apply all style review comments

milli/src/fieldids_weights_map.rs

@@ -1,3 +1,5 @@
+//! The fieldids weights map is in charge of storing linking the searchable fields with their weights.
+
 use std::collections::HashMap;
 
 use serde::{Deserialize, Serialize};
@@ -10,22 +12,29 @@ pub struct FieldidsWeightsMap {
 }
 
 impl FieldidsWeightsMap {
+    /// Insert a field id -> weigth into the map.
+    /// If the map did not have this key present, `None` is returned.
+    /// If the map did have this key present, the value is updated, and the old value is returned.
     pub fn insert(&mut self, fid: FieldId, weight: Weight) -> Option<Weight> {
         self.map.insert(fid, weight)
     }
 
+    /// Removes a field id from the map, returning the associated weight previously in the map.
     pub fn remove(&mut self, fid: FieldId) -> Option<Weight> {
         self.map.remove(&fid)
     }
 
+    /// Returns weight corresponding to the key.
     pub fn weight(&self, fid: FieldId) -> Option<Weight> {
         self.map.get(&fid).copied()
     }
 
+    /// Returns highest weight contained in the map if any.
     pub fn max_weight(&self) -> Option<Weight> {
         self.map.values().copied().max()
     }
 
+    /// Return an iterator visiting all field ids in arbitrary order.
     pub fn ids(&self) -> impl Iterator<Item = FieldId> + '_ {
         self.map.keys().copied()
     }