[Smaug123]

F# also has:

  let foo : obj = failwith ""

  match foo with
  | :? SomeType as blah ->
      // use blah : SomeType

(You're allowed to just use the identifier `foo` in the match arm.)

[halfmatthalfcat]

As does Scala:

  match thing {
    case a: String => 
      // use a as string
    case a @ MyCaseClass(b: String, c, d) =>
      // use a as the instance of MyCaseClass or use b as a string
  }