[SILGen]: Emit ignored loads of uninhabited lvalues to address DI edge cases #85381
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@swift-ci smoke test macos |
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@swift-ci please test source compatibility |
…e cases
Previously we would crash on this pattern:
```swift
let x: Never
switch x {}
```
This appears to be due to the fact that the switch over the uninhabited
value did not result in any instructions DI considers a use being
produced. This change adds special handling of this case so that we
now emit a load of the value so DI correctly diagnoses the use before
init.
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@swift-ci please test |
jamieQ
commented
Nov 8, 2025
| // Failure to do this in the past resulted in this bug: | ||
| // https://github.com/swiftlang/swift/issues/74478. | ||
|
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| emitLoadOfLValue(E, std::move(lv), SGFContext::AllowImmediatePlusZero); |
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could someone verify if it matters what SGFContext value is used here? i assume this case should always result in a downstream error so i'm inclined to think it doesn't...
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Previously we would crash (at runtime) on this pattern:
This appears to be due to the fact that the switch over the uninhabited value did not result in any instructions DI considers a use being produced. This change adds special handling of this case so that we now emit a load of the value so DI correctly diagnoses the use before init.
Resolves: #74478