Fix bug in Sliceable and rename del_item* to delitem (RustPython#4333)

* fix bug in sliceable

* fixup

Author: qingshi163

stdlib/src/array.rs

@@ -337,15 +337,15 @@ mod array {
                 fn delitem_by_index(&mut self, i: isize, vm: &VirtualMachine) -> PyResult<()> {
                     match self {
                         $(ArrayContentType::$n(v) => {
-                            v.del_item_by_index(vm, i)
+                            v.delitem_by_index(vm, i)
                         })*
                     }
                 }
 
                 fn delitem_by_slice(&mut self, slice: SaturatedSlice, vm: &VirtualMachine) -> PyResult<()> {
                     match self {
                         $(ArrayContentType::$n(v) => {
-                            v.del_item_by_slice(vm, slice)
+                            v.delitem_by_slice(vm, slice)
                         })*
                     }
                 }

vm/src/builtins/bytearray.rs

@@ -226,12 +226,10 @@ impl PyByteArray {
 
     pub fn _delitem(&self, needle: &PyObject, vm: &VirtualMachine) -> PyResult<()> {
         match SequenceIndex::try_from_borrowed_object(vm, needle, "bytearray")? {
-            SequenceIndex::Int(i) => self.try_resizable(vm)?.elements.del_item_by_index(vm, i),
+            SequenceIndex::Int(i) => self.try_resizable(vm)?.elements.delitem_by_index(vm, i),
             SequenceIndex::Slice(slice) => {
                 // TODO: delete 0 elements don't need resizable
-                self.try_resizable(vm)?
-                    .elements
-                    .del_item_by_slice(vm, slice)
+                self.try_resizable(vm)?.elements.delitem_by_slice(vm, slice)
             }
         }
     }
@@ -813,7 +811,7 @@ impl AsSequence for PyByteArray {
                 if let Some(value) = value {
                     zelf._setitem_by_index(i, value, vm)
                 } else {
-                    zelf.borrow_buf_mut().del_item_by_index(vm, i)
+                    zelf.borrow_buf_mut().delitem_by_index(vm, i)
                 }
             }),
             contains: atomic_func!(|seq, other, vm| {

vm/src/builtins/list.rs

@@ -309,8 +309,8 @@ impl PyList {
 
     fn _delitem(&self, needle: &PyObject, vm: &VirtualMachine) -> PyResult<()> {
         match SequenceIndex::try_from_borrowed_object(vm, needle, "list")? {
-            SequenceIndex::Int(i) => self.borrow_vec_mut().del_item_by_index(vm, i),
-            SequenceIndex::Slice(slice) => self.borrow_vec_mut().del_item_by_slice(vm, slice),
+            SequenceIndex::Int(i) => self.borrow_vec_mut().delitem_by_index(vm, i),
+            SequenceIndex::Slice(slice) => self.borrow_vec_mut().delitem_by_slice(vm, slice),
         }
     }
 
@@ -444,7 +444,7 @@ impl AsSequence for PyList {
                 if let Some(value) = value {
                     zelf.borrow_vec_mut().setitem_by_index(vm, i, value)
                 } else {
-                    zelf.borrow_vec_mut().del_item_by_index(vm, i)
+                    zelf.borrow_vec_mut().delitem_by_index(vm, i)
                 }
             }),
             contains: atomic_func!(|seq, target, vm| {

vm/src/sliceable.rs

@@ -86,7 +86,7 @@ where
         }
     }
 
-    fn del_item_by_index(&mut self, vm: &VirtualMachine, index: isize) -> PyResult<()> {
+    fn delitem_by_index(&mut self, vm: &VirtualMachine, index: isize) -> PyResult<()> {
         let pos = self
             .as_ref()
             .wrap_index(index)
@@ -95,11 +95,11 @@ where
         Ok(())
     }
 
-    fn del_item_by_slice(&mut self, _vm: &VirtualMachine, slice: SaturatedSlice) -> PyResult<()> {
+    fn delitem_by_slice(&mut self, _vm: &VirtualMachine, slice: SaturatedSlice) -> PyResult<()> {
         let (range, step, slice_len) = slice.adjust_indices(self.as_ref().len());
         if slice_len == 0 {
             Ok(())
-        } else if step == 1 {
+        } else if step == 1 || step == -1 {
             self.do_set_range(range, &[]);
             Ok(())
         } else {
@@ -192,15 +192,13 @@ pub trait SliceableSequenceOp {
         let sliced = if slice_len == 0 {
             Self::empty()
         } else if step == 1 {
-            if step.is_negative() {
-                self.do_slice_reverse(range)
-            } else {
-                self.do_slice(range)
-            }
-        } else if step.is_negative() {
-            self.do_stepped_slice_reverse(range, step.unsigned_abs())
-        } else {
+            self.do_slice(range)
+        } else if step == -1 {
+            self.do_slice_reverse(range)
+        } else if step.is_positive() {
             self.do_stepped_slice(range, step.unsigned_abs())
+        } else {
+            self.do_stepped_slice_reverse(range, step.unsigned_abs())
         };
         Ok(sliced)
     }