Moved

pandas/core/arrays/base.py

@@ -143,8 +143,6 @@ def nbytes(self):
     def astype(self, dtype, copy=True):
         """Cast to a NumPy array with 'dtype'.
 
-        The default implementation only allows casting to 'object' dtype.
-
         Parameters
         ----------
         dtype : str or dtype
@@ -159,14 +157,7 @@ def astype(self, dtype, copy=True):
         array : ndarray
             NumPy ndarray with 'dtype' for its dtype.
         """
-        np_dtype = np.dtype(dtype)
-
-        if np_dtype != 'object':
-            msg = ("{} can only be coerced to 'object' dtype, "
-                   "not '{}'.").format(type(self).__name__, dtype)
-            raise ValueError(msg)
-
-        return np.array(self, dtype=np_dtype, copy=copy)
+        return np.array(self, dtype=dtype, copy=copy)
 
     def isna(self):
         # type: () -> np.ndarray

pandas/tests/extension_arrays/test_common.py → pandas/tests/extension/test_common.py

@@ -12,6 +12,10 @@ def __init__(self, data):
     def __array__(self, dtype):
         return self.data
 
+    @property
+    def dtype(self):
+        return self.data.dtype
+
 
 def test_astype():
     arr = DummyArray(np.array([1, 2, 3]))
@@ -24,13 +28,11 @@ def test_astype():
     tm.assert_numpy_array_equal(result, expected)
 
 
-def test_astype_raises():
-    arr = DummyArray(np.array([1, 2, 3]))
+def test_astype_no_copy():
+    arr = DummyArray(np.array([1, 2, 3], dtype=np.int64))
+    result = arr.astype(arr.dtype, copy=False)
 
-    # type  int for py2
-    # class int for py3
-    xpr = ("DummyArray can only be coerced to 'object' dtype, not "
-           "'<.* 'int'>'")
+    assert arr.data is result
 
-    with tm.assert_raises_regex(ValueError, xpr):
-        arr.astype(int)
+    result = arr.astype(arr.dtype)
+    assert arr.data is not result