Fix hints

pkg/analysis_server/lib/src/computer/computer_outline.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.
 
 library computer.outline;
 
 import 'package:analysis_server/src/collections.dart';
 import 'package:analysis_server/src/protocol.dart';
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/element.dart' as engine;
@@ skipping 120 matching lines @@
         node = parent.parent;
         parent = node.parent;
       } else if (variableIndex >= 1) {
         firstOffset = variables[variableIndex - 1].end;
         return new _SourceRegion(firstOffset, endOffset - firstOffset);
       }
     }
     // unit or class member
     if (parent is CompilationUnit) {
       firstOffset = 0;
-      siblings = (parent as CompilationUnit).declarations;
+      siblings = parent.declarations;
     } else if (parent is ClassDeclaration) {
-      ClassDeclaration classDeclaration = parent as ClassDeclaration;
-      firstOffset = classDeclaration.leftBracket.end;
-      siblings = classDeclaration.members;
+      firstOffset = parent.leftBracket.end;
+      siblings = parent.members;
     } else {
       int offset = node.offset;
       return new _SourceRegion(offset, endOffset - offset);
     }
     // first child: [endOfParent, endOfNode]
     int index = siblings.indexOf(node);
     if (index == 0) {
       return new _SourceRegion(firstOffset, endOffset - firstOffset);
     }
     // not first child: [endOfPreviousSibling, endOfNode]
@@ skipping 220 matching lines @@
 }
 
 /**
  * A range of characters.
  */
 class _SourceRegion {
   final int length;
   final int offset;
   _SourceRegion(this.offset, this.length);
 }