Make invalid types in intersection more robust

Author: Girgias

Zend/tests/type_declarations/intersection_types/invalid_types/invalid_iterable_type.phpt

@@ -7,4 +7,4 @@ function foo(): iterable&Iterator {}
 
 ?>
 --EXPECTF--
-Fatal error: Type iterable cannot be part of an intersection type in %s on line %d
+Fatal error: Type Traversable|array cannot be part of an intersection type in %s on line %d

Zend/zend_compile.c

@@ -6275,11 +6275,15 @@ static zend_type zend_compile_typename(
 			zend_ast *type_ast = list->child[i];
 			zend_type single_type = zend_compile_single_typename(type_ast);
 
-			/* An intersection of standard types cannot exist so invalidate it */
-			/* Check for iterable early */
-			if (ZEND_TYPE_IS_ITERABLE_FALLBACK(single_type)) {
-				zend_error_noreturn(E_COMPILE_ERROR, "Type iterable cannot be part of an intersection type");
+			/* An intersection of union types cannot exist so invalidate it
+			 * Currently only can happen with iterable getting canonicalized to Traversable|array */
+			if (ZEND_TYPE_IS_UNION(single_type)) {
+				zend_string *standard_type_str = zend_type_to_string(single_type);
+				zend_error_noreturn(E_COMPILE_ERROR,
+					"Type %s cannot be part of an intersection type", ZSTR_VAL(standard_type_str));
+				zend_string_release_ex(standard_type_str, false);
 			}
+			/* An intersection of standard types cannot exist so invalidate it */
 			if (ZEND_TYPE_IS_ONLY_MASK(single_type)) {
 				zend_string *standard_type_str = zend_type_to_string(single_type);
 				zend_error_noreturn(E_COMPILE_ERROR,