smoke: remove unused variables and imports, added an explicit null return

lib/static.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /// Static implementation of smoke services using code-generated data.
 library smoke.static;
 
 import 'dart:math' as math;
 
-import 'package:logging/logging.dart';
 import 'package:smoke/smoke.dart';
 
 import 'src/common.dart';
 
 typedef T Getter<T>(object);
 typedef void Setter<T>(object, value);
 
 class StaticConfiguration {
   /// Maps symbol to a function that reads that symbol of an object. For
   /// instance, `#i: (o) => o.i`.
@@ skipping 262 matching lines @@
 
 /// Exception thrown when trynig to access something that should be there, but
 /// the code generator didn't include it.
 class MissingCodeException implements Exception {
   final String description;
   MissingCodeException(this.description);
 
   String toString() => 'Missing $description. '
       'Code generation for the smoke package seems incomplete.';
 }