Place 2.0 change from enum to struct

src/librustc/mir/mod.rs

@@ -1718,11 +1718,11 @@ impl<'tcx> Debug for Statement<'tcx> {
 #[derive(
     Clone, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable, HashStable,
 )]
-pub enum Place<'tcx> {
-    Base(PlaceBase<'tcx>),
+pub struct Place<'tcx> {
+    pub base: PlaceBase<'tcx>,
 
     /// projection out of a place (access a field, deref a pointer, etc)
-    Projection(Box<Projection<'tcx>>),
+    pub projection: Option<Box<Projection<'tcx>>>,
 }
 
 #[derive(
@@ -1761,7 +1761,7 @@ impl_stable_hash_for!(struct Static<'tcx> {
     Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable, HashStable,
 )]
 pub struct Projection<'tcx> {
-    pub base: Place<'tcx>,
+    pub base: Option<Box<Projection<'tcx>>>,
     pub elem: PlaceElem<'tcx>,
 }
 
@@ -1826,8 +1826,17 @@ newtype_index! {
     }
 }
 
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct PlaceRef<'a, 'tcx> {
+    pub base: &'a PlaceBase<'tcx>,
+    pub projection: &'a Option<Box<Projection<'tcx>>>,
+}
+
 impl<'tcx> Place<'tcx> {
-    pub const RETURN_PLACE: Place<'tcx> = Place::Base(PlaceBase::Local(RETURN_PLACE));
+    pub const RETURN_PLACE: Place<'tcx> = Place {
+        base: PlaceBase::Local(RETURN_PLACE),
+        projection: None,
+    };
 
     pub fn field(self, f: Field, ty: Ty<'tcx>) -> Place<'tcx> {
         self.elem(ProjectionElem::Field(f, ty))
@@ -1853,7 +1862,10 @@ impl<'tcx> Place<'tcx> {
     }
 
     pub fn elem(self, elem: PlaceElem<'tcx>) -> Place<'tcx> {
-        Place::Projection(Box::new(Projection { base: self, elem }))
+        Place {
+            base: self.base,
+            projection: Some(Box::new(Projection { base: self.projection, elem })),
+        }
     }
 
     /// Finds the innermost `Local` from this `Place`, *if* it is either a local itself or
@@ -1862,54 +1874,77 @@ impl<'tcx> Place<'tcx> {
     // FIXME: can we safely swap the semantics of `fn base_local` below in here instead?
     pub fn local_or_deref_local(&self) -> Option<Local> {
         match self {
-            Place::Base(PlaceBase::Local(local))
-            | Place::Projection(box Projection {
-                base: Place::Base(PlaceBase::Local(local)),
-                elem: ProjectionElem::Deref,
-            }) => Some(*local),
+            Place {
+                base: PlaceBase::Local(local),
+                projection: None,
+            } |
+            Place {
+                base: PlaceBase::Local(local),
+                projection: Some(box Projection {
+                    base: None,
+                    elem: ProjectionElem::Deref,
+                }),
+            } => Some(*local),
             _ => None,
         }
     }
 
-    /// Finds the innermost `Local` from this `Place`.
-    pub fn base_local(&self) -> Option<Local> {
-        let mut place = self;
-        loop {
-            match place {
-                Place::Projection(proj) => place = &proj.base,
-                Place::Base(PlaceBase::Static(_)) => return None,
-                Place::Base(PlaceBase::Local(local)) => return Some(*local),
-            }
-        }
-    }
-
     /// Recursively "iterates" over place components, generating a `PlaceBase` and
     /// `Projections` list and invoking `op` with a `ProjectionsIter`.
     pub fn iterate<R>(
         &self,
         op: impl FnOnce(&PlaceBase<'tcx>, ProjectionsIter<'_, 'tcx>) -> R,
     ) -> R {
-        self.iterate2(&Projections::Empty, op)
+        Place::iterate_over(&self.base, &self.projection, op)
     }
 
-    fn iterate2<R>(
-        &self,
-        next: &Projections<'_, 'tcx>,
+    pub fn iterate_over<R>(
+        place_base: &PlaceBase<'tcx>,
+        place_projection: &Option<Box<Projection<'tcx>>>,
         op: impl FnOnce(&PlaceBase<'tcx>, ProjectionsIter<'_, 'tcx>) -> R,
     ) -> R {
-        match self {
-            Place::Projection(interior) => {
-                interior.base.iterate2(&Projections::List { projection: interior, next }, op)
+        fn iterate_over2<'tcx, R>(
+            place_base: &PlaceBase<'tcx>,
+            place_projection: &Option<Box<Projection<'tcx>>>,
+            next: &Projections<'_, 'tcx>,
+            op: impl FnOnce(&PlaceBase<'tcx>, ProjectionsIter<'_, 'tcx>) -> R,
+        ) -> R {
+            match place_projection {
+                None => {
+                    op(place_base, next.iter())
+                }
+
+                Some(interior) => {
+                    iterate_over2(
+                        place_base,
+                        &interior.base,
+                        &Projections::List {
+                            projection: interior,
+                            next,
+                        },
+                        op,
+                    )
+                }
             }
+        }
 
-            Place::Base(base) => op(base, next.iter()),
+        iterate_over2(place_base, place_projection, &Projections::Empty, op)
+    }
+
+    pub fn as_place_ref(&self) -> PlaceRef<'_, 'tcx> {
+        PlaceRef {
+            base: &self.base,
+            projection: &self.projection,
         }
     }
 }
 
 impl From<Local> for Place<'_> {
     fn from(local: Local) -> Self {
-        Place::Base(local.into())
+        Place {
+            base: local.into(),
+            projection: None,
+        }
     }
 }
 
@@ -1919,6 +1954,36 @@ impl From<Local> for PlaceBase<'_> {
     }
 }
 
+impl<'a, 'tcx> PlaceRef<'a, 'tcx> {
+    pub fn iterate<R>(
+        &self,
+        op: impl FnOnce(&PlaceBase<'tcx>, ProjectionsIter<'_, 'tcx>) -> R,
+    ) -> R {
+        Place::iterate_over(self.base, self.projection, op)
+    }
+
+    /// Finds the innermost `Local` from this `Place`, *if* it is either a local itself or
+    /// a single deref of a local.
+    //
+    // FIXME: can we safely swap the semantics of `fn base_local` below in here instead?
+    pub fn local_or_deref_local(&self) -> Option<Local> {
+        match self {
+            PlaceRef {
+                base: PlaceBase::Local(local),
+                projection: None,
+            } |
+            PlaceRef {
+                base: PlaceBase::Local(local),
+                projection: Some(box Projection {
+                    base: None,
+                    elem: ProjectionElem::Deref,
+                }),
+            } => Some(*local),
+            _ => None,
+        }
+    }
+}
+
 /// A linked list of projections running up the stack; begins with the
 /// innermost projection and extends to the outermost (e.g., `a.b.c`
 /// would have the place `b` with a "next" pointer to `b.c`).
@@ -3155,18 +3220,14 @@ impl<'tcx> TypeFoldable<'tcx> for Terminator<'tcx> {
 
 impl<'tcx> TypeFoldable<'tcx> for Place<'tcx> {
     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
-        match self {
-            &Place::Projection(ref p) => Place::Projection(p.fold_with(folder)),
-            _ => self.clone(),
+        Place {
+            base: self.base.clone(),
+            projection: self.projection.fold_with(folder),
         }
     }
 
     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
-        if let &Place::Projection(ref p) = self {
-            p.visit_with(visitor)
-        } else {
-            false
-        }
+        self.projection.visit_with(visitor)
     }
 }
 

src/librustc/mir/tcx.rs

@@ -118,11 +118,15 @@ BraceStructTypeFoldableImpl! {
 }
 
 impl<'tcx> Place<'tcx> {
-    pub fn ty<D>(&self, local_decls: &D, tcx: TyCtxt<'tcx>) -> PlaceTy<'tcx>
-    where
-        D: HasLocalDecls<'tcx>,
+    pub fn ty_from<D>(
+        base: &PlaceBase<'tcx>,
+        projection: &Option<Box<Projection<'tcx>>>,
+        local_decls: &D,
+        tcx: TyCtxt<'tcx>
+    ) -> PlaceTy<'tcx>
+        where D: HasLocalDecls<'tcx>
     {
-        self.iterate(|place_base, place_projections| {
+        Place::iterate_over(base, projection, |place_base, place_projections| {
             let mut place_ty = place_base.ty(local_decls);
 
             for proj in place_projections {
@@ -132,6 +136,13 @@ impl<'tcx> Place<'tcx> {
             place_ty
         })
     }
+
+    pub fn ty<D>(&self, local_decls: &D, tcx: TyCtxt<'tcx>) -> PlaceTy<'tcx>
+    where
+        D: HasLocalDecls<'tcx>,
+    {
+        Place::ty_from(&self.base, &self.projection, local_decls, tcx)
+    }
 }
 
 impl<'tcx> PlaceBase<'tcx> {

src/librustc/mir/visit.rs

@@ -159,10 +159,11 @@ macro_rules! make_mir_visitor {
             }
 
             fn visit_projection(&mut self,
+                                place_base: & $($mutability)? PlaceBase<'tcx>,
                                 place: & $($mutability)? Projection<'tcx>,
                                 context: PlaceContext,
                                 location: Location) {
-                self.super_projection(place, context, location);
+                self.super_projection(place_base, place, context, location);
             }
 
             fn visit_constant(&mut self,
@@ -676,19 +677,20 @@ macro_rules! make_mir_visitor {
                             place: & $($mutability)? Place<'tcx>,
                             context: PlaceContext,
                             location: Location) {
-                match place {
-                    Place::Base(place_base) => {
-                        self.visit_place_base(place_base, context, location);
-                    }
-                    Place::Projection(proj) => {
-                        let context = if context.is_mutating_use() {
-                            PlaceContext::MutatingUse(MutatingUseContext::Projection)
-                        } else {
-                            PlaceContext::NonMutatingUse(NonMutatingUseContext::Projection)
-                        };
+                let mut context = context;
+
+                if place.projection.is_some() {
+                    context = if context.is_mutating_use() {
+                        PlaceContext::MutatingUse(MutatingUseContext::Projection)
+                    } else {
+                        PlaceContext::NonMutatingUse(NonMutatingUseContext::Projection)
+                    };
+                }
 
-                        self.visit_projection(proj, context, location);
-                    }
+                self.visit_place_base(& $($mutability)? place.base, context, location);
+
+                if let Some(box proj) = & $($mutability)? place.projection {
+                    self.visit_projection(& $($mutability)? place.base, proj, context, location);
                 }
             }
 
@@ -707,13 +709,14 @@ macro_rules! make_mir_visitor {
             }
 
             fn super_projection(&mut self,
+                                place_base: & $($mutability)? PlaceBase<'tcx>,
                                 proj: & $($mutability)? Projection<'tcx>,
                                 context: PlaceContext,
                                 location: Location) {
-                // this is calling `super_place` in preparation for changing `Place` to be
-                // a struct with a base and a slice of projections. `visit_place` should only ever
-                // be called for the outermost place now.
-                self.super_place(& $($mutability)? proj.base, context, location);
+                if let Some(box proj_base) = & $($mutability)? proj.base {
+                    self.visit_projection(place_base, proj_base, context, location);
+                }
+
                 match & $($mutability)? proj.elem {
                     ProjectionElem::Deref => {
                     }