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[Stdlib] Fix swift_setAtWritableKeyPath to check for ReferenceWritableKeyPaths. #34729

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Merged
merged 1 commit into from
Nov 13, 2020
Merged

[Stdlib] Fix swift_setAtWritableKeyPath to check for ReferenceWritableKeyPaths. #34729

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6 changes: 6 additions & 0 deletions stdlib/public/core/KeyPath.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -1920,6 +1920,12 @@ func _setAtWritableKeyPath<Root, Value>(
keyPath: WritableKeyPath<Root, Value>,
value: __owned Value
) {
if type(of: keyPath).kind == .reference {
return _setAtReferenceWritableKeyPath(root: root,
keyPath: _unsafeUncheckedDowncast(keyPath,
to: ReferenceWritableKeyPath<Root, Value>.self),
value: value)
}
// TODO: we should be able to do this more efficiently than projecting.
let (addr, owner) = keyPath._projectMutableAddress(from: &root)
addr.pointee = value
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15 changes: 15 additions & 0 deletions test/stdlib/KeyPath.swift
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Expand Up @@ -1028,5 +1028,20 @@ keyPath.test("tail allocated c array") {
expectEqual(4, offset)
}

keyPath.test("ReferenceWritableKeyPath statically typed as WritableKeyPath") {
let inner = C<Int>(x: 42, y: nil, z: 43)
var outer = C<C<Int>>(x: 44, y: nil, z: inner)
let keyPath = \C<C<Int>>.z.x
let upcastKeyPath = keyPath as WritableKeyPath

expectEqual(outer[keyPath: keyPath], 42)
outer[keyPath: keyPath] = 43
expectEqual(outer[keyPath: keyPath], 43)

expectEqual(outer[keyPath: upcastKeyPath], 43)
outer[keyPath: upcastKeyPath] = 44
expectEqual(outer[keyPath: upcastKeyPath], 44)
}

runAllTests()