Note np.array_api.can_cast() does not use np.can_cast()

Original NumPy Commit: 995f5464b6c5d8569e159a96c6af106721a4e6d5

Author: honno

array_api_strict/_data_type_functions.py

@@ -56,10 +56,15 @@ def can_cast(from_: Union[Dtype, Array], to: Dtype, /) -> bool:
         raise TypeError(f"{from_=}, but should be an array_api array or dtype")
     if to not in _all_dtypes:
         raise TypeError(f"{to=}, but should be a dtype")
+    # Note: We avoid np.can_cast() as it has discrepancies with the array API.
+    # See https://github.com/numpy/numpy/issues/20870
     try:
+        # We promote `from_` and `to` together. We then check if the promoted
+        # dtype is `to`, which indicates if `from_` can (up)cast to `to`.
         dtype = _result_type(from_, to)
         return to == dtype
     except TypeError:
+        # _result_type() raises if the dtypes don't promote together
         return False
 
 

array_api_strict/tests/test_data_type_functions.py

@@ -8,8 +8,6 @@
     [
         (xp.int8, xp.int16, True),
         (xp.int16, xp.int8, False),
-        # np.can_cast has discrepancies with the Array API
-        # See https://github.com/numpy/numpy/issues/20870
         (xp.bool, xp.int8, False),
         (xp.asarray(0, dtype=xp.uint8), xp.int8, False),
     ],