BUG: Fix fill value in masked array '==' and '!=' ops.

The type of the fill_value needs to be `bool_` in order to match
the result type of `==` and `!=`.

Closes #12248.

1 files changed, 18 insertions, 5 deletions

diff --git a/numpy/ma/core.py b/numpy/ma/core.py
index 9259aa4c7..9ee44e9ff 100644
--- a/numpy/ma/core.py
+++ b/numpy/ma/core.py
@@ -446,6 +446,7 @@ def _check_fill_value(fill_value, ndtype):
     If fill_value is not None, its value is forced to the given dtype.
 
     The result is always a 0d array.
+
     """
     ndtype = np.dtype(ndtype)
     fields = ndtype.fields
@@ -465,17 +466,19 @@ def _check_fill_value(fill_value, ndtype):
                                   dtype=ndtype)
     else:
         if isinstance(fill_value, basestring) and (ndtype.char not in 'OSVU'):
+            # Note this check doesn't work if fill_value is not a scalar
             err_msg = "Cannot set fill value of string with array of dtype %s"
             raise TypeError(err_msg % ndtype)
         else:
             # In case we want to convert 1e20 to int.
+            # Also in case of converting string arrays.
             try:
                 fill_value = np.array(fill_value, copy=False, dtype=ndtype)
-            except OverflowError:
-                # Raise TypeError instead of OverflowError. OverflowError
-                # is seldom used, and the real problem here is that the
-                # passed fill_value is not compatible with the ndtype.
-                err_msg = "Fill value %s overflows dtype %s"
+            except (OverflowError, ValueError):
+                # Raise TypeError instead of OverflowError or ValueError.
+                # OverflowError is seldom used, and the real problem here is
+                # that the passed fill_value is not compatible with the ndtype.
+                err_msg = "Cannot convert fill_value %s to dtype %s"
                 raise TypeError(err_msg % (fill_value, ndtype))
     return np.array(fill_value)
 
@@ -4014,6 +4017,16 @@ class MaskedArray(ndarray):
         check = check.view(type(self))
         check._update_from(self)
         check._mask = mask
+
+        # Cast fill value to bool_ if needed. If it cannot be cast, the
+        # default boolean fill value is used.
+        if check._fill_value is not None:
+            try:
+                fill = _check_fill_value(check._fill_value, np.bool_)
+            except (TypeError, ValueError):
+                fill = _check_fill_value(None, np.bool_)
+            check._fill_value = fill
+
         return check
 
     def __eq__(self, other):