feat(core): Support List.__setitem__ (#23)

include/mlc/core/list.h

@@ -174,7 +174,8 @@ struct UList : public ObjectRef {
                self->erase(i);
                return ret;
              })
-      .MemFn("_clear", &UListObj::clear);
+      .MemFn("_clear", &UListObj::clear)
+      .MemFn("__setitem__", &::mlc::core::ListBase::Accessor<UListObj>::SetItem);
 };
 
 template <typename T> struct ListObj : protected UListObj {

include/mlc/core/list_base.h

@@ -44,6 +44,7 @@ struct ListBase : public MLCList {
   template <typename TListObj> struct Accessor {
     MLC_INLINE static void New(int32_t num_args, const AnyView *args, Any *ret);
     MLC_INLINE static Any At(TListObj *self, int64_t i);
+    MLC_INLINE static void SetItem(TListObj *self, int64_t i, Any value);
   };
 };
 
@@ -180,6 +181,11 @@ MLC_INLINE Any ListBase::Accessor<TListObj>::At(TListObj *self, int64_t i) {
   return self->operator[](i);
 }
 
+template <typename TListObj> //
+MLC_INLINE void ListBase::Accessor<TListObj>::SetItem(TListObj *self, int64_t i, Any value) {
+  self->operator[](i) = std::move(value);
+}
+
 } // namespace core
 } // namespace mlc
 

python/mlc/core/list.py

@@ -43,6 +43,14 @@ def __getitem__(self, i: int | slice) -> T | Sequence[T]:
         else:
             raise TypeError(f"list indices must be integers or slices, not {type(i).__name__}")
 
+    def __setitem__(self, index: int, value: T) -> None:
+        length = len(self)
+        if not -length <= index < length:
+            raise IndexError(f"list assignment index out of range: {index}")
+        if index < 0:
+            index += length
+        List._C(b"__setitem__", self, index, value)
+
     def __iter__(self) -> Iterator[T]:
         return iter(self[i] for i in range(len(self)))
 

tests/python/test_core_list.py

@@ -163,3 +163,21 @@ def test_list_ne() -> None:
     b = List([1, 2, 3, 4])
     assert a != b
     assert b != a
+
+
+def test_list_setitem() -> None:
+    a = List([1, 4, 9, 16])
+    a[1] = 8
+    assert tuple(a) == (1, 8, 9, 16)
+    a[-2] = 12
+    assert tuple(a) == (1, 8, 12, 16)
+    a[-4] = 2
+    assert tuple(a) == (2, 8, 12, 16)
+
+    with pytest.raises(IndexError) as e:
+        a[4] = 20
+    assert str(e.value) == "list assignment index out of range: 4"
+
+    with pytest.raises(IndexError) as e:
+        a[-5] = 20
+    assert str(e.value) == "list assignment index out of range: -5"