[groovy mode] Highlight interpolated variables without braces

Closes #6899

Author: marijnh

mode/groovy/groovy.js

@@ -91,9 +91,14 @@ CodeMirror.defineMode("groovy", function(config) {
           if (!tripleQuoted) { break; }
           if (stream.match(quote + quote)) { end = true; break; }
         }
-        if (quote == '"' && next == "$" && !escaped && stream.eat("{")) {
-          state.tokenize.push(tokenBaseUntilBrace());
-          return "string";
+        if (quote == '"' && next == "$" && !escaped) {
+          if (stream.eat("{")) {
+            state.tokenize.push(tokenBaseUntilBrace());
+            return "string";
+          } else if (stream.match(/^\w/, false)) {
+            state.tokenize.push(tokenVariableDeref);
+            return "string";
+          }
         }
         escaped = !escaped && next == "\\";
       }
@@ -122,6 +127,15 @@ CodeMirror.defineMode("groovy", function(config) {
     return t;
   }
 
+  function tokenVariableDeref(stream, state) {
+    var next = stream.match(/^(\.|[\w\$_]+)/)
+    if (!next) {
+      state.tokenize.pop()
+      return state.tokenize[state.tokenize.length-1](stream, state)
+    }
+    return next[0] == "." ? null : "variable"
+  }
+
   function tokenComment(stream, state) {
     var maybeEnd = false, ch;
     while (ch = stream.next()) {