Unknown placeholder inlayHints in path segment

[A4-Tacks]

rust-analyzer version: rust-analyzer 0.4.2710-standalone

rustc version: rustc 1.91.0-nightly (040a98a 2025-08-20)

editor or extension: Vim

code snippet to reproduce:

fn main() {
    Foo::<_>::convert(2);
}
struct Foo<T>(T);

impl<T> Convert<T> for Foo<T> {
    fn convert(_: T) -> Self {
        loop { }
    }
}
trait Convert<T> {
    fn convert(value: T) -> Self;
}

Output:

Foo::<_ = {unknown}>::convert(2);

[ChayimFriedman2]

I believe the problem is that not in all places we lower types we look for placeholders and insert them into the map.

The real fix is to tie together the TyLoweringContext and the InferenceContext, required anyway for const generics.