feat(core): Support List.__add__ (#24)

Author: potatomashed

python/mlc/core/list.py

@@ -54,6 +54,20 @@ def __setitem__(self, index: int, value: T) -> None:
     def __iter__(self) -> Iterator[T]:
         return iter(self[i] for i in range(len(self)))
 
+    def __add__(self, other: Sequence[T]) -> List[T]:
+        if not isinstance(other, (list, tuple, List)):
+            return NotImplemented
+        result = List(self)
+        result.extend(other)
+        return result
+
+    def __radd__(self, other: Sequence[T]) -> List[T]:
+        if not isinstance(other, (list, tuple)):
+            return NotImplemented
+        result = List(other)
+        result.extend(self)
+        return result
+
     def insert(self, i: int, x: T) -> None:
         i = _normalize_index(i, len(self) + 1)
         return List._C(b"_insert", self, i, x)

tests/python/test_core_list.py

@@ -1,3 +1,4 @@
+from collections.abc import Sequence
 from typing import Any
 
 import pytest
@@ -181,3 +182,19 @@ def test_list_setitem() -> None:
     with pytest.raises(IndexError) as e:
         a[-5] = 20
     assert str(e.value) == "list assignment index out of range: -5"
+
+
+@pytest.mark.parametrize(
+    "a, b",
+    [
+        (List([1, 2, 3]), [4, 5, 6]),
+        (List([1, 2, 3]), (4, 5, 6)),
+        (List([1, 2, 3]), List([4, 5, 6])),
+        ([1, 2, 3], List([4, 5, 6])),
+        ((1, 2, 3), List([4, 5, 6])),
+    ],
+)
+def test_list_concat(a: Sequence[int], b: Sequence[int]) -> None:
+    c = a + b  # type: ignore[operator]
+    assert isinstance(c, List)
+    assert c == [1, 2, 3, 4, 5, 6]