def download [--head: oneof<>] {
  let span = $head | default (metadata $head).span
  error make {msg: "a", label: {text: here, span: $span}}
}

def run [--head: oneof<>] { 
  let span = (metadata $head).span
  download --head=$span
}

download
# => Error: nu::shell::error
# => 
# =>   × a
# =>    ╭─[entry #6:1:1]
# =>  1 │ download
# =>    · ────┬───
# =>    ·     ╰── here
# =>    ╰────

run
# => Error: nu::shell::error
# => 
# =>   × a
# =>    ╭─[entry #7:1:1]
# =>  1 │ run
# =>    · ─┬─
# =>    ·  ╰── here
# =>    ╰────

def download [number: oneof<int, record<item: int, span: record>>] {
  let number = match $number {
    {item: $_, span: $_} => $number,
    $val => {item: $number, span: (metadata $number).span}
  }

  error make {msg: "a", label: {text: here, span: $number.span}}
}

def run [number: int] {
  let number = {item: $number, span: (metadata $number).span}
  download $number
}

download 123
# => Error: nu::shell::error
# => 
# =>   × a
# =>    ╭─[entry #9:1:10]
# =>  1 │ download 123
# =>    ·          ─┬─
# =>    ·           ╰── here
# =>    ╰────

run 123
# => Error: nu::shell::error
# => 
# =>   × a
# =>    ╭─[entry #10:1:5]
# =>  1 │ run 123
# =>    ·     ─┬─
# =>    ·      ╰── here
# =>    ╰────