[gcc r15-3324] c++: fix used but not defined warning for friend

[Jason Merrill via Gcc-cvs]

https://gcc.gnu.org/g:f93a38f3fc8b20942896d037f3833d6b383dd3d8

commit r15-3324-gf93a38f3fc8b20942896d037f3833d6b383dd3d8
Author: Jason Merrill <ja...@redhat.com>
Date:   Thu Aug 29 13:27:13 2024 -0400

    c++: fix used but not defined warning for friend
    
    Here limit_bad_template_recursion avoids instantiating foo, and then we
    wrongly warn that it isn't defined, because as a non-template (but
    templated) friend DECL_TEMPLATE_INSTANTIATION is false.
    
    gcc/cp/ChangeLog:
    
            * decl2.cc (c_parse_final_cleanups): Also check
            DECL_FRIEND_PSEUDO_TEMPLATE_INSTANTIATION.
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/diagnostic/used-inline1.C: New test.

Diff:
---
 gcc/cp/decl2.cc                                |  3 ++-
 gcc/testsuite/g++.dg/diagnostic/used-inline1.C | 12 ++++++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/gcc/cp/decl2.cc b/gcc/cp/decl2.cc
index e9ae979896c5..c67e3e0c15f9 100644
--- a/gcc/cp/decl2.cc
+++ b/gcc/cp/decl2.cc
@@ -5559,7 +5559,8 @@ c_parse_final_cleanups (void)
          && !(header_module_p ()
               && (DECL_DEFAULTED_FN (decl) || decl_tls_wrapper_p (decl)))
          /* Don't complain if the template was defined.  */
-         && !(DECL_TEMPLATE_INSTANTIATION (decl)
+         && !((DECL_TEMPLATE_INSTANTIATION (decl)
+               || DECL_FRIEND_PSEUDO_TEMPLATE_INSTANTIATION (decl))
               && DECL_INITIAL (DECL_TEMPLATE_RESULT
                                (template_for_substitution (decl))))
          && warning_at (DECL_SOURCE_LOCATION (decl), 0,
diff --git a/gcc/testsuite/g++.dg/diagnostic/used-inline1.C 
b/gcc/testsuite/g++.dg/diagnostic/used-inline1.C
new file mode 100644
index 000000000000..ce4882eb9945
--- /dev/null
+++ b/gcc/testsuite/g++.dg/diagnostic/used-inline1.C
@@ -0,0 +1,12 @@
+template <class T> struct A {
+  friend void foo(A*) { }      // { dg-bogus "never defined" }
+  void bar() {
+    baz(this);                 // { dg-error "baz" }
+    foo(this);
+  }
+};
+
+int main()
+{
+  A<int>().bar();
+}