Bump minimum Solidity version to 0.5.7 (#1724)

* Bump Solidity version to 0.5.7

* Add changelog entry.

CHANGELOG.md

@@ -7,6 +7,9 @@
  implementers there. ([#1677](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1677))
  * `ERC777`: initial support for the [ERC777 token](https://eips.ethereum.org/EIPS/eip-777), which has multiple improvements over `ERC20` such as built-in burning, a more  straightforward permission system, and optional sender and receiver hooks on transfer (mandatory for contracts!). ([#1684](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1684))
 
+### Improvements:
+ * Upgraded the minimum compiler version to v0.5.7: this prevents users from encountering compiler bugs that were fixed in this version. ([#1724](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1724))
+
 ## 2.2.0 (2019-03-14)
 
 ### New features:

contracts/access/Roles.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 /**
  * @title Roles

contracts/access/roles/CapperRole.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../Roles.sol";
 

contracts/access/roles/MinterRole.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../Roles.sol";
 

contracts/access/roles/PauserRole.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../Roles.sol";
 

contracts/access/roles/SignerRole.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../Roles.sol";
 

contracts/access/roles/WhitelistAdminRole.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../Roles.sol";
 

contracts/access/roles/WhitelistedRole.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../Roles.sol";
 import "./WhitelistAdminRole.sol";

contracts/crowdsale/Crowdsale.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../token/ERC20/IERC20.sol";
 import "../math/SafeMath.sol";

contracts/crowdsale/distribution/FinalizableCrowdsale.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../../math/SafeMath.sol";
 import "../validation/TimedCrowdsale.sol";

contracts/crowdsale/distribution/PostDeliveryCrowdsale.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../validation/TimedCrowdsale.sol";
 import "../../math/SafeMath.sol";

contracts/crowdsale/distribution/RefundableCrowdsale.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../../math/SafeMath.sol";
 import "./FinalizableCrowdsale.sol";

contracts/crowdsale/distribution/RefundablePostDeliveryCrowdsale.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "./RefundableCrowdsale.sol";
 import "./PostDeliveryCrowdsale.sol";

contracts/crowdsale/emission/AllowanceCrowdsale.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../Crowdsale.sol";
 import "../../token/ERC20/IERC20.sol";

contracts/crowdsale/emission/MintedCrowdsale.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../Crowdsale.sol";
 import "../../token/ERC20/ERC20Mintable.sol";

contracts/crowdsale/price/IncreasingPriceCrowdsale.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../validation/TimedCrowdsale.sol";
 import "../../math/SafeMath.sol";

contracts/crowdsale/validation/CappedCrowdsale.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../../math/SafeMath.sol";
 import "../Crowdsale.sol";

contracts/crowdsale/validation/IndividuallyCappedCrowdsale.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../../math/SafeMath.sol";
 import "../Crowdsale.sol";

contracts/crowdsale/validation/PausableCrowdsale.sol

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

contracts/crowdsale/validation/TimedCrowdsale.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../../math/SafeMath.sol";
 import "../Crowdsale.sol";

contracts/crowdsale/validation/WhitelistCrowdsale.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 import "../Crowdsale.sol";
 import "../../access/roles/WhitelistedRole.sol";
 

contracts/cryptography/ECDSA.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 /**
  * @title Elliptic curve signature operations

contracts/cryptography/MerkleProof.sol

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

contracts/drafts/Counters.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../math/SafeMath.sol";
 

contracts/drafts/ERC1046/ERC20Metadata.sol

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

contracts/drafts/ERC1820Implementer.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "./IERC1820Implementer.sol";
 

contracts/drafts/ERC20Migrator.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../token/ERC20/IERC20.sol";
 import "../token/ERC20/ERC20Mintable.sol";

contracts/drafts/ERC20Snapshot.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../math/SafeMath.sol";
 import "../utils/Arrays.sol";

contracts/drafts/ERC777/ERC777.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "./IERC777.sol";
 import "./IERC777Recipient.sol";

contracts/drafts/ERC777/IERC777.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 /**
  * @title ERC777 token interface

contracts/drafts/ERC777/IERC777Recipient.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 /**
  * @title ERC777 token recipient interface

contracts/drafts/ERC777/IERC777Sender.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 /**
  * @title ERC777 token sender interface

contracts/drafts/IERC1820Implementer.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 /**
  * @title IERC1820Implementer

contracts/drafts/IERC1820Registry.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 /**
  * @title ERC1820 Pseudo-introspection Registry Contract

contracts/drafts/SignatureBouncer.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../access/roles/SignerRole.sol";
 import "../cryptography/ECDSA.sol";

contracts/drafts/SignedSafeMath.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 /**
  * @title SignedSafeMath

contracts/drafts/TokenVesting.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../token/ERC20/SafeERC20.sol";
 import "../ownership/Ownable.sol";

contracts/examples/SampleCrowdsale.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../crowdsale/validation/CappedCrowdsale.sol";
 import "../crowdsale/distribution/RefundableCrowdsale.sol";

contracts/examples/SimpleToken.sol

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

contracts/introspection/ERC165.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "./IERC165.sol";
 

contracts/introspection/ERC165Checker.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 /**
  * @title ERC165Checker

contracts/introspection/IERC165.sol

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

contracts/lifecycle/Pausable.sol

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

contracts/math/Math.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 /**
  * @title Math

contracts/math/SafeMath.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 /**
  * @title SafeMath

contracts/mocks/AddressImpl.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../utils/Address.sol";
 

contracts/mocks/AllowanceCrowdsaleImpl.sol

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

contracts/mocks/ArraysImpl.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../utils/Arrays.sol";
 

contracts/mocks/CappedCrowdsaleImpl.sol

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

contracts/mocks/CapperRoleMock.sol

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

contracts/mocks/ConditionalEscrowMock.sol

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

contracts/mocks/CountersImpl.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../drafts/Counters.sol";
 

contracts/mocks/CrowdsaleMock.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../crowdsale/Crowdsale.sol";
 

contracts/mocks/ECDSAMock.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../cryptography/ECDSA.sol";
 

contracts/mocks/ERC165/ERC165InterfacesSupported.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../../introspection/IERC165.sol";
 

contracts/mocks/ERC165/ERC165NotSupported.sol

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

contracts/mocks/ERC165CheckerMock.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../introspection/ERC165Checker.sol";
 

contracts/mocks/ERC165Mock.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../introspection/ERC165.sol";
 

contracts/mocks/ERC1820ImplementerMock.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../drafts/ERC1820Implementer.sol";
 

contracts/mocks/ERC20BurnableMock.sol

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

contracts/mocks/ERC20DetailedMock.sol

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

contracts/mocks/ERC20MetadataMock.sol

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

contracts/mocks/ERC20MintableMock.sol

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

contracts/mocks/ERC20Mock.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../token/ERC20/ERC20.sol";
 

contracts/mocks/ERC20PausableMock.sol

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

contracts/mocks/ERC20SnapshotMock.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../drafts/ERC20Snapshot.sol";
 

contracts/mocks/ERC721FullMock.sol

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

contracts/mocks/ERC721MintableBurnableImpl.sol

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

contracts/mocks/ERC721Mock.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../token/ERC721/ERC721.sol";
 

contracts/mocks/ERC721PausableMock.sol

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

contracts/mocks/ERC721ReceiverMock.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../token/ERC721/IERC721Receiver.sol";
 

contracts/mocks/ERC777Mock.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../drafts/ERC777/ERC777.sol";
 

contracts/mocks/ERC777SenderRecipientMock.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../drafts/ERC777/IERC777.sol";
 import "../drafts/ERC777/IERC777Sender.sol";

contracts/mocks/FinalizableCrowdsaleImpl.sol

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

contracts/mocks/IncreasingPriceCrowdsaleImpl.sol

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

contracts/mocks/IndividuallyCappedCrowdsaleImpl.sol

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

contracts/mocks/MathMock.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../math/Math.sol";
 

contracts/mocks/MerkleProofWrapper.sol

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

contracts/mocks/MintedCrowdsaleImpl.sol

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

contracts/mocks/MinterRoleMock.sol

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

contracts/mocks/OwnableInterfaceId.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../ownership/Ownable.sol";
 

contracts/mocks/OwnableMock.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../ownership/Ownable.sol";
 

contracts/mocks/PausableCrowdsaleImpl.sol

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

contracts/mocks/PausableMock.sol

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

contracts/mocks/PauserRoleMock.sol

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

contracts/mocks/PostDeliveryCrowdsaleImpl.sol

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

contracts/mocks/PullPaymentMock.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../payment/PullPayment.sol";
 

contracts/mocks/ReentrancyAttack.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 contract ReentrancyAttack {
     function callSender(bytes4 data) public {

contracts/mocks/ReentrancyMock.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../utils/ReentrancyGuard.sol";
 import "./ReentrancyAttack.sol";

contracts/mocks/RefundableCrowdsaleImpl.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../token/ERC20/IERC20.sol";
 import "../crowdsale/distribution/RefundableCrowdsale.sol";

contracts/mocks/RefundablePostDeliveryCrowdsaleImpl.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../token/ERC20/IERC20.sol";
 import "../crowdsale/distribution/RefundablePostDeliveryCrowdsale.sol";

contracts/mocks/RolesMock.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../access/Roles.sol";
 

contracts/mocks/SafeERC20Helper.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../token/ERC20/IERC20.sol";
 import "../token/ERC20/SafeERC20.sol";

contracts/mocks/SafeMathMock.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../math/SafeMath.sol";
 

contracts/mocks/SecondaryMock.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../ownership/Secondary.sol";
 

contracts/mocks/SignatureBouncerMock.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../drafts/SignatureBouncer.sol";
 import "./SignerRoleMock.sol";

contracts/mocks/SignedSafeMathMock.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../drafts/SignedSafeMath.sol";
 

contracts/mocks/SignerRoleMock.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../access/roles/SignerRole.sol";
 

contracts/mocks/TimedCrowdsaleImpl.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../token/ERC20/IERC20.sol";
 import "../crowdsale/validation/TimedCrowdsale.sol";

contracts/mocks/WhitelistAdminRoleMock.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../access/roles/WhitelistAdminRole.sol";
 

contracts/mocks/WhitelistCrowdsaleImpl.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../token/ERC20/IERC20.sol";
 import "../crowdsale/validation/WhitelistCrowdsale.sol";

contracts/mocks/WhitelistedRoleMock.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../access/roles/WhitelistedRole.sol";
 

contracts/ownership/Ownable.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 /**
  * @title Ownable

contracts/ownership/Secondary.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 /**
  * @title Secondary

contracts/payment/PaymentSplitter.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../math/SafeMath.sol";
 

contracts/payment/PullPayment.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "./escrow/Escrow.sol";
 

contracts/payment/escrow/ConditionalEscrow.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "./Escrow.sol";
 

contracts/payment/escrow/Escrow.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../../math/SafeMath.sol";
 import "../../ownership/Secondary.sol";

contracts/payment/escrow/RefundEscrow.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "./ConditionalEscrow.sol";
 

contracts/token/ERC20/ERC20.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "./IERC20.sol";
 import "../../math/SafeMath.sol";

contracts/token/ERC20/ERC20Burnable.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "./ERC20.sol";
 

contracts/token/ERC20/ERC20Capped.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "./ERC20Mintable.sol";
 

contracts/token/ERC20/ERC20Detailed.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "./IERC20.sol";
 

contracts/token/ERC20/ERC20Mintable.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "./ERC20.sol";
 import "../../access/roles/MinterRole.sol";

contracts/token/ERC20/ERC20Pausable.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "./ERC20.sol";
 import "../../lifecycle/Pausable.sol";

contracts/token/ERC20/IERC20.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 /**
  * @title ERC20 interface

contracts/token/ERC20/SafeERC20.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "./IERC20.sol";
 import "../../math/SafeMath.sol";

contracts/token/ERC20/TokenTimelock.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "./SafeERC20.sol";
 

contracts/token/ERC721/ERC721.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "./IERC721.sol";
 import "./IERC721Receiver.sol";
@@ -42,7 +42,7 @@ contract ERC721 is ERC165, IERC721 {
      *     bytes4(keccak256('transferFrom(address,address,uint256)')) == 0x23b872dd
      *     bytes4(keccak256('safeTransferFrom(address,address,uint256)')) == 0x42842e0e
      *     bytes4(keccak256('safeTransferFrom(address,address,uint256,bytes)')) == 0xb88d4fde
-     *    
+     *
      *     => 0x70a08231 ^ 0x6352211e ^ 0x095ea7b3 ^ 0x081812fc ^
      *        0xa22cb465 ^ 0xe985e9c ^ 0x23b872dd ^ 0x42842e0e ^ 0xb88d4fde == 0x80ac58cd
      */

contracts/token/ERC721/ERC721Burnable.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "./ERC721.sol";
 

contracts/token/ERC721/ERC721Enumerable.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "./IERC721Enumerable.sol";
 import "./ERC721.sol";
@@ -21,12 +21,12 @@ contract ERC721Enumerable is ERC165, ERC721, IERC721Enumerable {
     // Mapping from token id to position in the allTokens array
     mapping(uint256 => uint256) private _allTokensIndex;
 
-    /* 
+    /*
      *     bytes4(keccak256('totalSupply()')) == 0x18160ddd
      *     bytes4(keccak256('tokenOfOwnerByIndex(address,uint256)')) == 0x2f745c59
      *     bytes4(keccak256('tokenByIndex(uint256)')) == 0x4f6ccce7
-     *      
-     *     => 0x18160ddd ^ 0x2f745c59 ^ 0x4f6ccce7 == 0x780e9d63  
+     *
+     *     => 0x18160ddd ^ 0x2f745c59 ^ 0x4f6ccce7 == 0x780e9d63
      */
     bytes4 private constant _INTERFACE_ID_ERC721_ENUMERABLE = 0x780e9d63;
 

contracts/token/ERC721/ERC721Full.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "./ERC721.sol";
 import "./ERC721Enumerable.sol";

contracts/token/ERC721/ERC721Holder.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "./IERC721Receiver.sol";
 

contracts/token/ERC721/ERC721Metadata.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "./ERC721.sol";
 import "./IERC721Metadata.sol";
@@ -18,7 +18,7 @@ contract ERC721Metadata is ERC165, ERC721, IERC721Metadata {
      *     bytes4(keccak256('name()')) == 0x06fdde03
      *     bytes4(keccak256('symbol()')) == 0x95d89b41
      *     bytes4(keccak256('tokenURI(uint256)')) == 0xc87b56dd
-     *     
+     *
      *     => 0x06fdde03 ^ 0x95d89b41 ^ 0xc87b56dd == 0x5b5e139f
      */
     bytes4 private constant _INTERFACE_ID_ERC721_METADATA = 0x5b5e139f;

contracts/token/ERC721/ERC721MetadataMintable.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "./ERC721Metadata.sol";
 import "../../access/roles/MinterRole.sol";

contracts/token/ERC721/ERC721Mintable.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "./ERC721.sol";
 import "../../access/roles/MinterRole.sol";

contracts/token/ERC721/ERC721Pausable.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "./ERC721.sol";
 import "../../lifecycle/Pausable.sol";

contracts/token/ERC721/IERC721.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../../introspection/IERC165.sol";
 

contracts/token/ERC721/IERC721Enumerable.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "./IERC721.sol";
 

contracts/token/ERC721/IERC721Full.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "./IERC721.sol";
 import "./IERC721Enumerable.sol";

contracts/token/ERC721/IERC721Metadata.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "./IERC721.sol";
 

contracts/token/ERC721/IERC721Receiver.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 /**
  * @title ERC721 token receiver interface

contracts/utils/Address.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 /**
  * Utility library of inline functions on addresses

contracts/utils/Arrays.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 import "../math/Math.sol";
 

contracts/utils/ReentrancyGuard.sol

-pragma solidity ^0.5.2;
+pragma solidity ^0.5.7;
 
 /**
  * @title Helps contracts guard against reentrancy attacks.

truffle-config.js

@@ -18,7 +18,7 @@ module.exports = {
 
   compilers: {
     solc: {
-      version: '0.5.2',
+      version: '0.5.7',
     },
   },
 };