Improve specialisation in SpecConstr

This patch enables argToPat to 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.

diff --git a/compiler/specialise/SpecConstr.lhs b/compiler/specialise/SpecConstr.lhs
index 8bba247..e5583e1 100644 (file)
--- a/compiler/specialise/SpecConstr.lhs
+++ b/compiler/specialise/SpecConstr.lhs
@@ -875,6 +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)