Fix forward capture analysis #25831
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Fix forward capture analysis #25831
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slavapestov
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@swift-ci Please test source compatibility |
Sema does not have enough information to diagnose these problems correctly. Also, there was an unimplemented case in the analysis; if a closure did not yet have computed captures, we'd add it to the ForwardCapturedFuncs list, but nothing ever looked at that list.
…cation Otherwise we can't produce good diagnostics pointing at the right 'defer' block.
This will be used to emit diagnostics in SILGen when a value is captured before being defined.
This was the only case where getDeclCaptureKind() would return CaptureKind::None, and we can simplify some code by not handling that case.
The new analysis simply checks if the captured value has been defined yet; instead of asserting if it hasn't, we can now emit a diagnostic using the source location tracked in the capture list. Fixes <https://bugs.swift.org/browse/SR-4812>, <rdar://problem/40600800>.
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Sema had some logic to diagnose closures that captured values before their definition point. The analysis was wrong, and a false negative meant that SILGen would hit an assertion when trying to emit a capture of an undefined value.
Instead, let's just change SILGen to diagnose the invalid capture if it sees an undefined value while emitting captures, defining away the crash completely. This requires better tracking of source locations when building capture lists, but is otherwise simpler.
Fixes https://bugs.swift.org/browse/SR-4812, rdar://problem/40600800.