`"(__askama_item"` is not a valid identifier

While porting `uniffi` on the new askama version, I got this error. I reduced it to this:

```rust
{%- macro w(lol) %}
y: {{- lol -}}
{% endmacro -%}

{%- for x in &[0] -%}
{%- call w(loop.index) %}{% endcall -%}
{% endfor %}
```