+ /* Return the diagnostic message string if TYPE is not valid as a
+ function parameter type, NULL otherwise. */
+ const char *(*invalid_parameter_type) (const_tree type);
+
+ /* Return the diagnostic message string if TYPE is not valid as a
+ function return type, NULL otherwise. */
+ const char *(*invalid_return_type) (const_tree type);
+
+ /* If values of TYPE are promoted to some other type when used in
+ expressions (analogous to the integer promotions), return that type,
+ or NULL_TREE otherwise. */
+ tree (*promoted_type) (const_tree type);
+
+ /* Convert EXPR to TYPE, if target-specific types with special conversion
+ rules are involved. Return the converted expression, or NULL to apply
+ the standard conversion rules. */
+ tree (*convert_to_type) (tree type, tree expr);
+