swiftlang/swift

[SR-11885] Allow operator functions to have extra arguments with default values

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#54,301 opened on Dec 2, 2019

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compilerdeclarationsfeaturefuncgood first issueimprovementoperatorsswift evolution proposal needed

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Description
Previous ID SR-11885
Radar rdar://problem/57711758
Original Reporter @CodaFi
Type New Feature
Votes 1
Component/s Compiler
Labels New Feature, LanguageFeatureRequest, StarterBug, StarterProposal
Assignee mininny (JIRA)
Priority Medium

md5: 210d53f6b32e8240f74a2e7677a3c698

Issue Description:

It might make sense to allow operators to have default arguments, and for those defaults to not count towards the overall arity of the operator. For example, a custom operator `<-` could have `#line` and `#file` defaults in a debug configuration. It could then check some extra invariants in a particular configuration, or do some error reporting, etc.

infix operator <-
// Still infix because it has 2 formal arguments and 1 default
public func <- (lhs: T, rhs :T, file: StaticString = #file) -> U { /**/ }

This change requires an evolution proposal.

Contributor guide

Research direction
Read the Swift evolution proposal process and understand how operator arity is currently constrained.
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
GitSwift
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
70