[gcc r12-6025] c++: delayed noexcept in member function template [PR99980]

[Marek Polacek <mpolacek@gcc.gnu.org>]

https://gcc.gnu.org/g:06041b2c67a5d4d0941c53990f0438a309703ed0

commit r12-6025-g06041b2c67a5d4d0941c53990f0438a309703ed0
Author: Marek Polacek <polacek@redhat.com>
Date:   Wed Dec 15 17:41:53 2021 -0500

    c++: delayed noexcept in member function template [PR99980]
    
    Some time ago I noticed that we don't properly delay parsing of
    noexcept for member function templates.  This patch fixes that.
    
    It didn't work because even though we set CP_PARSER_FLAGS_DELAY_NOEXCEPT
    in cp_parser_member_declaration, member template declarations take
    a different path: we call cp_parser_template_declaration and return
    prior to setting the flag.
    
            PR c++/99980
    
    gcc/cp/ChangeLog:
    
            * parser.c (cp_parser_single_declaration): Maybe pass
            CP_PARSER_FLAGS_DELAY_NOEXCEPT down to cp_parser_init_declarator.
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/cpp0x/noexcept71.C: New test.

Diff:
---
 gcc/cp/parser.c                         |  7 ++++++-
 gcc/testsuite/g++.dg/cpp0x/noexcept71.C | 31 +++++++++++++++++++++++++++++++
 2 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 9cf74357ac9..44eed7ea638 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -31673,8 +31673,13 @@ cp_parser_single_declaration (cp_parser* parser,
       && (cp_lexer_next_token_is_not (parser->lexer, CPP_SEMICOLON)
 	  || decl_specifiers.type != error_mark_node))
     {
+      int flags = CP_PARSER_FLAGS_TYPENAME_OPTIONAL;
+      /* We don't delay parsing for friends, though CWG 2510 may change
+	 that.  */
+      if (member_p && !(friend_p && *friend_p))
+	flags |= CP_PARSER_FLAGS_DELAY_NOEXCEPT;
       decl = cp_parser_init_declarator (parser,
-					CP_PARSER_FLAGS_TYPENAME_OPTIONAL,
+					flags,
 				        &decl_specifiers,
 				        checks,
 				        /*function_definition_allowed_p=*/true,
diff --git a/gcc/testsuite/g++.dg/cpp0x/noexcept71.C b/gcc/testsuite/g++.dg/cpp0x/noexcept71.C
new file mode 100644
index 00000000000..361d6ad7b60
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/noexcept71.C
@@ -0,0 +1,31 @@
+// PR c++/99980
+// { dg-do compile { target c++11 } }
+
+#define SA(X) static_assert(X, #X)
+
+struct S {
+  template<typename T>
+  void f(T) noexcept(B);
+
+  struct N {
+    template<typename T>
+    void f2(T) noexcept(B);
+  };
+
+  static constexpr bool B = true;
+};
+
+S s;
+SA(noexcept(s.f(10)));
+S::N n;
+SA(noexcept(n.f2(10)));
+
+struct Bad {
+  template<typename T>
+  using U = void() noexcept(B); // { dg-error "not declared" }
+
+  template<typename T>
+  friend void friendo() noexcept(B); // { dg-error "not declared" }
+
+  static constexpr bool B = true;
+};