Merge pull request #26 from ryneeverett/unused-reassigned-variable

Add tests to document hard to test cases

It would be nice if shadowing an unused variable was an error, but this
is quite difficult to implement in a way which does not also raise false
positives in the context of loops.

2 files changed, 25 insertions, 0 deletions

diff --git a/pyflakes/checker.py b/pyflakes/checker.py
index fcdce9c..abd7f50 100644
--- a/pyflakes/checker.py
+++ b/pyflakes/checker.py
@@ -527,6 +527,7 @@ class Checker(object):
         else:
             binding = Assignment(name, node)
         if name in self.scope:
+            # then assume the rebound name is used as a global or within a loop
             binding.used = self.scope[name].used
         self.addBinding(node, binding)
 
diff --git a/pyflakes/test/test_other.py b/pyflakes/test/test_other.py
index ac116c8..718d16f 100644
--- a/pyflakes/test/test_other.py
+++ b/pyflakes/test/test_other.py
@@ -523,6 +523,30 @@ class TestUnusedAssignment(TestCase):
                 return
         ''', m.UnusedVariable)
 
+    @skip("todo: Difficult because it does't apply in the context of a loop")
+    def test_unusedReassignedVariable(self):
+        """
+        Shadowing a used variable can still raise an UnusedVariable warning.
+        """
+        self.flakes('''
+        def a():
+            b = 1
+            b.foo()
+            b = 2
+        ''', m.UnusedVariable)
+
+    def test_variableUsedInLoop(self):
+        """
+        Shadowing a used variable cannot raise an UnusedVariable warning in the
+        context of a loop.
+        """
+        self.flakes('''
+        def a():
+            b = True
+            while b:
+                b = False
+        ''')
+
     def test_assignToGlobal(self):
         """
         Assigning to a global and then not using that global is perfectly