Lower anonymous structs or unions to HIR

compiler/rustc_trait_selection/src/solve/assembly/structural_traits.rs

@@ -181,6 +181,11 @@ pub(in crate::solve) fn instantiate_constituent_tys_for_copy_clone_trait<'tcx>(
         | ty::Ref(_, _, Mutability::Not)
         | ty::Array(..) => Err(NoSolution),
 
+        // Check for anonymous adts.
+        ty::Adt(adt, generics) if adt.is_anonymous() => {
+            Ok(adt.all_fields().map(|f| f.ty(ecx.tcx(), generics)).collect())
+        }
+
         ty::Dynamic(..)
         | ty::Str
         | ty::Slice(_)

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.