Add native tp_descr_get for function_cls and wrapperdescr_cls

src/capi/types.h

@@ -143,6 +143,7 @@ public:
     DEFAULT_CLASS(wrapperdescr_cls);
 
     static Box* __get__(BoxedWrapperDescriptor* self, Box* inst, Box* owner);
+    static Box* descr_get(Box* self, Box* inst, Box* owner) noexcept;
     static Box* __call__(BoxedWrapperDescriptor* descr, PyObject* self, BoxedTuple* args, Box** _args);
 
     static void gcHandler(GCVisitor* v, Box* _o) {

src/runtime/capi.cpp

@@ -69,6 +69,20 @@ Box* BoxedWrapperDescriptor::__get__(BoxedWrapperDescriptor* self, Box* inst, Bo
     return new BoxedWrapperObject(self, inst);
 }
 
+Box* BoxedWrapperDescriptor::descr_get(Box* _self, Box* inst, Box* owner) noexcept {
+    RELEASE_ASSERT(_self->cls == wrapperdescr_cls, "");
+    BoxedWrapperDescriptor* self = static_cast<BoxedWrapperDescriptor*>(_self);
+
+    if (inst == None)
+        return self;
+
+    if (!isSubclass(inst->cls, self->type))
+        PyErr_Format(TypeError, "Descriptor '' for '%s' objects doesn't apply to '%s' object",
+                       getFullNameOfClass(self->type).c_str(), getFullTypeName(inst).c_str());
+
+    return new BoxedWrapperObject(self, inst);
+}
+
 Box* BoxedWrapperDescriptor::__call__(BoxedWrapperDescriptor* descr, PyObject* self, BoxedTuple* args, Box** _args) {
     RELEASE_ASSERT(descr->cls == wrapperdescr_cls, "");
 
@@ -1737,6 +1751,7 @@ void setupCAPI() {
     wrapperdescr_cls->giveAttr("__doc__",
                                new (pyston_getset_cls) BoxedGetsetDescriptor(wrapperdescrGetDoc, NULL, NULL));
     wrapperdescr_cls->freeze();
+    wrapperdescr_cls->tp_descr_get = BoxedWrapperDescriptor::descr_get;
 
     wrapperobject_cls->giveAttr(
         "__call__", new BoxedFunction(boxRTFunction((void*)BoxedWrapperObject::__call__, UNKNOWN, 1, 0, true, true)));

src/runtime/types.cpp

@@ -857,6 +857,14 @@ static Box* functionGet(BoxedFunction* self, Box* inst, Box* owner) {
     return new BoxedInstanceMethod(inst, self, owner);
 }
 
+static Box* function_descr_get(Box* self, Box* inst, Box* owner) noexcept {
+    RELEASE_ASSERT(self->cls == function_cls, "");
+
+    if (inst == None)
+        inst = NULL;
+    return new BoxedInstanceMethod(inst, self, owner);
+}
+
 static Box* functionCall(BoxedFunction* self, Box* args, Box* kwargs) {
     RELEASE_ASSERT(self->cls == function_cls, "%s", getTypeName(self));
 
@@ -2748,6 +2756,7 @@ void setupRuntime() {
     function_cls->giveAttr("__defaults__", function_cls->getattr("func_defaults"));
     function_cls->giveAttr("func_globals", function_cls->getattr("__globals__"));
     function_cls->freeze();
+    function_cls->tp_descr_get = function_descr_get;
 
     builtin_function_or_method_cls->giveAttr(
         "__module__",