Fixup lift_lets

Author: smowton

src/goto-symex/goto_symex.h

@@ -516,7 +516,7 @@ class goto_symext
   /// The assignments will be made in bottom-up topological but otherwise
   /// arbitrary order (i.e. in `(let x = let y = 0 in x + y) + (let z = 0 in z)
   /// we will define `y` before `x`, but `z` and `x` could come in either order)
-  void lift_lets(statet &, exprt &, assignment_typet);
+  void lift_lets(statet &, exprt &);
 
   /// Execute a single let expression, which should not have any nested let
   /// expressions (use \ref lift_lets instead if there might be).

src/goto-symex/symex_clean_expr.cpp

@@ -188,7 +188,7 @@ void goto_symext::lift_let(statet &state, const let_exprt &let_expr)
     symex_targett::assignment_typet::HIDDEN);
 }
 
-symex_live_let_variablest goto_symext::lift_lets(statet &state, exprt &rhs)
+void goto_symext::lift_lets(statet &state, exprt &rhs)
 {
   for(auto it = rhs.depth_begin(), itend = rhs.depth_end(); it != itend;)
   {