Prevent double reporting on hex, strings, and multiline comments.

sdk/lib/_internal/compiler/implementation/scanner/scanner.dart

 // Copyright (c) 2012, 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.
 
 part of scanner;
 
 abstract class Scanner {
   Token tokenize();
 
   factory Scanner(SourceFile file, {bool includeComments: false}) {
@@ skipping 610 matching lines @@
     next = advance(); // Advance past the $x or $X.
     bool hasDigits = false;
     while (true) {
       next = advance();
       if (($0 <= next && next <= $9)
           || ($A <= next && next <= $F)
           || ($a <= next && next <= $f)) {
         hasDigits = true;
       } else {
         if (!hasDigits) {
-          return unterminated('0x');
+          unterminated('0x', shouldAdvance: false);
+          return next;
         }
         appendSubstringToken(HEXADECIMAL_INFO, start, true);
         return next;
       }
     }
     return null;
   }
 
   int tokenizeDotsOrNumber(int next) {
     int start = scanOffset;
@@ skipping 300 matching lines @@
       next = tokenizeIdentifier(next, scanOffset, false);
     } else {
       unterminated(r'$', shouldAdvance: false);
     }
     beginToken(); // The string interpolation suffix starts here.
     return next;
   }
 
   int tokenizeSingleLineRawString(int next, int quoteChar, int start) {
     bool asciiOnly = true;
-    next = advance(); // Advance past the quote.
     while (next != $EOF) {
       if (identical(next, quoteChar)) {
         if (!asciiOnly) handleUnicode(start);
         next = advance();
         appendSubstringToken(STRING_INFO, start, asciiOnly);
         return next;
       } else if (identical(next, $LF) || identical(next, $CR)) {
         if (!asciiOnly) handleUnicode(start);
         return unterminatedRawString(quoteChar);
       } else if (next > 127) {
@@ skipping 108 matching lines @@
   }
 
   int unterminatedRawString(int quoteChar) {
     return unterminated('r${new String.fromCharCodes([quoteChar])}');
   }
 
   int unterminatedMultiLineString(int quoteChar) {
     return unterminated(
         new String.fromCharCodes([quoteChar, quoteChar, quoteChar]));
   }
+
   int unterminatedRawMultiLineString(int quoteChar) {
     return unterminated(
         'r${new String.fromCharCodes([quoteChar, quoteChar, quoteChar])}');
   }
 
   int advanceAfterError(bool shouldAdvance) {
     if (atEndOfFile()) return $EOF;
     if (shouldAdvance) {
       return advance(); // Ensure progress.
     } else {
@@ skipping 55 matching lines @@
 
 PrecedenceInfo closeBraceInfoFor(BeginGroupToken begin) {
   return const {
     '(': CLOSE_PAREN_INFO,
     '[': CLOSE_SQUARE_BRACKET_INFO,
     '{': CLOSE_CURLY_BRACKET_INFO,
     '<': GT_INFO,
     r'${': CLOSE_CURLY_BRACKET_INFO,
   }[begin.value];
 }