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

3 files changed, 12 insertions, 10 deletions

diff --git a/compiler/rustc_save_analysis/src/dump_visitor.rs b/compiler/rustc_save_analysis/src/dump_visitor.rs
index 12c77e0c8a6..54b6a121585 100644
--- a/compiler/rustc_save_analysis/src/dump_visitor.rs
+++ b/compiler/rustc_save_analysis/src/dump_visitor.rs
@@ -190,7 +190,7 @@ impl<'tcx> DumpVisitor<'tcx> {
         };
 
         let data = CompilationOptions {
-            directory: self.tcx.sess.working_dir.0.clone(),
+            directory: self.tcx.sess.working_dir.remapped_path_if_available().into(),
             program,
             arguments,
             output: self.save_ctxt.compilation_output(crate_name),
@@ -1112,7 +1112,7 @@ impl<'tcx> DumpVisitor<'tcx> {
                 name: String::new(),
                 qualname,
                 span,
-                value: filename.to_string(),
+                value: filename.prefer_remapped().to_string(),
                 children,
                 parent: None,
                 decl_id: None,
diff --git a/compiler/rustc_save_analysis/src/lib.rs b/compiler/rustc_save_analysis/src/lib.rs
index 7256e68b87a..bcd125ae01d 100644
--- a/compiler/rustc_save_analysis/src/lib.rs
+++ b/compiler/rustc_save_analysis/src/lib.rs
@@ -80,7 +80,7 @@ impl<'tcx> SaveContext<'tcx> {
         let end = sm.lookup_char_pos(span.hi());
 
         SpanData {
-            file_name: start.file.name.to_string().into(),
+            file_name: start.file.name.prefer_remapped().to_string().into(),
             byte_start: span.lo().0,
             byte_end: span.hi().0,
             line_start: Row::new_one_indexed(start.line as u32),
@@ -290,7 +290,7 @@ impl<'tcx> SaveContext<'tcx> {
                     name: item.ident.to_string(),
                     qualname,
                     span: self.span_from_span(item.ident.span),
-                    value: filename.to_string(),
+                    value: filename.prefer_remapped().to_string(),
                     parent: None,
                     children: m
                         .item_ids
diff --git a/compiler/rustc_save_analysis/src/span_utils.rs b/compiler/rustc_save_analysis/src/span_utils.rs
index edcd4925773..1947b04f441 100644
--- a/compiler/rustc_save_analysis/src/span_utils.rs
+++ b/compiler/rustc_save_analysis/src/span_utils.rs
@@ -16,8 +16,7 @@ impl<'a> SpanUtils<'a> {
 
     pub fn make_filename_string(&self, file: &SourceFile) -> String {
         match &file.name {
-            FileName::Real(name) if !file.name_was_remapped => {
-                let path = name.local_path();
+            FileName::Real(RealFileName::LocalPath(path)) => {
                 if path.is_absolute() {
                     self.sess
                         .source_map()
@@ -27,12 +26,15 @@ impl<'a> SpanUtils<'a> {
                         .display()
                         .to_string()
                 } else {
-                    self.sess.working_dir.0.join(&path).display().to_string()
+                    self.sess
+                        .working_dir
+                        .remapped_path_if_available()
+                        .join(&path)
+                        .display()
+                        .to_string()
                 }
             }
-            // If the file name is already remapped, we assume the user
-            // configured it the way they wanted to, so use that directly
-            filename => filename.to_string(),
+            filename => filename.prefer_remapped().to_string(),
         }
     }