c++: Fix ICE with struct in function parameter containing auto [PR122112]

When parsing function parameters containing a struct declaration,
initially auto_is_implicit_function_template_parm_p is set to true by
cp_parser_parameter_declaration_clause. However, later when we enter
class scope and scope_kind becomes sk_class, we don't set it to false, so
cp_parser_simple_type_specifier will call
synthesize_implicit_template_parm, which expects that
current_binding_level->kind == sk_function_parms, triggering a failed
assertion. This fix ensures that auto_is_implicit_function_template_parm_p
isn't set when parsing a struct body definition.

gcc/cp/ChangeLog:

	PR c++/122112
	* parser.cc (cp_parser_parameter_declaration_clause): Don't
	enable auto_is_implicit_function_template_parm_p when entering
	class scope.

gcc/testsuite/ChangeLog:

	PR c++/122112
	* g++.dg/parse/auto-struct-param.C: New test.

Signed-off-by: Egas Ribeiro <egas.g.ribeiro@tecnico.ulisboa.pt>

diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
index 8d1187f8cdae7015add294665e481195bca7c1b3..04031486bb3bf79ea4298acc88f3dccd48eef3a6 100644 (file)
--- a/gcc/cp/parser.cc
+++ b/gcc/cp/parser.cc
@@ -28124,6 +28124,7 @@ cp_parser_class_specifier (cp_parser* parser)
   bool in_switch_statement_p;
   bool saved_in_unbraced_linkage_specification_p;
   bool saved_in_unbraced_export_declaration_p;
+  bool saved_auto_is_implicit_function_template_parm_p;
   tree old_scope = NULL_TREE;
   tree scope = NULL_TREE;
   cp_token *closing_brace;
@@ -28181,6 +28182,10 @@ cp_parser_class_specifier (cp_parser* parser)
   saved_in_unbraced_export_declaration_p
     = parser->in_unbraced_export_declaration_p;
   parser->in_unbraced_export_declaration_p = false;
+  saved_auto_is_implicit_function_template_parm_p
+    = parser->auto_is_implicit_function_template_parm_p;
+  parser->auto_is_implicit_function_template_parm_p = false;
+
   /* 'this' from an enclosing non-static member function is unavailable.  */
   tree saved_ccp = current_class_ptr;
   tree saved_ccr = current_class_ref;
@@ -28571,6 +28576,8 @@ cp_parser_class_specifier (cp_parser* parser)
     = saved_in_unbraced_linkage_specification_p;
   parser->in_unbraced_export_declaration_p
     = saved_in_unbraced_export_declaration_p;
+  parser->auto_is_implicit_function_template_parm_p
+    = saved_auto_is_implicit_function_template_parm_p;
   current_class_ptr = saved_ccp;
   current_class_ref = saved_ccr;
 

diff --git a/gcc/testsuite/g++.dg/parse/auto-struct-param.C b/gcc/testsuite/g++.dg/parse/auto-struct-param.C
new file mode 100644 (file)
index 0000000..78573c6
--- /dev/null
+++ b/gcc/testsuite/g++.dg/parse/auto-struct-param.C
@@ -0,0 +1,4 @@
+// PR c++/122112
+// { dg-do compile { target c++20 } }
+
+void func(struct { auto x; });  // { dg-error "" }