fix: add CoroutineClosure and Error arms to simplify_nounwind_call

compiler/rustc_mir_transform/src/instsimplify.rs

@@ -390,7 +390,9 @@ impl<'tcx> InstSimplifyContext<'_, 'tcx> {
         let body_abi = match body_ty.kind() {
             ty::FnDef(..) => body_ty.fn_sig(self.tcx).abi(),
             ty::Closure(..) => ExternAbi::RustCall,
+            ty::CoroutineClosure(..) => ExternAbi::RustCall,
             ty::Coroutine(..) => ExternAbi::Rust,
+            ty::Error(_) => return,
             _ => bug!("unexpected body ty: {body_ty:?}"),
         };
 

tests/ui/async-await/async-closures/instsimplify-nounwind.rs

@@ -0,0 +1,20 @@
+// Regression test for #477: simplify_nounwind_call missing CoroutineClosure arm.
+// Before the fix, the MIR instsimplify pass would ICE (bug!("unexpected body ty"))
+// when encountering an async closure body type during nounwind simplification.
+
+//@ edition:2021
+//@ build-pass
+
+async fn call_once(f: impl std::future::Future<Output = ()>) {
+    f.await;
+}
+
+fn main() {
+    let _ = async {
+        let x = 1i32;
+        let c = async move || {
+            let _ = x;
+        };
+        call_once(c()).await;
+    };
+}