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Use FallibleTypeFolder for ConstInferUnifier not TypeRelation #107385

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Jan 28, 2023
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Use FallibleTypeFolder for ConstInferUnifier not TypeRelation #107385

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114 changes: 26 additions & 88 deletions compiler/rustc_infer/src/infer/combine.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -37,7 +37,10 @@ use rustc_middle::traits::ObligationCause;
use rustc_middle::ty::error::{ExpectedFound, TypeError};
use rustc_middle::ty::relate::{self, Relate, RelateResult, TypeRelation};
use rustc_middle::ty::subst::SubstsRef;
use rustc_middle::ty::{self, InferConst, Ty, TyCtxt, TypeVisitable};
use rustc_middle::ty::{
self, FallibleTypeFolder, InferConst, Ty, TyCtxt, TypeFoldable, TypeSuperFoldable,
TypeVisitable,
};
use rustc_middle::ty::{IntType, UintType};
use rustc_span::{Span, DUMMY_SP};

Expand Down Expand Up @@ -140,8 +143,6 @@ impl<'tcx> InferCtxt<'tcx> {
let a = self.shallow_resolve(a);
let b = self.shallow_resolve(b);

let a_is_expected = relation.a_is_expected();

match (a.kind(), b.kind()) {
(
ty::ConstKind::Infer(InferConst::Var(a_vid)),
Expand All @@ -158,11 +159,11 @@ impl<'tcx> InferCtxt<'tcx> {
}

(ty::ConstKind::Infer(InferConst::Var(vid)), _) => {
return self.unify_const_variable(relation.param_env(), vid, b, a_is_expected);
return self.unify_const_variable(vid, b);
}

(_, ty::ConstKind::Infer(InferConst::Var(vid))) => {
return self.unify_const_variable(relation.param_env(), vid, a, !a_is_expected);
return self.unify_const_variable(vid, a);
}
(ty::ConstKind::Unevaluated(..), _) if self.tcx.lazy_normalization() => {
// FIXME(#59490): Need to remove the leak check to accommodate
Expand Down Expand Up @@ -223,10 +224,8 @@ impl<'tcx> InferCtxt<'tcx> {
#[instrument(level = "debug", skip(self))]
fn unify_const_variable(
&self,
param_env: ty::ParamEnv<'tcx>,
target_vid: ty::ConstVid<'tcx>,
ct: ty::Const<'tcx>,
vid_is_expected: bool,
) -> RelateResult<'tcx, ty::Const<'tcx>> {
let (for_universe, span) = {
let mut inner = self.inner.borrow_mut();
Expand All @@ -239,8 +238,12 @@ impl<'tcx> InferCtxt<'tcx> {
ConstVariableValue::Unknown { universe } => (universe, var_value.origin.span),
}
};
let value = ConstInferUnifier { infcx: self, span, param_env, for_universe, target_vid }
.relate(ct, ct)?;
let value = ct.try_fold_with(&mut ConstInferUnifier {
infcx: self,
span,
for_universe,
target_vid,
})?;

self.inner.borrow_mut().const_unification_table().union_value(
target_vid,
Expand Down Expand Up @@ -800,8 +803,6 @@ struct ConstInferUnifier<'cx, 'tcx> {

span: Span,

param_env: ty::ParamEnv<'tcx>,

for_universe: ty::UniverseIndex,

/// The vid of the const variable that is in the process of being
Expand All @@ -810,69 +811,23 @@ struct ConstInferUnifier<'cx, 'tcx> {
target_vid: ty::ConstVid<'tcx>,
}

// We use `TypeRelation` here to propagate `RelateResult` upwards.
//
// Both inputs are expected to be the same.
impl<'tcx> TypeRelation<'tcx> for ConstInferUnifier<'_, 'tcx> {
fn tcx(&self) -> TyCtxt<'tcx> {
self.infcx.tcx
}

fn intercrate(&self) -> bool {
assert!(!self.infcx.intercrate);
false
}

fn param_env(&self) -> ty::ParamEnv<'tcx> {
self.param_env
}

fn tag(&self) -> &'static str {
"ConstInferUnifier"
}

fn a_is_expected(&self) -> bool {
true
}

fn mark_ambiguous(&mut self) {
bug!()
}

fn relate_with_variance<T: Relate<'tcx>>(
&mut self,
_variance: ty::Variance,
_info: ty::VarianceDiagInfo<'tcx>,
a: T,
b: T,
) -> RelateResult<'tcx, T> {
// We don't care about variance here.
self.relate(a, b)
}
impl<'tcx> FallibleTypeFolder<'tcx> for ConstInferUnifier<'_, 'tcx> {
type Error = TypeError<'tcx>;

fn binders<T>(
&mut self,
a: ty::Binder<'tcx, T>,
b: ty::Binder<'tcx, T>,
) -> RelateResult<'tcx, ty::Binder<'tcx, T>>
where
T: Relate<'tcx>,
{
Ok(a.rebind(self.relate(a.skip_binder(), b.skip_binder())?))
fn tcx<'a>(&'a self) -> TyCtxt<'tcx> {
self.infcx.tcx
}

#[instrument(level = "debug", skip(self), ret)]
fn tys(&mut self, t: Ty<'tcx>, _t: Ty<'tcx>) -> RelateResult<'tcx, Ty<'tcx>> {
debug_assert_eq!(t, _t);

fn try_fold_ty(&mut self, t: Ty<'tcx>) -> Result<Ty<'tcx>, TypeError<'tcx>> {
match t.kind() {
&ty::Infer(ty::TyVar(vid)) => {
let vid = self.infcx.inner.borrow_mut().type_variables().root_var(vid);
let probe = self.infcx.inner.borrow_mut().type_variables().probe(vid);
match probe {
TypeVariableValue::Known { value: u } => {
debug!("ConstOccursChecker: known value {:?}", u);
self.tys(u, u)
u.try_fold_with(self)
}
TypeVariableValue::Unknown { universe } => {
if self.for_universe.can_name(universe) {
Expand All @@ -892,16 +847,15 @@ impl<'tcx> TypeRelation<'tcx> for ConstInferUnifier<'_, 'tcx> {
}
}
ty::Infer(ty::IntVar(_) | ty::FloatVar(_)) => Ok(t),
_ => relate::super_relate_tys(self, t, t),
_ => t.try_super_fold_with(self),
}
}

fn regions(
#[instrument(level = "debug", skip(self), ret)]
fn try_fold_region(
&mut self,
r: ty::Region<'tcx>,
_r: ty::Region<'tcx>,
) -> RelateResult<'tcx, ty::Region<'tcx>> {
debug_assert_eq!(r, _r);
) -> Result<ty::Region<'tcx>, TypeError<'tcx>> {
debug!("ConstInferUnifier: r={:?}", r);

match *r {
Expand Down Expand Up @@ -930,14 +884,8 @@ impl<'tcx> TypeRelation<'tcx> for ConstInferUnifier<'_, 'tcx> {
}
}

#[instrument(level = "debug", skip(self))]
fn consts(
&mut self,
c: ty::Const<'tcx>,
_c: ty::Const<'tcx>,
) -> RelateResult<'tcx, ty::Const<'tcx>> {
debug_assert_eq!(c, _c);

#[instrument(level = "debug", skip(self), ret)]
fn try_fold_const(&mut self, c: ty::Const<'tcx>) -> Result<ty::Const<'tcx>, TypeError<'tcx>> {
match c.kind() {
ty::ConstKind::Infer(InferConst::Var(vid)) => {
// Check if the current unification would end up
Expand All @@ -958,7 +906,7 @@ impl<'tcx> TypeRelation<'tcx> for ConstInferUnifier<'_, 'tcx> {
let var_value =
self.infcx.inner.borrow_mut().const_unification_table().probe_value(vid);
match var_value.val {
ConstVariableValue::Known { value: u } => self.consts(u, u),
ConstVariableValue::Known { value: u } => u.try_fold_with(self),
ConstVariableValue::Unknown { universe } => {
if self.for_universe.can_name(universe) {
Ok(c)
Expand All @@ -977,17 +925,7 @@ impl<'tcx> TypeRelation<'tcx> for ConstInferUnifier<'_, 'tcx> {
}
}
}
ty::ConstKind::Unevaluated(ty::UnevaluatedConst { def, substs }) => {
let substs = self.relate_with_variance(
ty::Variance::Invariant,
ty::VarianceDiagInfo::default(),
substs,
substs,
)?;

Ok(self.tcx().mk_const(ty::UnevaluatedConst { def, substs }, c.ty()))
}
_ => relate::super_relate_consts(self, c, c),
_ => c.try_super_fold_with(self),
}
}
}