fix: walk parent_class chain when looking up __clone for op_clone (#57)

compiler/pipes/convert-invoke-to-func-call.cpp

@@ -119,8 +119,11 @@ VertexPtr ConvertInvokeToFuncCallPass::on_clone(VertexAdaptor<op_clone> v_clone)
     return call_virt_clone;
   }
 
-  // clone $obj, when a class has the __clone() magic method, is replaced with { tmp = clone $obj; tmp->__clone(); $tmp }
-  if (klass->members.has_instance_method(ClassData::NAME_OF_CLONE)) {
+  // clone $obj, when a class (or any of its ancestors) has the __clone() magic method,
+  // is replaced with { tmp = clone $obj; tmp->__clone(); $tmp }
+  // find_instance_method_by_local_name walks the full parent_class chain, so an inherited
+  // __clone() from a base class is correctly invoked (fixes #57)
+  if (const auto *clone_method = klass->find_instance_method_by_local_name(ClassData::NAME_OF_CLONE)) {
     auto tmp_var = VertexAdaptor<op_var>::create().set_location(v_clone);
     tmp_var->str_val = gen_unique_name("tmp_for_clone");
     tmp_var->extra_type = op_ex_var_superlocal;
@@ -130,7 +133,7 @@ VertexPtr ConvertInvokeToFuncCallPass::on_clone(VertexAdaptor<op_clone> v_clone)
     auto call_magic_clone = VertexAdaptor<op_func_call>::create(tmp_var).set_location(v_clone);
     call_magic_clone->str_val = ClassData::NAME_OF_CLONE;
     call_magic_clone->extra_type = op_ex_func_call_arrow;
-    call_magic_clone->func_id = klass->members.get_instance_method(ClassData::NAME_OF_CLONE)->function;
+    call_magic_clone->func_id = clone_method->function;
 
     return VertexAdaptor<op_seq_rval>::create(set_clone_to_tmp, call_magic_clone, tmp_var).set_location(v_clone);
   }

tests/phpt/clone_keyword/105_inherited_clone_method.php

@@ -0,0 +1,29 @@
+@ok
+<?php
+
+// Regression test for https://github.com/VKCOM/kphp/issues/57
+// When a child class does not define __clone() but a parent does,
+// cloning an instance of the child must invoke the parent's __clone().
+
+class Base {
+  public int $value;
+
+  public function __construct(int $v) {
+    $this->value = $v;
+  }
+
+  public function __clone() {
+    $this->value *= 2;
+  }
+}
+
+class Child extends Base {
+  // No __clone() here — must inherit Base::__clone()
+}
+
+$obj = new Child(5);
+$copy = clone $obj;
+
+// Base::__clone() doubles value: original stays 5, copy becomes 10
+var_dump($obj->value);   // int(5)
+var_dump($copy->value);  // int(10)

tests/phpt/clone_keyword/106_deep_inheritance_clone.php

@@ -0,0 +1,27 @@
+@ok
+<?php
+
+// Regression for #57: multi-level inheritance — __clone defined two levels up.
+
+class GrandParent {
+  public string $log = '';
+
+  public function __clone() {
+    $this->log .= '+cloned';
+  }
+}
+
+class Parent_ extends GrandParent {
+  // no __clone
+}
+
+class Child extends Parent_ {
+  // no __clone either — must still reach GrandParent::__clone
+}
+
+$obj = new Child();
+$obj->log = 'original';
+$copy = clone $obj;
+
+var_dump($obj->log);   // string(8) "original"
+var_dump($copy->log);  // string(15) "original+cloned"