re PR c++/84854 (ICE: unexpected expression in cxx_eval_constant_expression, at…

re PR c++/84854 (ICE: unexpected expression in cxx_eval_constant_expression, at cp/constexpr.c:4774)

	PR c++/84854
	* semantics.c (finish_if_stmt_cond): Check if the type of the condition
	is boolean.

	* g++.dg/cpp1z/constexpr-if15.C: New test.
	* g++.dg/cpp1z/constexpr-if16.C: New test.

From-SVN: r258756

gcc/cp/ChangeLog

+2018-03-22  Marek Polacek  <polacek@redhat.com>
+
+	PR c++/84854
+	* semantics.c (finish_if_stmt_cond): Check if the type of the condition
+	is boolean.
+
 2018-03-21  Jason Merrill  <jason@redhat.com>
 
 	PR c++/81311 - wrong C++17 overload resolution.

gcc/cp/semantics.c

@@ -733,7 +733,10 @@ finish_if_stmt_cond (tree cond, tree if_stmt)
   if (IF_STMT_CONSTEXPR_P (if_stmt)
       && !type_dependent_expression_p (cond)
       && require_constant_expression (cond)
-      && !value_dependent_expression_p (cond))
+      && !value_dependent_expression_p (cond)
+      /* Wait until instantiation time, since only then COND has been
+	 converted to bool.  */
+      && TREE_TYPE (cond) == boolean_type_node)
     {
       cond = instantiate_non_dependent_expr (cond);
       cond = cxx_constant_value (cond, NULL_TREE);

gcc/testsuite/ChangeLog

+2018-03-22  Marek Polacek  <polacek@redhat.com>
+
+	PR c++/84854
+	* g++.dg/cpp1z/constexpr-if15.C: New test.
+	* g++.dg/cpp1z/constexpr-if16.C: New test.
+
 2018-03-21  Joseph Myers  <joseph@codesourcery.com>
 
 	* gcc.dg/builtin-tgmath-3.c: New test.

gcc/testsuite/g++.dg/cpp1z/constexpr-if15.C

+// PR c++/84854
+// { dg-options -std=c++17 }
+
+constexpr int foo () { return 1; }
+constexpr int foo (int) { return 2; }
+
+template <typename>
+void a()
+{
+  if constexpr(foo) { };
+}

gcc/testsuite/g++.dg/cpp1z/constexpr-if16.C

+// { dg-options -std=c++17 }
+
+struct A
+{
+  constexpr operator bool () { return true; }
+  int i;
+};
+
+A a;
+
+template <class T> void f()
+{
+  constexpr bool b = a;
+  if constexpr (a) { }
+}
+
+int main()
+{
+  f<int>();
+}