fix object subtype-relation between generic instances #847
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Summary ======= Fix a bug with the subtype-of-generic-object logic that caused generic instances of object-like types to be treated as unrelated when one of their in-between types is a `ref`/`ptr` type while the formal type is not (or vice versa). Refer to the added test for an example of where this issue surfaced. Details ======= The mistake was considering the skipped ptr/ref at each inheritance step, while it must only be considered once for the formal and original actual type. This properly considers `ref` and `ptr` types being used as object base types. In addition to the fix, the documentation of and inside `isSubtypeOfGeneric` is slightly improved.
zerbina
added
bug
saem
reviewed
Aug 18, 2023
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| First = ref object of Root[int] | ||
| Second = object of First |
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no change for this PR. musing outloud really, but I do wonder about this feature... maybe it's ok under the "what else could it be?" although those sorts of things preclude future extension of the language.
saem
approved these changes
Aug 18, 2023
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/merge |
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Merge requested by: @saem Contents after the first section break of the PR description has been removed and preserved below:
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Summary
Fix a bug with the subtype-of-generic-object logic that caused generic
instances of object-like types to be treated as unrelated when one of
their in-between types is a
ref/ptrtype while the formal type isnot (or vice versa). Refer to the added test for an example of where
this issue surfaced.
Details
The mistake was considering the skipped ptr/ref at each inheritance
step, while it must only be considered once for the formal and original
actual type. This properly considers
refandptrtypes being usedas object base types.
In addition to the fix, the documentation of and inside
isSubtypeOfGenericInstanceis slightly improved.