c++: Update TYPE_FIELDS of variant types if cp_parser_late_parsing_default_args etc. modify it [PR98533]

The following testcases ICE during type verification, because TYPE_FIELDS
of e.g. S RECORD_TYPE in pr119123.C is different from TYPE_FIELDS of const S.
Various decls are added to S's TYPE_FIELDS first, then finish_struct
indirectly calls fixup_type_variants to sync the variant copies.
But later on cp_parser_class_specifier calls
cp_parser_late_parsing_default_args and that apparently adds a lambda
type (from default argument) to TYPE_FIELDS of S.
Dunno if that is right or not, assuming it is right, the following
patch fixes it by updating TYPE_FIELDS of variant types if there were
any changes in the various functions cp_parser_class_specifier defers and
calls on the outermost enclosing class.
There was quite a lot of code repetition already before, so the patch
uses a lambda to avoid the repetitions.
To my surprise, in some of the contract testcases (
g++.dg/contracts/contracts-friend1.C
g++.dg/contracts/contracts-nested-class1.C
g++.dg/contracts/contracts-nested-class2.C
g++.dg/contracts/contracts-redecl7.C
g++.dg/contracts/contracts-redecl8.C
) it is actually setting class_type and pushing TRANSLATION_UNIT_DECL
rather than some class types in some cases.

Or should the lambda pushing into the containing class be somehow avoided?

2025-03-06  Jakub Jelinek  <jakub@redhat.com>

	PR c++/98533
	PR c++/119123
	* parser.cc (cp_parser_class_specifier): Update TYPE_FIELDS of
	variant types in case cp_parser_late_parsing_default_args etc. change
	TYPE_FIELDS on the main variant.  Add switch_to_class lambda and
	use it to simplify repeated class switching code.

	* g++.dg/cpp0x/pr98533.C: New test.
	* g++.dg/cpp0x/pr119123.C: New test.

3 files changed, 68 insertions, 30 deletions

diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
index 69c27aa..489c00e 100644
--- a/gcc/cp/parser.cc
+++ b/gcc/cp/parser.cc
@@ -27718,6 +27718,7 @@ cp_parser_class_specifier (cp_parser* parser)
     {
       tree decl;
       tree class_type = NULL_TREE;
+      tree class_type_fields = NULL_TREE;
       tree pushed_scope = NULL_TREE;
       unsigned ix;
       cp_default_arg_entry *e;
@@ -27731,6 +27732,33 @@ cp_parser_class_specifier (cp_parser* parser)
 	  vec_safe_truncate (unparsed_funs_with_definitions, 0);
 	}
 
+      auto switch_to_class = [&] (tree t)
+	{
+	  if (class_type != t)
+	    {
+	      /* cp_parser_late_parsing_default_args etc. could have changed
+		 TYPE_FIELDS (class_type), propagate that to all variants.  */
+	      if (class_type
+		  && RECORD_OR_UNION_TYPE_P (class_type)
+		  && TYPE_FIELDS (class_type) != class_type_fields)
+		for (tree variant = TYPE_NEXT_VARIANT (class_type);
+		     variant; variant = TYPE_NEXT_VARIANT (variant))
+		  TYPE_FIELDS (variant) = TYPE_FIELDS (class_type);
+	      if (pushed_scope)
+		pop_scope (pushed_scope);
+	      class_type = t;
+	      class_type_fields = NULL_TREE;
+	      if (t)
+		{
+		  if (RECORD_OR_UNION_TYPE_P (class_type))
+		    class_type_fields = TYPE_FIELDS (class_type);
+		  pushed_scope = push_scope (class_type);
+		}
+	      else
+		pushed_scope = NULL_TREE;
+	    }
+	};
+
       /* In a first pass, parse default arguments to the functions.
 	 Then, in a second pass, parse the bodies of the functions.
 	 This two-phased approach handles cases like:
@@ -27746,13 +27774,7 @@ cp_parser_class_specifier (cp_parser* parser)
 	  decl = e->decl;
 	  /* If there are default arguments that have not yet been processed,
 	     take care of them now.  */
-	  if (class_type != e->class_type)
-	    {
-	      if (pushed_scope)
-		pop_scope (pushed_scope);
-	      class_type = e->class_type;
-	      pushed_scope = push_scope (class_type);
-	    }
+	  switch_to_class (e->class_type);
 	  /* Make sure that any template parameters are in scope.  */
 	  maybe_begin_member_template_processing (decl);
 	  /* Parse the default argument expressions.  */
@@ -27768,13 +27790,7 @@ cp_parser_class_specifier (cp_parser* parser)
       FOR_EACH_VEC_SAFE_ELT (unparsed_noexcepts, ix, decl)
 	{
 	  tree ctx = DECL_CONTEXT (decl);
-	  if (class_type != ctx)
-	    {
-	      if (pushed_scope)
-		pop_scope (pushed_scope);
-	      class_type = ctx;
-	      pushed_scope = push_scope (class_type);
-	    }
+	  switch_to_class (ctx);
 
 	  tree def_parse = TYPE_RAISES_EXCEPTIONS (TREE_TYPE (decl));
 	  def_parse = TREE_PURPOSE (def_parse);
@@ -27830,13 +27846,7 @@ cp_parser_class_specifier (cp_parser* parser)
       FOR_EACH_VEC_SAFE_ELT (unparsed_nsdmis, ix, decl)
 	{
 	  tree ctx = type_context_for_name_lookup (decl);
-	  if (class_type != ctx)
-	    {
-	      if (pushed_scope)
-		pop_scope (pushed_scope);
-	      class_type = ctx;
-	      pushed_scope = push_scope (class_type);
-	    }
+	  switch_to_class (ctx);
 	  inject_this_parameter (class_type, TYPE_UNQUALIFIED);
 	  cp_parser_late_parsing_nsdmi (parser, decl);
 	}
@@ -27846,13 +27856,7 @@ cp_parser_class_specifier (cp_parser* parser)
       FOR_EACH_VEC_SAFE_ELT (unparsed_contracts, ix, decl)
 	{
 	  tree ctx = DECL_CONTEXT (decl);
-	  if (class_type != ctx)
-	    {
-	      if (pushed_scope)
-		pop_scope (pushed_scope);
-	      class_type = ctx;
-	      pushed_scope = push_scope (class_type);
-	    }
+	  switch_to_class (ctx);
 
 	  temp_override<tree> cfd(current_function_decl, decl);
 
@@ -27893,8 +27897,7 @@ cp_parser_class_specifier (cp_parser* parser)
 
       current_class_ptr = NULL_TREE;
       current_class_ref = NULL_TREE;
-      if (pushed_scope)
-	pop_scope (pushed_scope);
+      switch_to_class (NULL_TREE);
 
       /* Now parse the body of the functions.  */
       if (flag_openmp)
diff --git a/gcc/testsuite/g++.dg/cpp0x/pr119123.C b/gcc/testsuite/g++.dg/cpp0x/pr119123.C
new file mode 100644
index 0000000..bbc1ca0
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/pr119123.C
@@ -0,0 +1,10 @@
+// PR c++/119123
+// { dg-do compile { target c++11 } }
+// { dg-options "-O2 -g" }
+
+struct S {
+  template <typename> void foo (int = [] {}) const;
+};
+struct T {
+  static void bar (const S &);
+};
diff --git a/gcc/testsuite/g++.dg/cpp0x/pr98533.C b/gcc/testsuite/g++.dg/cpp0x/pr98533.C
new file mode 100644
index 0000000..c279d02
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/pr98533.C
@@ -0,0 +1,25 @@
+// PR c++/98533
+// { dg-do compile { target c++11 } }
+// { dg-options "-g" }
+
+class IR;
+struct Pass {
+  explicit Pass(IR *ir) : ir_(ir) {}
+  virtual ~Pass() = default;
+  IR *ir_ {nullptr};
+};
+struct PassManager {
+  template <typename T> void RunPass() { T pass(ir_); }
+  IR *ir_ {nullptr};
+};
+struct IR final {
+  template <typename T> void RunPass() { pass_manager_.RunPass<T>(); }
+  PassManager pass_manager_;
+};
+struct ThePass : Pass {
+  explicit ThePass(IR *ir) : Pass(ir) {}
+  ThePass(const ThePass &) = delete;
+  template <typename Func = bool (*)(void *)> void Bar(void *inst, Func func = [](void *) {});
+};
+
+void foo(IR *ir) { ir->RunPass<ThePass>(); }