Rollup merge of #63933 - wesleywiser:cleanup_from_move_promoted, r=oli-obk

Resolve some small issues related to #63580

This resolves some feedback left on #63580 after it was merged:

- Adds documentation to `mir::Static` and `mir::StaticKind`
- Simplifies `maybe_get_optimized_mir()` and `maybe_get_promoted_mir()`

cc @bjorn3 @RalfJung

src/librustc/mir/mod.rs

@@ -1733,6 +1733,10 @@ pub enum PlaceBase<'tcx> {
 pub struct Static<'tcx> {
     pub ty: Ty<'tcx>,
     pub kind: StaticKind<'tcx>,
+    /// The `DefId` of the item this static was declared in. For promoted values, usually, this is
+    /// the same as the `DefId` of the `mir::Body` containing the `Place` this promoted appears in.
+    /// However, after inlining, that might no longer be the case as inlined `Place`s are copied
+    /// into the calling frame.
     pub def_id: DefId,
 }
 
@@ -1740,6 +1744,9 @@ pub struct Static<'tcx> {
     Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash, HashStable, RustcEncodable, RustcDecodable,
 )]
 pub enum StaticKind<'tcx> {
+    /// Promoted references consist of an id (`Promoted`) and the substs necessary to monomorphize
+    /// it. Usually, these substs are just the identity substs for the item. However, the inliner
+    /// will adjust these substs when it inlines a function based on the substs at the callsite.
     Promoted(Promoted, SubstsRef<'tcx>),
     Static,
 }

src/librustc_metadata/cstore_impl.rs

@@ -125,24 +125,8 @@ provide! { <'tcx> tcx, def_id, other, cdata,
             bug!("coerce_unsized_info: `{:?}` is missing its info", def_id);
         })
     }
-    optimized_mir => {
-        let mir = cdata.maybe_get_optimized_mir(tcx, def_id.index).unwrap_or_else(|| {
-            bug!("get_optimized_mir: missing MIR for `{:?}`", def_id)
-        });
-
-        let mir = tcx.arena.alloc(mir);
-
-        mir
-    }
-    promoted_mir => {
-        let promoted = cdata.maybe_get_promoted_mir(tcx, def_id.index).unwrap_or_else(|| {
-            bug!("get_promoted_mir: missing promoted MIR for `{:?}`", def_id)
-        });
-
-        let promoted = tcx.arena.alloc(promoted);
-
-        promoted
-    }
+    optimized_mir => { tcx.arena.alloc(cdata.get_optimized_mir(tcx, def_id.index)) }
+    promoted_mir => { tcx.arena.alloc(cdata.get_promoted_mir(tcx, def_id.index)) }
     mir_const_qualif => {
         (cdata.mir_const_qualif(def_id.index), tcx.arena.alloc(BitSet::new_empty(0)))
     }

src/librustc_metadata/decoder.rs

@@ -450,11 +450,19 @@ impl<'a, 'tcx> CrateMetadata {
     pub fn is_proc_macro_crate(&self) -> bool {
         self.root.proc_macro_decls_static.is_some()
     }
+
     fn is_proc_macro(&self, id: DefIndex) -> bool {
         self.is_proc_macro_crate() &&
             self.root.proc_macro_data.unwrap().decode(self).find(|x| *x == id).is_some()
     }
 
+    fn entry_unless_proc_macro(&self, id: DefIndex) -> Option<Entry<'tcx>> {
+        match self.is_proc_macro(id) {
+            true => None,
+            false => Some(self.entry(id)),
+        }
+    }
+
     fn maybe_entry(&self, item_id: DefIndex) -> Option<Lazy<Entry<'tcx>>> {
         self.root.entries_index.lookup(self.blob.raw_bytes(), item_id)
     }
@@ -689,10 +697,8 @@ impl<'a, 'tcx> CrateMetadata {
     }
 
     pub fn get_deprecation(&self, id: DefIndex) -> Option<attr::Deprecation> {
-        match self.is_proc_macro(id) {
-            true => None,
-            false => self.entry(id).deprecation.map(|depr| depr.decode(self)),
-        }
+        self.entry_unless_proc_macro(id)
+            .and_then(|entry| entry.deprecation.map(|depr| depr.decode(self)))
     }
 
     pub fn get_visibility(&self, id: DefIndex) -> ty::Visibility {
@@ -902,22 +908,24 @@ impl<'a, 'tcx> CrateMetadata {
         self.maybe_entry(id).and_then(|item| item.decode(self).mir).is_some()
     }
 
-    pub fn maybe_get_optimized_mir(&self, tcx: TyCtxt<'tcx>, id: DefIndex) -> Option<Body<'tcx>> {
-        match self.is_proc_macro(id) {
-            true => None,
-            false => self.entry(id).mir.map(|mir| mir.decode((self, tcx))),
-        }
+    pub fn get_optimized_mir(&self, tcx: TyCtxt<'tcx>, id: DefIndex) -> Body<'tcx> {
+        self.entry_unless_proc_macro(id)
+            .and_then(|entry| entry.mir.map(|mir| mir.decode((self, tcx))))
+            .unwrap_or_else(|| {
+                bug!("get_optimized_mir: missing MIR for `{:?}", self.local_def_id(id))
+            })
     }
 
-    pub fn maybe_get_promoted_mir(
+    pub fn get_promoted_mir(
         &self,
         tcx: TyCtxt<'tcx>,
         id: DefIndex,
-    ) -> Option<IndexVec<Promoted, Body<'tcx>>> {
-        match self.is_proc_macro(id) {
-            true => None,
-            false => self.entry(id).promoted_mir.map(|promoted| promoted.decode((self, tcx)),)
-        }
+    ) -> IndexVec<Promoted, Body<'tcx>> {
+        self.entry_unless_proc_macro(id)
+            .and_then(|entry| entry.promoted_mir.map(|promoted| promoted.decode((self, tcx))))
+            .unwrap_or_else(|| {
+                bug!("get_promoted_mir: missing MIR for `{:?}`", self.local_def_id(id))
+            })
     }
 
     pub fn mir_const_qualif(&self, id: DefIndex) -> u8 {