Scala 3 Pattern Matching on Unions

unionMatch.worksheet.sc

type Primitive = Boolean | Int | Float | Double | Long | String

val x: Int = 1
// x: Int = 1
val y: String = "i"
// y: String = i
val z: Double = 1.0
// z: Double = 1.0

def primitiveMatch(x: Primitive) =
  x match
    case b: Boolean => println("Boolean")
    case b: (Int | Float | Double | Long)  => println("Numeric")
    case b: String  => println("String")

primitiveMatch(x)
// Numeric
primitiveMatch(y)
// String
primitiveMatch(z)
// Numeric

case class A()
case class B(val x: Int)
case class C()

val a: A = A()
// a: A = A()
val bOrC: (B | C) = B(2)
// bOrC: B | C = B(2)

def classMatch(x: (A | B | C)) =
  x match
    case a: A => println("A")
    case B(_) | C() => println("B or C")

classMatch(a)
// A
classMatch(bOrC)
// B or C