Auto merge of #119139 - michaelwoerister:cleanup-stable-source-file-id, r=cjgillot

Unify SourceFile::name_hash and StableSourceFileId

This PR adapts the existing `StableSourceFileId` type so that it can be used instead of the `name_hash` field of `SourceFile`. This simplifies a few things that were kind of duplicated before.

The PR should also fix issues https://github.com/rust-lang/rust/issues/112700 and https://github.com/rust-lang/rust/issues/115835, but I was not able to reproduce these issues in a regression test. As far as I can tell, the root cause of these issues is that the id of the originating crate is not hashed in the `HashStable` impl of `Span` and thus cache entries that should have been considered invalidated were loaded. After this PR, the `stable_id` field of `SourceFile` includes information about the originating crate, so that ICE should not occur anymore.

1 files changed, 15 insertions, 22 deletions

diff --git a/compiler/rustc_middle/src/query/on_disk_cache.rs b/compiler/rustc_middle/src/query/on_disk_cache.rs
index f37cfe8b0a1..0577d22d850 100644
--- a/compiler/rustc_middle/src/query/on_disk_cache.rs
+++ b/compiler/rustc_middle/src/query/on_disk_cache.rs
@@ -1,6 +1,5 @@
 use rustc_data_structures::fx::{FxHashMap, FxIndexSet};
 use rustc_data_structures::memmap::Mmap;
-use rustc_data_structures::stable_hasher::Hash64;
 use rustc_data_structures::sync::{HashMapExt, Lock, Lrc, RwLock};
 use rustc_data_structures::unhash::UnhashMap;
 use rustc_data_structures::unord::UnordSet;
@@ -21,8 +20,10 @@ use rustc_session::Session;
 use rustc_span::hygiene::{
     ExpnId, HygieneDecodeContext, HygieneEncodeContext, SyntaxContext, SyntaxContextData,
 };
-use rustc_span::source_map::{SourceMap, StableSourceFileId};
-use rustc_span::{BytePos, ExpnData, ExpnHash, Pos, RelativeBytePos, SourceFile, Span};
+use rustc_span::source_map::SourceMap;
+use rustc_span::{
+    BytePos, ExpnData, ExpnHash, Pos, RelativeBytePos, SourceFile, Span, StableSourceFileId,
+};
 use rustc_span::{CachingSourceMapView, Symbol};
 use std::collections::hash_map::Entry;
 use std::mem;
@@ -133,30 +134,18 @@ impl AbsoluteBytePos {
     }
 }
 
-/// An `EncodedSourceFileId` is the same as a `StableSourceFileId` except that
-/// the source crate is represented as a [StableCrateId] instead of as a
-/// `CrateNum`. This way `EncodedSourceFileId` can be encoded and decoded
-/// without any additional context, i.e. with a simple `opaque::Decoder` (which
-/// is the only thing available when decoding the cache's [Footer].
 #[derive(Encodable, Decodable, Clone, Debug)]
 struct EncodedSourceFileId {
-    file_name_hash: Hash64,
+    stable_source_file_id: StableSourceFileId,
     stable_crate_id: StableCrateId,
 }
 
 impl EncodedSourceFileId {
     #[inline]
-    fn translate(&self, tcx: TyCtxt<'_>) -> StableSourceFileId {
-        let cnum = tcx.stable_crate_id_to_crate_num(self.stable_crate_id);
-        StableSourceFileId { file_name_hash: self.file_name_hash, cnum }
-    }
-
-    #[inline]
     fn new(tcx: TyCtxt<'_>, file: &SourceFile) -> EncodedSourceFileId {
-        let source_file_id = StableSourceFileId::new(file);
         EncodedSourceFileId {
-            file_name_hash: source_file_id.file_name_hash,
-            stable_crate_id: tcx.stable_crate_id(source_file_id.cnum),
+            stable_source_file_id: file.stable_id,
+            stable_crate_id: tcx.stable_crate_id(file.cnum),
         }
     }
 }
@@ -488,7 +477,9 @@ impl<'a, 'tcx> CacheDecoder<'a, 'tcx> {
             .borrow_mut()
             .entry(index)
             .or_insert_with(|| {
-                let stable_id = file_index_to_stable_id[&index].translate(tcx);
+                let source_file_id = &file_index_to_stable_id[&index];
+                let source_file_cnum =
+                    tcx.stable_crate_id_to_crate_num(source_file_id.stable_crate_id);
 
                 // If this `SourceFile` is from a foreign crate, then make sure
                 // that we've imported all of the source files from that crate.
@@ -499,12 +490,14 @@ impl<'a, 'tcx> CacheDecoder<'a, 'tcx> {
                 // that we will load the source files from that crate during macro
                 // expansion, so we use `import_source_files` to ensure that the foreign
                 // source files are actually imported before we call `source_file_by_stable_id`.
-                if stable_id.cnum != LOCAL_CRATE {
-                    self.tcx.cstore_untracked().import_source_files(self.tcx.sess, stable_id.cnum);
+                if source_file_cnum != LOCAL_CRATE {
+                    self.tcx
+                        .cstore_untracked()
+                        .import_source_files(self.tcx.sess, source_file_cnum);
                 }
 
                 source_map
-                    .source_file_by_stable_id(stable_id)
+                    .source_file_by_stable_id(source_file_id.stable_source_file_id)
                     .expect("failed to lookup `SourceFile` in new context")
             })
             .clone()