void-specialize.swift

func f(code:Void -> Void) {
  print("no throw version called")
  code()
}

func f<Result>(code:Void throws -> Result) rethrows -> Result {
  print("rethrow version called")
  return try code()
}

struct Error : ErrorType {}

func voidReturn1() {
  print("voidReturn1")
}
func voidReturn2() {
  print("voidReturn2")
}
func intReturn(arg:Int) -> Int {
  print("intReturn")
  return arg
}
func voidWithThrow() throws {
  print("voidWithThrow")
  throw Error()
}
func intReturnThrows(arg:Int) throws -> Int {
  print("intReturnThrows")
  throw Error()
}

print("Void return (1 stmt):")
f {
  voidReturn1()
}
print("")

print("Void return (2 stmts):")
f {
  voidReturn1()
  voidReturn2()
}
print("")

print("Int return and not using the result:")
f {
  intReturn(0)
}
print("")

print("Int return and using the result:")
let x = f {
  intReturn(1)
}
print("returned \(x)")
print("")

print("Void throw:")
do {
  try f {
    try voidWithThrow()
  }
} catch let e {
  print("caught \(e)")
}
print("")

print("Int throw:")
do {
  try f {
    try intReturnThrows(2)
  }
} catch let e {
  print("caught \(e)")
}
print("")