Add type overloads and test for unstack

Author: asmeurer

numpy/_core/shape_base.pyi

@@ -117,6 +117,12 @@ def stack(
     casting: _CastingKind = ...
 ) -> _ArrayType: ...
 
+@overload
+def unstack(
+    array: _ArrayLike[_SCT],
+    axis: int = 0
+) -> tuple[NDArray[_SCT], ...]: ...
+
 @overload
 def block(arrays: _ArrayLike[_SCT]) -> NDArray[_SCT]: ...
 @overload

numpy/typing/tests/data/reveal/shape_base.pyi

@@ -53,3 +53,6 @@ assert_type(np.kron(AR_f8, AR_f8), npt.NDArray[np.floating[Any]])
 
 assert_type(np.tile(AR_i8, 5), npt.NDArray[np.int64])
 assert_type(np.tile(AR_LIKE_f8, [2, 2]), npt.NDArray[Any])
+
+assert_type(np.unstack(AR_i8, 5), list[npt.NDArray[np.int64]])
+assert_type(np.unstack(AR_LIKE_f8, 5), list[npt.NDArray[Any]])