enh(csharp) add support for @identifier style identifiers (#2414)

CHANGES.md

@@ -16,6 +16,7 @@ Core Changes:
 
 Language Improvements:
 
+- (csharp) add support for `@identifier` style identifiers (#2414) [Josh Goebel][]
 - fix(elixir) Support function names with a slash (#2406) [Josh Goebel][]
 - fix(javascript) comma is allowed in a "value container" (#2403) [Josh Goebel][]
 - enh(apache) add `deny` and `allow` keywords [Josh Goebel][]

src/languages/csharp.js

@@ -93,6 +93,12 @@ export default function(hljs) {
     keywords: "in out"
   };
   var TYPE_IDENT_RE = hljs.IDENT_RE + '(<' + hljs.IDENT_RE + '(\\s*,\\s*' + hljs.IDENT_RE + ')*>)?(\\[\\])?';
+  var AT_IDENTIFIER = {
+    // prevents expressions like `@class` from incorrect flagging
+    // `class` as a keyword
+    begin: "@" + hljs.IDENT_RE,
+    relevance: 0
+  };
 
   return {
     name: 'C#',
@@ -195,7 +201,8 @@ export default function(hljs) {
           hljs.C_LINE_COMMENT_MODE,
           hljs.C_BLOCK_COMMENT_MODE
         ]
-      }
+      },
+      AT_IDENTIFIER
     ]
   };
 }

test/markup/csharp/identifiers.expect.txt

@@ -0,0 +1,3 @@
+<span class="hljs-keyword">var</span> @class = <span class="hljs-keyword">new</span> MyClass();
+doSomething(@var, @foo);
+<span class="hljs-keyword">var</span> a;

test/markup/csharp/identifiers.txt

@@ -0,0 +1,4 @@
+var @class = new MyClass();
+doSomething(@var, @foo);
+var a;
+