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, 15 insertions, 0 deletions

diff --git a/src/test/codegen/remap_path_prefix/issue-73167-remap-std.rs b/src/test/codegen/remap_path_prefix/issue-73167-remap-std.rs
new file mode 100644
index 00000000000..b66abc6bedf
--- /dev/null
+++ b/src/test/codegen/remap_path_prefix/issue-73167-remap-std.rs
@@ -0,0 +1,15 @@
+// ignore-windows
+
+// compile-flags: -g  -C no-prepopulate-passes -Z simulate-remapped-rust-src-base=/rustc/xyz
+
+// Here we check that importing std will not cause real path to std source files
+// to leak. If rustc was compiled with remap-debuginfo = true, this should be
+// true automatically. If paths to std library hasn't been remapped, we use the
+// above simulate-remapped-rust-src-base option to do it temporarily
+
+// CHECK: !DIFile(filename: "{{/rustc/.*/library/std/src/panic.rs}}"
+fn main() {
+    std::thread::spawn(|| {
+        println!("hello");
+    });
+}