Fixed bug #80596: Fix anonymous class union typehint errors

Cut off part after null byte when resolving the class name, to
avoid cutting off a larger part lateron.

Closes GH-6601.

Author: danog

NEWS

@@ -6,6 +6,8 @@ PHP                                                                        NEWS
   . Fixed bug #80523 (bogus parse error on >4GB source code). (Nikita)
   . Fixed bug #80384 (filter buffers entire read until file closed). (Adam
     Seitz, cmb)
+  . Fixed bug #80596 (Invalid union type TypeError in anonymous classes).
+    (Daniil Gentili)
 
 - BCMath:
   . Fixed bug #80545 (bcadd('a', 'a') doesn't throw an exception).

Zend/tests/type_declarations/union_types/anonymous_class.phpt

@@ -0,0 +1,30 @@
+--TEST--
+Union with anonymous class type
+--FILE--
+<?php
+
+$a = new class {
+    public function testParam(self|string $a)
+    {
+    }
+    public function test(): self|string
+    {
+        return new \stdClass;
+    }
+};
+
+try {
+    $a->testParam(null);
+} catch (\Throwable $e) {
+    echo $e->getMessage()."\n";
+}
+
+try {
+    $a->test();
+} catch (\Throwable $e) {
+    echo $e->getMessage()."\n";
+}
+?>
+--EXPECTF--
+class@anonymous(): Argument #1 ($a) must be of type class@anonymous|string, null given, called in %s on line %d
+class@anonymous::test(): Return value must be of type class@anonymous|string, stdClass returned

Zend/zend_compile.c

@@ -1167,7 +1167,15 @@ static zend_string *resolve_class_name(zend_string *name, zend_class_entry *scop
 			name = scope->parent->name;
 		}
 	}
-	return name;
+
+	/* The resolved name for anonymous classes contains null bytes. Cut off everything after the
+	 * null byte here, to avoid larger parts of the type being omitted by printing code later. */
+	size_t len = strlen(ZSTR_VAL(name));
+	if (len != ZSTR_LEN(name)) {
+		ZEND_ASSERT(scope && "This should only happen with resolved types");
+		return zend_string_init(ZSTR_VAL(name), len, 0);
+	}
+	return zend_string_copy(name);
 }
 
 zend_string *zend_type_to_string_resolved(zend_type type, zend_class_entry *scope) {
@@ -1179,11 +1187,13 @@ zend_string *zend_type_to_string_resolved(zend_type type, zend_class_entry *scop
 			if (ZEND_TYPE_HAS_CE(*list_type)) {
 				str = add_type_string(str, ZEND_TYPE_CE(*list_type)->name);
 			} else {
-				str = add_type_string(str, resolve_class_name(ZEND_TYPE_NAME(*list_type), scope));
+				zend_string *resolved = resolve_class_name(ZEND_TYPE_NAME(*list_type), scope);
+				str = add_type_string(str, resolved);
+				zend_string_release(resolved);
 			}
 		} ZEND_TYPE_LIST_FOREACH_END();
 	} else if (ZEND_TYPE_HAS_NAME(type)) {
-		str = zend_string_copy(resolve_class_name(ZEND_TYPE_NAME(type), scope));
+		str = resolve_class_name(ZEND_TYPE_NAME(type), scope);
 	} else if (ZEND_TYPE_HAS_CE(type)) {
 		str = zend_string_copy(ZEND_TYPE_CE(type)->name);
 	}