Using move semantics allows an Option to keep track of the
initialization state while satisfying the borrow checker. This replaces
the functionality that the 'consumed' flag had before. It also retains
the smaller object size since the Option of a reference can use the
representation of the null pointer, which is an invalid reference, as a
niche for the None variant.
Closes: #301
Approved by: whitequark
This didn't ever actually cause UB because the drop implementation
should have compiled to a no-op under all conditions; `finish` is
a part of a patchset that never got in. (Even if it didn't, the code
should have been dynamically sound, under all but the most strict
interpretations of Rust's aliasing requirements.)
But it's still a problem, at least because there is a warning for
this potential unsoundness that will become an error in the future.
So everything else aside, we can't use this pattern going forward.
For now, remove the Drop impl, exploiting the fact that `finish`
is a no-op. Going forward this will likely require unsafe code, or
some fundamental change in the way SocketRef is implemented, but
I could not come up with any way to do it. :(
Dario Nieuwenhuis
Andreas Molzer
whitequark
Valentin Lorentz
Dan Robertson
whitequark
Egor Karavaev