Lower anonymous structs or unions to HIR

compiler/rustc_trait_selection/src/traits/select/mod.rs

@@ -2212,6 +2212,16 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
 
             // FIXME(async_closures): These are never clone, for now.
             ty::CoroutineClosure(_, _) => None,
+            // `Copy` and `Clone` are automatically impelemented for an anonymous adt
+            // if all of its fields are `Copy` and `Clone`
+            ty::Adt(adt, args) if adt.is_anonymous() => {
+                // (*) binder moved here
+                Where(
+                    obligation
+                        .predicate
+                        .rebind(adt.all_fields().map(|f| f.ty(self.tcx(), args)).collect()),
+                )
+            }
 
             ty::Adt(..) | ty::Alias(..) | ty::Param(..) | ty::Placeholder(..) => {
                 // Fallback to whatever user-defined impls exist in this case.