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[SR-14287] Dictionary(uniqueKeysWithValues:) cannot accept KeyValuePairs #56646

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rnapier opened this issue Feb 28, 2021 · 2 comments
Open

[SR-14287] Dictionary(uniqueKeysWithValues:) cannot accept KeyValuePairs #56646

rnapier opened this issue Feb 28, 2021 · 2 comments
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself type checker Area → compiler: Semantic analysis

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@rnapier
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rnapier commented Feb 28, 2021

Previous ID SR-14287
Radar rdar://problem/74876070
Original Reporter @rnapier
Type Bug
Environment

Xcode 12.5 beta 2

Swift version 5.4 (swiftlang-1205.0.24.6 clang-1205.0.19.54).

Additional Detail from JIRA
Votes 1
Component/s Compiler
Labels Bug, TypeChecker
Assignee None
Priority Medium

md5: 16f594c0f1d796dd9c1e8bdb575f6220

Issue Description:

KeyValuesPairs is a Sequence whose Element is (key: Key, value: Value). It should be acceptable to Dictionary(uniqueKeysWithValues). Arrays with the same Element are acceptable.

let ps1: [(key: Int, value: String)] = [(1, "1"), (2, "2")]
let ps2: KeyValuePairs<Int, String> = [1: "1", 2: "2"]


type(of: ps1).Element == type(of: ps2).Element // true


let d1 = Dictionary(uniqueKeysWithValues: ps1)
let d2 = Dictionary<Int, String>(uniqueKeysWithValues: ps2) // Initializer 'init(uniqueKeysWithValues:)' requires the types 'KeyValuePairs<Int, String>.Element' (aka '(key: Int, value: String)') and '(Int, String)' be equivalent

This feels like an error in the type checker rather than an error in stdlib.
@typesanitizer
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@swift-ci create

@lorentey
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lorentey commented Mar 6, 2021

I suspect the error might be by design here; if so, the pragmatic thing here is probably to add an overload for `uniqueKeysWithValues:`. (Perhaps this can be considered a bugfix, rather than something that needs a proposal.)

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself type checker Area → compiler: Semantic analysis
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@rnapier @lorentey @typesanitizer