extension (x: Int) def plus(y: Int) = x + y

extension [T](x: T) def f = ()

extension (x: Int)
  def f = 1
  def f = 2

object Foo {
  extension (x: Int)
    def f = 1
    def f = 2
}

def extension(file: File) =
  file.extension

  file
    .extension