Add {-# OPTIONS_GHC -w #-} and some blurb to all compiler modules

[ghc-hetmet.git] / compiler / basicTypes / NewDemand.lhs

diff --git a/compiler/basicTypes/NewDemand.lhs b/compiler/basicTypes/NewDemand.lhs
index 6da4c47..0ca93ea 100644 (file)
--- a/compiler/basicTypes/NewDemand.lhs
+++ b/compiler/basicTypes/NewDemand.lhs
@@ -5,6 +5,13 @@
 \section[Demand]{@Demand@: the amount of demand on a value}
 
 \begin{code}
+{-# OPTIONS_GHC -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/WorkingConventions#Warnings
+-- for details
+
 module NewDemand(
        Demand(..), 
        topDmd, lazyDmd, seqDmd, evalDmd, errDmd, isStrictDmd, 
@@ -80,7 +87,13 @@ zipWithDmds :: (Demand -> Demand -> Demand)
 zipWithDmds f (Poly d1)  (Poly d2)  = Poly (d1 `f` d2)
 zipWithDmds f (Prod ds1) (Poly d2)  = Prod [d1 `f` d2 | d1 <- ds1]
 zipWithDmds f (Poly d1)  (Prod ds2) = Prod [d1 `f` d2 | d2 <- ds2]
-zipWithDmds f (Prod ds1) (Prod ds2) = Prod (zipWithEqual "zipWithDmds" f ds1 ds2)
+zipWithDmds f (Prod ds1) (Prod ds2) 
+  | length ds1 == length ds2 = Prod (zipWithEqual "zipWithDmds" f ds1 ds2)
+  | otherwise               = Poly topDmd
+       -- This really can happen with polymorphism
+       -- \f. case f x of (a,b) -> ...
+       --     case f y of (a,b,c) -> ...
+       -- Here the two demands on f are C(LL) and C(LLL)!
 
 topDmd, lazyDmd, seqDmd :: Demand
 topDmd  = Top                  -- The most uninformative demand