+-- We distinguish primitive coercions
+-- (represented in GHC by wired-in names), because
+-- External Core treats them specially, so we have
+-- to print them out with special syntax.
+ | TransCoercion Ty Ty
+ | SymCoercion Ty
+ | UnsafeCoercion Ty Ty
+ | InstCoercion Ty Ty
+ | LeftCoercion Ty
+ | RightCoercion Ty