merge GHC HEAD

[ghc-hetmet.git] / compiler / deSugar / DsBinds.lhs

diff --git a/compiler/deSugar/DsBinds.lhs b/compiler/deSugar/DsBinds.lhs
index 57c7482..65cb815 100644 (file)
--- a/compiler/deSugar/DsBinds.lhs
+++ b/compiler/deSugar/DsBinds.lhs
@@ -11,7 +11,7 @@ lower levels it is preserved with @let@/@letrec@s).
 
 \begin{code}
 module DsBinds ( dsTopLHsBinds, dsLHsBinds, decomposeRuleLhs, dsSpec,
-                 dsHsWrapper, dsTcEvBinds, dsEvBinds, wrapDsEvBinds,
+                dsHsWrapper, dsTcEvBinds, dsEvBinds, wrapDsEvBinds, 
                 DsEvBind(..), AutoScc(..)
   ) where
 
@@ -36,6 +36,7 @@ import Digraph
 
 import TcType
 import Type
+import Coercion
 import TysPrim  ( anyTypeOfKind )
 import CostCentre
 import Module
@@ -230,8 +231,8 @@ dsEvBinds bs = return (map dsEvGroup sccs)
 
     free_vars_of :: EvTerm -> [EvVar]
     free_vars_of (EvId v)           = [v]
-    free_vars_of (EvCast v co)      = v : varSetElems (tyVarsOfType co)
-    free_vars_of (EvCoercion co)    = varSetElems (tyVarsOfType co)
+    free_vars_of (EvCast v co)      = v : varSetElems (tyCoVarsOfCo co)
+    free_vars_of (EvCoercion co)    = varSetElems (tyCoVarsOfCo co)
     free_vars_of (EvDFunApp _ _ vs) = vs
     free_vars_of (EvSuperClass d _) = [d]
 
@@ -247,7 +248,7 @@ dsEvGroup (AcyclicSCC (EvBind co_var (EvSuperClass dict n)))
     (arg_tys, _) = splitFunTys rho
     bndrs = ex_tvs ++ map mk_wild_pred (theta `zip` [0..])
                    ++ map mkWildValBinder arg_tys
-    mk_wild_pred (p, i) | i==n      = ASSERT( p `tcEqPred` (coVarPred co_var)) 
+    mk_wild_pred (p, i) | i==n      = ASSERT( p `eqPred` (coVarPred co_var)) 
                                       co_var
                         | otherwise = mkWildEvBinder p
     
@@ -263,7 +264,7 @@ dsEvTerm :: EvTerm -> CoreExpr
 dsEvTerm (EvId v)                = Var v
 dsEvTerm (EvCast v co)           = Cast (Var v) co
 dsEvTerm (EvDFunApp df tys vars) = Var df `mkTyApps` tys `mkVarApps` vars
-dsEvTerm (EvCoercion co)         = Type co
+dsEvTerm (EvCoercion co)         = Coercion co
 dsEvTerm (EvSuperClass d n)
   = ASSERT( isClassPred (classSCTheta cls !! n) )
            -- We can only select *dictionary* superclasses
@@ -526,13 +527,14 @@ dsSpec mb_poly_rhs (L loc (SpecPrag poly_id spec_co spec_inl))
   where
     is_local_id = isJust mb_poly_rhs
     poly_rhs | Just rhs <-  mb_poly_rhs
-             = rhs
-             | Just unfolding <- maybeUnfoldingTemplate (idUnfolding poly_id)
-             = unfolding
+             = rhs         -- Local Id; this is its rhs
+             | Just unfolding <- maybeUnfoldingTemplate (realIdUnfolding poly_id)
+             = unfolding    -- Imported Id; this is its unfolding
+                           -- Use realIdUnfolding so we get the unfolding 
+                           -- even when it is a loop breaker. 
+                           -- We want to specialise recursive functions!
              | otherwise = pprPanic "dsImpSpecs" (ppr poly_id)
-       -- In the Nothing case the specialisation is for an imported Id
-       -- whose unfolding gives the RHS to be specialised
-        -- The type checker has checked that it has an unfolding
+                           -- The type checker has checked that it *has* an unfolding
 
 specUnfolding :: (CoreExpr -> CoreExpr) -> Type 
               -> Unfolding -> DsM (Unfolding, OrdList (Id,CoreExpr))
@@ -596,17 +598,13 @@ decomposeRuleLhs bndrs lhs
 
    bad_shape_msg = hang (ptext (sLit "RULE left-hand side too complicated to desugar"))
                       2 (ppr opt_lhs)
-   dead_msg bndr = hang (ptext (sLit "Forall'd") <+> pp_bndr bndr
-                                <+> ptext (sLit "is not bound in RULE lhs"))
+   dead_msg bndr = hang (sep [ ptext (sLit "Forall'd") <+> pp_bndr bndr
+                            , ptext (sLit "is not bound in RULE lhs")])
                       2 (ppr opt_lhs)
    pp_bndr bndr
-    | isTyVar bndr = ptext (sLit "type variable") <+> ppr bndr
-    | isCoVar bndr = ptext (sLit "coercion variable") <+> ppr bndr
-    | isDictId bndr = ptext (sLit "constraint") <+> ppr (get_pred bndr)
-    | otherwise     = ptext (sLit "variable") <+> ppr bndr
-
-   get_pred b = ASSERT( isId b ) expectJust "decomposeRuleLhs" 
-                                 (tcSplitPredTy_maybe (idType b))
+    | isTyVar bndr  = ptext (sLit "type variable") <+> quotes (ppr bndr)
+    | isEvVar bndr  = ptext (sLit "constraint") <+> quotes (ppr (evVarPred bndr))
+    | otherwise     = ptext (sLit "variable") <+> quotes (ppr bndr)
 \end{code}
 
 Note [Simplifying the left-hand side of a RULE]
@@ -633,7 +631,6 @@ otherwise we don't match when given an argument like
 NB: tcSimplifyRuleLhs is very careful not to generate complicated
     dictionary expressions that we might have to match
 
-
 Note [Matching seqId]
 ~~~~~~~~~~~~~~~~~~~
 The desugarer turns (seq e r) into (case e of _ -> r), via a special-case hack