Fix scoped type variables for expression type signatures

[ghc-hetmet.git] / compiler / specialise / SpecConstr.lhs

diff --git a/compiler/specialise/SpecConstr.lhs b/compiler/specialise/SpecConstr.lhs
index 78d1731..e5583e1 100644 (file)
--- a/compiler/specialise/SpecConstr.lhs
+++ b/compiler/specialise/SpecConstr.lhs
@@ -583,10 +583,7 @@ conArgOccs :: ArgOcc -> AltCon -> [ArgOcc]
 
 conArgOccs (ScrutOcc fm) (DataAlt dc) 
   | Just pat_arg_occs <- lookupUFM fm dc
-  = tyvar_unks ++ pat_arg_occs
-  where
-    tyvar_unks | isVanillaDataCon dc = [UnkOcc | tv <- dataConUnivTyVars dc]
-              | otherwise           = []
+  = [UnkOcc | tv <- dataConUnivTyVars dc] ++ pat_arg_occs
 
 conArgOccs other con = repeat UnkOcc
 \end{code}
@@ -878,6 +875,13 @@ argToPat in_scope con_env (Var v) arg_occ
     then return (True, Var v)
     else wildCardPat (idType v)
 
+argToPat in_scope con_env (Let _ arg) arg_occ
+  = argToPat in_scope con_env arg arg_occ
+       -- Look through let expressions
+       -- e.g.         f (let v = rhs in \y -> ...v...)
+       -- Here we can specialise for f (\y -> ...)
+       -- because the rule-matcher will look through the let.
+
 argToPat in_scope con_env arg arg_occ
   | is_value_lam arg
   = return (True, arg)