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

2 files changed, 7 insertions, 10 deletions

diff --git a/compiler/rustc_interface/src/passes.rs b/compiler/rustc_interface/src/passes.rs
index 96dbdce1126..9005325f0b4 100644
--- a/compiler/rustc_interface/src/passes.rs
+++ b/compiler/rustc_interface/src/passes.rs
@@ -35,7 +35,6 @@ use rustc_session::output::{filename_for_input, filename_for_metadata};
 use rustc_session::search_paths::PathKind;
 use rustc_session::Session;
 use rustc_span::symbol::{Ident, Symbol};
-use rustc_span::{FileName, RealFileName};
 use rustc_trait_selection::traits;
 use rustc_typeck as typeck;
 use tracing::{info, warn};
@@ -531,10 +530,10 @@ fn output_conflicts_with_dir(output_paths: &[PathBuf]) -> Option<PathBuf> {
     check_output(output_paths, check)
 }
 
-fn escape_dep_filename(filename: &FileName) -> String {
+fn escape_dep_filename(filename: &String) -> String {
     // Apparently clang and gcc *only* escape spaces:
     // http://llvm.org/klaus/clang/commit/9d50634cfc268ecc9a7250226dd5ca0e945240d4
-    filename.to_string().replace(" ", "\\ ")
+    filename.replace(" ", "\\ ")
 }
 
 // Makefile comments only need escaping newlines and `\`.
@@ -574,7 +573,7 @@ fn write_out_deps(
             .iter()
             .filter(|fmap| fmap.is_real_file())
             .filter(|fmap| !fmap.is_imported())
-            .map(|fmap| escape_dep_filename(&fmap.unmapped_path.as_ref().unwrap_or(&fmap.name)))
+            .map(|fmap| escape_dep_filename(&fmap.name.prefer_local().to_string()))
             .collect();
 
         if let Some(ref backend) = sess.opts.debugging_opts.codegen_backend {
@@ -586,16 +585,13 @@ fn write_out_deps(
                 for cnum in resolver.cstore().crates_untracked() {
                     let source = resolver.cstore().crate_source_untracked(cnum);
                     if let Some((path, _)) = source.dylib {
-                        let file_name = FileName::Real(RealFileName::Named(path));
-                        files.push(escape_dep_filename(&file_name));
+                        files.push(escape_dep_filename(&path.display().to_string()));
                     }
                     if let Some((path, _)) = source.rlib {
-                        let file_name = FileName::Real(RealFileName::Named(path));
-                        files.push(escape_dep_filename(&file_name));
+                        files.push(escape_dep_filename(&path.display().to_string()));
                     }
                     if let Some((path, _)) = source.rmeta {
-                        let file_name = FileName::Real(RealFileName::Named(path));
-                        files.push(escape_dep_filename(&file_name));
+                        files.push(escape_dep_filename(&path.display().to_string()));
                     }
                 }
             });
diff --git a/compiler/rustc_interface/src/tests.rs b/compiler/rustc_interface/src/tests.rs
index fd13cb3d59a..17dc6fd1d52 100644
--- a/compiler/rustc_interface/src/tests.rs
+++ b/compiler/rustc_interface/src/tests.rs
@@ -724,6 +724,7 @@ fn test_debugging_options_tracking_hash() {
     tracked!(profile_emit, Some(PathBuf::from("abc")));
     tracked!(relax_elf_relocations, Some(true));
     tracked!(relro_level, Some(RelroLevel::Full));
+    tracked!(simulate_remapped_rust_src_base, Some(PathBuf::from("/rustc/abc")));
     tracked!(report_delayed_bugs, true);
     tracked!(sanitizer, SanitizerSet::ADDRESS);
     tracked!(sanitizer_memory_track_origins, 2);