commit 520217cc15315fe1cc58dff23c65bb3cdc28dc56
Author: Jason Merrill <jason@redhat.com>
Date:   Wed Nov 29 21:51:36 2023 -0500

    wildcard

diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index 7946f0be77b..e0cb8a1b04f 100644
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -2265,6 +2265,10 @@ finish_non_static_data_member (tree decl, tree object, tree qualifying_scope,
       else if (PACK_EXPANSION_P (type))
 	/* Don't bother trying to represent this.  */
 	type = NULL_TREE;
+      else if (WILDCARD_TYPE_P (TREE_TYPE (object)))
+	/* We don't know what the eventual quals will be.  This can happen when
+	   called from build_capture_proxy for an explicit object lambda.  */
+	type = NULL_TREE;
       else
 	{
 	  /* Set the cv qualifiers.  */
@@ -11709,6 +11713,7 @@ finish_decltype_type (tree expr, bool id_expression_or_member_access_p,
      A<decltype(sizeof(T))>::U doesn't require 'typename'.  */
   if (instantiation_dependent_uneval_expression_p (expr))
     {
+    dependent:
       type = cxx_make_type (DECLTYPE_TYPE);
       DECLTYPE_TYPE_EXPR (type) = expr;
       DECLTYPE_TYPE_ID_EXPR_OR_MEMBER_ACCESS_P (type)
@@ -11883,7 +11888,11 @@ finish_decltype_type (tree expr, bool id_expression_or_member_access_p,
       if (outer_automatic_var_p (STRIP_REFERENCE_REF (expr))
 	  && current_function_decl
 	  && LAMBDA_FUNCTION_P (current_function_decl))
-	type = capture_decltype (STRIP_REFERENCE_REF (expr));
+	{
+	  type = capture_decltype (STRIP_REFERENCE_REF (expr));
+	  if (!type)
+	    goto dependent;
+	}
       else if (error_operand_p (expr))
 	type = error_mark_node;
       else if (expr == current_class_ptr)
@@ -12821,7 +12830,8 @@ capture_decltype (tree decl)
     {
       int quals = cp_type_quals (type);
       tree obtype = TREE_TYPE (DECL_ARGUMENTS (current_function_decl));
-      gcc_checking_assert (!WILDCARD_TYPE_P (non_reference (obtype)));
+      if (WILDCARD_TYPE_P (non_reference (obtype)))
+	return NULL_TREE;
       if (INDIRECT_TYPE_P (obtype))
 	quals |= cp_type_quals (TREE_TYPE (obtype));
       type = cp_build_qualified_type (type, quals);