Remove dependencies field of CrateMetadata

It is always identical to the list of values in cnum_map.

Author: bjorn3

compiler/rustc_metadata/src/creader.rs

@@ -719,7 +719,7 @@ impl CStore {
         self.used_extern_options.insert(name);
         match self.maybe_resolve_crate(tcx, name, dep_kind, origin) {
             Ok(cnum) => {
-                self.set_used_recursively(tcx, cnum);
+                self.set_used_recursively(cnum);
                 Some(cnum)
             }
             Err(err) => {

compiler/rustc_metadata/src/rmeta/decoder.rs

@@ -116,8 +116,6 @@ pub(crate) struct CrateMetadata {
     /// Maps crate IDs as they are were seen from this crate's compilation sessions into
     /// IDs as they are seen from the current compilation session.
     cnum_map: CrateNumMap,
-    /// Same ID set as `cnum_map` plus maybe some injected crates like panic runtime.
-    dependencies: Vec<CrateNum>,
     /// How to link (or not link) this crate to the currently compiled crate.
     dep_kind: CrateDepKind,
     /// Filesystem location of this crate.
@@ -1897,7 +1895,6 @@ impl CrateMetadata {
             .collect();
         let alloc_decoding_state =
             AllocDecodingState::new(root.interpret_alloc_index.decode(&blob).collect());
-        let dependencies = cnum_map.iter().copied().collect();
 
         // Pre-decode the DefPathHash->DefIndex table. This is a cheap operation
         // that does not copy any data. It just does some data verification.
@@ -1915,7 +1912,6 @@ impl CrateMetadata {
             alloc_decoding_state,
             cnum,
             cnum_map,
-            dependencies,
             dep_kind,
             source: Arc::new(source),
             private_dep,
@@ -1941,7 +1937,7 @@ impl CrateMetadata {
     }
 
     pub(crate) fn dependencies(&self) -> impl Iterator<Item = CrateNum> {
-        self.dependencies.iter().copied()
+        self.cnum_map.iter().copied()
     }
 
     pub(crate) fn target_modifiers(&self) -> TargetModifiers {

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

@@ -623,15 +623,15 @@ impl CStore {
         self.get_crate_data(cnum).get_proc_macro_quoted_span(tcx, id)
     }
 
-    pub fn set_used_recursively(&mut self, tcx: TyCtxt<'_>, cnum: CrateNum) {
+    pub fn set_used_recursively(&mut self, cnum: CrateNum) {
         let cmeta = self.get_crate_data_mut(cnum);
         if !cmeta.used {
             cmeta.used = true;
-            let dependencies = mem::take(&mut cmeta.dependencies);
-            for &dep_cnum in &dependencies {
-                self.set_used_recursively(tcx, dep_cnum);
+            let cnum_map = mem::take(&mut cmeta.cnum_map);
+            for &dep_cnum in cnum_map.iter() {
+                self.set_used_recursively(dep_cnum);
             }
-            self.get_crate_data_mut(cnum).dependencies = dependencies;
+            self.get_crate_data_mut(cnum).cnum_map = cnum_map;
         }
     }
 
@@ -663,11 +663,11 @@ impl CStore {
         if cmeta.update_extern_crate_diagnostics(extern_crate) {
             // Propagate the extern crate info to dependencies if it was updated.
             let extern_crate = ExternCrate { dependency_of: cnum, ..extern_crate };
-            let dependencies = mem::take(&mut cmeta.dependencies);
-            for &dep_cnum in &dependencies {
+            let cnum_map = mem::take(&mut cmeta.cnum_map);
+            for &dep_cnum in cnum_map.iter() {
                 self.update_transitive_extern_crate_diagnostics(dep_cnum, extern_crate);
             }
-            self.get_crate_data_mut(cnum).dependencies = dependencies;
+            self.get_crate_data_mut(cnum).cnum_map = cnum_map;
         }
     }
 }