perf: Use bincode to encode items rather than JSON

Author: LukeMathWalker

compiler/pavexc/src/rustdoc/compute/cache.rs

@@ -798,7 +798,6 @@ pub(in crate::rustdoc) struct SecondaryIndexes<'a> {
 impl<'a> CacheEntry<'a> {
     pub fn new(krate: &'a crate::rustdoc::Crate) -> Result<CacheEntry<'a>, anyhow::Error> {
         let mut cached = Self::raw(krate)?;
-
         let import_index = bincode::serde::encode_to_vec(&krate.import_index, BINCODE_CONFIG)?;
         let annotated_items =
             bincode::serde::encode_to_vec(&krate.annotated_items, BINCODE_CONFIG)?;
@@ -827,7 +826,7 @@ impl<'a> CacheEntry<'a> {
         let mut item_id2delimiters = HashMap::new();
         for (item_id, item) in &index.index {
             let start = items.len();
-            serde_json::to_writer(&mut items, item)?;
+            bincode::serde::encode_into_std_write(item, &mut items, bincode::config::standard())?;
             let end = items.len();
             item_id2delimiters.insert(item_id.0, (start, end));
         }

compiler/pavexc/src/rustdoc/queries.rs

@@ -935,9 +935,10 @@ impl CrateItemIndex {
             Self::Lazy(index) => {
                 let (start, end) = index.item_id2delimiters.get(id)?;
                 let bytes = index.items[*start..*end].to_vec();
-                let item = serde_json::from_slice(&bytes).expect(
-                    "Failed to deserialize an item from a lazy `rustdoc` index. This is a bug.",
-                );
+                let (item, _) =
+                    bincode::serde::decode_from_slice(&bytes, bincode::config::standard()).expect(
+                        "Failed to deserialize an item from a lazy `rustdoc` index. This is a bug.",
+                    );
                 Some(Cow::Owned(item))
             }
         }