tentatively seems to be working.

src/bin.rs

@@ -1,5 +1,6 @@
 extern crate nom;
 
+use crate::renderer::CompareContextElement;
 use crate::renderer::IntoBoxedContextElement;
 use parser::Filter;
 use renderer::compile_template;
@@ -11,6 +12,7 @@ use renderer::RenderError;
 use renderer::Renderable;
 use renderer::WalkError;
 use renderer::Walkable;
+use std::any::Any;
 use std::env;
 use std::fs;
 use std::io::{self, Read};
@@ -144,3 +146,16 @@ impl IntoBoxedContextElement for serde_json::Value {
         Box::new(self.clone())
     }
 }
+
+impl CompareContextElement for serde_json::Value {
+    fn to_any(&self) -> &dyn Any {
+        self
+    }
+
+    fn equals(&self, other: &dyn ContextElement) -> bool {
+        other
+            .to_any()
+            .downcast_ref::<Self>()
+            .map_or(false, |a| self == a)
+    }
+}

src/renderer/context_element.rs

@@ -5,7 +5,7 @@ use std::any::Any;
 use std::fmt::Debug;
 
 pub trait ContextElement:
-    Debug + Walkable + Renderable + Loopable + IntoBoxedContextElement
+    Debug + Walkable + Renderable + Loopable + IntoBoxedContextElement + CompareContextElement
 {
 }
 
@@ -32,6 +32,8 @@ pub trait Loopable {
 
 pub trait CompareContextElement {
     fn to_any(&self) -> &dyn Any;
+
+    fn equals(&self, other: &dyn ContextElement) -> bool;
 }
 
 pub trait IntoBoxedContextElement {

src/renderer/mod.rs

@@ -7,6 +7,7 @@ mod parameters_context;
 mod renderer;
 mod walking;
 
+pub use context_element::CompareContextElement;
 pub use context_element::ContextElement;
 pub use context_element::IntoBoxedContextElement;
 pub use context_element::Loopable;

src/renderer/parameters_context.rs

@@ -1,5 +1,6 @@
 use crate::parser::KVPair;
 use crate::parser::{Filter, RValue};
+use crate::renderer::context_element::CompareContextElement;
 use crate::renderer::context_element::ContextElement;
 use crate::renderer::context_element::IntoBoxedContextElement;
 use crate::renderer::walking::walk_path;
@@ -8,6 +9,7 @@ use crate::renderer::RenderError;
 use crate::renderer::Renderable;
 use crate::renderer::WalkError;
 use crate::renderer::Walkable;
+use std::any::Any;
 use std::collections::HashMap;
 
 /// Copy the data from an RValue to an Owned struct
@@ -146,3 +148,16 @@ impl IntoBoxedContextElement for String {
         Box::new(self.clone())
     }
 }
+
+impl CompareContextElement for String {
+    fn to_any(&self) -> &dyn Any {
+        self
+    }
+
+    fn equals(&self, other: &dyn ContextElement) -> bool {
+        other
+            .to_any()
+            .downcast_ref::<Self>()
+            .map_or(false, |a| self == a)
+    }
+}

src/renderer/renderer.rs

@@ -245,6 +245,9 @@ impl<'a> DustRenderer<'a> {
                             RValue::RVPath(path) => walk_path(breadcrumbs, &path.keys),
                         },
                     };
+                if left_side.unwrap().equals(right_side.unwrap()) {
+                    panic!("testing");
+                }
                 // let x = WalkError::CantWalk;
                 // let y = WalkError::CantWalk;
                 // if x == y {