Question about luaH_newkey

[重归混沌 <findstrx@...>]

When I read the `luaH_newkey` function. 

I am a bit confused about the processing of mainposition(https://github.com/lua/lua/blob/master/ltable.c#L637) 。

Even if the gval(mp) is empty, it still may be in some chain。of course, the result is still correct. 

Is it possible that in some extreme cases, all slots are in one chain.

Please help me to point it out, if I have some mistakes. Thank you very much.