Support Structural Refinements

[Jamie Thompson]

[2 days]

class Structural1[M <: { val output: Int } ] {
  import reflect.Selectable.reflectiveSelectable
  def get(m: M): Int = m.output
}

class Structural2[M <: { def output: Int } ] {
  import reflect.Selectable.reflectiveSelectable
  def get(m: M): Int = m.output
}

class Structural3[M <: { def encode(t: Int): String } ] {
  import reflect.Selectable.reflectiveSelectable
  def encodeWith(m: M, t: Int): String = m.encode(t)
}

class StructuralSelectable[M <: Selectable { def encode(t: Int): String } ] {
  def encodeWith(m: M, t: Int): String = m.encode(t)
}

class StructuralFlip1 {
  import reflect.Selectable.reflectiveSelectable
  def get[M <: { val output: Int } ](m: M): Int = m.output
}

class StructuralFlip2 {
  import reflect.Selectable.reflectiveSelectable
  def get[M <: { def output: Int } ](m: M): Int = m.output
}

class StructuralFlip3 {
  import reflect.Selectable.reflectiveSelectable
  def encodeWith[M <: { def encode(t: Int): String } ](m: M, t: Int): String = m.encode(t)
}

class StructuralSelectableFlip {
  def encodeWith[M <: Selectable { def encode(t: Int): String } ](m: M, t: Int): String = m.encode(t)
}

Structural refinement callsites and bounds on scala.Selectable are treated specially in Dotty, so there is an open question to how to support them if approved.