[4.2] Handle unexpected raw values for @objc enums in derived conformances #17881
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…wiftlang#17836) Because people put all sorts of nonsense into @objc enums (most reasonably, "private cases", which represent valid values that are not API), the Swift-synthesized implementation of 'hash(into:)' needs to not expect a switch statement to be exhaustive. And since Swift-defined @objc enums are supposed to behave enough like C-defined enums, they should at least handle simple method calls with an invalid raw value, which means that 'rawValue' likewise should not use a switch. This patch provides alternate implementations that look like this: extension ImportedEnum { public var rawValue: Int { return unsafeBitCast(self, to: Int.self) } public func hash(into hasher: inout Hasher) { hasher.combine(self.rawValue) } } rdar://problem/41913284 (cherry picked from commit 357c7d6)
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Aargh. Guess the simplest fix wasn't enough. |
This check is superfluous in correct code, but necessary in the 4.2 branch to avoid failing in incorrect code. (On master, the error is not reported because the enum is no longer considered @objc at this point.)
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Explanation: Because people put all sorts of nonsense into
@objcenums (most reasonably, "private cases", which represent valid values that are not API), the Swift-synthesized implementation ofhash(into:)needs to not expect a switch statement to be exhaustive. And since Swift-defined@objcenums are supposed to behave enough like C-defined enums, they should at least handle simple method calls with an invalid raw value, which means thatrawValuelikewise should not use a switch. Implementhash(into:)in terms ofrawValueandrawValuein terms ofunsafeBitCast.Scope: Affects
hash(into:)andrawValuefor both imported and user-defined@objcenums.Issue: rdar://problem/41913284
Risk: Medium-low. The code change is very straightforward and we have pretty good test coverage, but it is a broad scope.
Testing: Added compiler regression tests.
Reviewed by: @jckarter, @itaiferber, @slavapestov