fix $this in string interpolation

frog/frogsh

 #!/usr/bin/env node
 //  ********** Library dart:core **************
 //  ********** Natives dart:core **************
 /**
  * Generates a dynamic call stub for a function.
  * Our goal is to create a stub method like this on-the-fly:
  *   function($0, $1, capture) { this($0, $1, true, capture); }
  *
  * This stub then replaces the dynamic one on Function, with one that is
  * specialized for that particular function, taking into account its default
@@ skipping 17333 matching lines @@
       text = $add(text.substring$2(0, text.length - 1), endQuote);
     }
     else {
       text = $add($add(startQuote, text.substring$2(0, text.length - 1)), endQuote);
     }
     lits.add$1(this.makeStringLiteral($assert_String(text), token.get$span()));
     if ($notnull_bool(this._maybeEat(6/*TokenKind.LBRACE*/))) {
       lits.add$1(this.expression());
       this._eat(7/*TokenKind.RBRACE*/);
     }
+    else if ($notnull_bool(this._maybeEat(108/*TokenKind.THIS*/))) {
+      lits.add$1(new ThisExpression(this._previousToken.get$span()));
+    }
     else {
       var id = this.identifier();
       lits.add$1(new VarExpression(id, id.get$span()));
     }
   }
   var tok = this._lang_next();
   if ($notnull_bool($ne(tok.kind, 58/*TokenKind.STRING*/))) {
     this._errorExpected('interpolated string');
   }
   var text = $add(startQuote, tok.get$text());
@@ skipping 147 matching lines @@
   }
   else {
     return -1;
   }
 }
 lang_Parser.parseHex = function(hex) {
   var result = 0;
   for (var i = 0;
    i < hex.length; i++) {
     var digit = lang_Parser._hexDigit(hex.charCodeAt(i));
-    $assert($ne(digit, -1), "digit != -1", "parser.dart", 1259, 14);
+    $assert($ne(digit, -1), "digit != -1", "parser.dart", 1261, 14);
     result = (result << 4) + $assert_num(digit);
   }
   return $assert_num(result);
 }
 lang_Parser.prototype.finishNewExpression = function(start, isConst) {
   var type = this.type(0);
   var name = null;
   if ($notnull_bool(this._maybeEat(14/*TokenKind.DOT*/))) {
     name = this.identifier();
   }
@@ skipping 4200 matching lines @@
       INTERFACE,
       LIBRARY,
       NATIVE,
       NEGATE,
       OPERATOR,
       SET,
       SOURCE,
       STATIC,
       TYPEDEF ]*/;
 main();