swiftlang/swift

[SR-1959] Use Bounds.Stride for Index on countable ranges

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#44,568 创建于 2016年7月1日

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affects ABIgood first issueimprovementstandard libraryswift evolution proposal needed

描述
Previous ID SR-1959
Radar rdar://problem/26302563
Original Reporter @gribozavr
Type Bug
Votes 0
Component/s Standard Library
Labels Bug, AffectsABI, StarterProposal, swift-evolution-proposal-needed
Assignee None
Priority Medium

md5: 6a8b1ccf3e51e9239df2d35454f79393

Issue Description:

CountableRange collection conformance defines an Index type that conforms to Strideable. That is not the case for the CountableClosedRange, which makes the two ranges not interchangeable in all cases.

ClosedRangeIndex implementation uses an internal enum that makes Strideable conformance hard to implement.

The proposed solution is to use Bounds.Stride as Index on both CountableRange and CountableClosedRange.

  • It is proposed to use `Bound.Stride` as index for both countable ranges.

  • The only problem with that is that `SubSequence` of a countable range can no longer be the same type (as indices will not be interchangeable). [Why is this? Someone needs to reconstruct the logic chain.]

  • But it can be solved by using one of the existing slice types for `SubSequence`.

NOTE: Requires a swift-evolution proposal.

贡献者指南

技术栈
swift
领域
backenddeveloper experience
议题类型
bug
难度面向新贡献者的预计实现难度，1 表示很小改动，5 表示专家级工作。
4
预计时间有经验贡献者完成调查、实现、测试并准备 pull request 的粗略时间范围。
over 1 week
活动状态议题当前的可参与程度：新鲜、活跃、陈旧、阻塞或等待维护者输入。
stale
清晰度议题是否清楚说明期望改动、验收标准和下一步。
mostly clear
前置要求
SwiftGenericsStrideable protocolABI stability
新手友好度1-100 的估计分数，表示该议题对首次贡献者的友好程度。
20
研究方向
This issue from 2016 proposes using Bound.Stride as the index type for countable ranges to make CountableClosedRange and CountableRange interchangeable. The contributor should first understand the current implementation in the Swift standard library (e.g., Range.swift file) and the challenges with the enum based index for ClosedRangeIndex. Since a swift evolution proposal is required, the first step is to write a pitch for the community and discuss on the forums. After consensus, the implementation can change the index type and adjust the SubSequence type to use existing slice types.
[SR-1959] Use Bounds.Stride for Index on countable ranges · swiftlang/swift#44568 | Good First Issue