"type annotations needed" when duplicated where-clauses use different lifetime parameters

[jonas-schievink]

The following code should compile, but it seems to confuse the compiler and results in a very poor error message:

fn f<'a, 'b, T>()
where
    &'a T: Copy,
    &'b T: Copy,
{
}

error[E0283]: type annotations needed
   --> src/lib.rs:3:12
    |
3   |       &'a T: Copy,
    |              ^^^^ cannot infer type for reference `&'a T`
    |
    = note: cannot satisfy `&'a T: std::marker::Copy`

There should not be any type inference happening in the where-clause, so getting this error is fairly absurd.

Same thing happens with other traits than Copy, and also with concrete types like () instead of a type parameter T.

[jonas-schievink]

Duplicate of #34979