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[SR-4706] Name lookup in nested scopes is too restrictive #47283

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dabrahams opened this issue Apr 26, 2017 · 7 comments
Open

[SR-4706] Name lookup in nested scopes is too restrictive #47283

dabrahams opened this issue Apr 26, 2017 · 7 comments
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compiler The Swift compiler in itself improvement

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@dabrahams
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Previous ID SR-4706
Radar rdar://problem/31838975
Original Reporter @dabrahams
Type Improvement
Additional Detail from JIRA
Votes 1
Component/s Compiler
Labels Improvement
Assignee None
Priority Medium

md5: 145ae74568a9818327c3395ef2066493

is duplicated by:

  • SR-9056 Nested type not in scope in own extension
  • SR-12315 Extension of nested type does not have access to types it is nested in

relates to:

  • SR-3834 Extensions of nested types are in wrong namespace

Issue Description:

This is annoying, and makes nesting less useful than it should be:

enum X {
  struct Y {}
  struct Z {}
}
extension X.Z {
  typealias A = Y // error: use of undeclared type 'Y'
}

we ought to make Y visible without qualification in X.

Not sure if this is formally a defect, but I consider it to be at least a usability bug.
@dabrahams
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@swift-ci create

@slavapestov
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Should all members of X be visible inside the extension as well, or only Y?

@dabrahams
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All non-instance members should be visible. What could make Y special?

Here's another example, just to show how regressive it is:

extension Unicode.DefaultScalarView.Index : Comparable {
  static func < (lhs: Index, rhs: Index) -> Bool { return lhs < rhs } // error: use of undeclared type 'Index'
  static func == (lhs: Index, rhs: Index) -> Bool { return lhs == rhs }
}

The smallest version I could get it to eat was:

extension Unicode.DefaultScalarView.Index : Comparable {
  static func < (
    lhs: Unicode.DefaultScalarView<CodeUnits,Encoding>.Index,
    rhs: Unicode.DefaultScalarView<CodeUnits,Encoding>.Index
  ) -> Bool { return lhs < rhs }
  
  static func == (
    lhs: Unicode.DefaultScalarView<CodeUnits,Encoding>.Index,
    rhs: Unicode.DefaultScalarView<CodeUnits,Encoding>.Index
  ) -> Bool { return lhs == rhs }
}

@slavapestov
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If you use master, then you should be able to write Unicode.DefaultScalarView.Index

@slavapestov
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I agree it's verbose though. I'll see if we can change the name lookup rules.

@dabrahams
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— If you use master, then you should be able to write Unicode.DefaultScalarView.Index

That must be a recent change, because I'm very close to master

@slavapestov
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Yes, it's pretty recent.

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