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[stdlib] Dictionary.updateValue(_:,forKey:): Don’t overwrite the existing key #19592

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Merged
merged 1 commit into from
Sep 27, 2018
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[stdlib] Dictionary.updateValue(_:,forKey:): Don’t overwrite the existing key #19592

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8 changes: 0 additions & 8 deletions stdlib/public/core/NativeDictionary.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -416,10 +416,6 @@ extension _NativeDictionary { // Insertions
if found {
let oldValue = (_values + bucket.offset).move()
(_values + bucket.offset).initialize(to: value)
// FIXME: Replacing the old key with the new is unnecessary, unintuitive,
// and actively harmful to some usecases. We shouldn't do it.
// rdar://problem/32144087
(_keys + bucket.offset).pointee = key
return oldValue
}
_insert(at: bucket, key: key, value: value)
Expand All @@ -435,10 +431,6 @@ extension _NativeDictionary { // Insertions
let (bucket, found) = mutatingFind(key, isUnique: isUnique)
if found {
(_values + bucket.offset).pointee = value
// FIXME: Replacing the old key with the new is unnecessary, unintuitive,
// and actively harmful to some usecases. We shouldn't do it.
// rdar://problem/32144087
(_keys + bucket.offset).pointee = key
} else {
_insert(at: bucket, key: key, value: value)
}
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28 changes: 27 additions & 1 deletion validation-test/stdlib/Dictionary.swift
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Expand Up @@ -411,7 +411,7 @@ DictionaryTestSuite.test("COW.Fast.UpdateValueForKeyDoesNotReallocate") {
}
}

DictionaryTestSuite.test("COW.Slow.AddDoesNotReallocate") {
DictionaryTestSuite.test("COW.Slow.UpdateValueForKeyDoesNotReallocate") {
do {
var d1 = getCOWSlowDictionary()
let identity1 = d1._rawIdentifier()
Expand Down Expand Up @@ -4642,6 +4642,32 @@ DictionaryTestSuite.test("removeAt") {
}
}

DictionaryTestSuite.test("updateValue") {
let key1 = TestKeyTy(42)
let key2 = TestKeyTy(42)
let value1 = TestValueTy(1)
let value2 = TestValueTy(2)

var d: [TestKeyTy: TestValueTy] = [:]

expectNil(d.updateValue(value1, forKey: key1))

expectEqual(d.count, 1)
let index1 = d.index(forKey: key2)
expectNotNil(index1)
expectTrue(d[index1!].key === key1)
expectTrue(d[index1!].value === value1)

expectTrue(d.updateValue(value2, forKey: key2) === value1)

expectEqual(d.count, 1)
let index2 = d.index(forKey: key2)
expectEqual(index1, index2)
// We expect updateValue to keep the original key in place.
expectTrue(d[index2!].key === key1) // Not key2
expectTrue(d[index2!].value === value2)
}

DictionaryTestSuite.test("localHashSeeds") {
// With global hashing, copying elements in hash order between hash tables
// can become quadratic. (See https://bugs.swift.org/browse/SR-3268)
Expand Down