Is the `in` operator @safe?

[Luís Marques]

After a quick look it seems like the `in` operator may return a 
pointer that becomes invalid when an AA is resized:

https://github.com/dlang/druntime/blob/master/src/rt/aaA.d#L601
https://github.com/dlang/druntime/blob/master/src/rt/aaA.d#L114
https://github.com/dlang/druntime/blob/master/src/rt/aaA.d#L193

Yet you can use `in` in @safe functions and keep the pointer 
around. Is my assessment correct, or did I overlook anything? If 
so, I'll open a bug report (I didn't find one already open for 
that, but maybe I searched the wrong keywords).