fn merge_map(
res: &mut FxHashMap<EditionedFileId, FxHashSet<HighlightedRange>>,
new: Option<FxHashMap<EditionedFileId, FxHashSet<HighlightedRange>>>,
)fn merge_map(
res: &mut FxHashMap<EditionedFileId, FxHashSet<HighlightedRange>>,
new: Option<FxHashMap<EditionedFileId, FxHashSet<HighlightedRange>>>,
)