Duplicate addresses for distinct newly created contracts.

[jzaki]

Inside test functions setup() or a test...(), it is possible for two contracts to be created with the same address. Specifically between a contract created in a constructor, and a contract created in a function.
Example:

contract AContract {}


contract Collection {
    event Addresses(address, string);

    constructor() public {
        emit Addresses(new AContract(), "new in constructor");
    }
    
    function createFunction() public {
        emit Addresses(new AContract(), "new in function");
    }
}


contract AddressbugTest is DSTest {

    function setUp() public {
        Collection collection = new Collection();
        collection.createFunction();
    }

    function testBasicSanity() public {
        assertTrue(false);
    }

}

dapp test output:

src/Addressbug.t.sol:AddressbugTest
   ├╴constructor
   ├╴initialize test
   │  ├╴create Collection (src/Addressbug.t.sol:27)
   │  │  ├╴create AContract (src/Addressbug.t.sol:15)
   │  │  └╴Addresses(0x99db7a7dcb7726ec5d29d08d50685dd8d8843915, "new in constructor") (src/Addressbug.t.sol:15)
   │  └╴call Collection::createFunction()() (src/Addressbug.t.sol:28)
   │     ├╴create AContract (src/Addressbug.t.sol:19)
   │     └╴Addresses(0x99db7a7dcb7726ec5d29d08d50685dd8d8843915, "new in function") (src/Addressbug.t.sol:19)
   └╴testBasicSanity()
      └╴log_bytes32("Assertion failed") (lib/ds-test/src/test.sol:56)

Both addresses: 0x99db7a7dcb7726ec5d29d08d50685dd8d8843915

Expected different addresses.
Eg remix:

[
	{
		"from": "0x9303a10f5aee3a50aff33807f78c0e7264be20b8",
		"topic": "0x1536377df3f3504a004885fa2e8057b751df91abe9e49f1d13ec79cc4e1193c1",
		"event": "Addresses",
		"args": {
			"0": "0x4c8bF2546Cdc9CBfd00a1121a7b2730b3e3249eC",
			"1": "new in constructor",
			"length": 2
		}
	},
	{
		"from": "0x9303a10f5aee3a50aff33807f78c0e7264be20b8",
		"topic": "0x1536377df3f3504a004885fa2e8057b751df91abe9e49f1d13ec79cc4e1193c1",
		"event": "Addresses",
		"args": {
			"0": "0x5B14f277cCdc89905e2a2A93d69A478722e58037",
			"1": "new in function",
			"length": 2
		}
	}
]

Possibly useful summary of constructed contract addresses:

The address for an Ethereum contract is deterministically computed from the address of its creator (sender) and how many transactions the creator has sent (nonce). The sender and nonce are RLP encoded and then hashed with Keccak-256.

source

Possibly partially related: #40

[mbrock]

Thanks for the report. I've fixed the bug on master.

[asymmetric]

For posterity: it was fixed in 070cc9e 😊