Re: [PATCH] PR libstdc++/71579 assert that type traits are not misused with an incomplete type

[Jonathan Wakely]

On 06/05/19 14:19 +0300, Antony Polukhin wrote:

@@ -924,14 +984,25 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
  template<typename _Tp>
    struct is_default_constructible
    : public __is_default_constructible_safe<_Tp>::type
-    { };
+    {
+      static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
+       "template argument must be a complete class or an unbounded array");
+    };

  /// is_constructible

This "///" comment is for Doxygen, and should remain with the
is_constructible trait, not __is_constructible_impl.

-  template<typename _Tp, typename... _Args>
-    struct is_constructible
+    template<typename _Tp, typename... _Args>
+    struct __is_constructible_impl
      : public __bool_constant<__is_constructible(_Tp, _Args...)>
    { };

+  template<typename _Tp, typename... _Args>
+    struct is_constructible
+      : public __is_constructible_impl<_Tp, _Args...>
+    {
+      static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
+       "template argument must be a complete class or an unbounded array");
+    };
+
  template<typename _Tp, bool = __is_referenceable<_Tp>::value>
    struct __is_copy_constructible_impl;

The rest looks reasonable, but I'll finish reviewing it ASAP, when I
have more time.