Prevent coercion before distributed slice typecheck #83
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Fixes #82
We use a
fn() -> &T
to prevent value coercions from applying. This does allow contravariant coercion to a subtype (a shorter lifetime), but I believe that since#ty
is in astatic
(cannot contain lifetimes other than the top lifetime'static
) that this is not an exploitable hole. If a hole remains, it's probably to do withfor<'a>
lifetime binders.I did test a few methods that fully constrain
T
to be invariant (e.g.fn(T) -> T
), but they all worsened the error messages more than this does, and this appears to be sufficient.