Compile-time error on Scala 3

[sergeda]

This code produce compile-time error:

enum Subcommand:
    case IndexFile(file: Path)

val fileArg = Args.file("path-to-file", Exists.Yes) ?? "Path to the file"
val command = Command(name = "index-file", args = fileArg)
    .withHelp("Index file")
    .map{ path => Subcommand.IndexFile(path)}

Version is 0.4.0 , Scala is 3.3.0-RC2
Here is the error:

[error] java.lang.AssertionError: assertion failed: `wildApprox` failed to remove uninstantiated A
[error] scala.runtime.Scala3RunTime$.assertFailed(Scala3RunTime.scala:8)

[jdegoes]

/bounty $50

[algora-pbc]

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[andrzejressel]

I couldn't reproduce it (I believe the supplied code snippet is not enough), but I believe it's this :scala/scala3#17305. I believe it's something on Dotty side, I'll see if I can minimize it.

EDIT: The good thing is that is means something is wrong with your code - so I guess If you find it you don't have to wait for new Dotty version.

[pragmaxim]

This error seems to happen in case of any compilation error related to the syntax needed in the DSL, so it is indeed a dotty bug, just go line by line or comment out blocks of code and find the real compilation error to get rid of it.