re PR c++/85695 (if constexpr misevaluates typedefed type value)

	PR c++/85695
	* semantics.c (finish_if_stmt_cond): See through typedefs.

	* g++.dg/cpp1z/constexpr-if22.C: New test.

From-SVN: r260049

gcc/cp/ChangeLog

+2018-05-08  Marek Polacek  <polacek@redhat.com>
+
+	PR c++/85695
+	* semantics.c (finish_if_stmt_cond): See through typedefs.
+
 2018-05-07  Jason Merrill  <jason@redhat.com>
 
 	PR c++/85646 - lambda visibility.

gcc/cp/semantics.c

@@ -736,7 +736,7 @@ finish_if_stmt_cond (tree cond, tree if_stmt)
       && !instantiation_dependent_expression_p (cond)
       /* Wait until instantiation time, since only then COND has been
 	 converted to bool.  */
-      && TREE_TYPE (cond) == boolean_type_node)
+      && TYPE_MAIN_VARIANT (TREE_TYPE (cond)) == boolean_type_node)
     {
       cond = instantiate_non_dependent_expr (cond);
       cond = cxx_constant_value (cond, NULL_TREE);

gcc/testsuite/ChangeLog

+2018-05-08  Marek Polacek  <polacek@redhat.com>
+
+	PR c++/85695
+	* g++.dg/cpp1z/constexpr-if22.C: New test.
+
 2018-05-08  Uros Bizjak  <ubizjak@gmail.com>
 
 	PR target/85693

gcc/testsuite/g++.dg/cpp1z/constexpr-if22.C

+// PR c++/85695
+// { dg-options -std=c++17 }
+
+template <typename T, T v>
+struct integral_constant {
+    using value_type = T;
+    static constexpr const value_type value = v;
+    constexpr operator value_type (void) const { return value; }
+};
+template <typename T> struct is_trivial
+    : public integral_constant<bool, __is_trivial(T)> {};
+
+template <typename T>
+T clone_object (const T& p)
+{
+    if constexpr (is_trivial<T>::value)
+        return p;
+    else
+        return p.clone();
+}
+int main (void) { return clone_object(0); }