BUG: Don't allow an array to be passed as the dtype argument

2 files changed, 8 insertions, 3 deletions

diff --git a/numpy/lib/tests/test_type_check.py b/numpy/lib/tests/test_type_check.py
index d863e5924..1b1af86da 100644
--- a/numpy/lib/tests/test_type_check.py
+++ b/numpy/lib/tests/test_type_check.py
@@ -3,7 +3,7 @@ from __future__ import division, absolute_import, print_function
 import numpy as np
 from numpy.compat import long
 from numpy.testing import (
-    assert_, assert_equal, assert_array_equal, run_module_suite
+    assert_, assert_equal, assert_array_equal, run_module_suite, assert_raises
     )
 from numpy.lib.type_check import (
     common_type, mintypecode, isreal, iscomplex, isposinf, isneginf,
@@ -422,5 +422,11 @@ class TestArrayConversion(object):
         assert_equal(a.__class__, np.ndarray)
         assert_(np.issubdtype(a.dtype, float))
 
+        # previously this would infer dtypes from arrays, unlike every single
+        # other numpy function
+        assert_raises(TypeError,
+            asfarray, np.array([1, 2, 3]), dtype=np.array(1.0))
+
+
 if __name__ == "__main__":
     run_module_suite()
diff --git a/numpy/lib/type_check.py b/numpy/lib/type_check.py
index b2de153d3..e6aae8ddd 100644
--- a/numpy/lib/type_check.py
+++ b/numpy/lib/type_check.py
@@ -98,8 +98,7 @@ def asfarray(a, dtype=_nx.float_):
     array([ 2.,  3.])
 
     """
-    dtype = _nx.obj2sctype(dtype)
-    if not issubclass(dtype, _nx.inexact):
+    if not _nx.issubdtype(dtype, _nx.inexact):
         dtype = _nx.float_
     return asarray(a, dtype=dtype)