P0624R2 - Default constructible and assignable stateless lambdas

	P0624R2 - Default constructible and assignable stateless lambdas
	* method.c (synthesized_method_walk): For C++2a don't mark
	sfk_constructor or sfk_copy_assignment as deleted if lambda has
	no lambda-captures.

	* g++.dg/cpp2a/lambda1.C: New test.
	* g++.dg/cpp0x/lambda/lambda-ice2.C: Adjust expected diagnostics
	for -std=c++2a.

From-SVN: r261605

gcc/cp/ChangeLog

+2018-06-14  Jakub Jelinek  <jakub@redhat.com>
+
+	P0624R2 - Default constructible and assignable stateless lambdas
+	* method.c (synthesized_method_walk): For C++2a don't mark
+	sfk_constructor or sfk_copy_assignment as deleted if lambda has
+	no lambda-captures.
+
 2018-06-14  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	* decl.c (duplicate_decls): Use DECL_SOURCE_LOCATION in

gcc/cp/method.c

@@ -1539,10 +1539,15 @@ synthesized_method_walk (tree ctype, special_function_kind sfk, bool const_p,
     {
       /* "The closure type associated with a lambda-expression has a deleted
 	 default constructor and a deleted copy assignment operator."
-         This is diagnosed in maybe_explain_implicit_delete.  */
+	 This is diagnosed in maybe_explain_implicit_delete.
+	 In C++2a, only lambda-expressions with lambda-captures have those
+	 deleted.  */
       if (LAMBDA_TYPE_P (ctype)
-	  && (sfk == sfk_constructor
-	      || sfk == sfk_copy_assignment))
+	  && (sfk == sfk_constructor || sfk == sfk_copy_assignment)
+	  && (cxx_dialect < cxx2a
+	      || LAMBDA_EXPR_CAPTURE_LIST (CLASSTYPE_LAMBDA_EXPR (ctype))
+	      || LAMBDA_EXPR_DEFAULT_CAPTURE_MODE
+				(CLASSTYPE_LAMBDA_EXPR (ctype)) != CPLD_NONE))
 	{
 	  *deleted_p = true;
 	  return;

gcc/testsuite/ChangeLog

+2018-06-14  Jakub Jelinek  <jakub@redhat.com>
+
+	P0624R2 - Default constructible and assignable stateless lambdas
+	* g++.dg/cpp2a/lambda1.C: New test.
+	* g++.dg/cpp0x/lambda/lambda-ice2.C: Adjust expected diagnostics
+	for -std=c++2a.
+
 2018-06-14  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	* g++.dg/other/static3.C: New.

gcc/testsuite/g++.dg/cpp0x/lambda/lambda-ice2.C

@@ -2,15 +2,15 @@
 // { dg-do compile { target c++11 } }
 
 template<typename F>
-decltype(F()) run(F f) // { dg-message "note" }
+decltype(F()) run(F f) // { dg-message "note" "" { target c++17_down } }
 {
-  return f();
+  return f();	// { dg-error "could not convert" "" { target c++2a } }
 }
 
 int main()
 {
-  auto l = []() { return 5; }; // { dg-message "lambda closure type" }
+  auto l = []() { return 5; }; // { dg-message "lambda closure type" "" { target c++17_down } }
 
-  run(l); // { dg-error "no match" }
-  // { dg-error "use of deleted function" "candidate explanation" { target *-*-* } 5 }
+  run(l); // { dg-error "no match" "" { target c++17_down } }
+  // { dg-error "use of deleted function" "candidate explanation" { target c++17_down } 5 }
 }

gcc/testsuite/g++.dg/cpp2a/lambda1.C

+// P0624R2
+// { dg-do compile { target c++11 } }
+
+#if __cplusplus >= 201402L
+#define A auto
+#else
+#define A int
+#endif
+
+void
+f1 ()
+{
+  auto greater = [](A x, A y) { return x > y; };	// { dg-message "a lambda closure type has a deleted (default constructor|copy assignment operator)" "" { target c++17_down } }
+  decltype (greater) gt;	// { dg-error "use of deleted function" "" { target c++17_down } }
+  gt = greater;			// { dg-error "use of deleted function" "" { target c++17_down } }
+}
+
+void
+f2 ()
+{
+  auto greater = [&](A x, A y) { return x > y; };	// { dg-message "a lambda closure type has a deleted (default constructor|copy assignment operator)" }
+  decltype (greater) gt;	// { dg-error "use of deleted function" }
+  gt = greater;			// { dg-error "use of deleted function" }
+}
+
+void
+f3 ()
+{
+  auto greater = [=](A x, A y) { return x > y; };	// { dg-message "a lambda closure type has a deleted (default constructor|copy assignment operator)" }
+  decltype (greater) gt;	// { dg-error "use of deleted function" }
+  gt = greater;			// { dg-error "use of deleted function" }
+}
+
+void
+f4 (int i)
+{
+  auto greater = [i](A x, A y) { return x > y; };	// { dg-message "a lambda closure type has a deleted (default constructor|copy assignment operator)" }
+  decltype (greater) gt;	// { dg-error "use of deleted function" }
+  gt = greater;			// { dg-error "use of deleted function" }
+}
+
+#if __cplusplus > 201703L
+void
+f5 ()
+{
+  auto greater = [](auto x, auto y) constexpr { return x > y; };
+  decltype (greater) gt;
+  static_assert (!gt (1, 2));
+  static_assert (gt (4, 3));
+  static_assert (!gt (3.5, 3.75));
+  static_assert (gt (3.5, 3.25));
+  gt = greater;
+  static_assert (!gt (1, 2));
+  static_assert (gt (4, 3));
+  static_assert (!gt (3.5, 3.75));
+  static_assert (gt (3.5, 3.25));
+}
+#endif