jsruntime: Add a vtable hook on Object for instanceof

This will hopefully allow us to customize the behavior of
QmlTypeWrapper to allow comparison QMetaObject comparison against a
QObjectWrapper lhs (i.e. foo instanceof Item will hopefully be possible)

Task-number: QTBUG-24799
Change-Id: I780c8b424ec14d6ed6f93eeac46390e2fc920000
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

3 files changed, 56 insertions, 28 deletions

diff --git a/src/qml/jsruntime/qv4object.cpp b/src/qml/jsruntime/qv4object.cpp
index eb9cb80cee..2f664c6398 100644
--- a/src/qml/jsruntime/qv4object.cpp
+++ b/src/qml/jsruntime/qv4object.cpp
@@ -1155,6 +1155,49 @@ uint Object::getLength(const Managed *m)
     return v->toUInt32();
 }
 
+// 'var' is 'V' in 15.3.5.3.
+ReturnedValue Object::instanceOf(const Object *typeObject, const Value &var)
+{
+    QV4::ExecutionEngine *engine = typeObject->internalClass()->engine;
+
+    // 15.3.5.3, Assume F is a Function object.
+    const FunctionObject *function = typeObject->as<FunctionObject>();
+    if (!function)
+        return engine->throwTypeError();
+
+    Heap::FunctionObject *f = function->d();
+    if (function->isBoundFunction())
+        f = function->cast<BoundFunction>()->target();
+
+    // 15.3.5.3, 1: HasInstance can only be used on an object
+    const Object *lhs = var.as<Object>();
+    if (!lhs)
+        return Encode(false);
+
+    // 15.3.5.3, 2
+    const Object *o = f->protoProperty();
+    if (!o) // 15.3.5.3, 3
+        return engine->throwTypeError();
+
+    Heap::Object *v = lhs->d();
+
+    // 15.3.5.3, 4
+    while (v) {
+        // 15.3.5.3, 4, a
+        v = v->prototype;
+
+        // 15.3.5.3, 4, b
+        if (!v)
+            break; // will return false
+
+        // 15.3.5.3, 4, c
+        else if (o->d() == v)
+            return Encode(true);
+    }
+
+    return Encode(false);
+}
+
 bool Object::setArrayLength(uint newLen)
 {
     Q_ASSERT(isArrayObject());
diff --git a/src/qml/jsruntime/qv4object_p.h b/src/qml/jsruntime/qv4object_p.h
index 4a78690f47..6a543ae1a8 100644
--- a/src/qml/jsruntime/qv4object_p.h
+++ b/src/qml/jsruntime/qv4object_p.h
@@ -140,6 +140,7 @@ struct ObjectVTable
     void (*setLookup)(Managed *m, Lookup *l, const Value &v);
     uint (*getLength)(const Managed *m);
     void (*advanceIterator)(Managed *m, ObjectIterator *it, Value *name, uint *index, Property *p, PropertyAttributes *attributes);
+    ReturnedValue (*instanceOf)(const Object *typeObject, const Value &var);
 };
 
 #define DEFINE_OBJECT_VTABLE_BASE(classname) \
@@ -159,7 +160,8 @@ const QV4::ObjectVTable classname::static_vtbl =    \
     getLookup,                                  \
     setLookup,                                  \
     getLength,                                  \
-    advanceIterator                            \
+    advanceIterator,                            \
+    instanceOf                                  \
 }
 
 #define DEFINE_OBJECT_VTABLE(classname) \
@@ -351,6 +353,8 @@ public:
     void advanceIterator(ObjectIterator *it, Value *name, uint *index, Property *p, PropertyAttributes *attributes)
     { vtable()->advanceIterator(this, it, name, index, p, attributes); }
     uint getLength() const { return vtable()->getLength(this); }
+    ReturnedValue instanceOf(const Value &var) const
+    { return vtable()->instanceOf(this, var); }
 
     inline void construct(Scope &scope, CallData *d) const
     { return vtable()->construct(this, scope, d); }
@@ -372,6 +376,7 @@ protected:
     static void setLookup(Managed *m, Lookup *l, const Value &v);
     static void advanceIterator(Managed *m, ObjectIterator *it, Value *name, uint *index, Property *p, PropertyAttributes *attributes);
     static uint getLength(const Managed *m);
+    static ReturnedValue instanceOf(const Object *typeObject, const Value &var);
 
 private:
     ReturnedValue internalGet(String *name, bool *hasProperty) const;
diff --git a/src/qml/jsruntime/qv4runtime.cpp b/src/qml/jsruntime/qv4runtime.cpp
index 023a739e33..7f184f8221 100644
--- a/src/qml/jsruntime/qv4runtime.cpp
+++ b/src/qml/jsruntime/qv4runtime.cpp
@@ -343,35 +343,15 @@ ReturnedValue Runtime::method_deleteName(ExecutionEngine *engine, int nameIndex)
     return Encode(engine->currentContext->deleteProperty(name));
 }
 
-QV4::ReturnedValue Runtime::method_instanceof(ExecutionEngine *engine, const Value &left, const Value &right)
+QV4::ReturnedValue Runtime::method_instanceof(ExecutionEngine *engine, const Value &lval, const Value &rval)
 {
-    const FunctionObject *function = right.as<FunctionObject>();
-    if (!function)
-        return engine->throwTypeError();
-
-    Heap::FunctionObject *f = function->d();
-    if (function->isBoundFunction())
-        f = function->cast<BoundFunction>()->target();
-
-    const Object *o = left.as<Object>();
-    if (!o)
-        return Encode(false);
-    Heap::Object *v = o->d();
-
-    o = f->protoProperty();
-    if (!o)
-        return engine->throwTypeError();
-
-    while (v) {
-        v = v->prototype;
-
-        if (!v)
-            break;
-        else if (o->d() == v)
-            return Encode(true);
-    }
+    // 11.8.6, 5: rval must be an Object
+    const Object *rhs = rval.as<Object>();
+    if (!rhs)
+       return engine->throwTypeError();
 
-    return Encode(false);
+    // 11.8.6, 7: call "HasInstance", which we term instanceOf, and return the result.
+    return rhs->instanceOf(lval);
 }
 
 QV4::ReturnedValue Runtime::method_in(ExecutionEngine *engine, const Value &left, const Value &right)