delegation: support self ty propagation for functions in free to trait reuse
This PR adds support for self types specified in free to trait reuse. Up to this point we always generated `Self` despite the fact whether self type was specified or not. Now we use it in signature inheritance. Moreover we no more generate `Self` for static methods. Part of rust-lang/rust#118212.
```rust
trait Trait<T> {
fn foo<const B: bool>(&self) {}
fn bar() {}
}
impl<T> Trait<T> for usize {}
reuse <usize as Trait>::foo;
// Desugaring (no `Self` as usize is specified)
fn foo<T, const B: bool>(self: &usize) {
<usize as Trait::<T>>::foo::<B>(self)
}
reuse Trait::bar;
// Desugaring (no `Self` as static method)
fn bar<T>() {
Trait::<T>::bar(); //~ERROR: type annotations needed
}
```
r? @petrochenkov
Guillaume Gomez
aebbe6bb5f