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[stdlib] Preserve random-access Mirror.children inside AnyCollection #33319

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[stdlib] Preserve random-access Mirror.children inside AnyCollection #33319

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7 changes: 6 additions & 1 deletion stdlib/public/core/Mirror.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -137,7 +137,12 @@ public struct Mirror {

/// A collection of `Child` elements describing the structure of the
/// reflected subject.
public var children: Children { AnyCollection(_children) }
public var children: Children {
switch _children {
case let .left(l): return AnyCollection(l)
case let .right(r): return AnyCollection(r)
}
}

/// A suggested display style for the reflected subject.
public let displayStyle: DisplayStyle?
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19 changes: 19 additions & 0 deletions test/stdlib/Mirror.swift
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Expand Up @@ -150,6 +150,25 @@ mirrors.test("LabeledStructure") {
expectEqual("[bark: 1, bite: Zee]", h.testDescription)
}

mirrors.test("ErasedChildren") {
let m1 = Mirror(reflecting: 1..<4)
let c1 = AnyRandomAccessCollection(m1.children)
expectNotNil(c1)
expectNil(c1?.first?.label)
expectTrue(c1?.first?.label as? Int == 1)
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Shouldn't this be expectTrue(c1?.first?.value as? Int == 1)?

expectNil(c1?.last?.label)
expectTrue(c1?.last?.value as? Int == 3)

struct Foo { let i = 42; let s = "bar" }
let m2 = Mirror(reflecting: Foo())
let c2 = AnyRandomAccessCollection(m2.children)
expectNotNil(c2)
expectTrue(c2?.first?.label == "i")
expectTrue(c2?.first?.label as? Int == 42)
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Shouldn't this be expectTrue(c2?.first?.value as? Int == 42)?

expectTrue(c2?.last?.label == "s")
expectTrue(c2?.last?.value as? String == "bar")
}

mirrors.test("Legacy") {
let m = Mirror(reflecting: [1, 2, 3])
expectTrue(m.subjectType == [Int].self)
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