Implemented dpnp.can_cast function (#1600)

* Implemented dpnp.can_cast function

* address comments

* Update tests/third_party/cupy/test_type_routines.py

Co-authored-by: Anton <100830759+antonwolfy@users.noreply.github.com>

* Update tests/third_party/cupy/test_type_routines.py

Co-authored-by: Anton <100830759+antonwolfy@users.noreply.github.com>

---------

Co-authored-by: Anton <100830759+antonwolfy@users.noreply.github.com>

dpnp/dpnp_iface_manipulation.py

@@ -56,6 +56,7 @@
     "atleast_3d",
     "broadcast_arrays",
     "broadcast_to",
+    "can_cast",
     "concatenate",
     "copyto",
     "expand_dims",
@@ -402,6 +403,47 @@ def broadcast_to(array, /, shape, subok=False):
     return dpnp_array._create_from_usm_ndarray(new_array)
 
 
+def can_cast(from_, to, casting="safe"):
+    """
+    Returns ``True`` if cast between data types can occur according to the casting rule.
+
+    If `from` is a scalar or array scalar, also returns ``True`` if the scalar value can
+    be cast without overflow or truncation to an integer.
+
+    For full documentation refer to :obj:`numpy.can_cast`.
+
+    Parameters
+    ----------
+    from : dpnp.array, dtype
+        Source data type.
+    to : dtype
+        Target data type.
+    casting : {'no', 'equiv', 'safe', 'same_kind', 'unsafe'}, optional
+        Controls what kind of data casting may occur.
+
+    Returns
+    -------
+    out: bool
+        True if cast can occur according to the casting rule.
+
+    See Also
+    --------
+    :obj:`dpnp.result_type` : Returns the type that results from applying the NumPy
+        type promotion rules to the arguments.
+
+    """
+
+    if dpnp.is_supported_array_type(to):
+        raise TypeError("Cannot construct a dtype from an array")
+
+    dtype_from = (
+        from_.dtype
+        if dpnp.is_supported_array_type(from_)
+        else dpnp.dtype(from_)
+    )
+    return dpt.can_cast(dtype_from, to, casting)
+
+
 def concatenate(
     arrays, /, *, axis=0, out=None, dtype=None, casting="same_kind"
 ):
@@ -519,7 +561,7 @@ def copyto(dst, src, casting="same_kind", where=True):
     elif not dpnp.is_supported_array_type(src):
         src = dpnp.array(src, sycl_queue=dst.sycl_queue)
 
-    if not dpt.can_cast(src.dtype, dst.dtype, casting=casting):
+    if not dpnp.can_cast(src.dtype, dst.dtype, casting=casting):
         raise TypeError(
             f"Cannot cast from {src.dtype} to {dst.dtype} "
             f"according to the rule {casting}."

tests/test_arraymanipulation.py

@@ -928,3 +928,14 @@ def test_subok_error():
     with pytest.raises(NotImplementedError):
         dpnp.broadcast_arrays(x, subok=True)
         dpnp.broadcast_to(x, (4, 4), subok=True)
+
+
+def test_can_cast():
+    X = dpnp.ones((2, 2), dtype=dpnp.int64)
+    pytest.raises(TypeError, dpnp.can_cast, X, 1)
+    pytest.raises(TypeError, dpnp.can_cast, X, X)
+
+    X_np = numpy.ones((2, 2), dtype=numpy.int64)
+    assert dpnp.can_cast(X, "float32") == numpy.can_cast(X_np, "float32")
+    assert dpnp.can_cast(X, dpnp.int32) == numpy.can_cast(X_np, numpy.int32)
+    assert dpnp.can_cast(X, dpnp.int64) == numpy.can_cast(X_np, numpy.int64)

tests/third_party/cupy/test_type_routines.py

@@ -0,0 +1,102 @@
+import unittest
+
+import numpy
+import pytest
+
+import dpnp as cupy
+from tests.third_party.cupy import testing
+
+
+def _generate_type_routines_input(xp, dtype, obj_type):
+    dtype = numpy.dtype(dtype)
+    if obj_type == "dtype":
+        return dtype
+    if obj_type == "specifier":
+        return str(dtype)
+    if obj_type == "scalar":
+        return dtype.type(3)
+    if obj_type == "array":
+        return xp.zeros(3, dtype=dtype)
+    if obj_type == "primitive":
+        return type(dtype.type(3).tolist())
+    assert False
+
+
+@testing.parameterize(
+    *testing.product(
+        {
+            "obj_type": ["dtype", "specifier", "scalar", "array", "primitive"],
+        }
+    )
+)
+class TestCanCast(unittest.TestCase):
+    @testing.for_all_dtypes_combination(names=("from_dtype", "to_dtype"))
+    @testing.numpy_cupy_equal()
+    def test_can_cast(self, xp, from_dtype, to_dtype):
+        if self.obj_type == "scalar":
+            pytest.skip("to be aligned with NEP-50")
+
+        from_obj = _generate_type_routines_input(xp, from_dtype, self.obj_type)
+
+        ret = xp.can_cast(from_obj, to_dtype)
+        assert isinstance(ret, bool)
+        return ret
+
+
+@pytest.mark.skip("dpnp.common_type() is not implemented yet")
+class TestCommonType(unittest.TestCase):
+    @testing.numpy_cupy_equal()
+    def test_common_type_empty(self, xp):
+        ret = xp.common_type()
+        assert type(ret) == type
+        return ret
+
+    @testing.for_all_dtypes(no_bool=True)
+    @testing.numpy_cupy_equal()
+    def test_common_type_single_argument(self, xp, dtype):
+        array = _generate_type_routines_input(xp, dtype, "array")
+        ret = xp.common_type(array)
+        assert type(ret) == type
+        return ret
+
+    @testing.for_all_dtypes_combination(
+        names=("dtype1", "dtype2"), no_bool=True
+    )
+    @testing.numpy_cupy_equal()
+    def test_common_type_two_arguments(self, xp, dtype1, dtype2):
+        array1 = _generate_type_routines_input(xp, dtype1, "array")
+        array2 = _generate_type_routines_input(xp, dtype2, "array")
+        ret = xp.common_type(array1, array2)
+        assert type(ret) == type
+        return ret
+
+    @testing.for_all_dtypes()
+    def test_common_type_bool(self, dtype):
+        for xp in (numpy, cupy):
+            array1 = _generate_type_routines_input(xp, dtype, "array")
+            array2 = _generate_type_routines_input(xp, "bool_", "array")
+            with pytest.raises(TypeError):
+                xp.common_type(array1, array2)
+
+
+@testing.parameterize(
+    *testing.product(
+        {
+            "obj_type1": ["dtype", "specifier", "scalar", "array", "primitive"],
+            "obj_type2": ["dtype", "specifier", "scalar", "array", "primitive"],
+        }
+    )
+)
+class TestResultType(unittest.TestCase):
+    @testing.for_all_dtypes_combination(names=("dtype1", "dtype2"))
+    @testing.numpy_cupy_equal()
+    def test_result_type(self, xp, dtype1, dtype2):
+        if "scalar" in {self.obj_type1, self.obj_type2}:
+            pytest.skip("to be aligned with NEP-50")
+
+        input1 = _generate_type_routines_input(xp, dtype1, self.obj_type1)
+
+        input2 = _generate_type_routines_input(xp, dtype2, self.obj_type2)
+        ret = xp.result_type(input1, input2)
+        assert isinstance(ret, numpy.dtype)
+        return ret