MAINT,ENH: remove MaskedArray.astype, as the base type does everything.

With a slight update to `__array_finalize__`, this also fixes the
mask ordering to be the same as that of the data.

1 files changed, 24 insertions, 44 deletions

diff --git a/numpy/ma/core.py b/numpy/ma/core.py
index dad675600..1803ae493 100644
--- a/numpy/ma/core.py
+++ b/numpy/ma/core.py
@@ -1624,7 +1624,7 @@ def make_mask(m, copy=False, shrink=True, dtype=MaskType):
 
     # Make sure the input dtype is valid.
     dtype = make_mask_descr(dtype)
-    
+
     # legacy boolean special case: "existence of fields implies true"
     if isinstance(m, ndarray) and m.dtype.fields and dtype == np.bool_:
         return np.ones(m.shape, dtype=dtype)
@@ -2978,11 +2978,30 @@ class MaskedArray(ndarray):
             # heuristic it's not bad.) In all other cases, we make a copy of
             # the mask, so that future modifications to 'self' do not end up
             # side-effecting 'obj' as well.
-            if (obj.__array_interface__["data"][0]
+            if (_mask is not nomask and obj.__array_interface__["data"][0]
                     != self.__array_interface__["data"][0]):
-                _mask = _mask.copy()
+                # We should make a copy. But we could get here via astype,
+                # in which case the mask might need a new dtype as well
+                # (e.g., changing to or from a structured dtype), and the
+                # order could have changed. So, change the mask type if
+                # needed and use astype instead of copy.
+                if self.dtype == obj.dtype:
+                    _mask_dtype = _mask.dtype
+                else:
+                    _mask_dtype = make_mask_descr(self.dtype)
+
+                if self.flags.c_contiguous:
+                    order = "C"
+                elif self.flags.f_contiguous:
+                    order = "F"
+                else:
+                    order = "K"
+
+                _mask = _mask.astype(_mask_dtype, order)
+
         else:
             _mask = nomask
+
         self._mask = _mask
         # Finalize the mask
         if self._mask is not nomask:
@@ -3140,45 +3159,6 @@ class MaskedArray(ndarray):
         return output
     view.__doc__ = ndarray.view.__doc__
 
-    def astype(self, newtype):
-        """
-        Returns a copy of the MaskedArray cast to given newtype.
-
-        Returns
-        -------
-        output : MaskedArray
-            A copy of self cast to input newtype.
-            The returned record shape matches self.shape.
-
-        Examples
-        --------
-        >>> x = np.ma.array([[1,2,3.1],[4,5,6],[7,8,9]], mask=[0] + [1,0]*4)
-        >>> print(x)
-        [[1.0 -- 3.1]
-         [-- 5.0 --]
-         [7.0 -- 9.0]]
-        >>> print(x.astype(int32))
-        [[1 -- 3]
-         [-- 5 --]
-         [7 -- 9]]
-
-        """
-        newtype = np.dtype(newtype)
-        newmasktype = make_mask_descr(newtype)
-
-        output = self._data.astype(newtype).view(type(self))
-        output._update_from(self)
-
-        if self._mask is nomask:
-            output._mask = nomask
-        else:
-            output._mask = self._mask.astype(newmasktype)
-
-        # Don't check _fill_value if it's None, that'll speed things up
-        if self._fill_value is not None:
-            output._fill_value = _check_fill_value(self._fill_value, newtype)
-        return output
-
     def __getitem__(self, indx):
         """
         x.__getitem__(y) <==> x[y]
@@ -4303,7 +4283,7 @@ class MaskedArray(ndarray):
         elif self._mask:
             raise MaskError('Cannot convert masked element to a Python int.')
         return int(self.item())
-    
+
     def __long__(self):
         """
         Convert to long.
@@ -4314,7 +4294,7 @@ class MaskedArray(ndarray):
         elif self._mask:
             raise MaskError('Cannot convert masked element to a Python long.')
         return long(self.item())
-      
+
 
     def get_imag(self):
         """