2.3.0-rc.0

* Error handling in ERC20 and ERC721

* Added message string for require.

* Fixed solhint errors.

* Updated PR as per issue #1709

* changes as per #1709 and openzeppelin forum.

* Changes in require statement

* Changes in require statement

* build pipeline fix

* Changes as per @nventuro's comment.

* Update revert reason strings.

* Fianal update of revert reason strings.

* WIP: Updating reason strings in test cases

* WIP: Added changes to ERC20 and ERC721

* Fixes linting errors in *.tes.js files

* Achieved 100% code coverage

* Updated the test cases with shouldFail.reverting.withMessage()

* Fix package-lock.

* address review comments

* fix linter issues

* fix remaining revert reasons

.github/ISSUE_TEMPLATE/bug_report.md

@@ -6,7 +6,7 @@ about: Report a bug in OpenZeppelin
 
 <!-- Briefly describe the issue you're experiencing. Tell us what you were trying to do and what happened instead. -->
 
-<!-- Remember, this is not a place to ask for help debugging code. For that, we welcome you in the OpenZeppelin Slack channel: https://slack.openzeppelin.org/. -->
+<!-- Remember, this is not a place to ask for help debugging code. For that, we welcome you in the Zeppelin Forum: https://forum.zeppelin.solutions/. -->
 
 **💻 Environment**
 

.github/stale.yml

@@ -0,0 +1,66 @@
+# 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
+
+# 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

.gitignore

@@ -40,3 +40,7 @@ build/
 
 # IntelliJ IDE
 .idea
+
+# docsite artifacts
+docsite-build
+docs/api

.travis.yml

@@ -35,15 +35,6 @@ jobs:
       script: npm run test
       env: SOLC_NIGHTLY=true
 
-    - stage: update docs
-      if: tag =~ ^v[0-9]+\.[0-9]+\.[0-9]+$
-      addons:
-        apt:
-          packages:
-            - curl
-      script:
-        - ./scripts/ci/trigger_docs_update "${TRAVIS_TAG}"
-
 notifications:
   slack:
     rooms:

CHANGELOG.md

@@ -1,10 +1,23 @@
 # Changelog
 
+## 2.3.0 (unreleased)
+
+### New features:
+ * `ERC1820`: added support for interacting with the [ERC1820](https://eips.ethereum.org/EIPS/eip-1820) registry contract (`IERC1820Registry`), as well as base contracts that can be registered as implementers there. ([#1677](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1677))
+ * `ERC777`: initial support for the [ERC777 token](https://eips.ethereum.org/EIPS/eip-777), which has multiple improvements over `ERC20` such as built-in burning, a more  straightforward permission system, and optional sender and receiver hooks on transfer (mandatory for contracts!). ([#1684](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1684))
+ * All contracts now have revert reason strings, which give insight into error conditions, and help debug failing transactions. ([#1704](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1704))
+
+### Improvements:
+ * Upgraded the minimum compiler version to v0.5.7: this prevents users from encountering compiler bugs that were fixed in this version. ([#1724](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1724))
+
+### Bugfixes:
+ * `PostDeliveryCrowdsale`: some validations where skipped when paired with other crowdsale flavors, such as `AllowanceCrowdsale`, or `MintableCrowdsale` and `ERC20Capped`, which could cause buyers to not be able to claim their purchased tokens. ([#1721](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1721))
+
 ## 2.2.0 (2019-03-14)
 
 ### New features:
  * `ERC20Snapshot`: create snapshots on demand of the token balances and total supply, to later retrieve and e.g. calculate dividends at a past time. ([#1617](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1617))
- * `SafeERC20`: `ERC20` contracts with no return value (i.e. that revert on failure) are now supported. ([#1655](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/))
+ * `SafeERC20`: `ERC20` contracts with no return value (i.e. that revert on failure) are now supported. ([#1655](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1655))
  * `ERC20`: added internal `_approve(address owner, address spender, uint256 value)`, allowing derived contracts to set the allowance of arbitrary accounts. ([#1609](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1609))
  * `ERC20Metadata`: added internal `_setTokenURI(string memory tokenURI)`. ([#1618](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1618))
  * `TimedCrowdsale`: added internal `_extendTime(uint256 newClosingTime)` as well as `TimedCrowdsaleExtended(uint256 prevClosingTime, uint256 newClosingTime)` event allowing to extend the crowdsale, as long as it hasn't already closed.
@@ -13,14 +26,14 @@
  * Upgraded the minimum compiler version to v0.5.2: this removes many Solidity warnings that were false positives. ([#1606](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1606))
  * `ECDSA`: `recover` no longer accepts malleable signatures (those using upper-range values for `s`, or 0/1 for `v`). ([#1622](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1622))
  * `ERC721`'s transfers are now more gas efficient due to removal of unnecessary `SafeMath` calls. ([#1610](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1610))
- * `Counter`'s API has been improved, and is now used by `ERC721` (though it is still in `drafts`). ([#1610](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1610))
  * Fixed variable shadowing issues. ([#1606](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1606))
 
 ### Bugfixes:
  * (minor) `SafeERC20`: `safeApprove` wasn't properly checking for a zero allowance when attempting to set a non-zero allowance. ([#1647](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1647))
 
-### Breaking changes:
- * `TokenMetadata` (in drafts) has been renamed to `ERC20Metadata`. ([#1618](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1618))
+### Breaking changes in drafts:
+ * `TokenMetadata` has been renamed to `ERC20Metadata`. ([#1618](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1618))
+ * The library `Counter` has been renamed to `Counters` and its API has been improved. See an example in `ERC721`, lines [17](https://github.com/OpenZeppelin/openzeppelin-solidity/blob/3cb4a00fce1da76196ac0ac3a0ae9702b99642b5/contracts/token/ERC721/ERC721.sol#L17) and [204](https://github.com/OpenZeppelin/openzeppelin-solidity/blob/3cb4a00fce1da76196ac0ac3a0ae9702b99642b5/contracts/token/ERC721/ERC721.sol#L204). ([#1610](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1610))
 
 ## 2.1.3 (2019-02-26)
  * Backported `SafeERC20.safeApprove` bugfix. ([#1647](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1647))

DOCUMENTATION.md

@@ -0,0 +1,19 @@
+We're building an improved documentation website. It's still in development and
+contributions will be really appreciated.
+
+All of the content for the site is in this repository. The guides are in the
+[docs](/docs) directory, and the API Reference is extracted from comments in
+the source code. If you want to help improve the content, this is the
+repository you should be contributing to.
+
+[`solidity-docgen`](https://github.com/OpenZeppelin/solidity-docgen/tree/next) is the
+program that extracts the API Reference from source code.
+
+The [`openzeppelin-docsite`](https://github.com/OpenZeppelin/openzeppelin-docsite/tree/next)
+repository hosts the configuration for Docusaurus, the static site generator
+that we use.
+
+To run the docsite locally you should run `npm run docsite start` on this
+repository. This will live reload as the guides are edited, but not with
+changes to the source code comments, for that you need to restart the server.
+This should be improved eventually (contributions welcome!).

LICENSE

@@ -1,6 +1,6 @@
 The MIT License (MIT)
 
-Copyright (c) 2016 Smart Contract Solutions, Inc.
+Copyright (c) 2016-2019 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

@@ -12,6 +12,8 @@
 npm install openzeppelin-solidity
 ```
 
+OpenZeppelin features a stable API, which means your contracts won't break unexpectedly when upgrading to a newer minor version. You can read ṫhe details in our [API Stability](https://forum.zeppelin.solutions/t/api-stability/138) document.
+
 ## Usage
 
 To write your custom contracts, import ours and extend them through inheritance.
@@ -28,9 +30,9 @@ contract MyNFT is ERC721Full, ERC721Mintable {
 }
 ```
 
-> You need an ethereum development framework for the above import statements to work! Check out these guides for [Truffle] or [Embark].
+> You need an ethereum development framework for the above import statements to work! Check out these guides for [Truffle], [Embark] or [Buidler].
 
-On our site you will find a few [guides] to learn about the different parts of OpenZeppelin, as well as [documentation for the API][API docs]. Keep in mind that the API docs are work in progress, and don’t hesitate to ask questions in [our Slack][Slack].
+On our site you will find a few [guides] to learn about the different parts of OpenZeppelin, as well as [documentation for the API][API docs]. Keep in mind that the API docs are work in progress, and don’t hesitate to ask questions in [our forum][forum].
 
 ## Security
 
@@ -53,8 +55,9 @@ OpenZeppelin is released under the [MIT License](LICENSE).
 
 [API docs]: https://openzeppelin.org/api/docs/token_ERC721_ERC721BasicToken.html
 [guides]: https://openzeppelin.org/api/docs/get-started.html
-[Slack]: https://slack.openzeppelin.org
+[forum]: https://forum.zeppelin.solutions
 [Zeppelin]: https://zeppelin.solutions
 [contribution guide]: CONTRIBUTING.md
 [Truffle]: https://truffleframework.com/docs/truffle/quickstart
 [Embark]: https://embark.status.im/docs/quick_start.html
+[Buidler]: https://buidler.dev/guides/#getting-started

RELEASING.md

@@ -40,7 +40,7 @@ Once the CI run for the new tag is green, publish on npm under the `next` tag. Y
 npm publish --tag next
 ```
 
-Publish the release notes on GitHub and ask our community manager to announce the release candidate on at least Slack and Twitter.
+Publish the release notes on GitHub and the forum, and ask our community manager to announce the release candidate on at least Twitter.
 
 ## Creating the final release
 

contracts/access/README.md

@@ -0,0 +1,7 @@
+---
+sections:
+  - title: Library
+    contracts:
+      - Roles
+  - subdirectory: roles
+---

contracts/access/Roles.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 /**
  * @title Roles
@@ -10,31 +10,27 @@ library Roles {
     }
 
     /**
-     * @dev give an account access to this role
+     * @dev Give an account access to this role.
      */
     function add(Role storage role, address account) internal {
-        require(account != address(0));
-        require(!has(role, account));
-
+        require(!has(role, account), "Roles: account already has role");
         role.bearer[account] = true;
     }
 
     /**
-     * @dev remove an account's access to this role
+     * @dev Remove an account's access to this role.
      */
     function remove(Role storage role, address account) internal {
-        require(account != address(0));
-        require(has(role, account));
-
+        require(has(role, account), "Roles: account does not have role");
         role.bearer[account] = false;
     }
 
     /**
-     * @dev check if an account has this role
+     * @dev Check if an account has this role.
      * @return bool
      */
     function has(Role storage role, address account) internal view returns (bool) {
-        require(account != address(0));
+        require(account != address(0), "Roles: account is the zero address");
         return role.bearer[account];
     }
 }

contracts/access/roles/CapperRole.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../Roles.sol";
 
@@ -15,7 +15,7 @@ contract CapperRole {
     }
 
     modifier onlyCapper() {
-        require(isCapper(msg.sender));
+        require(isCapper(msg.sender), "CapperRole: caller does not have the Capper role");
         _;
     }
 

contracts/access/roles/MinterRole.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../Roles.sol";
 
@@ -15,7 +15,7 @@ contract MinterRole {
     }
 
     modifier onlyMinter() {
-        require(isMinter(msg.sender));
+        require(isMinter(msg.sender), "MinterRole: caller does not have the Minter role");
         _;
     }
 

contracts/access/roles/PauserRole.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../Roles.sol";
 
@@ -15,7 +15,7 @@ contract PauserRole {
     }
 
     modifier onlyPauser() {
-        require(isPauser(msg.sender));
+        require(isPauser(msg.sender), "PauserRole: caller does not have the Pauser role");
         _;
     }
 

contracts/access/roles/SignerRole.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../Roles.sol";
 
@@ -15,7 +15,7 @@ contract SignerRole {
     }
 
     modifier onlySigner() {
-        require(isSigner(msg.sender));
+        require(isSigner(msg.sender), "SignerRole: caller does not have the Signer role");
         _;
     }
 

contracts/access/roles/WhitelistAdminRole.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../Roles.sol";
 
@@ -19,7 +19,7 @@ contract WhitelistAdminRole {
     }
 
     modifier onlyWhitelistAdmin() {
-        require(isWhitelistAdmin(msg.sender));
+        require(isWhitelistAdmin(msg.sender), "WhitelistAdminRole: caller does not have the WhitelistAdmin role");
         _;
     }
 

contracts/access/roles/WhitelistedRole.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../Roles.sol";
 import "./WhitelistAdminRole.sol";
@@ -18,7 +18,7 @@ contract WhitelistedRole is WhitelistAdminRole {
     Roles.Role private _whitelisteds;
 
     modifier onlyWhitelisted() {
-        require(isWhitelisted(msg.sender));
+        require(isWhitelisted(msg.sender), "WhitelistedRole: caller does not have the Whitelisted role");
         _;
     }
 

contracts/crowdsale/Crowdsale.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../token/ERC20/IERC20.sol";
 import "../math/SafeMath.sol";
@@ -54,9 +54,9 @@ contract Crowdsale is ReentrancyGuard {
      * @param token Address of the token being sold
      */
     constructor (uint256 rate, address payable wallet, IERC20 token) public {
-        require(rate > 0);
-        require(wallet != address(0));
-        require(address(token) != address(0));
+        require(rate > 0, "Crowdsale: rate is 0");
+        require(wallet != address(0), "Crowdsale: wallet is the zero address");
+        require(address(token) != address(0), "Crowdsale: token is the zero address");
 
         _rate = rate;
         _wallet = wallet;
@@ -136,8 +136,8 @@ contract Crowdsale is ReentrancyGuard {
      * @param weiAmount Value in wei involved in the purchase
      */
     function _preValidatePurchase(address beneficiary, uint256 weiAmount) internal view {
-        require(beneficiary != address(0));
-        require(weiAmount != 0);
+        require(beneficiary != address(0), "Crowdsale: beneficiary is the zero address");
+        require(weiAmount != 0, "Crowdsale: weiAmount is 0");
     }
 
     /**

contracts/crowdsale/README.md

@@ -0,0 +1,11 @@
+---
+title: Crowdsales
+sections:
+  - title: Core
+    contracts:
+      - Crowdsale
+  - subdirectory: emission
+  - subdirectory: price
+  - subdirectory: validation
+  - subdirectory: distribution
+---

contracts/crowdsale/distribution/FinalizableCrowdsale.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../../math/SafeMath.sol";
 import "../validation/TimedCrowdsale.sol";
@@ -31,8 +31,8 @@ contract FinalizableCrowdsale is TimedCrowdsale {
      * work. Calls the contract's finalization function.
      */
     function finalize() public {
-        require(!_finalized);
-        require(hasClosed());
+        require(!_finalized, "FinalizableCrowdsale: already finalized");
+        require(hasClosed(), "FinalizableCrowdsale: not closed");
 
         _finalized = true;
 

contracts/crowdsale/distribution/PostDeliveryCrowdsale.sol

@@ -1,7 +1,9 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../validation/TimedCrowdsale.sol";
 import "../../math/SafeMath.sol";
+import "../../ownership/Secondary.sol";
+import "../../token/ERC20/IERC20.sol";
 
 /**
  * @title PostDeliveryCrowdsale
@@ -11,17 +13,23 @@ contract PostDeliveryCrowdsale is TimedCrowdsale {
     using SafeMath for uint256;
 
     mapping(address => uint256) private _balances;
+    __unstable__TokenVault private _vault;
+
+    constructor() public {
+        _vault = new __unstable__TokenVault();
+    }
 
     /**
      * @dev Withdraw tokens only after crowdsale ends.
      * @param beneficiary Whose tokens will be withdrawn.
      */
     function withdrawTokens(address beneficiary) public {
-        require(hasClosed());
+        require(hasClosed(), "PostDeliveryCrowdsale: not closed");
         uint256 amount = _balances[beneficiary];
-        require(amount > 0);
+        require(amount > 0, "PostDeliveryCrowdsale: beneficiary is not due any tokens");
+
         _balances[beneficiary] = 0;
-        _deliverTokens(beneficiary, amount);
+        _vault.transfer(token(), beneficiary, amount);
     }
 
     /**
@@ -32,12 +40,26 @@ contract PostDeliveryCrowdsale is TimedCrowdsale {
     }
 
     /**
-     * @dev Overrides parent by storing balances instead of issuing tokens right away.
+     * @dev Overrides parent by storing due balances, and delivering tokens to the vault instead of the end user. This
+     * ensures that the tokens will be available by the time they are withdrawn (which may not be the case if
+     * `_deliverTokens` was called later).
      * @param beneficiary Token purchaser
      * @param tokenAmount Amount of tokens purchased
      */
     function _processPurchase(address beneficiary, uint256 tokenAmount) internal {
         _balances[beneficiary] = _balances[beneficiary].add(tokenAmount);
+        _deliverTokens(address(_vault), tokenAmount);
+    }
+}
+
+/**
+ * @title __unstable__TokenVault
+ * @dev Similar to an Escrow for tokens, this contract allows its primary account to spend its tokens as it sees fit.
+ * This contract is an internal helper for PostDeliveryCrowdsale, and should not be used outside of this context.
+ */
+// solhint-disable-next-line contract-name-camelcase
+contract __unstable__TokenVault is Secondary {
+    function transfer(IERC20 token, address to, uint256 amount) public onlyPrimary {
+        token.transfer(to, amount);
     }
-
 }

contracts/crowdsale/distribution/RefundableCrowdsale.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../../math/SafeMath.sol";
 import "./FinalizableCrowdsale.sol";
@@ -28,7 +28,7 @@ contract RefundableCrowdsale is FinalizableCrowdsale {
      * @param goal Funding goal
      */
     constructor (uint256 goal) public {
-        require(goal > 0);
+        require(goal > 0, "RefundableCrowdsale: goal is 0");
         _escrow = new RefundEscrow(wallet());
         _goal = goal;
     }
@@ -41,12 +41,12 @@ contract RefundableCrowdsale is FinalizableCrowdsale {
     }
 
     /**
-     * @dev Investors can claim refunds here if crowdsale is unsuccessful
+     * @dev Investors can claim refunds here if crowdsale is unsuccessful.
      * @param refundee Whose refund will be claimed.
      */
     function claimRefund(address payable refundee) public {
-        require(finalized());
-        require(!goalReached());
+        require(finalized(), "RefundableCrowdsale: not finalized");
+        require(!goalReached(), "RefundableCrowdsale: goal reached");
 
         _escrow.withdraw(refundee);
     }
@@ -60,7 +60,7 @@ contract RefundableCrowdsale is FinalizableCrowdsale {
     }
 
     /**
-     * @dev escrow finalization task, called when finalize() is called
+     * @dev Escrow finalization task, called when finalize() is called.
      */
     function _finalization() internal {
         if (goalReached()) {

contracts/crowdsale/distribution/RefundablePostDeliveryCrowdsale.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "./RefundableCrowdsale.sol";
 import "./PostDeliveryCrowdsale.sol";
@@ -12,8 +12,8 @@ import "./PostDeliveryCrowdsale.sol";
  */
 contract RefundablePostDeliveryCrowdsale is RefundableCrowdsale, PostDeliveryCrowdsale {
     function withdrawTokens(address beneficiary) public {
-        require(finalized());
-        require(goalReached());
+        require(finalized(), "RefundablePostDeliveryCrowdsale: not finalized");
+        require(goalReached(), "RefundablePostDeliveryCrowdsale: goal not reached");
 
         super.withdrawTokens(beneficiary);
     }

contracts/crowdsale/emission/AllowanceCrowdsale.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../Crowdsale.sol";
 import "../../token/ERC20/IERC20.sol";
@@ -18,10 +18,10 @@ contract AllowanceCrowdsale is Crowdsale {
 
     /**
      * @dev Constructor, takes token wallet address.
-     * @param tokenWallet Address holding the tokens, which has approved allowance to the crowdsale
+     * @param tokenWallet Address holding the tokens, which has approved allowance to the crowdsale.
      */
     constructor (address tokenWallet) public {
-        require(tokenWallet != address(0));
+        require(tokenWallet != address(0), "AllowanceCrowdsale: token wallet is the zero address");
         _tokenWallet = tokenWallet;
     }
 

contracts/crowdsale/emission/MintedCrowdsale.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../Crowdsale.sol";
 import "../../token/ERC20/ERC20Mintable.sol";
@@ -16,6 +16,9 @@ contract MintedCrowdsale is Crowdsale {
      */
     function _deliverTokens(address beneficiary, uint256 tokenAmount) internal {
         // Potentially dangerous assumption about the type of the token.
-        require(ERC20Mintable(address(token())).mint(beneficiary, tokenAmount));
+        require(
+            ERC20Mintable(address(token())).mint(beneficiary, tokenAmount),
+                "MintedCrowdsale: minting failed"
+        );
     }
 }

contracts/crowdsale/price/IncreasingPriceCrowdsale.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../validation/TimedCrowdsale.sol";
 import "../../math/SafeMath.sol";
@@ -21,8 +21,9 @@ contract IncreasingPriceCrowdsale is TimedCrowdsale {
      * @param finalRate Number of tokens a buyer gets per wei at the end of the crowdsale
      */
     constructor (uint256 initialRate, uint256 finalRate) public {
-        require(finalRate > 0);
-        require(initialRate > finalRate);
+        require(finalRate > 0, "IncreasingPriceCrowdsale: final rate is 0");
+        // solhint-disable-next-line max-line-length
+        require(initialRate > finalRate, "IncreasingPriceCrowdsale: initial rate is not greater than final rate");
         _initialRate = initialRate;
         _finalRate = finalRate;
     }
@@ -32,7 +33,7 @@ contract IncreasingPriceCrowdsale is TimedCrowdsale {
      * all calls to it are a mistake.
      */
     function rate() public view returns (uint256) {
-        revert();
+        revert("IncreasingPriceCrowdsale: rate() called");
     }
 
     /**

contracts/crowdsale/validation/CappedCrowdsale.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../../math/SafeMath.sol";
 import "../Crowdsale.sol";
@@ -17,7 +17,7 @@ contract CappedCrowdsale is Crowdsale {
      * @param cap Max amount of wei to be contributed
      */
     constructor (uint256 cap) public {
-        require(cap > 0);
+        require(cap > 0, "CappedCrowdsale: cap is 0");
         _cap = cap;
     }
 
@@ -43,6 +43,6 @@ contract CappedCrowdsale is Crowdsale {
      */
     function _preValidatePurchase(address beneficiary, uint256 weiAmount) internal view {
         super._preValidatePurchase(beneficiary, weiAmount);
-        require(weiRaised().add(weiAmount) <= _cap);
+        require(weiRaised().add(weiAmount) <= _cap, "CappedCrowdsale: cap exceeded");
     }
 }

contracts/crowdsale/validation/IndividuallyCappedCrowdsale.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../../math/SafeMath.sol";
 import "../Crowdsale.sol";
@@ -48,11 +48,12 @@ contract IndividuallyCappedCrowdsale is Crowdsale, CapperRole {
      */
     function _preValidatePurchase(address beneficiary, uint256 weiAmount) internal view {
         super._preValidatePurchase(beneficiary, weiAmount);
-        require(_contributions[beneficiary].add(weiAmount) <= _caps[beneficiary]);
+        // solhint-disable-next-line max-line-length
+        require(_contributions[beneficiary].add(weiAmount) <= _caps[beneficiary], "IndividuallyCappedCrowdsale: beneficiary's cap exceeded");
     }
 
     /**
-     * @dev Extend parent behavior to update beneficiary contributions
+     * @dev Extend parent behavior to update beneficiary contributions.
      * @param beneficiary Token purchaser
      * @param weiAmount Amount of wei contributed
      */

contracts/crowdsale/validation/PausableCrowdsale.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../Crowdsale.sol";
 import "../../lifecycle/Pausable.sol";

contracts/crowdsale/validation/TimedCrowdsale.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../../math/SafeMath.sol";
 import "../Crowdsale.sol";
@@ -24,7 +24,7 @@ contract TimedCrowdsale is Crowdsale {
      * @dev Reverts if not in crowdsale time range.
      */
     modifier onlyWhileOpen {
-        require(isOpen());
+        require(isOpen(), "TimedCrowdsale: not open");
         _;
     }
 
@@ -35,8 +35,9 @@ contract TimedCrowdsale is Crowdsale {
      */
     constructor (uint256 openingTime, uint256 closingTime) public {
         // solhint-disable-next-line not-rely-on-time
-        require(openingTime >= block.timestamp);
-        require(closingTime > openingTime);
+        require(openingTime >= block.timestamp, "TimedCrowdsale: opening time is before current time");
+        // solhint-disable-next-line max-line-length
+        require(closingTime > openingTime, "TimedCrowdsale: opening time is not before closing time");
 
         _openingTime = openingTime;
         _closingTime = closingTime;
@@ -74,7 +75,7 @@ contract TimedCrowdsale is Crowdsale {
     }
 
     /**
-     * @dev Extend parent behavior requiring to be within contributing period
+     * @dev Extend parent behavior requiring to be within contributing period.
      * @param beneficiary Token purchaser
      * @param weiAmount Amount of wei contributed
      */
@@ -83,12 +84,13 @@ contract TimedCrowdsale is Crowdsale {
     }
 
     /**
-     * @dev Extend crowdsale
+     * @dev Extend crowdsale.
      * @param newClosingTime Crowdsale closing time
      */
     function _extendTime(uint256 newClosingTime) internal {
-        require(!hasClosed());
-        require(newClosingTime > _closingTime);
+        require(!hasClosed(), "TimedCrowdsale: already closed");
+        // solhint-disable-next-line max-line-length
+        require(newClosingTime > _closingTime, "TimedCrowdsale: new closing time is before current closing time");
 
         emit TimedCrowdsaleExtended(_closingTime, newClosingTime);
         _closingTime = newClosingTime;

contracts/crowdsale/validation/WhitelistCrowdsale.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 import "../Crowdsale.sol";
 import "../../access/roles/WhitelistedRole.sol";
 
@@ -15,7 +15,7 @@ contract WhitelistCrowdsale is WhitelistedRole, Crowdsale {
      * @param _weiAmount Amount of wei contributed
      */
     function _preValidatePurchase(address _beneficiary, uint256 _weiAmount) internal view {
-        require(isWhitelisted(_beneficiary));
+        require(isWhitelisted(_beneficiary), "WhitelistCrowdsale: beneficiary doesn't have the Whitelisted role");
         super._preValidatePurchase(_beneficiary, _weiAmount);
     }
 }

contracts/cryptography/ECDSA.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 /**
  * @title Elliptic curve signature operations
@@ -9,7 +9,7 @@ pragma solidity ^0.5.2;
 
 library ECDSA {
     /**
-     * @dev Recover signer address from a message by using their signature
+     * @dev Recover signer address from a message by using their signature.
      * @param hash bytes32 message, the hash is the signed message. What is recovered is the signer address.
      * @param signature bytes signature, the signature is generated using web3.eth.sign()
      */
@@ -56,8 +56,8 @@ library ECDSA {
 
     /**
      * toEthSignedMessageHash
-     * @dev prefix a bytes32 value with "\x19Ethereum Signed Message:"
-     * and hash the result
+     * @dev Prefix a bytes32 value with "\x19Ethereum Signed Message:"
+     * and hash the result.
      */
     function toEthSignedMessageHash(bytes32 hash) internal pure returns (bytes32) {
         // 32 is the length in bytes of hash,

contracts/cryptography/MerkleProof.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 /**
  * @title MerkleProof

contracts/drafts/Counters.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../math/SafeMath.sol";
 
@@ -6,7 +6,7 @@ import "../math/SafeMath.sol";
  * @title Counters
  * @author Matt Condon (@shrugs)
  * @dev Provides counters that can only be incremented or decremented by one. This can be used e.g. to track the number
- * of elements in a mapping, issuing ERC721 ids, or counting request ids
+ * of elements in a mapping, issuing ERC721 ids, or counting request ids.
  *
  * Include with `using Counters for Counters.Counter;`
  * Since it is not possible to overflow a 256 bit integer with increments of one, `increment` can skip the SafeMath

contracts/drafts/ERC1046/ERC20Metadata.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../../token/ERC20/IERC20.sol";
 

contracts/drafts/ERC1820Implementer.sol

@@ -0,0 +1,24 @@
+pragma solidity ^0.5.7;
+
+import "./IERC1820Implementer.sol";
+
+/**
+ * @dev ERC1820Implementer allows your contract to implement an interface for another account in the sense of ERC1820.
+ * That account or one of its ERC1820 managers can register the implementer in the ERC1820 registry, but the registry
+ * will first check with the implementer if it agrees to it, and only allow it if it does. Using the internal
+ * function _registerInterfaceForAddress provided by this contract, you are expressing this agreement,
+ * and you will be able to register the contract as an implementer in the registry for that account.
+ */
+contract ERC1820Implementer is IERC1820Implementer {
+    bytes32 constant private ERC1820_ACCEPT_MAGIC = keccak256(abi.encodePacked("ERC1820_ACCEPT_MAGIC"));
+
+    mapping(bytes32 => mapping(address => bool)) private _supportedInterfaces;
+
+    function canImplementInterfaceForAddress(bytes32 interfaceHash, address account) external view returns (bytes32) {
+        return _supportedInterfaces[interfaceHash][account] ? ERC1820_ACCEPT_MAGIC : bytes32(0x00);
+    }
+
+    function _registerInterfaceForAddress(bytes32 interfaceHash, address account) internal {
+        _supportedInterfaces[interfaceHash][account] = true;
+    }
+}

contracts/drafts/ERC20Migrator.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../token/ERC20/IERC20.sol";
 import "../token/ERC20/ERC20Mintable.sol";
@@ -44,7 +44,7 @@ contract ERC20Migrator {
      * @param legacyToken address of the old token contract
      */
     constructor (IERC20 legacyToken) public {
-        require(address(legacyToken) != address(0));
+        require(address(legacyToken) != address(0), "ERC20Migrator: legacy token is the zero address");
         _legacyToken = legacyToken;
     }
 
@@ -68,9 +68,10 @@ contract ERC20Migrator {
      * @param newToken_ the token that will be minted
      */
     function beginMigration(ERC20Mintable newToken_) public {
-        require(address(_newToken) == address(0));
-        require(address(newToken_) != address(0));
-        require(newToken_.isMinter(address(this)));
+        require(address(_newToken) == address(0), "ERC20Migrator: migration already started");
+        require(address(newToken_) != address(0), "ERC20Migrator: new token is the zero address");
+        //solhint-disable-next-line max-line-length
+        require(newToken_.isMinter(address(this)), "ERC20Migrator: not a minter for new token");
 
         _newToken = newToken_;
     }
@@ -82,7 +83,7 @@ contract ERC20Migrator {
      * @param amount amount of tokens to be migrated
      */
     function migrate(address account, uint256 amount) public {
-        require(address(_newToken) != address(0));
+        require(address(_newToken) != address(0), "ERC20Migrator: migration not started");
         _legacyToken.safeTransferFrom(account, address(this), amount);
         _newToken.mint(account, amount);
     }

contracts/drafts/ERC20Snapshot.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../math/SafeMath.sol";
 import "../utils/Arrays.sol";
@@ -31,7 +31,7 @@ contract ERC20Snapshot is ERC20 {
     }
 
     mapping (address => Snapshots) private _accountBalanceSnapshots;
-    Snapshots private _totalSupplySnaphots;
+    Snapshots private _totalSupplySnapshots;
 
     // Snapshot ids increase monotonically, with the first value being 1. An id of 0 is invalid.
     Counters.Counter private _currentSnapshotId;
@@ -56,7 +56,7 @@ contract ERC20Snapshot is ERC20 {
     }
 
     function totalSupplyAt(uint256 snapshotId) public view returns(uint256) {
-        (bool snapshotted, uint256 value) = _valueAt(snapshotId, _totalSupplySnaphots);
+        (bool snapshotted, uint256 value) = _valueAt(snapshotId, _totalSupplySnapshots);
 
         return snapshotted ? value : totalSupply();
     }
@@ -101,8 +101,9 @@ contract ERC20Snapshot is ERC20 {
     function _valueAt(uint256 snapshotId, Snapshots storage snapshots)
         private view returns (bool, uint256)
     {
-        require(snapshotId > 0);
-        require(snapshotId <= _currentSnapshotId.current());
+        require(snapshotId > 0, "ERC20Snapshot: id is 0");
+        // solhint-disable-next-line max-line-length
+        require(snapshotId <= _currentSnapshotId.current(), "ERC20Snapshot: nonexistent id");
 
         uint256 index = snapshots.ids.findUpperBound(snapshotId);
 
@@ -118,7 +119,7 @@ contract ERC20Snapshot is ERC20 {
     }
 
     function _updateTotalSupplySnapshot() private {
-        _updateSnapshot(_totalSupplySnaphots, totalSupply());
+        _updateSnapshot(_totalSupplySnapshots, totalSupply());
     }
 
     function _updateSnapshot(Snapshots storage snapshots, uint256 currentValue) private {

contracts/drafts/ERC777/ERC777.sol

@@ -0,0 +1,357 @@
+pragma solidity ^0.5.7;
+
+import "./IERC777.sol";
+import "./IERC777Recipient.sol";
+import "./IERC777Sender.sol";
+import "../../math/SafeMath.sol";
+import "../../utils/Address.sol";
+import "../IERC1820Registry.sol";
+
+/**
+ * @title ERC777 token implementation
+ * @author etsvigun <utgarda@gmail.com>, Bertrand Masius <github@catageeks.tk>
+ */
+contract ERC777 is IERC777 {
+    using SafeMath for uint256;
+    using Address for address;
+
+    IERC1820Registry private _erc1820 = IERC1820Registry(0x1820a4B7618BdE71Dce8cdc73aAB6C95905faD24);
+
+    string private _name;
+
+    string private _symbol;
+
+    mapping(address => uint256) private _balances;
+
+    uint256 private _totalSupply;
+
+    uint256 private _granularity;
+
+    bytes32 constant private TOKENS_SENDER_INTERFACE_HASH = keccak256("ERC777TokensSender");
+    bytes32 constant private TOKENS_RECIPIENT_INTERFACE_HASH = keccak256("ERC777TokensRecipient");
+
+    // This isn't ever read from - it's only used to respond to the defaultOperators query.
+    address[] private _defaultOperatorsArray;
+
+    // Immutable, but accounts may revoke them (tracked in __revokedDefaultOperators).
+    mapping(address => bool) private _defaultOperators;
+
+    // For each account, a mapping of its operators and revoked default operators.
+    mapping(address => mapping(address => bool)) private _operators;
+    mapping(address => mapping(address => bool)) private _revokedDefaultOperators;
+
+    constructor(
+        string memory name,
+        string memory symbol,
+        uint256 granularity,
+        address[] memory defaultOperators
+    ) public {
+        require(granularity > 0);
+
+        _name = name;
+        _symbol = symbol;
+        _granularity = granularity;
+
+        _defaultOperatorsArray = defaultOperators;
+        for (uint256 i = 0; i < _defaultOperatorsArray.length; i++) {
+            _defaultOperators[_defaultOperatorsArray[i]] = true;
+        }
+
+        // register interface
+        _erc1820.setInterfaceImplementer(address(this), keccak256("ERC777Token"), address(this));
+    }
+
+    /**
+     * @dev Send the amount of tokens from the address msg.sender to the address to
+     * @param to address recipient address
+     * @param amount uint256 amount of tokens to transfer
+     * @param data bytes information attached to the send, and intended for the recipient (to)
+     */
+    function send(address to, uint256 amount, bytes calldata data) external {
+        _send(msg.sender, msg.sender, to, amount, data, "");
+    }
+
+    /**
+     * @dev Send the amount of tokens on behalf of the address from to the address to
+     * @param from address token holder address.
+     * @param to address recipient address
+     * @param amount uint256 amount of tokens to transfer
+     * @param data bytes information attached to the send, and intended for the recipient (to)
+     * @param operatorData bytes extra information provided by the operator (if any)
+     */
+    function operatorSend(
+        address from,
+        address to,
+        uint256 amount,
+        bytes calldata data,
+        bytes calldata operatorData
+    )
+    external
+    {
+        require(isOperatorFor(msg.sender, from));
+        _send(msg.sender, from, to, amount, data, operatorData);
+    }
+
+    /**
+     * @dev Burn the amount of tokens from the address msg.sender
+     * @param amount uint256 amount of tokens to transfer
+     * @param data bytes extra information provided by the token holder
+     */
+    function burn(uint256 amount, bytes calldata data) external {
+        _burn(msg.sender, msg.sender, amount, data, "");
+    }
+
+    /**
+     * @dev Burn the amount of tokens on behalf of the address from
+     * @param from address token holder address.
+     * @param amount uint256 amount of tokens to transfer
+     * @param data bytes extra information provided by the token holder
+     * @param operatorData bytes extra information provided by the operator (if any)
+     */
+    function operatorBurn(address from, uint256 amount, bytes calldata data, bytes calldata operatorData) external {
+        require(isOperatorFor(msg.sender, from));
+        _burn(msg.sender, from, amount, data, operatorData);
+    }
+
+    /**
+     * @dev Authorize an operator for the sender
+     * @param operator address to be authorized as operator
+     */
+    function authorizeOperator(address operator) external {
+        require(msg.sender != operator);
+
+        if (_defaultOperators[operator]) {
+            delete _revokedDefaultOperators[msg.sender][operator];
+        } else {
+            _operators[msg.sender][operator] = true;
+        }
+
+        emit AuthorizedOperator(operator, msg.sender);
+    }
+
+    /**
+     * @dev Revoke operator rights from one of the default operators
+     * @param operator address to revoke operator rights from
+     */
+    function revokeOperator(address operator) external {
+        require(operator != msg.sender);
+
+        if (_defaultOperators[operator]) {
+            _revokedDefaultOperators[msg.sender][operator] = true;
+        } else {
+            delete _operators[msg.sender][operator];
+        }
+
+        emit RevokedOperator(operator, msg.sender);
+    }
+
+    /**
+     * @return the name of the token.
+     */
+    function name() public view returns (string memory) {
+        return _name;
+    }
+
+    /**
+     * @return the symbol of the token.
+     */
+    function symbol() public view returns (string memory) {
+        return _symbol;
+    }
+
+    /**
+     * @dev Total number of tokens in existence
+     */
+    function totalSupply() public view returns (uint256) {
+        return _totalSupply;
+    }
+
+    /**
+     * @dev Gets the balance of the specified address.
+     * @param tokenHolder The address to query the balance of.
+        * @return uint256 representing the amount owned by the specified address.
+     */
+    function balanceOf(address tokenHolder) public view returns (uint256) {
+        return _balances[tokenHolder];
+    }
+
+    /**
+     * @dev Gets the token's granularity,
+     * i.e. the smallest number of tokens (in the basic unit)
+     * which may be minted, sent or burned at any time
+     * @return uint256 granularity
+     */
+    function granularity() public view returns (uint256) {
+        return _granularity;
+    }
+
+    /**
+     * @dev Get the list of default operators as defined by the token contract.
+     * @return address[] default operators
+     */
+    function defaultOperators() public view returns (address[] memory) {
+        return _defaultOperatorsArray;
+    }
+
+    /**
+     * @dev Indicate whether an address
+     * is an operator of the tokenHolder address
+     * @param operator address which may be an operator of tokenHolder
+     * @param tokenHolder address of a token holder which may have the operator
+     * address as an operator.
+     */
+    function isOperatorFor(
+        address operator,
+        address tokenHolder
+    ) public view returns (bool) {
+        return operator == tokenHolder ||
+            (_defaultOperators[operator] && !_revokedDefaultOperators[tokenHolder][operator]) ||
+            _operators[tokenHolder][operator];
+    }
+
+    /**
+     * @dev Mint tokens. Does not check authorization of operator
+     * @dev the caller may ckeck that operator is authorized before calling
+     * @param operator address operator requesting the operation
+     * @param to address token recipient address
+     * @param amount uint256 amount of tokens to mint
+     * @param userData bytes extra information defined by the token recipient (if any)
+     * @param operatorData bytes extra information provided by the operator (if any)
+     */
+    function _mint(
+        address operator,
+        address to,
+        uint256 amount,
+        bytes memory userData,
+        bytes memory operatorData
+    )
+    internal
+    {
+        require(to != address(0));
+        require((amount % _granularity) == 0);
+
+        // Update state variables
+        _totalSupply = _totalSupply.add(amount);
+        _balances[to] = _balances[to].add(amount);
+
+        _callTokensReceived(operator, address(0), to, amount, userData, operatorData);
+
+        emit Minted(operator, to, amount, userData, operatorData);
+    }
+
+    /**
+     * @dev Send tokens
+     * @param operator address operator requesting the transfer
+     * @param from address token holder address
+     * @param to address recipient address
+     * @param amount uint256 amount of tokens to transfer
+     * @param userData bytes extra information provided by the token holder (if any)
+     * @param operatorData bytes extra information provided by the operator (if any)
+     */
+    function _send(
+        address operator,
+        address from,
+        address to,
+        uint256 amount,
+        bytes memory userData,
+        bytes memory operatorData
+    )
+    private
+    {
+        require(from != address(0));
+        require(to != address(0));
+        require((amount % _granularity) == 0);
+
+        _callTokensToSend(operator, from, to, amount, userData, operatorData);
+
+        // Update state variables
+        _balances[from] = _balances[from].sub(amount);
+        _balances[to] = _balances[to].add(amount);
+
+        _callTokensReceived(operator, from, to, amount, userData, operatorData);
+
+        emit Sent(operator, from, to, amount, userData, operatorData);
+    }
+
+    /**
+     * @dev Burn tokens
+     * @param operator address operator requesting the operation
+     * @param from address token holder address
+     * @param amount uint256 amount of tokens to burn
+     * @param data bytes extra information provided by the token holder
+     * @param operatorData bytes extra information provided by the operator (if any)
+     */
+    function _burn(
+        address operator,
+        address from,
+        uint256 amount,
+        bytes memory data,
+        bytes memory operatorData
+    )
+    private
+    {
+        require(from != address(0));
+        require((amount % _granularity) == 0);
+
+        _callTokensToSend(operator, from, address(0), amount, data, operatorData);
+
+        // Update state variables
+        _totalSupply = _totalSupply.sub(amount);
+        _balances[from] = _balances[from].sub(amount);
+
+        emit Burned(operator, from, amount, data, operatorData);
+    }
+
+    /**
+     * @dev Call from.tokensToSend() if the interface is registered
+     * @param operator address operator requesting the transfer
+     * @param from address token holder address
+     * @param to address recipient address
+     * @param amount uint256 amount of tokens to transfer
+     * @param userData bytes extra information provided by the token holder (if any)
+     * @param operatorData bytes extra information provided by the operator (if any)
+     */
+    function _callTokensToSend(
+        address operator,
+        address from,
+        address to,
+        uint256 amount,
+        bytes memory userData,
+        bytes memory operatorData
+    )
+    private
+    {
+        address implementer = _erc1820.getInterfaceImplementer(from, TOKENS_SENDER_INTERFACE_HASH);
+        if (implementer != address(0)) {
+            IERC777Sender(implementer).tokensToSend(operator, from, to, amount, userData, operatorData);
+        }
+    }
+
+    /**
+     * @dev Call to.tokensReceived() if the interface is registered. Reverts if the recipient is a contract but
+     * tokensReceived() was not registered for the recipient
+     * @param operator address operator requesting the transfer
+     * @param from address token holder address
+     * @param to address recipient address
+     * @param amount uint256 amount of tokens to transfer
+     * @param userData bytes extra information provided by the token holder (if any)
+     * @param operatorData bytes extra information provided by the operator (if any)
+     */
+    function _callTokensReceived(
+        address operator,
+        address from,
+        address to,
+        uint256 amount,
+        bytes memory userData,
+        bytes memory operatorData
+    )
+    private
+    {
+        address implementer = _erc1820.getInterfaceImplementer(to, TOKENS_RECIPIENT_INTERFACE_HASH);
+        if (implementer != address(0)) {
+            IERC777Recipient(implementer).tokensReceived(operator, from, to, amount, userData, operatorData);
+        } else {
+            require(!to.isContract());
+        }
+    }
+}

contracts/drafts/ERC777/IERC777.sol

@@ -0,0 +1,61 @@
+pragma solidity ^0.5.7;
+
+/**
+ * @title ERC777 token interface
+ * @dev See https://eips.ethereum.org/EIPS/eip-777
+ */
+interface IERC777 {
+    function authorizeOperator(address operator) external;
+
+    function revokeOperator(address operator) external;
+
+    function send(address to, uint256 amount, bytes calldata data) external;
+
+    function operatorSend(
+        address from,
+        address to,
+        uint256 amount,
+        bytes calldata data,
+        bytes calldata operatorData
+    ) external;
+
+    function burn(uint256 amount, bytes calldata data) external;
+
+    function operatorBurn(
+        address from,
+        uint256 amount,
+        bytes calldata data,
+        bytes calldata operatorData
+    ) external;
+
+    function name() external view returns (string memory);
+
+    function symbol() external view returns (string memory);
+
+    function totalSupply() external view returns (uint256);
+
+    function balanceOf(address owner) external view returns (uint256);
+
+    function granularity() external view returns (uint256);
+
+    function defaultOperators() external view returns (address[] memory);
+
+    function isOperatorFor(address operator, address tokenHolder) external view returns (bool);
+
+    event Sent(
+        address indexed operator,
+        address indexed from,
+        address indexed to,
+        uint256 amount,
+        bytes data,
+        bytes operatorData
+    );
+
+    event Minted(address indexed operator, address indexed to, uint256 amount, bytes data, bytes operatorData);
+
+    event Burned(address indexed operator, address indexed from, uint256 amount, bytes data, bytes operatorData);
+
+    event AuthorizedOperator(address indexed operator, address indexed tokenHolder);
+
+    event RevokedOperator(address indexed operator, address indexed tokenHolder);
+}

contracts/drafts/ERC777/IERC777Recipient.sol

@@ -0,0 +1,16 @@
+pragma solidity ^0.5.7;
+
+/**
+ * @title ERC777 token recipient interface
+ * @dev See https://eips.ethereum.org/EIPS/eip-777
+ */
+interface IERC777Recipient {
+    function tokensReceived(
+        address operator,
+        address from,
+        address to,
+        uint amount,
+        bytes calldata userData,
+        bytes calldata operatorData
+    ) external;
+}

contracts/drafts/ERC777/IERC777Sender.sol

@@ -0,0 +1,16 @@
+pragma solidity ^0.5.7;
+
+/**
+ * @title ERC777 token sender interface
+ * @dev See https://eips.ethereum.org/EIPS/eip-777
+ */
+interface IERC777Sender {
+    function tokensToSend(
+        address operator,
+        address from,
+        address to,
+        uint amount,
+        bytes calldata userData,
+        bytes calldata operatorData
+    ) external;
+}

contracts/drafts/IERC1820Implementer.sol

@@ -0,0 +1,17 @@
+pragma solidity ^0.5.7;
+
+/**
+ * @title IERC1820Implementer
+ * Interface for contracts that will be registered as implementers in the ERC1820 registry.
+ * @notice For more details, see https://eips.ethereum.org/EIPS/eip-1820
+ */
+interface IERC1820Implementer {
+    /**
+     * @notice Indicates whether the contract implements the interface `interfaceHash` for the address `account` or
+     * not.
+     * @param interfaceHash keccak256 hash of the name of the interface
+     * @param account Address for which the contract will implement the interface
+     * @return ERC1820_ACCEPT_MAGIC only if the contract implements `interfaceHash` for the address `account`.
+     */
+    function canImplementInterfaceForAddress(bytes32 interfaceHash, address account) external view returns (bytes32);
+}

contracts/drafts/IERC1820Registry.sol

@@ -0,0 +1,90 @@
+pragma solidity ^0.5.7;
+
+/**
+ * @title ERC1820 Pseudo-introspection Registry Contract
+ * @author Jordi Baylina and Jacques Dafflon
+ * @notice For more details, see https://eips.ethereum.org/EIPS/eip-1820
+ */
+interface IERC1820Registry {
+    /**
+     * @notice Sets the contract which implements a specific interface for an address.
+     * Only the manager defined for that address can set it.
+     * (Each address is the manager for itself until it sets a new manager.)
+     * @param account Address for which to set the interface.
+     * (If 'account' is the zero address then 'msg.sender' is assumed.)
+     * @param interfaceHash Keccak256 hash of the name of the interface as a string.
+     * E.g., 'web3.utils.keccak256("ERC777TokensRecipient")' for the 'ERC777TokensRecipient' interface.
+     * @param implementer Contract address implementing `interfaceHash` for `account.address()`.
+     */
+    function setInterfaceImplementer(address account, bytes32 interfaceHash, address implementer) external;
+
+    /**
+     * @notice Sets `newManager.address()` as manager for `account.address()`.
+     * The new manager will be able to call 'setInterfaceImplementer' for `account.address()`.
+     * @param account Address for which to set the new manager.
+     * @param newManager Address of the new manager for `addr.address()`.
+     * (Pass '0x0' to reset the manager to `account.address()`.)
+     */
+    function setManager(address account, address newManager) external;
+
+    /**
+     *  @notice Updates the cache with whether the contract implements an ERC165 interface or not.
+     *  @param account Address of the contract for which to update the cache.
+     *  @param interfaceId ERC165 interface for which to update the cache.
+     */
+    function updateERC165Cache(address account, bytes4 interfaceId) external;
+
+    /**
+     *  @notice Get the manager of an address.
+     *  @param account Address for which to return the manager.
+     *  @return Address of the manager for a given address.
+     */
+    function getManager(address account) external view returns (address);
+
+    /**
+     *  @notice Query if an address implements an interface and through which contract.
+     *  @param account Address being queried for the implementer of an interface.
+     *  (If 'account' is the zero address then 'msg.sender' is assumed.)
+     *  @param interfaceHash Keccak256 hash of the name of the interface as a string.
+     *  E.g., 'web3.utils.keccak256("ERC777TokensRecipient")' for the 'ERC777TokensRecipient' interface.
+     *  @return The address of the contract which implements the interface `interfaceHash` for `account.address()`
+     *  or '0' if `account.address()` did not register an implementer for this interface.
+     */
+    function getInterfaceImplementer(address account, bytes32 interfaceHash) external view returns (address);
+
+    /**
+     *  @notice Checks whether a contract implements an ERC165 interface or not.
+     *  If the result is not cached a direct lookup on the contract address is performed.
+     *  If the result is not cached or the cached value is out-of-date, the cache MUST be updated manually by calling
+     *  'updateERC165Cache' with the contract address.
+     *  @param account Address of the contract to check.
+     *  @param interfaceId ERC165 interface to check.
+     *  @return True if `account.address()` implements `interfaceId`, false otherwise.
+     */
+    function implementsERC165Interface(address account, bytes4 interfaceId) external view returns (bool);
+
+    /**
+     *  @notice Checks whether a contract implements an ERC165 interface or not without using nor updating the cache.
+     *  @param account Address of the contract to check.
+     *  @param interfaceId ERC165 interface to check.
+     *  @return True if `account.address()` implements `interfaceId`, false otherwise.
+     */
+    function implementsERC165InterfaceNoCache(address account, bytes4 interfaceId) external view returns (bool);
+
+    /**
+     *  @notice Compute the keccak256 hash of an interface given its name.
+     *  @param interfaceName Name of the interface.
+     *  @return The keccak256 hash of an interface name.
+     */
+    function interfaceHash(string calldata interfaceName) external pure returns (bytes32);
+
+    /**
+     *  @notice Indicates a contract is the `implementer` of `interfaceHash` for `account`.
+     */
+    event InterfaceImplementerSet(address indexed account, bytes32 indexed interfaceHash, address indexed implementer);
+
+    /**
+     *  @notice Indicates `newManager` is the address of the new manager for `account`.
+     */
+    event ManagerChanged(address indexed account, address indexed newManager);
+}

contracts/drafts/SignatureBouncer.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../access/roles/SignerRole.sol";
 import "../cryptography/ECDSA.sol";
@@ -48,26 +48,28 @@ contract SignatureBouncer is SignerRole {
     }
 
     /**
-     * @dev requires that a valid signature of a signer was provided
+     * @dev Requires that a valid signature of a signer was provided.
      */
     modifier onlyValidSignature(bytes memory signature) {
-        require(_isValidSignature(msg.sender, signature));
+        require(_isValidSignature(msg.sender, signature), "SignatureBouncer: invalid signature for caller");
         _;
     }
 
     /**
-     * @dev requires that a valid signature with a specified method of a signer was provided
+     * @dev Requires that a valid signature with a specified method of a signer was provided.
      */
     modifier onlyValidSignatureAndMethod(bytes memory signature) {
-        require(_isValidSignatureAndMethod(msg.sender, signature));
+        // solhint-disable-next-line max-line-length
+        require(_isValidSignatureAndMethod(msg.sender, signature), "SignatureBouncer: invalid signature for caller and method");
         _;
     }
 
     /**
-     * @dev requires that a valid signature with a specified method and params of a signer was provided
+     * @dev Requires that a valid signature with a specified method and params of a signer was provided.
      */
     modifier onlyValidSignatureAndData(bytes memory signature) {
-        require(_isValidSignatureAndData(msg.sender, signature));
+        // solhint-disable-next-line max-line-length
+        require(_isValidSignatureAndData(msg.sender, signature), "SignatureBouncer: invalid signature for caller and data");
         _;
     }
 
@@ -97,7 +99,7 @@ contract SignatureBouncer is SignerRole {
      * @return bool
      */
     function _isValidSignatureAndData(address account, bytes memory signature) internal view returns (bool) {
-        require(msg.data.length > _SIGNATURE_SIZE);
+        require(msg.data.length > _SIGNATURE_SIZE, "SignatureBouncer: data is too short");
 
         bytes memory data = new bytes(msg.data.length - _SIGNATURE_SIZE);
         for (uint i = 0; i < data.length; i++) {
@@ -108,8 +110,8 @@ contract SignatureBouncer is SignerRole {
     }
 
     /**
-     * @dev internal function to convert a hash to an eth signed message
-     * and then recover the signature and check it against the signer role
+     * @dev Internal function to convert a hash to an eth signed message
+     * and then recover the signature and check it against the signer role.
      * @return bool
      */
     function _isValidDataHash(bytes32 hash, bytes memory signature) internal view returns (bool) {

contracts/drafts/SignedSafeMath.sol

@@ -1,8 +1,8 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 /**
  * @title SignedSafeMath
- * @dev Signed math operations with safety checks that revert on error
+ * @dev Signed math operations with safety checks that revert on error.
  */
 library SignedSafeMath {
     int256 constant private INT256_MIN = -2**255;
@@ -18,10 +18,10 @@ library SignedSafeMath {
             return 0;
         }
 
-        require(!(a == -1 && b == INT256_MIN)); // This is the only case of overflow not detected by the check below
+        require(!(a == -1 && b == INT256_MIN), "SignedSafeMath: multiplication overflow");
 
         int256 c = a * b;
-        require(c / a == b);
+        require(c / a == b, "SignedSafeMath: multiplication overflow");
 
         return c;
     }
@@ -30,8 +30,8 @@ library SignedSafeMath {
      * @dev Integer division of two signed integers truncating the quotient, reverts on division by zero.
      */
     function div(int256 a, int256 b) internal pure returns (int256) {
-        require(b != 0); // Solidity only automatically asserts when dividing by 0
-        require(!(b == -1 && a == INT256_MIN)); // This is the only case of overflow
+        require(b != 0, "SignedSafeMath: division by zero");
+        require(!(b == -1 && a == INT256_MIN), "SignedSafeMath: division overflow");
 
         int256 c = a / b;
 
@@ -43,7 +43,7 @@ library SignedSafeMath {
      */
     function sub(int256 a, int256 b) internal pure returns (int256) {
         int256 c = a - b;
-        require((b >= 0 && c <= a) || (b < 0 && c > a));
+        require((b >= 0 && c <= a) || (b < 0 && c > a), "SignedSafeMath: subtraction overflow");
 
         return c;
     }
@@ -53,7 +53,7 @@ library SignedSafeMath {
      */
     function add(int256 a, int256 b) internal pure returns (int256) {
         int256 c = a + b;
-        require((b >= 0 && c >= a) || (b < 0 && c < a));
+        require((b >= 0 && c >= a) || (b < 0 && c < a), "SignedSafeMath: addition overflow");
 
         return c;
     }

contracts/drafts/TokenVesting.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../token/ERC20/SafeERC20.sol";
 import "../ownership/Ownable.sol";
@@ -47,10 +47,12 @@ contract TokenVesting is Ownable {
      * @param revocable whether the vesting is revocable or not
      */
     constructor (address beneficiary, uint256 start, uint256 cliffDuration, uint256 duration, bool revocable) public {
-        require(beneficiary != address(0));
-        require(cliffDuration <= duration);
-        require(duration > 0);
-        require(start.add(duration) > block.timestamp);
+        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;
@@ -115,7 +117,7 @@ contract TokenVesting is Ownable {
     function release(IERC20 token) public {
         uint256 unreleased = _releasableAmount(token);
 
-        require(unreleased > 0);
+        require(unreleased > 0, "TokenVesting: no tokens are due");
 
         _released[address(token)] = _released[address(token)].add(unreleased);
 
@@ -130,8 +132,8 @@ contract TokenVesting is Ownable {
      * @param token ERC20 token which is being vested
      */
     function revoke(IERC20 token) public onlyOwner {
-        require(_revocable);
-        require(!_revoked[address(token)]);
+        require(_revocable, "TokenVesting: cannot revoke");
+        require(!_revoked[address(token)], "TokenVesting: token already revoked");
 
         uint256 balance = token.balanceOf(address(this));
 

contracts/examples/SampleCrowdsale.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../crowdsale/validation/CappedCrowdsale.sol";
 import "../crowdsale/distribution/RefundableCrowdsale.sol";
@@ -48,6 +48,6 @@ contract SampleCrowdsale is CappedCrowdsale, RefundableCrowdsale, MintedCrowdsal
     {
         //As goal needs to be met for a successful crowdsale
         //the value needs to less or equal than a cap which is limit for accepted funds
-        require(goal <= cap);
+        require(goal <= cap, "SampleCrowdSale: goal is greater than cap");
     }
 }

contracts/examples/SimpleToken.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../token/ERC20/ERC20.sol";
 import "../token/ERC20/ERC20Detailed.sol";

contracts/introspection/ERC165.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "./IERC165.sol";
 
@@ -8,37 +8,36 @@ import "./IERC165.sol";
  * @dev Implements ERC165 using a lookup table.
  */
 contract ERC165 is IERC165 {
-    bytes4 private constant _INTERFACE_ID_ERC165 = 0x01ffc9a7;
     /*
-     * 0x01ffc9a7 ===
-     *     bytes4(keccak256('supportsInterface(bytes4)'))
+     * bytes4(keccak256('supportsInterface(bytes4)')) == 0x01ffc9a7
      */
+    bytes4 private constant _INTERFACE_ID_ERC165 = 0x01ffc9a7;
 
     /**
-     * @dev a mapping of interface id to whether or not it's supported
+     * @dev Mapping of interface ids to whether or not it's supported.
      */
     mapping(bytes4 => bool) private _supportedInterfaces;
 
     /**
      * @dev A contract implementing SupportsInterfaceWithLookup
-     * implement ERC165 itself
+     * implements ERC165 itself.
      */
     constructor () internal {
         _registerInterface(_INTERFACE_ID_ERC165);
     }
 
     /**
-     * @dev implement supportsInterface(bytes4) using a lookup table
+     * @dev Implement supportsInterface(bytes4) using a lookup table.
      */
     function supportsInterface(bytes4 interfaceId) external view returns (bool) {
         return _supportedInterfaces[interfaceId];
     }
 
     /**
-     * @dev internal method for registering an interface
+     * @dev Internal method for registering an interface.
      */
     function _registerInterface(bytes4 interfaceId) internal {
-        require(interfaceId != 0xffffffff);
+        require(interfaceId != 0xffffffff, "ERC165: invalid interface id");
         _supportedInterfaces[interfaceId] = true;
     }
 }

contracts/introspection/ERC165Checker.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 /**
  * @title ERC165Checker
@@ -9,11 +9,10 @@ library ERC165Checker {
     // As per the EIP-165 spec, no interface should ever match 0xffffffff
     bytes4 private constant _INTERFACE_ID_INVALID = 0xffffffff;
 
-    bytes4 private constant _INTERFACE_ID_ERC165 = 0x01ffc9a7;
     /*
-     * 0x01ffc9a7 ===
-     *     bytes4(keccak256('supportsInterface(bytes4)'))
+     * bytes4(keccak256('supportsInterface(bytes4)')) == 0x01ffc9a7
      */
+    bytes4 private constant _INTERFACE_ID_ERC165 = 0x01ffc9a7;
 
     /**
      * @notice Query if a contract supports ERC165

contracts/introspection/IERC165.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 /**
  * @title IERC165

contracts/lifecycle/Pausable.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../access/roles/PauserRole.sol";
 
@@ -17,7 +17,7 @@ contract Pausable is PauserRole {
     }
 
     /**
-     * @return true if the contract is paused, false otherwise.
+     * @return True if the contract is paused, false otherwise.
      */
     function paused() public view returns (bool) {
         return _paused;
@@ -27,7 +27,7 @@ contract Pausable is PauserRole {
      * @dev Modifier to make a function callable only when the contract is not paused.
      */
     modifier whenNotPaused() {
-        require(!_paused);
+        require(!_paused, "Pausable: paused");
         _;
     }
 
@@ -35,12 +35,12 @@ contract Pausable is PauserRole {
      * @dev Modifier to make a function callable only when the contract is paused.
      */
     modifier whenPaused() {
-        require(_paused);
+        require(_paused, "Pausable: not paused");
         _;
     }
 
     /**
-     * @dev called by the owner to pause, triggers stopped state
+     * @dev Called by a pauser to pause, triggers stopped state.
      */
     function pause() public onlyPauser whenNotPaused {
         _paused = true;
@@ -48,7 +48,7 @@ contract Pausable is PauserRole {
     }
 
     /**
-     * @dev called by the owner to unpause, returns to normal state
+     * @dev Called by a pauser to unpause, returns to normal state.
      */
     function unpause() public onlyPauser whenPaused {
         _paused = false;

contracts/math/Math.sol

@@ -1,8 +1,8 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 /**
  * @title Math
- * @dev Assorted math operations
+ * @dev Assorted math operations.
  */
 library Math {
     /**

contracts/math/SafeMath.sol

@@ -1,8 +1,8 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 /**
  * @title SafeMath
- * @dev Unsigned math operations with safety checks that revert on error
+ * @dev Unsigned math operations with safety checks that revert on error.
  */
 library SafeMath {
     /**
@@ -17,7 +17,7 @@ library SafeMath {
         }
 
         uint256 c = a * b;
-        require(c / a == b);
+        require(c / a == b, "SafeMath: multiplication overflow");
 
         return c;
     }
@@ -27,7 +27,7 @@ library SafeMath {
      */
     function div(uint256 a, uint256 b) internal pure returns (uint256) {
         // Solidity only automatically asserts when dividing by 0
-        require(b > 0);
+        require(b > 0, "SafeMath: division by zero");
         uint256 c = a / b;
         // assert(a == b * c + a % b); // There is no case in which this doesn't hold
 
@@ -38,7 +38,7 @@ library SafeMath {
      * @dev Subtracts two unsigned integers, reverts on overflow (i.e. if subtrahend is greater than minuend).
      */
     function sub(uint256 a, uint256 b) internal pure returns (uint256) {
-        require(b <= a);
+        require(b <= a, "SafeMath: subtraction overflow");
         uint256 c = a - b;
 
         return c;
@@ -49,7 +49,7 @@ library SafeMath {
      */
     function add(uint256 a, uint256 b) internal pure returns (uint256) {
         uint256 c = a + b;
-        require(c >= a);
+        require(c >= a, "SafeMath: addition overflow");
 
         return c;
     }
@@ -59,7 +59,7 @@ library SafeMath {
      * reverts when dividing by zero.
      */
     function mod(uint256 a, uint256 b) internal pure returns (uint256) {
-        require(b != 0);
+        require(b != 0, "SafeMath: modulo by zero");
         return a % b;
     }
 }

contracts/mocks/Acknowledger.sol

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

contracts/mocks/AddressImpl.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../utils/Address.sol";
 

contracts/mocks/AllowanceCrowdsaleImpl.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../token/ERC20/IERC20.sol";
 import "../crowdsale/emission/AllowanceCrowdsale.sol";

contracts/mocks/ArraysImpl.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../utils/Arrays.sol";
 

contracts/mocks/CappedCrowdsaleImpl.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../token/ERC20/IERC20.sol";
 import "../crowdsale/validation/CappedCrowdsale.sol";

contracts/mocks/CapperRoleMock.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../access/roles/CapperRole.sol";
 

contracts/mocks/ConditionalEscrowMock.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../payment/escrow/ConditionalEscrow.sol";
 

contracts/mocks/CountersImpl.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../drafts/Counters.sol";
 

contracts/mocks/CrowdsaleMock.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../crowdsale/Crowdsale.sol";
 

contracts/mocks/ECDSAMock.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../cryptography/ECDSA.sol";
 

contracts/mocks/ERC165/ERC165InterfacesSupported.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../../introspection/IERC165.sol";
 
@@ -13,37 +13,36 @@ import "../../introspection/IERC165.sol";
  * solidity-coverage ignores the /mocks folder, so we duplicate its implementation here to avoid instrumenting it
  */
 contract SupportsInterfaceWithLookupMock is IERC165 {
-    bytes4 public constant INTERFACE_ID_ERC165 = 0x01ffc9a7;
     /*
-     * 0x01ffc9a7 ===
-     *     bytes4(keccak256('supportsInterface(bytes4)'))
+     * bytes4(keccak256('supportsInterface(bytes4)')) == 0x01ffc9a7
      */
+    bytes4 public constant INTERFACE_ID_ERC165 = 0x01ffc9a7;
 
     /**
-     * @dev a mapping of interface id to whether or not it's supported
+     * @dev A mapping of interface id to whether or not it's supported.
      */
     mapping(bytes4 => bool) private _supportedInterfaces;
 
     /**
      * @dev A contract implementing SupportsInterfaceWithLookup
-     * implement ERC165 itself
+     * implement ERC165 itself.
      */
     constructor () public {
         _registerInterface(INTERFACE_ID_ERC165);
     }
 
     /**
-     * @dev implement supportsInterface(bytes4) using a lookup table
+     * @dev Implement supportsInterface(bytes4) using a lookup table.
      */
     function supportsInterface(bytes4 interfaceId) external view returns (bool) {
         return _supportedInterfaces[interfaceId];
     }
 
     /**
-     * @dev private method for registering an interface
+     * @dev Private method for registering an interface.
      */
     function _registerInterface(bytes4 interfaceId) internal {
-        require(interfaceId != 0xffffffff);
+        require(interfaceId != 0xffffffff, "ERC165InterfacesSupported: invalid interface id");
         _supportedInterfaces[interfaceId] = true;
     }
 }

contracts/mocks/ERC165/ERC165NotSupported.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 contract ERC165NotSupported {
     // solhint-disable-previous-line no-empty-blocks

contracts/mocks/ERC165CheckerMock.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../introspection/ERC165Checker.sol";
 

contracts/mocks/ERC165Mock.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../introspection/ERC165.sol";
 

contracts/mocks/ERC1820ImplementerMock.sol

@@ -0,0 +1,9 @@
+pragma solidity ^0.5.7;
+
+import "../drafts/ERC1820Implementer.sol";
+
+contract ERC1820ImplementerMock is ERC1820Implementer {
+    function registerInterfaceForAddress(bytes32 interfaceHash, address account) public {
+        _registerInterfaceForAddress(interfaceHash, account);
+    }
+}

contracts/mocks/ERC20BurnableMock.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../token/ERC20/ERC20Burnable.sol";
 

contracts/mocks/ERC20DetailedMock.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../token/ERC20/ERC20.sol";
 import "../token/ERC20/ERC20Detailed.sol";

contracts/mocks/ERC20MetadataMock.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../token/ERC20/ERC20.sol";
 import "../drafts/ERC1046/ERC20Metadata.sol";

contracts/mocks/ERC20MintableMock.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../token/ERC20/ERC20Mintable.sol";
 import "./MinterRoleMock.sol";

contracts/mocks/ERC20Mock.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../token/ERC20/ERC20.sol";
 

contracts/mocks/ERC20PausableMock.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../token/ERC20/ERC20Pausable.sol";
 import "./PauserRoleMock.sol";

contracts/mocks/ERC20SnapshotMock.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../drafts/ERC20Snapshot.sol";
 

contracts/mocks/ERC721FullMock.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../token/ERC721/ERC721Full.sol";
 import "../token/ERC721/ERC721Mintable.sol";

contracts/mocks/ERC721MintableBurnableImpl.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../token/ERC721/ERC721Full.sol";
 import "../token/ERC721/ERC721Mintable.sol";

contracts/mocks/ERC721Mock.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../token/ERC721/ERC721.sol";
 

contracts/mocks/ERC721PausableMock.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../token/ERC721/ERC721Pausable.sol";
 import "./PauserRoleMock.sol";

contracts/mocks/ERC721ReceiverMock.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../token/ERC721/IERC721Receiver.sol";
 
@@ -16,7 +16,7 @@ contract ERC721ReceiverMock is IERC721Receiver {
     function onERC721Received(address operator, address from, uint256 tokenId, bytes memory data)
         public returns (bytes4)
     {
-        require(!_reverts);
+        require(!_reverts, "ERC721ReceiverMock: reverting");
         emit Received(operator, from, tokenId, data, gasleft());
         return _retval;
     }

contracts/mocks/ERC777Mock.sol

@@ -0,0 +1,26 @@
+pragma solidity ^0.5.7;
+
+import "../drafts/ERC777/ERC777.sol";
+
+contract ERC777Mock is ERC777 {
+    constructor(
+        address initialHolder,
+        uint256 initialBalance,
+        string memory name,
+        string memory symbol,
+        uint256 granularity,
+        address[] memory defaultOperators
+    ) public ERC777(name, symbol, granularity, defaultOperators) {
+        _mint(msg.sender, initialHolder, initialBalance, "", "");
+    }
+
+    function mintInternal (
+        address operator,
+        address to,
+        uint256 amount,
+        bytes memory userData,
+        bytes memory operatorData
+    ) public {
+        _mint(operator, to, amount, userData, operatorData);
+    }
+}

contracts/mocks/ERC777SenderRecipientMock.sol

@@ -0,0 +1,147 @@
+pragma solidity ^0.5.7;
+
+import "../drafts/ERC777/IERC777.sol";
+import "../drafts/ERC777/IERC777Sender.sol";
+import "../drafts/ERC777/IERC777Recipient.sol";
+import "../drafts/IERC1820Registry.sol";
+import "../drafts/ERC1820Implementer.sol";
+
+contract ERC777SenderRecipientMock is IERC777Sender, IERC777Recipient, ERC1820Implementer {
+    event TokensToSendCalled(
+        address operator,
+        address from,
+        address to,
+        uint256 amount,
+        bytes data,
+        bytes operatorData,
+        address token,
+        uint256 fromBalance,
+        uint256 toBalance
+    );
+
+    event TokensReceivedCalled(
+        address operator,
+        address from,
+        address to,
+        uint256 amount,
+        bytes data,
+        bytes operatorData,
+        address token,
+        uint256 fromBalance,
+        uint256 toBalance
+    );
+
+    bool private _shouldRevertSend;
+    bool private _shouldRevertReceive;
+
+    IERC1820Registry private _erc1820 = IERC1820Registry(0x1820a4B7618BdE71Dce8cdc73aAB6C95905faD24);
+
+    bytes32 constant private TOKENS_SENDER_INTERFACE_HASH = keccak256("ERC777TokensSender");
+    bytes32 constant private TOKENS_RECIPIENT_INTERFACE_HASH = keccak256("ERC777TokensRecipient");
+
+    function tokensToSend(
+        address operator,
+        address from,
+        address to,
+        uint amount,
+        bytes calldata userData,
+        bytes calldata operatorData
+    ) external {
+        if (_shouldRevertSend) {
+            revert();
+        }
+
+        IERC777 token = IERC777(msg.sender);
+
+        uint256 fromBalance = token.balanceOf(from);
+        // when called due to burn, to will be the zero address, which will have a balance of 0
+        uint256 toBalance = token.balanceOf(to);
+
+        emit TokensToSendCalled(
+            operator,
+            from,
+            to,
+            amount,
+            userData,
+            operatorData,
+            address(token),
+            fromBalance,
+            toBalance
+        );
+    }
+
+    function tokensReceived(
+        address operator,
+        address from,
+        address to,
+        uint amount,
+        bytes calldata userData,
+        bytes calldata operatorData
+    ) external{
+        if (_shouldRevertReceive) {
+            revert();
+        }
+
+        IERC777 token = IERC777(msg.sender);
+
+        uint256 fromBalance = token.balanceOf(from);
+        // when called due to burn, to will be the zero address, which will have a balance of 0
+        uint256 toBalance = token.balanceOf(to);
+
+        emit TokensReceivedCalled(
+            operator,
+            from,
+            to,
+            amount,
+            userData,
+            operatorData,
+            address(token),
+            fromBalance,
+            toBalance
+        );
+    }
+
+    function senderFor(address account) public {
+        _registerInterfaceForAddress(TOKENS_SENDER_INTERFACE_HASH, account);
+
+        address self = address(this);
+        if (account == self) {
+            registerSender(self);
+        }
+    }
+
+    function registerSender(address sender) public {
+        _erc1820.setInterfaceImplementer(address(this), TOKENS_SENDER_INTERFACE_HASH, sender);
+    }
+
+    function recipientFor(address account) public {
+        _registerInterfaceForAddress(TOKENS_RECIPIENT_INTERFACE_HASH, account);
+
+        address self = address(this);
+        if (account == self) {
+            registerRecipient(self);
+        }
+    }
+
+    function registerRecipient(address recipient) public {
+        _erc1820.setInterfaceImplementer(address(this), TOKENS_RECIPIENT_INTERFACE_HASH, recipient);
+    }
+
+    function setShouldRevertSend(bool shouldRevert) public {
+        _shouldRevertSend = shouldRevert;
+    }
+
+    function setShouldRevertReceive(bool shouldRevert) public {
+        _shouldRevertReceive = shouldRevert;
+    }
+
+    function send(IERC777 token, address to, uint256 amount, bytes memory data) public {
+        // This is 777's send function, not the Solidity send function
+        token.send(to, amount, data); // solhint-disable-line check-send-result
+    }
+
+    function burn(IERC777 token, uint256 amount, bytes memory data) public {
+        token.burn(amount, data);
+    }
+}
+

contracts/mocks/EventEmitter.sol

@@ -1,73 +0,0 @@
-pragma solidity ^0.5.2;
-
-contract EventEmitter {
-    event Argumentless();
-    event ShortUint(uint8 value);
-    event ShortInt(int8 value);
-    event LongUint(uint256 value);
-    event LongInt(int256 value);
-    event Address(address value);
-    event Boolean(bool value);
-    event String(string value);
-    event LongUintBooleanString(uint256 uintValue, bool booleanValue, string stringValue);
-
-    constructor (uint8 uintValue, bool booleanValue, string memory stringValue) public {
-        emit ShortUint(uintValue);
-        emit Boolean(booleanValue);
-        emit String(stringValue);
-    }
-
-    function emitArgumentless() public {
-        emit Argumentless();
-    }
-
-    function emitShortUint(uint8 value) public {
-        emit ShortUint(value);
-    }
-
-    function emitShortInt(int8 value) public {
-        emit ShortInt(value);
-    }
-
-    function emitLongUint(uint256 value) public {
-        emit LongUint(value);
-    }
-
-    function emitLongInt(int256 value) public {
-        emit LongInt(value);
-    }
-
-    function emitAddress(address value) public {
-        emit Address(value);
-    }
-
-    function emitBoolean(bool value) public {
-        emit Boolean(value);
-    }
-
-    function emitString(string memory value) public {
-        emit String(value);
-    }
-
-    function emitLongUintBooleanString(uint256 uintValue, bool booleanValue, string memory stringValue) public {
-        emit LongUintBooleanString(uintValue, booleanValue, stringValue);
-    }
-
-    function emitLongUintAndBoolean(uint256 uintValue, bool boolValue) public {
-        emit LongUint(uintValue);
-        emit Boolean(boolValue);
-    }
-
-    function emitStringAndEmitIndirectly(string memory value, IndirectEventEmitter emitter) public {
-        emit String(value);
-        emitter.emitStringIndirectly(value);
-    }
-}
-
-contract IndirectEventEmitter {
-    event IndirectString(string value);
-
-    function emitStringIndirectly(string memory value) public {
-        emit IndirectString(value);
-    }
-}

contracts/mocks/Failer.sol

@@ -1,23 +0,0 @@
-pragma solidity ^0.5.2;
-
-contract Failer {
-    uint256[] private array;
-
-    function dontFail() public pure {
-        // solhint-disable-previous-line no-empty-blocks
-    }
-
-    function failWithRevert() public pure {
-        revert();
-    }
-
-    function failWithThrow() public pure {
-        assert(false);
-    }
-
-    function failWithOutOfGas() public {
-        for (uint256 i = 0; i < 2**200; ++i) {
-            array.push(i);
-        }
-    }
-}

contracts/mocks/FinalizableCrowdsaleImpl.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../token/ERC20/IERC20.sol";
 import "../crowdsale/distribution/FinalizableCrowdsale.sol";

contracts/mocks/IncreasingPriceCrowdsaleImpl.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../crowdsale/price/IncreasingPriceCrowdsale.sol";
 import "../math/SafeMath.sol";

contracts/mocks/IndividuallyCappedCrowdsaleImpl.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../token/ERC20/IERC20.sol";
 import "../crowdsale/validation/IndividuallyCappedCrowdsale.sol";

contracts/mocks/MathMock.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../math/Math.sol";
 

contracts/mocks/MerkleProofWrapper.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import { MerkleProof } from "../cryptography/MerkleProof.sol";
 

contracts/mocks/MintedCrowdsaleImpl.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../token/ERC20/ERC20Mintable.sol";
 import "../crowdsale/emission/MintedCrowdsale.sol";

contracts/mocks/MinterRoleMock.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../access/roles/MinterRole.sol";
 

contracts/mocks/OwnableInterfaceId.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../ownership/Ownable.sol";
 

contracts/mocks/OwnableMock.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../ownership/Ownable.sol";
 

contracts/mocks/PausableCrowdsaleImpl.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../token/ERC20/ERC20.sol";
 import "../crowdsale/validation/PausableCrowdsale.sol";

contracts/mocks/PausableMock.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../lifecycle/Pausable.sol";
 import "./PauserRoleMock.sol";

contracts/mocks/PauserRoleMock.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../access/roles/PauserRole.sol";
 

contracts/mocks/PostDeliveryCrowdsaleImpl.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../token/ERC20/IERC20.sol";
 import "../crowdsale/distribution/PostDeliveryCrowdsale.sol";

contracts/mocks/PullPaymentMock.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../payment/PullPayment.sol";