[project @ 2000-12-15 14:48:09 by simonmar]

Don't eta reduce something we just saturated.  (D'oh!)

This fixes the problem which causes a bootstrapped HEAD compiler to
crash.

diff --git a/ghc/compiler/coreSyn/CoreSat.lhs b/ghc/compiler/coreSyn/CoreSat.lhs
index 1b347d1..b47c514 100644 (file)
--- a/ghc/compiler/coreSyn/CoreSat.lhs
+++ b/ghc/compiler/coreSyn/CoreSat.lhs
@@ -334,7 +334,8 @@ deLam expr@(Lam _ _)
     (bndrs, body) = collectBinders expr
 
     eta expr@(App _ _)
-       | n_remaining >= 0 &&
+       | ok_to_eta_reduce f &&
+         n_remaining >= 0 &&
          and (zipWith ok bndrs last_args) &&
          not (any (`elemVarSet` fvs_remaining) bndrs)
        = Just remaining_expr
@@ -348,6 +349,14 @@ deLam expr@(Lam _ _)
          ok bndr (Var arg) = bndr == arg
          ok bndr other     = False
 
+         -- we can't eta reduce something which must be saturated.
+         ok_to_eta_reduce (Var f)
+                = case idFlavour f of
+                     PrimOpId op  -> False
+                     DataConId dc -> False
+                     other        -> True
+         ok_to_eta_reduce _ = False --safe. ToDo: generalise
+
     eta (Let bind@(NonRec b r) body)
        | not (any (`elemVarSet` fvs) bndrs)
                 = case eta body of