Allow self and parent to be part of an intersection type

Author: Girgias

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

@@ -0,0 +1,14 @@
+--TEST--
+Duplicate parent type
+--FILE--
+<?php
+
+class A {}
+class B extends A {
+    public function test(): parent&A&parent {
+    }
+}
+
+?>
+--EXPECTF--
+Fatal error: Duplicate type parent is redundant in %s on line %d

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

@@ -0,0 +1,13 @@
+--TEST--
+Duplicate self type
+--FILE--
+<?php
+
+class A {
+    public function test(): self&A&self {
+    }
+}
+
+?>
+--EXPECTF--
+Fatal error: Duplicate type self is redundant in %s on line %d

Zend/tests/type_declarations/intersection_types/redundant_types/duplicate_parent_type.phpt

@@ -0,0 +1,57 @@
+--TEST--
+Using self/parent/static part of an intersection
+--FILE--
+<?php
+
+interface X {}
+interface Y {}
+interface Z {}
+
+class A {
+    public function test(): self&X {
+        return $this;
+    }
+}
+class B extends A implements X {}
+class BError extends A {}
+
+class C extends B {
+    public function parentIntersection(): parent&X {
+        return new B();
+    }
+}
+class D extends B {
+    public function parentIntersection(): parent&X {
+        return new A();
+    }
+}
+
+$b = new B();
+$be = new BError();
+$c = new C();
+$d = new D();
+
+// Self tests
+var_dump($b->test());
+try {
+    var_dump($be->test());
+} catch (\TypeError $e) {
+    echo $e->getMessage(), PHP_EOL;
+}
+
+// Parent tests
+var_dump($c->parentIntersection());
+try {
+    var_dump($d->parentIntersection());
+} catch (\TypeError $e) {
+    echo $e->getMessage(), PHP_EOL;
+}
+
+?>
+--EXPECT--
+object(B)#1 (0) {
+}
+A::test(): Return value must be of type A&X, BError returned
+object(B)#6 (0) {
+}
+D::parentIntersection(): Return value must be of type B&X, A returned

Zend/tests/type_declarations/intersection_types/redundant_types/duplicate_self_type.phpt

@@ -6307,6 +6307,7 @@ static zend_type zend_compile_typename(
 		zend_ast_list *list = zend_ast_get_list(ast);
 		zend_type_list *type_list;
 
+		// TODO Is this still true if self/parent are accepted?
 		/* Allocate the type list directly on the arena as it must be a type
 		 * list of the same number of elements as the AST list has children */
 		type_list = zend_arena_alloc(&CG(arena), ZEND_TYPE_LIST_SIZE(list->children));
@@ -6317,20 +6318,14 @@ static zend_type zend_compile_typename(
 		for (uint32_t i = 0; i < list->children; i++) {
 			zend_ast *type_ast = list->child[i];
 			zend_type single_type = zend_compile_single_typename(type_ast);
-			zend_string *standard_type_str = zend_type_to_string(single_type);
 
 			/* 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,
 					"Type %s cannot be part of an intersection type", ZSTR_VAL(standard_type_str));
+				zend_string_release_ex(standard_type_str, false);
 			}
-			/* Check for "self" and "parent" too */
-			if (zend_string_equals_literal_ci(standard_type_str, "self")
-					|| zend_string_equals_literal_ci(standard_type_str, "parent")) {
-				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);
 
 			/* Add type to the type list */
 			type_list->types[type_list->num_types++] = single_type;