Lint to prefer x.isNotEmpty vs. !x.isEmpty (#143).

lib/src/linter.dart

 // Copyright (c) 2015, 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.
 
 library linter.src.linter;
 
 import 'dart:io';
 
 import 'package:analyzer/analyzer.dart';
 import 'package:analyzer/src/generated/engine.dart'
@@ skipping 80 matching lines @@
           // processing gets pushed down, this hack can go away.)
           if (rule.reporter == null && sourceUrl != null) {
             var source = createSource(sourceUrl);
             rule.reporter = new ErrorReporter(this, source);
           }
           try {
             spec.accept(visitor);
           } on Exception catch (e) {
             reporter.exception(new LinterException(e.toString()));
           }
-          if (rule._locationInfo != null && !rule._locationInfo.isEmpty) {
+          if (rule._locationInfo != null && rule._locationInfo.isNotEmpty) {
             results.addAll(rule._locationInfo);
             rule._locationInfo.clear();
           }
         }
       }
     }
 
     return results;
   }
 
@@ skipping 280 matching lines @@
           // processing gets pushed down, this hack can go away.)
           if (rule.reporter == null && sourceUrl != null) {
             var source = createSource(sourceUrl);
             rule.reporter = new ErrorReporter(this, source);
           }
           try {
             spec.accept(visitor);
           } on Exception catch (e) {
             reporter.exception(new LinterException(e.toString()));
           }
-          if (rule._locationInfo != null && !rule._locationInfo.isEmpty) {
+          if (rule._locationInfo != null && rule._locationInfo.isNotEmpty) {
             results.addAll(rule._locationInfo);
             rule._locationInfo.clear();
           }
         }
       }
     }
 
     return results;
   }
 
@@ skipping 15 matching lines @@
 }
 
 class _LintCode extends LintCode {
   static final registry = <String, LintCode>{};
 
   factory _LintCode(String name, String message) => registry.putIfAbsent(
       name + message, () => new _LintCode._(name, message));
 
   _LintCode._(String name, String message) : super(name, message);
 }