E4119

Compiler diagnostic name: unknown_func_labelled_arg.

This function is not a toplevel function, so it cannot have labelled arguments.

Only toplevel functions can declare or receive labelled arguments. Local functions are inferred as ordinary function values, so a call such as g(x~) is rejected when g is a local function parameter.

Erroneous example

fn init {
  let x = 42
  fn f(g) {
    g(x~)
  //^
  // Error: This function is not a toplevel function, so it cannot have labelled arguments.
  }
  f(h)
}

fn h(x : Int) -> Unit {
  ignore(x)
}

Suggestion

Pass the value positionally when calling a local function value, or move the function to the toplevel if you need labelled arguments.

fn init {
  let x = 42
  fn f(g) {
    g(x)
  }
  f(h)
}

fn h(x : Int) -> Unit {
  ignore(x)
}