Cleanup isSubclass check. Remove isInstance()

src/runtime/capi.cpp

@@ -669,7 +669,7 @@ void checkAndThrowCAPIException() {
 
     if (_type) {
         BoxedClass* type = static_cast<BoxedClass*>(_type);
-        assert(isInstance(_type, type_cls) && isSubclass(static_cast<BoxedClass*>(type), BaseException)
+        assert(isSubclass(_type->cls, type_cls) && isSubclass(static_cast<BoxedClass*>(type), BaseException)
                && "Only support throwing subclass of BaseException for now");
 
         Box* value = cur_thread_state.curexc_value;
@@ -686,7 +686,7 @@ void checkAndThrowCAPIException() {
         PyErr_Clear();
 
         // This is similar to PyErr_NormalizeException:
-        if (!isInstance(value, type)) {
+        if (!isSubclass(value->cls, type)) {
             if (value->cls == tuple_cls) {
                 value = runtimeCall(type, ArgPassSpec(0, 0, true, false), value, NULL, NULL, NULL, NULL);
             } else if (value == None) {

src/runtime/objmodel.cpp

@@ -211,18 +211,8 @@ extern "C" void my_assert(bool b) {
     assert(b);
 }
 
-bool isInstance(Box* obj, BoxedClass* cls) {
-    int rtn = _PyObject_RealIsInstance(obj, cls);
-    if (rtn < 0)
-        checkAndThrowCAPIException();
-    return rtn;
-}
-
 extern "C" bool isSubclass(BoxedClass* child, BoxedClass* parent) {
-    int rtn = _PyObject_RealIsSubclass(child, parent);
-    if (rtn < 0)
-        checkAndThrowCAPIException();
-    return rtn;
+    return PyType_IsSubtype(child, parent);
 }
 
 extern "C" void assertFail(BoxedModule* inModule, Box* msg) {
@@ -4465,7 +4455,7 @@ extern "C" Box* boxedLocalsGet(Box* boxedLocals, const char* attr, BoxedModule*
             // TODO should check the exact semantic here but it's something like:
             // If it throws a KeyError, then the variable doesn't exist so move on
             // and check the globals (below); otherwise, just propogate the exception.
-            if (!isInstance(e.value, KeyError)) {
+            if (!isSubclass(e.value->cls, KeyError)) {
                 throw;
             }
         }

src/runtime/objmodel.h

@@ -84,7 +84,6 @@ extern "C" Box* importStar(Box* from_module, BoxedModule* to_module);
 extern "C" Box** unpackIntoArray(Box* obj, int64_t expected_size);
 extern "C" void assertNameDefined(bool b, const char* name, BoxedClass* exc_cls, bool local_var_msg);
 extern "C" void assertFail(BoxedModule* inModule, Box* msg);
-extern "C" bool isInstance(Box* obj, BoxedClass* parent);
 extern "C" bool isSubclass(BoxedClass* child, BoxedClass* parent);
 extern "C" BoxedClosure* createClosure(BoxedClosure* parent_closure);