Branch :
quote fn (x) { x }
quote fn (x, _y) { x }
quote fn ([x | _y]) { x }
quote fn {
([]) { :error }
([x | _y]) { x }
(_) { :error }
}
fn (x) { x }
fn (x, _y) { x }
fn ([x | _y]) { x }
fn {
([]) { :error }
([x | _y]) { x }
(_) { :error }
}