re PR c++/56438 (ICE in value_dependent_expression_p, at cp/pt.c:19551)

	PR c++/56438
	* semantics.c (potential_constant_expression_1): In C++98, a cast
	to non-integral type can't be a constant expression.

From-SVN: r196274

gcc/cp/ChangeLog

+2013-02-25  Jason Merrill  <jason@redhat.com>
+
+	PR c++/56438
+	* semantics.c (potential_constant_expression_1): In C++98, a cast
+	to non-integral type can't be a constant expression.
+
 2013-02-24  Jakub Jelinek  <jakub@redhat.com>
 
 	PR c++/56403

gcc/cp/semantics.c

@@ -8607,6 +8607,18 @@ potential_constant_expression_1 (tree t, bool want_rval, tsubst_flags_t flags)
     case STATIC_CAST_EXPR:
     case REINTERPRET_CAST_EXPR:
     case IMPLICIT_CONV_EXPR:
+      if (cxx_dialect < cxx0x
+	  && !dependent_type_p (TREE_TYPE (t))
+	  && !INTEGRAL_OR_ENUMERATION_TYPE_P (TREE_TYPE (t)))
+	/* In C++98, a conversion to non-integral type can't be part of a
+	   constant expression.  */
+	{
+	  if (flags & tf_error)
+	    error ("cast to non-integral type %qT in a constant expression",
+		   TREE_TYPE (t));
+	  return false;
+	}
+
       return (potential_constant_expression_1
 	      (TREE_OPERAND (t, 0),
 	       TREE_CODE (TREE_TYPE (t)) != REFERENCE_TYPE, flags));

gcc/testsuite/g++.dg/template/cast3.C

+// PR c++/56438
+
+struct A { };
+A& operator<<(A&, const char*);
+
+struct B {
+  int size();
+};
+
+struct C { };
+
+template <class S, class T>
+S bar(const S& s, const T& t) {
+  return s;
+}
+
+template<class S, class T>
+void foo() {
+  A a;
+  B b;
+  a << bar(b.size(), C());	// { dg-error "no match" }
+}