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, 6 insertions, 9 deletions

diff --git a/src/librustdoc/passes/calculate_doc_coverage.rs b/src/librustdoc/passes/calculate_doc_coverage.rs
index 3f9978c8fca..52f6a97089b 100644
--- a/src/librustdoc/passes/calculate_doc_coverage.rs
+++ b/src/librustdoc/passes/calculate_doc_coverage.rs
@@ -216,13 +216,9 @@ impl<'a, 'b> fold::DocFolder for CoverageCalculator<'a, 'b> {
                 return Some(i);
             }
             clean::ImplItem(ref impl_) => {
+                let filename = i.source.filename(self.ctx.sess());
                 if let Some(ref tr) = impl_.trait_ {
-                    debug!(
-                        "impl {:#} for {:#} in {}",
-                        tr.print(),
-                        impl_.for_.print(),
-                        i.source.filename
-                    );
+                    debug!("impl {:#} for {:#} in {}", tr.print(), impl_.for_.print(), filename,);
 
                     // don't count trait impls, the missing-docs lint doesn't so we shouldn't
                     // either
@@ -231,7 +227,7 @@ impl<'a, 'b> fold::DocFolder for CoverageCalculator<'a, 'b> {
                     // inherent impls *can* be documented, and those docs show up, but in most
                     // cases it doesn't make sense, as all methods on a type are in one single
                     // impl block
-                    debug!("impl {:#} in {}", impl_.for_.print(), i.source.filename);
+                    debug!("impl {:#} in {}", impl_.for_.print(), filename);
                 }
             }
             _ => {
@@ -251,6 +247,7 @@ impl<'a, 'b> fold::DocFolder for CoverageCalculator<'a, 'b> {
                     None,
                 );
 
+                let filename = i.source.filename(self.ctx.sess());
                 let has_doc_example = tests.found_tests != 0;
                 let hir_id = self.ctx.tcx.hir().local_def_id_to_hir_id(i.def_id.expect_local());
                 let (level, source) = self.ctx.tcx.lint_level_at_node(MISSING_DOCS, hir_id);
@@ -258,8 +255,8 @@ impl<'a, 'b> fold::DocFolder for CoverageCalculator<'a, 'b> {
                 // unless the user had an explicit `allow`
                 let should_have_docs =
                     level != lint::Level::Allow || matches!(source, LintSource::Default);
-                debug!("counting {:?} {:?} in {}", i.type_(), i.name, i.source.filename);
-                self.items.entry(i.source.filename.clone()).or_default().count_item(
+                debug!("counting {:?} {:?} in {}", i.type_(), i.name, filename);
+                self.items.entry(filename).or_default().count_item(
                     has_docs,
                     has_doc_example,
                     should_have_doc_example(self.ctx, &i),