Postmonomorphism Asserts and Bound Hiding

[SkiFire13]

@soundlogic2236

That is to say, make it so a block of code can add extra bounds which are not 'exposed', and are only checked post-monomorphism.

This is not sound for the same reason as why specialization is not sound: lifetimes are erased post-monomorphization, but are needed to properly check bounds. In fact, the following use of the specialization feature is unsound.

@soundlogic2236

    trait TryProof {
        type Result: DebugProof<Self> + MaybeConjureProof + Copy;
    }

    impl<T: ?Sized> TryProof for T {
        default type Result = !;
    }
    impl<T: ?Sized + std::fmt::Debug> TryProof for T {
        type Result = ();
    }

Here's how this can be exploited Rust Playground