+    }
+}

contracts/governance/extensions/GovernorVotesQuorumFraction.sol

@@ -0,0 +1,49 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "./GovernorVotes.sol";
+
+/**
+ * @dev Extension of {Governor} for voting weight extraction from an {ERC20Votes} token and a quorum expressed as a
+ * fraction of the total supply.
+ *
+ * _Available since v4.3._
+ */
+abstract contract GovernorVotesQuorumFraction is GovernorVotes {
+    uint256 private _quorumNumerator;
+
+    event QuorumNumeratorUpdated(uint256 oldQuorumNumerator, uint256 newQuorumNumerator);
+
+    constructor(uint256 quorumNumeratorValue) {
+        _updateQuorumNumerator(quorumNumeratorValue);
+    }
+
+    function quorumNumerator() public view virtual returns (uint256) {
+        return _quorumNumerator;
+    }
+
+    function quorumDenominator() public view virtual returns (uint256) {
+        return 100;
+    }
+
+    function quorum(uint256 blockNumber) public view virtual override returns (uint256) {
+        return (token.getPastTotalSupply(blockNumber) * quorumNumerator()) / quorumDenominator();
+    }
+
+    function updateQuorumNumerator(uint256 newQuorumNumerator) external virtual onlyGovernance {
+        _updateQuorumNumerator(newQuorumNumerator);
+    }
+
+    function _updateQuorumNumerator(uint256 newQuorumNumerator) internal virtual {
+        require(
+            newQuorumNumerator <= quorumDenominator(),
+            "GovernorVotesQuorumFraction: quorumNumerator over quorumDenominator"
+        );
+
+        uint256 oldQuorumNumerator = _quorumNumerator;
+        _quorumNumerator = newQuorumNumerator;
+
+        emit QuorumNumeratorUpdated(oldQuorumNumerator, newQuorumNumerator);
+    }
+}

contracts/governance/extensions/IGovernorTimelock.sol

@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "../IGovernor.sol";
+
+/**
+ * @dev Extension of the {IGovernor} for timelock supporting modules.
+ *
+ * _Available since v4.3._
+ */
+abstract contract IGovernorTimelock is IGovernor {
+    event ProposalQueued(uint256 proposalId, uint256 eta);
+
+    function timelock() public view virtual returns (address);
+
+    function proposalEta(uint256 proposalId) public view virtual returns (uint256);
+
+    function queue(
+        address[] memory targets,
+        uint256[] memory values,
+        bytes[] memory calldatas,
+        bytes32 descriptionHash
+    ) public virtual returns (uint256 proposalId);
+}

contracts/interfaces/IERC1155.sol

@@ -0,0 +1,5 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "../token/ERC1155/IERC1155.sol";

contracts/interfaces/IERC1155MetadataURI.sol

@@ -0,0 +1,5 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "../token/ERC1155/extensions/IERC1155MetadataURI.sol";

contracts/interfaces/IERC1155Receiver.sol

@@ -0,0 +1,5 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "../token/ERC1155/IERC1155Receiver.sol";

contracts/interfaces/IERC1271.sol

@@ -0,0 +1,18 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+/**
+ * @dev Interface of the ERC1271 standard signature validation method for
+ * contracts as defined in https://eips.ethereum.org/EIPS/eip-1271[ERC-1271].
+ *
+ * _Available since v4.1._
+ */
+interface IERC1271 {
+    /**
+     * @dev Should return whether the signature provided is valid for the provided data
+     * @param hash      Hash of the data to be signed
+     * @param signature Signature byte array associated with _data
+     */
+    function isValidSignature(bytes32 hash, bytes memory signature) external view returns (bytes4 magicValue);
+}

contracts/interfaces/IERC1363.sol

@@ -0,0 +1,94 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "./IERC20.sol";
+import "./IERC165.sol";
+
+interface IERC1363 is IERC165, IERC20 {
+    /*
+     * Note: the ERC-165 identifier for this interface is 0x4bbee2df.
+     * 0x4bbee2df ===
+     *   bytes4(keccak256('transferAndCall(address,uint256)')) ^
+     *   bytes4(keccak256('transferAndCall(address,uint256,bytes)')) ^
+     *   bytes4(keccak256('transferFromAndCall(address,address,uint256)')) ^
+     *   bytes4(keccak256('transferFromAndCall(address,address,uint256,bytes)'))
+     */
+
+    /*
+     * Note: the ERC-165 identifier for this interface is 0xfb9ec8ce.
+     * 0xfb9ec8ce ===
+     *   bytes4(keccak256('approveAndCall(address,uint256)')) ^
+     *   bytes4(keccak256('approveAndCall(address,uint256,bytes)'))
+     */
+
+    /**
+     * @dev Transfer tokens from `msg.sender` to another address and then call `onTransferReceived` on receiver
+     * @param to address The address which you want to transfer to
+     * @param value uint256 The amount of tokens to be transferred
+     * @return true unless throwing
+     */
+    function transferAndCall(address to, uint256 value) external returns (bool);
+
+    /**
+     * @dev Transfer tokens from `msg.sender` to another address and then call `onTransferReceived` on receiver
+     * @param to address The address which you want to transfer to
+     * @param value uint256 The amount of tokens to be transferred
+     * @param data bytes Additional data with no specified format, sent in call to `to`
+     * @return true unless throwing
+     */
+    function transferAndCall(
+        address to,
+        uint256 value,
+        bytes memory data
+    ) external returns (bool);
+
+    /**
+     * @dev Transfer tokens from one address to another and then call `onTransferReceived` on receiver
+     * @param from address The address which you want to send tokens from
+     * @param to address The address which you want to transfer to
+     * @param value uint256 The amount of tokens to be transferred
+     * @return true unless throwing
+     */
+    function transferFromAndCall(
+        address from,
+        address to,
+        uint256 value
+    ) external returns (bool);
+
+    /**
+     * @dev Transfer tokens from one address to another and then call `onTransferReceived` on receiver
+     * @param from address The address which you want to send tokens from
+     * @param to address The address which you want to transfer to
+     * @param value uint256 The amount of tokens to be transferred
+     * @param data bytes Additional data with no specified format, sent in call to `to`
+     * @return true unless throwing
+     */
+    function transferFromAndCall(
+        address from,
+        address to,
+        uint256 value,
+        bytes memory data
+    ) external returns (bool);
+
+    /**
+     * @dev Approve the passed address to spend the specified amount of tokens on behalf of msg.sender
+     * and then call `onApprovalReceived` on spender.
+     * @param spender address The address which will spend the funds
+     * @param value uint256 The amount of tokens to be spent
+     */
+    function approveAndCall(address spender, uint256 value) external returns (bool);
+
+    /**
+     * @dev Approve the passed address to spend the specified amount of tokens on behalf of msg.sender
+     * and then call `onApprovalReceived` on spender.
+     * @param spender address The address which will spend the funds
+     * @param value uint256 The amount of tokens to be spent
+     * @param data bytes Additional data with no specified format, sent in call to `spender`
+     */
+    function approveAndCall(
+        address spender,
+        uint256 value,
+        bytes memory data
+    ) external returns (bool);
+}

contracts/interfaces/IERC1363Receiver.sol

@@ -0,0 +1,31 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+interface IERC1363Receiver {
+    /*
+     * Note: the ERC-165 identifier for this interface is 0x88a7ca5c.
+     * 0x88a7ca5c === bytes4(keccak256("onTransferReceived(address,address,uint256,bytes)"))
+     */
+
+    /**
+     * @notice Handle the receipt of ERC1363 tokens
+     * @dev Any ERC1363 smart contract calls this function on the recipient
+     * after a `transfer` or a `transferFrom`. This function MAY throw to revert and reject the
+     * transfer. Return of other than the magic value MUST result in the
+     * transaction being reverted.
+     * Note: the token contract address is always the message sender.
+     * @param operator address The address which called `transferAndCall` or `transferFromAndCall` function
+     * @param from address The address which are token transferred from
+     * @param value uint256 The amount of tokens transferred
+     * @param data bytes Additional data with no specified format
+     * @return `bytes4(keccak256("onTransferReceived(address,address,uint256,bytes)"))`
+     *  unless throwing
+     */
+    function onTransferReceived(
+        address operator,
+        address from,
+        uint256 value,
+        bytes memory data
+    ) external returns (bytes4);
+}

contracts/interfaces/IERC1363Spender.sol

@@ -0,0 +1,29 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+interface IERC1363Spender {
+    /*
+     * Note: the ERC-165 identifier for this interface is 0x7b04a2d0.
+     * 0x7b04a2d0 === bytes4(keccak256("onApprovalReceived(address,uint256,bytes)"))
+     */
+
+    /**
+     * @notice Handle the approval of ERC1363 tokens
+     * @dev Any ERC1363 smart contract calls this function on the recipient
+     * after an `approve`. This function MAY throw to revert and reject the
+     * approval. Return of other than the magic value MUST result in the
+     * transaction being reverted.
+     * Note: the token contract address is always the message sender.
+     * @param owner address The address which called `approveAndCall` function
+     * @param value uint256 The amount of tokens to be spent
+     * @param data bytes Additional data with no specified format
+     * @return `bytes4(keccak256("onApprovalReceived(address,uint256,bytes)"))`
+     *  unless throwing
+     */
+    function onApprovalReceived(
+        address owner,
+        uint256 value,
+        bytes memory data
+    ) external returns (bytes4);
+}

contracts/interfaces/IERC165.sol

@@ -0,0 +1,5 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "../utils/introspection/IERC165.sol";

contracts/interfaces/IERC1820Implementer.sol

@@ -0,0 +1,5 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "../utils/introspection/IERC1820Implementer.sol";

contracts/interfaces/IERC1820Registry.sol

@@ -0,0 +1,5 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "../utils/introspection/IERC1820Registry.sol";

contracts/interfaces/IERC20.sol

@@ -0,0 +1,5 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "../token/ERC20/IERC20.sol";

contracts/interfaces/IERC20Metadata.sol

@@ -0,0 +1,5 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "../token/ERC20/extensions/IERC20Metadata.sol";

contracts/interfaces/IERC2981.sol

@@ -0,0 +1,22 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "./IERC165.sol";
+
+/**
+ * @dev Interface for the NFT Royalty Standard
+ */
+interface IERC2981 is IERC165 {
+    /**
+     * @dev Called with the sale price to determine how much royalty is owed and to whom.
+     * @param tokenId - the NFT asset queried for royalty information
+     * @param salePrice - the sale price of the NFT asset specified by `tokenId`
+     * @return receiver - address of who should be sent the royalty payment
+     * @return royaltyAmount - the royalty payment amount for `salePrice`
+     */
+    function royaltyInfo(uint256 tokenId, uint256 salePrice)
+        external
+        view
+        returns (address receiver, uint256 royaltyAmount);
+}

contracts/interfaces/IERC3156.sol

@@ -0,0 +1,6 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "./IERC3156FlashBorrower.sol";
+import "./IERC3156FlashLender.sol";

contracts/interfaces/IERC3156FlashBorrower.sol

@@ -0,0 +1,28 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+/**
+ * @dev Interface of the ERC3156 FlashBorrower, as defined in
+ * https://eips.ethereum.org/EIPS/eip-3156[ERC-3156].
+ *
+ * _Available since v4.1._
+ */
+interface IERC3156FlashBorrower {
+    /**
+     * @dev Receive a flash loan.
+     * @param initiator The initiator of the loan.
+     * @param token The loan currency.
+     * @param amount The amount of tokens lent.
+     * @param fee The additional amount of tokens to repay.
+     * @param data Arbitrary data structure, intended to contain user-defined parameters.
+     * @return The keccak256 hash of "ERC3156FlashBorrower.onFlashLoan"
+     */
+    function onFlashLoan(
+        address initiator,
+        address token,
+        uint256 amount,
+        uint256 fee,
+        bytes calldata data
+    ) external returns (bytes32);
+}

contracts/interfaces/IERC3156FlashLender.sol

@@ -0,0 +1,42 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "./IERC3156FlashBorrower.sol";
+
+/**
+ * @dev Interface of the ERC3156 FlashLender, as defined in
+ * https://eips.ethereum.org/EIPS/eip-3156[ERC-3156].
+ *
+ * _Available since v4.1._
+ */
+interface IERC3156FlashLender {
+    /**
+     * @dev The amount of currency available to be lended.
+     * @param token The loan currency.
+     * @return The amount of `token` that can be borrowed.
+     */
+    function maxFlashLoan(address token) external view returns (uint256);
+
+    /**
+     * @dev The fee to be charged for a given loan.
+     * @param token The loan currency.
+     * @param amount The amount of tokens lent.
+     * @return The amount of `token` to be charged for the loan, on top of the returned principal.
+     */
+    function flashFee(address token, uint256 amount) external view returns (uint256);
+
+    /**
+     * @dev Initiate a flash loan.
+     * @param receiver The receiver of the tokens in the loan, and the receiver of the callback.
+     * @param token The loan currency.
+     * @param amount The amount of tokens lent.
+     * @param data Arbitrary data structure, intended to contain user-defined parameters.
+     */
+    function flashLoan(
+        IERC3156FlashBorrower receiver,
+        address token,
+        uint256 amount,
+        bytes calldata data
+    ) external returns (bool);
+}

contracts/interfaces/IERC721.sol

@@ -0,0 +1,5 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "../token/ERC721/IERC721.sol";

contracts/interfaces/IERC721Enumerable.sol

@@ -0,0 +1,5 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "../token/ERC721/extensions/IERC721Enumerable.sol";

contracts/interfaces/IERC721Metadata.sol

@@ -0,0 +1,5 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "../token/ERC721/extensions/IERC721Metadata.sol";

contracts/interfaces/IERC721Receiver.sol

@@ -0,0 +1,5 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "../token/ERC721/IERC721Receiver.sol";

contracts/interfaces/IERC777.sol

@@ -0,0 +1,5 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "../token/ERC777/IERC777.sol";

contracts/interfaces/IERC777Recipient.sol

@@ -0,0 +1,5 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "../token/ERC777/IERC777Recipient.sol";

contracts/interfaces/IERC777Sender.sol

@@ -0,0 +1,5 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "../token/ERC777/IERC777Sender.sol";

contracts/interfaces/README.adoc

@@ -0,0 +1,50 @@
+= Interfaces
+
+[.readme-notice]
+NOTE: This document is better viewed at https://docs.openzeppelin.com/contracts/api/interfaces
+
+== List of standardized interfaces
+These interfaces are available as `.sol` files, and also as compiler `.json` ABI files (through the npm package). These
+are usefull to interract with third party contracts that implement them.
+
+- {IERC20}
+- {IERC20Metadata}
+- {IERC165}
+- {IERC721}
+- {IERC721Receiver}
+- {IERC721Enumerable}
+- {IERC721Metadata}
+- {IERC777}
+- {IERC777Recipient}
+- {IERC777Sender}
+- {IERC1155}
+- {IERC1155Receiver}
+- {IERC1155MetadataURI}
+- {IERC1271}
+- {IERC1363}
+- {IERC1820Implementer}
+- {IERC1820Registry}
+- {IERC2612}
+- {IERC2981}
+- {IERC3156FlashLender}
+- {IERC3156FlashBorrower}
+
+== Detailed ABI
+
+{{IERC1271}}
+
+{{IERC1363}}
+
+{{IERC1363Receiver}}
+
+{{IERC1820Implementer}}
+
+{{IERC1820Registry}}
+
+{{IERC2612}}
+
+{{IERC2981}}
+
+{{IERC3156FlashLender}}
+
+{{IERC3156FlashBorrower}}

contracts/interfaces/draft-IERC2612.sol

@@ -0,0 +1,7 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "../token/ERC20/extensions/draft-IERC20Permit.sol";
+
+interface IERC2612 is IERC20Permit {}

contracts/introspection/README.adoc

@@ -1,28 +0,0 @@
-= Introspection
-
-This set of interfaces and contracts deal with https://en.wikipedia.org/wiki/Type_introspection[type introspection] of contracts, that is, examining which functions can be called on them. This is usually referred to as a contract's _interface_.
-
-Ethereum contracts have no native concept of an interface, so applications must usually simply trust they are not making an incorrect call. For trusted setups this is a non-issue, but often unknown and untrusted third-party addresses need to be interacted with. There may even not be any direct calls to them! (e.g. `ERC20` tokens may be sent to a contract that lacks a way to transfer them out of it, locking them forever). In these cases, a contract _declaring_ its interface can be very helpful in preventing errors.
-
-There are two main ways to approach this.
-
-* Locally, where a contract implements `IERC165` and declares an interface, and a second one queries it directly via `ERC165Checker`.
-* Globally, where a global and unique registry (`IERC1820Registry`) is used to register implementers of a certain interface (`IERC1820Implementer`). It is then the registry that is queried, which allows for more complex setups, like contracts implementing interfaces for externally-owned accounts.
-
-Note that, in all cases, accounts simply _declare_ their interfaces, but they are not required to actually implement them. This mechanism can therefore be used to both prevent errors and allow for complex interactions (see `ERC777`), but it must not be relied on for security.
-
-== Local
-
-{{IERC165}}
-
-{{ERC165}}
-
-{{ERC165Checker}}
-
-== Global
-
-{{IERC1820Registry}}
-
-{{IERC1820Implementer}}
-
-{{ERC1820Implementer}}

contracts/math/README.adoc

@@ -1,11 +0,0 @@
-= Math
-
-These are math-related utilities.
-
-== Libraries
-
-{{SafeMath}}
-
-{{SignedSafeMath}}
-
-{{Math}}

contracts/math/SafeMath.sol

@@ -1,152 +0,0 @@
-// SPDX-License-Identifier: MIT
-
-pragma solidity ^0.6.0;
-
-/**
- * @dev Wrappers over Solidity's arithmetic operations with added overflow
- * checks.
- *
- * Arithmetic operations in Solidity wrap on overflow. This can easily result
- * in bugs, because programmers usually assume that an overflow raises an
- * error, which is the standard behavior in high level programming languages.
- * `SafeMath` restores this intuition by reverting the transaction when an
- * operation overflows.
- *
- * Using this library instead of the unchecked operations eliminates an entire
- * class of bugs, so it's recommended to use it always.
- */
-library SafeMath {
-    /**
-     * @dev Returns the addition of two unsigned integers, reverting on
-     * overflow.
-     *
-     * Counterpart to Solidity's `+` operator.
-     *
-     * Requirements:
-     * - Addition cannot overflow.
-     */
-    function add(uint256 a, uint256 b) internal pure returns (uint256) {
-        uint256 c = a + b;
-        require(c >= a, "SafeMath: addition overflow");
-
-        return c;
-    }
-
-    /**
-     * @dev Returns the subtraction of two unsigned integers, reverting on
-     * overflow (when the result is negative).
-     *
-     * Counterpart to Solidity's `-` operator.
-     *
-     * Requirements:
-     * - Subtraction cannot overflow.
-     */
-    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
-        return sub(a, b, "SafeMath: subtraction overflow");
-    }
-
-    /**
-     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
-     * overflow (when the result is negative).
-     *
-     * Counterpart to Solidity's `-` operator.
-     *
-     * Requirements:
-     * - Subtraction cannot overflow.
-     */
-    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
-        require(b <= a, errorMessage);
-        uint256 c = a - b;
-
-        return c;
-    }
-
-    /**
-     * @dev Returns the multiplication of two unsigned integers, reverting on
-     * overflow.
-     *
-     * Counterpart to Solidity's `*` operator.
-     *
-     * Requirements:
-     * - Multiplication cannot 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-contracts/pull/522
-        if (a == 0) {
-            return 0;
-        }
-
-        uint256 c = a * b;
-        require(c / a == b, "SafeMath: multiplication overflow");
-
-        return c;
-    }
-
-    /**
-     * @dev Returns the integer division of two unsigned integers. Reverts on
-     * division by zero. The result is rounded towards zero.
-     *
-     * Counterpart to Solidity's `/` operator. Note: this function uses a
-     * `revert` opcode (which leaves remaining gas untouched) while Solidity
-     * uses an invalid opcode to revert (consuming all remaining gas).
-     *
-     * Requirements:
-     * - The divisor cannot be zero.
-     */
-    function div(uint256 a, uint256 b) internal pure returns (uint256) {
-        return div(a, b, "SafeMath: division by zero");
-    }
-
-    /**
-     * @dev Returns the integer division of two unsigned integers. Reverts with custom message on
-     * division by zero. The result is rounded towards zero.
-     *
-     * Counterpart to Solidity's `/` operator. Note: this function uses a
-     * `revert` opcode (which leaves remaining gas untouched) while Solidity
-     * uses an invalid opcode to revert (consuming all remaining gas).
-     *
-     * Requirements:
-     * - The divisor cannot be zero.
-     */
-    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
-        // Solidity only automatically asserts when dividing by 0
-        require(b > 0, errorMessage);
-        uint256 c = a / b;
-        // assert(a == b * c + a % b); // There is no case in which this doesn't hold
-
-        return c;
-    }
-
-    /**
-     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
-     * Reverts when dividing by zero.
-     *
-     * Counterpart to Solidity's `%` operator. This function uses a `revert`
-     * opcode (which leaves remaining gas untouched) while Solidity uses an
-     * invalid opcode to revert (consuming all remaining gas).
-     *
-     * Requirements:
-     * - The divisor cannot be zero.
-     */
-    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
-        return mod(a, b, "SafeMath: modulo by zero");
-    }
-
-    /**
-     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
-     * Reverts with custom message when dividing by zero.
-     *
-     * Counterpart to Solidity's `%` operator. This function uses a `revert`
-     * opcode (which leaves remaining gas untouched) while Solidity uses an
-     * invalid opcode to revert (consuming all remaining gas).
-     *
-     * Requirements:
-     * - The divisor cannot be zero.
-     */
-    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
-        require(b != 0, errorMessage);
-        return a % b;
-    }
-}

contracts/math/SignedSafeMath.sol

@@ -1,62 +0,0 @@
-// SPDX-License-Identifier: MIT
-
-pragma solidity ^0.6.0;
-
-/**
- * @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-contracts/pull/522
-        if (a == 0) {
-            return 0;
-        }
-
-        require(!(a == -1 && b == _INT256_MIN), "SignedSafeMath: multiplication overflow");
-
-        int256 c = a * b;
-        require(c / a == b, "SignedSafeMath: multiplication overflow");
-
-        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, "SignedSafeMath: division by zero");
-        require(!(b == -1 && a == _INT256_MIN), "SignedSafeMath: division 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), "SignedSafeMath: subtraction overflow");
-
-        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), "SignedSafeMath: addition overflow");
-
-        return c;
-    }
-}

contracts/metatx/ERC2771Context.sol

@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "../utils/Context.sol";
+
+/**
+ * @dev Context variant with ERC2771 support.
+ */
+abstract contract ERC2771Context is Context {
+    address private _trustedForwarder;
+
+    constructor(address trustedForwarder) {
+        _trustedForwarder = trustedForwarder;
+    }
+
+    function isTrustedForwarder(address forwarder) public view virtual returns (bool) {
+        return forwarder == _trustedForwarder;
+    }
+
+    function _msgSender() internal view virtual override returns (address sender) {
+        if (isTrustedForwarder(msg.sender)) {
+            // The assembly code is more direct than the Solidity version using `abi.decode`.
+            assembly {
+                sender := shr(96, calldataload(sub(calldatasize(), 20)))
+            }
+        } else {
+            return super._msgSender();
+        }
+    }
+
+    function _msgData() internal view virtual override returns (bytes calldata) {
+        if (isTrustedForwarder(msg.sender)) {
+            return msg.data[:msg.data.length - 20];
+        } else {
+            return super._msgData();
+        }
+    }
+}

contracts/metatx/MinimalForwarder.sol

@@ -0,0 +1,58 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "../utils/cryptography/ECDSA.sol";
+import "../utils/cryptography/draft-EIP712.sol";
+
+/**
+ * @dev Simple minimal forwarder to be used together with an ERC2771 compatible contract. See {ERC2771Context}.
+ */
+contract MinimalForwarder is EIP712 {
+    using ECDSA for bytes32;
+
+    struct ForwardRequest {
+        address from;
+        address to;
+        uint256 value;
+        uint256 gas;
+        uint256 nonce;
+        bytes data;
+    }
+
+    bytes32 private constant _TYPEHASH =
+        keccak256("ForwardRequest(address from,address to,uint256 value,uint256 gas,uint256 nonce,bytes data)");
+
+    mapping(address => uint256) private _nonces;
+
+    constructor() EIP712("MinimalForwarder", "0.0.1") {}
+
+    function getNonce(address from) public view returns (uint256) {
+        return _nonces[from];
+    }
+
+    function verify(ForwardRequest calldata req, bytes calldata signature) public view returns (bool) {
+        address signer = _hashTypedDataV4(
+            keccak256(abi.encode(_TYPEHASH, req.from, req.to, req.value, req.gas, req.nonce, keccak256(req.data)))
+        ).recover(signature);
+        return _nonces[req.from] == req.nonce && signer == req.from;
+    }
+
+    function execute(ForwardRequest calldata req, bytes calldata signature)
+        public
+        payable
+        returns (bool, bytes memory)
+    {
+        require(verify(req, signature), "MinimalForwarder: signature does not match request");
+        _nonces[req.from] = req.nonce + 1;
+
+        (bool success, bytes memory returndata) = req.to.call{gas: req.gas, value: req.value}(
+            abi.encodePacked(req.data, req.from)
+        );
+        // Validate that the relayer has sent enough gas for the call.
+        // See https://ronan.eth.link/blog/ethereum-gas-dangers/
+        assert(gasleft() > req.gas / 63);
+
+        return (success, returndata);
+    }
+}

contracts/metatx/README.adoc

@@ -0,0 +1,12 @@
+= Meta Transactions
+
+[.readme-notice]
+NOTE: This document is better viewed at https://docs.openzeppelin.com/contracts/api/metatx
+
+== Core
+
+{{ERC2771Context}}
+
+== Utils
+
+{{MinimalForwarder}}

contracts/mocks/AccessControlEnumerableMock.sol

@@ -0,0 +1,17 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "../access/AccessControlEnumerable.sol";
+
+contract AccessControlEnumerableMock is AccessControlEnumerable {
+    constructor() {
+        _setupRole(DEFAULT_ADMIN_ROLE, _msgSender());
+    }
+
+    function setRoleAdmin(bytes32 roleId, bytes32 adminRoleId) public {
+        _setRoleAdmin(roleId, adminRoleId);
+    }
+
+    function senderProtected(bytes32 roleId) public onlyRole(roleId) {}
+}

contracts/mocks/AccessControlMock.sol

@@ -1,15 +1,17 @@
 // SPDX-License-Identifier: MIT
 
-pragma solidity ^0.6.0;
+pragma solidity ^0.8.0;
 
 import "../access/AccessControl.sol";
 
 contract AccessControlMock is AccessControl {
-    constructor() public {
+    constructor() {
         _setupRole(DEFAULT_ADMIN_ROLE, _msgSender());
     }
 
     function setRoleAdmin(bytes32 roleId, bytes32 adminRoleId) public {
         _setRoleAdmin(roleId, adminRoleId);
     }
+
+    function senderProtected(bytes32 roleId) public onlyRole(roleId) {}
 }

contracts/mocks/AddressImpl.sol

@@ -1,10 +1,14 @@
 // SPDX-License-Identifier: MIT
 
-pragma solidity ^0.6.0;
+pragma solidity ^0.8.0;
 
 import "../utils/Address.sol";
 
 contract AddressImpl {
+    string public sharedAnswer;
+
+    event CallReturnValue(string data);
+
     function isContract(address account) external view returns (bool) {
         return Address.isContract(account);
     }
@@ -13,6 +17,30 @@ contract AddressImpl {
         Address.sendValue(receiver, amount);
     }
 
+    function functionCall(address target, bytes calldata data) external {
+        bytes memory returnData = Address.functionCall(target, data);
+        emit CallReturnValue(abi.decode(returnData, (string)));
+    }
+
+    function functionCallWithValue(
+        address target,
+        bytes calldata data,
+        uint256 value
+    ) external payable {
+        bytes memory returnData = Address.functionCallWithValue(target, data, value);
+        emit CallReturnValue(abi.decode(returnData, (string)));
+    }
+
+    function functionStaticCall(address target, bytes calldata data) external {
+        bytes memory returnData = Address.functionStaticCall(target, data);
+        emit CallReturnValue(abi.decode(returnData, (string)));
+    }
+
+    function functionDelegateCall(address target, bytes calldata data) external {
+        bytes memory returnData = Address.functionDelegateCall(target, data);
+        emit CallReturnValue(abi.decode(returnData, (string)));
+    }
+
     // sendValue's tests require the contract to hold Ether
-    receive () external payable { }
+    receive() external payable {}
 }

contracts/mocks/ArraysImpl.sol

@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: MIT
 
-pragma solidity ^0.6.0;
+pragma solidity ^0.8.0;
 
 import "../utils/Arrays.sol";
 
@@ -9,7 +9,7 @@ contract ArraysImpl {
 
     uint256[] private _array;
 
-    constructor (uint256[] memory array) public {
+    constructor(uint256[] memory array) {
         _array = array;
     }
 

contracts/mocks/BadBeacon.sol

@@ -0,0 +1,11 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+contract BadBeaconNoImpl {}
+
+contract BadBeaconNotContract {
+    function implementation() external pure returns (address) {
+        return address(0x1);
+    }
+}

contracts/mocks/BitmapMock.sol

@@ -0,0 +1,27 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "../utils/structs/BitMaps.sol";
+
+contract BitMapMock {
+    using BitMaps for BitMaps.BitMap;
+
+    BitMaps.BitMap private _bitmap;
+
+    function get(uint256 index) public view returns (bool) {
+        return _bitmap.get(index);
+    }
+
+    function setTo(uint256 index, bool value) public {
+        _bitmap.setTo(index, value);
+    }
+
+    function set(uint256 index) public {
+        _bitmap.set(index);
+    }
+
+    function unset(uint256 index) public {
+        _bitmap.unset(index);
+    }
+}

contracts/mocks/CallReceiverMock.sol

@@ -0,0 +1,50 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+contract CallReceiverMock {
+    string public sharedAnswer;
+
+    event MockFunctionCalled();
+
+    uint256[] private _array;
+
+    function mockFunction() public payable returns (string memory) {
+        emit MockFunctionCalled();
+
+        return "0x1234";
+    }
+
+    function mockFunctionNonPayable() public returns (string memory) {
+        emit MockFunctionCalled();
+
+        return "0x1234";
+    }
+
+    function mockStaticFunction() public pure returns (string memory) {
+        return "0x1234";
+    }
+
+    function mockFunctionRevertsNoReason() public payable {
+        revert();
+    }
+
+    function mockFunctionRevertsReason() public payable {
+        revert("CallReceiverMock: reverting");
+    }
+
+    function mockFunctionThrows() public payable {
+        assert(false);
+    }
+
+    function mockFunctionOutOfGas() public payable {
+        for (uint256 i = 0; ; ++i) {
+            _array.push(i);
+        }
+    }
+
+    function mockFunctionWritesStorage() public returns (string memory) {
+        sharedAnswer = "42";
+        return "0x1234";
+    }
+}

contracts/mocks/ClashingImplementation.sol

@@ -0,0 +1,18 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+/**
+ * @dev Implementation contract with an admin() function made to clash with
+ * @dev TransparentUpgradeableProxy's to test correct functioning of the
+ * @dev Transparent Proxy feature.
+ */
+contract ClashingImplementation {
+    function admin() external pure returns (address) {
+        return 0x0000000000000000000000000000000011111142;
+    }
+
+    function delegatedFunction() external pure returns (bool) {
+        return true;
+    }
+}

contracts/mocks/ClonesMock.sol

@@ -0,0 +1,36 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "../proxy/Clones.sol";
+import "../utils/Address.sol";
+
+contract ClonesMock {
+    using Address for address;
+    using Clones for address;
+
+    event NewInstance(address instance);
+
+    function clone(address implementation, bytes calldata initdata) public payable {
+        _initAndEmit(implementation.clone(), initdata);
+    }
+
+    function cloneDeterministic(
+        address implementation,
+        bytes32 salt,
+        bytes calldata initdata
+    ) public payable {
+        _initAndEmit(implementation.cloneDeterministic(salt), initdata);
+    }
+
+    function predictDeterministicAddress(address implementation, bytes32 salt) public view returns (address predicted) {
+        return implementation.predictDeterministicAddress(salt);
+    }
+
+    function _initAndEmit(address instance, bytes memory initdata) private {
+        if (initdata.length > 0) {
+            instance.functionCallWithValue(initdata, msg.value);
+        }
+        emit NewInstance(instance);
+    }
+}

contracts/mocks/ConditionalEscrowMock.sol

@@ -1,8 +1,8 @@
 // SPDX-License-Identifier: MIT
 
-pragma solidity ^0.6.0;
+pragma solidity ^0.8.0;
 
-import "../payment/escrow/ConditionalEscrow.sol";
+import "../utils/escrow/ConditionalEscrow.sol";
 
 // mock class using ConditionalEscrow
 contract ConditionalEscrowMock is ConditionalEscrow {

contracts/mocks/ContextMock.sol

@@ -1,8 +1,8 @@
 // SPDX-License-Identifier: MIT
 
-pragma solidity ^0.6.0;
+pragma solidity ^0.8.0;
 
-import "../GSN/Context.sol";
+import "../utils/Context.sol";
 
 contract ContextMock is Context {
     event Sender(address sender);
@@ -23,7 +23,11 @@ contract ContextMockCaller {
         context.msgSender();
     }
 
-    function callData(ContextMock context, uint256 integerValue, string memory stringValue) public {
+    function callData(
+        ContextMock context,
+        uint256 integerValue,
+        string memory stringValue
+    ) public {
         context.msgData(integerValue, stringValue);
     }
 }

contracts/mocks/CountersImpl.sol

@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: MIT
 
-pragma solidity ^0.6.0;
+pragma solidity ^0.8.0;
 
 import "../utils/Counters.sol";
 
@@ -20,4 +20,8 @@ contract CountersImpl {
     function decrement() public {
         _counter.decrement();
     }
+
+    function reset() public {
+        _counter.reset();
+    }
 }