Minor refactoring

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

diff --git a/compiler/deSugar/DsExpr.lhs b/compiler/deSugar/DsExpr.lhs
index 2512ddd..11fddf5 100644 (file)
--- a/compiler/deSugar/DsExpr.lhs
+++ b/compiler/deSugar/DsExpr.lhs
@@ -43,12 +43,15 @@ import Type
 import Coercion
 import CoreSyn
 import CoreUtils
+import CoreFVs
 import MkCore
 
 import DynFlags
 import StaticFlags
 import CostCentre
 import Id
+import Var
+import VarSet
 import PrelInfo
 import DataCon
 import TysWiredIn
@@ -208,7 +211,9 @@ dsExpr (HsVar var)                = return (Var var)
 dsExpr (HsIPVar ip)                  = return (Var (ipNameName ip))
 dsExpr (HsLit lit)                   = dsLit lit
 dsExpr (HsOverLit lit)               = dsOverLit lit
-dsExpr (HsWrap co_fn e)       = dsCoercion co_fn (dsExpr e)
+dsExpr (HsWrap co_fn e)       = do { co_fn' <- dsCoercion co_fn
+                                   ; e' <- dsExpr e
+                                   ; return (co_fn' e') }
 
 dsExpr (NegApp expr neg_expr) 
   = App <$> dsExpr neg_expr <*> dsLExpr expr
@@ -643,23 +648,30 @@ makes all list literals be generated via the simple route.
 
 
 \begin{code}
-
 dsExplicitList :: PostTcType -> [LHsExpr Id] -> DsM CoreExpr
 -- See Note [Desugaring explicit lists]
-dsExplicitList elt_ty xs = do
-    dflags <- getDOptsDs
-    xs' <- mapM dsLExpr xs
-    if  opt_SimpleListLiterals || not (dopt Opt_EnableRewriteRules dflags)
-        then return $ mkListExpr elt_ty xs'
-        else mkBuildExpr elt_ty (mkSplitExplicitList (thisPackage dflags) xs')
+dsExplicitList elt_ty xs
+  = do { dflags <- getDOptsDs
+       ; xs' <- mapM dsLExpr xs
+       ; let (dynamic_prefix, static_suffix) = spanTail is_static xs'
+       ; if opt_SimpleListLiterals                     -- -fsimple-list-literals
+         || not (dopt Opt_EnableRewriteRules dflags)   -- Rewrite rules off
+         || null dynamic_prefix   -- Avoid build (\c n. foldr c n xs)!
+         then return $ mkListExpr elt_ty xs'
+         else mkBuildExpr elt_ty (mkSplitExplicitList dynamic_prefix static_suffix) }
   where
-    mkSplitExplicitList this_package xs' (c, _) (n, n_ty) = do
-        let (dynamic_prefix, static_suffix) = spanTail (rhsIsStatic this_package) xs'
-            static_suffix' = mkListExpr elt_ty static_suffix
-        
-        folded_static_suffix <- mkFoldrExpr elt_ty n_ty (Var c) (Var n) static_suffix'
-        let build_body = foldr (App . App (Var c)) folded_static_suffix dynamic_prefix
-        return build_body
+    is_static :: CoreExpr -> Bool
+    is_static e = all is_static_var (varSetElems (exprFreeVars e))
+
+    is_static_var :: Var -> Bool
+    is_static_var v 
+      | isId v = isExternalName (idName v)  -- Top-level things are given external names
+      | otherwise = False                   -- Type variables
+
+    mkSplitExplicitList prefix suffix (c, _) (n, n_ty)
+      = do { let suffix' = mkListExpr elt_ty suffix
+           ; folded_suffix <- mkFoldrExpr elt_ty n_ty (Var c) (Var n) suffix'
+           ; return (foldr (App . App (Var c)) folded_suffix prefix) }
 
 spanTail :: (a -> Bool) -> [a] -> ([a], [a])
 spanTail f xs = (reverse rejected, reverse satisfying)
@@ -737,8 +749,7 @@ dsDo stmts body result_ty
         body       = noLoc $ HsDo DoExpr rec_stmts return_app body_ty
         return_app = nlHsApp (noLoc return_op) (mkLHsTupleExpr rets)
        body_ty    = mkAppTy m_ty tup_ty
-        tup_ty     = mkCoreTupTy (map idType tup_ids)
-                  -- mkCoreTupTy deals with singleton case
+        tup_ty     = mkBoxedTupleTy (map idType tup_ids) -- Deals with singleton case
 
     -- In a do expression, pattern-match failure just calls
     -- the monadic 'fail' rather than throwing an exception
@@ -836,8 +847,7 @@ dsMDo tbl stmts body result_ty
        mfix_pat = noLoc $ LazyPat $ mk_tup_pat rec_tup_pats
        body     = noLoc $ HsDo ctxt rec_stmts return_app body_ty
        body_ty = mkAppTy m_ty tup_ty
-       tup_ty  = mkCoreTupTy (map idType (later_ids' ++ rec_ids))
-                 -- mkCoreTupTy deals with singleton case
+       tup_ty  = mkBoxedTupleTy (map idType (later_ids' ++ rec_ids))  -- Deals with singleton case
 
        return_app  = nlHsApp (nlHsTyApp return_id [tup_ty]) 
                              (mkLHsTupleExpr rets)