gistfile1.txt

ckwalsh@ckwalsh:~$ cat foo.php 
<?hh
 
namespace Foo;
 
class Bar {
	function foobar(): this {
		return $this;
	}
}
 
$b = new Bar();
$b2 = $b->foobar();
ckwalsh@ckwalsh:~$ hhvm --version
HipHop VM 3.1.0-dev+2014.04.18 (rel)
Compiler: heads/master-0-gccf06d57ebf7da5f9cab87dcdfa1439494a7e34b
Repo schema: 612222bbdfacd77d127e829b0e7e928b04905850
ckwalsh@ckwalsh:~$ hhvm foo.php 

Fatal error: Value returned from Foo\Bar::foobar() must be of type Foo\this, Foo\Bar given in /home/ckwalsh/foo.php on line 7
ckwalsh@ckwalsh:~$