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use crate::solve::FulfillmentCtxt;
use crate::traits::query::evaluate_obligation::InferCtxtExt as _;
use crate::traits::{self, DefiningAnchor, ObligationCtxt};
use rustc_hir::def_id::DefId;
use rustc_hir::lang_items::LangItem;
use rustc_infer::traits::{TraitEngine, TraitEngineExt};
use rustc_middle::arena::ArenaAllocatable;
use rustc_middle::infer::canonical::{Canonical, CanonicalQueryResponse, QueryResponse};
use rustc_middle::traits::query::NoSolution;
use rustc_middle::ty::{self, Ty, TyCtxt, TypeFoldable, TypeVisitableExt};
use rustc_middle::ty::{GenericArg, ToPredicate};
use rustc_span::DUMMY_SP;
use std::fmt::Debug;
pub use rustc_infer::infer::*;
pub trait InferCtxtExt<'tcx> {
fn type_is_copy_modulo_regions(&self, param_env: ty::ParamEnv<'tcx>, ty: Ty<'tcx>) -> bool;
fn type_is_sized_modulo_regions(&self, param_env: ty::ParamEnv<'tcx>, ty: Ty<'tcx>) -> bool;
/// Check whether a `ty` implements given trait(trait_def_id).
/// The inputs are:
///
/// - the def-id of the trait
/// - the type parameters of the trait, including the self-type
/// - the parameter environment
///
/// Invokes `evaluate_obligation`, so in the event that evaluating
/// `Ty: Trait` causes overflow, EvaluatedToErrStackDependent (or EvaluatedToAmbigStackDependent)
/// will be returned.
fn type_implements_trait(
&self,
trait_def_id: DefId,
params: impl IntoIterator<Item: Into<GenericArg<'tcx>>>,
param_env: ty::ParamEnv<'tcx>,
) -> traits::EvaluationResult;
fn could_impl_trait(
&self,
trait_def_id: DefId,
ty: Ty<'tcx>,
param_env: ty::ParamEnv<'tcx>,
) -> Option<Vec<traits::FulfillmentError<'tcx>>>;
}
impl<'tcx> InferCtxtExt<'tcx> for InferCtxt<'tcx> {
fn type_is_copy_modulo_regions(&self, param_env: ty::ParamEnv<'tcx>, ty: Ty<'tcx>) -> bool {
let ty = self.resolve_vars_if_possible(ty);
if !(param_env, ty).has_infer() {
return ty.is_copy_modulo_regions(self.tcx, param_env);
}
let copy_def_id = self.tcx.require_lang_item(LangItem::Copy, None);
// This can get called from typeck (by euv), and `moves_by_default`
// rightly refuses to work with inference variables, but
// moves_by_default has a cache, which we want to use in other
// cases.
traits::type_known_to_meet_bound_modulo_regions(self, param_env, ty, copy_def_id)
}
fn type_is_sized_modulo_regions(&self, param_env: ty::ParamEnv<'tcx>, ty: Ty<'tcx>) -> bool {
let lang_item = self.tcx.require_lang_item(LangItem::Sized, None);
traits::type_known_to_meet_bound_modulo_regions(self, param_env, ty, lang_item)
}
#[instrument(level = "debug", skip(self, params), ret)]
fn type_implements_trait(
&self,
trait_def_id: DefId,
params: impl IntoIterator<Item: Into<GenericArg<'tcx>>>,
param_env: ty::ParamEnv<'tcx>,
) -> traits::EvaluationResult {
let trait_ref = ty::TraitRef::new(self.tcx, trait_def_id, params);
let obligation = traits::Obligation {
cause: traits::ObligationCause::dummy(),
param_env,
recursion_depth: 0,
predicate: ty::Binder::dummy(trait_ref).to_predicate(self.tcx),
};
self.evaluate_obligation(&obligation).unwrap_or(traits::EvaluationResult::EvaluatedToErr)
}
fn could_impl_trait(
&self,
trait_def_id: DefId,
ty: Ty<'tcx>,
param_env: ty::ParamEnv<'tcx>,
) -> Option<Vec<traits::FulfillmentError<'tcx>>> {
self.probe(|_snapshot| {
if let ty::Adt(def, args) = ty.kind()
&& let Some((impl_def_id, _)) = self
.tcx
.all_impls(trait_def_id)
.filter_map(|impl_def_id| {
self.tcx.impl_trait_ref(impl_def_id).map(|r| (impl_def_id, r))
})
.map(|(impl_def_id, imp)| (impl_def_id, imp.skip_binder()))
.find(|(_, imp)| match imp.self_ty().peel_refs().kind() {
ty::Adt(i_def, _) if i_def.did() == def.did() => true,
_ => false,
})
{
let mut fulfill_cx = FulfillmentCtxt::new(self);
// We get all obligations from the impl to talk about specific
// trait bounds.
let obligations = self
.tcx
.predicates_of(impl_def_id)
.instantiate(self.tcx, args)
.into_iter()
.map(|(clause, span)| {
traits::Obligation::new(
self.tcx,
traits::ObligationCause::dummy_with_span(span),
param_env,
clause,
)
})
.collect::<Vec<_>>();
fulfill_cx.register_predicate_obligations(self, obligations);
let trait_ref = ty::TraitRef::new(self.tcx, trait_def_id, [ty]);
let obligation = traits::Obligation::new(
self.tcx,
traits::ObligationCause::dummy(),
param_env,
trait_ref,
);
fulfill_cx.register_predicate_obligation(self, obligation);
let mut errors = fulfill_cx.select_all_or_error(self);
// We remove the last predicate failure, which corresponds to
// the top-level obligation, because most of the type we only
// care about the other ones, *except* when it is the only one.
// This seems to only be relevant for arbitrary self-types.
// Look at `tests/ui/moves/move-fn-self-receiver.rs`.
if errors.len() > 1 {
errors.truncate(errors.len() - 1);
}
Some(errors)
} else {
None
}
})
}
}
pub trait InferCtxtBuilderExt<'tcx> {
fn enter_canonical_trait_query<K, R>(
self,
canonical_key: &Canonical<'tcx, K>,
operation: impl FnOnce(&ObligationCtxt<'_, 'tcx>, K) -> Result<R, NoSolution>,
) -> Result<CanonicalQueryResponse<'tcx, R>, NoSolution>
where
K: TypeFoldable<TyCtxt<'tcx>>,
R: Debug + TypeFoldable<TyCtxt<'tcx>>,
Canonical<'tcx, QueryResponse<'tcx, R>>: ArenaAllocatable<'tcx>;
}
impl<'tcx> InferCtxtBuilderExt<'tcx> for InferCtxtBuilder<'tcx> {
/// The "main method" for a canonicalized trait query. Given the
/// canonical key `canonical_key`, this method will create a new
/// inference context, instantiate the key, and run your operation
/// `op`. The operation should yield up a result (of type `R`) as
/// well as a set of trait obligations that must be fully
/// satisfied. These obligations will be processed and the
/// canonical result created.
///
/// Returns `NoSolution` in the event of any error.
///
/// (It might be mildly nicer to implement this on `TyCtxt`, and
/// not `InferCtxtBuilder`, but that is a bit tricky right now.
/// In part because we would need a `for<'tcx>` sort of
/// bound for the closure and in part because it is convenient to
/// have `'tcx` be free on this function so that we can talk about
/// `K: TypeFoldable<TyCtxt<'tcx>>`.)
fn enter_canonical_trait_query<K, R>(
self,
canonical_key: &Canonical<'tcx, K>,
operation: impl FnOnce(&ObligationCtxt<'_, 'tcx>, K) -> Result<R, NoSolution>,
) -> Result<CanonicalQueryResponse<'tcx, R>, NoSolution>
where
K: TypeFoldable<TyCtxt<'tcx>>,
R: Debug + TypeFoldable<TyCtxt<'tcx>>,
Canonical<'tcx, QueryResponse<'tcx, R>>: ArenaAllocatable<'tcx>,
{
let (infcx, key, canonical_inference_vars) = self
.with_opaque_type_inference(DefiningAnchor::Bubble)
.build_with_canonical(DUMMY_SP, canonical_key);
let ocx = ObligationCtxt::new(&infcx);
let value = operation(&ocx, key)?;
ocx.make_canonicalized_query_response(canonical_inference_vars, value)
}
}
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