[Sema] Improve handling of fallthrough in if/switch expressions
#75891
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Make it clear the issue is the transfer of control flow out of the `if`/`switch` expression. Technically things like `break` and `continue` are allowed, as long as they are not jumping out of the expression.
I don't think this currently matters, but ensure we re-contextualize BreakStmts and ContinueStmts in RecontextualizeClosures since these statements store DeclContexts.
Follow a similar pattern to BreakTargetRequest and ContinueTargetRequest.
Allow `fallthrough` to appear as the last statement in the case of a `switch` expression. We already allowed it in other positions, this was just an oversight. rdar://127670432
Impose the same limit we impose on other forms of control flow statements (e.g `break`, `continue`, `return`), where it cannot transfer control out of the expression. This fixes a crash where we'd fail to find a fallthrough nested in an `if` expression. It is technically source breaking, as we would have allowed the case where the `if` expression is a directly nested result of an outer `switch` expression, but I would be very surprised if anyone is relying on that. rdar://133845101
hamishknight
requested review from
hborla,
xedin,
slavapestov,
jckarter,
ahoppen,
bnbarham,
CodaFi,
DougGregor and
rintaro
as code owners
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@swift-ci please test |
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@swift-ci please test source compatibility |
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@swift-ci please test |
xedin
approved these changes
Aug 19, 2024
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Remove the restriction on
fallthroughas the last statement in aswitchexpression, and prevent fallthrough from jumping out ofifexpressions.rdar://127670432
rdar://133845101
Resolves #75880