Description:
------------
Attempting to import/inherit $this produces the compile-time error 
"Cannot use $this as lexical variable."

Note that the workaround of assigning $this to the temporary variable 
$tmp, and inheriting $tmp instead does work, so there appears to be no 
limitation in the engine:

class Foo {

    public function bar() {

        $tmp = $this;
        return function() use ($tmp) {
            echo "in closure\n";
        }

    }

}

See also http://wiki.php.net/rfc/closures/removal-of-this.  (It 
appears that $this was once automatically imported into the closure's 
scope, but that this turned out to be a bad idea.  This bug report 
concerns what happens when $this is explicitly imported, however.)

Reproduce code:
---------------
<?php

class Foo {

    public function bar() {

        return function() use ($this) {
            echo "in closure\n";
        }

    }

}



Expected result:
----------------
in closure

Actual result:
--------------
PHP Fatal error:  Cannot use $this as lexical variable in 
/mnt/hgfs/workspace/scratch/wart2.php on line 7