Cannot find method IndexedSeqView.updated when running a program compiled with CC stdlib

[Linyxus]

Compiler version

main

Minimized code

object Hello extends App {
    println(Vector(1, 2, 3).view.updated(1, 8))
}

Steps to reproduce (assuming that the code is saved as Hello.scala):

sbt> set ThisBuild/Build.scala2Library := Build.Scala2LibraryCCTasty
sbt> scala3-bootstrapped/scalac Hello.scala
sbt> scala3-bootstrapped/scala Hello

Output

Exception in thread "main" java.lang.NoSuchMethodError: 'scala.collection.View scala.collection.IndexedSeqView.updated(int, java.lang.Object)'
	at Hello$.<clinit>(Hello.scala:2)
	at Hello.main(Hello.scala)

Expectation

It should run.

[odersky]

I think it's because at runtime we use the normal stdlib, where there is no updated in IndexedSeqView. Can you try to make the updated that we added an inline method?

[nicolasstucki]

This is the difference in the bytecode

  44: invokestatic  #54                 // Method scala/runtime/BoxesRunTime.boxToInteger:(I)Ljava/lang/Integer;
- 47: invokeinterface #60,  3           // InterfaceMethod scala/collection/IndexedSeqView.updated:(ILjava/lang/Object;)Ljava/lang/Object;
+ 47: invokeinterface #60,  3           // InterfaceMethod scala/collection/IndexedSeqView.updated:(ILjava/lang/Object;)Lscala/collection/View;
  52: invokevirtual #64                 // Method scala/Predef$.println:(Ljava/lang/Object;)V

[odersky]

Which is which?

[nicolasstucki]

The one that returns a View is using the CC library. That signature corresponds to the addition new override added in https://github.com/lampepfl/dotty/pull/19798/files#diff-1557066ce6e57518a7fa5d6138de6a2a431ecc6baf30fcf1e423c73cf99b340eR51

Inlining it seems to work (#19824). It is not an ideal solution as it will duplicate the implementation of updated at each call site.

[odersky]

Or maybe we can massage the return type by going through some abstract type. E.g.

type C[T] <: T
def updated(...): C[View]

Would that work?

[Linyxus]

Or maybe we can massage the return type by going through some abstract type. E.g.

type C[T] <: T
def updated(...): C[View]

Would that work?

We have to say type C[T] >: T <: T to make it typecheck. I tried and it didn't work.

I attempted another fix here. Do you think that is a good idea?

[odersky]

Not ure it will work, but it's worth a try!

[Linyxus]

I confirm that it works. So maybe we could use this scheme for other methods that need to be added as well?