Tweaks to string escapes. Added raw string literals.

utils/vim/syntax/dart.vim

 " Vim syntax file " Language: 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.
 
 " Quit when a syntax file was already loaded
 if !exists("main_syntax")
   if version < 600
     syntax clear
   elseif exists("b:current_syntax")
     finish
   endif
   " we define it here so that included files can test for it
   let main_syntax='dart'
   syn region dartFold start="{" end="}" transparent fold
 endif
 
 " keyword definitions
 syn keyword dartConditional    if else switch
 syn keyword dartRepeat         while for
 syn keyword dartBoolean        true false
 syn keyword dartConstant       null
 syn keyword dartTypedef        this super class typedef
 syn keyword dartOperator       new is in factory
-syn match   dartOperator       "+\|-\|*\|[~]\=/\|%\|||\|&&\|\(!\|=\)=[=]\=\|=>\|="
+syn match   dartOperator       "+\|-\|*\|[~]\=/\|%\|||\|&&\|\(!\|=\)=[=]\=\|=>\|[<>]=\|=\|!"
 syn keyword dartType           void var const bool int double num
 syn keyword dartStatement      return
 syn keyword dartStorageClass   static final abstract
 syn keyword dartExceptions     throw try catch finally
 syn keyword dartAssert         assert
 syn keyword dartClassDecl      extends implements interface
 " TODO(antonm): check if labels on break and continue are supported.
 syn keyword dartBranch         break continue nextgroup=dartUserLabelRef skipwhite
 syn keyword dartKeyword        function get set
 syn match   dartUserLabelRef   "\k\+" contained
 syn match   dartVarArg         "\.\.\."
 
 " TODO(antonm): consider conditional highlighting of corelib classes.
 
 syn region  dartLabelRegion   transparent matchgroup=dartLabel start="\<case\>" matchgroup=NONE end=":"
 syn keyword dartLabel         default
 
 " Comments
 syn keyword dartTodo          contained TODO FIXME XXX
 syn region  dartComment       start="/\*"  end="\*/" contains=dartTodo,dartDocLink,@Spell
 syn match   dartLineComment   "//.*" contains=dartTodo,@Spell
 syn region  dartDocLink       contained start=+\[+ end=+\]+
 
 " Strings
-syn region  dartString       start=+"+ end=+"+ contains=@Spell,dartInterpolation,dartSpecialChar
-syn region  dartString       start=+'+ end=+'+ contains=@Spell,dartInterpolation,dartSpecialChar
-syn match   dartInterpolation     contained "\$\(\w\+\|{[^\}]\+}\)"
-syn match   dartSpecialChar       contained "\\\([4-9]\d\|[0-3]\d\d\|[\"\\'ntbrf]\|u\x\{4\}\)"
+syn region  dartString        start=+\z(["']\)+hs=s+1 end=+\z1+he=e-1 contains=@Spell,dartInterpolation,dartSpecialChar
+syn region  dartRawString     start=+@\z(["']\)+hs=s+2 end=+\z1+he=e-1 contains=@Spell
+syn match   dartInterpolation contained "\$\(\w\+\|{[^}]\+}\)"
+syn match   dartSpecialChar   contained "\\\(u\x\{4\}\|u{\x\+}\|x\x\x\|x{\x\+}\|.\)"
 
 " Numbers
 syn match dartNumber         "\<\d\+\(\.\d\+\)\=\>"
 
 " The default highlighting.
 command! -nargs=+ HiLink hi def link <args>
 HiLink dartVarArg          Function
 HiLink dartBranch          Conditional
 HiLink dartUserLabelRef    dartUserLabel
 HiLink dartLabel           Label
 HiLink dartUserLabel       Label
 HiLink dartConditional     Conditional
 HiLink dartRepeat          Repeat
 HiLink dartExceptions      Exception
 HiLink dartAssert          Statement
 HiLink dartStorageClass    StorageClass
 HiLink dartClassDecl       dartStorageClass
 HiLink dartBoolean         Boolean
 HiLink dartString          String
+HiLink dartRawString       String
 HiLink dartNumber          Number
 HiLink dartStatement       Statement
 HiLink dartOperator        Operator
 HiLink dartComment         Comment
 HiLink dartLineComment     Comment
 HiLink dartConstant        Constant
 HiLink dartTypedef         Typedef
 HiLink dartTodo            Todo
 HiLink dartKeyword         Keyword
 HiLink dartType            Type
 HiLink dartInterpolation   PreProc
 HiLink dartDocLink         SpecialComment
 HiLink dartSpecialChar     SpecialChar
 delcommand HiLink
 
 let b:current_syntax = "dart"
 
 if main_syntax == 'dart'
   unlet main_syntax
 endif
 
 let b:spell_options="contained"