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use rustc_index::vec::IndexVec;
use rustc_infer::infer::{InferCtxt, NllRegionVariableOrigin};
use rustc_middle::mir::visit::{MutVisitor, TyContext};
use rustc_middle::mir::{Body, Location, Promoted};
use rustc_middle::mir::{Constant, ConstantKind};
use rustc_middle::ty::subst::SubstsRef;
use rustc_middle::ty::{self, Ty, TyCtxt, TypeFoldable};
/// Replaces all free regions appearing in the MIR with fresh
/// inference variables, returning the number of variables created.
#[instrument(skip(infcx, body, promoted), level = "debug")]
pub fn renumber_mir<'tcx>(
infcx: &InferCtxt<'_, 'tcx>,
body: &mut Body<'tcx>,
promoted: &mut IndexVec<Promoted, Body<'tcx>>,
) {
debug!(?body.arg_count);
let mut visitor = NllVisitor { infcx };
for body in promoted.iter_mut() {
visitor.visit_body(body);
}
visitor.visit_body(body);
}
/// Replaces all regions appearing in `value` with fresh inference
/// variables.
#[instrument(skip(infcx), level = "debug")]
pub fn renumber_regions<'tcx, T>(infcx: &InferCtxt<'_, 'tcx>, value: T) -> T
where
T: TypeFoldable<'tcx>,
{
infcx.tcx.fold_regions(value, |_region, _depth| {
let origin = NllRegionVariableOrigin::Existential { from_forall: false };
infcx.next_nll_region_var(origin)
})
}
// FIXME(valtrees): This function is necessary because `fold_regions`
// panics for mir constants in the visitor.
//
// Once `visit_mir_constant` is removed we can also remove this function
// and just use `renumber_regions`.
fn renumber_regions_in_mir_constant<'tcx>(
infcx: &InferCtxt<'_, 'tcx>,
value: ConstantKind<'tcx>,
) -> ConstantKind<'tcx> {
infcx.tcx.super_fold_regions(value, |_region, _depth| {
let origin = NllRegionVariableOrigin::Existential { from_forall: false };
infcx.next_nll_region_var(origin)
})
}
struct NllVisitor<'a, 'tcx> {
infcx: &'a InferCtxt<'a, 'tcx>,
}
impl<'a, 'tcx> NllVisitor<'a, 'tcx> {
fn renumber_regions<T>(&mut self, value: T) -> T
where
T: TypeFoldable<'tcx>,
{
renumber_regions(self.infcx, value)
}
fn renumber_regions_in_mir_constant(
&mut self,
value: ConstantKind<'tcx>,
) -> ConstantKind<'tcx> {
renumber_regions_in_mir_constant(self.infcx, value)
}
}
impl<'a, 'tcx> MutVisitor<'tcx> for NllVisitor<'a, 'tcx> {
fn tcx(&self) -> TyCtxt<'tcx> {
self.infcx.tcx
}
#[instrument(skip(self), level = "debug")]
fn visit_ty(&mut self, ty: &mut Ty<'tcx>, ty_context: TyContext) {
*ty = self.renumber_regions(*ty);
debug!(?ty);
}
#[instrument(skip(self), level = "debug")]
fn visit_substs(&mut self, substs: &mut SubstsRef<'tcx>, location: Location) {
*substs = self.renumber_regions(*substs);
debug!(?substs);
}
#[instrument(skip(self), level = "debug")]
fn visit_region(&mut self, region: &mut ty::Region<'tcx>, location: Location) {
let old_region = *region;
*region = self.renumber_regions(old_region);
debug!(?region);
}
#[instrument(skip(self), level = "debug")]
fn visit_constant(&mut self, constant: &mut Constant<'tcx>, _location: Location) {
let literal = constant.literal;
constant.literal = self.renumber_regions_in_mir_constant(literal);
debug!("constant: {:#?}", constant);
}
}
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