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, 5 insertions, 5 deletions

diff --git a/compiler/rustc_mir/src/transform/coverage/mod.rs b/compiler/rustc_mir/src/transform/coverage/mod.rs
index aca11de4516..918d6ee4b0c 100644
--- a/compiler/rustc_mir/src/transform/coverage/mod.rs
+++ b/compiler/rustc_mir/src/transform/coverage/mod.rs
@@ -169,8 +169,8 @@ impl<'a, 'tcx> Instrumentor<'a, 'tcx> {
         debug!(
             "instrumenting {:?}, fn sig span: {}, body span: {}",
             def_id,
-            source_map.span_to_string(fn_sig_span),
-            source_map.span_to_string(body_span)
+            source_map.span_to_diagnostic_string(fn_sig_span),
+            source_map.span_to_diagnostic_string(body_span)
         );
 
         let mut graphviz_data = debug::GraphvizData::new();
@@ -311,7 +311,7 @@ impl<'a, 'tcx> Instrumentor<'a, 'tcx> {
         let tcx = self.tcx;
         let source_map = tcx.sess.source_map();
         let body_span = self.body_span;
-        let file_name = Symbol::intern(&self.source_file.name.to_string());
+        let file_name = Symbol::intern(&self.source_file.name.prefer_remapped().to_string_lossy());
 
         let mut bcb_counters = IndexVec::from_elem_n(None, self.basic_coverage_blocks.num_nodes());
         for covspan in coverage_spans {
@@ -332,8 +332,8 @@ impl<'a, 'tcx> Instrumentor<'a, 'tcx> {
                 "Calling make_code_region(file_name={}, source_file={:?}, span={}, body_span={})",
                 file_name,
                 self.source_file,
-                source_map.span_to_string(span),
-                source_map.span_to_string(body_span)
+                source_map.span_to_diagnostic_string(span),
+                source_map.span_to_diagnostic_string(body_span)
             );
 
             inject_statement(