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Make SwiftValue hash/equality work the same as SwiftObject #69618

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Merged
merged 2 commits into from
Nov 7, 2023
Merged

Make SwiftValue hash/equality work the same as SwiftObject #69618

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2cbd70e
Make SwiftValue hash/equality work the same as SwiftObject
tbkka Nov 2, 2023
5ba38e8
Comment out a known-broken test case
tbkka Nov 4, 2023
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42 changes: 36 additions & 6 deletions stdlib/public/runtime/SwiftValue.mm
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Original file line number Diff line number Diff line change
Expand Up @@ -29,13 +29,15 @@
#include "swift/Runtime/Metadata.h"
#include "swift/Runtime/ObjCBridge.h"
#include "swift/Runtime/Debug.h"
#include "swift/Threading/Mutex.h"
#include "Private.h"
#include "SwiftEquatableSupport.h"
#include "SwiftHashableSupport.h"
#include <objc/runtime.h>
#include <Foundation/Foundation.h>

#include <new>
#include <unordered_set>

using namespace swift;
using namespace swift::hashable_support;
Expand Down Expand Up @@ -446,15 +448,43 @@ - (BOOL)isEqual:(id)other {
}

- (NSUInteger)hash {
// If Swift type is Hashable, get the hash value from there
auto selfHeader = getSwiftValueHeader(self);
auto hashableConformance = selfHeader->getHashableConformance();
if (!hashableConformance) {
return (NSUInteger)self;
if (hashableConformance) {
return _swift_stdlib_Hashable_hashValue_indirect(
getSwiftValuePayload(self,
getSwiftValuePayloadAlignMask(selfHeader->type)),
selfHeader->type, hashableConformance);
}
return _swift_stdlib_Hashable_hashValue_indirect(
getSwiftValuePayload(self,
getSwiftValuePayloadAlignMask(selfHeader->type)),
selfHeader->type, hashableConformance);

// If Swift type is Equatable but not Hashable,
// we have to return something here that is compatible
// with the `isEqual:` above.
auto equatableConformance = selfHeader->getEquatableConformance();
if (equatableConformance) {
// Warn once per type about this
auto metadata = getSwiftValueTypeMetadata(self);
static Lazy<std::unordered_set<const Metadata *>> warned;
static LazyMutex warnedLock;
LazyMutex::ScopedLock guard(warnedLock);
auto result = warned.get().insert(metadata);
auto inserted = std::get<1>(result);
if (inserted) {
TypeNamePair typeName = swift_getTypeName(metadata, true);
warning(0,
"Obj-C `-hash` invoked on a Swift value of type `%s` that is Equatable but not Hashable; "
"this can lead to severe performance problems.\n",
typeName.data);
}
// Constant value (yuck!) is the only choice here
return (NSUInteger)1;
}

// If the Swift type is neither Equatable nor Hashable,
// then we can hash the identity, which should be pretty
// good in practice.
return (NSUInteger)self;
}

static id getValueDescription(__SwiftValue *self) {
Expand Down
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