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resolve_instance: remove BoundVarsCollector

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This commit is contained in:
lcnr 2022-09-08 17:02:09 +02:00
parent 4a09adf99f
commit 14f2acd0ac
1 changed files with 3 additions and 108 deletions
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111
compiler/rustc_ty_utils/src/instance.rs
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@ -4,112 +4,12 @@
use rustc_middle::traits::CodegenObligationError;
use rustc_middle::ty::subst::SubstsRef;
use rustc_middle::ty::{
self, Binder, Instance, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitor,
self, Instance, TyCtxt, TypeVisitable,
};
use rustc_span::{sym, DUMMY_SP};
use rustc_trait_selection::traits;
use traits::{translate_substs, Reveal};
use rustc_data_structures::sso::SsoHashSet;
use std::collections::btree_map::Entry;
use std::collections::BTreeMap;
use std::ops::ControlFlow;
// FIXME(#86795): `BoundVarsCollector` here should **NOT** be used
// outside of `resolve_associated_item`. It's just to address #64494,
// #83765, and #85848 which are creating bound types/regions that lose
// their `Binder` *unintentionally*.
// It's ideal to remove `BoundVarsCollector` and just use
// `ty::Binder::*` methods but we use this stopgap until we figure out
// the "real" fix.
struct BoundVarsCollector<'tcx> {
binder_index: ty::DebruijnIndex,
vars: BTreeMap<u32, ty::BoundVariableKind>,
// We may encounter the same variable at different levels of binding, so
// this can't just be `Ty`
visited: SsoHashSet<(ty::DebruijnIndex, Ty<'tcx>)>,
}
impl<'tcx> BoundVarsCollector<'tcx> {
fn new() -> Self {
BoundVarsCollector {
binder_index: ty::INNERMOST,
vars: BTreeMap::new(),
visited: SsoHashSet::default(),
}
}
fn into_vars(self, tcx: TyCtxt<'tcx>) -> &'tcx ty::List<ty::BoundVariableKind> {
let max = self.vars.iter().map(|(k, _)| *k).max().unwrap_or(0);
for i in 0..max {
if let None = self.vars.get(&i) {
panic!("Unknown variable: {:?}", i);
}
}
tcx.mk_bound_variable_kinds(self.vars.into_iter().map(|(_, v)| v))
}
}
impl<'tcx> TypeVisitor<'tcx> for BoundVarsCollector<'tcx> {
type BreakTy = ();
fn visit_binder<T: TypeVisitable<'tcx>>(
&mut self,
t: &Binder<'tcx, T>,
) -> ControlFlow<Self::BreakTy> {
self.binder_index.shift_in(1);
let result = t.super_visit_with(self);
self.binder_index.shift_out(1);
result
}
fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
if t.outer_exclusive_binder() < self.binder_index
|| !self.visited.insert((self.binder_index, t))
{
return ControlFlow::CONTINUE;
}
match *t.kind() {
ty::Bound(debruijn, bound_ty) if debruijn == self.binder_index => {
match self.vars.entry(bound_ty.var.as_u32()) {
Entry::Vacant(entry) => {
entry.insert(ty::BoundVariableKind::Ty(bound_ty.kind));
}
Entry::Occupied(entry) => match entry.get() {
ty::BoundVariableKind::Ty(_) => {}
_ => bug!("Conflicting bound vars"),
},
}
}
_ => (),
};
t.super_visit_with(self)
}
fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow<Self::BreakTy> {
match *r {
ty::ReLateBound(index, br) if index == self.binder_index => {
match self.vars.entry(br.var.as_u32()) {
Entry::Vacant(entry) => {
entry.insert(ty::BoundVariableKind::Region(br.kind));
}
Entry::Occupied(entry) => match entry.get() {
ty::BoundVariableKind::Region(_) => {}
_ => bug!("Conflicting bound vars"),
},
}
}
_ => (),
};
r.super_visit_with(self)
}
}
fn resolve_instance<'tcx>(
tcx: TyCtxt<'tcx>,
key: ty::ParamEnvAnd<'tcx, (DefId, SubstsRef<'tcx>)>,
@ -201,19 +101,14 @@ fn resolve_associated_item<'tcx>(
let trait_ref = ty::TraitRef::from_method(tcx, trait_id, rcvr_substs);
// See FIXME on `BoundVarsCollector`.
let mut bound_vars_collector = BoundVarsCollector::new();
trait_ref.visit_with(&mut bound_vars_collector);
let trait_binder = ty::Binder::bind_with_vars(trait_ref, bound_vars_collector.into_vars(tcx));
let vtbl = match tcx.codegen_fulfill_obligation((param_env, trait_binder)) {
let vtbl = match tcx.codegen_fulfill_obligation((param_env, ty::Binder::dummy(trait_ref))) {
Ok(vtbl) => vtbl,
Err(CodegenObligationError::Ambiguity) => {
let reported = tcx.sess.delay_span_bug(
tcx.def_span(trait_item_id),
&format!(
"encountered ambiguity selecting `{:?}` during codegen, presuming due to \
"encountered ambiguity selecting `{trait_ref:?}` during codegen, presuming due to \
overflow or prior type error",
trait_binder
),
);
return Err(reported);