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[SR-7776] Misleading 'flatMap is unavailable' diagnostic on Sequence #50315

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AnthonyLatsis opened this issue May 25, 2018 · 3 comments
Closed

[SR-7776] Misleading 'flatMap is unavailable' diagnostic on Sequence #50315

AnthonyLatsis opened this issue May 25, 2018 · 3 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

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@AnthonyLatsis
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Previous ID SR-7776
Radar None
Original Reporter @AnthonyLatsis
Type Bug
Status Closed
Resolution Done

Attachment: Download

Environment

Version 9.3 (9E145)

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

md5: c214929280d7ffbae26c384ba79d8054

Issue Description:

The last two examples should show ambiguous reference and optionally generic parameter could not be inferred. Maybe a logic imperfection related to @available? (One of the flatMap methods is deprecated).

protocol P { // test
  associatedtype Element

  func foo<U>(_ arg: (Element) throws -> U) rethrows -> [U.Element] where U: P
  func foo<U>(_ arg: (Element) throws -> U?) rethrows -> [U]
}

func g<T: P>( arg: T) {
  arg.foo // Ambiguous reference to member 'foo' (OK)
}

func g<T: Sequence>( arg: T) {
  arg.flatMap // 'flatMap' is unavailable
}
[1, 2, 3].enumerated().flatMap // 'flatMap' is unavailable
@belkadan
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I see it in near-master, so maybe it's fixed?

@AnthonyLatsis
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By the way, I am getting this note

note: 'flatMap' was obsoleted in Swift 4
@inlinable public func flatMap(_ transform: (Self.Element) throws -> String) rethrows -> [String]

Was the 'String' flatMap really on Sequence before? This would explain the compiler actually resolving flatMap as a reference to an obsoleted method. The diagnostic then makes sense...but only with the note attached and containing the method's full signature, which isn't shown.

In addition, Xcode doesn't show inline notes, which often makes errors senseless like here.
![](Screen Shot 2018-05-26 at 4.48.17 PM.png)

@AnthonyLatsis
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This diagnoses fine in Xcode 11.0

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
This issue was closed.
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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
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@belkadan @AnthonyLatsis