build: update to Solidity 6.4 (#165)

Author: abarmat

contracts/DisputeManager.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.6.4;
 
 /*
  * @title Dispute management

contracts/GNS.sol

@@ -1,8 +1,7 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.6.4;
 
 import "./Governed.sol";
 
-
 contract GNS is Governed {
     /*
      * @title Graph Name Service (GNS) contract

contracts/Governed.sol

@@ -1,5 +1,4 @@
-pragma solidity ^0.5.2;
-
+pragma solidity ^0.6.4;
 
 contract Governed {
     /*

contracts/GraphToken.sol

@@ -1,53 +1,35 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.6.4;
+
 /*
  * @title GraphToken contract
  *
- * @author Bryant Eisenbach
- * @author Reuven Etzion
- *
- * Requirements
- * @req 01 The Graph Token shall implement the ERC20 Token Standard
- * @req 02 The Graph Token shall allow tokens staked in the protocol to be burned
- * @req 03 The Graph Token shall allow tokens to be minted to reward protocol participants
- * @req 04 The Graph Token shall only allow designated accounts the authority to mint
- *         Note: for example, the Payment Channel Hub and Rewards Manager contracts
- * @req 05 The Graph Token shall allow the protocol Governance to modify the accounts that have
- *         minting authority
- * @req 06 The Graph Token shall allow the protocol Governance to mint new tokens
- * @req 07 The Graph Token shall mint an inital distribution of tokens
- * @req 08 The Graph Token shall allow a token holder to stake in the protocol for indexing or
- *         curation markets for a particular Subgraph
- *
  */
 
 import "./Governed.sol";
-import "openzeppelin-solidity/contracts/token/ERC20/ERC20Burnable.sol";
-import "openzeppelin-solidity/contracts/token/ERC20/ERC20Mintable.sol";
-import "openzeppelin-solidity/contracts/token/ERC20/ERC20Detailed.sol";
-
+import "@openzeppelin/contracts/token/ERC20/ERC20Burnable.sol";
+import "@openzeppelin/contracts/token/ERC20/ERC20Detailed.sol";
 
 // @imp 08 target _to of transfer(_to, _amount, _data) in Token must implement this interface
 // NOTE: This is based off of ERC777TokensRecipient interface, but does not fully implement it
-contract TokenReceiver {
+interface TokenReceiver {
     function tokensReceived(
         address _from,
         uint256 _amount,
         bytes calldata _data
     ) external returns (bool);
 }
 
+contract GraphToken is Governed, ERC20Detailed, ERC20Burnable {
+    mapping(address => bool) private _minters;
+
+    // -- Events --
+    event MinterAdded(address indexed account);
+    event MinterRemoved(address indexed account);
 
-contract GraphToken is
-    Governed,
-    ERC20Detailed, // @imp 01
-    ERC20Burnable, // @imp 01, 02
-    ERC20Mintable // @imp 01, 03, 04
-{
-    // @imp 05, 06 Override so Governor can set Minters or mint tokens
     modifier onlyMinter() {
         require(
             isMinter(msg.sender) || msg.sender == governor,
-            "Only minter can call."
+            "Only minter can call"
         );
         _;
     }
@@ -62,22 +44,38 @@ contract GraphToken is
         ERC20Detailed("Graph Token", "GRT", 18)
         Governed(_governor)
     {
-        // @imp 06 Governor is initially the sole treasurer
+        // Governor is initially the sole treasurer
         _addMinter(_governor);
-        _removeMinter(msg.sender); // Zep automagically does this, so remove...
 
-        // @imp 07 The Governer has the initial supply of tokens
-        _mint(_governor, _initialSupply); // Deployment address holds all tokens
+        // The Governor has the initial supply of tokens
+        _mint(_governor, _initialSupply);
     }
 
-    /**
-     * @dev Method to expose `removeToken` while using the `onlyGovernor` modifier
-     * @param _account <address> Address of account to remove from `_minters`
-     */
-    function removeMinter(address _account) public onlyGovernance {
+    function addMinter(address _account) external onlyGovernance {
+        _addMinter(_account);
+    }
+
+    function removeMinter(address _account) external onlyGovernance {
         _removeMinter(_account);
     }
 
+    function isMinter(address _account) public view returns (bool) {
+        return _minters[_account];
+    }
+
+    function renounceMinter() external {
+        _removeMinter(msg.sender);
+    }
+
+    function mint(address _account, uint256 _amount)
+        external
+        onlyMinter
+        returns (bool)
+    {
+        _mint(_account, _amount);
+        return true;
+    }
+
     /*
      * @dev Transfer Graph tokens to the Staking interface
      * @notice Interacts with Staking contract
@@ -93,4 +91,14 @@ contract GraphToken is
         assert(TokenReceiver(_to).tokensReceived(msg.sender, _amount, _data));
         success = true;
     }
+
+    function _addMinter(address _account) internal {
+        _minters[_account] = true;
+        emit MinterAdded(_account);
+    }
+
+    function _removeMinter(address _account) internal {
+        _minters[_account] = false;
+        emit MinterRemoved(_account);
+    }
 }

contracts/Migrations.sol

@@ -1,5 +1,4 @@
-pragma solidity ^0.5.2;
-
+pragma solidity ^0.6.4;
 
 contract Migrations {
     address public owner;

contracts/MultiSigWallet.sol

@@ -1,5 +1,4 @@
-pragma solidity ^0.5.2;
-
+pragma solidity ^0.6.4;
 
 // upgraded from solidity ^0.4.15 (Gnosis MultiSigWallet v1.3.7)
 
@@ -95,7 +94,7 @@ contract MultiSigWallet {
     }
 
     /// @dev Fallback function allows to deposit ether.
-    function() external payable {
+    fallback() external payable {
         if (msg.value > 0) emit Deposit(msg.sender, msg.value);
     }
 
@@ -143,7 +142,7 @@ contract MultiSigWallet {
                 owners[i] = owners[owners.length - 1];
                 break;
             }
-        owners.length -= 1;
+        owners.pop();
         if (required > owners.length) changeRequirement(owners.length);
         emit OwnerRemoval(owner);
     }
@@ -183,7 +182,7 @@ contract MultiSigWallet {
     /// @param destination Transaction target address.
     /// @param value Transaction ether value.
     /// @param data Transaction data payload.
-    /// @return Returns transaction ID.
+    /// @return transactionId Returns transaction ID.
     function submitTransaction(
         address destination,
         uint256 value,
@@ -257,7 +256,7 @@ contract MultiSigWallet {
             let x := mload(0x40) // "Allocate" memory for output (0x40 is where "free memory" pointer is stored by convention)
             let d := add(data, 32) // First 32 bytes are the padded length of data, so exclude that
             result := call(
-                sub(gas, 34710), // 34710 is the value that solidity is currently emitting
+                sub(gas(), 34710), // 34710 is the value that solidity is currently emitting
                 // It includes callGas (700) + callVeryLow (3, to pay for SUB) + callValueTransferGas (9000) +
                 // callNewAccountGas (25000, in case the destination address does not exist and needs creating)
                 destination,
@@ -289,7 +288,7 @@ contract MultiSigWallet {
     /// @param destination Transaction target address.
     /// @param value Transaction ether value.
     /// @param data Transaction data payload.
-    /// @return Returns transaction ID.
+    /// @return transactionId Returns transaction ID.
     function addTransaction(
         address destination,
         uint256 value,
@@ -311,7 +310,7 @@ contract MultiSigWallet {
      */
     /// @dev Returns number of confirmations of a transaction.
     /// @param transactionId Transaction ID.
-    /// @return Number of confirmations.
+    /// @return count Number of confirmations.
     function getConfirmationCount(uint256 transactionId)
         public
         view
@@ -324,7 +323,7 @@ contract MultiSigWallet {
     /// @dev Returns total number of transactions after filers are applied.
     /// @param pending Include pending transactions.
     /// @param executed Include executed transactions.
-    /// @return Total number of transactions after filters are applied.
+    /// @return count Total number of transactions after filters are applied.
     function getTransactionCount(bool pending, bool executed)
         public
         view
@@ -345,7 +344,7 @@ contract MultiSigWallet {
 
     /// @dev Returns array with owner addresses, which confirmed transaction.
     /// @param transactionId Transaction ID.
-    /// @return Returns array of owner addresses.
+    /// @return _confirmations Returns array of owner addresses.
     function getConfirmations(uint256 transactionId)
         public
         view
@@ -368,7 +367,7 @@ contract MultiSigWallet {
     /// @param to Index end position of transaction array.
     /// @param pending Include pending transactions.
     /// @param executed Include executed transactions.
-    /// @return Returns array of transaction IDs.
+    /// @return _transactionIds Returns array of transaction IDs.
     function getTransactionIds(
         uint256 from,
         uint256 to,

contracts/RewardsManager.sol

@@ -1,8 +1,7 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.6.4;
 
 import "./Governed.sol";
 
-
 contract RewardsManager is Governed {
     /*
      * @title Graph Protocol Reward Manager contract

contracts/ServiceRegistry.sol

@@ -1,8 +1,7 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.6.4;
 
 import "./Governed.sol";
 
-
 contract ServiceRegistry is Governed {
     /*
      * @title Graph Protocol Service Registry contract

contracts/Staking.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.6.4;
 
 /*
  * @title Staking contract