[gcc r12-3536] c++: tweak C++20 destructor template-id rule

[Jason Merrill <jason@gcc.gnu.org>]

https://gcc.gnu.org/g:f53a89fe722958d29fded71b444ff0f09b57b2c4

commit r12-3536-gf53a89fe722958d29fded71b444ff0f09b57b2c4
Author: Jason Merrill <jason@redhat.com>
Date:   Mon Sep 13 16:45:42 2021 -0400

    c++: tweak C++20 destructor template-id rule
    
    While working on a larger change to destructor lookup I noticed that this
    rule talks about declarators, but we weren't limiting the error to the case
    where we're parsing a declarator.  I don't know if this actually broke
    anything, since a CPP_TEMPLATE_ID would have to have been parsed once
    before, but it's more correct this way.
    
    gcc/cp/ChangeLog:
    
            * parser.c (cp_parser_unqualified_id): Only complain about ~A<T> in
            a declarator.

Diff:
---
 gcc/cp/parser.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index e44c5c6b57c..ab1dc81b997 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -6379,7 +6379,8 @@ cp_parser_unqualified_id (cp_parser* parser,
 
 	/* DR 2237 (C++20 only): A simple-template-id is no longer valid as the
 	   declarator-id of a constructor or destructor.  */
-	if (token->type == CPP_TEMPLATE_ID && cxx_dialect >= cxx20)
+	if (token->type == CPP_TEMPLATE_ID && declarator_p
+	    && cxx_dialect >= cxx20)
 	  {
 	    if (!cp_parser_simulate_error (parser))
 	      error_at (tilde_loc, "template-id not allowed for destructor");