generate synthetic and error tokens when missing digit

pkg/front_end/lib/src/fasta/scanner/array_based_scanner.dart

 // Copyright (c) 2011, 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.
 
 library fasta.scanner.array_based_scanner;
 
 import 'error_token.dart' show ErrorToken, UnmatchedToken;
 
 import '../../scanner/token.dart'
     show
@@ skipping 244 matching lines @@
   }
 
   @override
   void appendSubstringToken(TokenType type, int start, bool asciiOnly,
       [int extraOffset = 0]) {
     appendToken(createSubstringToken(type, start, asciiOnly, extraOffset));
   }
 
   @override
   void appendSyntheticSubstringToken(
-      TokenType type, int start, bool asciiOnly, String closingQuotes) {
+      TokenType type, int start, bool asciiOnly, String syntheticChars) {
     appendToken(
-        createSyntheticSubstringToken(type, start, asciiOnly, closingQuotes));
+        createSyntheticSubstringToken(type, start, asciiOnly, syntheticChars));
   }
 
   /**
    * Returns a new substring from the scan offset [start] to the current
    * [scanOffset] plus the [extraOffset]. For example, if the current
    * scanOffset is 10, then [appendSubstringToken(5, -1)] will append the
    * substring string [5,9).
    *
    * Note that [extraOffset] can only be used if the covered character(s) are
    * known to be ASCII.
    */
   analyzer.StringToken createSubstringToken(
       TokenType type, int start, bool asciiOnly,
       [int extraOffset = 0]);
 
   /**
    * Returns a new synthetic substring from the scan offset [start]
-   * to the current [scanOffset] plus the [closingQuotes].
-   * The [closingQuotes] are appended to the unterminated string
+   * to the current [scanOffset] plus the [syntheticChars].
+   * The [syntheticChars] are appended to the unterminated string
    * literal's lexeme but the returned token's length will *not* include
-   * those closing quotes so as to be true to the original source.
+   * those additional characters so as to be true to the original source.
    */
   analyzer.StringToken createSyntheticSubstringToken(
-      TokenType type, int start, bool asciiOnly, String closingQuotes);
+      TokenType type, int start, bool asciiOnly, String syntheticChars);
 
   /**
    * This method is called to discard '<' from the "grouping" stack.
    *
    * [PartialParser.skipExpression] relies on the fact that we do not
    * create groups for stuff like:
    * [:a = b < c, d = e > f:].
    *
    * In other words, this method is called when the scanner recognizes
    * something which cannot possibly be part of a type parameter/argument
@@ skipping 65 matching lines @@
     //      |
     //     next
     //      v
     //     EOF
     TokenType type = closeBraceInfoFor(begin);
     appendToken(new SyntheticToken(type, tokenStart));
     begin.endGroup = tail;
     appendErrorToken(new UnmatchedToken(begin));
   }
 }