src/librustc_mir/borrow_check/nll/renumber.rs

   1 use rustc::ty::subst::SubstsRef;
   2 use rustc::ty::{self, Ty, TyCtxt, TypeFoldable};
   3 use rustc::mir::{Body, Location, PlaceElem, Promoted};
   4 use rustc::mir::visit::{MutVisitor, TyContext};
   5 use rustc::infer::{InferCtxt, NLLRegionVariableOrigin};
   6 use rustc_index::vec::IndexVec;
   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
  36         .tcx
  37         .fold_regions(value, &mut false, |_region, _depth| {
  38             let origin = NLLRegionVariableOrigin::Existential { from_forall: false };
  39             infcx.next_nll_region_var(origin)
  40         })
  41 }
  42
  43 struct NLLVisitor<'a, 'tcx> {
  44     infcx: &'a InferCtxt<'a, 'tcx>,
  45 }
  46
  47 impl<'a, 'tcx> NLLVisitor<'a, 'tcx> {
  48     fn renumber_regions<T>(&mut self, value: &T) -> T
  49     where
  50         T: TypeFoldable<'tcx>,
  51     {
  52         renumber_regions(self.infcx, value)
  53     }
  54 }
  55
  56 impl<'a, 'tcx> MutVisitor<'tcx> for NLLVisitor<'a, 'tcx> {
  57     fn tcx(&self) -> TyCtxt<'tcx> {
  58         self.infcx.tcx
  59     }
  60
  61     fn visit_ty(&mut self, ty: &mut Ty<'tcx>, ty_context: TyContext) {
  62         debug!("visit_ty(ty={:?}, ty_context={:?})", ty, ty_context);
  63
  64         *ty = self.renumber_regions(ty);
  65
  66         debug!("visit_ty: ty={:?}", ty);
  67     }
  68
  69     fn process_projection_elem(
  70         &mut self,
  71         elem: &PlaceElem<'tcx>,
  72     ) -> Option<PlaceElem<'tcx>> {
  73         if let PlaceElem::Field(field, ty) = elem {
  74             let new_ty = self.renumber_regions(ty);
  75
  76             if new_ty != *ty {
  77                 return Some(PlaceElem::Field(*field, new_ty));
  78             }
  79         }
  80
  81         None
  82     }
  83
  84     fn visit_substs(&mut self, substs: &mut SubstsRef<'tcx>, location: Location) {
  85         debug!("visit_substs(substs={:?}, location={:?})", substs, location);
  86
  87         *substs = self.renumber_regions(&{ *substs });
  88
  89         debug!("visit_substs: substs={:?}", substs);
  90     }
  91
  92     fn visit_region(&mut self, region: &mut ty::Region<'tcx>, location: Location) {
  93         debug!("visit_region(region={:?}, location={:?})", region, location);
  94
  95         let old_region = *region;
  96         *region = self.renumber_regions(&old_region);
  97
  98         debug!("visit_region: region={:?}", region);
  99     }
 100
 101     fn visit_const(&mut self, constant: &mut &'tcx ty::Const<'tcx>, _location: Location) {
 102         *constant = self.renumber_regions(&*constant);
 103     }
 104 }