c++: Fix up user_provided_p [PR81349]

The standard says: "A function is user-provided if it is user-declared and
not explicitly defaulted or deleted on its first declaration."
I don't see anything about function templates having different rules here,
but user_provided_p does return true for all TEMPLATE_DECLs.

The following patch fixes it by treating as user-provided only templates
that aren't deleted.

2020-03-26  Jakub Jelinek  <jakub@redhat.com>

	PR c++/81349
	* class.c (user_provided_p): Use STRIP_TEMPLATE instead of returning
	true for all TEMPLATE_DECLs.

	* g++.dg/cpp1z/pr81349.C: New test.

gcc/cp/ChangeLog

 2020-03-26  Jakub Jelinek  <jakub@redhat.com>
 
+	PR c++/81349
+	* class.c (user_provided_p): Use STRIP_TEMPLATE instead of returning
+	true for all TEMPLATE_DECLs.
+
 	PR c++/94272
 	* cp-gimplify.c (cp_genericize_r): Handle STATEMENT_LIST.
 

gcc/cp/class.c

@@ -5159,12 +5159,10 @@ in_class_defaulted_default_constructor (tree t)
 bool
 user_provided_p (tree fn)
 {
-  if (TREE_CODE (fn) == TEMPLATE_DECL)
-    return true;
-  else
-    return (!DECL_ARTIFICIAL (fn)
-	    && !(DECL_INITIALIZED_IN_CLASS_P (fn)
-		 && (DECL_DEFAULTED_FN (fn) || DECL_DELETED_FN (fn))));
+  fn = STRIP_TEMPLATE (fn);
+  return (!DECL_ARTIFICIAL (fn)
+	  && !(DECL_INITIALIZED_IN_CLASS_P (fn)
+	       && (DECL_DEFAULTED_FN (fn) || DECL_DELETED_FN (fn))));
 }
 
 /* Returns true iff class T has a user-provided constructor.  */

gcc/testsuite/ChangeLog

 2020-03-26  Jakub Jelinek  <jakub@redhat.com>
 
+	PR c++/81349
+	* g++.dg/cpp1z/pr81349.C: New test.
+
 	PR c++/94272
 	* g++.dg/debug/pr94272.C: New test.
 

gcc/testsuite/g++.dg/cpp1z/pr81349.C

+// PR c++/81349
+// { dg-do compile { target c++17_only } }
+
+#include <type_traits>
+
+struct A {
+  A (int) = delete;
+};
+
+struct B {
+  template <typename T>
+  B (T) = delete;
+};
+
+template <typename U>
+struct C {
+  C (U) = delete;
+};
+
+template <typename U>
+struct D {
+  template <typename T>
+  D (T, U) = delete;
+};
+
+static_assert (std::is_aggregate_v<A>);
+static_assert (std::is_aggregate_v<B>);
+static_assert (std::is_aggregate_v<C<int>>);
+static_assert (std::is_aggregate_v<D<int>>);