Component

Forge

Describe the feature you would like

Often it's desirable to check properties of results, such as a new price of an AMM. However, these functions can contain error-checks and revert on certain inputs. And sometimes I want to make sure a property holds only if I actually get a result from a call and ignore the reverting cases.

An example of what this could look like is:

    function test_getPrice_invariant(uint256 x, uint256 dx) public {
        dx = bound(dx, 0, type(uint256).max - x);

        vm.canRevert(Overflow.selector);
        uint256 y1 = amm.getPrice(x);

        vm.canRevert(Overflow.selector);
        uint256 y2 = amm.getPrice(x + dx);
        
        assertGte(y2, y1);
    }

A current workaround is to use low-level calls or try ... catch ..., but these have to be set up for each function manually.

    function getPrice_canRevert(uint256 x, bytes4 selector) internal returns (uint256) {
        try amm.getPrice(x) returns (uint256 price) {
            return price;
        } catch (bytes memory reason) {
            require(bytes4(reason) == selector, "unexpected revert");
        }
    }

An implementation of vm.canRevert/vm.allowRevert could add to the counter of vm.assume checks to make sure that one isn't rejecting all calls.

Additional context

No response