Associated type not resolved based on lifetimes

[programmerjake]

I tried this code:
https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=d9dd02dbc642c719d6a984f0e4dd91fb

pub trait Trait<'a> {
    type Type;
}

pub fn f<'a, 'b, T: Trait<'a> + Trait<'b>>(v: <T as Trait<'a>>::Type) {
    
}

I expected to see this happen: compile without errors.

Instead, this happened:

   Compiling playground v0.0.1 (/playground)
error[E0284]: type annotations needed: cannot satisfy `<T as Trait<'a>>::Type == _`
 --> src/lib.rs:5:1
  |
5 | / pub fn f<'a, 'b, T: Trait<'a> + Trait<'b>>(v: <T as Trait<'a>>::Type) {
6 | |     
7 | | }
  | |_^ cannot satisfy `<T as Trait<'a>>::Type == _`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0284`.
error: could not compile `playground`

To learn more, run the command again with --verbose.

related: https://users.rust-lang.org/t/compile-failing-even-though-it-seems-like-it-should-work/62409?u=programmerjake

[jackh726]

Possibly fixed by #85499 (but is the same cause)

[BGR360]

Could it be related to this old gem? #21974