Auto merge of #79957 - jyn514:smaller-span, r=GuillaumeGomez

[rustdoc] Calculate span information on demand instead of storing it ahead of time

This brings `size_of<clean::types::Span>()` down from over 100 bytes (!!) to only 12, the same as rustc. It brings `Item` down even more, from `784` to `680`.

~~TODO: I need to figure out how to do this for the JSON backend too. That uses `From` impls everywhere, which don't allow passing in the `Session` as an argument. `@P1n3appl3,` `@tmandry,` maybe one of you have ideas?~~ Figured it out, fortunately only two functions needed to be changed. I like the `convert_x()` format better than `From` everywhere but I'm open to feedback.

Helps with #79103

1 files changed, 5 insertions, 1 deletions

diff --git a/src/librustdoc/formats/renderer.rs b/src/librustdoc/formats/renderer.rs
index d0fdc69cc19..6334524eb1c 100644
--- a/src/librustdoc/formats/renderer.rs
+++ b/src/librustdoc/formats/renderer.rs
@@ -1,5 +1,7 @@
 use std::sync::Arc;
 
+use rustc_data_structures::sync::Lrc;
+use rustc_session::Session;
 use rustc_span::edition::Edition;
 
 use crate::clean;
@@ -19,6 +21,7 @@ crate trait FormatRenderer: Clone {
         render_info: RenderInfo,
         edition: Edition,
         cache: &mut Cache,
+        sess: Lrc<Session>,
     ) -> Result<(Self, clean::Crate), Error>;
 
     /// Renders a single non-module item. This means no recursive sub-item rendering is required.
@@ -49,6 +52,7 @@ crate fn run_format<T: FormatRenderer>(
     render_info: RenderInfo,
     diag: &rustc_errors::Handler,
     edition: Edition,
+    sess: Lrc<Session>,
 ) -> Result<(), Error> {
     let (krate, mut cache) = Cache::from_krate(
         render_info.clone(),
@@ -59,7 +63,7 @@ crate fn run_format<T: FormatRenderer>(
     );
 
     let (mut format_renderer, mut krate) =
-        T::init(krate, options, render_info, edition, &mut cache)?;
+        T::init(krate, options, render_info, edition, &mut cache, sess)?;
 
     let cache = Arc::new(cache);
     // Freeze the cache now that the index has been built. Put an Arc into TLS for future