Fix #6484: Properly unpickle some Scala 2 type lambdas #6494
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Scala 2 pickles both type lambdas and polymorphic methods using the POLYtpe tag. When we unpickle them, we distinguish them based on whether the symbol for the owner of the type parameters is a term or a type, but it seems that some type parameter symbols for type lambdas are pickled with a term owner. In Eff for example, the pickled information for the `runReader` method in: https://github.com/atnos-org/eff/blob/85bd7b2dc1cd26c22e45d69910755f2a9ea4ece4/shared/src/main/scala/org/atnos/eff/syntax/reader.scala#L12 contains a POLYtpe `[A] => A` (because `Reader` is defined in cats as `type Reader[A, B] = Kleisli[Id, A, B]`, and `Id` is defined as `type Id[A] = A`), somehow the owner of the symbol for `A` is the object `reader` defined in the same file. That doesn't make any sense to me, but just checking if the owner is actually a method should work just as well and fixes the problem. Given that Scala 2 unpickling support is a temporary crutch I think that's good enough.
odersky
approved these changes
May 11, 2019
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Scala 2 pickles both type lambdas and polymorphic methods using the
POLYtpe tag. When we unpickle them, we distinguish them based on whether
the symbol for the owner of the type parameters is a term or a type, but
it seems that some type parameter symbols for type lambdas are pickled
with a term owner. In Eff for example, the pickled information for the
runReadermethod in:https://github.com/atnos-org/eff/blob/85bd7b2dc1cd26c22e45d69910755f2a9ea4ece4/shared/src/main/scala/org/atnos/eff/syntax/reader.scala#L12
contains a POLYtpe
[A] => A(becauseReaderis defined in cats astype Reader[A, B] = Kleisli[Id, A, B], andIdis defined astype Id[A] = A), somehow the owner of the symbol forAis theobject
readerdefined in the same file.That doesn't make any sense to me, but just checking if the owner is
actually a method should work just as well and fixes the problem. Given
that Scala 2 unpickling support is a temporary crutch I think that's
good enough.