Add a Loopable trait for dust sections.

src/renderer/renderer.rs

@@ -114,6 +114,7 @@ fn walk_path<'a>(
 mod tests {
     use super::*;
     use crate::parser::Filter;
+    use crate::renderer::context_element::Loopable;
     use crate::renderer::context_element::Renderable;
     use crate::renderer::context_element::Walkable;
 
@@ -172,6 +173,28 @@ mod tests {
             }
         }
 
+        impl Loopable for &str {
+            fn get_loop_elements(&self) -> Result<Vec<&dyn ContextElement>, RenderError> {
+                if self.is_empty() {
+                    Ok(Vec::new())
+                } else {
+                    Ok(vec![self])
+                }
+            }
+        }
+
+        impl Loopable for u32 {
+            fn get_loop_elements(&self) -> Result<Vec<&dyn ContextElement>, RenderError> {
+                Ok(vec![self])
+            }
+        }
+
+        impl<I: ContextElement> Loopable for HashMap<&str, I> {
+            fn get_loop_elements(&self) -> Result<Vec<&dyn ContextElement>, RenderError> {
+                Ok(vec![self])
+            }
+        }
+
         let context: HashMap<&str, &str> =
             [("cat", "kitty"), ("dog", "doggy"), ("tiger", "murderkitty")]
                 .iter()