Forwarding force unwrap 6.0 #73545
Forwarding force unwrap 6.0 #73545
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| fatalError("bah!") // expected-error {{must consume 'self' before exiting method that discards self}} | ||
| return // expected-error {{must consume 'self' before exiting method that discards self}} |
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Curious why you needed to change these tests? I assume this fix revealed a bug in pruned liveness that the discard checking relied on w.r.t. unreachable blocks?
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These tests appear to previously be testing that an unreachable call like fatalError is treated as a function exit, which is wrong—fatalError never returns, and so the calling function is never really exited either. I needed to fix this because every force-unwrap introduces a branch with a trap and unreachable on the nil path, and if move checking tries to treat this as an exit, it will try to insert cleanups on the unreachable branch, which may not be valid because other cleanups on dependent accesses might still be active and we don't generally try to clean up on crash paths.
Since these tests are still exercising interesting combinations of control flow, I changed them to have a real function return instead of a trap so that the tests still provide coverage.
Like `?` or property access, `x!` can be borrowing, consuming, or mutated through depending on the use site and the ownership of the base value. Alter SILGen to emit `x!` as a borrowing operation when the result is only used as a borrow. Fix the move-only checker not to treat the unreachable branch as a dead path for values and try to destroy the value unnecessarily and possibly out-of-order with cleanups on the value. Fixes rdar://127459955.
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(includes #73411 as a prerequisite)
Explanation: Changes the handling of the
x!force unwrap operator onOptionalto be any of borrowing, consuming, or mutating based on the use of the unwrapped value.Scope: Noncopyable stdlib adoption work.
Issue: rdar://127459955
Original PR: #73531
Risk: Low. The change only affects the
!operator and should be a safe extension of its behavior for noncopyable Optionals.Testing: Swift CI, test case from bug report
Reviewer: @kavon