message: Resolve a useless_let_if_seq lint warning
diff: @@ -86,23 +86,25 @@ pub fn prepare_target<'a, 'cfg>(
  }
  let root = cx.files().out_dir(unit);
  - let mut missing_outputs = false;
  + let missing_outputs = {
  if unit.mode.is_doc() {
  - missing_outputs = !root.join(unit.target.crate_name())
  + !root.join(unit.target.crate_name())
  .join("index.html")
  - .exists();
  + .exists()
  } else {
  - for output in cx.outputs(unit)?.iter() {
  - if output.flavor == FileFlavor::DebugInfo {
  - continue;
  - }
  - if !output.path.exists() {
  + match cx.outputs(unit)?
  + .iter()
  + .filter(|output| output.flavor != FileFlavor::DebugInfo)
  + .find(|output| !output.path.exists())
  + {
  + None => false,
  + Some(output) => {
  info!("missing output path {:?}", output.path);
  - missing_outputs = true;
  - break
  + true
  }
  }
  }
  + };
  let allow_failure = bcx.extra_args_for(unit).is_some();
  let target_root = cx.files().target_root().to_path_buf();
  