--- /dev/null
+base_isa_gen4.nit:34,8--15: Warning: Expression is already a A since it is a B[Canard].
+base_isa_gen4.nit:36,8--22: Warning: Expression is already a B[Animal] since it is a B[Canard].
+base_isa_gen4.nit:40,8--24: Warning: Expression is already a B[B[Canard]].
+base_isa_gen4.nit:42,8--24: Warning: Expression is already a B[B[Animal]] since it is a B[B[Canard]].
+true