Rethrows in method of struct with a throwing property

Using Swift
9

You might be able to use overloading, as is necessary for your problem when it comes to functions.

It is terrible, yes, but I can't think of a way to avoid copying everything that uses one of the two closure options. I think a generic type is better than two manual concrete types if there's other common functionality that doesn't rely on the closure.

struct Foo<Closure> {
  private let closure: Closure
}

extension Foo where Closure == () -> Void {
  init(_ closure: Closure) {
    self.closure = closure
  }

  func callAsFunction() {
    closure()
  }
}

extension Foo where Closure == () throws -> Void {
  init(_ closure: Closure) {
    self.closure = closure
  }

  func callAsFunction() throws {
    try closure()
  }
}

let foo1 = Foo { print("Foo") }
foo1()

let foo2 = Foo {
  struct Error: Swift.Error { }
  throw Error()
}

do {
  try foo2()
} catch {
  print("Error")
}
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