vlib/v/checker/tests/assign_expr_type_err_i.vv:3:9: error: invalid right operand: f64 += string
    1 | fn main() {
    2 |     mut foo := 1.5
    3 |     foo += 'hello'
      |            ~~~~~~~
    4 |     _ = foo
    5 | }
vlib/v/checker/tests/assign_expr_type_err_i.vv:3:9: error: cannot assign to `foo`: expected `f64`, not `string`
    1 | fn main() {
    2 |     mut foo := 1.5
    3 |     foo += 'hello'
      |            ~~~~~~~
    4 |     _ = foo
    5 | }
