vlib/v/checker/tests/auto_deref_assign_err.vv:10:6: error: cannot assign to `o`: expected `&int`, not `string`
    8 | fn sub( mut o &int ) {
    9 |     println( 'in function got: ' + o.str() )
   10 |     o = "mutate int as string??"
      |         ~~~~~~~~~~~~~~~~~~~~~~~~
   11 | }
