[5.9🍒] _forget usage fixes to match SE-390
#65743
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we decided against allowing it for now. rdar://108877261 (cherry picked from commit 7ac3ea0)
rdar://108877261 (cherry picked from commit 4943beb)
We haven't quite got the semantics we want implemented for `discard` aka `_forget` statements. Allowing people to use `_forget` in noncopyable types that have stored properties that require destruction will not let us implement it the way we'd like in the future without source break. But, if the type only has "trivial" stored properties with a no-op destruction, like `Int`, then we can still provide utility for users like FileDescriptor who just want to disable the deinit and have nothing fancy stored in the type itself. rdar://108877261 (cherry picked from commit 578da49)
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@swift-ci please test |
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SE-0390 also renamed it to |
airspeedswift
approved these changes
May 6, 2023
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yes the discard change will be a separate PR. |
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• Description: A bundle of changes to usages of the
_forgetstatement to match SE-390. See the commits for details but the TLDR is: (1) emit an error if_forgetis in an initializer, as it was being permitted there in addition to consuming methods; (2) emit an error if_forgetis used in a type with no deinit, since there's no reason to use_forgetat all; (3) require only "trivially destructed" storage in a type with a_forget, since we don't yet have the semantics we want implemented if you have storage that requires destruction.• Risk: Low-ish. Could lead to source breaks that are trivial to fix for (1) and (2); just define a
consuming func forget() { _forget self }if you used it in an initializer. For (3) it's a harder but necessary source break that is better to make now than later. It shouldn't affect early adopters that I'm aware of.• Original PR: #65690
• Reviewed By: @airspeedswift
• Testing: regression tests included
• Resolves: rdar://108877261