adampauls
commented
2 years ago @odersky this comment suggests that this issue might not get fixed. Where can I read up on the workaround using intersection types? In our particular case, the alternative to the code we have is to have type parameter lists that are going to be hundreds of chars long (like T[A <: AbstractA, B <: AbstractB[A], C <: AbstractC[A, B], ...] but where A and B are real class names) repeated in probably a dozen or so places. I'm not sure how to use intersection types to fix the problem. Moreover, note that the compiler crash occurred when trying to use this code from Scala 3, but compiled with 2.13 -- where intersection types are not available.
Perhaps I should focus on minimizing the compiler crash and treating that as the more urgent bug?
odersky
griggt
japgolly
The code below compiles on Scala 2.13.7. Although in this minimized example, the compiler doesn't crash, in the non-minimized use case in our real code, the compiler does crash with the stacktrace shown even lower. I'm not entirely sure if this code should compile in either version, but we have been using it since 2.12 with no trouble.
Note that the compiler crash occurs when code compiled with 3.1.0 depends on the non-minimized version of this code compiled with 2.13.7.
Update: you can workaround the problem where code compiled with Scala 2 is referenced from Scala 3 by overriding the methods in the Scala 2 code with the concrete type. That is, if you have a method
def foo: FooonAbstractBar, if you override it withdef foo: ConcreteFooonConcreteBar, thenfoocan be called on an instance ofConcreteBarfrom Scala 3 without an error.Compiler version
3.1.0
Minimized code
Output (click arrow to expand)