Auto merge of #83813 - cbeuw:remap-std, r=michaelwoerister

Fix `--remap-path-prefix` not correctly remapping `rust-src` component paths and unify handling of path mapping with virtualized paths

This PR fixes #73167 ("Binaries end up containing path to the rust-src component despite `--remap-path-prefix`") by preventing real local filesystem paths from reaching compilation output if the path is supposed to be remapped.

`RealFileName::Named` introduced in #72767 is now renamed as `LocalPath`, because this variant wraps a (most likely) valid local filesystem path.

`RealFileName::Devirtualized` is renamed as `Remapped` to be used for remapped path from a real path via `--remap-path-prefix` argument, as well as real path inferred from a virtualized (during compiler bootstrapping) `/rustc/...` path. The `local_path` field is now an `Option<PathBuf>`, as it will be set to `None` before serialisation, so it never reaches any build output. Attempting to serialise a non-`None` `local_path` will cause an assertion faliure.

When a path is remapped, a `RealFileName::Remapped` variant is created. The original path is preserved in `local_path` field and the remapped path is saved in `virtual_name` field. Previously, the `local_path` is directly modified which goes against its purpose of "suitable for reading from the file system on the local host".

`rustc_span::SourceFile`'s fields `unmapped_path` (introduced by #44940) and `name_was_remapped` (introduced by #41508 when `--remap-path-prefix` feature originally added) are removed, as these two pieces of information can be inferred from the `name` field: if it's anything other than a `FileName::Real(_)`, or if it is a `FileName::Real(RealFileName::LocalPath(_))`, then clearly `name_was_remapped` would've been false and `unmapped_path` would've been `None`. If it is a `FileName::Real(RealFileName::Remapped{local_path, virtual_name})`, then `name_was_remapped` would've been true and `unmapped_path` would've been `Some(local_path)`.

cc `@eddyb` who implemented `/rustc/...` path devirtualisation

1 files changed, 2 insertions, 2 deletions

diff --git a/src/librustdoc/html/render/context.rs b/src/librustdoc/html/render/context.rs
index 666d9dfc3e9..8fd5d8b6b85 100644
--- a/src/librustdoc/html/render/context.rs
+++ b/src/librustdoc/html/render/context.rs
@@ -293,7 +293,7 @@ impl<'tcx> Context<'tcx> {
 
         // We can safely ignore synthetic `SourceFile`s.
         let file = match item.span(self.tcx()).filename(self.sess()) {
-            FileName::Real(ref path) => path.local_path().to_path_buf(),
+            FileName::Real(ref path) => path.local_path_if_available().to_path_buf(),
             _ => return None,
         };
         let file = &file;
@@ -380,7 +380,7 @@ impl<'tcx> FormatRenderer<'tcx> for Context<'tcx> {
         } = options;
 
         let src_root = match krate.src {
-            FileName::Real(ref p) => match p.local_path().parent() {
+            FileName::Real(ref p) => match p.local_path_if_available().parent() {
                 Some(p) => p.to_path_buf(),
                 None => PathBuf::new(),
             },