Auto merge of #137229 - GuillaumeGomez:expand-macro, r=lolbinarycat

Add support for macro expansion in rustdoc source code pages

This is what it looks like:

![Screenshot From 2025-02-18 18-08-51](https://github.com/user-attachments/assets/ce2b3806-6218-47df-94bf-e9e9ed40cd41)

![image](https://github.com/user-attachments/assets/891042db-8632-4dba-9343-e28570c058fe)

You can test it [here](https://rustdoc.crud.net/imperio/macro-expansion/src/lib/lib.rs.html). In this case, I also enabled the `--generate-link-to-definition` to show that both options work well together.

Note: <del>There is a bug currently in firefox where the line numbers are not displayed correctly if they're inside the "macro expansion" span: https://bugzilla.mozilla.org/show_bug.cgi?id=1949948<del> Found a workaround around this bug.

r? `@notriddle`

2 files changed, 18 insertions, 12 deletions

diff --git a/src/librustdoc/html/render/context.rs b/src/librustdoc/html/render/context.rs
index e4fca09d64f..faaecaf0cbb 100644
--- a/src/librustdoc/html/render/context.rs
+++ b/src/librustdoc/html/render/context.rs
@@ -12,7 +12,7 @@ use rustc_hir::def_id::{DefIdMap, LOCAL_CRATE};
 use rustc_middle::ty::TyCtxt;
 use rustc_session::Session;
 use rustc_span::edition::Edition;
-use rustc_span::{FileName, Symbol, sym};
+use rustc_span::{BytePos, FileName, Symbol, sym};
 use tracing::info;
 
 use super::print_item::{full_path, print_item, print_item_path};
@@ -28,6 +28,7 @@ use crate::formats::FormatRenderer;
 use crate::formats::cache::Cache;
 use crate::formats::item_type::ItemType;
 use crate::html::escape::Escape;
+use crate::html::macro_expansion::ExpandedCode;
 use crate::html::markdown::{self, ErrorCodes, IdMap, plain_text_summary};
 use crate::html::render::write_shared::write_shared;
 use crate::html::url_parts_builder::UrlPartsBuilder;
@@ -139,6 +140,7 @@ pub(crate) struct SharedContext<'tcx> {
     /// Correspondence map used to link types used in the source code pages to allow to click on
     /// links to jump to the type's definition.
     pub(crate) span_correspondence_map: FxHashMap<rustc_span::Span, LinkFromSrc>,
+    pub(crate) expanded_codes: FxHashMap<BytePos, Vec<ExpandedCode>>,
     /// The [`Cache`] used during rendering.
     pub(crate) cache: Cache,
     pub(crate) call_locations: AllCallLocations,
@@ -458,20 +460,13 @@ impl<'tcx> Context<'tcx> {
     }
 }
 
-/// Generates the documentation for `crate` into the directory `dst`
-impl<'tcx> FormatRenderer<'tcx> for Context<'tcx> {
-    fn descr() -> &'static str {
-        "html"
-    }
-
-    const RUN_ON_MODULE: bool = true;
-    type ModuleData = ContextInfo;
-
-    fn init(
+impl<'tcx> Context<'tcx> {
+    pub(crate) fn init(
         krate: clean::Crate,
         options: RenderOptions,
         cache: Cache,
         tcx: TyCtxt<'tcx>,
+        expanded_codes: FxHashMap<BytePos, Vec<ExpandedCode>>,
     ) -> Result<(Self, clean::Crate), Error> {
         // need to save a copy of the options for rendering the index page
         let md_opts = options.clone();
@@ -579,6 +574,7 @@ impl<'tcx> FormatRenderer<'tcx> for Context<'tcx> {
             cache,
             call_locations,
             should_merge: options.should_merge,
+            expanded_codes,
         };
 
         let dst = output;
@@ -604,6 +600,16 @@ impl<'tcx> FormatRenderer<'tcx> for Context<'tcx> {
 
         Ok((cx, krate))
     }
+}
+
+/// Generates the documentation for `crate` into the directory `dst`
+impl<'tcx> FormatRenderer<'tcx> for Context<'tcx> {
+    fn descr() -> &'static str {
+        "html"
+    }
+
+    const RUN_ON_MODULE: bool = true;
+    type ModuleData = ContextInfo;
 
     fn save_module_data(&mut self) -> Self::ModuleData {
         self.deref_id_map.borrow_mut().clear();
diff --git a/src/librustdoc/html/render/span_map.rs b/src/librustdoc/html/render/span_map.rs
index 846d3ad310c..8bc2e0bd957 100644
--- a/src/librustdoc/html/render/span_map.rs
+++ b/src/librustdoc/html/render/span_map.rs
@@ -35,7 +35,7 @@ pub(crate) enum LinkFromSrc {
 /// 1. Generate a `span` correspondence map which links an item `span` to its definition `span`.
 /// 2. Collect the source code files.
 ///
-/// It returns the `krate`, the source code files and the `span` correspondence map.
+/// It returns the source code files and the `span` correspondence map.
 ///
 /// Note about the `span` correspondence map: the keys are actually `(lo, hi)` of `span`s. We don't
 /// need the `span` context later on, only their position, so instead of keeping a whole `Span`, we