Make imag and real attributes numpy.ndarray

Close pylint-dev/pylint#3322

ChangeLog

@@ -7,6 +7,10 @@ What's New in astroid 2.4.0?
 Release Date: TBA
 
 
+* Numpy ``ndarray`` attributes ``imag`` and ``real`` are now inferred as ``ndarray``.
+
+  Close PyCQA/pylint#3322
+
 * Added a call to ``register_transform`` for all functions of the ``brain_numpy_core_multiarray``
   module in case the current node is an instance of ``astroid.Name``
 

astroid/brain/brain_numpy_ndarray.py

@@ -24,11 +24,11 @@ def __init__(self, shape, dtype=float, buffer=None, offset=0,
             self.dtype = None
             self.flags = None
             self.flat = None
-            self.imag = None
+            self.imag = np.ndarray([0, 0])
             self.itemsize = None
             self.nbytes = None
             self.ndim = None
-            self.real = None
+            self.real = np.ndarray([0, 0])
             self.shape = numpy.ndarray([0, 0])
             self.size = None
             self.strides = None

tests/unittest_brain_numpy_ndarray.py

@@ -117,6 +117,18 @@ def _inferred_ndarray_method_call(self, func_name):
         )
         return node.infer()
 
+    def _inferred_ndarray_attribute(self, attr_name):
+        node = builder.extract_node(
+            """
+        import numpy as np
+        test_array = np.ndarray((2, 2))
+        test_array.{:s}
+        """.format(
+                attr_name
+            )
+        )
+        return node.infer()
+
     def test_numpy_function_calls_inferred_as_ndarray(self):
         """
         Test that some calls to numpy functions are inferred as numpy.ndarray
@@ -136,6 +148,25 @@ def test_numpy_function_calls_inferred_as_ndarray(self):
                     ),
                 )
 
+    def test_numpy_ndarray_attribute_inferred_as_ndarray(self):
+        """
+        Test that some numpy ndarray attributes are inferred as numpy.ndarray
+        """
+        licit_array_types = ".ndarray"
+        for attr_ in ("real", "imag"):
+            with self.subTest(typ=attr_):
+                inferred_values = list(self._inferred_ndarray_attribute(attr_))
+                self.assertTrue(
+                    len(inferred_values) == 1,
+                    msg="Too much inferred value for {:s}".format(attr_),
+                )
+                self.assertTrue(
+                    inferred_values[-1].pytype() in licit_array_types,
+                    msg="Illicit type for {:s} ({})".format(
+                        attr_, inferred_values[-1].pytype()
+                    ),
+                )
+
 
 if __name__ == "__main__":
     unittest.main()