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[SR-5184] Confusing diagnostics with an escaping closure #47760

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swift-ci opened this issue Jun 10, 2017 · 2 comments
Open

[SR-5184] Confusing diagnostics with an escaping closure #47760

swift-ci opened this issue Jun 10, 2017 · 2 comments
Labels
bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself diagnostics QoI Bug: Diagnostics Quality of Implementation type checker Area → compiler: Semantic analysis

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@swift-ci
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Previous ID SR-5184
Radar rdar://32711708
Original Reporter vytis (JIRA User)
Type Bug
Environment

Xcode 9.0 beta (9M136h) with default Swift toolchain

Additional Detail from JIRA
Votes 0
Component/s Compiler
Labels Bug, DiagnosticsQoI, TypeChecker
Assignee None
Priority Medium

md5: cec240dd4da017b9119a7c2b4a41bcbe

is duplicated by:

  • SR-8499 Useless error message without @escaping when closure types conversion is failed

Issue Description:

Having a closure in a tuple produces a confusing diagnostic message on assignment.

Example:

typealias ObserverCallback = () -> ()
typealias Observer = (limit: Int, callback: ObserverCallback)

var observer: Observer?

func addObserver(limit: Int, callback: ObserverCallback) {
    observer = (limit: limit, callback: callback)
}

Produces the diagnostic:

error: Circlone.playground:5:16: error: cannot assign value of type '(limit: Int, callback: () -> ())' to type 'Observer?' (aka 'Optional<(limit: Int, callback: () -> ())>')
    observer = (limit: limit, callback: callback)
               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
                                                  as! Observer

When the actual reason is that we need to add `@escaping` to a closure parameter:

func addObserver(limit: Int, callback: @escaping ObserverCallback)
@belkadan
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cc @milseman, @xedin

@milseman
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Mannequin

milseman mannequin commented Jun 12, 2017

Likely related to SR-2657

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
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Labels
bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself diagnostics QoI Bug: Diagnostics Quality of Implementation type checker Area → compiler: Semantic analysis
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@belkadan @swift-ci