Fix CodingStyle#Warnings URLs

[ghc-hetmet.git] / compiler / simplCore / SimplUtils.lhs

diff --git a/compiler/simplCore/SimplUtils.lhs b/compiler/simplCore/SimplUtils.lhs
index 8acf913..e8714d4 100644 (file)
--- a/compiler/simplCore/SimplUtils.lhs
+++ b/compiler/simplCore/SimplUtils.lhs
@@ -4,6 +4,13 @@
 \section[SimplUtils]{The simplifier utilities}
 
 \begin{code}
+{-# OPTIONS -w #-}
+-- The above warning supression flag is a temporary kludge.
+-- While working on this module you are encouraged to remove it and fix
+-- any warnings in the module. See
+--     http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings
+-- for details
+
 module SimplUtils (
        -- Rebuilding
        mkLam, mkCase, prepareAlts, bindCaseBndr,
@@ -15,7 +22,7 @@ module SimplUtils (
        -- The continuation type
        SimplCont(..), DupFlag(..), LetRhsFlag(..), 
        contIsDupable, contResultType, contIsTrivial, contArgs, dropArgs, 
-       countValArgs, countArgs,
+       countValArgs, countArgs, splitInlineCont,
        mkBoringStop, mkLazyArgStop, mkRhsStop, contIsRhsOrArg,
        interestingCallContext, interestingArgContext,
 
@@ -39,9 +46,11 @@ import CoreUnfold
 import MkId
 import Name
 import Id
+import Var     ( isCoVar )
 import NewDemand
 import SimplMonad
-import Type
+import Type    ( Type, funArgTy, mkForAllTys, mkTyVarTys, 
+                 splitTyConApp_maybe, tyConAppArgs )
 import TyCon
 import DataCon
 import Unify   ( dataConCannotMatch )
@@ -153,10 +162,11 @@ mkLazyArgStop ty has_rules = Stop ty AnArg (canUpdateInPlace ty || has_rules)
 mkRhsStop :: OutType -> SimplCont
 mkRhsStop ty = Stop ty AnRhs (canUpdateInPlace ty)
 
-contIsRhsOrArg (Stop {})       = True
-contIsRhsOrArg (StrictBind {}) = True
-contIsRhsOrArg (StrictArg {})  = True
-contIsRhsOrArg other          = False
+-------------------
+contIsRhsOrArg (Stop {})                = True
+contIsRhsOrArg (StrictBind {})          = True
+contIsRhsOrArg (StrictArg {})           = True
+contIsRhsOrArg other            = False
 
 -------------------
 contIsDupable :: SimplCont -> Bool
@@ -203,6 +213,26 @@ dropArgs :: Int -> SimplCont -> SimplCont
 dropArgs 0 cont = cont
 dropArgs n (ApplyTo _ _ _ cont) = dropArgs (n-1) cont
 dropArgs n other               = pprPanic "dropArgs" (ppr n <+> ppr other)
+
+--------------------
+splitInlineCont :: SimplCont -> Maybe (SimplCont, SimplCont)
+-- Returns Nothing if the continuation should dissolve an InlineMe Note
+-- Return Just (c1,c2) otherwise, 
+--     where c1 is the continuation to put inside the InlineMe 
+--     and   c2 outside
+
+-- Example: (__inline_me__ (/\a. e)) ty
+--     Here we want to do the beta-redex without dissolving the InlineMe
+-- See test simpl017 (and Trac #1627) for a good example of why this is important
+
+splitInlineCont (ApplyTo dup (Type ty) se c)
+  | Just (c1, c2) <- splitInlineCont c                 = Just (ApplyTo dup (Type ty) se c1, c2)
+splitInlineCont cont@(Stop ty _ _)             = Just (mkBoringStop ty, cont)
+splitInlineCont cont@(StrictBind bndr _ _ se _) = Just (mkBoringStop (substTy se (idType bndr)), cont)
+splitInlineCont cont@(StrictArg _ fun_ty _ _)   = Just (mkBoringStop (funArgTy fun_ty), cont)
+splitInlineCont other                          = Nothing
+       -- NB: the calculation of the type for mkBoringStop is an annoying
+       --     duplication of the same calucation in mkDupableCont
 \end{code}
 
 
@@ -1041,8 +1071,11 @@ abstractFloats main_tvs body_env body
                 subst'   = CoreSubst.extendIdSubst subst id poly_app
           ; return (subst', (NonRec poly_id poly_rhs)) }
       where
-       rhs'     = CoreSubst.substExpr subst rhs
-       tvs_here = varSetElems (main_tv_set `intersectVarSet` exprSomeFreeVars isTyVar rhs')
+       rhs' = CoreSubst.substExpr subst rhs
+       tvs_here | any isCoVar main_tvs = main_tvs      -- Note [Abstract over coercions]
+                | otherwise 
+                = varSetElems (main_tv_set `intersectVarSet` exprSomeFreeVars isTyVar rhs')
+       
                -- Abstract only over the type variables free in the rhs
                -- wrt which the new binding is abstracted.  But the naive
                -- approach of abstract wrt the tyvars free in the Id's type
@@ -1101,6 +1134,13 @@ abstractFloats main_tvs body_env body
                -- pinned on x.
 \end{code}
 
+Note [Abstract over coercions]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+If a coercion variable (g :: a ~ Int) is free in the RHS, then so is the
+type variable a.  Rather than sort this mess out, we simply bale out and abstract
+wrt all the type variables if any of them are coercion variables.
+
+
 Historical note: if you use let-bindings instead of a substitution, beware of this:
 
                -- Suppose we start with: