Skeleton for lexical error recovery.

pkg/dart_scanner/lib/src/recover.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 licenset hat can be found in the LICENSE file.
+
+library dart_scanner.recover;
+
+import 'token.dart' show
+    Token;
+
+/// Recover from errors in [tokens]. The original sources are provided as
+/// [bytes]. [lineStarts] are the beginning character offsets of lines, and
+/// must be updated if recovery is performed rewriting the original source
+/// code.
+Token defaultRecoveryStrategy(
+    List<int> bytes, Token tokens, List<int> lineStarts) {
+  // See [Parser.reportErrorToken](package:dart_parser/src/parser.dart) for how
+  // it currently handles lexical errors. In addition, notice how the parser
+  // calls [handleInvalidExpression], [handleInvalidFunctionBody], and
+  // [handleInvalidTypeReference] to allow the listener to recover its internal
+  // state. See [package:compiler/src/parser/element_listener.dart] for an
+  // example of how these events are used.
+  //
+  // In addition, the scanner will attempt a bit of recovery when braces don't
+  // match up during brace grouping. See
+  // [ArrayBasedScanner.discardBeginGroupUntil](array_based_scanner.dart). For
+  // more details on brace grouping see
+  // [AbstractScanner.unmatchedBeginGroup](abstract_scanner.dart).
+  return tokens;
+}