Add AsRef, as_slice, as_str to more things #65901
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| @@ -42,7 +42,7 @@ __pycache__/ | |||
| /src/libcore/unicode/SpecialCasing.txt | |||
| /src/libcore/unicode/UnicodeData.txt | |||
| /src/libcore/unicode/downloaded | |||
| /target/ | |||
| target/ | |||
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Yes; I should have put it in a separate commit. RLS puts the target/ directory in src/libcore for me.
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This is libs territory, sorry, thought I'd already done this :) r? @dtolnay |
Centril
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Thanks for the PR! I am going to close because I don't feel that any of the methods or impls added here are sufficiently motivated.
I agree with you that adding associated methods to permutations of iterator adaptors is a rabbit hole.
Regarding the various AsRef impls, I guess I don't understand the use case. It's pretty uncommon for callers to need the genericness of AsRef in writing clear code. Do we really need someone to be able to make a CharIndices and pass it to fs::write in order to express what they mean in the clearest way? Not that permitting it would be bad, it's just not a need that people have and so it's not something that is worth designing for.
In my view the bar for adding surface area to the standard library isn't whether the behavior would be unambiguous to a reasonable observer ("never ultimately lead to unexpected behaviour" in your words), but whether people can get done what they need to get done with an effort that is proportional to how common their individual use case is. Instead of adding the most amount of surface area that remains unambiguous, we need to add the least amount of surface area that makes a usable library.
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This is somewhat related to #58957.
When writing some code I noticed the disparity between
CharIndices<'_>andEnumerate<Iter<'_, T>>; while you can get the original slice from the former, you can't from the latter.Essentially, I chose a relatively conservative list of adapters that would reasonably add this functionality where this would never ultimately lead to unexpected behaviour. For example, having
as_refforFilterorStepBywould likely lead to items being shown that aren't part of the iterator, which would be confusing. However,Clonedcan safely assumed to iterate its items in order, and addingas_refto that wouldn't be to weird.Ultimately, this fills in a few holes that seemed reasonable to fill, namely:
str::Byteshas anas_bytesmethod now and implementsAsRef<[u8]>,str::Charsandstr::CharIndicesnow implementAsRef<str>andAsRef<[u8]>. (unsure ifOsStrandPathshould be included, or[u8]should be excluded)iter::{Copied, Cloned, Enumerate}will have anas_slicemethod when wrapped around aslice::Iterorslice::IterMut, and anAsRef<[T]>implementation when wrappingslice::Iter.This honestly seems like an ever-deepening rabbit hole and I'm not sure where it should stop. That said, I feel that adding these methods to the above is shallow enough it shouldn't be too controversial.
Curious to see what people's thoughts are.