fasta tokens implement analyzer token API

pkg/front_end/test/scanner_replacement_test.dart

 // Copyright (c) 2017, 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:convert' show UTF8;
 
+import 'package:front_end/src/fasta/scanner/abstract_scanner.dart'
+    show fastaSupportsGenericMethodComments;
 import 'package:front_end/src/fasta/scanner/precedence.dart'
     show BAD_INPUT_INFO, EOF_INFO;
 import 'package:front_end/src/fasta/scanner/recover.dart'
     show defaultRecoveryStrategy;
 import 'package:front_end/src/fasta/scanner.dart' as fasta;
 import 'package:front_end/src/fasta/scanner/token.dart' as fasta;
 import 'package:front_end/src/fasta/scanner/error_token.dart' as fasta;
 import 'package:front_end/src/scanner/token.dart' as analyzer;
 import 'package:front_end/src/scanner/errors.dart'
     show ScannerErrorCode, translateErrorToken;
@@ skipping 13 matching lines @@
 /// token stream before verifying assertions.
 ///
 /// These tests help to validate the correctness of the analyzer->Fasta token
 /// stream conversion.
 @reflectiveTest
 class ScannerTest_Replacement extends ScannerTest {
   @override
   analyzer.Token scanWithListener(String source, ErrorListener listener,
       {bool genericMethodComments: false,
       bool lazyAssignmentOperators: false}) {
-    if (genericMethodComments) {
+    if (genericMethodComments && !fastaSupportsGenericMethodComments) {
       // Fasta doesn't support generic method comments.
       // TODO(danrubel): once the analyzer toolchain no longer needs generic
       // method comments, remove tests that exercise them.
       fail('No generic method comment support in Fasta');
     }
     // Note: Fasta always supports lazy assignment operators (`&&=` and `||=`),
     // so we can ignore the `lazyAssignmentOperators` flag.
     // TODO(danrubel): once lazyAssignmentOperators are fully supported by
     // Dart, remove this flag.
     fasta.ScannerResult result = fasta.scanString(source,
@@ skipping 342 matching lines @@
       } else if (token is fasta.UnmatchedToken) {
         expect(lastClosedGroup?.endGroup?.next, same(token),
             reason: 'Unexpected error token for group: $lastClosedGroup');
         expect(token.begin, lastClosedGroup);
       }
       token = token.next;
     }
     expect(openerStack, isEmpty, reason: 'Missing closers');
   }
 }