BUG: loosen kwargs requirements in ediff1d

2 files changed, 16 insertions, 18 deletions

diff --git a/numpy/lib/arraysetops.py b/numpy/lib/arraysetops.py
index 558150e48..b53d8c03f 100644
--- a/numpy/lib/arraysetops.py
+++ b/numpy/lib/arraysetops.py
@@ -94,8 +94,7 @@ def ediff1d(ary, to_end=None, to_begin=None):
     # force a 1d array
     ary = np.asanyarray(ary).ravel()
 
-    # we have unit tests enforcing
-    # propagation of the dtype of input
+    # enforce propagation of the dtype of input
     # ary to returned result
     dtype_req = ary.dtype
 
@@ -106,23 +105,22 @@ def ediff1d(ary, to_end=None, to_begin=None):
     if to_begin is None:
         l_begin = 0
     else:
-        to_begin = np.asanyarray(to_begin)
-        if not np.can_cast(to_begin, dtype_req):
-            raise TypeError("dtype of to_begin must be compatible "
-                            "with input ary")
-
-        to_begin = to_begin.ravel()
+        _to_begin = np.asanyarray(to_begin, dtype=dtype_req)
+        if not np.all(_to_begin == to_begin):
+            raise ValueError("cannot convert 'to_begin' to array with dtype "
+                            "'%r' as required for input ary" % dtype_req)
+        to_begin = _to_begin.ravel()
         l_begin = len(to_begin)
 
     if to_end is None:
         l_end = 0
     else:
-        to_end = np.asanyarray(to_end)
-        if not np.can_cast(to_end, dtype_req):
-            raise TypeError("dtype of to_end must be compatible "
-                            "with input ary")
-
-        to_end = to_end.ravel()
+        _to_end = np.asanyarray(to_end, dtype=dtype_req)
+        # check that casting has not overflowed
+        if not np.all(_to_end == to_end):
+            raise ValueError("cannot convert 'to_end' to array with dtype "
+                             "'%r' as required for input ary" % dtype_req)
+        to_end = _to_end.ravel()
         l_end = len(to_end)
 
     # do the calculation in place and copy to_begin and to_end
diff --git a/numpy/lib/tests/test_arraysetops.py b/numpy/lib/tests/test_arraysetops.py
index a17fc66e5..93d4b279f 100644
--- a/numpy/lib/tests/test_arraysetops.py
+++ b/numpy/lib/tests/test_arraysetops.py
@@ -136,8 +136,8 @@ class TestSetOps(object):
          np.nan),
         # should fail because attempting
         # to downcast to smaller int type:
-        (np.array([1, 2, 3], dtype=np.int32),
-         np.array([5, 7, 2], dtype=np.int64),
+        (np.array([1, 2, 3], dtype=np.int16),
+         np.array([5, 1<<20, 2], dtype=np.int32),
          None),
         # should fail because attempting to cast
         # two special floating point values
@@ -152,8 +152,8 @@ class TestSetOps(object):
         # specifically, raise an appropriate
         # Exception when attempting to append or
         # prepend with an incompatible type
-        msg = 'must be compatible'
-        with assert_raises_regex(TypeError, msg):
+        msg = 'cannot convert'
+        with assert_raises_regex(ValueError, msg):
             ediff1d(ary=ary,
                     to_end=append,
                     to_begin=prepend)