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use rustc_hir::def_id::DefId;
use rustc_infer::infer::at::ToTrace;
use rustc_infer::infer::canonical::CanonicalVarValues;
use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
use rustc_infer::infer::{InferCtxt, InferOk, LateBoundRegionConversionTime};
use rustc_infer::traits::query::NoSolution;
use rustc_infer::traits::ObligationCause;
use rustc_middle::infer::unify_key::{ConstVariableOrigin, ConstVariableOriginKind};
use rustc_middle::ty::{
self, Ty, TyCtxt, TypeFoldable, TypeSuperVisitable, TypeVisitable, TypeVisitableExt,
TypeVisitor,
};
use rustc_span::DUMMY_SP;
use std::ops::ControlFlow;
use super::search_graph::SearchGraph;
use super::Goal;
pub struct EvalCtxt<'a, 'tcx> {
// FIXME: should be private.
pub(super) infcx: &'a InferCtxt<'tcx>,
pub(super) var_values: CanonicalVarValues<'tcx>,
/// The highest universe index nameable by the caller.
///
/// When we enter a new binder inside of the query we create new universes
/// which the caller cannot name. We have to be careful with variables from
/// these new universes when creating the query response.
///
/// Both because these new universes can prevent us from reaching a fixpoint
/// if we have a coinductive cycle and because that's the only way we can return
/// new placeholders to the caller.
pub(super) max_input_universe: ty::UniverseIndex,
pub(super) search_graph: &'a mut SearchGraph<'tcx>,
/// This field is used by a debug assertion in [`EvalCtxt::evaluate_goal`],
/// see the comment in that method for more details.
pub in_projection_eq_hack: bool,
}
impl<'tcx> EvalCtxt<'_, 'tcx> {
pub(super) fn probe<T>(&mut self, f: impl FnOnce(&mut EvalCtxt<'_, 'tcx>) -> T) -> T {
self.infcx.probe(|_| f(self))
}
pub(super) fn tcx(&self) -> TyCtxt<'tcx> {
self.infcx.tcx
}
pub(super) fn next_ty_infer(&self) -> Ty<'tcx> {
self.infcx.next_ty_var(TypeVariableOrigin {
kind: TypeVariableOriginKind::MiscVariable,
span: DUMMY_SP,
})
}
pub(super) fn next_const_infer(&self, ty: Ty<'tcx>) -> ty::Const<'tcx> {
self.infcx.next_const_var(
ty,
ConstVariableOrigin { kind: ConstVariableOriginKind::MiscVariable, span: DUMMY_SP },
)
}
/// Is the projection predicate is of the form `exists<T> <Ty as Trait>::Assoc = T`.
///
/// This is the case if the `term` is an inference variable in the innermost universe
/// and does not occur in any other part of the predicate.
pub(super) fn term_is_fully_unconstrained(
&self,
goal: Goal<'tcx, ty::ProjectionPredicate<'tcx>>,
) -> bool {
let term_is_infer = match goal.predicate.term.unpack() {
ty::TermKind::Ty(ty) => {
if let &ty::Infer(ty::TyVar(vid)) = ty.kind() {
match self.infcx.probe_ty_var(vid) {
Ok(value) => bug!("resolved var in query: {goal:?} {value:?}"),
Err(universe) => universe == self.universe(),
}
} else {
false
}
}
ty::TermKind::Const(ct) => {
if let ty::ConstKind::Infer(ty::InferConst::Var(vid)) = ct.kind() {
match self.infcx.probe_const_var(vid) {
Ok(value) => bug!("resolved var in query: {goal:?} {value:?}"),
Err(universe) => universe == self.universe(),
}
} else {
false
}
}
};
// Guard against `<T as Trait<?0>>::Assoc = ?0>`.
struct ContainsTerm<'tcx> {
term: ty::Term<'tcx>,
}
impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for ContainsTerm<'tcx> {
type BreakTy = ();
fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
if t.needs_infer() {
if ty::Term::from(t) == self.term {
ControlFlow::Break(())
} else {
t.super_visit_with(self)
}
} else {
ControlFlow::Continue(())
}
}
fn visit_const(&mut self, c: ty::Const<'tcx>) -> ControlFlow<Self::BreakTy> {
if c.needs_infer() {
if ty::Term::from(c) == self.term {
ControlFlow::Break(())
} else {
c.super_visit_with(self)
}
} else {
ControlFlow::Continue(())
}
}
}
let mut visitor = ContainsTerm { term: goal.predicate.term };
term_is_infer
&& goal.predicate.projection_ty.visit_with(&mut visitor).is_continue()
&& goal.param_env.visit_with(&mut visitor).is_continue()
}
#[instrument(level = "debug", skip(self, param_env), ret)]
pub(super) fn eq<T: ToTrace<'tcx>>(
&self,
param_env: ty::ParamEnv<'tcx>,
lhs: T,
rhs: T,
) -> Result<Vec<Goal<'tcx, ty::Predicate<'tcx>>>, NoSolution> {
self.infcx
.at(&ObligationCause::dummy(), param_env)
.eq(lhs, rhs)
.map(|InferOk { value: (), obligations }| {
obligations.into_iter().map(|o| o.into()).collect()
})
.map_err(|e| {
debug!(?e, "failed to equate");
NoSolution
})
}
pub(super) fn instantiate_binder_with_infer<T: TypeFoldable<TyCtxt<'tcx>> + Copy>(
&self,
value: ty::Binder<'tcx, T>,
) -> T {
self.infcx.instantiate_binder_with_fresh_vars(
DUMMY_SP,
LateBoundRegionConversionTime::HigherRankedType,
value,
)
}
pub(super) fn instantiate_binder_with_placeholders<T: TypeFoldable<TyCtxt<'tcx>> + Copy>(
&self,
value: ty::Binder<'tcx, T>,
) -> T {
self.infcx.instantiate_binder_with_placeholders(value)
}
pub(super) fn resolve_vars_if_possible<T>(&self, value: T) -> T
where
T: TypeFoldable<TyCtxt<'tcx>>,
{
self.infcx.resolve_vars_if_possible(value)
}
pub(super) fn fresh_substs_for_item(&self, def_id: DefId) -> ty::SubstsRef<'tcx> {
self.infcx.fresh_substs_for_item(DUMMY_SP, def_id)
}
pub(super) fn universe(&self) -> ty::UniverseIndex {
self.infcx.universe()
}
}
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