bjoernager/rust
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implement and use NormalizesTo

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This commit is contained in:
lcnr 2023-12-07 18:20:27 +01:00
parent 3978f545ba
commit ffb4c08a81
21 changed files with 135 additions and 125 deletions
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66
compiler/rustc_infer/src/infer/combine.rs
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@ -34,8 +34,8 @@ use rustc_middle::infer::unify_key::{ConstVarValue, ConstVariableValue, EffectVa
use rustc_middle::infer::unify_key::{ConstVariableOrigin, ConstVariableOriginKind};
use rustc_middle::ty::error::{ExpectedFound, TypeError};
use rustc_middle::ty::relate::{RelateResult, TypeRelation};
use rustc_middle::ty::TyVar;
use rustc_middle::ty::{self, InferConst, ToPredicate, Ty, TyCtxt, TypeVisitableExt};
use rustc_middle::ty::{AliasRelationDirection, TyVar};
use rustc_middle::ty::{IntType, UintType};
use rustc_span::DUMMY_SP;
@ -490,31 +490,47 @@ impl<'infcx, 'tcx> CombineFields<'infcx, 'tcx> {
// cyclic type. We instead delay the unification in case
// the alias can be normalized to something which does not
// mention `?0`.
// FIXME(-Ztrait-solver=next): replace this with `AliasRelate`
let &ty::Alias(kind, data) = a_ty.kind() else {
bug!("generalization should only result in infer vars for aliases");
};
if !self.infcx.next_trait_solver() {
// The old solver only accepts projection predicates for associated types.
match kind {
ty::AliasKind::Projection => {}
ty::AliasKind::Inherent | ty::AliasKind::Weak | ty::AliasKind::Opaque => {
return Err(TypeError::CyclicTy(a_ty));
if self.infcx.next_trait_solver() {
let (lhs, rhs, direction) = match ambient_variance {
ty::Variance::Invariant => {
(a_ty.into(), b_ty.into(), AliasRelationDirection::Equate)
}
ty::Variance::Covariant => {
(a_ty.into(), b_ty.into(), AliasRelationDirection::Subtype)
}
ty::Variance::Contravariant => {
(b_ty.into(), a_ty.into(), AliasRelationDirection::Subtype)
}
ty::Variance::Bivariant => unreachable!("bivariant generalization"),
};
self.obligations.push(Obligation::new(
self.tcx(),
self.trace.cause.clone(),
self.param_env,
ty::PredicateKind::AliasRelate(lhs, rhs, direction),
));
} else {
match a_ty.kind() {
&ty::Alias(ty::AliasKind::Projection, data) => {
// FIXME: This does not handle subtyping correctly, we should switch to
// alias-relate in the new solver and could instead create a new inference
// variable for `a_ty`, emitting `Projection(a_ty, a_infer)` and
// `a_infer <: b_ty`.
self.obligations.push(Obligation::new(
self.tcx(),
self.trace.cause.clone(),
self.param_env,
ty::ProjectionPredicate { projection_ty: data, term: b_ty.into() },
))
}
// The old solver only accepts projection predicates for associated types.
ty::Alias(
ty::AliasKind::Inherent | ty::AliasKind::Weak | ty::AliasKind::Opaque,
_,
) => return Err(TypeError::CyclicTy(a_ty)),
_ => bug!("generalizated `{a_ty:?} to infer, not an alias"),
}
}
// FIXME: This does not handle subtyping correctly, we should switch to
// alias-relate in the new solver and could instead create a new inference
// variable for `a_ty`, emitting `Projection(a_ty, a_infer)` and
// `a_infer <: b_ty`.
self.obligations.push(Obligation::new(
self.tcx(),
self.trace.cause.clone(),
self.param_env,
ty::ProjectionPredicate { projection_ty: data, term: b_ty.into() },
))
} else {
match ambient_variance {
ty::Variance::Invariant => self.equate(a_is_expected).relate(a_ty, b_ty),
@ -525,9 +541,7 @@ impl<'infcx, 'tcx> CombineFields<'infcx, 'tcx> {
a_ty,
b_ty,
),
ty::Variance::Bivariant => {
unreachable!("no code should be generalizing bivariantly (currently)")
}
ty::Variance::Bivariant => unreachable!("bivariant generalization"),
}?;
}