A question about roles.

Hello I have noticed in looking at some core that GADT type constructors are often applied with a representational role. These constructors are explicitly marked as nominal. Is this information just ignored at a Core level or is this invalid core? Looking at the code a see that we if we downgrade a TyConAppCo we unconditionally change it to a representational role after changing its children. I think this is where it is introduced. Alex ET