Rollup merge of #109213 - oli-obk:cstore, r=cjgillot

Eagerly intern and check CrateNum/StableCrateId collisions

r? ``@cjgillot``

It seems better to check things ahead of time than checking them afterwards.
The [previous version](https://github.com/rust-lang/rust/pull/108390) was a bit nonsensical, so this addresses the feedback

Cargo.lock

@@ -5294,6 +5294,7 @@ name = "rustc_span"
 version = "0.0.0"
 dependencies = [
  "cfg-if",
+ "indexmap",
  "md-5",
  "rustc_arena",
  "rustc_data_structures",

compiler/rustc_metadata/src/creader.rs

@@ -6,11 +6,11 @@ use crate::rmeta::{CrateDep, CrateMetadata, CrateNumMap, CrateRoot, MetadataBlob
 
 use rustc_ast::expand::allocator::AllocatorKind;
 use rustc_ast::{self as ast, *};
-use rustc_data_structures::fx::{FxHashMap, FxHashSet};
+use rustc_data_structures::fx::FxHashSet;
 use rustc_data_structures::svh::Svh;
 use rustc_data_structures::sync::{MappedReadGuard, MappedWriteGuard, ReadGuard, WriteGuard};
 use rustc_expand::base::SyntaxExtension;
-use rustc_hir::def_id::{CrateNum, LocalDefId, StableCrateId, LOCAL_CRATE};
+use rustc_hir::def_id::{CrateNum, LocalDefId, StableCrateId, StableCrateIdMap, LOCAL_CRATE};
 use rustc_hir::definitions::Definitions;
 use rustc_index::vec::IndexVec;
 use rustc_middle::ty::TyCtxt;
@@ -46,9 +46,8 @@ pub struct CStore {
     /// This crate has a `#[alloc_error_handler]` item.
     has_alloc_error_handler: bool,
 
-    /// This map is used to verify we get no hash conflicts between
+    /// The interned [StableCrateId]s.
-    /// `StableCrateId` values.
+    pub(crate) stable_crate_ids: StableCrateIdMap,
-    pub(crate) stable_crate_ids: FxHashMap<StableCrateId, CrateNum>,
 
     /// Unused externs of the crate
     unused_externs: Vec<Symbol>,
@@ -144,9 +143,21 @@ impl CStore {
         })
     }
 
-    fn alloc_new_crate_num(&mut self) -> CrateNum {
+    fn intern_stable_crate_id(&mut self, root: &CrateRoot) -> Result<CrateNum, CrateError> {
+        assert_eq!(self.metas.len(), self.stable_crate_ids.len());
+        let num = CrateNum::new(self.stable_crate_ids.len());
+        if let Some(&existing) = self.stable_crate_ids.get(&root.stable_crate_id()) {
+            let crate_name0 = root.name();
+            if let Some(crate_name1) = self.metas[existing].as_ref().map(|data| data.name()) {
+                Err(CrateError::StableCrateIdCollision(crate_name0, crate_name1))
+            } else {
+                Err(CrateError::SymbolConflictsCurrent(crate_name0))
+            }
+        } else {
             self.metas.push(None);
-        CrateNum::new(self.metas.len() - 1)
+            self.stable_crate_ids.insert(root.stable_crate_id(), num);
+            Ok(num)
+        }
     }
 
     pub fn has_crate_data(&self, cnum: CrateNum) -> bool {
@@ -247,7 +258,7 @@ impl CStore {
     }
 
     pub fn new(sess: &Session) -> CStore {
-        let mut stable_crate_ids = FxHashMap::default();
+        let mut stable_crate_ids = StableCrateIdMap::default();
         stable_crate_ids.insert(sess.local_stable_crate_id(), LOCAL_CRATE);
         CStore {
             // We add an empty entry for LOCAL_CRATE (which maps to zero) in
@@ -342,42 +353,6 @@ impl<'a, 'tcx> CrateLoader<'a, 'tcx> {
         None
     }
 
-    fn verify_no_symbol_conflicts(&self, root: &CrateRoot) -> Result<(), CrateError> {
-        // Check for (potential) conflicts with the local crate
-        if self.sess.local_stable_crate_id() == root.stable_crate_id() {
-            return Err(CrateError::SymbolConflictsCurrent(root.name()));
-        }
-
-        // Check for conflicts with any crate loaded so far
-        for (_, other) in self.cstore.iter_crate_data() {
-            // Same stable crate id but different SVH
-            if other.stable_crate_id() == root.stable_crate_id() && other.hash() != root.hash() {
-                bug!(
-                    "Previously returned E0523 here. \
-                     See https://github.com/rust-lang/rust/pull/100599 for additional discussion.\
-                     root.name() = {}.",
-                    root.name()
-                );
-            }
-        }
-
-        Ok(())
-    }
-
-    fn verify_no_stable_crate_id_hash_conflicts(
-        &mut self,
-        root: &CrateRoot,
-        cnum: CrateNum,
-    ) -> Result<(), CrateError> {
-        if let Some(existing) = self.cstore.stable_crate_ids.insert(root.stable_crate_id(), cnum) {
-            let crate_name0 = root.name();
-            let crate_name1 = self.cstore.get_crate_data(existing).name();
-            return Err(CrateError::StableCrateIdCollision(crate_name0, crate_name1));
-        }
-
-        Ok(())
-    }
-
     fn register_crate(
         &mut self,
         host_lib: Option<Library>,
@@ -396,7 +371,7 @@ impl<'a, 'tcx> CrateLoader<'a, 'tcx> {
             self.sess.opts.externs.get(name.as_str()).map_or(false, |e| e.is_private_dep);
 
         // Claim this crate number and cache it
-        let cnum = self.cstore.alloc_new_crate_num();
+        let cnum = self.cstore.intern_stable_crate_id(&crate_root)?;
 
         info!(
             "register crate `{}` (cnum = {}. private_dep = {})",
@@ -432,14 +407,6 @@ impl<'a, 'tcx> CrateLoader<'a, 'tcx> {
             None
         };
 
-        // Perform some verification *after* resolve_crate_deps() above is
-        // known to have been successful. It seems that - in error cases - the
-        // cstore can be in a temporarily invalid state between cnum allocation
-        // and dependency resolution and the verification code would produce
-        // ICEs in that case (see #83045).
-        self.verify_no_symbol_conflicts(&crate_root)?;
-        self.verify_no_stable_crate_id_hash_conflicts(&crate_root, cnum)?;
-
         let crate_metadata = CrateMetadata::new(
             self.sess,
             &self.cstore,

compiler/rustc_metadata/src/rmeta/decoder.rs

@@ -1709,10 +1709,6 @@ impl CrateMetadata {
         self.root.name
     }
 
-    pub(crate) fn stable_crate_id(&self) -> StableCrateId {
-        self.root.stable_crate_id
-    }
-
     pub(crate) fn hash(&self) -> Svh {
         self.root.hash
     }

compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs

@@ -595,7 +595,10 @@ impl CrateStore for CStore {
     }
 
     fn stable_crate_id_to_crate_num(&self, stable_crate_id: StableCrateId) -> CrateNum {
-        self.stable_crate_ids[&stable_crate_id]
+        *self
+            .stable_crate_ids
+            .get(&stable_crate_id)
+            .unwrap_or_else(|| bug!("uninterned StableCrateId: {stable_crate_id:?}"))
     }
 
     /// Returns the `DefKey` for a given `DefId`. This indicates the

compiler/rustc_span/Cargo.toml

@@ -18,3 +18,4 @@ tracing = "0.1"
 sha1 = "0.10.0"
 sha2 = "0.10.1"
 md5 = { package = "md-5", version = "0.10.0" }
+indexmap = { version = "1.9.1" }

compiler/rustc_span/src/def_id.rs

@@ -1,13 +1,17 @@
 use crate::{HashStableContext, Symbol};
 use rustc_data_structures::fingerprint::Fingerprint;
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher, ToStableHashKey};
+use rustc_data_structures::unhash::Unhasher;
 use rustc_data_structures::AtomicRef;
 use rustc_index::vec::Idx;
 use rustc_macros::HashStable_Generic;
 use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
 use std::borrow::Borrow;
 use std::fmt;
-use std::hash::{Hash, Hasher};
+use std::hash::{BuildHasherDefault, Hash, Hasher};
+
+pub type StableCrateIdMap =
+    indexmap::IndexMap<StableCrateId, CrateNum, BuildHasherDefault<Unhasher>>;
 
 rustc_index::newtype_index! {
     #[custom_encodable]

tests/run-make-fulldeps/issue-83045/Makefile

@@ -29,5 +29,5 @@ all:
 				  --crate-type=rlib \
 				  --edition=2018 \
 				  c.rs 2>&1 | tee $(TMPDIR)/output.txt || exit 0
-	$(CGREP) E0463 < $(TMPDIR)/output.txt
+	$(CGREP) E0519 < $(TMPDIR)/output.txt
 	$(CGREP) -v "internal compiler error" < $(TMPDIR)/output.txt