If we find a blanket impl for `Trait` but we're matching on an object `Trait`, prefer the object (I think we could perhaps go either way, but this seems safer). Also give a nice error for attempts to manually `impl Trait for Trait`, since they will be ineffectual.
This fixes the problems around ambiguity ICEs relating to `Any` and `MarkerTrait` that were cropping up all over the place. There may still be similar ICEs reported in #21756 that this PR does not address.
Fixes #24015.
Fixes #24051.
Fixes #24037.
Fixes #23853.
Fixes #21942.
cc #21756.
cc @alexcrichton (this fixes crates.io)
r? @aturon
projects / rust.git / commitdiff