Update dart2js parser to disallow repeated comparisons and prefix +.

sdk/lib/_internal/compiler/implementation/scanner/token.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.
 
 part of scanner;
 
 const int EOF_TOKEN = 0;
 
 const int KEYWORD_TOKEN = $k;
 const int IDENTIFIER_TOKEN = $a;
@@ skipping 413 matching lines @@
 const PrecedenceInfo BAR_INFO =
   const PrecedenceInfo(const SourceString('|'), 8, BAR_TOKEN);
 
 const PrecedenceInfo CARET_INFO =
   const PrecedenceInfo(const SourceString('^'), 9, CARET_TOKEN);
 
 const PrecedenceInfo AMPERSAND_INFO =
   const PrecedenceInfo(const SourceString('&'), 10, AMPERSAND_TOKEN);
 
 // Equality operators.
+const int EQUALITY_PRECEDENCE = 6;
 const PrecedenceInfo BANG_EQ_EQ_INFO =
-  const PrecedenceInfo(const SourceString('!=='), 6, BANG_EQ_EQ_TOKEN);
+  const PrecedenceInfo(const SourceString('!=='),
+                       EQUALITY_PRECEDENCE, BANG_EQ_EQ_TOKEN);
 const PrecedenceInfo BANG_EQ_INFO =
-  const PrecedenceInfo(const SourceString('!='), 6, BANG_EQ_TOKEN);
+  const PrecedenceInfo(const SourceString('!='),
+                       EQUALITY_PRECEDENCE, BANG_EQ_TOKEN);
 const PrecedenceInfo EQ_EQ_EQ_INFO =
-  const PrecedenceInfo(const SourceString('==='), 6, EQ_EQ_EQ_TOKEN);
+  const PrecedenceInfo(const SourceString('==='),
+                       EQUALITY_PRECEDENCE, EQ_EQ_EQ_TOKEN);
 const PrecedenceInfo EQ_EQ_INFO =
-  const PrecedenceInfo(const SourceString('=='), 6, EQ_EQ_TOKEN);
+  const PrecedenceInfo(const SourceString('=='),
+                       EQUALITY_PRECEDENCE, EQ_EQ_TOKEN);
 
 // Relational operators.
+const int RELATIONAL_PRECEDENCE = 7;
 const PrecedenceInfo GT_EQ_INFO =
-  const PrecedenceInfo(const SourceString('>='), 7, GT_EQ_TOKEN);
+  const PrecedenceInfo(const SourceString('>='),
+                       RELATIONAL_PRECEDENCE, GT_EQ_TOKEN);
 const PrecedenceInfo GT_INFO =
-  const PrecedenceInfo(const SourceString('>'), 7, GT_TOKEN);
+  const PrecedenceInfo(const SourceString('>'),
+                       RELATIONAL_PRECEDENCE, GT_TOKEN);
 const PrecedenceInfo IS_INFO =
-  const PrecedenceInfo(const SourceString('is'), 7, KEYWORD_TOKEN);
+  const PrecedenceInfo(const SourceString('is'),
+                       RELATIONAL_PRECEDENCE, KEYWORD_TOKEN);
 const PrecedenceInfo AS_INFO =
-  const PrecedenceInfo(const SourceString('as'), 7, KEYWORD_TOKEN);
+  const PrecedenceInfo(const SourceString('as'),
+                       RELATIONAL_PRECEDENCE, KEYWORD_TOKEN);
 const PrecedenceInfo LT_EQ_INFO =
-  const PrecedenceInfo(const SourceString('<='), 7, LT_EQ_TOKEN);
+  const PrecedenceInfo(const SourceString('<='),
+                       RELATIONAL_PRECEDENCE, LT_EQ_TOKEN);
 const PrecedenceInfo LT_INFO =
-  const PrecedenceInfo(const SourceString('<'), 7, LT_TOKEN);
+  const PrecedenceInfo(const SourceString('<'),
+                       RELATIONAL_PRECEDENCE, LT_TOKEN);
 
 // Shift operators.
 const PrecedenceInfo GT_GT_INFO =
   const PrecedenceInfo(const SourceString('>>'), 11, GT_GT_TOKEN);
 const PrecedenceInfo LT_LT_INFO =
   const PrecedenceInfo(const SourceString('<<'), 11, LT_LT_TOKEN);
 
 // Additive operators.
 const PrecedenceInfo MINUS_INFO =
   const PrecedenceInfo(const SourceString('-'), 12, MINUS_TOKEN);
@@ skipping 67 matching lines @@
 
 const PrecedenceInfo HEXADECIMAL_INFO =
   const PrecedenceInfo(const SourceString('hexadecimal'), 0, HEXADECIMAL_TOKEN);
 
 const PrecedenceInfo COMMENT_INFO =
   const PrecedenceInfo(const SourceString('comment'), 0, COMMENT_TOKEN);
 
 // For reporting lexical errors.
 const PrecedenceInfo ERROR_INFO =
   const PrecedenceInfo(const SourceString('?'), 0, UNKNOWN_TOKEN);