Use macros for creating the intermediate stage.

This is to make it easier to change function signatures by consolidating the places where the signatures exist.

src/intermediate/document_element.rs

@@ -1,8 +1,8 @@
-use crate::error::CustomError;
-
+use super::macros::iselector;
 use super::registry::Registry;
 use super::IHeading;
 use super::ISection;
+use crate::error::CustomError;
 use futures::future::{BoxFuture, FutureExt};
 
 #[derive(Debug, Clone)]
@@ -11,21 +11,17 @@ pub(crate) enum IDocumentElement {
     Section(ISection),
 }
 
-impl IDocumentElement {
-    pub(crate) fn new<'parse, 'b>(
-        registry: &'b mut Registry<'parse>,
-        original: &'b organic::types::DocumentElement<'parse>,
-    ) -> BoxFuture<'b, Result<IDocumentElement, CustomError>> {
-        async move {
-            match original {
-                organic::types::DocumentElement::Heading(inner) => Ok(IDocumentElement::Heading(
-                    IHeading::new(registry, inner).await?,
-                )),
-                organic::types::DocumentElement::Section(inner) => Ok(IDocumentElement::Section(
-                    ISection::new(registry, inner).await?,
-                )),
-            }
+iselector!(
+    IDocumentElement,
+    DocumentElement,
+    |registry, original| async {
+        match &original {
+            organic::types::DocumentElement::Heading(inner) => Ok(IDocumentElement::Heading(
+                IHeading::new(registry, inner).await?,
+            )),
+            organic::types::DocumentElement::Section(inner) => Ok(IDocumentElement::Section(
+                ISection::new(registry, inner).await?,
+            )),
         }
-        .boxed()
     }
-}
+);