Makes args of type.__prepare__ optional, refs RustPython#2762

Author: sobolevn

extra_tests/snippets/builtin_type.py

@@ -123,3 +123,17 @@ def custom_func():
     pass
 
 assert custom_func.__qualname__ == 'custom_func'
+
+
+# Regression to
+# https://github.com/RustPython/RustPython/issues/2762
+
+assert type.__prepare__() == {}
+assert type.__prepare__('name') == {}
+assert type.__prepare__('name', object) == {}
+assert type.__prepare__('name', (bytes, str)) == {}
+assert type.__prepare__(a=1, b=2) == {}
+assert type.__prepare__('name', (object, int), kw=True) == {}
+
+assert int.__prepare__() == {}
+assert int.__prepare__('name', (object, int), kw=True) == {}

vm/src/builtins/pytype.rs

@@ -16,7 +16,7 @@ use super::staticmethod::PyStaticMethod;
 use super::tuple::PyTuple;
 use super::weakref::PyWeak;
 use crate::builtins::tuple::PyTupleTyped;
-use crate::function::{FuncArgs, KwArgs};
+use crate::function::{FuncArgs, KwArgs, OptionalArg};
 use crate::slots::{self, Callable, PyTpFlags, PyTypeSlots, SlotGetattro, SlotSetattro};
 use crate::utils::Either;
 use crate::vm::VirtualMachine;
@@ -345,8 +345,8 @@ impl PyType {
 
     #[pymethod(magic)]
     fn prepare(
-        _name: PyStrRef,
-        _bases: PyObjectRef,
+        _name: OptionalArg<PyStrRef>,
+        _bases: OptionalArg<PyObjectRef>,
         _kwargs: KwArgs,
         vm: &VirtualMachine,
     ) -> PyDictRef {