Mark bindings as used by locals()

Fixes #136
Fixes #333

Author: jayvdb

Diff for: pyflakes/checker.py

@@ -409,7 +409,6 @@ class FunctionScope(Scope):
 
     @ivar globals: Names declared 'global' in this function.
     """
-    usesLocals = False
     alwaysUsed = {'__tracebackhide__', '__traceback_info__',
                   '__traceback_supplement__'}
 
@@ -428,7 +427,6 @@ def unusedAssignments(self):
             if (not binding.used
                     and name != '_'  # see issue #202
                     and name not in self.globals
-                    and not self.usesLocals
                     and isinstance(binding, Assignment)):
                 yield name, binding
 
@@ -710,6 +708,15 @@ def handleNodeLoad(self, node):
         in_generators = None
         importStarred = None
 
+        if node.id == 'locals' and isinstance(node.parent, ast.Call):
+            # we are doing locals() call, which marks names currently
+            # in scope as used.
+            scope = self.scope
+            if isinstance(scope, GeneratorScope):
+                scope = self.scopeStack[-2]
+            for binding in scope.values():
+                binding.used = (self.scope, node)
+
         # try enclosing function scopes and global scope
         for scope in self.scopeStack[-1::-1]:
             if isinstance(scope, ClassScope):
@@ -1096,10 +1103,6 @@ def NAME(self, node):
         # Locate the name in locals / function / globals scopes.
         if isinstance(node.ctx, (ast.Load, ast.AugLoad)):
             self.handleNodeLoad(node)
-            if (node.id == 'locals' and isinstance(self.scope, FunctionScope)
-                    and isinstance(node.parent, ast.Call)):
-                # we are doing locals() call in current scope
-                self.scope.usesLocals = True
         elif isinstance(node.ctx, (ast.Store, ast.AugStore)):
             self.handleNodeStore(node)
         elif isinstance(node.ctx, ast.Del):

Diff for: pyflakes/test/test_other.py

@@ -1185,7 +1185,7 @@ def a(unused_param):
             _ = unused_param
         ''')
 
-    def test_unusedVariableAsLocals(self):
+    def test_unusedVariableWithLocals(self):
         """
         Using locals() it is perfectly valid to have unused variables
         """
@@ -1195,6 +1195,29 @@ def a():
             return locals()
         ''')
 
+    def test_unusedVariableWithLocalsInComprehension(self):
+        """
+        Using locals() in comprehension it is perfectly valid
+        to have unused variables
+        """
+        self.flakes('''
+        def a():
+            b = 1
+            return (i for i in locals())
+        ''')
+
+    def test_unusedVariableAfterLocals(self):
+        """
+        Warn when an unused variable appears after locals()
+        """
+        self.flakes('''
+        def a():
+            b = 1
+            c = locals()
+            d = 1
+            return c
+        ''', m.UnusedVariable)
+
     def test_unusedVariableNoLocals(self):
         """
         Using locals() in wrong scope should not matter