base_isa_nullable2.nit:27,8--23: Warning: expression is already a `nullable A` since it is a `A`.
base_isa_nullable2.nit:29,8--31: Warning: expression is already a `nullable B[Object]` since it is a `B[Object]`.
base_isa_nullable2.nit:30,8--40: Warning: expression is already a `nullable B[nullable Object]` since it is a `B[Object]`.
base_isa_nullable2.nit:33,8--31: Warning: expression is already a `C[nullable Object]`.
true