vlib/v/checker/tests/array_map_fn_err_b.vv:5:20: error: type mismatch, should use `fn(a int) int {...}`
    3 | }
    4 | fn main() {
    5 |     a := [1,2,3,4].map(add)
      |                       ~~~~~
    6 |     println(a)
    7 | }
