[gcc r13-919] c++: auto function as function argument [PR105779]

[gcc r13-919] c++: auto function as function argument [PR105779]

[Jason Merrill]

https://gcc.gnu.org/g:72e52b88582e738c8b8bde5f85af63d3a0e15d2b

commit r13-919-g72e52b88582e738c8b8bde5f85af63d3a0e15d2b
Author: Jason Merrill <jason@redhat.com>
Date:   Tue May 31 16:17:58 2022 -0400

    c++: auto function as function argument [PR105779]
    
    This testcase demonstrates that the issue in PR105623 is not limited to
    templates, so we should do the marking in a less template-specific place.
    
            PR c++/105779
    
    gcc/cp/ChangeLog:
    
            * call.cc (resolve_args): Call mark_single_function here.
            * pt.cc (unify_one_argument): Not here.
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/cpp1y/auto-fn63.C: New test.

Diff:
---
 gcc/cp/call.cc                         |  5 +++++
 gcc/cp/pt.cc                           |  4 ----
 gcc/testsuite/g++.dg/cpp1y/auto-fn63.C | 12 ++++++++++++
 3 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc
index 85fe9b5ab85..4710c3777c5 100644
--- a/gcc/cp/call.cc
+++ b/gcc/cp/call.cc
@@ -4672,6 +4672,11 @@ resolve_args (vec<tree, va_gc> *args, tsubst_flags_t complain)
 	}
       else if (invalid_nonstatic_memfn_p (EXPR_LOCATION (arg), arg, complain))
 	return NULL;
+
+      /* Force auto deduction now.  Omit tf_warning to avoid redundant
+	 deprecated warning on deprecated-14.C.  */
+      if (!mark_single_function (arg, tf_error))
+	return NULL;
     }
   return args;
 }
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 4f0ace2644b..6de8e496859 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -22624,10 +22624,6 @@ unify_one_argument (tree tparms, tree targs, tree parm, tree arg,
 	      return unify_success (explain_p);
 	    }
 
-	  /* Force auto deduction now.  Use tf_none to avoid redundant
-	     deprecated warning on deprecated-14.C.  */
-	  mark_single_function (arg, tf_none);
-
 	  arg_expr = arg;
 	  arg = unlowered_expr_type (arg);
 	  if (arg == error_mark_node)
diff --git a/gcc/testsuite/g++.dg/cpp1y/auto-fn63.C b/gcc/testsuite/g++.dg/cpp1y/auto-fn63.C
new file mode 100644
index 00000000000..ca3bc854065
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1y/auto-fn63.C
@@ -0,0 +1,12 @@
+// PR c++/105779
+// { dg-do compile { target c++14 } }
+
+template<int>
+struct struct1
+{
+  static auto apply() { return 1; }
+};
+
+int method(int(*f)());
+
+int t = method(struct1<1>::apply);