fix completion replacement offset/length for invalid token in switch statement

pkg/analysis_server/test/services/completion/keyword_contributor_test.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 test.services.completion.dart.keyword;
 
 import 'package:analysis_server/src/protocol.dart';
 import 'package:analysis_server/src/services/completion/dart_completion_manager.dart';
 import 'package:analysis_server/src/services/completion/keyword_contributor.dart';
 import 'package:analyzer/src/generated/scanner.dart';
@@ skipping 1110 matching lines @@
         relevance: DART_RELEVANCE_HIGH);
   }
 
   test_switch_start4() {
     addTestSource('main() {switch(1) {^ default:}}');
     expect(computeFast(), isTrue);
     assertSuggestKeywords([Keyword.CASE, Keyword.DEFAULT],
         relevance: DART_RELEVANCE_HIGH);
   }
 
+  test_switch_start5() {
+    addTestSource('main() {switch(1) {c^ default:}}');
+    expect(computeFast(), isTrue);
+    assertSuggestKeywords([Keyword.CASE, Keyword.DEFAULT],
+        relevance: DART_RELEVANCE_HIGH);
+    expect(request.replacementOffset, 19);
+    expect(request.replacementLength, 1);
+  }
+
+  test_switch_start6() {
+    addTestSource('main() {switch(1) {c^}}');
+    expect(computeFast(), isTrue);
+    assertSuggestKeywords([Keyword.CASE, Keyword.DEFAULT],
+        relevance: DART_RELEVANCE_HIGH);
+    expect(request.replacementOffset, 19);
+    expect(request.replacementLength, 1);
+  }
+
+  test_switch_start7() {
+    addTestSource('main() {switch(1) { c^ }}');
+    expect(computeFast(), isTrue);
+    assertSuggestKeywords([Keyword.CASE, Keyword.DEFAULT],
+        relevance: DART_RELEVANCE_HIGH);
+    expect(request.replacementOffset, 20);
+    expect(request.replacementLength, 1);
+  }
+
   test_switch_statement() {
     addTestSource('main() {switch(1) {case 1:^}}');
     expect(computeFast(), isTrue);
     assertSuggestKeywords(STMT_START_IN_SWITCH_OUTSIDE_CLASS);
   }
 
   test_switch_statement2() {
     addTestSource('class A{foo() {switch(1) {case 1:^}}}');
     expect(computeFast(), isTrue);
     assertSuggestKeywords(STMT_START_IN_SWITCH_IN_CLASS);
   }
 
   void _appendCompletions(
       StringBuffer msg, Iterable<String> completions, Iterable<String> other) {
     List<String> sorted = completions.toList();
     sorted.sort((c1, c2) => c1.compareTo(c2));
     sorted.forEach(
         (c) => msg.writeln('  $c, ${other.contains(c) ? '' : '<<<<<<<<<<<'}'));
   }
 
   bool _equalSets(Iterable<String> iter1, Iterable<String> iter2) {
     if (iter1.length != iter2.length) return false;
     if (iter1.any((c) => !iter2.contains(c))) return false;
     if (iter2.any((c) => !iter1.contains(c))) return false;
     return true;
   }
 }