Restore partial analysis of analysis options files

pkg/analysis_server/lib/src/domain_completion.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.
 
 import 'dart:async';
 
 import 'package:analysis_server/protocol/protocol.dart';
 import 'package:analysis_server/protocol/protocol_generated.dart';
 import 'package:analysis_server/src/analysis_server.dart';
 import 'package:analysis_server/src/collections.dart';
@@ skipping 178 matching lines @@
             request, this, params, performance, completionId);
         return;
       }
       source = server.resourceProvider.getFile(filePath).createSource();
     } else {
       if (offset < 0 || offset > result.content.length) {
         server.sendResponse(new Response.invalidParameter(
             request,
             'params.offset',
             'Expected offset between 0 and source length inclusive,'
-            ' but found ${offset}'));
+            ' but found $offset'));
         return;
       }
       source =
           server.resourceProvider.getFile(result.path).createSource(result.uri);
 
       recordRequest(performance, source, result.content, offset);
     }
     CompletionRequestImpl completionRequest = new CompletionRequestImpl(
         result, server.resourceProvider, source, offset, performance);
 
@@ skipping 83 matching lines @@
   final int replacementOffset;
 
   /**
    * The suggested completions.
    */
   final List<CompletionSuggestion> suggestions;
 
   CompletionResult(
       this.replacementOffset, this.replacementLength, this.suggestions);
 }