re PR c++/67411 (internal compiler error: in tsubst_copy, at cp/pt.c:13473)

	PR c++/67411

	* decl2.c (decl_maybe_constant_var_p): A proxy isn't constant.

From-SVN: r231862

gcc/cp/ChangeLog

+2015-12-20  Jason Merrill  <jason@redhat.com>
+
+	PR c++/67411
+	* decl2.c (decl_maybe_constant_var_p): A proxy isn't constant.
+
 2015-12-18  Patrick Palka  <ppalka@gcc.gnu.org>
 
 	PR c++/68978

gcc/cp/decl2.c

@@ -4222,6 +4222,9 @@ decl_maybe_constant_var_p (tree decl)
     return false;
   if (DECL_DECLARED_CONSTEXPR_P (decl))
     return true;
+  if (DECL_VALUE_EXPR (decl))
+    /* A proxy isn't constant.  */
+    return false;
   return (CP_TYPE_CONST_NON_VOLATILE_P (type)
 	  && INTEGRAL_OR_ENUMERATION_TYPE_P (type));
 }

gcc/testsuite/g++.dg/cpp1y/lambda-generic-const1.C

+// PR c++/67411
+// { dg-do compile { target c++14 } }
+
+template <class T>
+void f()
+{
+  int i = 42;
+  [x = i] {
+    [&](auto) {
+      [=] { return x; }();
+    }(1);
+  }();
+}
+
+int main()
+{
+  f<int>();
+}