fix(rust) prevent symbol from gobbling strings

Author: joshgoebel

src/languages/rust.js

@@ -200,7 +200,8 @@ export default function(hljs) {
       }),
       {
         className: 'symbol',
-        begin: /'[a-zA-Z_][a-zA-Z0-9_]*/
+        // negative lookahead to avoid matching `'`
+        begin: /'[a-zA-Z_][a-zA-Z0-9_]*(?!')/
       },
       {
         scope: 'string',

test/markup/rust/strings.expect.txt

@@ -3,6 +3,7 @@
 <span class="hljs-string">&#x27;<span class="hljs-char escape_">\x</span>1A&#x27;</span>;
 <span class="hljs-string">&#x27;<span class="hljs-char escape_">\u</span>12AS&#x27;</span>;
 <span class="hljs-string">&#x27;<span class="hljs-char escape_">\U</span>1234ASDF&#x27;</span>;
+<span class="hljs-string">&#x27;😭&#x27;</span>;
 <span class="hljs-string">b&#x27;a&#x27;</span>;
 
 <span class="hljs-string">&quot;hello&quot;</span>;
@@ -12,6 +13,7 @@
 <span class="hljs-string">r###&quot;world&quot;###</span>;
 <span class="hljs-string">r##&quot; &quot;###
 &quot;# &quot;##</span>;
+<span class="hljs-string">&quot;😭😭😭😭&quot;</span>;
 
 <span class="hljs-string">br&quot; &quot;</span>;
 <span class="hljs-string">br#&quot;hello&quot;#</span>;

test/markup/rust/strings.txt

@@ -3,6 +3,7 @@
 '\x1A';
 '\u12AS';
 '\U1234ASDF';
+'😭';
 b'a';
 
 "hello";
@@ -12,6 +13,7 @@ r"hello";
 r###"world"###;
 r##" "###
 "# "##;
+"😭😭😭😭";
 
 br" ";
 br#"hello"#;