When translating analyzer/fasta token streams, match up begin/end tokens.

pkg/front_end/test/scanner_fasta_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 'package:front_end/src/fasta/analyzer/token_utils.dart';
 import 'package:front_end/src/fasta/scanner/error_token.dart' as fasta;
 import 'package:front_end/src/fasta/scanner/keyword.dart' as fasta;
 import 'package:front_end/src/fasta/scanner/string_scanner.dart' as fasta;
 import 'package:front_end/src/fasta/scanner/token.dart' as fasta;
 import 'package:front_end/src/fasta/scanner/token_constants.dart' as fasta;
@@ skipping 73 matching lines @@
   @override
   @failingTest
   void test_index_eq() {
     // TODO(paulberry,ahe): "[]=" should be parsed as a single token.
     // See dartbug.com/28665.
     super.test_index_eq();
   }
 
   @override
   @failingTest
+  void test_mismatched_closer() {
+    // TODO(paulberry,ahe): Fasta and analyzer recover this error differently.
+    // Figure out which recovery technique we want the front end to use.

[Paul Berry, 2017/02/13 22:38:59]

FWIW, my intuition is that Fasta's error recovery is better here, because when a
user is typing in a file, they are likely to type openers first and then close
them, so when there is a mismatch between an opener and a closer, it's probably
better to drop the opener.

[ahe, 2017/02/14 11:28:32]

That also has its downsides, but I have some ideas I want to try out in
pkg/front_end/lib/src/fasta/scanner/recover.dart in the future. I don't know
exactly when I'll find time to experiment with this, but feel free to ask me
more about it at any time.

+    super.test_mismatched_closer();
+  }
+
+  @override
+  @failingTest
+  void test_mismatched_opener() {
+    // TODO(paulberry,ahe): Fasta and analyzer recover this error differently.
+    // Figure out which recovery technique we want the front end to use.
+    super.test_mismatched_opener();
+  }
+
+  @override
+  @failingTest
   void test_scriptTag_withArgs() {
     // TODO(paulberry,ahe): script tags are needed by analyzer.
     super.test_scriptTag_withArgs();
   }
 
   @override
   @failingTest
   void test_scriptTag_withoutSpace() {
     // TODO(paulberry,ahe): script tags are needed by analyzer.
     super.test_scriptTag_withoutSpace();
@@ skipping 69 matching lines @@
     super.test_string_simple_unterminated_interpolation_block();
   }
 
   @override
   @failingTest
   void test_string_simple_unterminated_interpolation_identifier() {
     // TODO(paulberry,ahe): bad error recovery.
     super.test_string_simple_unterminated_interpolation_identifier();
   }
 }