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use std::cell::RefCell;
use std::fmt::Debug;
use super::TraitEngine;
use super::{ChalkFulfillmentContext, FulfillmentContext};
use crate::solve::FulfillmentCtxt as NextFulfillmentCtxt;
use crate::traits::NormalizeExt;
use rustc_data_structures::fx::FxIndexSet;
use rustc_hir::def_id::{DefId, LocalDefId};
use rustc_infer::infer::at::ToTrace;
use rustc_infer::infer::canonical::{
Canonical, CanonicalQueryResponse, CanonicalVarValues, QueryResponse,
};
use rustc_infer::infer::{InferCtxt, InferOk};
use rustc_infer::traits::query::Fallible;
use rustc_infer::traits::{
FulfillmentError, Obligation, ObligationCause, PredicateObligation, TraitEngineExt as _,
};
use rustc_middle::arena::ArenaAllocatable;
use rustc_middle::ty::error::TypeError;
use rustc_middle::ty::ToPredicate;
use rustc_middle::ty::TypeFoldable;
use rustc_middle::ty::{self, Ty, TyCtxt};
use rustc_session::config::TraitSolver;
use rustc_span::Span;
pub trait TraitEngineExt<'tcx> {
fn new(tcx: TyCtxt<'tcx>) -> Box<Self>;
fn new_in_snapshot(tcx: TyCtxt<'tcx>) -> Box<Self>;
}
impl<'tcx> TraitEngineExt<'tcx> for dyn TraitEngine<'tcx> {
fn new(tcx: TyCtxt<'tcx>) -> Box<Self> {
match tcx.sess.opts.unstable_opts.trait_solver {
TraitSolver::Classic => Box::new(FulfillmentContext::new()),
TraitSolver::Chalk => Box::new(ChalkFulfillmentContext::new()),
TraitSolver::Next => Box::new(NextFulfillmentCtxt::new()),
}
}
fn new_in_snapshot(tcx: TyCtxt<'tcx>) -> Box<Self> {
match tcx.sess.opts.unstable_opts.trait_solver {
TraitSolver::Classic => Box::new(FulfillmentContext::new_in_snapshot()),
TraitSolver::Chalk => Box::new(ChalkFulfillmentContext::new_in_snapshot()),
TraitSolver::Next => Box::new(NextFulfillmentCtxt::new()),
}
}
}
/// Used if you want to have pleasant experience when dealing
/// with obligations outside of hir or mir typeck.
pub struct ObligationCtxt<'a, 'tcx> {
pub infcx: &'a InferCtxt<'tcx>,
engine: RefCell<Box<dyn TraitEngine<'tcx>>>,
}
impl<'a, 'tcx> ObligationCtxt<'a, 'tcx> {
pub fn new(infcx: &'a InferCtxt<'tcx>) -> Self {
Self { infcx, engine: RefCell::new(<dyn TraitEngine<'_>>::new(infcx.tcx)) }
}
pub fn new_in_snapshot(infcx: &'a InferCtxt<'tcx>) -> Self {
Self { infcx, engine: RefCell::new(<dyn TraitEngine<'_>>::new_in_snapshot(infcx.tcx)) }
}
pub fn register_obligation(&self, obligation: PredicateObligation<'tcx>) {
self.engine.borrow_mut().register_predicate_obligation(self.infcx, obligation);
}
pub fn register_obligations(
&self,
obligations: impl IntoIterator<Item = PredicateObligation<'tcx>>,
) {
// Can't use `register_predicate_obligations` because the iterator
// may also use this `ObligationCtxt`.
for obligation in obligations {
self.engine.borrow_mut().register_predicate_obligation(self.infcx, obligation)
}
}
pub fn register_infer_ok_obligations<T>(&self, infer_ok: InferOk<'tcx, T>) -> T {
let InferOk { value, obligations } = infer_ok;
self.engine.borrow_mut().register_predicate_obligations(self.infcx, obligations);
value
}
/// Requires that `ty` must implement the trait with `def_id` in
/// the given environment. This trait must not have any type
/// parameters (except for `Self`).
pub fn register_bound(
&self,
cause: ObligationCause<'tcx>,
param_env: ty::ParamEnv<'tcx>,
ty: Ty<'tcx>,
def_id: DefId,
) {
let tcx = self.infcx.tcx;
let trait_ref = tcx.mk_trait_ref(def_id, [ty]);
self.register_obligation(Obligation {
cause,
recursion_depth: 0,
param_env,
predicate: ty::Binder::dummy(trait_ref).without_const().to_predicate(tcx),
});
}
pub fn normalize<T: TypeFoldable<'tcx>>(
&self,
cause: &ObligationCause<'tcx>,
param_env: ty::ParamEnv<'tcx>,
value: T,
) -> T {
let infer_ok = self.infcx.at(&cause, param_env).normalize(value);
self.register_infer_ok_obligations(infer_ok)
}
/// Makes `expected <: actual`.
pub fn eq_exp<T>(
&self,
cause: &ObligationCause<'tcx>,
param_env: ty::ParamEnv<'tcx>,
a_is_expected: bool,
a: T,
b: T,
) -> Result<(), TypeError<'tcx>>
where
T: ToTrace<'tcx>,
{
self.infcx
.at(cause, param_env)
.eq_exp(a_is_expected, a, b)
.map(|infer_ok| self.register_infer_ok_obligations(infer_ok))
}
pub fn eq<T: ToTrace<'tcx>>(
&self,
cause: &ObligationCause<'tcx>,
param_env: ty::ParamEnv<'tcx>,
expected: T,
actual: T,
) -> Result<(), TypeError<'tcx>> {
self.infcx
.at(cause, param_env)
.eq(expected, actual)
.map(|infer_ok| self.register_infer_ok_obligations(infer_ok))
}
/// Checks whether `expected` is a subtype of `actual`: `expected <: actual`.
pub fn sub<T: ToTrace<'tcx>>(
&self,
cause: &ObligationCause<'tcx>,
param_env: ty::ParamEnv<'tcx>,
expected: T,
actual: T,
) -> Result<(), TypeError<'tcx>> {
self.infcx
.at(cause, param_env)
.sup(expected, actual)
.map(|infer_ok| self.register_infer_ok_obligations(infer_ok))
}
/// Checks whether `expected` is a supertype of `actual`: `expected :> actual`.
pub fn sup<T: ToTrace<'tcx>>(
&self,
cause: &ObligationCause<'tcx>,
param_env: ty::ParamEnv<'tcx>,
expected: T,
actual: T,
) -> Result<(), TypeError<'tcx>> {
self.infcx
.at(cause, param_env)
.sup(expected, actual)
.map(|infer_ok| self.register_infer_ok_obligations(infer_ok))
}
pub fn select_where_possible(&self) -> Vec<FulfillmentError<'tcx>> {
self.engine.borrow_mut().select_where_possible(self.infcx)
}
pub fn select_all_or_error(&self) -> Vec<FulfillmentError<'tcx>> {
self.engine.borrow_mut().select_all_or_error(self.infcx)
}
pub fn assumed_wf_types(
&self,
param_env: ty::ParamEnv<'tcx>,
span: Span,
def_id: LocalDefId,
) -> FxIndexSet<Ty<'tcx>> {
let tcx = self.infcx.tcx;
let assumed_wf_types = tcx.assumed_wf_types(def_id);
let mut implied_bounds = FxIndexSet::default();
let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
let cause = ObligationCause::misc(span, hir_id);
for ty in assumed_wf_types {
// FIXME(@lcnr): rustc currently does not check wf for types
// pre-normalization, meaning that implied bounds are sometimes
// incorrect. See #100910 for more details.
//
// Not adding the unnormalized types here mostly fixes that, except
// that there are projections which are still ambiguous in the item definition
// but do normalize successfully when using the item, see #98543.
//
// Anyways, I will hopefully soon change implied bounds to make all of this
// sound and then uncomment this line again.
// implied_bounds.insert(ty);
let normalized = self.normalize(&cause, param_env, ty);
implied_bounds.insert(normalized);
}
implied_bounds
}
pub fn make_canonicalized_query_response<T>(
&self,
inference_vars: CanonicalVarValues<'tcx>,
answer: T,
) -> Fallible<CanonicalQueryResponse<'tcx, T>>
where
T: Debug + TypeFoldable<'tcx>,
Canonical<'tcx, QueryResponse<'tcx, T>>: ArenaAllocatable<'tcx>,
{
self.infcx.make_canonicalized_query_response(
inference_vars,
answer,
&mut **self.engine.borrow_mut(),
)
}
}
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