report invalid param if offset is out of bounds

pkg/analysis_server/lib/src/services/completion/dart_completion_manager.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 services.completion.dart;
 
 import 'dart:async';
 
 import 'package:analysis_server/plugin/protocol/protocol.dart';
 import 'package:analysis_server/src/provisional/completion/completion_core.dart'
@@ skipping 114 matching lines @@
    * Compute suggestions based upon cached information only
    * then send an initial response to the client.
    * Return a list of contributors for which [computeFull] should be called
    */
   List<DartCompletionContributor> computeFast(
       DartCompletionRequest request, CompletionPerformance performance) {
     return performance.logElapseTime('computeFast', () {
       CompilationUnit unit = context.parseCompilationUnit(source);
       request.unit = unit;
       request.target = new CompletionTarget.forOffset(unit, request.offset);
-      if (request.offset < 0 || request.offset > unit.end) {
-        request.replacementOffset = request.offset;
-        request.replacementLength = 0;
-        sendResults(request, true);
-        return [];
-      }
 
       ReplacementRange range =
           new ReplacementRange.compute(request.offset, request.target);
       request.replacementOffset = range.offset;
       request.replacementLength = range.length;
 
       List<DartCompletionContributor> todo = new List.from(contributors);
       todo.removeWhere((DartCompletionContributor c) {
         return performance.logElapseTime('computeFast ${c.runtimeType}', () {
           return c.computeFast(request);
@@ skipping 307 matching lines @@
               // Replacement range for import URI
               return new ReplacementRange(start, end - start);
             }
           }
         }
       }
     }
     return new ReplacementRange(requestOffset, 0);
   }
 }