"children of trait were already queried before class was discovered" due to match type used #17132
Description
Compiler version
3.2.2
Minimized code
sealed trait Transformation[T]
case object Count extends Transformation[Int]
case class MultiTransformation[T1 <: Transformation[?], T2 <: Transformation[?]](t1: T1, t2: T2)
extends Transformation[MultiTransformationResult[T1, T2]]
type MultiTransformationResult[T1 <: Transformation[?], T2 <: Transformation[?]] <: Tuple = (T1, T2) match {
case (Transformation[t], MultiTransformation[t1, t2]) => t *: MultiTransformationResult[t1, t2]
case (Transformation[t1], Transformation[t2]) => (t1, t2)
}Output
children of trait Transformation were already queried before class MultiTransformation was discovered.
As a remedy, you could move class MultiTransformation on the same nesting level as trait Transformation.Expectation
The code should either compile or the compiler should display a valid error message. In this case the error message is misleading as both trait and class already are on the same nesting level.