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Casting from AnyHashable to AnyHashable should never create another wrapper #36470

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Merged
merged 2 commits into from
Mar 22, 2021
Merged

Casting from AnyHashable to AnyHashable should never create another wrapper #36470

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773c679
Casting from AnyHashable to AnyHashable should never create another w…
tbkka Mar 17, 2021
855b1fb
Move the `Struct AnyHashable` change to `without-asserts` list
tbkka Mar 19, 2021
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7 changes: 7 additions & 0 deletions stdlib/public/core/AnyHashable.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -260,6 +260,13 @@ extension AnyHashable: CustomReflectable {
}
}

@available(macOS 9999, iOS 9999, tvOS 9999, watchOS 9999, *)
extension AnyHashable: _HasCustomAnyHashableRepresentation {
public __consuming func _toCustomAnyHashable() -> AnyHashable? {
return self
}
}

/// Returns a default (non-custom) representation of `self`
/// as `AnyHashable`.
///
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23 changes: 23 additions & 0 deletions test/Casting/Casts.swift
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Expand Up @@ -924,4 +924,27 @@ CastsTests.test("Optional cast to AnyHashable") {
expectNotEqual(xh, yh)
}

// Repeatedly casting to AnyHashable should still test equal.
// (This was broken for a while because repeatedly casting to
// AnyHashable could end up with multiple nested AnyHashables.)
// rdar://75180619
CastsTests.test("Recursive AnyHashable") {
struct P: Hashable {
var x: Int
}
struct S {
var x: AnyHashable?
init<T: Hashable>(_ x: T?) {
self.x = x
}
}
let p = P(x: 0)
let hp = p as AnyHashable?
print(hp.debugDescription)
let s = S(hp)
print(s.x.debugDescription)
expectEqual(s.x, hp)
expectEqual(s.x, p)
}

runAllTests()
1 change: 1 addition & 0 deletions test/api-digester/stability-stdlib-abi-without-asserts.test
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Expand Up @@ -48,6 +48,7 @@ Func Collection.subranges(where:) has been removed
Func MutableCollection.moveSubranges(_:to:) has been removed
Func MutableCollection.removeSubranges(_:) has been removed
Func RangeReplaceableCollection.removeSubranges(_:) has been removed
Struct AnyHashable has added a conformance to an existing protocol _HasCustomAnyHashableRepresentation
Struct DiscontiguousSlice has been removed
Struct RangeSet has been removed
Subscript Collection.subscript(_:) has been removed
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