Add test

tests/ui/async-await/auxiliary/issue-107036.rs

@@ -0,0 +1,12 @@
+// edition:2021
+
+pub trait T {}
+impl T for () {}
+
+pub struct S {}
+
+impl S {
+    pub async fn f<'a>(&self) -> impl T + 'a {
+        ()
+    }
+}

tests/ui/async-await/issue-107036.rs

@@ -0,0 +1,14 @@
+// aux-build:issue-107036.rs
+// edition:2021
+// check-pass
+
+extern crate issue_107036;
+use issue_107036::S;
+
+async fn f() {
+    S{}.f().await;
+}
+
+fn main() {
+    let _ = f();
+}