Rollup merge of rust-lang#95102 - compiler-errors:issue-94034-bug, r=…

…jackh726

Add known-bug for rust-lang#95034

Couldn't fix the issue, since I am no type theorist and inference variables in universes above U0 scare me. But I at least wanted to add a known-bug test for it.

cc rust-lang#95034 (does not fix)

src/test/ui/hrtb/issue-94034.rs

@@ -0,0 +1,96 @@
+// known-bug
+// failure-status: 101
+// compile-flags: --edition=2021 --crate-type=lib
+// rustc-env:RUST_BACKTRACE=0
+
+// normalize-stderr-test "thread 'rustc' panicked.*" -> "thread 'rustc' panicked"
+// normalize-stderr-test "note:.*RUST_BACKTRACE=1.*\n" -> ""
+// normalize-stderr-test "\nerror: internal compiler error.*\n\n" -> ""
+// normalize-stderr-test "note:.*unexpectedly panicked.*\n\n" -> ""
+// normalize-stderr-test "note: we would appreciate a bug report.*\n\n" -> ""
+// normalize-stderr-test "note: compiler flags.*\n\n" -> ""
+// normalize-stderr-test "note: rustc.*running on.*\n\n" -> ""
+// normalize-stderr-test "query stack during panic:\n" -> ""
+// normalize-stderr-test "we're just showing a limited slice of the query stack\n" -> ""
+// normalize-stderr-test "end of query stack\n" -> ""
+// normalize-stderr-test "#.*\n" -> ""
+
+// This should not ICE.
+
+use std::{
+    future::Future,
+    marker::PhantomData,
+    pin::Pin,
+    task::{Context, Poll},
+};
+
+mod object {
+    use super::*;
+
+    pub trait Object<'a> {
+        type Error;
+        type Future: Future<Output = Self>;
+        fn create() -> Self::Future;
+    }
+
+    impl<'a> Object<'a> for u8 {
+        type Error = ();
+        type Future = Pin<Box<dyn Future<Output = Self>>>;
+        fn create() -> Self::Future {
+            unimplemented!()
+        }
+    }
+
+    impl<'a, E, A: Object<'a, Error = E>> Object<'a> for (A,) {
+        type Error = ();
+        type Future = CustomFut<'a, E, A>;
+        fn create() -> Self::Future {
+            unimplemented!()
+        }
+    }
+
+    pub struct CustomFut<'f, E, A: Object<'f, Error = E>> {
+        ph: PhantomData<(A::Future,)>,
+    }
+
+    impl<'f, E, A: Object<'f, Error = E>> Future for CustomFut<'f, E, A> {
+        type Output = (A,);
+        fn poll(self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<Self::Output> {
+            unimplemented!()
+        }
+    }
+}
+
+mod async_fn {
+    use super::*;
+
+    pub trait AsyncFn {
+        type Future: Future<Output = ()>;
+        fn call(&self) -> Self::Future;
+    }
+
+    impl<F, Fut> AsyncFn for F
+    where
+        F: Fn() -> Fut,
+        Fut: Future<Output = ()>,
+    {
+        type Future = Fut;
+        fn call(&self) -> Self::Future {
+            (self)()
+        }
+    }
+}
+
+pub async fn test() {
+    use self::{async_fn::AsyncFn, object::Object};
+
+    async fn create<T: Object<'static>>() {
+        T::create().await;
+    }
+
+    async fn call_async_fn(inner: impl AsyncFn) {
+        inner.call().await;
+    }
+
+    call_async_fn(create::<(u8,)>).await;
+}

src/test/ui/hrtb/issue-94034.stderr

@@ -0,0 +1 @@
+thread 'rustc' panicked