Invariants: Allow `targetContract(address(this));` for contracts that use targetFunctions

[GalloDaSballo]

Component

Forge

Describe the feature you would like

Feature Request

Allow the usage of targetContract(address(this)); for Invariant Testing

Example

Allow:

https://github.com/Recon-Fuzz/create-chimera-app/blob/0294f60d1f31013923cbe2a0fd92c74e2b359a5e/test/recon/CryticToFoundry.sol#L13-L19

contract CryticToFoundry is Test, TargetFunctions, FoundryAsserts {
    function setUp() public {
        setup();

        targetContract(address(this));
    }

to work

Example Repro: https://github.com/GalloDaSballo/foundry-targetContract-repro

Context

An extremely common way of writing invariant tests uses Target Function, explicit functions that tell the fuzzer how to explore state

Source:
https://github.com/Recon-Fuzz/create-chimera-app (Recon)
https://github.com/perimetersec/arachne (PerimeterSec)
https://github.com/euler-xyz/euler-vault-kit/tree/master/src (Enigma Dark)
https://github.com/CodeHawks-Contests/2025-02-gamma/blob/main/test/fuzzing/echidna/CryticToFoundry.sol (Guardian Audits)

As it stands targetFunctions doesn't allow passing address(this)

This prevents these testing suites from being easily reusable with Foundry

Current logs:

Encountered 2 failing tests in test/recon/CryticToFoundry.sol:CryticToFoundry
[FAIL: failed to set up invariant testing environment: No contracts to fuzz.] invariant_count_never_gt_0() (runs: 0, calls: 0, reverts: 0)
[FAIL: failed to set up invariant testing environment: No contracts to fuzz.] invariant_number_never_zero() (runs: 0, calls: 0, reverts: 0)

Request

Allow us to pass targetContract(address(this)); which will allow us to use the same suite with no changes

Additional context

No response