Fix tests

lib/src/codegen/assignments_index.dart

 // Copyright (c) 2015, 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 'package:analyzer/dart/ast/token.dart';
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/element.dart';
-import 'package:analyzer/src/generated/scanner.dart';
 
 import 'ast_builder.dart';
 
 /// Creates an index of variable assignments and declarations occurring in all
 /// the provided [nodes].
 ///
 /// Expands any compound assignment expression (e.g. `i += 2` yields an assigned
 /// expression of `i + 2`), and treats declarations with no assignment as having
 /// a `null` assigned expression.
 Map<LocalVariableElement, List<Expression>> indexLocalAssignments(
@@ skipping 118 matching lines @@
 
 Token _opToken(TokenType t) => new Token(t, 0);
 
 /// Transforms `+=` to `+`, `??=` to `??`, etc.
 TokenType _expandAssignmentOp(TokenType assignmentOp) {
   assert(assignmentOp.isAssignmentOperator);
   var op = _opByAssignmentOp[assignmentOp];
   if (op == null) throw new ArgumentError("Can't expand op $assignmentOp");
   return op;
 }