vlib/v/checker/tests/append_err.vv:3:7: error: cannot append `string` to `[]int`
    1 | fn main() {
    2 |     mut l := []int{}
    3 |     l << 'test'
      |          ~~~~~~
    4 |     
    5 |     _ = l << 3
vlib/v/checker/tests/append_err.vv:5:8: error: array append cannot be used in an expression
    3 |     l << 'test'
    4 |     
    5 |     _ = l << 3
      |           ~~
    6 |     _ = (l << 3).len
    7 | }
vlib/v/checker/tests/append_err.vv:6:9: error: array append cannot be used in an expression
    4 |     
    5 |     _ = l << 3
    6 |     _ = (l << 3).len
      |            ~~
    7 | }