same diagnostic repeated 5 times

Code

#![feature(yield_expr, iter_macro)]
use std::iter::iter;
use std::pin::pin;
use std::task::{Context, Waker};
async fn call_async_once(f: impl AsyncFnOnce()) {
    f().await
}
fn main() {
    let f = iter! { || yield};
    pin!(call_async_once(f)).poll(&mut Context::from_waker(Waker::noop()));
}

Current output

error[E0277]: the trait bound `{gen closure@a.rs:9:21: 9:23}: AsyncFnOnce()` is not satisfied
  --> a.rs:10:26
   |
10 |     pin!(call_async_once(f)).poll(&mut Context::from_waker(Waker::noop()));
   |          --------------- ^ the trait `AsyncFnOnce()` is not implemented for `{gen closure@a.rs:9:21: 9:23}`
   |          |
   |          required by a bound introduced by this call
   |
note: required by a bound in `call_async_once`
  --> a.rs:5:34
   |
 5 | async fn call_async_once(f: impl AsyncFnOnce()) {
   |                                  ^^^^^^^^^^^^^ required by this bound in `call_async_once`

error[E0277]: the trait bound `{gen closure@a.rs:9:21: 9:23}: AsyncFnOnce()` is not satisfied
  --> a.rs:10:10
   |
10 |     pin!(call_async_once(f)).poll(&mut Context::from_waker(Waker::noop()));
   |          ^^^^^^^^^^^^^^^^^^ the trait `AsyncFnOnce()` is not implemented for `{gen closure@a.rs:9:21: 9:23}`
   |
note: required by a bound in `call_async_once`
  --> a.rs:5:34
   |
 5 | async fn call_async_once(f: impl AsyncFnOnce()) {
   |                                  ^^^^^^^^^^^^^ required by this bound in `call_async_once`

error[E0277]: the trait bound `{gen closure@a.rs:9:21: 9:23}: AsyncFnOnce()` is not satisfied
  --> a.rs:10:5
   |
10 |     pin!(call_async_once(f)).poll(&mut Context::from_waker(Waker::noop()));
   |     ^^^^^^^^^^^^^^^^^^^^^^^^ the trait `AsyncFnOnce()` is not implemented for `{gen closure@a.rs:9:21: 9:23}`
   |
note: required by a bound in `call_async_once`
  --> a.rs:5:34
   |
 5 | async fn call_async_once(f: impl AsyncFnOnce()) {
   |                                  ^^^^^^^^^^^^^ required by this bound in `call_async_once`

error[E0277]: the trait bound `{gen closure@a.rs:9:21: 9:23}: AsyncFnOnce()` is not satisfied
  --> a.rs:10:5
   |
10 |     pin!(call_async_once(f)).poll(&mut Context::from_waker(Waker::noop()));
   |     ^^^^^^^^^^^^^^^^^^^^^^^^ the trait `AsyncFnOnce()` is not implemented for `{gen closure@a.rs:9:21: 9:23}`
   |
note: required by a bound in `call_async_once`
  --> a.rs:5:34
   |
 5 | async fn call_async_once(f: impl AsyncFnOnce()) {
   |                                  ^^^^^^^^^^^^^ required by this bound in `call_async_once`

error[E0277]: the trait bound `{gen closure@a.rs:9:21: 9:23}: AsyncFnOnce()` is not satisfied
  --> a.rs:10:5
   |
10 |     pin!(call_async_once(f)).poll(&mut Context::from_waker(Waker::noop()));
   |     ^^^^^^^^^^^^^^^^^^^^^^^^ the trait `AsyncFnOnce()` is not implemented for `{gen closure@a.rs:9:21: 9:23}`
   |
note: required by a bound in `call_async_once`
  --> a.rs:5:34
   |
 5 | async fn call_async_once(f: impl AsyncFnOnce()) {
   |                                  ^^^^^^^^^^^^^ required by this bound in `call_async_once`

error[E0277]: the trait bound `{gen closure@a.rs:9:21: 9:23}: AsyncFnOnce()` is not satisfied
  --> a.rs:10:5
   |
10 |     pin!(call_async_once(f)).poll(&mut Context::from_waker(Waker::noop()));
   |     ^^^^^^^^^^^^^^^^^^^^^^^^ the trait `AsyncFnOnce()` is not implemented for `{gen closure@a.rs:9:21: 9:23}`
   |
note: required by a bound in `call_async_once`
  --> a.rs:5:34
   |
 5 | async fn call_async_once(f: impl AsyncFnOnce()) {
   |                                  ^^^^^^^^^^^^^ required by this bound in `call_async_once`

error[E0277]: the trait bound `{gen closure@a.rs:9:21: 9:23}: AsyncFnOnce()` is not satisfied
  --> a.rs:10:5
   |
10 |     pin!(call_async_once(f)).poll(&mut Context::from_waker(Waker::noop()));
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `AsyncFnOnce()` is not implemented for `{gen closure@a.rs:9:21: 9:23}`
   |
note: required by a bound in `call_async_once`
  --> a.rs:5:34
   |
 5 | async fn call_async_once(f: impl AsyncFnOnce()) {
   |                                  ^^^^^^^^^^^^^ required by this bound in `call_async_once`

error: aborting due to 7 previous errors

For more information about this error, try `rustc --explain E0277`.

Desired output

error[E0277]: the trait bound `{gen closure@a.rs:9:21: 9:23}: AsyncFnOnce()` is not satisfied
  --> a.rs:10:26
   |
10 |     pin!(call_async_once(f)).poll(&mut Context::from_waker(Waker::noop()));
   |          --------------- ^ the trait `AsyncFnOnce()` is not implemented for `{gen closure@a.rs:9:21: 9:23}`
   |          |
   |          required by a bound introduced by this call
   |
note: required by a bound in `call_async_once`
  --> a.rs:5:34
   |
 5 | async fn call_async_once(f: impl AsyncFnOnce()) {
   |                                  ^^^^^^^^^^^^^ required by this bound in `call_async_once`

error[E0277]: the trait bound `{gen closure@a.rs:9:21: 9:23}: AsyncFnOnce()` is not satisfied
  --> a.rs:10:10
   |
10 |     pin!(call_async_once(f)).poll(&mut Context::from_waker(Waker::noop()));
   |          ^^^^^^^^^^^^^^^^^^ the trait `AsyncFnOnce()` is not implemented for `{gen closure@a.rs:9:21: 9:23}`
   |
note: required by a bound in `call_async_once`
  --> a.rs:5:34
   |
 5 | async fn call_async_once(f: impl AsyncFnOnce()) {
   |                                  ^^^^^^^^^^^^^ required by this bound in `call_async_once`

error[E0277]: the trait bound `{gen closure@a.rs:9:21: 9:23}: AsyncFnOnce()` is not satisfied
  --> a.rs:10:5
   |
10 |     pin!(call_async_once(f)).poll(&mut Context::from_waker(Waker::noop()));
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `AsyncFnOnce()` is not implemented for `{gen closure@a.rs:9:21: 9:23}`
   |
note: required by a bound in `call_async_once`
  --> a.rs:5:34
   |
 5 | async fn call_async_once(f: impl AsyncFnOnce()) {
   |                                  ^^^^^^^^^^^^^ required by this bound in `call_async_once`

error: aborting due to 7 previous errors

For more information about this error, try `rustc --explain E0277`.

Rationale and extra context

No response

Other cases

Rust Version

rustc 1.97.0-nightly (67bcaa9c4 2026-05-01)
binary: rustc
commit-hash: 67bcaa9c4b1b1015efae3d591155c79760b1e0a5
commit-date: 2026-05-01
host: x86_64-unknown-linux-gnu
release: 1.97.0-nightly
LLVM version: 22.1.4

Anything else?

needs --edition=2024

Start by running the provided a.rs reproducer with rustc 1.97.0-nightly and --edition=2024, then trace the compiler's diagnostic emission for the repeated E0277 messages. Done means the reproducer reports the same seven errors but displays only the three distinct diagnostics shown in the desired output.