Implementing typestate

[Ola Fosheim Grøstad via Digitalmars-d]

On Wednesday, 16 September 2015 at 10:31:58 UTC, Idan Arye wrote:
> What's wrong with two `open()`s in a row? Each will return a 
> new file handle.

Yes, but if you do it by mistake then you don't get the compiler 
to check that you call close() on both. I should have written 
"what if you forget close()". Will the compiler then complain at 
compile time?

You can't make that happen with just move semantics, you need 
linear typing so that every resource created are consumed exactly 
once.