From a17d329568660592dad5c7668fb09f31ab77cd69 Mon Sep 17 00:00:00 2001
From: "simonpj@microsoft.com" <unknown>
Date: Tue, 13 Jan 2009 16:48:04 +0000
Subject: [PATCH] Rename isIdentityCoercion to isIdentityCoI; add
 Coercion.isIdentityCoercion

---
 compiler/typecheck/TcBinds.lhs |    2 +-
 compiler/typecheck/TcPat.lhs   |    4 ++--
 compiler/types/Coercion.lhs    |   28 +++++++++++++++++-----------
 3 files changed, 20 insertions(+), 14 deletions(-)

diff --git a/compiler/typecheck/TcBinds.lhs b/compiler/typecheck/TcBinds.lhs
index c67eeef..59ae266 100644
--- a/compiler/typecheck/TcBinds.lhs
+++ b/compiler/typecheck/TcBinds.lhs
@@ -812,7 +812,7 @@ unifyCtxts (sig1 : sigs)        -- Argument is always non-empty
                -- where F is a type function and (F a ~ [a])
                -- Then unification might succeed with a coercion.  But it's much
                -- much simpler to require that such signatures have identical contexts
-               checkTc (all isIdentityCoercion cois)
+               checkTc (all isIdentityCoI cois)
                        (ptext (sLit "Mutually dependent functions have syntactically distinct contexts"))
              }
 
diff --git a/compiler/typecheck/TcPat.lhs b/compiler/typecheck/TcPat.lhs
index c6caa54..e21fb68 100644
--- a/compiler/typecheck/TcPat.lhs
+++ b/compiler/typecheck/TcPat.lhs
@@ -427,7 +427,7 @@ tc_pat pstate (orig@(ViewPat expr pat _)) overall_pat_ty thing_inside
 tc_pat pstate (SigPatIn pat sig_ty) pat_ty thing_inside
   = do	{ (inner_ty, tv_binds, coi) <- tcPatSig (patSigCtxt pstate) sig_ty 
                                                                     pat_ty
-        ; unless (isIdentityCoercion coi) $ 
+        ; unless (isIdentityCoI coi) $ 
             failWithTc (badSigPat pat_ty)
 	; (pat', tvs, res) <- tcExtendTyVarEnv2 tv_binds $
 			      tc_lpat pat inner_ty pstate thing_inside
@@ -702,7 +702,7 @@ tcConPat pstate con_span data_con tycon pat_ty arg_pats thing_inside
 	     ; (_, freshTvs, subst) <- tcInstTyVars (tyConTyVars tycon)
              ; let instTys' = substTys subst instTys
 	     ; cois <- boxyUnifyList instTys' scrutinee_arg_tys
-             ; let coi = if isIdentityCoercion coi1
+             ; let coi = if isIdentityCoI coi1
                          then  -- pat_ty was splittable
                                -- => boxyUnifyList had real work to do
                            mkTyConAppCoI fam_tycon instTys' cois
diff --git a/compiler/types/Coercion.lhs b/compiler/types/Coercion.lhs
index b247a3f..eda45a3 100644
--- a/compiler/types/Coercion.lhs
+++ b/compiler/types/Coercion.lhs
@@ -22,7 +22,7 @@ module Coercion (
         Coercion,
  
         mkCoKind, mkReflCoKind, splitCoercionKind_maybe, splitCoercionKind,
-        coercionKind, coercionKinds, coercionKindPredTy,
+        coercionKind, coercionKinds, coercionKindPredTy, isIdentityCoercion,
 
 	-- ** Equality predicates
 	isEqPred, mkEqPred, getEqPredTys, isEqPredTy,  
@@ -46,7 +46,7 @@ module Coercion (
 
 	-- * CoercionI
 	CoercionI(..),
-	isIdentityCoercion,
+	isIdentityCoI,
 	mkSymCoI, mkTransCoI, 
 	mkTyConAppCoI, mkAppTyCoI, mkFunTyCoI,
 	mkForAllTyCoI,
@@ -184,6 +184,12 @@ coercionKinds :: [Coercion] -> ([Type], [Type])
 coercionKinds tys = unzip $ map coercionKind tys
 
 -------------------------------------
+isIdentityCoercion :: Coercion -> Bool
+isIdentityCoercion co  
+  = case coercionKind co of
+       (t1,t2) -> t1 `coreEqType` t2
+
+-------------------------------------
 -- Coercion kind and type mk's
 -- (make saturated TyConApp CoercionTyCon{...} args)
 
@@ -580,13 +586,13 @@ instance Outputable CoercionI where
   ppr IdCo     = ptext (sLit "IdCo")
   ppr (ACo co) = ppr co
 
-isIdentityCoercion :: CoercionI -> Bool
-isIdentityCoercion IdCo = True
-isIdentityCoercion _    = False
+isIdentityCoI :: CoercionI -> Bool
+isIdentityCoI IdCo = True
+isIdentityCoI _    = False
 
 -- | Tests whether all the given 'CoercionI's represent the identity coercion
-allIdCos :: [CoercionI] -> Bool
-allIdCos = all isIdentityCoercion
+allIdCoIs :: [CoercionI] -> Bool
+allIdCoIs = all isIdentityCoI
 
 -- | For each 'CoercionI' in the input list, return either the 'Coercion' it
 -- contains or the corresponding 'Type' from the other list
@@ -615,8 +621,8 @@ mkTransCoI (ACo co1) (ACo co2) = ACo $ mkTransCoercion co1 co2
 -- | Smart constructor for type constructor application on 'CoercionI', see also 'mkAppCoercion'
 mkTyConAppCoI :: TyCon -> [Type] -> [CoercionI] -> CoercionI
 mkTyConAppCoI tyCon tys cois
-  | allIdCos cois = IdCo
-  | otherwise	  = ACo (TyConApp tyCon (zipCoArgs cois tys))
+  | allIdCoIs cois = IdCo
+  | otherwise	   = ACo (TyConApp tyCon (zipCoArgs cois tys))
 
 -- | Smart constructor for honest-to-god 'Coercion' application on 'CoercionI', see also 'mkAppCoercion'
 mkAppTyCoI :: Type -> CoercionI -> Type -> CoercionI -> CoercionI
@@ -645,8 +651,8 @@ fromACo (ACo co) = co
 -- > mkClassPPredCoI cls tys cois :: PredTy (cls tys) ~ PredTy (cls (tys `cast` cois))
 mkClassPPredCoI :: Class -> [Type] -> [CoercionI] -> CoercionI
 mkClassPPredCoI cls tys cois 
-  | allIdCos cois = IdCo
-  | otherwise     = ACo $ PredTy $ ClassP cls (zipCoArgs cois tys)
+  | allIdCoIs cois = IdCo
+  | otherwise      = ACo $ PredTy $ ClassP cls (zipCoArgs cois tys)
 
 -- | Smart constructor for implicit parameter 'Coercion's on 'CoercionI'. Similar to 'mkClassPPredCoI'
 mkIParamPredCoI :: (IPName Name) -> CoercionI -> CoercionI 
-- 
1.7.10.4