[gcc r10-10700] c++: Fox template-introduction tentative parsing in class bodies clear colon_corrects_to_scope_p [PR

[Jakub Jelinek <jakub@gcc.gnu.org>]

https://gcc.gnu.org/g:3d8d22d7bd799fbdcddb4762a97c39d6107ee077

commit r10-10700-g3d8d22d7bd799fbdcddb4762a97c39d6107ee077
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Wed Mar 30 09:16:41 2022 +0200

    c++: Fox template-introduction tentative parsing in class bodies clear colon_corrects_to_scope_p [PR105061]
    
    The concepts support (in particular template introductions from concepts TS)
    broke the following testcase, valid unnamed bitfields with dependent
    types (or even just typedefs) were diagnosed as typos (: instead of correct
    ::) in template introduction during their tentative parsing.
    The following patch fixes that by not doing this : to :: correction when
    member_p is true.
    
    2022-03-30  Jakub Jelinek  <jakub@redhat.com>
    
            PR c++/105061
            * parser.c (cp_parser_template_introduction): If member_p, temporarily
            clear parser->colon_corrects_to_scope_p around tentative parsing of
            nested name specifier.
    
            * g++.dg/concepts/pr105061.C: New test.
    
    (cherry picked from commit 4f2795218a6ba6a7b7b9b18ca7a6e390661e1608)

Diff:
---
 gcc/cp/parser.c                          |  7 +++++++
 gcc/testsuite/g++.dg/concepts/pr105061.C | 13 +++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 61f2af34688..1499bf5d258 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -29218,9 +29218,15 @@ cp_parser_template_introduction (cp_parser* parser, bool member_p)
   tree saved_scope = parser->scope;
   tree saved_object_scope = parser->object_scope;
   tree saved_qualifying_scope = parser->qualifying_scope;
+  bool saved_colon_corrects_to_scope_p = parser->colon_corrects_to_scope_p;
 
   cp_token *start_token = cp_lexer_peek_token (parser->lexer);
 
+  /* In classes don't parse valid unnamed bitfields as invalid
+     template introductions.  */
+  if (member_p)
+    parser->colon_corrects_to_scope_p = false;
+
   /* Look for the optional `::' operator.  */
   cp_parser_global_scope_opt (parser,
 			      /*current_scope_valid_p=*/false);
@@ -29241,6 +29247,7 @@ cp_parser_template_introduction (cp_parser* parser, bool member_p)
   parser->scope = saved_scope;
   parser->object_scope = saved_object_scope;
   parser->qualifying_scope = saved_qualifying_scope;
+  parser->colon_corrects_to_scope_p = saved_colon_corrects_to_scope_p;
 
   if (concept_name == error_mark_node
       || (seen_error () && !concept_definition_p (tmpl_decl)))
diff --git a/gcc/testsuite/g++.dg/concepts/pr105061.C b/gcc/testsuite/g++.dg/concepts/pr105061.C
new file mode 100644
index 00000000000..3f6f0e4d6e1
--- /dev/null
+++ b/gcc/testsuite/g++.dg/concepts/pr105061.C
@@ -0,0 +1,13 @@
+// PR c++/105061
+
+template <typename T, int U, int V>
+struct A { T : V, u : U; };
+template <int U, int V>
+struct B { unsigned : V, u : U; };
+typedef unsigned uns;
+template <int U, int V>
+struct C { uns : V, u : U; };
+
+A<unsigned int, 4, 5> a = { 13 };
+B<5, 6> b = { 26 };
+C<8, 9> c = { 42 };