Type inference issue when constraining on a union type

[thedmitriyk]

Compiler version

3.0.0-RC3

Minimized code

sealed trait Base { def str: String }
case class One(str: String) extends Base
case class Two(str: String) extends Base
case class Three(str: String) extends Base

case class Item(_id: String)

private def doWithItem[T <: (One | Two | Three)](item: Item, value: T, action: (T) => Item) = doWithItemId(item._id, value, action)
private def doWithItemId[T <: (One | Two | Three)](itemId: String, value: T, action: (T) => Item) = { println(value.str); Item("_id") }

Output

Compile error:

Found:    (action : T => Item)
Required: T² => Item

where:    T  is a type in method doWithItem with bounds <: One | Two | Three
          T² is a type variable with constraint >: (value : T) and <: One | Two | Three

Expectation

The expectation is not having a compile error. If you reduce the ADT to just One and Two and constrain T on (One | Two), it works.

Scastie: https://scastie.scala-lang.org/SAjrgcaoRS2fn7iyDhJnzg