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[SR-3836] The SubSequence of a Range should be a Range #46421

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dabrahams opened this issue Feb 2, 2017 · 5 comments
Closed

[SR-3836] The SubSequence of a Range should be a Range #46421

dabrahams opened this issue Feb 2, 2017 · 5 comments
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@dabrahams
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. good first issue Good for newcomers standard library Area: Standard library umbrella

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@dabrahams
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Previous ID SR-3836
Radar None
Original Reporter @dabrahams
Type Bug
Status Closed
Resolution Cannot Reproduce
Additional Detail from JIRA
Votes 0
Component/s Standard Library
Labels Bug, StarterBug
Assignee @dabrahams
Priority Medium

md5: 8d1c0acd570b0e835bd5108fb26423ab

Issue Description:

Cluttering up the type with a RandomAccessSlice<...> wrapper or whatever has no purpose.
Same goes for CountableRange as long as it's around.

Thought should be given to whether ClosedRange.SubSequence can/should be a ClosedRange or must be a Range
@natecook1000
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A ClosedRange.SubSequence would need to be able to represent an empty range, so ClosedRange is out for that.

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Comment by David Sweeris (JIRA)

Once conditional conformance hits, could we just say that SubSequence equals Optional<Self>? That way we could just make it nil for empty ranges regardless of whether `Self` can represent such a thing. What do y'all think? Is it worth bringing up on evolution?

@dabrahams
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Dave (JIRA User) No, the SubSequence type is constrained by all kinds of things that Optional<Self> can't fulfill, e.g. it needs to be a Sequence having the same Element type.

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Comment by David Sweeris (JIRA)

Has it already been fixed? The only place I can find "typealias SubSequence = RandomAccessSlice" anywhere in the source directory is in the definition of RandomAccessSlice itself.

@dabrahams
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Yep!

(swift) print(CountableRange<Int>.SubSequence.self)
CountableRange<Int>
(swift) print(CountableClosedRange<Int>.SubSequence.self)
RandomAccessSlice<CountableClosedRange<Int>>
(swift)

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
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@dabrahams dabrahams

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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. good first issue Good for newcomers standard library Area: Standard library umbrella
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@dabrahams @natecook1000 @swift-ci