Ensure our builtin constructors are subclassable

Respect the newTarget passed into those constructors and make
sure we set up the proto chain correctly.

Change-Id: I3d12c7dbef4b33660a6715d73e9fb0f89105167a
Fixes: QTBUG-71138
Reviewed-by: Erik Verbruggen <erik.verbruggen@qt.io>

1 files changed, 4 insertions, 1 deletions

diff --git a/src/qml/jsruntime/qv4promiseobject.cpp b/src/qml/jsruntime/qv4promiseobject.cpp
index a955e5eb6a..8450655334 100644
--- a/src/qml/jsruntime/qv4promiseobject.cpp
+++ b/src/qml/jsruntime/qv4promiseobject.cpp
@@ -364,7 +364,7 @@ void Heap::RejectWrapper::init()
 }
 
 
-ReturnedValue PromiseCtor::virtualCallAsConstructor(const FunctionObject *f, const Value *argv, int argc, const Value *)
+ReturnedValue PromiseCtor::virtualCallAsConstructor(const FunctionObject *f, const Value *argv, int argc, const Value *newTarget)
 {
     Scope scope(f);
 
@@ -396,6 +396,9 @@ ReturnedValue PromiseCtor::virtualCallAsConstructor(const FunctionObject *f, con
         a->d()->resolution.set(scope.engine, Value::fromReturnedValue(scope.engine->catchException()));
     }
 
+    if (newTarget)
+        a->setProtoFromNewTarget(newTarget);
+
     return a->asReturnedValue();
 }