SIL: Detect and bail out on infinite aggregates. #41111
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Sema diagnoses obvious cases of value types defined in terms of themselves, but it can't catch cases that arise as a result of generic substitution, such as if a generic struct has a field of associated type that becomes the same as the struct type itself. SIL may end up handling these types, even though they can't be instantiated (the runtime will complain and crash if the metadata is requested), either during SILGen because they were written in source code, or as a result of generic specialization during optimization. SIL thus can't rely on diagnostics preventing such types from appearing, so it needs to be able to continue gracefully when they show up. Add checks in type lowering for when a struct or enum lowering ends up depending on itself, and generate an infinite type lowering that's opaque and address-only. Fixes rdar://80310017
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@swift-ci Please test |
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Sema diagnoses obvious cases of value types defined in terms of themselves,
but it can't catch cases that arise as a result of generic substitution,
such as if a generic struct has a field of associated type that becomes the
same as the struct type itself. SIL may end up handling these types, even
though they can't be instantiated (the runtime will complain and crash if
the metadata is requested), either during SILGen because they were written
in source code, or as a result of generic specialization during optimization.
SIL thus can't rely on diagnostics preventing such types from appearing, so
it needs to be able to continue gracefully when they show up. Add checks
in type lowering for when a struct or enum lowering ends up depending on
itself, and generate an infinite type lowering that's opaque and address-only.
Fixes rdar://80310017