c++: auto member function and auto variable [PR106893]

As with PR105623, we need to call mark_single_function sooner to
resolve the type of a BASELINK.

	PR c++/106893
	PR c++/90451

gcc/cp/ChangeLog:

	* decl.cc (cp_finish_decl): Call mark_single_function.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp1y/auto-fn65.C: New test.

gcc/cp/decl.cc

@@ -8140,6 +8140,9 @@ cp_finish_decl (tree decl, tree init, bool init_const_expr_p,
 	    d_init = build_x_compound_expr_from_list (d_init, ELK_INIT,
 						      tf_warning_or_error);
 	  d_init = resolve_nondeduced_context (d_init, tf_warning_or_error);
+	  /* Force auto deduction now.  Use tf_none to avoid redundant warnings
+	     on deprecated-14.C.  */
+	  mark_single_function (d_init, tf_none);
 	}
       enum auto_deduction_context adc = adc_variable_type;
       if (DECL_DECOMPOSITION_P (decl))

gcc/testsuite/g++.dg/cpp1y/auto-fn65.C

+// PR c++/106893
+// { dg-do compile { target c++14 } }
+
+template <typename T>
+struct CoordTraits
+{
+  static auto GetX(T const &p) { return 1; }
+};
+typedef CoordTraits<int> Traits;
+static constexpr auto GetX = Traits::GetX;