E4013

This function has a type which expects a different number of arguments than provided.

Erroneous Example

fn f() -> (() -> Int) {
  fn (x: Int) { x }
}

The example above declares a function f returns a function which expects no arguments, but returns a function that expects one argument. This will give the following error on line 2:

This function has type () -> Int, which expects 0 argument(s), but is given 1 argument(s).

Suggestion

Adjust the code so that the number of arguments in the function type matches the number of arguments in the function definition:

///|
pub fn f() -> (Int) -> Int {
  fn(x : Int) { x }
}

... or:

///|
pub fn g(x : Int) -> () -> Int {
  fn() { x }
}