src/librustc_mir/borrow_check/renumber.rs

   1 use rustc_index::vec::IndexVec;
   2 use rustc_infer::infer::{InferCtxt, NLLRegionVariableOrigin};
   3 use rustc_middle::mir::visit::{MutVisitor, TyContext};
   4 use rustc_middle::mir::{Body, Location, PlaceElem, Promoted};
   5 use rustc_middle::ty::subst::SubstsRef;
   6 use rustc_middle::ty::{self, Ty, TyCtxt, TypeFoldable};
   7
   8 /// Replaces all free regions appearing in the MIR with fresh
   9 /// inference variables, returning the number of variables created.
  10 pub fn renumber_mir<'tcx>(
  11     infcx: &InferCtxt<'_, 'tcx>,
  12     body: &mut Body<'tcx>,
  13     promoted: &mut IndexVec<Promoted, Body<'tcx>>,
  14 ) {
  15     debug!("renumber_mir()");
  16     debug!("renumber_mir: body.arg_count={:?}", body.arg_count);
  17
  18     let mut visitor = NLLVisitor { infcx };
  19
  20     for body in promoted.iter_mut() {
  21         visitor.visit_body(body);
  22     }
  23
  24     visitor.visit_body(body);
  25 }
  26
  27 /// Replaces all regions appearing in `value` with fresh inference
  28 /// variables.
  29 pub fn renumber_regions<'tcx, T>(infcx: &InferCtxt<'_, 'tcx>, value: &T) -> T
  30 where
  31     T: TypeFoldable<'tcx>,
  32 {
  33     debug!("renumber_regions(value={:?})", value);
  34
  35     infcx.tcx.fold_regions(value, &mut false, |_region, _depth| {
  36         let origin = NLLRegionVariableOrigin::Existential { from_forall: false };
  37         infcx.next_nll_region_var(origin)
  38     })
  39 }
  40
  41 struct NLLVisitor<'a, 'tcx> {
  42     infcx: &'a InferCtxt<'a, 'tcx>,
  43 }
  44
  45 impl<'a, 'tcx> NLLVisitor<'a, 'tcx> {
  46     fn renumber_regions<T>(&mut self, value: &T) -> T
  47     where
  48         T: TypeFoldable<'tcx>,
  49     {
  50         renumber_regions(self.infcx, value)
  51     }
  52 }
  53
  54 impl<'a, 'tcx> MutVisitor<'tcx> for NLLVisitor<'a, 'tcx> {
  55     fn tcx(&self) -> TyCtxt<'tcx> {
  56         self.infcx.tcx
  57     }
  58
  59     fn visit_ty(&mut self, ty: &mut Ty<'tcx>, ty_context: TyContext) {
  60         debug!("visit_ty(ty={:?}, ty_context={:?})", ty, ty_context);
  61
  62         *ty = self.renumber_regions(ty);
  63
  64         debug!("visit_ty: ty={:?}", ty);
  65     }
  66
  67     fn process_projection_elem(
  68         &mut self,
  69         elem: PlaceElem<'tcx>,
  70         _: Location,
  71     ) -> Option<PlaceElem<'tcx>> {
  72         if let PlaceElem::Field(field, ty) = elem {
  73             let new_ty = self.renumber_regions(&ty);
  74
  75             if new_ty != ty {
  76                 return Some(PlaceElem::Field(field, new_ty));
  77             }
  78         }
  79
  80         None
  81     }
  82
  83     fn visit_substs(&mut self, substs: &mut SubstsRef<'tcx>, location: Location) {
  84         debug!("visit_substs(substs={:?}, location={:?})", substs, location);
  85
  86         *substs = self.renumber_regions(&{ *substs });
  87
  88         debug!("visit_substs: substs={:?}", substs);
  89     }
  90
  91     fn visit_region(&mut self, region: &mut ty::Region<'tcx>, location: Location) {
  92         debug!("visit_region(region={:?}, location={:?})", region, location);
  93
  94         let old_region = *region;
  95         *region = self.renumber_regions(&old_region);
  96
  97         debug!("visit_region: region={:?}", region);
  98     }
  99
 100     fn visit_const(&mut self, constant: &mut &'tcx ty::Const<'tcx>, _location: Location) {
 101         *constant = self.renumber_regions(&*constant);
 102     }
 103 }