Rollup merge of rust-lang#65197 - spastorino:place-mut-visitor-adjust…

…s2, r=oli-obk

Prepare `MutVisitor`s to handle interned projections

The following are all the files where mir's `MutVisitor` is implemented. The `-` there stands for no changes, `visit_place` wasn't making any change on `Place`s. `x` stands for this file was changed to make `visit_place` do whatever it was doing with the base but avoid modifying the projection, instead just create a new one and assign to it.

```
[-] src/librustc_mir/transform/no_landing_pads.rs
[x] src/librustc_mir/transform/promote_consts.rs
[x] src/librustc_mir/transform/generator.rs
[x] src/librustc_mir/transform/erase_regions.rs
[-] src/librustc_mir/transform/instcombine.rs
[x] src/librustc_mir/transform/inline.rs
[x] src/librustc_mir/transform/simplify.rs
[x] src/librustc_mir/util/def_use.rs
[-] src/librustc_mir/transform/const_prop.rs
[-] src/librustc_mir/transform/cleanup_post_borrowck.rs
[x] src/librustc_mir/borrow_check/nll/renumber.rs
[-] src/librustc_mir/transform/copy_prop.rs
```

There is some code repetition, just created the PR so we can start discussing it.

/cc @oli-obk @nikomatsakis

src/librustc/mir/visit.rs

@@ -158,22 +158,7 @@ macro_rules! make_mir_visitor {
  self.super_place_base(base, context, location);
  }
 
- fn visit_projection(&mut self,
- base: & $($mutability)? PlaceBase<'tcx>,
- projection: & $($mutability)? [PlaceElem<'tcx>],
- context: PlaceContext,
- location: Location) {
- self.super_projection(base, projection, context, location);
- }
-
- fn visit_projection_elem(&mut self,
- base: & $($mutability)? PlaceBase<'tcx>,
- proj_base: & $($mutability)? [PlaceElem<'tcx>],
- elem: & $($mutability)? PlaceElem<'tcx>,
- context: PlaceContext,
- location: Location) {
- self.super_projection_elem(base, proj_base, elem, context, location);
- }
+ visit_place_fns!($($mutability)?);
 
  fn visit_constant(&mut self,
  constant: & $($mutability)? Constant<'tcx>,
@@ -681,28 +666,6 @@ macro_rules! make_mir_visitor {
  );
  }
 
- fn super_place(&mut self,
- place: & $($mutability)? Place<'tcx>,
- context: PlaceContext,
- location: Location) {
- let mut context = context;
-
- if !place.projection.is_empty() {
- context = if context.is_mutating_use() {
- PlaceContext::MutatingUse(MutatingUseContext::Projection)
- } else {
- PlaceContext::NonMutatingUse(NonMutatingUseContext::Projection)
- };
- }
-
- self.visit_place_base(& $($mutability)? place.base, context, location);
-
- self.visit_projection(& $($mutability)? place.base,
- & $($mutability)? place.projection,
- context,
- location);
- }
-
  fn super_place_base(&mut self,
  place_base: & $($mutability)? PlaceBase<'tcx>,
  context: PlaceContext,
@@ -717,45 +680,6 @@ macro_rules! make_mir_visitor {
  }
  }
 
- fn super_projection(&mut self,
- base: & $($mutability)? PlaceBase<'tcx>,
- projection: & $($mutability)? [PlaceElem<'tcx>],
- context: PlaceContext,
- location: Location) {
- let mut cursor = projection;
- while let [proj_base @ .., elem] = cursor {
- cursor = proj_base;
- self.visit_projection_elem(base, cursor, elem, context, location);
- }
- }
-
- fn super_projection_elem(&mut self,
- _base: & $($mutability)? PlaceBase<'tcx>,
- _proj_base: & $($mutability)? [PlaceElem<'tcx>],
- elem: & $($mutability)? PlaceElem<'tcx>,
- _context: PlaceContext,
- location: Location) {
- match elem {
- ProjectionElem::Field(_field, ty) => {
- self.visit_ty(ty, TyContext::Location(location));
- }
- ProjectionElem::Index(local) => {
- self.visit_local(
- local,
- PlaceContext::NonMutatingUse(NonMutatingUseContext::Copy),
- location
- );
- }
- ProjectionElem::Deref |
- ProjectionElem::Subslice { from: _, to: _ } |
- ProjectionElem::ConstantIndex { offset: _,
- min_length: _,
- from_end: _ } |
- ProjectionElem::Downcast(_, _) => {
- }
- }
- }
-
  fn super_local_decl(&mut self,
  local: Local,
  local_decl: & $($mutability)? LocalDecl<'tcx>) {
@@ -858,6 +782,141 @@ macro_rules! make_mir_visitor {
  }
 }
 
+macro_rules! visit_place_fns {
+ (mut) => (
+ fn super_place(
+ &mut self,
+ place: &mut Place<'tcx>,
+ context: PlaceContext,
+ location: Location,
+ ) {
+ self.visit_place_base(&mut place.base, context, location);
+
+ if let Some(new_projection) = self.process_projection(&place.projection) {
+ place.projection = new_projection;
+ }
+ }
+
+ fn process_projection(
+ &mut self,
+ projection: &'a [PlaceElem<'tcx>],
+ ) -> Option<Box<[PlaceElem<'tcx>]>> {
+ let mut projection = Cow::Borrowed(projection);
+
+ for i in 0..projection.len() {
+ if let Some(elem) = projection.get(i) {
+ if let Some(elem) = self.process_projection_elem(elem) {
+ let vec = projection.to_mut();
+ vec[i] = elem;
+ }
+ }
+ }
+
+ match projection {
+ Cow::Borrowed(_) => None,
+ Cow::Owned(vec) => Some(vec.into_boxed_slice()),
+ }
+ }
+
+ fn process_projection_elem(
+ &mut self,
+ _elem: &PlaceElem<'tcx>,
+ ) -> Option<PlaceElem<'tcx>> {
+ None
+ }
+ );
+
+ () => (
+ fn visit_projection(
+ &mut self,
+ base: &PlaceBase<'tcx>,
+ projection: &[PlaceElem<'tcx>],
+ context: PlaceContext,
+ location: Location,
+ ) {
+ self.super_projection(base, projection, context, location);
+ }
+
+ fn visit_projection_elem(
+ &mut self,
+ base: &PlaceBase<'tcx>,
+ proj_base: &[PlaceElem<'tcx>],
+ elem: &PlaceElem<'tcx>,
+ context: PlaceContext,
+ location: Location,
+ ) {
+ self.super_projection_elem(base, proj_base, elem, context, location);
+ }
+
+ fn super_place(
+ &mut self,
+ place: &Place<'tcx>,
+ context: PlaceContext,
+ location: Location,
+ ) {
+ let mut context = context;
+
+ if !place.projection.is_empty() {
+ context = if context.is_mutating_use() {
+ PlaceContext::MutatingUse(MutatingUseContext::Projection)
+ } else {
+ PlaceContext::NonMutatingUse(NonMutatingUseContext::Projection)
+ };
+ }
+
+ self.visit_place_base(&place.base, context, location);
+
+ self.visit_projection(&place.base,
+ &place.projection,
+ context,
+ location);
+ }
+
+ fn super_projection(
+ &mut self,
+ base: &PlaceBase<'tcx>,
+ projection: &[PlaceElem<'tcx>],
+ context: PlaceContext,
+ location: Location,
+ ) {
+ let mut cursor = projection;
+ while let [proj_base @ .., elem] = cursor {
+ cursor = proj_base;
+ self.visit_projection_elem(base, cursor, elem, context, location);
+ }
+ }
+
+ fn super_projection_elem(
+ &mut self,
+ _base: &PlaceBase<'tcx>,
+ _proj_base: &[PlaceElem<'tcx>],
+ elem: &PlaceElem<'tcx>,
+ _context: PlaceContext,
+ location: Location,
+ ) {
+ match elem {
+ ProjectionElem::Field(_field, ty) => {
+ self.visit_ty(ty, TyContext::Location(location));
+ }
+ ProjectionElem::Index(local) => {
+ self.visit_local(
+ local,
+ PlaceContext::NonMutatingUse(NonMutatingUseContext::Copy),
+ location
+ );
+ }
+ ProjectionElem::Deref |
+ ProjectionElem::Subslice { from: _, to: _ } |
+ ProjectionElem::ConstantIndex { offset: _,
+ min_length: _,
+ from_end: _ } |
+ ProjectionElem::Downcast(_, _) => {
+ }
+ }
+ }
+ );
+}
+
 make_mir_visitor!(Visitor,);
 make_mir_visitor!(MutVisitor,mut);
 

src/librustc_mir/borrow_check/nll/renumber.rs

@@ -1,6 +1,6 @@
 use rustc::ty::subst::SubstsRef;
 use rustc::ty::{self, Ty, TypeFoldable};
-use rustc::mir::{Location, Body, Promoted};
+use rustc::mir::{Body, Location, PlaceElem, Promoted};
 use rustc::mir::visit::{MutVisitor, TyContext};
 use rustc::infer::{InferCtxt, NLLRegionVariableOrigin};
 use rustc_index::vec::IndexVec;
@@ -62,6 +62,21 @@ impl<'a, 'tcx> MutVisitor<'tcx> for NLLVisitor<'a, 'tcx> {
  debug!("visit_ty: ty={:?}", ty);
  }
 
+ fn process_projection_elem(
+ &mut self,
+ elem: &PlaceElem<'tcx>,
+ ) -> Option<PlaceElem<'tcx>> {
+ if let PlaceElem::Field(field, ty) = elem {
+ let new_ty = self.renumber_regions(ty);
+
+ if new_ty != *ty {
+ return Some(PlaceElem::Field(*field, new_ty));
+ }
+ }
+
+ None
+ }
+
  fn visit_substs(&mut self, substs: &mut SubstsRef<'tcx>, location: Location) {
  debug!("visit_substs(substs={:?}, location={:?})", substs, location);
 

src/librustc_mir/transform/erase_regions.rs

@@ -25,7 +25,6 @@ impl EraseRegionsVisitor<'tcx> {
 impl MutVisitor<'tcx> for EraseRegionsVisitor<'tcx> {
  fn visit_ty(&mut self, ty: &mut Ty<'tcx>, _: TyContext) {
  *ty = self.tcx.erase_regions(ty);
- self.super_ty(ty);
  }
 
  fn visit_region(&mut self, region: &mut ty::Region<'tcx>, _: Location) {
@@ -39,6 +38,21 @@ impl MutVisitor<'tcx> for EraseRegionsVisitor<'tcx> {
  fn visit_substs(&mut self, substs: &mut SubstsRef<'tcx>, _: Location) {
  *substs = self.tcx.erase_regions(substs);
  }
+
+ fn process_projection_elem(
+ &mut self,
+ elem: &PlaceElem<'tcx>,
+ ) -> Option<PlaceElem<'tcx>> {
+ if let PlaceElem::Field(field, ty) = elem {
+ let new_ty = self.tcx.erase_regions(ty);
+
+ if new_ty != *ty {
+ return Some(PlaceElem::Field(*field, new_ty));
+ }
+ }
+
+ None
+ }
 }
 
 pub struct EraseRegions;

src/librustc_mir/transform/generator.rs

@@ -88,6 +88,18 @@ impl<'tcx> MutVisitor<'tcx> for RenameLocalVisitor {
  *local = self.to;
  }
  }
+
+ fn process_projection_elem(
+ &mut self,
+ elem: &PlaceElem<'tcx>,
+ ) -> Option<PlaceElem<'tcx>> {
+ match elem {
+ PlaceElem::Index(local) if *local == self.from => {
+ Some(PlaceElem::Index(self.to))
+ }
+ _ => None,
+ }
+ }
 }
 
 struct DerefArgVisitor;
@@ -110,7 +122,13 @@ impl<'tcx> MutVisitor<'tcx> for DerefArgVisitor {
  projection: Box::new([ProjectionElem::Deref]),
  });
  } else {
- self.super_place(place, context, location);
+ self.visit_place_base(&mut place.base, context, location);
+
+ for elem in place.projection.iter() {
+ if let PlaceElem::Index(local) = elem {
+ assert_ne!(*local, self_arg());
+ }
+ }
  }
  }
 }
@@ -137,7 +155,13 @@ impl<'tcx> MutVisitor<'tcx> for PinArgVisitor<'tcx> {
  projection: Box::new([ProjectionElem::Field(Field::new(0), self.ref_gen_ty)]),
  });
  } else {
- self.super_place(place, context, location);
+ self.visit_place_base(&mut place.base, context, location);
+
+ for elem in place.projection.iter() {
+ if let PlaceElem::Index(local) = elem {
+ assert_ne!(*local, self_arg());
+ }
+ }
  }
  }
 }
@@ -247,17 +271,25 @@ impl MutVisitor<'tcx> for TransformVisitor<'tcx> {
  assert_eq!(self.remap.get(local), None);
  }
 
- fn visit_place(&mut self,
- place: &mut Place<'tcx>,
- context: PlaceContext,
- location: Location) {
+ fn visit_place(
+ &mut self,
+ place: &mut Place<'tcx>,
+ context: PlaceContext,
+ location: Location,
+ ) {
  if let PlaceBase::Local(l) = place.base {
  // Replace an Local in the remap with a generator struct access
  if let Some(&(ty, variant_index, idx)) = self.remap.get(&l) {
  replace_base(place, self.make_field(variant_index, idx, ty));
  }
  } else {
- self.super_place(place, context, location);
+ self.visit_place_base(&mut place.base, context, location);
+
+ for elem in place.projection.iter() {
+ if let PlaceElem::Index(local) = elem {
+ assert_ne!(*local, self_arg());
+ }
+ }
  }
  }