Match options directly in the Fuse implementation#70750
Match options directly in the Fuse implementation#70750bors merged 2 commits intorust-lang:masterfrom
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@bors try @rust-timer queue |
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Awaiting bors try build completion |
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⌛ Trying commit 6fdd4f3 with merge ec7a02385a47e4dfcfa6ca70e1f167ba4a3f8985... |
| self.iter = None; | ||
| } | ||
| nth | ||
| fuse!(self.iter.nth(n)) |
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This is beautiful. Nicely done.
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☀️ Try build successful - checks-azure |
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Queued ec7a02385a47e4dfcfa6ca70e1f167ba4a3f8985 with parent f6fe99c, future comparison URL. |
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| default fn next(&mut self) -> Option<<I as Iterator>::Item> { | |||
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Unrelated to the tweaks in this PR... there's a default fn here and elsewhere that shouldn't be (Specialization should be negotiated through internal traits.)
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Hmm, it's been like that for a little while...
https://github.com/rust-lang/rust/pull/35656/files#diff-d93bf2799d551e25b17e877b23a37db3L1659-R1726
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Sure, we discovered problematic usage of associated type defaults much older, still, it needed to be fixed however old. :)
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@Centril Maybe open an E-Easy issue for it with instructions for a new contributor to pick up? I agree that it's "unrelated to the tweaks in this PR", so I don't think it needs to happen here.
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Finished benchmarking try commit ec7a02385a47e4dfcfa6ca70e1f167ba4a3f8985, comparison URL. |
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This looks fairly neutral, but I suspect that's largely due to most iterators hitting the specialization, not the interesting ones. We've seen a bunch of examples where this is helpful (the @bors r+ |
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📌 Commit 6fdd4f3 has been approved by |
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Match options directly in the Fuse implementation Rather than using `as_ref()`, `as_mut()`, and `?`, we can use `match` directly to save a lot of generated code. This was mentioned as a possibility in rust-lang#70366 (comment), and I found that it had a very large impact on rust-lang#70332 using `Fuse` within `Chain`. Let's evaluate this change on its own first.
Rollup of 7 pull requests Successful merges: - rust-lang#70553 (move OS constants to platform crate) - rust-lang#70665 (Do not lose or reorder user-provided linker arguments) - rust-lang#70750 (Match options directly in the Fuse implementation) - rust-lang#70782 (Stop importing the float modules in documentation) - rust-lang#70798 ("cannot resolve" → "cannot satisfy") - rust-lang#70808 (Simplify dtor registration for HermitCore by using a list of destructors) - rust-lang#70824 (Remove marker comments in libstd/lib.rs macro imports) Failed merges: r? @ghost
Implement Chain with Option fuses The iterators are now "fused" with `Option` so we don't need separate state to track which part is already exhausted, and we may also get niche layout for `None`. We don't use the real `Fuse` adapter because its specialization for `FusedIterator` unconditionally descends into the iterator, and that could be expensive to keep revisiting stuff like nested chains. It also hurts compiler performance to add more iterator layers to `Chain`. This change was inspired by the [proposal](https://internals.rust-lang.org/t/proposal-implement-iter-chain-using-fuse/12006) on the internals forum. This is an alternate to rust-lang#70332, directly employing some of the same `Fuse` optimizations as rust-lang#70366 and rust-lang#70750. r? @scottmcm
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Rather than using
as_ref(),as_mut(), and?, we can usematchdirectly to save a lot of generated code. This was mentioned as a possibility in #70366 (comment), and I found that it had a very large impact on #70332 usingFusewithinChain. Let's evaluate this change on its own first.