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Make functions passed to BoundVarReplacer be optional #83090

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merged 1 commit into from
Mar 17, 2021
Merged

Make functions passed to BoundVarReplacer be optional #83090

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108 changes: 53 additions & 55 deletions compiler/rustc_middle/src/ty/fold.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -439,18 +439,18 @@ struct BoundVarReplacer<'a, 'tcx> {
/// the ones we have visited.
current_index: ty::DebruijnIndex,

fld_r: &'a mut (dyn FnMut(ty::BoundRegion) -> ty::Region<'tcx> + 'a),
fld_t: &'a mut (dyn FnMut(ty::BoundTy) -> Ty<'tcx> + 'a),
fld_c: &'a mut (dyn FnMut(ty::BoundVar, Ty<'tcx>) -> &'tcx ty::Const<'tcx> + 'a),
fld_r: Option<&'a mut (dyn FnMut(ty::BoundRegion) -> ty::Region<'tcx> + 'a)>,
fld_t: Option<&'a mut (dyn FnMut(ty::BoundTy) -> Ty<'tcx> + 'a)>,
fld_c: Option<&'a mut (dyn FnMut(ty::BoundVar, Ty<'tcx>) -> &'tcx ty::Const<'tcx> + 'a)>,
}

impl<'a, 'tcx> BoundVarReplacer<'a, 'tcx> {
fn new<F, G, H>(tcx: TyCtxt<'tcx>, fld_r: &'a mut F, fld_t: &'a mut G, fld_c: &'a mut H) -> Self
where
F: FnMut(ty::BoundRegion) -> ty::Region<'tcx>,
G: FnMut(ty::BoundTy) -> Ty<'tcx>,
H: FnMut(ty::BoundVar, Ty<'tcx>) -> &'tcx ty::Const<'tcx>,
{
fn new(
tcx: TyCtxt<'tcx>,
fld_r: Option<&'a mut (dyn FnMut(ty::BoundRegion) -> ty::Region<'tcx> + 'a)>,
fld_t: Option<&'a mut (dyn FnMut(ty::BoundTy) -> Ty<'tcx> + 'a)>,
fld_c: Option<&'a mut (dyn FnMut(ty::BoundVar, Ty<'tcx>) -> &'tcx ty::Const<'tcx> + 'a)>,
) -> Self {
BoundVarReplacer { tcx, current_index: ty::INNERMOST, fld_r, fld_t, fld_c }
}
}
Expand All @@ -469,63 +469,58 @@ impl<'a, 'tcx> TypeFolder<'tcx> for BoundVarReplacer<'a, 'tcx> {

fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
match *t.kind() {
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I wonder whether something like this would be more readable:

fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
    match *t.kind() {
        ty::Bound(debruijn, bound_ty) if debruijn == self.current_index => {
            if let Some(fld_t) = self.fld_t.as_mut() {
                let ty = fld_t(bound_ty);
                return ty::fold::shift_vars(self.tcx, &ty, self.current_index.as_u32());
            }
        }
        _ if t.has_vars_bound_at_or_above(self.current_index) => return t.super_fold_with(self),
    }
    t
}

(and similarly for the other methods).

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Ooh, I like that

ty::Bound(debruijn, bound_ty) => {
if debruijn == self.current_index {
let fld_t = &mut self.fld_t;
ty::Bound(debruijn, bound_ty) if debruijn == self.current_index => {
if let Some(fld_t) = self.fld_t.as_mut() {
let ty = fld_t(bound_ty);
ty::fold::shift_vars(self.tcx, &ty, self.current_index.as_u32())
} else {
t
return ty::fold::shift_vars(self.tcx, &ty, self.current_index.as_u32());
}
}
_ => {
if !t.has_vars_bound_at_or_above(self.current_index) {
// Nothing more to substitute.
t
} else {
t.super_fold_with(self)
}
_ if t.has_vars_bound_at_or_above(self.current_index) => {
return t.super_fold_with(self);
}
_ => {}
}
t
}

fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
match *r {
ty::ReLateBound(debruijn, br) if debruijn == self.current_index => {
let fld_r = &mut self.fld_r;
let region = fld_r(br);
if let ty::ReLateBound(debruijn1, br) = *region {
// If the callback returns a late-bound region,
// that region should always use the INNERMOST
// debruijn index. Then we adjust it to the
// correct depth.
assert_eq!(debruijn1, ty::INNERMOST);
self.tcx.mk_region(ty::ReLateBound(debruijn, br))
} else {
region
if let Some(fld_r) = self.fld_r.as_mut() {
let region = fld_r(br);
return if let ty::ReLateBound(debruijn1, br) = *region {
// If the callback returns a late-bound region,
// that region should always use the INNERMOST
// debruijn index. Then we adjust it to the
// correct depth.
assert_eq!(debruijn1, ty::INNERMOST);
self.tcx.mk_region(ty::ReLateBound(debruijn, br))
} else {
region
};
}
}
_ => r,
_ => {}
}
r
}

fn fold_const(&mut self, ct: &'tcx ty::Const<'tcx>) -> &'tcx ty::Const<'tcx> {
if let ty::Const { val: ty::ConstKind::Bound(debruijn, bound_const), ty } = *ct {
if debruijn == self.current_index {
let fld_c = &mut self.fld_c;
let ct = fld_c(bound_const, ty);
ty::fold::shift_vars(self.tcx, &ct, self.current_index.as_u32())
} else {
ct
match *ct {
ty::Const { val: ty::ConstKind::Bound(debruijn, bound_const), ty }
if debruijn == self.current_index =>
{
if let Some(fld_c) = self.fld_c.as_mut() {
let ct = fld_c(bound_const, ty);
return ty::fold::shift_vars(self.tcx, &ct, self.current_index.as_u32());
}
}
} else {
if !ct.has_vars_bound_at_or_above(self.current_index) {
// Nothing more to substitute.
ct
} else {
ct.super_fold_with(self)
_ if ct.has_vars_bound_at_or_above(self.current_index) => {
return ct.super_fold_with(self);
}
_ => {}
}
ct
}
}

Expand All @@ -550,14 +545,16 @@ impl<'tcx> TyCtxt<'tcx> {
F: FnMut(ty::BoundRegion) -> ty::Region<'tcx>,
T: TypeFoldable<'tcx>,
{
// identity for bound types and consts
let fld_t = |bound_ty| self.mk_ty(ty::Bound(ty::INNERMOST, bound_ty));
let fld_c = |bound_ct, ty| {
self.mk_const(ty::Const { val: ty::ConstKind::Bound(ty::INNERMOST, bound_ct), ty })
};
let mut region_map = BTreeMap::new();
let real_fld_r = |br: ty::BoundRegion| *region_map.entry(br).or_insert_with(|| fld_r(br));
let value = self.replace_escaping_bound_vars(value.skip_binder(), real_fld_r, fld_t, fld_c);
let mut real_fld_r =
|br: ty::BoundRegion| *region_map.entry(br).or_insert_with(|| fld_r(br));
let value = value.skip_binder();
let value = if !value.has_escaping_bound_vars() {
value
} else {
let mut replacer = BoundVarReplacer::new(self, Some(&mut real_fld_r), None, None);
value.fold_with(&mut replacer)
};
(value, region_map)
}

Expand All @@ -580,7 +577,8 @@ impl<'tcx> TyCtxt<'tcx> {
if !value.has_escaping_bound_vars() {
value
} else {
let mut replacer = BoundVarReplacer::new(self, &mut fld_r, &mut fld_t, &mut fld_c);
let mut replacer =
BoundVarReplacer::new(self, Some(&mut fld_r), Some(&mut fld_t), Some(&mut fld_c));
value.fold_with(&mut replacer)
}
}
Expand Down