swiftlang/swift

[SR-11397] FixedWidthInteger.init?(_: radix:) fails for Self with short bitWidth

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#53,798 opened on Aug 30, 2019

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 (5 comments) (0 reactions) (1 assignee)Swift (69,989 stars) (10,719 forks)batch import
buggood first issuestandard library

Description
Previous ID SR-11397
Radar None
Original Reporter CTMacUser (JIRA User)
Type Bug
Votes 0
Component/s Standard Library
Labels Bug, StarterBug
Assignee @theblixguy
Priority Medium

md5: 71036ce9352bad83dc05a0cfcdea3df7

Issue Description:

The current implementation of FixedWidthInteger.init?(_: radix: ) converts the radix to the receiver type. If that type has less than 6 bits of width, not all radix values are supported and a run error happens at the conversion.

Theoretically, any width above zero should work if we go to a bignum implementation. I'm not suggesting we do that, but that workaround indicates we shouldn't return a nil from the initializer in such cases, because that would imply a user error and not a implementation error. I guess a fatal error is more appropriate.

(BTW, my code was testing with a zero-width type, so there may be other problems.)

Contributor guide

Tech stack
swift
Domain
backend
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
SwiftgenericsFixedWidthInteger protocolradix conversion
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
75
Research direction
Look into the current implementation of FixedWidthInteger.init?( : radix:) in the Swift standard library, likely in IntegerTypes.swift. The issue describes that for types with bit width less than 6, the radix conversion to the receiver type fails. Consider replacing the current behavior with a fatal error for unsupported radices, as suggested. Review comments for any additional context; note the assignee @theblixguy may have existing work.