Remove metadata_loader query

It is only used by CrateLoader. We can store the metadata loader in
CStore instead which CrateLoader has access to.

compiler/rustc_interface/src/queries.rs

@@ -193,7 +193,10 @@ impl<'tcx> Queries<'tcx> {
                 self.compiler.register_lints.as_deref(),
                 &pre_configured_attrs,
             ));
-            let cstore = RwLock::new(Box::new(CStore::new(stable_crate_id)) as _);
+            let cstore = RwLock::new(Box::new(CStore::new(
+                self.codegen_backend().metadata_loader(),
+                stable_crate_id,
+            )) as _);
             let definitions = RwLock::new(Definitions::new(stable_crate_id));
             let source_span = AppendOnlyIndexVec::new();
             let _id = source_span.push(krate.spans.inner_span);
@@ -221,9 +224,6 @@ impl<'tcx> Queries<'tcx> {
                     tcx.arena.alloc(rustc_expand::config::features(sess, &pre_configured_attrs)),
                 );
                 feed.crate_for_resolver(tcx.arena.alloc(Steal::new((krate, pre_configured_attrs))));
-                feed.metadata_loader(
-                    tcx.arena.alloc(Steal::new(self.codegen_backend().metadata_loader())),
-                );
             });
             Ok(qcx)
         })

compiler/rustc_metadata/src/creader.rs

@@ -15,8 +15,9 @@ use rustc_hir::definitions::Definitions;
 use rustc_index::IndexVec;
 use rustc_middle::ty::TyCtxt;
 use rustc_session::config::{self, CrateType, ExternLocation};
-use rustc_session::cstore::ExternCrateSource;
+use rustc_session::cstore::{
-use rustc_session::cstore::{CrateDepKind, CrateSource, ExternCrate};
+    CrateDepKind, CrateSource, ExternCrate, ExternCrateSource, MetadataLoaderDyn,
+};
 use rustc_session::lint;
 use rustc_session::output::validate_crate_name;
 use rustc_session::search_paths::PathKind;
@@ -33,6 +34,8 @@ use std::time::Duration;
 use std::{cmp, env, iter};
 
 pub struct CStore {
+    metadata_loader: Box<MetadataLoaderDyn>,
+
     metas: IndexVec<CrateNum, Option<Box<CrateMetadata>>>,
     injected_panic_runtime: Option<CrateNum>,
     /// This crate needs an allocator and either provides it itself, or finds it in a dependency.
@@ -261,10 +264,14 @@ impl CStore {
         }
     }
 
-    pub fn new(local_stable_crate_id: StableCrateId) -> CStore {
+    pub fn new(
+        metadata_loader: Box<MetadataLoaderDyn>,
+        local_stable_crate_id: StableCrateId,
+    ) -> CStore {
         let mut stable_crate_ids = StableCrateIdMap::default();
         stable_crate_ids.insert(local_stable_crate_id, LOCAL_CRATE);
         CStore {
+            metadata_loader,
             // We add an empty entry for LOCAL_CRATE (which maps to zero) in
             // order to make array indices in `metas` match with the
             // corresponding `CrateNum`. This first entry will always remain
@@ -538,10 +545,9 @@ impl<'a, 'tcx> CrateLoader<'a, 'tcx> {
             (LoadResult::Previous(cnum), None)
         } else {
             info!("falling back to a load");
-            let metadata_loader = self.tcx.metadata_loader(()).borrow();
             let mut locator = CrateLocator::new(
                 self.sess,
-                &**metadata_loader,
+                &*self.cstore.metadata_loader,
                 name,
                 // The all loop is because `--crate-type=rlib --crate-type=rlib` is
                 // legal and produces both inside this type.

compiler/rustc_middle/src/arena.rs

@@ -40,7 +40,6 @@ macro_rules! arena_types {
                 rustc_data_structures::sync::Lrc<rustc_ast::Crate>,
             )>,
             [] output_filenames: std::sync::Arc<rustc_session::config::OutputFilenames>,
-            [] metadata_loader: rustc_data_structures::steal::Steal<Box<rustc_session::cstore::MetadataLoaderDyn>>,
             [] crate_for_resolver: rustc_data_structures::steal::Steal<(rustc_ast::Crate, rustc_ast::AttrVec)>,
             [] resolutions: rustc_middle::ty::ResolverGlobalCtxt,
             [decode] unsafety_check_result: rustc_middle::mir::UnsafetyCheckResult,

compiler/rustc_middle/src/query/mod.rs

@@ -2096,12 +2096,6 @@ rustc_queries! {
         desc { "looking up enabled feature gates" }
     }
 
-    query metadata_loader((): ()) -> &'tcx Steal<Box<rustc_session::cstore::MetadataLoaderDyn>> {
-        feedable
-        no_hash
-        desc { "raw operations for metadata file access" }
-    }
-
     query crate_for_resolver((): ()) -> &'tcx Steal<(rustc_ast::Crate, rustc_ast::AttrVec)> {
         feedable
         no_hash