Implement conversion from IceResult into BreadcrumbTreeNode.

I believe this change will remove an extra heap allocation I was doing in the new_breadcrumbs_* functions for the explicit context by adding support for converting from Rc<dyn ContextElement> to Rc<dyn IntoContextElement> without copying the underlying data. This should allow conversion of the IceResult::Owned variant to the BreadcrumbTreeElement::Owned variant without extra copying.

src/renderer/breadcrumb_tree.rs

@@ -1,5 +1,7 @@
+use crate::renderer::context_element::ContextElement;
 use crate::renderer::context_element::IceResult;
 use crate::renderer::context_element::IntoContextElement;
+use crate::renderer::context_element::IntoRcIce;
 use std::borrow::Borrow;
 use std::rc::Rc;
 
@@ -29,6 +31,15 @@ impl<'a> From<&'a IceResult<'a>> for BreadcrumbTreeElement<'a> {
     }
 }
 
+impl<'a> From<IceResult<'a>> for BreadcrumbTreeElement<'a> {
+    fn from(inp: IceResult<'a>) -> Self {
+        match inp {
+            IceResult::Owned(rc_ce) => BreadcrumbTreeElement::Owned(rc_ce.into_rc_ice()),
+            IceResult::Borrowed(ce) => BreadcrumbTreeElement::Borrowed(ce.from_context_element()),
+        }
+    }
+}
+
 impl<'a> BreadcrumbTree<'a> {
     pub fn new(parent: Option<&'a BreadcrumbTree>, element: BreadcrumbTreeElement<'a>) -> Self {
         BreadcrumbTree {

src/renderer/context_element.rs

@@ -16,6 +16,7 @@ pub trait ContextElement:
     // + CloneIntoBoxedContextElement
     + CompareContextElement
     + FromContextElement
+    + IntoRcIce
 {
 }
 
@@ -119,6 +120,16 @@ impl<C: ContextElement> IntoContextElement for C {
     }
 }
 
+pub trait IntoRcIce {
+    fn into_rc_ice(self: Rc<Self>) -> Rc<dyn IntoContextElement>;
+}
+
+impl<C: 'static + ContextElement> IntoRcIce for C {
+    fn into_rc_ice(self: Rc<C>) -> Rc<dyn IntoContextElement> {
+        Rc::clone(&self) as Rc<dyn IntoContextElement>
+    }
+}
+
 #[derive(Clone, Debug)]
 pub enum IceResult<'a> {
     // Using Rc so that when we need to create BreadcrumbTrees with

src/renderer/parameters_context.rs

@@ -3,6 +3,7 @@ use crate::parser::KVPair;
 use crate::parser::OwnedLiteral;
 use crate::parser::RValue;
 use crate::renderer::breadcrumb_tree::BreadcrumbTree;
+use crate::renderer::breadcrumb_tree::BreadcrumbTreeElement;
 use crate::renderer::context_element::CompareContextElement;
 use crate::renderer::context_element::ContextElement;
 use crate::renderer::context_element::IceResult;
@@ -21,7 +22,7 @@ use std::rc::Rc;
 
 #[derive(Debug)]
 pub struct ParametersContext<'a> {
-    params: HashMap<&'a str, &'a dyn IntoContextElement>,
+    params: HashMap<&'a str, BreadcrumbTreeElement<'a>>,
 }
 
 impl<'a> ParametersContext<'a> {
@@ -38,12 +39,14 @@ impl<'a> ParametersContext<'a> {
         // then those are resolved at the time of access rather than
         // the time of assignment, so we leave them into their
         // original IntoContextElement state.
-        let rendered_params = params
+        let rendered_params: HashMap<&'a str, BreadcrumbTreeElement<'a>> = params
             .iter()
             .map(|kvpair| {
                 let k = kvpair.key;
-                let v: &dyn IntoContextElement = match &kvpair.value {
+                let v: BreadcrumbTreeElement<'a> = match &kvpair.value {
-                    RValue::RVLiteral(owned_literal) => &kvpair.value,
+                    RValue::RVLiteral(owned_literal) => {
+                        BreadcrumbTreeElement::Borrowed(&kvpair.value)
+                    }
                     /*RValue::RVPath(path) => kvpair
                     .value
                     .into_context_element(renderer, breadcrumbs)

src/renderer/renderer.rs

@@ -227,7 +227,7 @@ impl<'a> DustRenderer<'a> {
                 .flatten()
                 .map(|val| {
                     if val.get_context_element_reference().is_truthy() {
-                        new_nodes.push(BreadcrumbTreeElement::Owned(Rc::new(val)))
+                        new_nodes.push(std::convert::From::from(val))
                     }
                 });
         });
@@ -297,7 +297,7 @@ impl<'a> DustRenderer<'a> {
                 .flatten()
                 .map(|val| {
                     if val.get_context_element_reference().is_truthy() {
-                        new_nodes.push(BreadcrumbTreeElement::Owned(Rc::new(val)));
+                        new_nodes.push(std::convert::From::from(val));
                     }
                 });
         });