add non-regression test for issue 105809

Author: lqd

src/test/ui/mir/issue-105809.rs

@@ -0,0 +1,36 @@
+// Non-regression test ICE from issue #105809 and duplicates.
+
+// build-pass: the ICE is during codegen
+// compile-flags: --edition 2018 -Zmir-opt-level=1
+
+use std::{future::Future, pin::Pin};
+
+// Create a `T` without affecting analysis like `loop {}`.
+fn create<T>() -> T {
+    loop {}
+}
+
+async fn trivial_future() {}
+
+struct Connection<H> {
+    _h: H,
+}
+
+async fn complex_future<H>(conn: &Connection<H>) {
+    let small_fut = async move {
+        let _ = conn;
+        trivial_future().await;
+    };
+
+    let mut tuple = (small_fut,);
+    let (small_fut_again,) = &mut tuple;
+    let _ = small_fut_again;
+}
+
+fn main() {
+    let mut fut = complex_future(&Connection { _h: () });
+
+    let mut cx = create();
+    let future = unsafe { Pin::new_unchecked(&mut fut) };
+    let _ = future.poll(&mut cx);
+}