Pipeline blocks (#1579)

* Making Commands match what UntaggedValue needs

* WIP

* WIP

* WIP

* Moved to expressions for conditions

* Add 'each' command to use command blocks

* More cleanup

* Add test for 'each'

* Instead use an expression block

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

@@ -1,9 +1,5 @@
 use crate::value::{Primitive, UntaggedValue, Value};
 use indexmap::IndexMap;
-use nu_errors::ShellError;
-use query_interface::{interfaces, vtable_for, Object, ObjectHash};
-use serde::{Deserialize, Serialize};
-use std::cmp::{Ord, Ordering, PartialOrd};
 use std::fmt::Debug;
 
 /// An evaluation scope. Scopes map variable names to Values and aid in evaluating blocks and expressions.
@@ -42,67 +38,3 @@ impl Scope {
         }
     }
 }
-
-#[typetag::serde(tag = "type")]
-pub trait EvaluateTrait: Debug + Send + Sync + Object + ObjectHash + 'static {
-    fn invoke(&self, scope: &Scope) -> Result<Value, ShellError>;
-    fn clone_box(&self) -> Evaluate;
-}
-
-interfaces!(Evaluate: dyn ObjectHash);
-
-#[typetag::serde]
-impl EvaluateTrait for Evaluate {
-    fn invoke(&self, scope: &Scope) -> Result<Value, ShellError> {
-        self.expr.invoke(scope)
-    }
-
-    fn clone_box(&self) -> Evaluate {
-        self.expr.clone_box()
-    }
-}
-
-#[derive(Debug, Serialize, Deserialize)]
-pub struct Evaluate {
-    expr: Box<dyn EvaluateTrait>,
-}
-
-impl Evaluate {
-    pub fn new(evaluate: impl EvaluateTrait) -> Evaluate {
-        Evaluate {
-            expr: Box::new(evaluate),
-        }
-    }
-}
-
-impl std::hash::Hash for Evaluate {
-    fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
-        self.expr.obj_hash(state)
-    }
-}
-
-impl Clone for Evaluate {
-    fn clone(&self) -> Evaluate {
-        self.expr.clone_box()
-    }
-}
-
-impl Ord for Evaluate {
-    fn cmp(&self, _: &Self) -> Ordering {
-        Ordering::Equal
-    }
-}
-
-impl PartialOrd for Evaluate {
-    fn partial_cmp(&self, _: &Evaluate) -> Option<Ordering> {
-        Some(Ordering::Equal)
-    }
-}
-
-impl PartialEq for Evaluate {
-    fn eq(&self, _: &Evaluate) -> bool {
-        true
-    }
-}
-
-impl Eq for Evaluate {}