src/librustc_mir/borrow_check/nll/renumber.rs

   1 use rustc::ty::subst::Substs;
   2 use rustc::ty::{self, ClosureSubsts, GeneratorSubsts, Ty, TypeFoldable};
   3 use rustc::mir::{Location, Mir};
   4 use rustc::mir::visit::{MutVisitor, TyContext};
   5 use rustc::infer::{InferCtxt, NLLRegionVariableOrigin};
   6
   7 /// Replaces all free regions appearing in the MIR with fresh
   8 /// inference variables, returning the number of variables created.
   9 pub fn renumber_mir<'tcx>(infcx: &InferCtxt<'_, '_, 'tcx>, mir: &mut Mir<'tcx>) {
  10     debug!("renumber_mir()");
  11     debug!("renumber_mir: mir.arg_count={:?}", mir.arg_count);
  12
  13     let mut visitor = NLLVisitor { infcx };
  14     visitor.visit_mir(mir);
  15 }
  16
  17 /// Replaces all regions appearing in `value` with fresh inference
  18 /// variables.
  19 pub fn renumber_regions<'tcx, T>(
  20     infcx: &InferCtxt<'_, '_, 'tcx>,
  21     value: &T,
  22 ) -> T
  23 where
  24     T: TypeFoldable<'tcx>,
  25 {
  26     debug!("renumber_regions(value={:?})", value);
  27
  28     infcx
  29         .tcx
  30         .fold_regions(value, &mut false, |_region, _depth| {
  31             let origin = NLLRegionVariableOrigin::Existential;
  32             infcx.next_nll_region_var(origin)
  33         })
  34 }
  35
  36 struct NLLVisitor<'a, 'gcx: 'a + 'tcx, 'tcx: 'a> {
  37     infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
  38 }
  39
  40 impl<'a, 'gcx, 'tcx> NLLVisitor<'a, 'gcx, 'tcx> {
  41     fn renumber_regions<T>(&mut self, value: &T) -> T
  42     where
  43         T: TypeFoldable<'tcx>,
  44     {
  45         renumber_regions(self.infcx, value)
  46     }
  47 }
  48
  49 impl<'a, 'gcx, 'tcx> MutVisitor<'tcx> for NLLVisitor<'a, 'gcx, 'tcx> {
  50     fn visit_mir(&mut self, mir: &mut Mir<'tcx>) {
  51         for promoted in mir.promoted.iter_mut() {
  52             self.visit_mir(promoted);
  53         }
  54
  55         self.super_mir(mir);
  56     }
  57
  58     fn visit_ty(&mut self, ty: &mut Ty<'tcx>, ty_context: TyContext) {
  59         debug!("visit_ty(ty={:?}, ty_context={:?})", ty, ty_context);
  60
  61         *ty = self.renumber_regions(ty);
  62
  63         debug!("visit_ty: ty={:?}", ty);
  64     }
  65
  66     fn visit_substs(&mut self, substs: &mut &'tcx Substs<'tcx>, location: Location) {
  67         debug!("visit_substs(substs={:?}, location={:?})", substs, location);
  68
  69         *substs = self.renumber_regions(&{ *substs });
  70
  71         debug!("visit_substs: substs={:?}", substs);
  72     }
  73
  74     fn visit_region(&mut self, region: &mut ty::Region<'tcx>, location: Location) {
  75         debug!("visit_region(region={:?}, location={:?})", region, location);
  76
  77         let old_region = *region;
  78         *region = self.renumber_regions(&old_region);
  79
  80         debug!("visit_region: region={:?}", region);
  81     }
  82
  83     fn visit_const(&mut self, constant: &mut &'tcx ty::LazyConst<'tcx>, _location: Location) {
  84         *constant = self.renumber_regions(&*constant);
  85     }
  86
  87     fn visit_generator_substs(&mut self,
  88                               substs: &mut GeneratorSubsts<'tcx>,
  89                               location: Location) {
  90         debug!(
  91             "visit_generator_substs(substs={:?}, location={:?})",
  92             substs,
  93             location,
  94         );
  95
  96         *substs = self.renumber_regions(substs);
  97
  98         debug!("visit_generator_substs: substs={:?}", substs);
  99     }
 100
 101     fn visit_closure_substs(&mut self, substs: &mut ClosureSubsts<'tcx>, location: Location) {
 102         debug!(
 103             "visit_closure_substs(substs={:?}, location={:?})",
 104             substs,
 105             location
 106         );
 107
 108         *substs = self.renumber_regions(substs);
 109
 110         debug!("visit_closure_substs: substs={:?}", substs);
 111     }
 112 }