[5.9🍒] prevent reinitialization of self after discard #66352
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his instruction is a marker for a following destroy instruction to suppress the call of the move-only type's deinitializer.
…eeded by a drop_deinit rdar://105798769
…ry-picked yet." This reverts commit 22a9c77.
As part of SE-390, you're required to write either: - `consume self` - pass self as a `consuming` parameter to a function - `discard self` before the function ends in a context that contains a `discard self` somewhere. This prevents people from accidentally invoking the deinit due to implicit destruction of `self` before exiting the function. rdar://106099027 (cherry picked from commit 88d35a0)
The value `self` is mutable (i.e., var-bound) in a `consuming` method. Since you're allowed to reinitialize a var after consuming, that means you were also naturally allowed to reinitialize self after `discard self`. But that capability was not intended; after you discard self you shouldn't be reinitializing it, as that's probably a mistake. This change makes reinitialization of `self` reachable from a `discard self` statement an error. rdar://106098163 (cherry picked from commit bd253c6)
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I rebased this on top of #65449 since it depends on those changes. Only the last commit is new. |
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@swift-ci please test |
gottesmm
approved these changes
Jun 6, 2023
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@swift-ci clean test macOS platform |
tbkka
approved these changes
Jun 6, 2023
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• Description: Adds a missing piece of SE-390 where we want to prevent reinitialization of
selfafter discarding it, since it doesn't make sense to permit that and can limit our ability to implementdiscardmore generally in the future.• Risk: Medium. Will introduce a source break in functions that are using discard self and reinitialize self at some point reachable afterwards. (see test/SILOptimizer/discard_checking.swift for examples). The set of programs using discard is probably quite small currently and we'd want to introduce this change early, though the error could be downgraded into a warning for 5.9 upon request.
• Original PR: #66351
• Reviewed By: @gottesmm
• Testing: regression tests included
• Resolves: rdar://106098163