Fix warnings and split Scope (#1902)

crates/nu-protocol/src/value/evaluate.rs

@@ -1,4 +1,4 @@
-use crate::value::{Primitive, UntaggedValue, Value};
+use crate::value::Value;
 use indexmap::IndexMap;
 use serde::{Deserialize, Serialize};
 use std::fmt::Debug;
@@ -13,69 +13,19 @@ pub struct Scope {
     pub env: IndexMap<String, String>,
 }
 
-impl Scope {
-    /// Create a new scope
-    pub fn new(it: Value) -> Scope {
-        Scope {
-            it,
-            vars: IndexMap::new(),
-            env: IndexMap::new(),
-        }
-    }
-}
-
 impl Scope {
     /// Create an empty scope
-    pub fn empty() -> Scope {
+    pub fn new() -> Scope {
         Scope {
-            it: UntaggedValue::Primitive(Primitive::Nothing).into_untagged_value(),
+            it: Value::nothing(),
             vars: IndexMap::new(),
             env: IndexMap::new(),
         }
     }
-
-    /// Create an empty scope, setting $it to a known Value
-    pub fn it_value(value: Value) -> Scope {
-        Scope {
-            it: value,
-            vars: IndexMap::new(),
-            env: IndexMap::new(),
-        }
-    }
-
-    pub fn env(env: IndexMap<String, String>) -> Scope {
-        Scope {
-            it: UntaggedValue::Primitive(Primitive::Nothing).into_untagged_value(),
-            vars: IndexMap::new(),
-            env,
-        }
-    }
-
-    pub fn set_it(self, value: Value) -> Scope {
-        Scope {
-            it: value,
-            vars: self.vars,
-            env: self.env,
-        }
-    }
-
-    pub fn set_var(self, name: String, value: Value) -> Scope {
-        let mut new_vars = self.vars.clone();
-        new_vars.insert(name, value);
-        Scope {
-            it: self.it,
-            vars: new_vars,
-            env: self.env,
-        }
-    }
-
-    pub fn set_env_var(self, variable: String, value: String) -> Scope {
-        let mut new_env_vars = self.env.clone();
-        new_env_vars.insert(variable, value);
-        Scope {
-            it: self.it,
-            vars: self.vars,
-            env: new_env_vars,
-        }
-    }
+}
+
+impl Default for Scope {
+    fn default() -> Scope {
+        Scope::new()
+    }
 }