Incorrect rewriting of ENCAPSED strings

This code is rewritten incorrectly:
```<?php
$arr = ['json_encode' => 'json_encode'];
echo "json is {$arr['json_encode']($arr)}\n";
```

Result:
```<?php 
$arr = ['json_encode' => 'json_encode'];
echo "json is {\Badoo\SoftMocks::callFunction(__NAMESPACE__, $arr['json_encode'], array(&$arr))}\n";
````