fix analysis messages

tool/patch_sdk.dart

 #!/usr/bin/env 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.
 
 /// Command line tool to merge the SDK libraries and our patch files.
 /// This is currently designed as an offline tool, but we could automate it.
 library ddc.tool.patch_sdk;
 
 import 'dart:io';
@@ skipping 90 matching lines @@
 /// writing the dart:* libraries, and not a tool given to Dart developers, it
 /// seems like a non-ideal situation. Instead we keep the preprocessing simple.
 List<String> _patchLibrary(List<String> partsContents, String patchContents) {
   var results = <StringEditBuffer>[];
 
   // Parse the patch first. We'll need to extract bits of this as we go through
   // the other files.
   var patchFinder = new PatchFinder.parseAndVisit(patchContents);
 
   // Merge `external` declarations with the corresponding `@patch` code.
-  bool first = true;
   for (var partContent in partsContents) {
     var partEdits = new StringEditBuffer(partContent);
     var partUnit = parseCompilationUnit(partContent);
     partUnit.accept(new PatchApplier(partEdits, patchFinder));
     results.add(partEdits);
   }
   return new List<String>.from(results.map((e) => e.toString()));
 }
 
 /// Merge `@patch` declarations into `external` declarations.
 class PatchApplier extends GeneralizingAstVisitor {
   final StringEditBuffer edits;
   final PatchFinder patch;
 
   bool _isLibrary = true; // until proven otherwise.
 
   PatchApplier(this.edits, this.patch);
 
   @override visitCompilationUnit(CompilationUnit node) {
     super.visitCompilationUnit(node);
     if (_isLibrary) _mergeUnpatched(node);
   }
 
   /// Merges directives and declarations that are not `@patch` into the library.
   void _mergeUnpatched(CompilationUnit unit) {
     // Merge directives from the patch
     // TODO(jmesserly): remove duplicate imports
     var directivePos = unit.directives.last.end;
     for (var directive in patch.unit.directives) {
-      var uri = directive.uri.stringValue;
       var code = patch.contents.substring(directive.offset, directive.end);
       edits.insert(directivePos, '\n' + code);
     }
 
     // Merge declarations from the patch
     var declarationPos = edits.original.length;
     for (var declaration in patch.mergeDeclarations) {
       var code = patch.contents.substring(declaration.offset, declaration.end);
       edits.insert(declarationPos, '\n' + code);
     }
@@ skipping 194 matching lines @@
   int get length => end - begin;
 
   String toString() => '(Edit @ $begin,$end: "$replace")';
 
   int compareTo(_StringEdit other) {
     int diff = begin - other.begin;
     if (diff != 0) return diff;
     return end - other.end;
   }
 }