rustc_metadata: Give decoder access to whole crate store

src/librustc_metadata/creader.rs

@@ -76,6 +76,21 @@ fn report(self) -> ! {
     }
 }
 
+/// A reference to `CrateMetadata` that can also give access to whole crate store when necessary.
+#[derive(Clone, Copy)]
+crate struct CrateMetadataRef<'a> {
+    pub cdata: &'a CrateMetadata,
+    pub cstore: &'a CStore,
+}
+
+impl std::ops::Deref for CrateMetadataRef<'_> {
+    type Target = CrateMetadata;
+
+    fn deref(&self) -> &Self::Target {
+        self.cdata
+    }
+}
+
 fn dump_crates(cstore: &CStore) {
     info!("resolved crates:");
     cstore.iter_crate_data(|cnum, data| {
@@ -100,10 +115,11 @@ fn alloc_new_crate_num(&mut self) -> CrateNum {
         CrateNum::new(self.metas.len() - 1)
     }
 
-    crate fn get_crate_data(&self, cnum: CrateNum) -> &CrateMetadata {
-        self.metas[cnum]
+    crate fn get_crate_data(&self, cnum: CrateNum) -> CrateMetadataRef<'_> {
+        let cdata = self.metas[cnum]
             .as_ref()
-            .unwrap_or_else(|| panic!("Failed to get crate data for {:?}", cnum))
+            .unwrap_or_else(|| panic!("Failed to get crate data for {:?}", cnum));
+        CrateMetadataRef { cdata, cstore: self }
     }
 
     fn set_crate_data(&mut self, cnum: CrateNum, data: CrateMetadata) {
@@ -217,7 +233,7 @@ fn existing_match(&self, name: Symbol, hash: Option<Svh>, kind: PathKind) -> Opt
             // We're also sure to compare *paths*, not actual byte slices. The
             // `source` stores paths which are normalized which may be different
             // from the strings on the command line.
-            let source = self.cstore.get_crate_data(cnum).source();
+            let source = self.cstore.get_crate_data(cnum).cdata.source();
             if let Some(entry) = self.sess.opts.externs.get(&name.as_str()) {
                 // Only use `--extern crate_name=path` here, not `--extern crate_name`.
                 if let Some(mut files) = entry.files() {

src/librustc_metadata/rmeta/decoder.rs

 // Decoding metadata from a single crate's metadata
 
+use crate::creader::CrateMetadataRef;
 use crate::rmeta::table::{FixedSizeEncoding, Table};
 use crate::rmeta::*;
 
@@ -125,7 +126,7 @@ struct ImportedSourceFile {
 
 pub(super) struct DecodeContext<'a, 'tcx> {
     opaque: opaque::Decoder<'a>,
-    cdata: Option<&'a CrateMetadata>,
+    cdata: Option<CrateMetadataRef<'a>>,
     sess: Option<&'tcx Session>,
     tcx: Option<TyCtxt<'tcx>>,
 
@@ -141,7 +142,7 @@ pub(super) struct DecodeContext<'a, 'tcx> {
 /// Abstract over the various ways one can create metadata decoders.
 pub(super) trait Metadata<'a, 'tcx>: Copy {
     fn raw_bytes(self) -> &'a [u8];
-    fn cdata(self) -> Option<&'a CrateMetadata> {
+    fn cdata(self) -> Option<CrateMetadataRef<'a>> {
         None
     }
     fn sess(self) -> Option<&'tcx Session> {
@@ -162,7 +163,7 @@ fn decoder(self, pos: usize) -> DecodeContext<'a, 'tcx> {
             lazy_state: LazyState::NoNode,
             alloc_decoding_session: self
                 .cdata()
-                .map(|cdata| cdata.alloc_decoding_state.new_decoding_session()),
+                .map(|cdata| cdata.cdata.alloc_decoding_state.new_decoding_session()),
         }
     }
 }
@@ -185,33 +186,33 @@ fn sess(self) -> Option<&'tcx Session> {
     }
 }
 
-impl<'a, 'tcx> Metadata<'a, 'tcx> for &'a CrateMetadata {
+impl<'a, 'tcx> Metadata<'a, 'tcx> for &'a CrateMetadataRef<'a> {
     fn raw_bytes(self) -> &'a [u8] {
         self.blob.raw_bytes()
     }
-    fn cdata(self) -> Option<&'a CrateMetadata> {
-        Some(self)
+    fn cdata(self) -> Option<CrateMetadataRef<'a>> {
+        Some(*self)
     }
 }
 
-impl<'a, 'tcx> Metadata<'a, 'tcx> for (&'a CrateMetadata, &'tcx Session) {
+impl<'a, 'tcx> Metadata<'a, 'tcx> for (&'a CrateMetadataRef<'a>, &'tcx Session) {
     fn raw_bytes(self) -> &'a [u8] {
         self.0.raw_bytes()
     }
-    fn cdata(self) -> Option<&'a CrateMetadata> {
-        Some(self.0)
+    fn cdata(self) -> Option<CrateMetadataRef<'a>> {
+        Some(*self.0)
     }
     fn sess(self) -> Option<&'tcx Session> {
         Some(&self.1)
     }
 }
 
-impl<'a, 'tcx> Metadata<'a, 'tcx> for (&'a CrateMetadata, TyCtxt<'tcx>) {
+impl<'a, 'tcx> Metadata<'a, 'tcx> for (&'a CrateMetadataRef<'a>, TyCtxt<'tcx>) {
     fn raw_bytes(self) -> &'a [u8] {
         self.0.raw_bytes()
     }
-    fn cdata(self) -> Option<&'a CrateMetadata> {
-        Some(self.0)
+    fn cdata(self) -> Option<CrateMetadataRef<'a>> {
+        Some(*self.0)
     }
     fn tcx(self) -> Option<TyCtxt<'tcx>> {
         Some(self.1)
@@ -242,7 +243,7 @@ fn tcx(&self) -> TyCtxt<'tcx> {
         self.tcx.expect("missing TyCtxt in DecodeContext")
     }
 
-    fn cdata(&self) -> &'a CrateMetadata {
+    fn cdata(&self) -> CrateMetadataRef<'a> {
         self.cdata.expect("missing CrateMetadata in DecodeContext")
     }
 
@@ -558,7 +559,7 @@ impl CrateRoot<'_> {
     }
 }
 
-impl<'a, 'tcx> CrateMetadata {
+impl CrateMetadata {
     crate fn new(
         sess: &Session,
         blob: MetadataBlob,
@@ -601,7 +602,9 @@ impl<'a, 'tcx> CrateMetadata {
             extern_crate: Lock::new(None),
         }
     }
+}
 
+impl<'a, 'tcx> CrateMetadataRef<'a> {
     fn is_proc_macro(&self, id: DefIndex) -> bool {
         self.root.proc_macro_data.and_then(|data| data.decode(self).find(|x| *x == id)).is_some()
     }
@@ -1440,10 +1443,10 @@ fn def_path_hash(&self, index: DefIndex) -> DefPathHash {
     /// Proc macro crates don't currently export spans, so this function does not have
     /// to work for them.
     fn imported_source_files(
-        &'a self,
+        &self,
         local_source_map: &source_map::SourceMap,
-    ) -> &[ImportedSourceFile] {
-        self.source_map_import_info.init_locking(|| {
+    ) -> &'a [ImportedSourceFile] {
+        self.cdata.source_map_import_info.init_locking(|| {
             let external_source_map = self.root.source_map.decode(self);
 
             external_source_map
@@ -1540,7 +1543,9 @@ fn get_crate_dep_node_index(&self, tcx: TyCtxt<'tcx>) -> DepNodeIndex {
 
         dep_node_index
     }
+}
 
+impl CrateMetadata {
     crate fn dependencies(&self) -> LockGuard<'_, Vec<CrateNum>> {
         self.dependencies.borrow()
     }

src/librustc_metadata/rmeta/decoder/cstore_impl.rs

@@ -517,7 +517,7 @@ fn def_path_hash(&self, def: DefId) -> DefPathHash {
     }
 
     fn def_path_table(&self, cnum: CrateNum) -> &DefPathTable {
-        &self.get_crate_data(cnum).def_path_table
+        &self.get_crate_data(cnum).cdata.def_path_table
     }
 
     fn crates_untracked(&self) -> Vec<CrateNum> {