[project @ 2003-09-26 09:01:08 by simonpj]

Better error trace when cat_evals crashes

diff --git a/ghc/compiler/simplCore/Simplify.lhs b/ghc/compiler/simplCore/Simplify.lhs
index 28e3af4..7dc3cfc 100644 (file)
--- a/ghc/compiler/simplCore/Simplify.lhs
+++ b/ghc/compiler/simplCore/Simplify.lhs
@@ -1467,17 +1467,21 @@ simplAlts env zap_occ_info handled_cons case_bndr' alts cont'
        -- We really must record that b is already evaluated so that we don't
        -- go and re-evaluate it when constructing the result.
 
-    add_evals (DataAlt dc) vs = cat_evals vs (dataConRepStrictness dc)
+    add_evals (DataAlt dc) vs = cat_evals dc vs (dataConRepStrictness dc)
     add_evals other_con    vs = vs
 
-    cat_evals [] [] = []
-    cat_evals (v:vs) (str:strs)
-       | isTyVar v          = v        : cat_evals vs (str:strs)
-       | isMarkedStrict str = evald_v  : cat_evals vs strs
-       | otherwise          = zapped_v : cat_evals vs strs
+    cat_evals dc vs strs
+       = go vs strs
        where
-         zapped_v = zap_occ_info v
-         evald_v  = zapped_v `setIdUnfolding` mkOtherCon []
+         go [] [] = []
+         go (v:vs) (str:strs)
+           | isTyVar v          = v        : go vs (str:strs)
+           | isMarkedStrict str = evald_v  : go vs strs
+           | otherwise          = zapped_v : go vs strs
+           where
+             zapped_v = zap_occ_info v
+             evald_v  = zapped_v `setIdUnfolding` mkOtherCon []
+         go _ _ = pprPanic "cat_evals" (ppr dc $$ ppr vs $$ ppr strs)
 \end{code}