Starting a context for partial parameters.

src/renderer/renderer.rs

@@ -1,6 +1,7 @@
 use crate::parser::template;
 use crate::parser::Body;
 use crate::parser::DustTag;
+use crate::parser::RValue;
 use crate::parser::Special;
 use crate::parser::Template;
 use crate::parser::TemplateElement;
@@ -253,6 +254,11 @@ fn walk_path<'a>(
     })
 }
 
+struct ParametersContext<'a> {
+    params: HashMap<&'a str, RValue<'a>>,
+    breadcrumbs: &'a Vec<&'a dyn ContextElement>,
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;