[Clang][P1061] Add bit-field and pack indexing tests

Author: ricejasonf

clang/lib/Sema/SemaTemplateVariadic.cpp

@@ -802,7 +802,8 @@ bool Sema::CheckParameterPacksForExpansion(
             CurrentInstantiationScope->findInstantiationOf(ND);
         Decl *B = cast<Decl *>(*Instantiation);
         Expr *BindingExpr = cast<BindingDecl>(B)->getBinding();
-        ResolvedPack = dyn_cast<ResolvedUnexpandedPackExpr>(BindingExpr);
+        ResolvedPack =
+            dyn_cast_if_present<ResolvedUnexpandedPackExpr>(BindingExpr);
         if (!ResolvedPack) {
           ShouldExpand = false;
           continue;

clang/test/SemaCXX/cxx2c-binding-pack.cpp

@@ -60,6 +60,9 @@ template <typename T>
 void decompose_struct() {
   T obj{1, 2, 3, 6};
   auto [x, ...rest, y] = obj;
+
+  auto [...empty] = type_<int>{};
+  static_assert(sizeof...(empty) == 0);
 }
 
 template <typename T>
@@ -88,9 +91,27 @@ struct S {
   };
 };
 
+struct bit_fields {
+  int a : 4 {1};
+  int b : 4 {2};
+  int c : 4 {3};
+  int d : 4 {4};
+};
+
+template <typename T>
+void decompose_bit_field() {
+  auto [...x] = T{};
+  static_assert(sizeof...(x) == 4);
+  int a = x...[0];
+  int b = x...[1];
+  int c = x...[2];
+  int d = x...[3];
+}
+
 int main() {
   decompose_array<int>();
   decompose_tuple<fake_tuple>();
   decompose_struct<my_struct>();
   S<1, 2, 3, 4>::N<5, 6>().foo();
+  decompose_bit_field<bit_fields>();
 }