Add failing test case for askama-rs#708

Author: msrd0

testing/templates/macro-iter.html.j2

@@ -0,0 +1,16 @@
+{%- macro list(list) -%}
+<ul>
+	{%- for item in list %}
+	<li>{{item}}</li>
+	{%- endfor %}
+</ul>
+<ol>
+	{%- for item in list %}
+	<li>{{item}}</li>
+	{%- endfor %}
+</ol>
+{%- endmacro -%}
+
+{%- for foo in foos %}
+{% call list(foo.list) %}
+{%- endfor %}

testing/tests/macro.rs

@@ -1,4 +1,5 @@
 use askama::Template;
+use std::collections::BTreeSet;
 
 #[derive(Template)]
 #[template(path = "macro.html")]
@@ -73,3 +74,13 @@ fn str_cmp() {
     let t = StrCmpTemplate;
     assert_eq!(t.render().unwrap(), "AfooBotherCneitherD");
 }
+
+#[derive(Template)]
+#[template(path = "macro-iter.html.j2")]
+struct MacroIterTemplate {
+    foos: Vec<Foo>,
+}
+
+struct Foo {
+    list: BTreeSet<String>,
+}