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Update unresolved questions and drawbacks for the FusedIterator RFC 

1. We can't remove the `done` bool without making `Fuse` invariant.
2. One drawback I failed to mention is that implementing `FusedIterator` locks
implementors into obeying the `FusedIterator` spec.
This commit is contained in:
Steven Allen 2016-08-22 12:03:42 -04:00
parent 44c24bdfe5
commit 67a14dc22e
1 changed files with 12 additions and 4 deletions
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@ -190,6 +190,12 @@ impl<I> Iterator for Fuse<I> where I: FusedIterator {
3. Fuse isn't used very often anyways. However, I would argue that it should be
used more often and people are just playing fast and loose. I'm hoping that
making `Fuse` free when unneeded will encourage people to use it when they should.
4. This trait locks implementors into following the `FusedIterator` spec;
removing the `FusedIterator` implementation would be a breaking change. This
precludes future optimizations that take advantage of the fact that the
behavior of an `Iterator` is undefined after it returns `None` the first
time.
# Alternatives
@ -268,9 +274,11 @@ change.
[unresolved]: #unresolved-questions
Should this trait be unsafe? I can't think of any way generic unsafe code could
end up relying on the guarantees of `Fused`.
end up relying on the guarantees of `FusedIterator`.
Also, it's possible to implement the specialized `Fuse` struct without a useless
`don` bool. Unfortunately, it's *very* messy. IMO, this is not worth it for now
~~Also, it's possible to implement the specialized `Fuse` struct without a useless
`done` bool. Unfortunately, it's *very* messy. IMO, this is not worth it for now
and can always be fixed in the future as it doesn't change the `FusedIterator`
trait.
trait.~~ Resolved: It's not possible to remove the `done` bool without making
`Fuse` invariant.