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[SR-9014] Pattern matching doesn't work for overloaded enum cases #51517

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swift-ci opened this issue Oct 16, 2018 · 3 comments
Open

[SR-9014] Pattern matching doesn't work for overloaded enum cases #51517

swift-ci opened this issue Oct 16, 2018 · 3 comments
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compiler The Swift compiler in itself

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@swift-ci
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Previous ID SR-9014
Radar None
Original Reporter aaargh! (JIRA User)
Type Sub-task
Environment

Swift 4.1 Playground in Xcode 10.0 (10A254a) on macOS 10.14 (18A391)

Additional Detail from JIRA
Votes 1
Component/s Compiler
Labels Sub-task
Assignee None
Priority Medium

md5: bea00aad8d9891b0317e78ea34c47706

Parent-Task:

Issue Description:

When overloading enum cases with labelled associated values, pattern matching only works for the last case defined with the same base name.

Minimal test-case:

public enum Result {
    case Succes
    case NonFatalError(message: String)
    case NonFatalError(messages: [String])
    case FatalError
}


var test1:Result = .NonFatalError(message: "line1")
var test2:Result = .NonFatalError(messages: ["line1", "line2"])


if case .NonFatalError(let message) = test1 {
    print("message: \(message)")
}


if case .NonFatalError(let messages) = test2 {
    print("message: \(messages)")
}

Only the second pattern matches.

When I reverse the order of the two NonFatalError cases, only the first if-case matches.

Expected behaviour: either the enum should not compile, or the pattern matching should work.
@belkadan
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You didn't put a label in your pattern-match: case .NonFatalError(messages: let messages). This should probably complain about being ambiguous, though. cc CodaFi (JIRA User)

@swift-ci
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swift-ci commented Jan 9, 2019

Comment by Nikola Lajic (JIRA)

@belkadan I ran into the same issue today. Your suggestion throws another unrelated error. In addition to that, a non-exhaustive warning is not shown for the switch.

import UIKit


enum Result {
    case finished(error: Error)
    case finished(response: String)
}


var a: Result = .finished(response: "A")


switch a {
case .finished(let response): // type is string
    print(response)
    // missing warning for non exhaustive switch
}


switch a {
case .finished(response: let response):
    print(response)
case .finished(error: let error): // error: tuple pattern element label 'error' must be 'response'
    print(error)
}

@belkadan
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belkadan commented Jan 9, 2019

I think we just haven't finished implementing SE-0155.

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
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@belkadan @swift-ci