vectoriser: take class directly from the instance tycon

diff --git a/compiler/vectorise/Vectorise/Type/PADict.hs b/compiler/vectorise/Vectorise/Type/PADict.hs
index 8b6ad92..a15f671 100644 (file)
--- a/compiler/vectorise/Vectorise/Type/PADict.hs
+++ b/compiler/vectorise/Vectorise/Type/PADict.hs
@@ -53,21 +53,12 @@ buildPADict vect_tc prepr_tc arr_tc repr
                $ Type inst_ty : map (method_call args) method_ids
 
       -- Build the type of the dictionary function.
-      pa_tc          <- builtin paTyCon
-      let pa_opitems = [(id, NoDefMeth) | id <- method_ids]
-      let pa_cls     = mkClass 
-                       (tyConName pa_tc)
-                       tvs             -- tyvars of class
-                       []              -- fundeps
-                       []              -- superclass predicates
-                       0               -- number of equalities
-                       []              -- superclass dict selectors
-                       []              -- associated type families
-                       pa_opitems      -- class op items
-                       pa_tc           -- dictionary type constructor
-                       
-      let dfun_ty = mkForAllTys tvs
-                  $ mkFunTys (map varType args) (PredTy $ ClassP pa_cls [inst_ty])
+      pa_tc            <- builtin paTyCon
+      let pa_opitems   = [(id, NoDefMeth) | id <- method_ids]
+      let Just pa_cls  = tyConClass_maybe pa_tc
+
+      let dfun_ty      = mkForAllTys tvs
+                       $ mkFunTys (map varType args) (PredTy $ ClassP pa_cls [inst_ty])
 
       -- Set the unfolding for the inliner.
       raw_dfun <- newExportedVar dfun_name dfun_ty