query cycle: specialisation `cycle detected when building specialization graph of trait`

Code

#![feature(specialization)]

trait Trait<T> {
    type Assoc;
}

impl<T> Trait<T> for Vec<T> {}

impl Trait<u8> for Vec<u32> {
    type Assoc = u8;
}

impl<T> Trait<T> for String {
    type Assoc = ();
}

impl Trait<<Vec<u8> as Trait<u8>>::Assoc> for String {}

fn main() {}

Current output

warning: the feature `specialization` is incomplete and may not be safe to use and/or cause compiler crashes
 --> 43273EB829A15349E16F5931020795BF70C210EEDA25D591DFCCF621A1677EA0.rs:1:12
  |
1 | #![feature(specialization)]
  |            ^^^^^^^^^^^^^^
  |
  = note: see issue #31844 <https://github.com/rust-lang/rust/issues/31844> for more information
  = help: consider using `min_specialization` instead, which is more stable and complete
  = note: `#[warn(incomplete_features)]` on by default

error[E0391]: cycle detected when building specialization graph of trait `Trait`
 --> 43273EB829A15349E16F5931020795BF70C210EEDA25D591DFCCF621A1677EA0.rs:3:1
  |
3 | trait Trait<T> {
  | ^^^^^^^^^^^^^^
  |
  = note: ...which immediately requires building specialization graph of trait `Trait` again
note: cycle used when coherence checking all impls of trait `Trait`
 --> 43273EB829A15349E16F5931020795BF70C210EEDA25D591DFCCF621A1677EA0.rs:3:1
  |
3 | trait Trait<T> {
  | ^^^^^^^^^^^^^^
  = note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information

error: aborting due to 1 previous error; 1 warning emitted

For more information about this error, try `rustc --explain E0391`.

Desired output

We should have a proper diagnostic here pointing out where the cyclic problem is

Rationale and extra context

cc https://github.com/rust-lang/rust/issues/119321

Other cases

No response

Anything else?

No response

Start by compiling the Rust reproducer with specialization enabled and compare the current E0391 output with the requested diagnostic. Review the related issue #119321 for context; done means the cycle is reported with a proper explanation of where the cyclic problem occurs.