Port and test more assists.

pkg/analysis_services/lib/src/correction/source_range.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.
 
 // This code was auto-generated, is not intended to be edited, and is subject to
 // significant change. Please see the README file for more information.
 
 library services.src.correction.source_range_factory;
 
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/element.dart';
 import 'package:analyzer/src/generated/error.dart';
 import 'package:analyzer/src/generated/scanner.dart';
 import 'package:analyzer/src/generated/source.dart';
 
 
 SourceRange rangeElementName(Element element) {
   return new SourceRange(element.nameOffset, element.name.length);
 }
 
 SourceRange rangeEndEnd(a, b) {
   int offset = a.end;
   var length = b.end - offset;
   return new SourceRange(offset, length);
 }
 
+SourceRange rangeEndLength(a, int length) {
+  int offset = a is int ? a : a.end;
+  return new SourceRange(offset, length);
+}
+
 SourceRange rangeEndStart(a, b) {
   int offset = a.end;
-  var length = b.offset - offset;
+  var length = (b is int ? b : b.offset) - offset;
   return new SourceRange(offset, length);
 }
 
 SourceRange rangeError(AnalysisError error) {
   return new SourceRange(error.offset, error.length);
 }
 
 SourceRange rangeNode(AstNode node) {
   return new SourceRange(node.offset, node.length);
 }
@@ skipping 27 matching lines @@
 
 SourceRange rangeStartStart(a, b) {
   int offset = a is int ? a : a.offset;
   var length = (b is int ? b : b.offset) - offset;
   return new SourceRange(offset, length);
 }
 
 SourceRange rangeToken(Token token) {
   return new SourceRange(token.offset, token.length);
 }