message: Use a try_map
  Summary: Almost perfectly suited for it.
diff: @@ -111,13 +111,7 @@ impl Compiler<'_> {
  + Sync,
  > {
  let v = v.into_map(|x| self.expr(x).as_compiled());
  - box move |eval| {
  - let mut r = Vec::with_capacity(v.len());
  - for s in &v {
  - r.push(s(eval)?)
  - }
  - Ok(r)
  - }
  + box move |eval| v.try_map(|s| s(eval))
  }
  }
  