In an AbsBinds, the 'dicts' can include EqInsts

An AbsBinds abstrats over evidence, and the evidence can be both
Dicts (class constraints, implicit parameters) and EqInsts (equality
constraints).  So we need to
  - use varType rather than idType
  - use instToVar rather than instToId
  - use zonkDictBndr rather than zonkIdBndr in zonking

It actually all worked before, but gave warnings.

diff --git a/compiler/typecheck/TcBinds.lhs b/compiler/typecheck/TcBinds.lhs
index ba4bfc6..f27637d 100644 (file)
--- a/compiler/typecheck/TcBinds.lhs
+++ b/compiler/typecheck/TcBinds.lhs
@@ -42,7 +42,7 @@ import VarEnv
 import TysPrim
 import Id
 import IdInfo
-import Var ( TyVar )
+import Var ( TyVar, varType )
 import Name
 import NameSet
 import NameEnv
@@ -344,15 +344,15 @@ tcPolyBinds top_lvl sig_fn prag_fn rec_group rec_tc binds
           generalise dflags top_lvl bind_list sig_fn mono_bind_infos lie_req
 
        -- BUILD THE POLYMORPHIC RESULT IDs
-  ; let dict_ids = map instToId dicts
-  ; exports <- mapM (mkExport top_lvl prag_fn tyvars_to_gen (map idType dict_ids))
+  ; let dict_vars = map instToVar dicts        -- May include equality constraints
+  ; exports <- mapM (mkExport top_lvl prag_fn tyvars_to_gen (map varType dict_vars))
                    mono_bind_infos
 
   ; let        poly_ids = [poly_id | (_, poly_id, _, _) <- exports]
   ; traceTc (text "binding:" <+> ppr (poly_ids `zip` map idType poly_ids))
 
   ; let abs_bind = L loc $ AbsBinds tyvars_to_gen
-                                   dict_ids exports
+                                   dict_vars exports
                                    (dict_binds `unionBags` binds')
 
   ; return ([unitBag abs_bind], poly_ids)      -- poly_ids are guaranteed zonked by mkExport

diff --git a/compiler/typecheck/TcHsSyn.lhs b/compiler/typecheck/TcHsSyn.lhs
index 075ae71..f9b390f 100644 (file)
--- a/compiler/typecheck/TcHsSyn.lhs
+++ b/compiler/typecheck/TcHsSyn.lhs
@@ -194,6 +194,13 @@ zonkIdBndr env id
 zonkIdBndrs :: ZonkEnv -> [TcId] -> TcM [Id]
 zonkIdBndrs env ids = mappM (zonkIdBndr env) ids
 
+zonkDictBndrs :: ZonkEnv -> [Var] -> TcM [Var]
+-- "Dictionary" binders can be coercion variables or dictionary variables
+zonkDictBndrs env ids = mappM (zonkDictBndr env) ids
+
+zonkDictBndr env var | isTyVar var = return var
+                    | otherwise   = zonkIdBndr env var
+
 zonkTopBndrs :: [TcId] -> TcM [Id]
 zonkTopBndrs ids = zonkIdBndrs emptyZonkEnv ids
 \end{code}
@@ -287,7 +294,7 @@ zonk_bind env bind@(FunBind { fun_id = var, fun_matches = ms, fun_co_fn = co_fn
 zonk_bind env (AbsBinds { abs_tvs = tyvars, abs_dicts = dicts, 
                          abs_exports = exports, abs_binds = val_binds })
   = ASSERT( all isImmutableTyVar tyvars )
-    zonkIdBndrs env dicts              `thenM` \ new_dicts ->
+    zonkDictBndrs env dicts                    `thenM` \ new_dicts ->
     fixM (\ ~(new_val_binds, _) ->
        let
          env1 = extendZonkEnv env new_dicts

diff --git a/compiler/typecheck/TcInstDcls.lhs b/compiler/typecheck/TcInstDcls.lhs
index 5d1e63a..0025ef2 100644 (file)
--- a/compiler/typecheck/TcInstDcls.lhs
+++ b/compiler/typecheck/TcInstDcls.lhs
@@ -525,7 +525,7 @@ tcInstDecl2 (InstInfo { iSpec = ispec, iBinds = NewTypeDerived })
        ; let dict_bind = noLoc $ VarBind (instToId this_dict) (noLoc body)
 
        ; return (unitBag $ noLoc $
-                 AbsBinds  tvs (map instToId dfun_dicts)
+                 AbsBinds  tvs (map instToVar dfun_dicts)
                            [(tvs, dfun_id, instToId this_dict, [])] 
                            (dict_bind `consBag` sc_binds)) }
   where

diff --git a/compiler/typecheck/TcSimplify.lhs b/compiler/typecheck/TcSimplify.lhs
index f5bdc51..0516308 100644 (file)
--- a/compiler/typecheck/TcSimplify.lhs
+++ b/compiler/typecheck/TcSimplify.lhs
@@ -950,8 +950,10 @@ bindIrredsR loc qtvs co_vars reft givens irreds
   | null irreds
   = return emptyBag
   | otherwise
-  = do { let givens' = filter isDict givens
-               -- The givens can include methods
+  = do { let givens' = filter isAbstractableInst givens
+               -- The givens can (redundantly) include methods
+               -- We want to retain both EqInsts and Dicts
+               -- There should be no implicadtion constraints
                -- See Note [Pruning the givens in an implication constraint]
 
           -- If there are no 'givens' *and* the refinement is empty
@@ -987,7 +989,8 @@ makeImplicationBind :: InstLoc -> [TcTyVar] -> Refinement
 --
 -- This binding must line up the 'rhs' in reduceImplication
 makeImplicationBind loc all_tvs reft
-                   givens      -- Guaranteed all Dicts (TOMDO: true?)
+                   givens      -- Guaranteed all Dicts
+                               -- or EqInsts
                    irreds
  | null irreds                 -- If there are no irreds, we are done
  = return ([], emptyBag)