Fix #2770: Tighten type compatibility checks for overrides #2886
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- We now require strict subtypes if owning classes are in a subclass relationship. Nonempty bounds good enough only if classes are unrelated. - We treat class types correctly by eta-expanding their types. - We do kind checking on types. Previously, some illegal things slipped through because of the way Any works. In fact a hk type like `[X] => Any` is a subtype of `Any` according to TypeComparer. But kind checking should prevent us from making that comparison in the first place.
Special provisions need to be made if the type argument is a wildcard or of type Nothing.
smarter
approved these changes
Jul 19, 2017
| def memberTp(self: Type) = | ||
| if (member.isClass) TypeAlias(member.typeRef.EtaExpand(member.typeParams)) | ||
| else self.memberInfo(member) | ||
| def otherTp(self: Type) = self.memberInfo(other) |
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Why isn't other eta-expanded like member?
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Other cannot be a class anyway. Classes cannot be overridden.
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a subclass relationship. Nonempty bounds good enough only
if classes are unrelated.
Previously, some illegal things slipped through because of the way Any works.
In fact a hk type like
[X] => Anyis a subtype ofAnyaccording toTypeComparer. But kind checking should prevent us from making that
comparison in the first place.