[SR-1283] RawRepresentable extension for Self:NSCoding breaks implicit RawRepresentable implementation for enums

Description

import Foundation

enum Status: Int {
    case Good
    case Bad
}

extension RawRepresentable where Self: NSCoding {
    init?(rawValue: NSData) {
        if let instance = NSKeyedUnarchiver.unarchiveObjectWithData(rawValue) as? Self {
            self = instance
        } else {
            return nil
        }
    }
    
    var rawValue: NSData {
        get {
            return NSKeyedArchiver.archivedDataWithRootObject(self)
        }
    }
}

Contributor guide

Tech stack

swift

Domain

tooling

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.

1-2 days

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.

mostly clear

Prerequisites

Swift genericsRawRepresentableNSCoding

Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.

55

Research direction

The bug is due to an extension on RawRepresentable where Self: NSCoding providing a conflicting initializer and property. The fix likely requires modifying the Swift compiler's type checking to disallow such extensions when they conflict with enum's implicit RawRepresentable conformance. Look into the type checker's handling of conditional conformances and RawRepresentable conformance inference. Check the Swift compiler source, particularly the Sema module. The issue has a label 'StarterBug', which may indicate it has been triaged for beginners and there might be a suggested fix in related discussions.