Fix debug_ppr_ty ForAllTy (#18522)
Before this change, GHC would pretty-print forall k. forall a -> ()
as forall @k a. ()
, which isn't even valid Haskell.
Before this change, GHC would pretty-print forall k. forall a -> ()
as forall @k a. ()
, which isn't even valid Haskell.