Component

Forge

Describe the feature you would like

I'd like to propose a new lint rule called UnsafeTypecast for forge lint. This rule should flag any downcast or semantically unsafe typecast as unsafe by default.

This includes:

• Numeric downcasts (e.g., uint128 → uint64, int256 → int8, uint256 → int256)
• Non-numeric downcasts (e.g., bytes → bytes32)

These casts can lead to data loss, overflow, or incorrect interpretation and should always be treated with caution.

The expected usage is that developers disable the lint explicitly using // forge-lint: disable-next-line(UnsafeTypecast), and include a separate explanatory comment justifying why the cast is safe.

For example:

if (a > type(uint32).max) revert TypecastOverflow();

// ...

// forge-lint: disable-next-line(UnsafeTypecast)
uint32 b = uint32(a); // We ensure `a` can fit in 32 bits above.

Additional context

No response