Generalize initial "not const" assignments

Author: oli-obk

src/librustc_mir/transform/promote_consts.rs

@@ -44,8 +44,8 @@ pub enum TempState {
 impl TempState {
     pub fn is_promotable(&self) -> bool {
         debug!("is_promotable: self={:?}", self);
-        if let TempState::Defined { uses, .. } = *self {
-            uses > 0
+        if let TempState::Defined { .. } = *self {
+            true
         } else {
             false
         }
@@ -80,9 +80,14 @@ impl<'tcx> Visitor<'tcx> for TempCollector<'tcx> {
                    context: PlaceContext<'tcx>,
                    location: Location) {
         debug!("visit_local: index={:?} context={:?} location={:?}", index, context, location);
-        // We're only interested in temporaries
-        if self.mir.local_kind(index) != LocalKind::Temp {
-            return;
+        // We're only interested in temporaries and the return place
+        match self.mir.local_kind(index) {
+            | LocalKind::Temp
+            | LocalKind::ReturnPointer
+            => {},
+            | LocalKind::Arg
+            | LocalKind::Var
+            => return,
         }
 
         // Ignore drops, if the temp gets promoted,

src/librustc_mir/transform/qualify_consts.rs

@@ -631,26 +631,21 @@ impl<'a, 'tcx> Checker<'a, 'tcx> {
         };
 
         for (local, decl) in mir.local_decls.iter_enumerated() {
-            match mir.local_kind(local) {
-                LocalKind::Arg => {
-                    let qualifs = cx.qualifs_in_any_value_of_ty(decl.ty);
-                    for (per_local, qualif) in &mut cx.per_local.as_mut().zip(qualifs).0 {
-                        if *qualif {
-                            per_local.insert(local);
-                        }
+            if let LocalKind::Arg = mir.local_kind(local) {
+                let qualifs = cx.qualifs_in_any_value_of_ty(decl.ty);
+                for (per_local, qualif) in &mut cx.per_local.as_mut().zip(qualifs).0 {
+                    if *qualif {
+                        per_local.insert(local);
                     }
-                    cx.per_local[IsNotConst].insert(local);
-                }
-
-                LocalKind::Var if mode == Mode::Fn => {
-                    cx.per_local[IsNotConst].insert(local);
-                }
-
-                LocalKind::Temp if !temps[local].is_promotable() => {
-                    cx.per_local[IsNotConst].insert(local);
                 }
-
-                _ => {}
+            }
+            if !temps[local].is_promotable() {
+                cx.per_local[IsNotConst].insert(local);
+            }
+            if let LocalKind::Var = mir.local_kind(local) {
+                // Sanity check to prevent implicit and explicit promotion of
+                // named locals
+                assert!(cx.per_local[IsNotConst].contains(local));
             }
         }