fixes #1724 for heregexen

TODO: DRY up that regex handling code so we don't have a duplicate test/error

lib/coffee-script/lexer.js

@@ -207,6 +207,9 @@
       heregex = match[0], body = match[1], flags = match[2];
       if (0 > body.indexOf('#{')) {
         re = body.replace(HEREGEX_OMIT, '').replace(/\//g, '\\/');
+        if (re.match(/^\*/)) {
+          this.error('regular expressions cannot begin with `*`');
+        }
         this.token('REGEX', "/" + (re || '(?:)') + "/" + flags);
         return heregex.length;
       }