Calculate span info on-demand instead of ahead of time

This should *vastly* reduce memory usage.

2 files changed, 27 insertions, 15 deletions

diff --git a/src/librustdoc/html/render/mod.rs b/src/librustdoc/html/render/mod.rs
index ff8fd208eea..b91f1a6c0e3 100644
--- a/src/librustdoc/html/render/mod.rs
+++ b/src/librustdoc/html/render/mod.rs
@@ -103,7 +103,6 @@ crate fn ensure_trailing_slash(v: &str) -> impl fmt::Display + '_ {
 /// rustdoc tree).
 #[derive(Clone)]
 crate struct Context {
-    crate sess: Lrc<Session>,
     /// Current hierarchy of components leading down to what's currently being
     /// rendered
     crate current: Vec<String>,
@@ -124,6 +123,7 @@ crate struct Context {
 }
 
 crate struct SharedContext {
+    crate sess: Lrc<Session>,
     /// The path to the crate root source minus the file name.
     /// Used for simplifying paths to the highlighted source code files.
     crate src_root: PathBuf,
@@ -176,6 +176,10 @@ impl Context {
         let filename = format!("{}{}.{}", base, self.shared.resource_suffix, ext,);
         self.dst.join(&filename)
     }
+
+    fn sess(&self) -> &Session {
+        &self.shared.sess
+    }
 }
 
 impl SharedContext {
@@ -459,6 +463,7 @@ impl FormatRenderer for Context {
         }
         let (sender, receiver) = channel();
         let mut scx = SharedContext {
+            sess,
             collapsed: krate.collapsed,
             src_root,
             include_sources,
@@ -498,7 +503,6 @@ impl FormatRenderer for Context {
 
         let cache = Arc::new(cache);
         let mut cx = Context {
-            sess,
             current: Vec::new(),
             dst,
             render_redirect_pages: false,
@@ -1636,24 +1640,24 @@ impl Context {
     /// of their crate documentation isn't known.
     fn src_href(&self, item: &clean::Item, cache: &Cache) -> Option<String> {
         let mut root = self.root_path();
-
         let mut path = String::new();
+        let cnum = item.source.cnum(self.sess());
 
         // We can safely ignore synthetic `SourceFile`s.
-        let file = match item.source.filename {
+        let file = match item.source.filename(self.sess()) {
             FileName::Real(ref path) => path.local_path().to_path_buf(),
             _ => return None,
         };
         let file = &file;
 
-        let (krate, path) = if item.source.cnum == LOCAL_CRATE {
+        let (krate, path) = if cnum == LOCAL_CRATE {
             if let Some(path) = self.shared.local_sources.get(file) {
                 (&self.shared.layout.krate, path)
             } else {
                 return None;
             }
         } else {
-            let (krate, src_root) = match *cache.extern_locations.get(&item.source.cnum)? {
+            let (krate, src_root) = match *cache.extern_locations.get(&cnum)? {
                 (ref name, ref src, ExternalLocation::Local) => (name, src),
                 (ref name, ref src, ExternalLocation::Remote(ref s)) => {
                     root = s.to_string();
@@ -1672,11 +1676,10 @@ impl Context {
             (krate, &path)
         };
 
-        let lines = if item.source.loline == item.source.hiline {
-            item.source.loline.to_string()
-        } else {
-            format!("{}-{}", item.source.loline, item.source.hiline)
-        };
+        let loline = item.source.lo(self.sess()).line;
+        let hiline = item.source.hi(self.sess()).line;
+        let lines =
+            if loline == hiline { loline.to_string() } else { format!("{}-{}", loline, hiline) };
         Some(format!(
             "{root}src/{krate}/{path}#{lines}",
             root = Escape(&root),
diff --git a/src/librustdoc/html/sources.rs b/src/librustdoc/html/sources.rs
index e7b5a90d84d..ef9e9f350fb 100644
--- a/src/librustdoc/html/sources.rs
+++ b/src/librustdoc/html/sources.rs
@@ -7,6 +7,7 @@ use crate::html::highlight;
 use crate::html::layout;
 use crate::html::render::{SharedContext, BASIC_KEYWORDS};
 use rustc_hir::def_id::LOCAL_CRATE;
+use rustc_session::Session;
 use rustc_span::source_map::FileName;
 use std::ffi::OsStr;
 use std::fs;
@@ -34,37 +35,45 @@ struct SourceCollector<'a> {
 
 impl<'a> DocFolder for SourceCollector<'a> {
     fn fold_item(&mut self, item: clean::Item) -> Option<clean::Item> {
+        // If we're not rendering sources, there's nothing to do.
         // If we're including source files, and we haven't seen this file yet,
         // then we need to render it out to the filesystem.
         if self.scx.include_sources
             // skip all synthetic "files"
-            && item.source.filename.is_real()
+            && item.source.filename(self.sess()).is_real()
             // skip non-local files
-            && item.source.cnum == LOCAL_CRATE
+            && item.source.cnum(self.sess()) == LOCAL_CRATE
         {
+            let filename = item.source.filename(self.sess());
             // If it turns out that we couldn't read this file, then we probably
             // can't read any of the files (generating html output from json or
             // something like that), so just don't include sources for the
             // entire crate. The other option is maintaining this mapping on a
             // per-file basis, but that's probably not worth it...
-            self.scx.include_sources = match self.emit_source(&item.source.filename) {
+            self.scx.include_sources = match self.emit_source(&filename) {
                 Ok(()) => true,
                 Err(e) => {
                     println!(
                         "warning: source code was requested to be rendered, \
                          but processing `{}` had an error: {}",
-                        item.source.filename, e
+                        filename, e
                     );
                     println!("         skipping rendering of source code");
                     false
                 }
             };
         }
+        // FIXME: if `include_sources` isn't set and DocFolder didn't require consuming the crate by value,
+        // we could return None here without having to walk the rest of the crate.
         Some(self.fold_item_recur(item))
     }
 }
 
 impl<'a> SourceCollector<'a> {
+    fn sess(&self) -> &Session {
+        &self.scx.sess
+    }
+
     /// Renders the given filename into its corresponding HTML source file.
     fn emit_source(&mut self, filename: &FileName) -> Result<(), Error> {
         let p = match *filename {