re PR c++/87093 (is_constructible (__is_constructible() instrinsic) explicitly…

re PR c++/87093 (is_constructible (__is_constructible() instrinsic) explicitly instantiates conversion member function of source)

PR c++/87093

gcc/cp

PR c++/87093
* method.c (constructible_expr): We're in an unevaluated context
in all cases, not just for class targets.

testsuite/

PR c++/87093
* g++.dg/ext/is_constructible2.C: New.

From-SVN: r264253

gcc/cp/ChangeLog

+2018-09-13  Ville Voutilainen  <ville.voutilainen@gmail.com>
+
+	PR c++/87093
+	* method.c (constructible_expr): We're in an unevaluated context
+	in all cases, not just for class targets.
+
 2018-09-12  David Malcolm  <dmalcolm@redhat.com>
 
 	PR c++/85110

gcc/cp/method.c

@@ -1144,11 +1144,11 @@ static tree
 constructible_expr (tree to, tree from)
 {
   tree expr;
+  cp_unevaluated cp_uneval_guard;
   if (CLASS_TYPE_P (to))
     {
       tree ctype = to;
       vec<tree, va_gc> *args = NULL;
-      cp_unevaluated cp_uneval_guard;
       if (!TYPE_REF_P (to))
 	to = cp_build_reference_type (to, /*rval*/false);
       tree ob = build_stub_object (to);

gcc/testsuite/g++.dg/ext/is_constructible2.C

+// { dg-do compile { target c++11 } }
+
+#include <type_traits>
+
+template <typename T> struct x {
+  operator bool() {
+    static_assert(!std::is_same<T, T>::value, "");
+    return false;
+  }
+};
+
+static constexpr auto a = __is_constructible(bool, x<int>);