Incorrect trait bounds check

[ivan770]

I tried this code:
https://play.rust-lang.org/?version=nightly&mode=debug&edition=2018&gist=d372b241527aa63df526377bfc532b31

I expected to see this happen: It compiles or gives me a detailed error.

Instead, this happened: Compiler suggests to add an already existing trait bound. Adding it one more time leads to compiler suggesting adding it once more and so on.

While the code example uses GAT and TAIT, I'm not entirely sure both of those features are required to reproduce the issue.

@rustbot label +T-compiler +F-type_alias_impl_trait +F-generic_associated_types +A-traits +requires-nightly

[JohnTitor]

This compiles fine on the latest nightly, perhaps related to #88405.