Add tests for type.__bases__, fix type.__bases__

Author: coolreader18

tests/snippets/types_snippet.py

@@ -43,6 +43,11 @@ class D(B, C): pass
 assert C.__subclasses__() == [D]
 assert D.__subclasses__() == []
 
+assert D.__bases__ == (B, C)
+assert A.__bases__ == (object,)
+assert B.__bases__ == (A,)
+
+
 del D
 
 try: # gc sweep is needed here for CPython...

vm/src/obj/objtype.rs

@@ -297,8 +297,12 @@ fn type_new_slot(metatype: PyClassRef, args: PyFuncArgs, vm: &VirtualMachine) ->
 
     let (name, bases, dict): (PyStringRef, PyIterable<PyClassRef>, PyDictRef) = args.bind(vm)?;
 
-    let mut bases: Vec<PyClassRef> = bases.iter(vm)?.collect::<Result<Vec<_>, _>>()?;
-    bases.push(vm.ctx.object());
+    let bases: Vec<PyClassRef> = bases.iter(vm)?.collect::<Result<Vec<_>, _>>()?;
+    let bases = if bases.is_empty() {
+        vec![vm.ctx.object()]
+    } else {
+        bases
+    };
 
     let attributes = dict.to_attributes();