iter: remove PyStrReverseIterator

This commit removes `PyStrReverseIterator` and its traits for using
general `PyReverseSequenceIterator` for `PyStr` type.

In previous rustpython, `PyStrReverseIterator` type registered in
`TypeZoo`, even it had no methods(e.g. `length_hint`, `reduce`, `setstate`)

Therefore, by removing `PyStrReverseIterator`, `PyStr` enable to use
`PySequenceReverseIterator`.

Signed-off-by: snowapril <sinjihng@gmail.com>

vm/src/builtins/make_module.rs

@@ -720,7 +720,7 @@ mod decl {
             vm.get_method_or_type_error(obj.clone(), "__getitem__", || {
                 "argument to reversed() must be a sequence".to_owned()
             })?;
-            let len = vm.obj_len(&obj)? as isize;
+            let len = vm.obj_len(&obj)?;
             let obj_iterator = PyReverseSequenceIterator::new(obj, len);
             Ok(obj_iterator.into_object(vm))
         }

vm/src/builtins/pystr.rs

@@ -202,45 +202,6 @@ impl PyIter for PyStrIterator {
     }
 }
 
-#[pyclass(module = false, name = "str_reverseiterator")]
-#[derive(Debug)]
-pub struct PyStrReverseIterator {
-    string: PyStrRef,
-    position: PyAtomic<usize>,
-}
-
-impl PyValue for PyStrReverseIterator {
-    fn class(vm: &VirtualMachine) -> &PyTypeRef {
-        &vm.ctx.types.str_reverseiterator_type
-    }
-}
-
-#[pyimpl(with(PyIter))]
-impl PyStrReverseIterator {}
-
-impl PyIter for PyStrReverseIterator {
-    fn next(zelf: &PyRef<Self>, vm: &VirtualMachine) -> PyResult {
-        let value = &*zelf.string.value;
-        let mut end = zelf.position.load(atomic::Ordering::Relaxed);
-        loop {
-            let ch = value[..end]
-                .chars()
-                .next_back()
-                .ok_or_else(|| vm.new_stop_iteration())?;
-
-            match zelf.position.compare_exchange_weak(
-                end,
-                end - ch.len_utf8(),
-                atomic::Ordering::Release,
-                atomic::Ordering::Relaxed,
-            ) {
-                Ok(_) => break Ok(ch.into_pyobject(vm)),
-                Err(cur) => end = cur,
-            }
-        }
-    }
-}
-
 #[derive(FromArgs)]
 struct StrArgs {
     #[pyarg(any, optional)]
@@ -1126,14 +1087,6 @@ impl PyStr {
     fn encode(zelf: PyRef<Self>, args: EncodeArgs, vm: &VirtualMachine) -> PyResult<PyBytesRef> {
         encode_string(zelf, args.encoding, args.errors, vm)
     }
-
-    #[pymethod(magic)]
-    fn reversed(zelf: PyRef<Self>) -> PyStrReverseIterator {
-        PyStrReverseIterator {
-            position: Radium::new(zelf.byte_len()),
-            string: zelf,
-        }
-    }
 }
 
 impl PyStrRef {
@@ -1254,7 +1207,6 @@ pub fn init(ctx: &PyContext) {
     PyStr::extend_class(ctx, &ctx.types.str_type);
 
     PyStrIterator::extend_class(ctx, &ctx.types.str_iterator_type);
-    PyStrReverseIterator::extend_class(ctx, &ctx.types.str_reverseiterator_type);
 }
 
 impl PySliceableSequence for PyStr {

vm/src/types.rs

@@ -74,7 +74,6 @@ pub struct TypeZoo {
     pub list_iterator_type: PyTypeRef,
     pub list_reverseiterator_type: PyTypeRef,
     pub str_iterator_type: PyTypeRef,
-    pub str_reverseiterator_type: PyTypeRef,
     pub dict_keyiterator_type: PyTypeRef,
     pub dict_reversekeyiterator_type: PyTypeRef,
     pub dict_valueiterator_type: PyTypeRef,
@@ -193,7 +192,6 @@ impl TypeZoo {
             longrange_iterator_type: range::PyLongRangeIterator::init_bare_type().clone(),
             set_iterator_type: set::PySetIterator::init_bare_type().clone(),
             str_iterator_type: pystr::PyStrIterator::init_bare_type().clone(),
-            str_reverseiterator_type: pystr::PyStrReverseIterator::init_bare_type().clone(),
             traceback_type: traceback::PyTraceback::init_bare_type().clone(),
             tuple_iterator_type: tuple::PyTupleIterator::init_bare_type().clone(),
             weakproxy_type: weakproxy::PyWeakProxy::init_bare_type().clone(),