Fix prototype for trait methods

Fixes GH-14009

Author: iluuu1994

Zend/tests/gh14009.phpt

@@ -0,0 +1,41 @@
+--TEST--
+GH-14009: Traits inherit prototype
+--FILE--
+<?php
+
+class P {
+    protected function common() {
+        throw new Exception('Unreachable');
+    }
+}
+
+class A extends P {
+    public function test(P $sibling) {
+        $sibling->common();
+    }
+}
+
+class B extends P {
+    protected function common() {
+        echo __METHOD__, "\n";
+    }
+}
+
+trait T {
+    protected function common() {
+        echo __METHOD__, "\n";
+    }
+}
+
+class C extends P {
+    use T;
+}
+
+$a = new A();
+$a->test(new B());
+$a->test(new C());
+
+?>
+--EXPECT--
+B::common
+T::common

Zend/zend_inheritance.c

@@ -1146,20 +1146,24 @@ static zend_always_inline inheritance_status do_inheritance_check_on_method_ex(
 		parent = proto;
 	}
 
-	if (!check_only && child->common.prototype != proto && child_zv) {
+	if (!check_only && child->common.prototype != proto) {
 		do {
+			bool copied = false;
 			if (child->common.scope != ce && child->type == ZEND_USER_FUNCTION) {
 				if (ce->ce_flags & ZEND_ACC_INTERFACE) {
 					/* Few parent interfaces contain the same method */
 					break;
-				} else {
+				} else if (child_zv) {
 					/* op_array wasn't duplicated yet */
 					zend_function *new_function = zend_arena_alloc(&CG(arena), sizeof(zend_op_array));
 					memcpy(new_function, child, sizeof(zend_op_array));
 					Z_PTR_P(child_zv) = child = new_function;
+					copied = true;
 				}
 			}
-			child->common.prototype = proto;
+			if (copied || child_scope == ce) {
+				child->common.prototype = proto;
+			}
 		} while (0);
 	}