vlib/v/checker/tests/array_map_anon_fn_err_b.vv:2:21: error: type mismatch, should use `fn(a int) T {...}`
    1 | fn main() {
    2 |     a := [1,2,3,4].map(fn(a string) string { return a })
      |                        ~~
    3 |     println(a)
    4 | }
