Recursive generic function with std::fmt::Borrow bound expects the same generic type for recursive call

[timvermeulen]

fn f<T: ?Sized>(_: &T)
where
    String: std::borrow::Borrow<T>,
{
    // doesn't compile:
    f("");
    
    // compiles:
    f::<str>("");
}

error[E0308]: mismatched types
 --> src/lib.rs:6:7
  |
6 |     f("");
  |       ^^ expected type parameter, found str
  |
  = note: expected type `&T`
             found type `&'static str`

[ExpHP]

See #24066

[Enselic]

Triage: Closing as duplicate of #24066 because the root cause is likely the same.