Fix ICE for broken or-pattern in async fn

src/test/ui/or-patterns/mismatched-bindings-async-fn.rs

@@ -0,0 +1,16 @@
+// Regression test for #71297
+// edition:2018
+
+#![feature(or_patterns)]
+
+async fn a((x | s): String) {}
+//~^ ERROR variable `x` is not bound in all patterns
+//~| ERROR variable `s` is not bound in all patterns
+
+async fn b() {
+    let x | s = String::new();
+    //~^ ERROR variable `x` is not bound in all patterns
+    //~| ERROR variable `s` is not bound in all patterns
+}
+
+fn main() {}

src/test/ui/or-patterns/mismatched-bindings-async-fn.stderr

@@ -0,0 +1,35 @@
+error[E0408]: variable `x` is not bound in all patterns
+  --> $DIR/mismatched-bindings-async-fn.rs:6:17
+   |
+LL | async fn a((x | s): String) {}
+   |             -   ^ pattern doesn't bind `x`
+   |             |
+   |             variable not in all patterns
+
+error[E0408]: variable `s` is not bound in all patterns
+  --> $DIR/mismatched-bindings-async-fn.rs:6:13
+   |
+LL | async fn a((x | s): String) {}
+   |             ^   - variable not in all patterns
+   |             |
+   |             pattern doesn't bind `s`
+
+error[E0408]: variable `x` is not bound in all patterns
+  --> $DIR/mismatched-bindings-async-fn.rs:11:13
+   |
+LL |     let x | s = String::new();
+   |         -   ^ pattern doesn't bind `x`
+   |         |
+   |         variable not in all patterns
+
+error[E0408]: variable `s` is not bound in all patterns
+  --> $DIR/mismatched-bindings-async-fn.rs:11:9
+   |
+LL |     let x | s = String::new();
+   |         ^   - variable not in all patterns
+   |         |
+   |         pattern doesn't bind `s`
+
+error: aborting due to 4 previous errors
+
+For more information about this error, try `rustc --explain E0408`.