[libcxx-commits] [libcxx] r359162 - Update test to better check for the non-constexpr-ness of a move constructor. Fixes PR#41577.

[Marshall Clow via libcxx-commits]

Author: marshall
Date: Wed Apr 24 19:12:51 2019
New Revision: 359162

URL: http://llvm.org/viewvc/llvm-project?rev=359162&view=rev
Log:
Update test to better check for the non-constexpr-ness of a move constructor. Fixes PR#41577.

Modified:
    libcxx/trunk/test/std/utilities/optional/optional.object/optional.object.ctor/move.fail.cpp

Modified: libcxx/trunk/test/std/utilities/optional/optional.object/optional.object.ctor/move.fail.cpp
URL: http://llvm.org/viewvc/llvm-project/libcxx/trunk/test/std/utilities/optional/optional.object/optional.object.ctor/move.fail.cpp?rev=359162&r1=359161&r2=359162&view=diff
==============================================================================
--- libcxx/trunk/test/std/utilities/optional/optional.object/optional.object.ctor/move.fail.cpp (original)
+++ libcxx/trunk/test/std/utilities/optional/optional.object/optional.object.ctor/move.fail.cpp Wed Apr 24 19:12:51 2019
@@ -10,8 +10,17 @@
 // <optional>
 
 // constexpr optional(const optional<T>&& rhs);
+//  C++17 said:
 //   If is_trivially_move_constructible_v<T> is true,
 //    this constructor shall be a constexpr constructor.
+//
+//  P0602 changed this to:
+//     If is_trivially_move_constructible_v<T> is true, this constructor is trivial.
+//
+//  which means that it can't be constexpr if T is not trivially move-constructible,
+//    because you have to do a placement new to get the value into place.
+//    Except in the case where it is moving from an empty optional - that could be
+//    made to be constexpr (and libstdc++ does so).
 
 #include <optional>
 #include <type_traits>
@@ -23,16 +32,22 @@ struct S {
     constexpr S()   : v_(0) {}
     S(int v)        : v_(v) {}
     constexpr S(const S  &rhs) : v_(rhs.v_) {} // not trivially moveable
-    constexpr S(const S &&rhs) : v_(rhs.v_) {} // not trivially moveable
+    constexpr S(      S &&rhs) : v_(rhs.v_) {} // not trivially moveable
     int v_;
     };
 
 
+constexpr bool test() // expected-error {{constexpr function never produces a constant expression}}
+{
+    std::optional<S> o1{3};
+    std::optional<S> o2 = std::move(o1);
+    return o2.has_value();  // return -something-
+}
+
+
 int main(int, char**)
 {
     static_assert (!std::is_trivially_move_constructible_v<S>, "" );
-    constexpr std::optional<S> o1;
-    constexpr std::optional<S> o2 = std::move(o1);  // not constexpr
-
-  return 0;
+    static_assert (test(), "");  // expected-error {{static_assert expression is not an integral constant expression}}
+    return 0;
 }