Fix lookup_binding in function call case

src/eval.rs

@@ -52,8 +52,6 @@ impl Evaluator {
     }
 
     fn lookup_binding(&mut self, var: String) -> Option<Expression> {
-        self.varmap.map.get(&var).map(|expr| expr.clone())
-            .or_else(|| {
         for frame in self.frames.iter() {
             match frame.map.get(&var) {
                 None => (),
@@ -61,8 +59,7 @@ impl Evaluator {
             }
         }
 
-                None
-            })
+        self.varmap.map.get(&var).map(|expr| expr.clone())
     }
 
     fn add_function(&mut self, name: String, function: Function) {