⚠️[ObjectiveC] NSObject: Fix hashing implementation #18006
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NSObject defines its own interface for hashing and equality. Subclasses must implement custom hashing by overriding the hash property, or NSSet and NSDictionary will not work correctly. To prevent a common source of errors, make the hashValue property Swift-only, and non-overridable. (It was declared as @objc open by historical accident.) This is a potentially source-breaking change.
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@swift-ci please test |
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@swift-ci please test source compatibility |
lorentey
changed the title
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Updated and re-submitted as #20129 |
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NSObjectdefines its own interface for hashing and equality. Subclasses must implement custom hashing by overriding the hash property, orNSSetandNSDictionarywill not work correctly.To prevent a common source of errors, make the
hashValueproperty Swift-only, and non-overridable. (It was declared as@objc openby historical accident.)Also add explicit, non-overridable definitions for
hash(into:)and_rawHashValue(seed:)to prevent them from contributing to this issue in the future.This is a potentially source-breaking change. Code that currently overrides
NSObject.hashValueis almost certainly broken (because it violates the NSObject contract). However, this change trades a subtle runtime issue (that the code may or may not actually trigger) with an obvious compilation error.rdar://problem/42623458