[gcc r12-6779] c++: designator for base class member [PR101405]

[Jason Merrill <jason@gcc.gnu.org>]

https://gcc.gnu.org/g:cc01cd9397fe99e707bcc5b98bb33d807ba610d7

commit r12-6779-gcc01cd9397fe99e707bcc5b98bb33d807ba610d7
Author: Jason Merrill <jason@redhat.com>
Date:   Thu Jan 20 09:18:45 2022 -0500

    c++: designator for base class member [PR101405]
    
    A C++20 designator must name a direct non-static member of the class; in
    this case it names a member of a base class, and we should give an error
    instead of crashing.
    
            PR c++/101405
    
    gcc/cp/ChangeLog:
    
            * decl.cc (reshape_init_class): Reject designator for a member of
            another class.
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/cpp2a/desig20.C: New test.

Diff:
---
 gcc/cp/decl.cc                       | 14 ++++++++++----
 gcc/testsuite/g++.dg/cpp2a/desig20.C | 20 ++++++++++++++++++++
 2 files changed, 30 insertions(+), 4 deletions(-)

diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
index 1cbe9a34be0..8e5421848d1 100644
--- a/gcc/cp/decl.cc
+++ b/gcc/cp/decl.cc
@@ -6569,16 +6569,22 @@ reshape_init_class (tree type, reshape_iter *d, bool first_initializer_p,
 	  tree ictx = DECL_CONTEXT (field);
 	  if (!same_type_ignoring_top_level_qualifiers_p (ictx, type))
 	    {
-	      gcc_assert (ANON_AGGR_TYPE_P (ictx));
 	      /* Find the anon aggr that is a direct member of TYPE.  */
-	      while (true)
+	      while (ANON_AGGR_TYPE_P (ictx))
 		{
 		  tree cctx = TYPE_CONTEXT (ictx);
 		  if (same_type_ignoring_top_level_qualifiers_p (cctx, type))
-		    break;
+		    goto found;
 		  ictx = cctx;
 		}
-	      /* And then the TYPE member with that anon aggr type.  */
+
+	      /* Not found, e.g. FIELD is a member of a base class.  */
+	      if (complain & tf_error)
+		error ("%qD is not a direct member of %qT", field, type);
+	      return error_mark_node;
+
+	    found:
+	      /* Now find the TYPE member with that anon aggr type.  */
 	      tree aafield = TYPE_FIELDS (type);
 	      for (; aafield; aafield = TREE_CHAIN (aafield))
 		if (TREE_TYPE (aafield) == ictx)
diff --git a/gcc/testsuite/g++.dg/cpp2a/desig20.C b/gcc/testsuite/g++.dg/cpp2a/desig20.C
new file mode 100644
index 00000000000..0ceda7ccabd
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/desig20.C
@@ -0,0 +1,20 @@
+// PR c++/101405
+// { dg-do compile { target c++20 } }
+
+struct A {
+  int const a = 1;
+  int const b = 2;
+};
+
+struct B : A {
+  using A::a;
+  using A::b;
+  int const c = 3;
+  int const d = 4;
+};
+
+int main()
+{
+  [[maybe_unused]] B b =
+  { .a = 10, .d = 42 };		// { dg-error "not a direct member" }
+}