swiftlang/swift

[SR-14941] Introduce compiler warning for leading-zero octal notation

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#57,283 opened on Jul 19, 2021

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good first issueimprovement

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Description
Previous ID SR-14941
Radar rdar://problem/22123688
Original Reporter eaigner (JIRA User)
Type Improvement
Votes 0
Component/s
Labels Improvement, StarterBug
Assignee None
Priority Medium

md5: 639a9bd96ac9c3918c5433098fa9ad29

Issue Description:

I had a bug in my code for quite some time that went by unnoticed, because I didn't realize Swift handled octal numbers differently. Specifically I was making the following call

mkfifo(path, 0644)

This should obviously read `0o644`, but went by unnoticed, since it just resulted in an elevated user permission.

It would be great if the compiler could warn in such instances where numbers are typed with leading zeroes, maybe something of the form "Did you mean to write an octal number?"

Contributor guide

Research direction
Investigate how the Swift compiler's lexer handles integer literals with leading zeros, and study existing compiler warnings (e.g., for deprecated syntax) to model a new warning. Look at how other languages like Python or Rust warn about leading zero octal. The warning should trigger when a literal has leading zeros and is not explicitly octal (0o). Check the SwiftAST or Lexer source files in the swift repository.
Tech stack
swift
Domain
compilers
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
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.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
Swift
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
85