Fix build errors on latest nightly

src/evaluate/evaluator.rs

@@ -6,18 +6,24 @@ use crate::parser::{
 };
 use crate::prelude::*;
 use crate::TaggedDictBuilder;
-use derive_new::new;
 use indexmap::IndexMap;
 use log::trace;
 use std::fmt;
 
-#[derive(new)]
 pub struct Scope {
     it: Tagged<Value>,
-    #[new(default)]
     vars: IndexMap<String, Tagged<Value>>,
 }
 
+impl Scope {
+    pub fn new(it: Tagged<Value>) -> Scope {
+        Scope {
+            it,
+            vars: IndexMap::new(),
+        }
+    }
+}
+
 impl fmt::Display for Scope {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_map()