Self as generic trait parameter is not properly ignored by Self: Sized bound

[izagawd]

This Compiles

struct Foo;
trait Bar{
    fn some_method(&self) -> impl SomeTrait where Self: Sized;
}
trait SomeTrait{}
fn main() {
    let obj : &dyn Bar;
}

This Also Compiles

struct Foo;
trait Bar{
    fn some_method(&self) -> &dyn SomeTrait<Self> where Self: Sized;
}
trait SomeTrait<T>{}
fn main() {
    let obj : &dyn Bar;
}

But This..

struct Foo;
trait Bar{
    fn some_method(&self) -> impl SomeTrait<Self> where Self: Sized;
}
trait SomeTrait<T>{}
fn main() {
    let obj : &dyn Bar;
}

Show This Error output

error[E0038]: the trait `Bar` is not dyn compatible
 --> src\main.rs:7:15
  |
7 |     let obj : &dyn Bar;
  |               ^^^^^^^^ `Bar` is not dyn compatible
  |
note: for a trait to be dyn compatible it needs to allow building a vtable
      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#dyn-compatibility>
 --> src\main.rs:3:35
  |
2 | trait Bar{
  |       --- this trait is not dyn compatible...
3 |     fn some_method(&self) -> impl SomeTrait<Self> where Self: Sized;
  |                                   ^^^^^^^^^^^^^^^ ...because it uses `Self` as a type parameter

Even though Self : Sized. This should be valid in rust.

version:
rustc 1.86.0-nightly (a567209 2025-02-13)

[konnorandrews]

@rustbot modify labels: -I-ICE

[konnorandrews]

Here is a smaller example without RPITIT.

struct X(&'static dyn A);

trait A {
    type T: B<Self> where Self: Sized;
}

trait B<T> {}

...
3 | trait A {
  |       - this trait cannot be made into an object...
4 |     type T: B<Self> where Self: Sized;
  |             ^^^^^^^ ...because it uses `Self` as a type parameter