-- in case x of
-- I# y -> let x = I# y in x }
-- See comments above. Is it not beautifully short?
+-- Moreover, it works just as well when there are
+-- several binders, and if the binders are lifted
+-- E.g. x = e
+-- --> x = let x = e in
+-- case x of (a,b) -> let x = (a,b) in x
splitThunk :: Var -> Expr Var -> UniqSM [(Var, Expr Var)]
splitThunk fn_id rhs = do