Support iterating over reflective lists

hornbeam_interpreter/src/engine.rs

@@ -203,6 +203,32 @@ impl<'a, O: OutputSystem + Send, LS: LocalisationSystem + Sync + Send> Interpret
                             self.scopes[scope_idx].variables.remove(binding as &str);
                         }
                     }
+                    Value::Reflective(reflective) => match reflective.reflect_ref() {
+                        ReflectRef::List(list) => {
+                            if list.is_empty() {
+                                self.run_steps(scope_idx, empty_steps).await?;
+                            } else {
+                                for idx in 0..list.len() {
+                                    // TODO(performance) I'd like to remove this clone!
+                                    //                   Can possibly do so with a Yoke or something...
+                                    let val = list.get(idx).expect("checked iter").clone_value();
+                                    self.scopes[scope_idx].variables.insert(
+                                        String::from(binding as &str),
+                                        Value::from_reflect(val),
+                                    );
+                                    self.run_steps(scope_idx, body_steps).await?;
+                                }
+                                self.scopes[scope_idx].variables.remove(binding as &str);
+                            }
+                        }
+                        other => {
+                            return Err(InterpreterError::TypeError {
+                                context: "For".to_string(),
+                                conflict: format!("not iterable reflective: {reflective:?}."),
+                                location: step.locator.clone(),
+                            });
+                        }
+                    },
                     // TODO string?
                     // TODO map (with k,v binding)?
                     other => {