Fix negative traits coherence checks compile error message for type aliases #90259
Description
Follow up of this comment on #90104
This test https://github.com/rust-lang/rust/pull/90104/files#diff-2c291b05493bf924a05c167ef3923655ca244b6fd8bc2303ffdc2ed2132498cc is giving an ungreat error message.
#![feature(rustc_attrs)] #![feature(trait_alias)] trait A {} trait B {} trait AB = A + B; impl A for u32 {} impl B for u32 {} trait C {} #[rustc_strict_coherence] impl<T: AB> C for T {} #[rustc_strict_coherence] impl C for u32 {} //~^ ERROR // FIXME it's giving an ungreat error but unsure if we care given that it's using an internal rustc // attribute and an artificial code path for testing purposes fn main() {}fails with ...
error[E0283]: type annotations needed --> $DIR/coherence-overlap-trait-alias.rs:15:6 | LL | impl C for u32 {} | ^ cannot infer type for type `u32` | = note: cannot satisfy `u32: C` note: required by a bound in `C` --> $DIR/coherence-overlap-trait-alias.rs:11:1 | LL | trait C {} | ^^^^^^^ required by this bound in `C` error: aborting due to previous error Error should mention about conflicting implementations for u32 or something like that. More similar to what happens without using the rustc_strict_coherence attribute.