Create2 feature pending tasks (OpenZeppelin#2013)

* Add Create2 library (OpenZeppelin#1744)

* feat(contracts): Add Create2 library to use create2 evm opcode

* Upgrade sol-coverage

* Add changelog entry

* Update comments and code style

* Remove create2 helper

* Fix linter error

* Fix truffle dependency

* Fix linter error

* refactor(Create2): Remove _deploy internal function

* test(Create2): test Create2 with inline assembly code

* fix(Create2): Check address returned form create2 instead of codesize of created contract

* refactor(Create2):Add revert reason when Create2 deploy fails (OpenZeppelin#2062)

* fix merge with master

* fix test

Co-authored-by: Augusto Lemble <me@augustol.com>

.solcover.js

@@ -3,7 +3,6 @@ module.exports = {
     testCommand: 'npm test',
     compileCommand: 'npm run compile',
     skipFiles: [
-        'lifecycle/Migrations.sol',
-        'mocks'
+        'mocks',
     ]
 }

CHANGELOG.md

@@ -5,6 +5,7 @@
 ### New features
  * `SafeCast.toUintXX`: new library for integer downcasting, which allows for safe operation on smaller types (e.g. `uint32`) when combined with `SafeMath`. ([#1926](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1926))
  * `ERC721Metadata`: added `baseURI`, which can be used for dramatic gas savings when all token URIs share a prefix (e.g. `http://api.myapp.com/tokens/<id>`). ([#1970](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1970))
+ * `Create2`: simple library to make usage of the `CREATE2` opcode easier. ([#1744](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/1744))
 
 ### Improvements
  * `ERC777`: `_burn` is now internal, providing more flexibility and making it easier to create tokens that deflate. ([#1908](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/1908))

contracts/mocks/Create2Impl.sol

@@ -0,0 +1,23 @@
+pragma solidity ^0.5.0;
+
+import "../utils/Create2.sol";
+import "../token/ERC20/ERC20.sol";
+
+contract Create2Impl {
+    function deploy(bytes32 salt, bytes memory code) public {
+        Create2.deploy(salt, code);
+    }
+
+    function deployERC20(bytes32 salt) public {
+        // solhint-disable-next-line indent
+        Create2.deploy(salt, type(ERC20).creationCode);
+    }
+
+    function computeAddress(bytes32 salt, bytes memory code) public view returns (address) {
+        return Create2.computeAddress(salt, code);
+    }
+
+    function computeAddress(bytes32 salt, bytes memory code, address deployer) public pure returns (address) {
+        return Create2.computeAddress(salt, code, deployer);
+    }
+}

contracts/utils/Create2.sol

@@ -0,0 +1,47 @@
+pragma solidity ^0.5.0;
+
+/**
+ * @dev Helper to make usage of the `CREATE2` EVM opcode easier and safer.
+ * `CREATE2` can be used to compute in advance the address where a smart
+ * contract will be deployed, which allows for interesting new mechanisms known
+ * as 'counterfactual interactions'.
+ *
+ * See the https://eips.ethereum.org/EIPS/eip-1014#motivation[EIP] for more
+ * information.
+ */
+library Create2 {
+    /**
+     * @dev Deploys a contract using `CREATE2`. The address where the contract
+     * will be deployed can be known in advance via {computeAddress}. Note that
+     * a contract cannot be deployed twice using the same salt.
+     */
+    function deploy(bytes32 salt, bytes memory bytecode) internal returns (address) {
+        address addr;
+        // solhint-disable-next-line no-inline-assembly
+        assembly {
+            addr := create2(0, add(bytecode, 0x20), mload(bytecode), salt)
+        }
+        require(addr != address(0), "Create2: Failed on deploy");
+        return addr;
+    }
+
+    /**
+     * @dev Returns the address where a contract will be stored if deployed via {deploy}. Any change in the `bytecode`
+     * or `salt` will result in a new destination address.
+     */
+    function computeAddress(bytes32 salt, bytes memory bytecode) internal view returns (address) {
+        return computeAddress(salt, bytecode, address(this));
+    }
+
+    /**
+     * @dev Returns the address where a contract will be stored if deployed via {deploy} from a contract located at
+     * `deployer`. If `deployer` is this contract's address, returns the same value as {computeAddress}.
+     */
+    function computeAddress(bytes32 salt, bytes memory bytecodeHash, address deployer) internal pure returns (address) {
+        bytes32 bytecodeHashHash = keccak256(bytecodeHash);
+        bytes32 _data = keccak256(
+            abi.encodePacked(bytes1(0xff), deployer, salt, bytecodeHashHash)
+        );
+        return address(bytes20(_data << 96));
+    }
+}

contracts/utils/README.adoc

@@ -10,4 +10,6 @@ Miscellaneous contracts containing utility functions, often related to working w
 
 {{Arrays}}
 
+{{Create2}}
+
 {{ReentrancyGuard}}

test/utils/Create2.test.js

@@ -0,0 +1,71 @@
+const { contract, accounts, web3 } = require('@openzeppelin/test-environment');
+const { BN, expectRevert } = require('@openzeppelin/test-helpers');
+
+const { expect } = require('chai');
+
+const Create2Impl = contract.fromArtifact('Create2Impl');
+const ERC20Mock = contract.fromArtifact('ERC20Mock');
+const ERC20 = contract.fromArtifact('ERC20');
+
+describe('Create2', function () {
+  const [deployerAccount] = accounts;
+
+  const salt = 'salt message';
+  const saltHex = web3.utils.soliditySha3(salt);
+  const constructorByteCode = `${ERC20Mock.bytecode}${web3.eth.abi
+    .encodeParameters(['address', 'uint256'], [deployerAccount, 100]).slice(2)
+  }`;
+
+  beforeEach(async function () {
+    this.factory = await Create2Impl.new();
+  });
+
+  it('should compute the correct contract address', async function () {
+    const onChainComputed = await this.factory
+      .computeAddress(saltHex, constructorByteCode);
+    const offChainComputed =
+      computeCreate2Address(saltHex, constructorByteCode, this.factory.address);
+    expect(onChainComputed).to.equal(offChainComputed);
+  });
+
+  it('should compute the correct contract address with deployer', async function () {
+    const onChainComputed = await this.factory
+      .computeAddress(saltHex, constructorByteCode, deployerAccount);
+    const offChainComputed =
+      computeCreate2Address(saltHex, constructorByteCode, deployerAccount);
+    expect(onChainComputed).to.equal(offChainComputed);
+  });
+
+  it('should deploy a ERC20 from inline assembly code', async function () {
+    const offChainComputed =
+      computeCreate2Address(saltHex, ERC20.bytecode, this.factory.address);
+    await this.factory
+      .deploy(saltHex, ERC20.bytecode, { from: deployerAccount });
+    expect(ERC20.bytecode).to.include((await web3.eth.getCode(offChainComputed)).slice(2));
+  });
+
+  it('should deploy a ERC20Mock with correct balances', async function () {
+    const offChainComputed =
+      computeCreate2Address(saltHex, constructorByteCode, this.factory.address);
+    await this.factory
+      .deploy(saltHex, constructorByteCode, { from: deployerAccount });
+    const erc20 = await ERC20Mock.at(offChainComputed);
+    expect(await erc20.balanceOf(deployerAccount)).to.be.bignumber.equal(new BN(100));
+  });
+
+  it('should failed deploying a contract in an existent address', async function () {
+    await this.factory.deploy(saltHex, constructorByteCode, { from: deployerAccount });
+    await expectRevert(
+      this.factory.deploy(saltHex, constructorByteCode, { from: deployerAccount }), 'Create2: Failed on deploy'
+    );
+  });
+});
+
+function computeCreate2Address (saltHex, bytecode, deployer) {
+  return web3.utils.toChecksumAddress(`0x${web3.utils.sha3(`0x${[
+    'ff',
+    deployer,
+    saltHex,
+    web3.utils.soliditySha3(bytecode),
+  ].map(x => x.replace(/0x/, '')).join('')}`).slice(-40)}`);
+}