vlib/v/checker/tests/incorrect_smartcast_err.vv:10:5: notice: smartcasting requires either an immutable value, or an explicit mut keyword before the value
    8 | fn main(){
    9 |     mut example := IExample(Example{field:"test"})
   10 |     if example is Example{
      |        ~~~~~~~
   11 |         println(example.field)
   12 |     }
vlib/v/checker/tests/incorrect_smartcast_err.vv:11:19: error: type `IExample` has no field named `field`
    9 |     mut example := IExample(Example{field:"test"})
   10 |     if example is Example{
   11 |         println(example.field)
      |                         ~~~~~
   12 |     }
   13 | }
