[ConstraintSystem] Enforce TVO_CanBindToPack, and diagnose pack references outside of pack expansion expressions.
#64498
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hborla
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xedin,
AnthonyLatsis and
slavapestov
as code owners
…ences outside of pack expansion expressions.
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@swift-ci please smoke test |
hborla
commented
Mar 21, 2023
| @@ -5317,8 +5317,9 @@ ERROR(expansion_not_allowed,none, | |||
| ERROR(expansion_not_variadic,none, | |||
| "pack expansion %0 must contain at least one pack reference", (Type)) | |||
| ERROR(pack_reference_outside_expansion,none, | |||
| "pack reference %0 can only appear in pack expansion or generic requirement", | |||
| (Type)) | |||
| "pack reference %0 can only appear in pack expansion " | |||
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I'm not a fan of this error message, bike-shedding is welcome!
xedin
approved these changes
Mar 21, 2023
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@swift-ci please smoke test macOS |
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This changes catches the mistake of referencing a value pack without any keywords or with
eachoutside of a pack expansion expression:This is done by enforcing
TVO_CanBindToPackwhen binding a type variable to a fixed type. If the binding is aPackTypeor aPackArchetypeType, solving the constraint will either fail, or apply a constraint fix in diagnostic mode for the invalid pack reference. During CSGen, type variables for decl refs and unresolved dot refs will be marked asTVO_CanBindToPackif there is an enclosing pack expansion expression.This subsumes #61777