Update linter

.solhint.json

@@ -9,6 +9,7 @@
     "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

@@ -14,7 +14,6 @@ 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 virtual returns (address payable) {
         return msg.sender;

contracts/GSN/GSNRecipientERC20Fee.sol

@@ -115,9 +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 {

contracts/GSN/GSNRecipientSignature.sol

@@ -64,11 +64,7 @@ contract GSNRecipientSignature is GSNRecipient {
         }
     }
 
-    function _preRelayedCall(bytes memory) internal virtual override 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 virtual override {
-        // solhint-disable-previous-line no-empty-blocks
-    }
+    function _postRelayedCall(bytes memory, bool, uint256, bytes32) internal virtual override { }
 }

contracts/mocks/AddressImpl.sol

@@ -15,5 +15,6 @@ contract AddressImpl {
         Address.sendValue(receiver, amount);
     }
 
-    receive () 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/CapperRoleMock.sol

@@ -7,7 +7,5 @@ contract CapperRoleMock is CapperRole {
         _removeCapper(account);
     }
 
-    function onlyCapperMock() public view onlyCapper {
-        // solhint-disable-previous-line no-empty-blocks
-    }
+    function onlyCapperMock() public view onlyCapper { }
 }

contracts/mocks/ERC165/ERC165NotSupported.sol

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

contracts/mocks/ERC20DetailedMock.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

@@ -4,9 +4,7 @@ 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

@@ -3,6 +3,4 @@ pragma solidity ^0.6.0;
 import "../token/ERC20/ERC20Mintable.sol";
 import "./MinterRoleMock.sol";
 
-contract ERC20MintableMock is ERC20Mintable, MinterRoleMock {
-    // solhint-disable-previous-line no-empty-blocks
-}
+contract ERC20MintableMock is ERC20Mintable, MinterRoleMock { }

contracts/mocks/ERC721FullMock.sol

@@ -11,9 +11,7 @@ import "../token/ERC721/ERC721Burnable.sol";
  * 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
-    }
+    constructor (string memory name, string memory symbol) public ERC721Mintable() ERC721Full(name, symbol) { }
 
     function exists(uint256 tokenId) public view returns (bool) {
         return _exists(tokenId);

contracts/mocks/ERC721GSNRecipientMock.sol

@@ -10,7 +10,6 @@ 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);

contracts/mocks/ERC721MintableBurnableImpl.sol

@@ -9,9 +9,7 @@ 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
-    }
+    constructor () public ERC721Mintable() ERC721Full("Test", "TEST") { }
 
     function _afterTokenTransfer(address from, address to, uint256 tokenId) internal virtual override(ERC721, ERC721Full, ERC721Metadata) {
         super._afterTokenTransfer(from, to, tokenId);

contracts/mocks/GSNRecipientERC20FeeMock.sol

@@ -4,9 +4,7 @@ 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

@@ -18,13 +18,9 @@ contract GSNRecipientMock is ContextMock, GSNRecipient {
         return (0, "");
     }
 
-    function _preRelayedCall(bytes memory) internal override 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 override {
-        // solhint-disable-previous-line no-empty-blocks
-    }
+    function _postRelayedCall(bytes memory, bool, uint256, bytes32) internal override { }
 
     function upgradeRelayHub(address newRelayHub) public {
         return _upgradeRelayHub(newRelayHub);

contracts/mocks/GSNRecipientSignatureMock.sol

@@ -4,9 +4,7 @@ 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/MinterRoleMock.sol

@@ -7,7 +7,5 @@ contract MinterRoleMock is MinterRole {
         _removeMinter(account);
     }
 
-    function onlyMinterMock() public view onlyMinter {
-        // solhint-disable-previous-line no-empty-blocks
-    }
+    function onlyMinterMock() public view onlyMinter { }
 }

contracts/mocks/OwnableMock.sol

@@ -2,6 +2,4 @@ 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/PauserRoleMock.sol

@@ -7,7 +7,5 @@ contract PauserRoleMock is PauserRole {
         _removePauser(account);
     }
 
-    function onlyPauserMock() public view onlyPauser {
-        // solhint-disable-previous-line no-empty-blocks
-    }
+    function onlyPauserMock() public view onlyPauser { }
 }

contracts/mocks/PullPaymentMock.sol

@@ -4,9 +4,7 @@ import "../payment/PullPayment.sol";
 
 // mock class using PullPayment
 contract PullPaymentMock is PullPayment {
-    constructor () public payable {
-        // solhint-disable-previous-line no-empty-blocks
-    }
+    constructor () public payable { }
 
     // test helper function to call asyncTransfer
     function callTransfer(address dest, uint256 amount) public {

contracts/mocks/SecondaryMock.sol

@@ -3,7 +3,5 @@ pragma solidity ^0.6.0;
 import "../ownership/Secondary.sol";
 
 contract SecondaryMock is Secondary {
-    function onlyPrimaryMock() public view onlyPrimary {
-        // solhint-disable-previous-line no-empty-blocks
-    }
+    function onlyPrimaryMock() public view onlyPrimary { }
 }

contracts/mocks/SignerRoleMock.sol

@@ -7,7 +7,5 @@ contract SignerRoleMock is SignerRole {
         _removeSigner(account);
     }
 
-    function onlySignerMock() public view onlySigner {
-        // solhint-disable-previous-line no-empty-blocks
-    }
+    function onlySignerMock() public view onlySigner { }
 }

contracts/mocks/WhitelistAdminRoleMock.sol

@@ -7,7 +7,5 @@ contract WhitelistAdminRoleMock is WhitelistAdminRole {
         _removeWhitelistAdmin(account);
     }
 
-    function onlyWhitelistAdminMock() public view onlyWhitelistAdmin {
-        // solhint-disable-previous-line no-empty-blocks
-    }
+    function onlyWhitelistAdminMock() public view onlyWhitelistAdmin { }
 }

contracts/mocks/WhitelistedRoleMock.sol

@@ -3,7 +3,5 @@ pragma solidity ^0.6.0;
 import "../access/roles/WhitelistedRole.sol";
 
 contract WhitelistedRoleMock is WhitelistedRole {
-    function onlyWhitelistedMock() public view onlyWhitelisted {
-        // solhint-disable-previous-line no-empty-blocks
-    }
+    function onlyWhitelistedMock() public view onlyWhitelisted { }
 }

contracts/token/ERC721/ERC721Full.sol

@@ -11,9 +11,7 @@ import "./ERC721Metadata.sol";
  * See https://eips.ethereum.org/EIPS/eip-721
  */
 contract ERC721Full is ERC721Enumerable, ERC721Metadata {
-    constructor (string memory name, string memory symbol) public ERC721Metadata(name, symbol) {
-        // solhint-disable-previous-line no-empty-blocks
-    }
+    constructor (string memory name, string memory symbol) public ERC721Metadata(name, symbol) { }
 
     function _afterTokenTransfer(address from, address to, uint256 tokenId)
         virtual

contracts/token/ERC721/IERC721Full.sol

@@ -8,6 +8,4 @@ import "./IERC721Metadata.sol";
  * @title ERC-721 Non-Fungible Token Standard, full implementation interface
  * @dev See https://eips.ethereum.org/EIPS/eip-721
  */
-abstract contract IERC721Full is IERC721, IERC721Enumerable, IERC721Metadata {
-    // solhint-disable-previous-line no-empty-blocks
-}
+abstract contract IERC721Full is IERC721, IERC721Enumerable, IERC721Metadata { }

contracts/utils/Address.sol

@@ -63,7 +63,7 @@ library Address {
     function sendValue(address payable recipient, uint256 amount) internal {
         require(address(this).balance >= amount, "Address: insufficient balance");
 
-        // solhint-disable-next-line avoid-call-value
+        // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
         (bool success, ) = recipient.call.value(amount)("");
         require(success, "Address: unable to send value, recipient may have reverted");
     }