Check feature names imported from future

As '*' does not appear in __future__.all_feature_names, this
also reports an error on : from __future__ import *

Author: jayvdb

pyflakes/checker.py

@@ -4,6 +4,7 @@
 Implement the central Checker class.
 Also, it models the Bindings and Scopes.
 """
+import __future__
 import doctest
 import os
 import sys
@@ -1053,6 +1054,9 @@ def IMPORTFROM(self, node):
             name = alias.asname or alias.name
             if node.module == '__future__':
                 importation = FutureImportation(name, node, self.scope)
+                if alias.name not in __future__.all_feature_names:
+                    self.report(messages.FutureFeatureNotDefined,
+                                node, alias.name)
             elif alias.name == '*':
                 # Only Python 2, local import * is a SyntaxWarning
                 if not PY2 and not isinstance(self.scope, ModuleScope):

pyflakes/messages.py

@@ -124,6 +124,15 @@ def __init__(self, filename, loc, names):
         self.message_args = ()
 
 
+class FutureFeatureNotDefined(Message):
+    """An undefined __future__ feature name was imported."""
+    message = 'future feature %s is not defined'
+
+    def __init__(self, filename, loc, name):
+        Message.__init__(self, filename, loc)
+        self.message_args = (name,)
+
+
 class UnusedVariable(Message):
     """
     Indicates that a variable has been explicitly assigned to but not actually

pyflakes/test/test_imports.py

@@ -788,6 +788,18 @@ def test_futureImportUsed(self):
         assert print_function is not division
         ''')
 
+    def test_futureImportUndefined(self):
+        """Importing undefined names from __future__ fails."""
+        self.flakes('''
+        from __future__ import print_statement
+        ''', m.FutureFeatureNotDefined)
+
+    def test_futureImportStar(self):
+        """Importing '*' from __future__ fails."""
+        self.flakes('''
+        from __future__ import *
+        ''', m.FutureFeatureNotDefined)
+
 
 class TestSpecialAll(TestCase):
     """