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Rollup merge of rust-lang#69591 - matthewjasper:query-response-relate…
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…, r=nikomatsakis

Use TypeRelating for instantiating query responses

`eq` can add constraints to `RegionConstraintData`, which isn't allowed during borrow checking outside of a `CustomTypeOp`. Use `TypeRelating` instead to always push constraints to the obligations list.

closes rust-lang#69490
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Centril authored Mar 11, 2020
2 parents 7ef49a3 + cbf5f7d commit bf1f7c9
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Showing 2 changed files with 111 additions and 7 deletions.
85 changes: 78 additions & 7 deletions src/librustc_infer/infer/canonical/query_response.rs
Original file line number Diff line number Diff line change
Expand Up @@ -12,14 +12,15 @@ use crate::infer::canonical::{
Canonical, CanonicalVarValues, CanonicalizedQueryResponse, Certainty, OriginalQueryValues,
QueryOutlivesConstraint, QueryRegionConstraints, QueryResponse,
};
use crate::infer::nll_relate::{NormalizationStrategy, TypeRelating, TypeRelatingDelegate};
use crate::infer::region_constraints::{Constraint, RegionConstraintData};
use crate::infer::InferCtxtBuilder;
use crate::infer::{InferCtxt, InferOk, InferResult};
use crate::infer::{InferCtxt, InferCtxtBuilder, InferOk, InferResult, NLLRegionVariableOrigin};
use crate::traits::query::{Fallible, NoSolution};
use crate::traits::TraitEngine;
use crate::traits::{DomainGoal, TraitEngine};
use crate::traits::{Obligation, ObligationCause, PredicateObligation};
use rustc::arena::ArenaAllocatable;
use rustc::ty::fold::TypeFoldable;
use rustc::ty::relate::TypeRelation;
use rustc::ty::subst::{GenericArg, GenericArgKind};
use rustc::ty::{self, BoundVar, Ty, TyCtxt};
use rustc_data_structures::captures::Captures;
Expand Down Expand Up @@ -304,13 +305,31 @@ impl<'cx, 'tcx> InferCtxt<'cx, 'tcx> {
}

(GenericArgKind::Type(v1), GenericArgKind::Type(v2)) => {
let ok = self.at(cause, param_env).eq(v1, v2)?;
obligations.extend(ok.into_obligations());
TypeRelating::new(
self,
QueryTypeRelatingDelegate {
infcx: self,
param_env,
cause,
obligations: &mut obligations,
},
ty::Variance::Invariant,
)
.relate(&v1, &v2)?;
}

(GenericArgKind::Const(v1), GenericArgKind::Const(v2)) => {
let ok = self.at(cause, param_env).eq(v1, v2)?;
obligations.extend(ok.into_obligations());
TypeRelating::new(
self,
QueryTypeRelatingDelegate {
infcx: self,
param_env,
cause,
obligations: &mut obligations,
},
ty::Variance::Invariant,
)
.relate(&v1, &v2)?;
}

_ => {
Expand Down Expand Up @@ -656,3 +675,55 @@ pub fn make_query_region_constraints<'tcx>(

QueryRegionConstraints { outlives, member_constraints: member_constraints.clone() }
}

struct QueryTypeRelatingDelegate<'a, 'tcx> {
infcx: &'a InferCtxt<'a, 'tcx>,
obligations: &'a mut Vec<PredicateObligation<'tcx>>,
param_env: ty::ParamEnv<'tcx>,
cause: &'a ObligationCause<'tcx>,
}

impl<'tcx> TypeRelatingDelegate<'tcx> for QueryTypeRelatingDelegate<'_, 'tcx> {
fn create_next_universe(&mut self) -> ty::UniverseIndex {
self.infcx.create_next_universe()
}

fn next_existential_region_var(&mut self, from_forall: bool) -> ty::Region<'tcx> {
let origin = NLLRegionVariableOrigin::Existential { from_forall };
self.infcx.next_nll_region_var(origin)
}

fn next_placeholder_region(&mut self, placeholder: ty::PlaceholderRegion) -> ty::Region<'tcx> {
self.infcx.tcx.mk_region(ty::RePlaceholder(placeholder))
}

fn generalize_existential(&mut self, universe: ty::UniverseIndex) -> ty::Region<'tcx> {
self.infcx.next_nll_region_var_in_universe(
NLLRegionVariableOrigin::Existential { from_forall: false },
universe,
)
}

fn push_outlives(&mut self, sup: ty::Region<'tcx>, sub: ty::Region<'tcx>) {
self.obligations.push(Obligation {
cause: self.cause.clone(),
param_env: self.param_env,
predicate: ty::Predicate::RegionOutlives(ty::Binder::dummy(ty::OutlivesPredicate(
sup, sub,
))),
recursion_depth: 0,
});
}

fn push_domain_goal(&mut self, _: DomainGoal<'tcx>) {
bug!("should never be invoked with eager normalization")
}

fn normalization() -> NormalizationStrategy {
NormalizationStrategy::Eager
}

fn forbid_inference_vars() -> bool {
true
}
}
33 changes: 33 additions & 0 deletions src/test/ui/nll/user-annotations/type-annotation-with-hrtb.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,33 @@
// Regression test for issue #69490

// check-pass

pub trait Trait<T> {
const S: &'static str;
}

impl<T> Trait<()> for T
where
T: for<'a> Trait<&'a ()>,
{
// Use of `T::S` here caused an ICE
const S: &'static str = T::S;
}

// Some similar cases that didn't ICE:

impl<'a, T> Trait<()> for (T,)
where
T: Trait<&'a ()>,
{
const S: &'static str = T::S;
}

impl<T> Trait<()> for [T; 1]
where
T: Trait<for<'a> fn(&'a ())>,
{
const S: &'static str = T::S;
}

fn main() {}

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