Make absolutely sure that 'done' and 'safeIndex' are strict in the index

This is just to make sure that there is no redundant boxing.
For safeIndex, for example, the error path doesn't evaluate the
index, so it may be passed boxed unless safeIndex is inlined bodily,
which I don't want to rely on.

1 files changed, 8 insertions, 5 deletions

diff --git a/libraries/base/GHC/Arr.lhs b/libraries/base/GHC/Arr.lhs
index 6d11e38c63..14bc917cca 100644
--- a/libraries/base/GHC/Arr.lhs
+++ b/libraries/base/GHC/Arr.lhs
@@ -491,7 +491,8 @@ fill marr# (I# i#, e) next
 {-# INLINE done #-}
 done :: Ix i => i -> i -> Int -> MutableArray# s e -> STRep s (Array i e)
 -- See NB on 'fill'
-done l u n marr#
+-- Make sure it is strict in 'n'
+done l u n@(I# _) marr#
   = \s1# -> case unsafeFreezeArray# marr# s1# of
               (# s2#, arr# #) -> (# s2#, Array l u n arr# #)
 
@@ -534,11 +535,13 @@ negRange = error "Negative range size"
 {-# INLINE[1] safeIndex #-}
 -- See Note [Double bounds-checking of index values]
 -- Inline *after* (!) so the rules can fire
+-- Make sure it is strict in n
 safeIndex :: Ix i => (i, i) -> Int -> i -> Int
-safeIndex (l,u) n i = let i' = index (l,u) i
-                      in if (0 <= i') && (i' < n)
-                         then i'
-                         else badSafeIndex i' n
+safeIndex (l,u) n@(I# _) i 
+  | (0 <= i') && (i' < n) = i'
+  | otherwise             = badSafeIndex i' n
+  where
+    i' = index (l,u) i
 
 -- See Note [Double bounds-checking of index values]
 {-# RULES