c++: tweak parsing of invalid types

cp_parser_parse_and_diagnose_invalid_type_name is called during declaration
parsing, so it should pass 'true' for the declarator_p argument.  But that
caused a diagnostic regression on template/pr84789.C due to undesired lookup
in dependent scopes.  To fix that, cp_parser_nested_name_specifier_opt needs
to respect the value of check_dependency_p.

This patch avoids a regression from Andrew Sharp's WIP patch for PR70417.

It would make more sense to test only check_dependency_p, not declarator_p,
but removing the declarator_p condition turns out to reveal complicated
interactions of cp_parser_constructor_declarator_p and caching of
nested-name-specifiers and template-ids that I've already spent too much
time trying to sort out.

gcc/cp/ChangeLog:

	* parser.c (cp_parser_parse_and_diagnose_invalid_type_name):
	Pass true for declarator_p.
	(cp_parser_nested_name_specifier_opt): Only look through
	TYPENAME_TYPE if check_dependency_p is false.

diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 9c7ed65f55c8a6388bd00d83d9ca745fe415092f..49d951cfb193ce18079460eda1e9a4be045cf487 100644 (file)
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -3693,7 +3693,7 @@ cp_parser_parse_and_diagnose_invalid_type_name (cp_parser *parser)
                                /*template_keyword_p=*/false,
                                /*check_dependency_p=*/true,
                                /*template_p=*/NULL,
-                               /*declarator_p=*/false,
+                               /*declarator_p=*/true,
                                /*optional_p=*/false);
   /* If the next token is a (, this is a function with no explicit return
      type, i.e. constructor, destructor or conversion op.  */
@@ -6605,6 +6605,8 @@ check_template_keyword_in_nested_name_spec (tree name)
    it unchanged if there is no nested-name-specifier.  Returns the new
    scope iff there is a nested-name-specifier, or NULL_TREE otherwise.
 
+   If CHECK_DEPENDENCY_P is FALSE, names are looked up in dependent scopes.
+
    If IS_DECLARATION is TRUE, the nested-name-specifier is known to be
    part of a declaration and/or decl-specifier.  */
 
@@ -6645,9 +6647,10 @@ cp_parser_nested_name_specifier_opt (cp_parser *parser,
          /* Grab the nested-name-specifier and continue the loop.  */
          cp_parser_pre_parsed_nested_name_specifier (parser);
          /* If we originally encountered this nested-name-specifier
-            with IS_DECLARATION set to false, we will not have
+            with CHECK_DEPENDENCY_P set to true, we will not have
             resolved TYPENAME_TYPEs, so we must do so here.  */
          if (is_declaration
+             && !check_dependency_p
              && TREE_CODE (parser->scope) == TYPENAME_TYPE)
            {
              new_scope = resolve_typename_type (parser->scope,
@@ -6729,6 +6732,7 @@ cp_parser_nested_name_specifier_opt (cp_parser *parser,
         a template.  So, if we have a typename at this point, we make
         an effort to look through it.  */
       if (is_declaration
+         && !check_dependency_p
          && !typename_keyword_p
          && parser->scope
          && TREE_CODE (parser->scope) == TYPENAME_TYPE)