Migrate Contracts to Solidity v0.6 (#2080)

* Initial migration to Solidity 0.6.x - v3.0 first steps (#2063)

* Initial migration, missing GSN, 721, 777 and Crowdsales.

* Add _beforeTokenOperation and _afterTokenOperation.

* Add documentation for hooks.

* Add hooks doc

* Add missing drafts

* Add back ERC721 with hooks

* Bring back ERC777

* Notes on hooks

* Bring back GSN

* Make functions virtual

* Make GSN overrides explicit

* Fix ERC20Pausable tests

* Remove virtual from some view functions

* Update linter

* Delete examples

* Remove unnecessary virtual

* Remove roles from Pausable

* Remove roles

* Remove users of roles

* Adapt ERC20 tests

* Fix ERC721 tests

* Add all ERC721 hooks

* Add ERC777 hooks

* Fix remaining tests

* Bump compiler version

* Move 721BurnableMock into mocks directory

* Remove _before hooks

* Fix tests

* Upgrade linter

* Put modifiers last

* Remove _beforeTokenApproval and _beforeOperatorApproval hooks

.solhint.json

@@ -1,14 +1,9 @@
 {
   "extends": "solhint:recommended",
   "rules": {
-    "indent": ["error", 4],
     "func-order": "off",
-    "bracket-align": "off",
-    "compiler-fixed": "off",
-    "no-simple-event-func-name": "off",
-    "separate-by-one-line-in-contract": "off",
-    "two-lines-top-level-separator": "off",
     "mark-callable-contracts": "off",
-    "compiler-version": ["error", "^0.5.0"]
+    "no-empty-blocks": "off",
+    "compiler-version": ["error", "^0.6.0"]
   }
 }

contracts/GSN/Context.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 /*
  * @dev Provides information about the current execution context, including the
@@ -14,13 +14,12 @@ contract Context {
     // Empty internal constructor, to prevent people from mistakenly deploying
     // an instance of this contract, which should be used via inheritance.
     constructor () internal { }
-    // solhint-disable-previous-line no-empty-blocks
 
-    function _msgSender() internal view returns (address payable) {
+    function _msgSender() internal view virtual returns (address payable) {
         return msg.sender;
     }
 
-    function _msgData() internal view returns (bytes memory) {
+    function _msgData() internal view virtual returns (bytes memory) {
         this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
         return msg.data;
     }

contracts/GSN/GSNRecipient.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 import "./IRelayRecipient.sol";
 import "./IRelayHub.sol";
@@ -15,7 +15,7 @@ import "./Context.sol";
  * information on how to use the pre-built {GSNRecipientSignature} and
  * {GSNRecipientERC20Fee}, or how to write your own.
  */
-contract GSNRecipient is IRelayRecipient, Context {
+abstract contract GSNRecipient is IRelayRecipient, Context {
     // Default RelayHub address, deployed on mainnet and all testnets at the same address
     address private _relayHub = 0xD216153c06E857cD7f72665E0aF1d7D82172F494;
 
@@ -33,7 +33,7 @@ contract GSNRecipient is IRelayRecipient, Context {
     /**
      * @dev Returns the address of the {IRelayHub} contract for this recipient.
      */
-    function getHubAddr() public view returns (address) {
+    function getHubAddr() public view override returns (address) {
         return _relayHub;
     }
 
@@ -44,7 +44,7 @@ contract GSNRecipient is IRelayRecipient, Context {
      * 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 {
+    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");
@@ -70,7 +70,7 @@ contract GSNRecipient is IRelayRecipient, Context {
      *
      * Derived contracts should expose this in an external interface with proper access control.
      */
-    function _withdrawDeposits(uint256 amount, address payable payee) internal {
+    function _withdrawDeposits(uint256 amount, address payable payee) internal virtual {
         IRelayHub(_relayHub).withdraw(amount, payee);
     }
 
@@ -85,7 +85,7 @@ contract GSNRecipient is IRelayRecipient, Context {
      *
      * IMPORTANT: Contracts derived from {GSNRecipient} should never use `msg.sender`, and use {_msgSender} instead.
      */
-    function _msgSender() internal view returns (address payable) {
+    function _msgSender() internal view virtual override returns (address payable) {
         if (msg.sender != _relayHub) {
             return msg.sender;
         } else {
@@ -99,7 +99,7 @@ contract GSNRecipient is IRelayRecipient, Context {
      *
      * IMPORTANT: Contracts derived from {GSNRecipient} should never use `msg.data`, and use {_msgData} instead.
      */
-    function _msgData() internal view returns (bytes memory) {
+    function _msgData() internal view virtual override returns (bytes memory) {
         if (msg.sender != _relayHub) {
             return msg.data;
         } else {
@@ -119,7 +119,7 @@ contract GSNRecipient is IRelayRecipient, Context {
      *
      * - the caller must be the `RelayHub` contract.
      */
-    function preRelayedCall(bytes calldata context) external returns (bytes32) {
+    function preRelayedCall(bytes calldata context) external virtual override returns (bytes32) {
         require(msg.sender == getHubAddr(), "GSNRecipient: caller is not RelayHub");
         return _preRelayedCall(context);
     }
@@ -131,7 +131,7 @@ contract GSNRecipient is IRelayRecipient, Context {
      * must implement this function with any relayed-call preprocessing they may wish to do.
      *
      */
-    function _preRelayedCall(bytes memory context) internal returns (bytes32);
+    function _preRelayedCall(bytes memory context) internal virtual returns (bytes32);
 
     /**
      * @dev See `IRelayRecipient.postRelayedCall`.
@@ -142,7 +142,7 @@ contract GSNRecipient is IRelayRecipient, Context {
      *
      * - the caller must be the `RelayHub` contract.
      */
-    function postRelayedCall(bytes calldata context, bool success, uint256 actualCharge, bytes32 preRetVal) external {
+    function postRelayedCall(bytes calldata context, bool success, uint256 actualCharge, bytes32 preRetVal) external virtual override {
         require(msg.sender == getHubAddr(), "GSNRecipient: caller is not RelayHub");
         _postRelayedCall(context, success, actualCharge, preRetVal);
     }
@@ -154,7 +154,7 @@ contract GSNRecipient is IRelayRecipient, Context {
      * 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;
+    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

contracts/GSN/GSNRecipientERC20Fee.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 import "./GSNRecipient.sol";
 import "../math/SafeMath.sol";
@@ -43,7 +43,7 @@ contract GSNRecipientERC20Fee is GSNRecipient {
     /**
      * @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 {
+    function _mint(address account, uint256 amount) internal virtual {
         _token.mint(account, amount);
     }
 
@@ -63,6 +63,8 @@ contract GSNRecipientERC20Fee is GSNRecipient {
     )
         external
         view
+        virtual
+        override
         returns (uint256, bytes memory)
     {
         if (_token.balanceOf(from) < maxPossibleCharge) {
@@ -78,7 +80,7 @@ contract GSNRecipientERC20Fee is GSNRecipient {
      * 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 returns (bytes32) {
+    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
@@ -88,7 +90,7 @@ contract GSNRecipientERC20Fee is GSNRecipient {
     /**
      * @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 {
+    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));
 
@@ -113,9 +115,7 @@ contract GSNRecipientERC20Fee is GSNRecipient {
 contract __unstable__ERC20PrimaryAdmin is ERC20, ERC20Detailed, Secondary {
     uint256 private constant UINT256_MAX = 2**256 - 1;
 
-    constructor(string memory name, string memory symbol, uint8 decimals) public ERC20Detailed(name, symbol, decimals) {
-        // solhint-disable-previous-line no-empty-blocks
-    }
+    constructor(string memory name, string memory symbol, uint8 decimals) public ERC20Detailed(name, symbol, decimals) { }
 
     // The primary account (GSNRecipientERC20Fee) can mint tokens
     function mint(address account, uint256 amount) public onlyPrimary {
@@ -123,7 +123,7 @@ contract __unstable__ERC20PrimaryAdmin is ERC20, ERC20Detailed, Secondary {
     }
 
     // The primary account has 'infinite' allowance for all token holders
-    function allowance(address owner, address spender) public view returns (uint256) {
+    function allowance(address owner, address spender) public view override(ERC20, IERC20) returns (uint256) {
         if (spender == primary()) {
             return UINT256_MAX;
         } else {
@@ -132,7 +132,7 @@ contract __unstable__ERC20PrimaryAdmin is ERC20, ERC20Detailed, Secondary {
     }
 
     // Allowance for the primary account cannot be changed (it is always 'infinite')
-    function _approve(address owner, address spender, uint256 value) internal {
+    function _approve(address owner, address spender, uint256 value) internal override {
         if (spender == primary()) {
             return;
         } else {
@@ -140,7 +140,7 @@ contract __unstable__ERC20PrimaryAdmin is ERC20, ERC20Detailed, Secondary {
         }
     }
 
-    function transferFrom(address sender, address recipient, uint256 amount) public returns (bool) {
+    function transferFrom(address sender, address recipient, uint256 amount) public override(ERC20, IERC20) returns (bool) {
         if (recipient == primary()) {
             _transfer(sender, recipient, amount);
             return true;

contracts/GSN/GSNRecipientSignature.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 import "./GSNRecipient.sol";
 import "../cryptography/ECDSA.sol";
@@ -42,6 +42,8 @@ contract GSNRecipientSignature is GSNRecipient {
     )
         external
         view
+        virtual
+        override
         returns (uint256, bytes memory)
     {
         bytes memory blob = abi.encodePacked(
@@ -62,11 +64,7 @@ contract GSNRecipientSignature is GSNRecipient {
         }
     }
 
-    function _preRelayedCall(bytes memory) internal returns (bytes32) {
-        // solhint-disable-previous-line no-empty-blocks
-    }
+    function _preRelayedCall(bytes memory) internal virtual override returns (bytes32) { }
 
-    function _postRelayedCall(bytes memory, bool, uint256, bytes32) internal {
-        // solhint-disable-previous-line no-empty-blocks
-    }
+    function _postRelayedCall(bytes memory, bool, uint256, bytes32) internal virtual override { }
 }

contracts/GSN/IRelayHub.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 /**
  * @dev Interface for `RelayHub`, the core contract of the GSN. Users should not need to interact with this contract
@@ -207,7 +207,7 @@ interface IRelayHub {
     event CanRelayFailed(address indexed relay, address indexed from, address indexed to, bytes4 selector, uint256 reason);
 
     /**
-     * @dev Emitted when a transaction is relayed. 
+     * @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.
@@ -236,7 +236,7 @@ interface IRelayHub {
      */
     function maxPossibleCharge(uint256 relayedCallStipend, uint256 gasPrice, uint256 transactionFee) external view returns (uint256);
 
-     // Relay penalization. 
+     // 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.

contracts/GSN/IRelayRecipient.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 /**
  * @dev Base interface for a contract that will be called via the GSN from {IRelayHub}.

contracts/access/README.adoc

@@ -5,17 +5,3 @@ NOTE: This page is incomplete. We're working to improve it for the next release.
 == Library
 
 {{Roles}}
-
-== Roles
-
-{{CapperRole}}
-
-{{MinterRole}}
-
-{{PauserRole}}
-
-{{SignerRole}}
-
-{{WhitelistAdminRole}}
-
-{{WhitelistedRole}}

contracts/access/Roles.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 /**
  * @title Roles

contracts/access/roles/CapperRole.sol

@@ -1,44 +0,0 @@
-pragma solidity ^0.5.0;
-
-import "../../GSN/Context.sol";
-import "../Roles.sol";
-
-contract CapperRole is Context {
-    using Roles for Roles.Role;
-
-    event CapperAdded(address indexed account);
-    event CapperRemoved(address indexed account);
-
-    Roles.Role private _cappers;
-
-    constructor () internal {
-        _addCapper(_msgSender());
-    }
-
-    modifier onlyCapper() {
-        require(isCapper(_msgSender()), "CapperRole: caller does not have the Capper role");
-        _;
-    }
-
-    function isCapper(address account) public view returns (bool) {
-        return _cappers.has(account);
-    }
-
-    function addCapper(address account) public onlyCapper {
-        _addCapper(account);
-    }
-
-    function renounceCapper() public {
-        _removeCapper(_msgSender());
-    }
-
-    function _addCapper(address account) internal {
-        _cappers.add(account);
-        emit CapperAdded(account);
-    }
-
-    function _removeCapper(address account) internal {
-        _cappers.remove(account);
-        emit CapperRemoved(account);
-    }
-}

contracts/access/roles/MinterRole.sol

@@ -1,44 +0,0 @@
-pragma solidity ^0.5.0;
-
-import "../../GSN/Context.sol";
-import "../Roles.sol";
-
-contract MinterRole is Context {
-    using Roles for Roles.Role;
-
-    event MinterAdded(address indexed account);
-    event MinterRemoved(address indexed account);
-
-    Roles.Role private _minters;
-
-    constructor () internal {
-        _addMinter(_msgSender());
-    }
-
-    modifier onlyMinter() {
-        require(isMinter(_msgSender()), "MinterRole: caller does not have the Minter role");
-        _;
-    }
-
-    function isMinter(address account) public view returns (bool) {
-        return _minters.has(account);
-    }
-
-    function addMinter(address account) public onlyMinter {
-        _addMinter(account);
-    }
-
-    function renounceMinter() public {
-        _removeMinter(_msgSender());
-    }
-
-    function _addMinter(address account) internal {
-        _minters.add(account);
-        emit MinterAdded(account);
-    }
-
-    function _removeMinter(address account) internal {
-        _minters.remove(account);
-        emit MinterRemoved(account);
-    }
-}

contracts/access/roles/PauserRole.sol

@@ -1,44 +0,0 @@
-pragma solidity ^0.5.0;
-
-import "../../GSN/Context.sol";
-import "../Roles.sol";
-
-contract PauserRole is Context {
-    using Roles for Roles.Role;
-
-    event PauserAdded(address indexed account);
-    event PauserRemoved(address indexed account);
-
-    Roles.Role private _pausers;
-
-    constructor () internal {
-        _addPauser(_msgSender());
-    }
-
-    modifier onlyPauser() {
-        require(isPauser(_msgSender()), "PauserRole: caller does not have the Pauser role");
-        _;
-    }
-
-    function isPauser(address account) public view returns (bool) {
-        return _pausers.has(account);
-    }
-
-    function addPauser(address account) public onlyPauser {
-        _addPauser(account);
-    }
-
-    function renouncePauser() public {
-        _removePauser(_msgSender());
-    }
-
-    function _addPauser(address account) internal {
-        _pausers.add(account);
-        emit PauserAdded(account);
-    }
-
-    function _removePauser(address account) internal {
-        _pausers.remove(account);
-        emit PauserRemoved(account);
-    }
-}

contracts/access/roles/SignerRole.sol

@@ -1,44 +0,0 @@
-pragma solidity ^0.5.0;
-
-import "../../GSN/Context.sol";
-import "../Roles.sol";
-
-contract SignerRole is Context {
-    using Roles for Roles.Role;
-
-    event SignerAdded(address indexed account);
-    event SignerRemoved(address indexed account);
-
-    Roles.Role private _signers;
-
-    constructor () internal {
-        _addSigner(_msgSender());
-    }
-
-    modifier onlySigner() {
-        require(isSigner(_msgSender()), "SignerRole: caller does not have the Signer role");
-        _;
-    }
-
-    function isSigner(address account) public view returns (bool) {
-        return _signers.has(account);
-    }
-
-    function addSigner(address account) public onlySigner {
-        _addSigner(account);
-    }
-
-    function renounceSigner() public {
-        _removeSigner(_msgSender());
-    }
-
-    function _addSigner(address account) internal {
-        _signers.add(account);
-        emit SignerAdded(account);
-    }
-
-    function _removeSigner(address account) internal {
-        _signers.remove(account);
-        emit SignerRemoved(account);
-    }
-}

contracts/access/roles/WhitelistAdminRole.sol

@@ -1,48 +0,0 @@
-pragma solidity ^0.5.0;
-
-import "../../GSN/Context.sol";
-import "../Roles.sol";
-
-/**
- * @title WhitelistAdminRole
- * @dev WhitelistAdmins are responsible for assigning and removing Whitelisted accounts.
- */
-contract WhitelistAdminRole is Context {
-    using Roles for Roles.Role;
-
-    event WhitelistAdminAdded(address indexed account);
-    event WhitelistAdminRemoved(address indexed account);
-
-    Roles.Role private _whitelistAdmins;
-
-    constructor () internal {
-        _addWhitelistAdmin(_msgSender());
-    }
-
-    modifier onlyWhitelistAdmin() {
-        require(isWhitelistAdmin(_msgSender()), "WhitelistAdminRole: caller does not have the WhitelistAdmin role");
-        _;
-    }
-
-    function isWhitelistAdmin(address account) public view returns (bool) {
-        return _whitelistAdmins.has(account);
-    }
-
-    function addWhitelistAdmin(address account) public onlyWhitelistAdmin {
-        _addWhitelistAdmin(account);
-    }
-
-    function renounceWhitelistAdmin() public {
-        _removeWhitelistAdmin(_msgSender());
-    }
-
-    function _addWhitelistAdmin(address account) internal {
-        _whitelistAdmins.add(account);
-        emit WhitelistAdminAdded(account);
-    }
-
-    function _removeWhitelistAdmin(address account) internal {
-        _whitelistAdmins.remove(account);
-        emit WhitelistAdminRemoved(account);
-    }
-}

contracts/access/roles/WhitelistedRole.sol

@@ -1,51 +0,0 @@
-pragma solidity ^0.5.0;
-
-import "../../GSN/Context.sol";
-import "../Roles.sol";
-import "./WhitelistAdminRole.sol";
-
-/**
- * @title WhitelistedRole
- * @dev Whitelisted accounts have been approved by a WhitelistAdmin to perform certain actions (e.g. participate in a
- * crowdsale). This role is special in that the only accounts that can add it are WhitelistAdmins (who can also remove
- * it), and not Whitelisteds themselves.
- */
-contract WhitelistedRole is Context, WhitelistAdminRole {
-    using Roles for Roles.Role;
-
-    event WhitelistedAdded(address indexed account);
-    event WhitelistedRemoved(address indexed account);
-
-    Roles.Role private _whitelisteds;
-
-    modifier onlyWhitelisted() {
-        require(isWhitelisted(_msgSender()), "WhitelistedRole: caller does not have the Whitelisted role");
-        _;
-    }
-
-    function isWhitelisted(address account) public view returns (bool) {
-        return _whitelisteds.has(account);
-    }
-
-    function addWhitelisted(address account) public onlyWhitelistAdmin {
-        _addWhitelisted(account);
-    }
-
-    function removeWhitelisted(address account) public onlyWhitelistAdmin {
-        _removeWhitelisted(account);
-    }
-
-    function renounceWhitelisted() public {
-        _removeWhitelisted(_msgSender());
-    }
-
-    function _addWhitelisted(address account) internal {
-        _whitelisteds.add(account);
-        emit WhitelistedAdded(account);
-    }
-
-    function _removeWhitelisted(address account) internal {
-        _whitelisteds.remove(account);
-        emit WhitelistedRemoved(account);
-    }
-}

contracts/crowdsale/Crowdsale.sol

@@ -1,200 +0,0 @@
-pragma solidity ^0.5.0;
-
-import "../GSN/Context.sol";
-import "../token/ERC20/IERC20.sol";
-import "../math/SafeMath.sol";
-import "../token/ERC20/SafeERC20.sol";
-import "../utils/ReentrancyGuard.sol";
-
-/**
- * @title Crowdsale
- * @dev Crowdsale is a base contract for managing a token crowdsale,
- * allowing investors to purchase tokens with ether. This contract implements
- * such functionality in its most fundamental form and can be extended to provide additional
- * functionality and/or custom behavior.
- * The external interface represents the basic interface for purchasing tokens, and conforms
- * the base architecture for crowdsales. It is *not* intended to be modified / overridden.
- * The internal interface conforms the extensible and modifiable surface of crowdsales. Override
- * the methods to add functionality. Consider using 'super' where appropriate to concatenate
- * behavior.
- */
-contract Crowdsale is Context, ReentrancyGuard {
-    using SafeMath for uint256;
-    using SafeERC20 for IERC20;
-
-    // The token being sold
-    IERC20 private _token;
-
-    // Address where funds are collected
-    address payable private _wallet;
-
-    // How many token units a buyer gets per wei.
-    // The rate is the conversion between wei and the smallest and indivisible token unit.
-    // So, if you are using a rate of 1 with a ERC20Detailed token with 3 decimals called TOK
-    // 1 wei will give you 1 unit, or 0.001 TOK.
-    uint256 private _rate;
-
-    // Amount of wei raised
-    uint256 private _weiRaised;
-
-    /**
-     * Event for token purchase logging
-     * @param purchaser who paid for the tokens
-     * @param beneficiary who got the tokens
-     * @param value weis paid for purchase
-     * @param amount amount of tokens purchased
-     */
-    event TokensPurchased(address indexed purchaser, address indexed beneficiary, uint256 value, uint256 amount);
-
-    /**
-     * @param rate Number of token units a buyer gets per wei
-     * @dev The rate is the conversion between wei and the smallest and indivisible
-     * token unit. So, if you are using a rate of 1 with a ERC20Detailed token
-     * with 3 decimals called TOK, 1 wei will give you 1 unit, or 0.001 TOK.
-     * @param wallet Address where collected funds will be forwarded to
-     * @param token Address of the token being sold
-     */
-    constructor (uint256 rate, address payable wallet, IERC20 token) public {
-        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;
-        _token = token;
-    }
-
-    /**
-     * @dev fallback function ***DO NOT OVERRIDE***
-     * Note that other contracts will transfer funds with a base gas stipend
-     * of 2300, which is not enough to call buyTokens. Consider calling
-     * buyTokens directly when purchasing tokens from a contract.
-     */
-    function () external payable {
-        buyTokens(_msgSender());
-    }
-
-    /**
-     * @return the token being sold.
-     */
-    function token() public view returns (IERC20) {
-        return _token;
-    }
-
-    /**
-     * @return the address where funds are collected.
-     */
-    function wallet() public view returns (address payable) {
-        return _wallet;
-    }
-
-    /**
-     * @return the number of token units a buyer gets per wei.
-     */
-    function rate() public view returns (uint256) {
-        return _rate;
-    }
-
-    /**
-     * @return the amount of wei raised.
-     */
-    function weiRaised() public view returns (uint256) {
-        return _weiRaised;
-    }
-
-    /**
-     * @dev low level token purchase ***DO NOT OVERRIDE***
-     * This function has a non-reentrancy guard, so it shouldn't be called by
-     * another `nonReentrant` function.
-     * @param beneficiary Recipient of the token purchase
-     */
-    function buyTokens(address beneficiary) public nonReentrant payable {
-        uint256 weiAmount = msg.value;
-        _preValidatePurchase(beneficiary, weiAmount);
-
-        // calculate token amount to be created
-        uint256 tokens = _getTokenAmount(weiAmount);
-
-        // update state
-        _weiRaised = _weiRaised.add(weiAmount);
-
-        _processPurchase(beneficiary, tokens);
-        emit TokensPurchased(_msgSender(), beneficiary, weiAmount, tokens);
-
-        _updatePurchasingState(beneficiary, weiAmount);
-
-        _forwardFunds();
-        _postValidatePurchase(beneficiary, weiAmount);
-    }
-
-    /**
-     * @dev Validation of an incoming purchase. Use require statements to revert state when conditions are not met.
-     * Use `super` in contracts that inherit from Crowdsale to extend their validations.
-     * Example from CappedCrowdsale.sol's _preValidatePurchase method:
-     *     super._preValidatePurchase(beneficiary, weiAmount);
-     *     require(weiRaised().add(weiAmount) <= cap);
-     * @param beneficiary Address performing the token purchase
-     * @param weiAmount Value in wei involved in the purchase
-     */
-    function _preValidatePurchase(address beneficiary, uint256 weiAmount) internal view {
-        require(beneficiary != address(0), "Crowdsale: beneficiary is the zero address");
-        require(weiAmount != 0, "Crowdsale: weiAmount is 0");
-        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
-    }
-
-    /**
-     * @dev Validation of an executed purchase. Observe state and use revert statements to undo rollback when valid
-     * conditions are not met.
-     * @param beneficiary Address performing the token purchase
-     * @param weiAmount Value in wei involved in the purchase
-     */
-    function _postValidatePurchase(address beneficiary, uint256 weiAmount) internal view {
-        // solhint-disable-previous-line no-empty-blocks
-    }
-
-    /**
-     * @dev Source of tokens. Override this method to modify the way in which the crowdsale ultimately gets and sends
-     * its tokens.
-     * @param beneficiary Address performing the token purchase
-     * @param tokenAmount Number of tokens to be emitted
-     */
-    function _deliverTokens(address beneficiary, uint256 tokenAmount) internal {
-        _token.safeTransfer(beneficiary, tokenAmount);
-    }
-
-    /**
-     * @dev Executed when a purchase has been validated and is ready to be executed. Doesn't necessarily emit/send
-     * tokens.
-     * @param beneficiary Address receiving the tokens
-     * @param tokenAmount Number of tokens to be purchased
-     */
-    function _processPurchase(address beneficiary, uint256 tokenAmount) internal {
-        _deliverTokens(beneficiary, tokenAmount);
-    }
-
-    /**
-     * @dev Override for extensions that require an internal state to check for validity (current user contributions,
-     * etc.)
-     * @param beneficiary Address receiving the tokens
-     * @param weiAmount Value in wei involved in the purchase
-     */
-    function _updatePurchasingState(address beneficiary, uint256 weiAmount) internal {
-        // solhint-disable-previous-line no-empty-blocks
-    }
-
-    /**
-     * @dev Override to extend the way in which ether is converted to tokens.
-     * @param weiAmount Value in wei to be converted into tokens
-     * @return Number of tokens that can be purchased with the specified _weiAmount
-     */
-    function _getTokenAmount(uint256 weiAmount) internal view returns (uint256) {
-        return weiAmount.mul(_rate);
-    }
-
-    /**
-     * @dev Determines how ETH is stored/forwarded on purchases.
-     */
-    function _forwardFunds() internal {
-        _wallet.transfer(msg.value);
-    }
-}

contracts/crowdsale/README.adoc

@@ -1,35 +0,0 @@
-= Crowdsales
-
-NOTE: This page is incomplete. We're working to improve it for the next release. Stay tuned!
-
-== Core
-
-{{Crowdsale}}
-
-== Emission
-
-{{AllowanceCrowdsale}}
-
-{{MintedCrowdsale}}
-
-== Validation
-
-{{CappedCrowdsale}}
-
-{{IndividuallyCappedCrowdsale}}
-
-{{PausableCrowdsale}}
-
-{{TimedCrowdsale}}
-
-{{WhitelistCrowdsale}}
-
-== Distribution
-
-{{FinalizableCrowdsale}}
-
-{{PostDeliveryCrowdsale}}
-
-{{RefundableCrowdsale}}
-
-{{RefundablePostDeliveryCrowdsale}}

contracts/crowdsale/distribution/FinalizableCrowdsale.sol

@@ -1,51 +0,0 @@
-pragma solidity ^0.5.0;
-
-import "../../math/SafeMath.sol";
-import "../validation/TimedCrowdsale.sol";
-
-/**
- * @title FinalizableCrowdsale
- * @dev Extension of TimedCrowdsale with a one-off finalization action, where one
- * can do extra work after finishing.
- */
-contract FinalizableCrowdsale is TimedCrowdsale {
-    using SafeMath for uint256;
-
-    bool private _finalized;
-
-    event CrowdsaleFinalized();
-
-    constructor () internal {
-        _finalized = false;
-    }
-
-    /**
-     * @return true if the crowdsale is finalized, false otherwise.
-     */
-    function finalized() public view returns (bool) {
-        return _finalized;
-    }
-
-    /**
-     * @dev Must be called after crowdsale ends, to do some extra finalization
-     * work. Calls the contract's finalization function.
-     */
-    function finalize() public {
-        require(!_finalized, "FinalizableCrowdsale: already finalized");
-        require(hasClosed(), "FinalizableCrowdsale: not closed");
-
-        _finalized = true;
-
-        _finalization();
-        emit CrowdsaleFinalized();
-    }
-
-    /**
-     * @dev Can be overridden to add finalization logic. The overriding function
-     * should call super._finalization() to ensure the chain of finalization is
-     * executed entirely.
-     */
-    function _finalization() internal {
-        // solhint-disable-previous-line no-empty-blocks
-    }
-}

contracts/crowdsale/distribution/PostDeliveryCrowdsale.sol

@@ -1,65 +0,0 @@
-pragma solidity ^0.5.0;
-
-import "../validation/TimedCrowdsale.sol";
-import "../../math/SafeMath.sol";
-import "../../ownership/Secondary.sol";
-import "../../token/ERC20/IERC20.sol";
-
-/**
- * @title PostDeliveryCrowdsale
- * @dev Crowdsale that locks tokens from withdrawal until it ends.
- */
-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(), "PostDeliveryCrowdsale: not closed");
-        uint256 amount = _balances[beneficiary];
-        require(amount > 0, "PostDeliveryCrowdsale: beneficiary is not due any tokens");
-
-        _balances[beneficiary] = 0;
-        _vault.transfer(token(), beneficiary, amount);
-    }
-
-    /**
-     * @return the balance of an account.
-     */
-    function balanceOf(address account) public view returns (uint256) {
-        return _balances[account];
-    }
-
-    /**
-     * @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

@@ -1,83 +0,0 @@
-pragma solidity ^0.5.0;
-
-import "../../GSN/Context.sol";
-import "../../math/SafeMath.sol";
-import "./FinalizableCrowdsale.sol";
-import "../../payment/escrow/RefundEscrow.sol";
-
-/**
- * @title RefundableCrowdsale
- * @dev Extension of `FinalizableCrowdsale` contract that adds a funding goal, and the possibility of users
- * getting a refund if goal is not met.
- *
- * Deprecated, use `RefundablePostDeliveryCrowdsale` instead. Note that if you allow tokens to be traded before the goal
- * is met, then an attack is possible in which the attacker purchases tokens from the crowdsale and when they sees that
- * the goal is unlikely to be met, they sell their tokens (possibly at a discount). The attacker will be refunded when
- * the crowdsale is finalized, and the users that purchased from them will be left with worthless tokens.
- */
-contract RefundableCrowdsale is Context, FinalizableCrowdsale {
-    using SafeMath for uint256;
-
-    // minimum amount of funds to be raised in weis
-    uint256 private _goal;
-
-    // refund escrow used to hold funds while crowdsale is running
-    RefundEscrow private _escrow;
-
-    /**
-     * @dev Constructor, creates RefundEscrow.
-     * @param goal Funding goal
-     */
-    constructor (uint256 goal) public {
-        require(goal > 0, "RefundableCrowdsale: goal is 0");
-        _escrow = new RefundEscrow(wallet());
-        _goal = goal;
-    }
-
-    /**
-     * @return minimum amount of funds to be raised in wei.
-     */
-    function goal() public view returns (uint256) {
-        return _goal;
-    }
-
-    /**
-     * @dev Investors can claim refunds here if crowdsale is unsuccessful.
-     * @param refundee Whose refund will be claimed.
-     */
-    function claimRefund(address payable refundee) public {
-        require(finalized(), "RefundableCrowdsale: not finalized");
-        require(!goalReached(), "RefundableCrowdsale: goal reached");
-
-        _escrow.withdraw(refundee);
-    }
-
-    /**
-     * @dev Checks whether funding goal was reached.
-     * @return Whether funding goal was reached
-     */
-    function goalReached() public view returns (bool) {
-        return weiRaised() >= _goal;
-    }
-
-    /**
-     * @dev Escrow finalization task, called when finalize() is called.
-     */
-    function _finalization() internal {
-        if (goalReached()) {
-            _escrow.close();
-            _escrow.beneficiaryWithdraw();
-        } else {
-            _escrow.enableRefunds();
-        }
-
-        super._finalization();
-    }
-
-    /**
-     * @dev Overrides Crowdsale fund forwarding, sending funds to escrow.
-     */
-    function _forwardFunds() internal {
-        _escrow.deposit.value(msg.value)(_msgSender());
-    }
-}

contracts/crowdsale/distribution/RefundablePostDeliveryCrowdsale.sol

@@ -1,20 +0,0 @@
-pragma solidity ^0.5.0;
-
-import "./RefundableCrowdsale.sol";
-import "./PostDeliveryCrowdsale.sol";
-
-
-/**
- * @title RefundablePostDeliveryCrowdsale
- * @dev Extension of RefundableCrowdsale contract that only delivers the tokens
- * once the crowdsale has closed and the goal met, preventing refunds to be issued
- * to token holders.
- */
-contract RefundablePostDeliveryCrowdsale is RefundableCrowdsale, PostDeliveryCrowdsale {
-    function withdrawTokens(address beneficiary) public {
-        require(finalized(), "RefundablePostDeliveryCrowdsale: not finalized");
-        require(goalReached(), "RefundablePostDeliveryCrowdsale: goal not reached");
-
-        super.withdrawTokens(beneficiary);
-    }
-}

contracts/crowdsale/emission/AllowanceCrowdsale.sol

@@ -1,51 +0,0 @@
-pragma solidity ^0.5.0;
-
-import "../Crowdsale.sol";
-import "../../token/ERC20/IERC20.sol";
-import "../../token/ERC20/SafeERC20.sol";
-import "../../math/SafeMath.sol";
-import "../../math/Math.sol";
-
-/**
- * @title AllowanceCrowdsale
- * @dev Extension of Crowdsale where tokens are held by a wallet, which approves an allowance to the crowdsale.
- */
-contract AllowanceCrowdsale is Crowdsale {
-    using SafeMath for uint256;
-    using SafeERC20 for IERC20;
-
-    address private _tokenWallet;
-
-    /**
-     * @dev Constructor, takes token wallet address.
-     * @param tokenWallet Address holding the tokens, which has approved allowance to the crowdsale.
-     */
-    constructor (address tokenWallet) public {
-        require(tokenWallet != address(0), "AllowanceCrowdsale: token wallet is the zero address");
-        _tokenWallet = tokenWallet;
-    }
-
-    /**
-     * @return the address of the wallet that will hold the tokens.
-     */
-    function tokenWallet() public view returns (address) {
-        return _tokenWallet;
-    }
-
-    /**
-     * @dev Checks the amount of tokens left in the allowance.
-     * @return Amount of tokens left in the allowance
-     */
-    function remainingTokens() public view returns (uint256) {
-        return Math.min(token().balanceOf(_tokenWallet), token().allowance(_tokenWallet, address(this)));
-    }
-
-    /**
-     * @dev Overrides parent behavior by transferring tokens from wallet.
-     * @param beneficiary Token purchaser
-     * @param tokenAmount Amount of tokens purchased
-     */
-    function _deliverTokens(address beneficiary, uint256 tokenAmount) internal {
-        token().safeTransferFrom(_tokenWallet, beneficiary, tokenAmount);
-    }
-}

contracts/crowdsale/emission/MintedCrowdsale.sol

@@ -1,24 +0,0 @@
-pragma solidity ^0.5.0;
-
-import "../Crowdsale.sol";
-import "../../token/ERC20/ERC20Mintable.sol";
-
-/**
- * @title MintedCrowdsale
- * @dev Extension of Crowdsale contract whose tokens are minted in each purchase.
- * Token ownership should be transferred to MintedCrowdsale for minting.
- */
-contract MintedCrowdsale is Crowdsale {
-    /**
-     * @dev Overrides delivery by minting tokens upon purchase.
-     * @param beneficiary Token purchaser
-     * @param tokenAmount Number of tokens to be minted
-     */
-    function _deliverTokens(address beneficiary, uint256 tokenAmount) internal {
-        // Potentially dangerous assumption about the type of the token.
-        require(
-            ERC20Mintable(address(token())).mint(beneficiary, tokenAmount),
-                "MintedCrowdsale: minting failed"
-        );
-    }
-}

contracts/crowdsale/price/IncreasingPriceCrowdsale.sol

@@ -1,79 +0,0 @@
-pragma solidity ^0.5.0;
-
-import "../validation/TimedCrowdsale.sol";
-import "../../math/SafeMath.sol";
-
-/**
- * @title IncreasingPriceCrowdsale
- * @dev Extension of Crowdsale contract that increases the price of tokens linearly in time.
- * Note that what should be provided to the constructor is the initial and final _rates_, that is,
- * the amount of tokens per wei contributed. Thus, the initial rate must be greater than the final rate.
- */
-contract IncreasingPriceCrowdsale is TimedCrowdsale {
-    using SafeMath for uint256;
-
-    uint256 private _initialRate;
-    uint256 private _finalRate;
-
-    /**
-     * @dev Constructor, takes initial and final rates of tokens received per wei contributed.
-     * @param initialRate Number of tokens a buyer gets per wei at the start of the crowdsale
-     * @param finalRate Number of tokens a buyer gets per wei at the end of the crowdsale
-     */
-    constructor (uint256 initialRate, uint256 finalRate) public {
-        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;
-    }
-
-    /**
-     * The base rate function is overridden to revert, since this crowdsale doesn't use it, and
-     * all calls to it are a mistake.
-     */
-    function rate() public view returns (uint256) {
-        revert("IncreasingPriceCrowdsale: rate() called");
-    }
-
-    /**
-     * @return the initial rate of the crowdsale.
-     */
-    function initialRate() public view returns (uint256) {
-        return _initialRate;
-    }
-
-    /**
-     * @return the final rate of the crowdsale.
-     */
-    function finalRate() public view returns (uint256) {
-        return _finalRate;
-    }
-
-    /**
-     * @dev Returns the rate of tokens per wei at the present time.
-     * Note that, as price _increases_ with time, the rate _decreases_.
-     * @return The number of tokens a buyer gets per wei at a given time
-     */
-    function getCurrentRate() public view returns (uint256) {
-        if (!isOpen()) {
-            return 0;
-        }
-
-        // solhint-disable-next-line not-rely-on-time
-        uint256 elapsedTime = block.timestamp.sub(openingTime());
-        uint256 timeRange = closingTime().sub(openingTime());
-        uint256 rateRange = _initialRate.sub(_finalRate);
-        return _initialRate.sub(elapsedTime.mul(rateRange).div(timeRange));
-    }
-
-    /**
-     * @dev Overrides parent method taking into account variable rate.
-     * @param weiAmount The value in wei to be converted into tokens
-     * @return The number of tokens _weiAmount wei will buy at present time
-     */
-    function _getTokenAmount(uint256 weiAmount) internal view returns (uint256) {
-        uint256 currentRate = getCurrentRate();
-        return currentRate.mul(weiAmount);
-    }
-}

contracts/crowdsale/validation/CappedCrowdsale.sol

@@ -1,48 +0,0 @@
-pragma solidity ^0.5.0;
-
-import "../../math/SafeMath.sol";
-import "../Crowdsale.sol";
-
-/**
- * @title CappedCrowdsale
- * @dev Crowdsale with a limit for total contributions.
- */
-contract CappedCrowdsale is Crowdsale {
-    using SafeMath for uint256;
-
-    uint256 private _cap;
-
-    /**
-     * @dev Constructor, takes maximum amount of wei accepted in the crowdsale.
-     * @param cap Max amount of wei to be contributed
-     */
-    constructor (uint256 cap) public {
-        require(cap > 0, "CappedCrowdsale: cap is 0");
-        _cap = cap;
-    }
-
-    /**
-     * @return the cap of the crowdsale.
-     */
-    function cap() public view returns (uint256) {
-        return _cap;
-    }
-
-    /**
-     * @dev Checks whether the cap has been reached.
-     * @return Whether the cap was reached
-     */
-    function capReached() public view returns (bool) {
-        return weiRaised() >= _cap;
-    }
-
-    /**
-     * @dev Extend parent behavior requiring purchase to respect the funding cap.
-     * @param beneficiary Token purchaser
-     * @param weiAmount Amount of wei contributed
-     */
-    function _preValidatePurchase(address beneficiary, uint256 weiAmount) internal view {
-        super._preValidatePurchase(beneficiary, weiAmount);
-        require(weiRaised().add(weiAmount) <= _cap, "CappedCrowdsale: cap exceeded");
-    }
-}

contracts/crowdsale/validation/IndividuallyCappedCrowdsale.sol

@@ -1,64 +0,0 @@
-pragma solidity ^0.5.0;
-
-import "../../math/SafeMath.sol";
-import "../Crowdsale.sol";
-import "../../access/roles/CapperRole.sol";
-
-/**
- * @title IndividuallyCappedCrowdsale
- * @dev Crowdsale with per-beneficiary caps.
- */
-contract IndividuallyCappedCrowdsale is Crowdsale, CapperRole {
-    using SafeMath for uint256;
-
-    mapping(address => uint256) private _contributions;
-    mapping(address => uint256) private _caps;
-
-    /**
-     * @dev Sets a specific beneficiary's maximum contribution.
-     * @param beneficiary Address to be capped
-     * @param cap Wei limit for individual contribution
-     */
-    function setCap(address beneficiary, uint256 cap) external onlyCapper {
-        _caps[beneficiary] = cap;
-    }
-
-    /**
-     * @dev Returns the cap of a specific beneficiary.
-     * @param beneficiary Address whose cap is to be checked
-     * @return Current cap for individual beneficiary
-     */
-    function getCap(address beneficiary) public view returns (uint256) {
-        return _caps[beneficiary];
-    }
-
-    /**
-     * @dev Returns the amount contributed so far by a specific beneficiary.
-     * @param beneficiary Address of contributor
-     * @return Beneficiary contribution so far
-     */
-    function getContribution(address beneficiary) public view returns (uint256) {
-        return _contributions[beneficiary];
-    }
-
-    /**
-     * @dev Extend parent behavior requiring purchase to respect the beneficiary's funding cap.
-     * @param beneficiary Token purchaser
-     * @param weiAmount Amount of wei contributed
-     */
-    function _preValidatePurchase(address beneficiary, uint256 weiAmount) internal view {
-        super._preValidatePurchase(beneficiary, weiAmount);
-        // 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.
-     * @param beneficiary Token purchaser
-     * @param weiAmount Amount of wei contributed
-     */
-    function _updatePurchasingState(address beneficiary, uint256 weiAmount) internal {
-        super._updatePurchasingState(beneficiary, weiAmount);
-        _contributions[beneficiary] = _contributions[beneficiary].add(weiAmount);
-    }
-}

contracts/crowdsale/validation/PausableCrowdsale.sol

@@ -1,21 +0,0 @@
-pragma solidity ^0.5.0;
-
-import "../Crowdsale.sol";
-import "../../lifecycle/Pausable.sol";
-
-/**
- * @title PausableCrowdsale
- * @dev Extension of Crowdsale contract where purchases can be paused and unpaused by the pauser role.
- */
-contract PausableCrowdsale is Crowdsale, Pausable {
-    /**
-     * @dev Validation of an incoming purchase. Use require statements to revert state when conditions are not met.
-     * Use super to concatenate validations.
-     * Adds the validation that the crowdsale must not be paused.
-     * @param _beneficiary Address performing the token purchase
-     * @param _weiAmount Value in wei involved in the purchase
-     */
-    function _preValidatePurchase(address _beneficiary, uint256 _weiAmount) internal view whenNotPaused {
-        return super._preValidatePurchase(_beneficiary, _weiAmount);
-    }
-}

contracts/crowdsale/validation/TimedCrowdsale.sol

@@ -1,98 +0,0 @@
-pragma solidity ^0.5.0;
-
-import "../../math/SafeMath.sol";
-import "../Crowdsale.sol";
-
-/**
- * @title TimedCrowdsale
- * @dev Crowdsale accepting contributions only within a time frame.
- */
-contract TimedCrowdsale is Crowdsale {
-    using SafeMath for uint256;
-
-    uint256 private _openingTime;
-    uint256 private _closingTime;
-
-    /**
-     * Event for crowdsale extending
-     * @param newClosingTime new closing time
-     * @param prevClosingTime old closing time
-     */
-    event TimedCrowdsaleExtended(uint256 prevClosingTime, uint256 newClosingTime);
-
-    /**
-     * @dev Reverts if not in crowdsale time range.
-     */
-    modifier onlyWhileOpen {
-        require(isOpen(), "TimedCrowdsale: not open");
-        _;
-    }
-
-    /**
-     * @dev Constructor, takes crowdsale opening and closing times.
-     * @param openingTime Crowdsale opening time
-     * @param closingTime Crowdsale closing time
-     */
-    constructor (uint256 openingTime, uint256 closingTime) public {
-        // solhint-disable-next-line not-rely-on-time
-        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;
-    }
-
-    /**
-     * @return the crowdsale opening time.
-     */
-    function openingTime() public view returns (uint256) {
-        return _openingTime;
-    }
-
-    /**
-     * @return the crowdsale closing time.
-     */
-    function closingTime() public view returns (uint256) {
-        return _closingTime;
-    }
-
-    /**
-     * @return true if the crowdsale is open, false otherwise.
-     */
-    function isOpen() public view returns (bool) {
-        // solhint-disable-next-line not-rely-on-time
-        return block.timestamp >= _openingTime && block.timestamp <= _closingTime;
-    }
-
-    /**
-     * @dev Checks whether the period in which the crowdsale is open has already elapsed.
-     * @return Whether crowdsale period has elapsed
-     */
-    function hasClosed() public view returns (bool) {
-        // solhint-disable-next-line not-rely-on-time
-        return block.timestamp > _closingTime;
-    }
-
-    /**
-     * @dev Extend parent behavior requiring to be within contributing period.
-     * @param beneficiary Token purchaser
-     * @param weiAmount Amount of wei contributed
-     */
-    function _preValidatePurchase(address beneficiary, uint256 weiAmount) internal onlyWhileOpen view {
-        super._preValidatePurchase(beneficiary, weiAmount);
-    }
-
-    /**
-     * @dev Extend crowdsale.
-     * @param newClosingTime Crowdsale closing time
-     */
-    function _extendTime(uint256 newClosingTime) internal {
-        require(!hasClosed(), "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

@@ -1,21 +0,0 @@
-pragma solidity ^0.5.0;
-import "../Crowdsale.sol";
-import "../../access/roles/WhitelistedRole.sol";
-
-
-/**
- * @title WhitelistCrowdsale
- * @dev Crowdsale in which only whitelisted users can contribute.
- */
-contract WhitelistCrowdsale is WhitelistedRole, Crowdsale {
-    /**
-     * @dev Extend parent behavior requiring beneficiary to be whitelisted. Note that no
-     * restriction is imposed on the account sending the transaction.
-     * @param _beneficiary Token beneficiary
-     * @param _weiAmount Amount of wei contributed
-     */
-    function _preValidatePurchase(address _beneficiary, uint256 _weiAmount) internal view {
-        require(isWhitelisted(_beneficiary), "WhitelistCrowdsale: beneficiary doesn't have the Whitelisted role");
-        super._preValidatePurchase(_beneficiary, _weiAmount);
-    }
-}

contracts/cryptography/ECDSA.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 /**
  * @dev Elliptic Curve Digital Signature Algorithm (ECDSA) operations.

contracts/cryptography/MerkleProof.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 /**
  * @dev These functions deal with verification of Merkle trees (hash trees),

contracts/drafts/Counters.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 import "../math/SafeMath.sol";
 

contracts/drafts/ERC1046/ERC20Metadata.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 import "../../token/ERC20/IERC20.sol";
 
@@ -18,7 +18,7 @@ contract ERC20Metadata {
         return _tokenURI;
     }
 
-    function _setTokenURI(string memory tokenURI_) internal {
+    function _setTokenURI(string memory tokenURI_) internal virtual {
         _tokenURI = tokenURI_;
     }
 }

contracts/drafts/ERC20Migrator.sol

@@ -1,103 +0,0 @@
-pragma solidity ^0.5.0;
-
-import "../token/ERC20/IERC20.sol";
-import "../token/ERC20/ERC20Mintable.sol";
-import "../token/ERC20/SafeERC20.sol";
-import "../math/Math.sol";
-
-/**
- * @title ERC20Migrator
- * @dev This contract can be used to migrate an ERC20 token from one
- * contract to another, where each token holder has to opt-in to the migration.
- * To opt-in, users must approve for this contract the number of tokens they
- * want to migrate. Once the allowance is set up, anyone can trigger the
- * migration to the new token contract. In this way, token holders "turn in"
- * their old balance and will be minted an equal amount in the new token.
- * The new token contract must be mintable. For the precise interface refer to
- * OpenZeppelin's {ERC20Mintable}, but the only functions that are needed are
- * {MinterRole-isMinter} and {ERC20Mintable-mint}. The migrator will check
- * that it is a minter for the token.
- * The balance from the legacy token will be transferred to the migrator, as it
- * is migrated, and remain there forever.
- * Although this contract can be used in many different scenarios, the main
- * motivation was to provide a way to migrate ERC20 tokens into an upgradeable
- * version of it using ZeppelinOS. To read more about how this can be done
- * using this implementation, please follow the official documentation site of
- * ZeppelinOS: https://docs.zeppelinos.org/docs/erc20_onboarding.html
- *
- * Example of usage:
- * ```
- * const migrator = await ERC20Migrator.new(legacyToken.address);
- * await newToken.addMinter(migrator.address);
- * await migrator.beginMigration(newToken.address);
- * ```
- */
-contract ERC20Migrator {
-    using SafeERC20 for IERC20;
-
-    /// Address of the old token contract
-    IERC20 private _legacyToken;
-
-    /// Address of the new token contract
-    ERC20Mintable private _newToken;
-
-    /**
-     * @param legacyToken address of the old token contract
-     */
-    constructor (IERC20 legacyToken) public {
-        require(address(legacyToken) != address(0), "ERC20Migrator: legacy token is the zero address");
-        _legacyToken = legacyToken;
-    }
-
-    /**
-     * @dev Returns the legacy token that is being migrated.
-     */
-    function legacyToken() public view returns (IERC20) {
-        return _legacyToken;
-    }
-
-    /**
-     * @dev Returns the new token to which we are migrating.
-     */
-    function newToken() public view returns (IERC20) {
-        return _newToken;
-    }
-
-    /**
-     * @dev Begins the migration by setting which is the new token that will be
-     * minted. This contract must be a minter for the new token.
-     * @param newToken_ the token that will be minted
-     */
-    function beginMigration(ERC20Mintable newToken_) public {
-        require(address(_newToken) == address(0), "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_;
-    }
-
-    /**
-     * @dev Transfers part of an account's balance in the old token to this
-     * contract, and mints the same amount of new tokens for that account.
-     * @param account whose tokens will be migrated
-     * @param amount amount of tokens to be migrated
-     */
-    function migrate(address account, uint256 amount) public {
-        require(address(_newToken) != address(0), "ERC20Migrator: migration not started");
-        _legacyToken.safeTransferFrom(account, address(this), amount);
-        _newToken.mint(account, amount);
-    }
-
-    /**
-     * @dev Transfers all of an account's allowed balance in the old token to
-     * this contract, and mints the same amount of new tokens for that account.
-     * @param account whose tokens will be migrated
-     */
-    function migrateAll(address account) public {
-        uint256 balance = _legacyToken.balanceOf(account);
-        uint256 allowance = _legacyToken.allowance(account, address(this));
-        uint256 amount = Math.min(balance, allowance);
-        migrate(account, amount);
-    }
-}

contracts/drafts/ERC20Snapshot.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 import "../math/SafeMath.sol";
 import "../utils/Arrays.sol";
@@ -43,7 +43,7 @@ contract ERC20Snapshot is ERC20 {
     // Creates a new snapshot id. Balances are only stored in snapshots on demand: unless a snapshot was taken, a
     // balance change will not be recorded. This means the extra added cost of storing snapshotted balances is only paid
     // when required, but is also flexible enough that it allows for e.g. daily snapshots.
-    function snapshot() public returns (uint256) {
+    function snapshot() public virtual returns (uint256) {
         _currentSnapshotId.increment();
 
         uint256 currentId = _currentSnapshotId.current();
@@ -66,21 +66,21 @@ contract ERC20Snapshot is ERC20 {
     // _transfer, _mint and _burn are the only functions where the balances are modified, so it is there that the
     // snapshots are updated. Note that the update happens _before_ the balance change, with the pre-modified value.
     // The same is true for the total supply and _mint and _burn.
-    function _transfer(address from, address to, uint256 value) internal {
+    function _transfer(address from, address to, uint256 value) internal virtual override {
         _updateAccountSnapshot(from);
         _updateAccountSnapshot(to);
 
         super._transfer(from, to, value);
     }
 
-    function _mint(address account, uint256 value) internal {
+    function _mint(address account, uint256 value) internal virtual override {
         _updateAccountSnapshot(account);
         _updateTotalSupplySnapshot();
 
         super._mint(account, value);
     }
 
-    function _burn(address account, uint256 value) internal {
+    function _burn(address account, uint256 value) internal virtual override {
         _updateAccountSnapshot(account);
         _updateTotalSupplySnapshot();
 

contracts/drafts/SignedSafeMath.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 /**
  * @title SignedSafeMath

contracts/drafts/Strings.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 /**
  * @title Strings

contracts/drafts/TokenVesting.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 import "../token/ERC20/SafeERC20.sol";
 import "../ownership/Ownable.sol";

contracts/examples/SampleCrowdsale.sol

@@ -1,53 +0,0 @@
-pragma solidity ^0.5.0;
-
-import "../crowdsale/validation/CappedCrowdsale.sol";
-import "../crowdsale/distribution/RefundableCrowdsale.sol";
-import "../crowdsale/emission/MintedCrowdsale.sol";
-import "../token/ERC20/ERC20Mintable.sol";
-import "../token/ERC20/ERC20Detailed.sol";
-
-/**
- * @title SampleCrowdsaleToken
- * @dev Very simple ERC20 Token that can be minted.
- * It is meant to be used in a crowdsale contract.
- */
-contract SampleCrowdsaleToken is ERC20Mintable, ERC20Detailed {
-    constructor () public ERC20Detailed("Sample Crowdsale Token", "SCT", 18) {
-        // solhint-disable-previous-line no-empty-blocks
-    }
-}
-
-/**
- * @title SampleCrowdsale
- * @dev This is an example of a fully fledged crowdsale.
- * The way to add new features to a base crowdsale is by multiple inheritance.
- * In this example we are providing following extensions:
- * CappedCrowdsale - sets a max boundary for raised funds
- * RefundableCrowdsale - set a min goal to be reached and returns funds if it's not met
- * MintedCrowdsale - assumes the token can be minted by the crowdsale, which does so
- * when receiving purchases.
- *
- * After adding multiple features it's good practice to run integration tests
- * to ensure that subcontracts works together as intended.
- */
-contract SampleCrowdsale is CappedCrowdsale, RefundableCrowdsale, MintedCrowdsale {
-    constructor (
-        uint256 openingTime,
-        uint256 closingTime,
-        uint256 rate,
-        address payable wallet,
-        uint256 cap,
-        ERC20Mintable token,
-        uint256 goal
-    )
-        public
-        Crowdsale(rate, wallet, token)
-        CappedCrowdsale(cap)
-        TimedCrowdsale(openingTime, closingTime)
-        RefundableCrowdsale(goal)
-    {
-        //As goal needs to be met for a successful crowdsale
-        //the value needs to less or equal than a cap which is limit for accepted funds
-        require(goal <= cap, "SampleCrowdSale: goal is greater than cap");
-    }
-}

contracts/examples/SimpleToken.sol

@@ -1,21 +0,0 @@
-pragma solidity ^0.5.0;
-
-import "../GSN/Context.sol";
-import "../token/ERC20/ERC20.sol";
-import "../token/ERC20/ERC20Detailed.sol";
-
-/**
- * @title SimpleToken
- * @dev Very simple ERC20 Token example, where all tokens are pre-assigned to the creator.
- * Note they can later distribute these tokens as they wish using `transfer` and other
- * `ERC20` functions.
- */
-contract SimpleToken is Context, ERC20, ERC20Detailed {
-
-    /**
-     * @dev Constructor that gives _msgSender() all of existing tokens.
-     */
-    constructor () public ERC20Detailed("SimpleToken", "SIM", 18) {
-        _mint(_msgSender(), 10000 * (10 ** uint256(decimals())));
-    }
-}

contracts/introspection/ERC165.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 import "./IERC165.sol";
 
@@ -30,7 +30,7 @@ contract ERC165 is IERC165 {
      *
      * Time complexity O(1), guaranteed to always use less than 30 000 gas.
      */
-    function supportsInterface(bytes4 interfaceId) external view returns (bool) {
+    function supportsInterface(bytes4 interfaceId) external view override returns (bool) {
         return _supportedInterfaces[interfaceId];
     }
 
@@ -45,7 +45,7 @@ contract ERC165 is IERC165 {
      *
      * - `interfaceId` cannot be the ERC165 invalid interface (`0xffffffff`).
      */
-    function _registerInterface(bytes4 interfaceId) internal {
+    function _registerInterface(bytes4 interfaceId) internal virtual {
         require(interfaceId != 0xffffffff, "ERC165: invalid interface id");
         _supportedInterfaces[interfaceId] = true;
     }

contracts/introspection/ERC165Checker.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.10;
+pragma solidity ^0.6.0;
 
 /**
  * @dev Library used to query support of an interface declared via {IERC165}.

contracts/introspection/ERC1820Implementer.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 import "./IERC1820Implementer.sol";
 
@@ -18,7 +18,7 @@ contract ERC1820Implementer is IERC1820Implementer {
     /**
      * See {IERC1820Implementer-canImplementInterfaceForAddress}.
      */
-    function canImplementInterfaceForAddress(bytes32 interfaceHash, address account) external view returns (bytes32) {
+    function canImplementInterfaceForAddress(bytes32 interfaceHash, address account) external view override returns (bytes32) {
         return _supportedInterfaces[interfaceHash][account] ? ERC1820_ACCEPT_MAGIC : bytes32(0x00);
     }
 
@@ -29,7 +29,7 @@ contract ERC1820Implementer is IERC1820Implementer {
      * See {IERC1820Registry-setInterfaceImplementer} and
      * {IERC1820Registry-interfaceHash}.
      */
-    function _registerInterfaceForAddress(bytes32 interfaceHash, address account) internal {
+    function _registerInterfaceForAddress(bytes32 interfaceHash, address account) internal virtual {
         _supportedInterfaces[interfaceHash][account] = true;
     }
 }

contracts/introspection/IERC165.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 /**
  * @dev Interface of the ERC165 standard, as defined in the

contracts/introspection/IERC1820Implementer.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 /**
  * @dev Interface for an ERC1820 implementer, as defined in the

contracts/introspection/IERC1820Registry.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 /**
  * @dev Interface of the global ERC1820 Registry, as defined in the

contracts/lifecycle/Pausable.sol

@@ -1,7 +1,6 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 import "../GSN/Context.sol";
-import "../access/roles/PauserRole.sol";
 
 /**
  * @dev Contract module which allows children to implement an emergency stop
@@ -12,7 +11,7 @@ import "../access/roles/PauserRole.sol";
  * the functions of your contract. Note that they will not be pausable by
  * simply including this module, only once the modifiers are put in place.
  */
-contract Pausable is Context, PauserRole {
+contract Pausable is Context {
     /**
      * @dev Emitted when the pause is triggered by a pauser (`account`).
      */
@@ -59,7 +58,7 @@ contract Pausable is Context, PauserRole {
     /**
      * @dev Called by a pauser to pause, triggers stopped state.
      */
-    function pause() public onlyPauser whenNotPaused {
+    function _pause() internal virtual whenNotPaused {
         _paused = true;
         emit Paused(_msgSender());
     }
@@ -67,7 +66,7 @@ contract Pausable is Context, PauserRole {
     /**
      * @dev Called by a pauser to unpause, returns to normal state.
      */
-    function unpause() public onlyPauser whenPaused {
+    function _unpause() internal virtual whenPaused {
         _paused = false;
         emit Unpaused(_msgSender());
     }

contracts/math/Math.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 /**
  * @dev Standard math utilities missing in the Solidity language.

contracts/math/SafeMath.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 /**
  * @dev Wrappers over Solidity's arithmetic operations with added overflow

contracts/mocks/AddressImpl.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 import "../utils/Address.sol";
 
@@ -15,5 +15,6 @@ contract AddressImpl {
         Address.sendValue(receiver, amount);
     }
 
-    function () external payable { } // sendValue's tests require the contract to hold Ether
+    // sendValue's tests require the contract to hold Ether
+    receive () external payable { }
 }

contracts/mocks/AllowanceCrowdsaleImpl.sol

@@ -1,14 +0,0 @@
-pragma solidity ^0.5.0;
-
-import "../token/ERC20/IERC20.sol";
-import "../crowdsale/emission/AllowanceCrowdsale.sol";
-
-contract AllowanceCrowdsaleImpl is AllowanceCrowdsale {
-    constructor (uint256 rate, address payable wallet, IERC20 token, address tokenWallet)
-        public
-        Crowdsale(rate, wallet, token)
-        AllowanceCrowdsale(tokenWallet)
-    {
-        // solhint-disable-previous-line no-empty-blocks
-    }
-}

contracts/mocks/ArraysImpl.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 import "../utils/Arrays.sol";
 

contracts/mocks/CappedCrowdsaleImpl.sol

@@ -1,14 +0,0 @@
-pragma solidity ^0.5.0;
-
-import "../token/ERC20/IERC20.sol";
-import "../crowdsale/validation/CappedCrowdsale.sol";
-
-contract CappedCrowdsaleImpl is CappedCrowdsale {
-    constructor (uint256 rate, address payable wallet, IERC20 token, uint256 cap)
-        public
-        Crowdsale(rate, wallet, token)
-        CappedCrowdsale(cap)
-    {
-        // solhint-disable-previous-line no-empty-blocks
-    }
-}

contracts/mocks/CapperRoleMock.sol

@@ -1,18 +0,0 @@
-pragma solidity ^0.5.0;
-
-import "../access/roles/CapperRole.sol";
-
-contract CapperRoleMock is CapperRole {
-    function removeCapper(address account) public {
-        _removeCapper(account);
-    }
-
-    function onlyCapperMock() public view onlyCapper {
-        // solhint-disable-previous-line no-empty-blocks
-    }
-
-    // Causes a compilation error if super._removeCapper is not internal
-    function _removeCapper(address account) internal {
-        super._removeCapper(account);
-    }
-}

contracts/mocks/ConditionalEscrowMock.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 import "../payment/escrow/ConditionalEscrow.sol";
 
@@ -10,7 +10,7 @@ contract ConditionalEscrowMock is ConditionalEscrow {
         _allowed[payee] = allowed;
     }
 
-    function withdrawalAllowed(address payee) public view returns (bool) {
+    function withdrawalAllowed(address payee) public view override returns (bool) {
         return _allowed[payee];
     }
 }

contracts/mocks/ContextMock.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 import "../GSN/Context.sol";
 

contracts/mocks/CountersImpl.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 import "../drafts/Counters.sol";
 

contracts/mocks/Create2Impl.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 import "../utils/Create2.sol";
 import "../token/ERC20/ERC20.sol";

contracts/mocks/CrowdsaleMock.sol

@@ -1,9 +0,0 @@
-pragma solidity ^0.5.0;
-
-import "../crowdsale/Crowdsale.sol";
-
-contract CrowdsaleMock is Crowdsale {
-    constructor (uint256 rate, address payable wallet, IERC20 token) public Crowdsale(rate, wallet, token) {
-        // solhint-disable-previous-line no-empty-blocks
-    }
-}

contracts/mocks/ECDSAMock.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 import "../cryptography/ECDSA.sol";
 

contracts/mocks/ERC165/ERC165InterfacesSupported.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 import "../../introspection/IERC165.sol";
 
@@ -34,7 +34,7 @@ contract SupportsInterfaceWithLookupMock is IERC165 {
     /**
      * @dev Implement supportsInterface(bytes4) using a lookup table.
      */
-    function supportsInterface(bytes4 interfaceId) external view returns (bool) {
+    function supportsInterface(bytes4 interfaceId) external view override returns (bool) {
         return _supportedInterfaces[interfaceId];
     }
 

contracts/mocks/ERC165/ERC165NotSupported.sol

@@ -1,5 +1,3 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
-contract ERC165NotSupported {
-    // solhint-disable-previous-line no-empty-blocks
-}
+contract ERC165NotSupported { }

contracts/mocks/ERC165CheckerMock.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 import "../introspection/ERC165Checker.sol";
 

contracts/mocks/ERC165Mock.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 import "../introspection/ERC165.sol";
 

contracts/mocks/ERC1820ImplementerMock.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 import "../introspection/ERC1820Implementer.sol";
 

contracts/mocks/ERC20BurnableMock.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 import "../token/ERC20/ERC20Burnable.sol";
 

contracts/mocks/ERC20CappedMock.sol

@@ -0,0 +1,11 @@
+pragma solidity ^0.6.0;
+
+import "../token/ERC20/ERC20Capped.sol";
+
+contract ERC20CappedMock is ERC20Capped {
+    constructor (uint256 cap) public ERC20Capped(cap) { }
+
+    function mint(address to, uint256 tokenId) public {
+        _mint(to, tokenId);
+    }
+}

contracts/mocks/ERC20DetailedMock.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 import "../token/ERC20/ERC20.sol";
 import "../token/ERC20/ERC20Detailed.sol";
@@ -8,6 +8,6 @@ contract ERC20DetailedMock is ERC20, ERC20Detailed {
         public
         ERC20Detailed(name, symbol, decimals)
     {
-        // solhint-disable-previous-line no-empty-blocks
+
     }
 }

contracts/mocks/ERC20MetadataMock.sol

@@ -1,12 +1,10 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 import "../token/ERC20/ERC20.sol";
 import "../drafts/ERC1046/ERC20Metadata.sol";
 
 contract ERC20MetadataMock is ERC20, ERC20Metadata {
-    constructor (string memory tokenURI) public ERC20Metadata(tokenURI) {
-        // solhint-disable-previous-line no-empty-blocks
-    }
+    constructor (string memory tokenURI) public ERC20Metadata(tokenURI) { }
 
     function setTokenURI(string memory tokenURI) public {
         _setTokenURI(tokenURI);

contracts/mocks/ERC20MintableMock.sol

@@ -1,8 +0,0 @@
-pragma solidity ^0.5.0;
-
-import "../token/ERC20/ERC20Mintable.sol";
-import "./MinterRoleMock.sol";
-
-contract ERC20MintableMock is ERC20Mintable, MinterRoleMock {
-    // solhint-disable-previous-line no-empty-blocks
-}

contracts/mocks/ERC20Mock.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 import "../token/ERC20/ERC20.sol";
 

contracts/mocks/ERC20PausableMock.sol

@@ -1,11 +1,18 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 import "../token/ERC20/ERC20Pausable.sol";
-import "./PauserRoleMock.sol";
 
 // mock class using ERC20Pausable
-contract ERC20PausableMock is ERC20Pausable, PauserRoleMock {
+contract ERC20PausableMock is ERC20Pausable {
     constructor (address initialAccount, uint256 initialBalance) public {
         _mint(initialAccount, initialBalance);
     }
+
+    function pause() external {
+        _pause();
+    }
+
+    function unpause() external {
+        _unpause();
+    }
 }

contracts/mocks/ERC20SnapshotMock.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 import "../drafts/ERC20Snapshot.sol";
 

contracts/mocks/ERC721BurnableMock.sol

@@ -0,0 +1,9 @@
+pragma solidity ^0.6.0;
+
+import "../token/ERC721/ERC721Burnable.sol";
+
+contract ERC721BurnableMock is ERC721Burnable {
+    function mint(address to, uint256 tokenId) public {
+        _mint(to, tokenId);
+    }
+}

contracts/mocks/ERC721FullMock.sol

@@ -1,8 +1,6 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 import "../token/ERC721/ERC721Full.sol";
-import "../token/ERC721/ERC721Mintable.sol";
-import "../token/ERC721/ERC721MetadataMintable.sol";
 import "../token/ERC721/ERC721Burnable.sol";
 
 /**
@@ -10,10 +8,8 @@ import "../token/ERC721/ERC721Burnable.sol";
  * This mock just provides public functions for setting metadata URI, getting all tokens of an owner,
  * checking token existence, removal of a token from an address
  */
-contract ERC721FullMock is ERC721Full, ERC721Mintable, ERC721MetadataMintable, ERC721Burnable {
-    constructor (string memory name, string memory symbol) public ERC721Mintable() ERC721Full(name, symbol) {
-        // solhint-disable-previous-line no-empty-blocks
-    }
+contract ERC721FullMock is ERC721Full, ERC721Burnable {
+    constructor (string memory name, string memory symbol) public ERC721Full(name, symbol) { }
 
     function exists(uint256 tokenId) public view returns (bool) {
         return _exists(tokenId);
@@ -30,4 +26,12 @@ contract ERC721FullMock is ERC721Full, ERC721Mintable, ERC721MetadataMintable, E
     function setBaseURI(string memory baseURI) public {
         _setBaseURI(baseURI);
     }
+
+    function _beforeTokenTransfer(address from, address to, uint256 tokenId) internal virtual override(ERC721, ERC721Full) {
+        super._beforeTokenTransfer(from, to, tokenId);
+    }
+
+    function mint(address to, uint256 tokenId) public {
+        _mint(to, tokenId);
+    }
 }

contracts/mocks/ERC721GSNRecipientMock.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 import "../token/ERC721/ERC721.sol";
 import "../GSN/GSNRecipient.sol";
@@ -10,9 +10,16 @@ import "../GSN/GSNRecipientSignature.sol";
  */
 contract ERC721GSNRecipientMock is ERC721, GSNRecipient, GSNRecipientSignature {
     constructor(address trustedSigner) public GSNRecipientSignature(trustedSigner) { }
-    // solhint-disable-previous-line no-empty-blocks
 
     function mint(uint256 tokenId) public {
         _mint(_msgSender(), tokenId);
     }
+
+    function _msgSender() internal view override(Context, GSNRecipient) returns (address payable) {
+        return GSNRecipient._msgSender();
+    }
+
+    function _msgData() internal view override(Context, GSNRecipient) returns (bytes memory) {
+        return GSNRecipient._msgData();
+    }
 }

contracts/mocks/ERC721MintableBurnableImpl.sol

@@ -1,15 +0,0 @@
-pragma solidity ^0.5.0;
-
-import "../token/ERC721/ERC721Full.sol";
-import "../token/ERC721/ERC721Mintable.sol";
-import "../token/ERC721/ERC721MetadataMintable.sol";
-import "../token/ERC721/ERC721Burnable.sol";
-
-/**
- * @title ERC721MintableBurnableImpl
- */
-contract ERC721MintableBurnableImpl is ERC721Full, ERC721Mintable, ERC721MetadataMintable, ERC721Burnable {
-    constructor () public ERC721Mintable() ERC721Full("Test", "TEST") {
-        // solhint-disable-previous-line no-empty-blocks
-    }
-}

contracts/mocks/ERC721Mock.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 import "../token/ERC721/ERC721.sol";
 

contracts/mocks/ERC721PausableMock.sol

@@ -1,13 +1,12 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 import "../token/ERC721/ERC721Pausable.sol";
-import "./PauserRoleMock.sol";
 
 /**
  * @title ERC721PausableMock
  * This mock just provides a public mint, burn and exists functions for testing purposes
  */
-contract ERC721PausableMock is ERC721Pausable, PauserRoleMock {
+contract ERC721PausableMock is ERC721Pausable {
     function mint(address to, uint256 tokenId) public {
         super._mint(to, tokenId);
     }
@@ -19,4 +18,12 @@ contract ERC721PausableMock is ERC721Pausable, PauserRoleMock {
     function exists(uint256 tokenId) public view returns (bool) {
         return super._exists(tokenId);
     }
+
+    function pause() external {
+        _pause();
+    }
+
+    function unpause() external {
+        _unpause();
+    }
 }

contracts/mocks/ERC721ReceiverMock.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 import "../token/ERC721/IERC721Receiver.sol";
 
@@ -14,7 +14,7 @@ contract ERC721ReceiverMock is IERC721Receiver {
     }
 
     function onERC721Received(address operator, address from, uint256 tokenId, bytes memory data)
-        public returns (bytes4)
+        public override returns (bytes4)
     {
         require(!_reverts, "ERC721ReceiverMock: reverting");
         emit Received(operator, from, tokenId, data, gasleft());

contracts/mocks/ERC777Mock.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 import "../GSN/Context.sol";
 import "../token/ERC777/ERC777.sol";

contracts/mocks/ERC777SenderRecipientMock.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 import "../GSN/Context.sol";
 import "../token/ERC777/IERC777.sol";
@@ -47,7 +47,7 @@ contract ERC777SenderRecipientMock is Context, IERC777Sender, IERC777Recipient,
         uint256 amount,
         bytes calldata userData,
         bytes calldata operatorData
-    ) external {
+    ) external override {
         if (_shouldRevertSend) {
             revert();
         }
@@ -78,7 +78,7 @@ contract ERC777SenderRecipientMock is Context, IERC777Sender, IERC777Recipient,
         uint256 amount,
         bytes calldata userData,
         bytes calldata operatorData
-    ) external{
+    ) external override {
         if (_shouldRevertReceive) {
             revert();
         }

contracts/mocks/EnumerableSetMock.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 import "../utils/EnumerableSet.sol";
 

contracts/mocks/EtherReceiverMock.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 contract EtherReceiverMock {
     bool private _acceptEther;
@@ -7,7 +7,7 @@ contract EtherReceiverMock {
         _acceptEther = acceptEther;
     }
 
-    function () external payable {
+    receive () external payable {
         if (!_acceptEther) {
             revert();
         }

contracts/mocks/FinalizableCrowdsaleImpl.sol

@@ -1,14 +0,0 @@
-pragma solidity ^0.5.0;
-
-import "../token/ERC20/IERC20.sol";
-import "../crowdsale/distribution/FinalizableCrowdsale.sol";
-
-contract FinalizableCrowdsaleImpl is FinalizableCrowdsale {
-    constructor (uint256 openingTime, uint256 closingTime, uint256 rate, address payable wallet, IERC20 token)
-        public
-        Crowdsale(rate, wallet, token)
-        TimedCrowdsale(openingTime, closingTime)
-    {
-        // solhint-disable-previous-line no-empty-blocks
-    }
-}

contracts/mocks/GSNRecipientERC20FeeMock.sol

@@ -1,12 +1,10 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 import "../GSN/GSNRecipient.sol";
 import "../GSN/GSNRecipientERC20Fee.sol";
 
 contract GSNRecipientERC20FeeMock is GSNRecipient, GSNRecipientERC20Fee {
-    constructor(string memory name, string memory symbol) public GSNRecipientERC20Fee(name, symbol) {
-        // solhint-disable-previous-line no-empty-blocks
-    }
+    constructor(string memory name, string memory symbol) public GSNRecipientERC20Fee(name, symbol) { }
 
     function mint(address account, uint256 amount) public {
         _mint(account, amount);

contracts/mocks/GSNRecipientMock.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 import "./ContextMock.sol";
 import "../GSN/GSNRecipient.sol";
@@ -12,20 +12,25 @@ contract GSNRecipientMock is ContextMock, GSNRecipient {
     function acceptRelayedCall(address, address, bytes calldata, uint256, uint256, uint256, uint256, bytes calldata, uint256)
         external
         view
+        override
         returns (uint256, bytes memory)
     {
         return (0, "");
     }
 
-    function _preRelayedCall(bytes memory) internal returns (bytes32) {
-        // solhint-disable-previous-line no-empty-blocks
-    }
+    function _preRelayedCall(bytes memory) internal override returns (bytes32) { }
 
-    function _postRelayedCall(bytes memory, bool, uint256, bytes32) internal {
-        // solhint-disable-previous-line no-empty-blocks
-    }
+    function _postRelayedCall(bytes memory, bool, uint256, bytes32) internal override { }
 
     function upgradeRelayHub(address newRelayHub) public {
         return _upgradeRelayHub(newRelayHub);
     }
+
+    function _msgSender() internal override(Context, GSNRecipient) view virtual returns (address payable) {
+        return GSNRecipient._msgSender();
+    }
+
+    function _msgData() internal override(Context, GSNRecipient) view virtual returns (bytes memory) {
+        return GSNRecipient._msgData();
+    }
 }

contracts/mocks/GSNRecipientSignatureMock.sol

@@ -1,12 +1,10 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 import "../GSN/GSNRecipient.sol";
 import "../GSN/GSNRecipientSignature.sol";
 
 contract GSNRecipientSignatureMock is GSNRecipient, GSNRecipientSignature {
-    constructor(address trustedSigner) public GSNRecipientSignature(trustedSigner) {
-        // solhint-disable-previous-line no-empty-blocks
-    }
+    constructor(address trustedSigner) public GSNRecipientSignature(trustedSigner) { }
 
     event MockFunctionCalled();
 

contracts/mocks/IncreasingPriceCrowdsaleImpl.sol

@@ -1,22 +0,0 @@
-pragma solidity ^0.5.0;
-
-import "../crowdsale/price/IncreasingPriceCrowdsale.sol";
-import "../math/SafeMath.sol";
-
-contract IncreasingPriceCrowdsaleImpl is IncreasingPriceCrowdsale {
-    constructor (
-        uint256 openingTime,
-        uint256 closingTime,
-        address payable wallet,
-        IERC20 token,
-        uint256 initialRate,
-        uint256 finalRate
-    )
-        public
-        Crowdsale(initialRate, wallet, token)
-        TimedCrowdsale(openingTime, closingTime)
-        IncreasingPriceCrowdsale(initialRate, finalRate)
-    {
-        // solhint-disable-previous-line no-empty-blocks
-    }
-}

contracts/mocks/IndividuallyCappedCrowdsaleImpl.sol

@@ -1,11 +0,0 @@
-pragma solidity ^0.5.0;
-
-import "../token/ERC20/IERC20.sol";
-import "../crowdsale/validation/IndividuallyCappedCrowdsale.sol";
-import "./CapperRoleMock.sol";
-
-contract IndividuallyCappedCrowdsaleImpl is IndividuallyCappedCrowdsale, CapperRoleMock {
-    constructor (uint256 rate, address payable wallet, IERC20 token) public Crowdsale(rate, wallet, token) {
-        // solhint-disable-previous-line no-empty-blocks
-    }
-}

contracts/mocks/MathMock.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 import "../math/Math.sol";
 

contracts/mocks/MerkleProofWrapper.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 import { MerkleProof } from "../cryptography/MerkleProof.sol";
 

contracts/mocks/MintedCrowdsaleImpl.sol

@@ -1,10 +0,0 @@
-pragma solidity ^0.5.0;
-
-import "../token/ERC20/ERC20Mintable.sol";
-import "../crowdsale/emission/MintedCrowdsale.sol";
-
-contract MintedCrowdsaleImpl is MintedCrowdsale {
-    constructor (uint256 rate, address payable wallet, ERC20Mintable token) public Crowdsale(rate, wallet, token) {
-        // solhint-disable-previous-line no-empty-blocks
-    }
-}

contracts/mocks/MinterRoleMock.sol

@@ -1,18 +0,0 @@
-pragma solidity ^0.5.0;
-
-import "../access/roles/MinterRole.sol";
-
-contract MinterRoleMock is MinterRole {
-    function removeMinter(address account) public {
-        _removeMinter(account);
-    }
-
-    function onlyMinterMock() public view onlyMinter {
-        // solhint-disable-previous-line no-empty-blocks
-    }
-
-    // Causes a compilation error if super._removeMinter is not internal
-    function _removeMinter(address account) internal {
-        super._removeMinter(account);
-    }
-}

contracts/mocks/OwnableInterfaceId.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 import "../ownership/Ownable.sol";
 

contracts/mocks/OwnableMock.sol

@@ -1,7 +1,5 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 import "../ownership/Ownable.sol";
 
-contract OwnableMock is Ownable {
-    // solhint-disable-previous-line no-empty-blocks
-}
+contract OwnableMock is Ownable { }

contracts/mocks/PausableCrowdsaleImpl.sol

@@ -1,10 +0,0 @@
-pragma solidity ^0.5.0;
-
-import "../token/ERC20/ERC20.sol";
-import "../crowdsale/validation/PausableCrowdsale.sol";
-
-contract PausableCrowdsaleImpl is PausableCrowdsale {
-    constructor (uint256 _rate, address payable _wallet, ERC20 _token) public Crowdsale(_rate, _wallet, _token) {
-        // solhint-disable-previous-line no-empty-blocks
-    }
-}

contracts/mocks/PausableMock.sol

@@ -1,10 +1,8 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.6.0;
 
 import "../lifecycle/Pausable.sol";
-import "./PauserRoleMock.sol";
 
-// mock class using Pausable
-contract PausableMock is Pausable, PauserRoleMock {
+contract PausableMock is Pausable {
     bool public drasticMeasureTaken;
     uint256 public count;
 
@@ -20,4 +18,12 @@ contract PausableMock is Pausable, PauserRoleMock {
     function drasticMeasure() external whenPaused {
         drasticMeasureTaken = true;
     }
+
+    function pause() external {
+        _pause();
+    }
+
+    function unpause() external {
+        _unpause();
+    }
 }

contracts/mocks/PauserRoleMock.sol

@@ -1,18 +0,0 @@
-pragma solidity ^0.5.0;
-
-import "../access/roles/PauserRole.sol";
-
-contract PauserRoleMock is PauserRole {
-    function removePauser(address account) public {
-        _removePauser(account);
-    }
-
-    function onlyPauserMock() public view onlyPauser {
-        // solhint-disable-previous-line no-empty-blocks
-    }
-
-    // Causes a compilation error if super._removePauser is not internal
-    function _removePauser(address account) internal {
-        super._removePauser(account);
-    }
-}

contracts/mocks/PostDeliveryCrowdsaleImpl.sol

@@ -1,14 +0,0 @@
-pragma solidity ^0.5.0;
-
-import "../token/ERC20/IERC20.sol";
-import "../crowdsale/distribution/PostDeliveryCrowdsale.sol";
-
-contract PostDeliveryCrowdsaleImpl is PostDeliveryCrowdsale {
-    constructor (uint256 openingTime, uint256 closingTime, uint256 rate, address payable wallet, IERC20 token)
-        public
-        TimedCrowdsale(openingTime, closingTime)
-        Crowdsale(rate, wallet, token)
-    {
-        // solhint-disable-previous-line no-empty-blocks
-    }
-}