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use crate::rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt;
use rustc_hir as hir;
use rustc_infer::infer::{InferOk, TyCtxtInferExt};
use rustc_infer::traits;
use rustc_middle::ty::subst::Subst;
use rustc_middle::ty::ToPredicate;
use rustc_span::DUMMY_SP;
use super::*;
pub(crate) struct BlanketImplFinder<'a, 'tcx> {
pub(crate) cx: &'a mut core::DocContext<'tcx>,
}
impl<'a, 'tcx> BlanketImplFinder<'a, 'tcx> {
pub(crate) fn get_blanket_impls(&mut self, item_def_id: DefId) -> Vec<Item> {
let param_env = self.cx.tcx.param_env(item_def_id);
let ty = self.cx.tcx.bound_type_of(item_def_id);
trace!("get_blanket_impls({:?})", ty);
let mut impls = Vec::new();
self.cx.with_all_traits(|cx, all_traits| {
for &trait_def_id in all_traits {
if !cx.cache.access_levels.is_public(trait_def_id)
|| cx.generated_synthetics.get(&(ty.0, trait_def_id)).is_some()
{
continue;
}
// NOTE: doesn't use `for_each_relevant_impl` to avoid looking at anything besides blanket impls
let trait_impls = cx.tcx.trait_impls_of(trait_def_id);
for &impl_def_id in trait_impls.blanket_impls() {
trace!(
"get_blanket_impls: Considering impl for trait '{:?}' {:?}",
trait_def_id,
impl_def_id
);
let trait_ref = cx.tcx.bound_impl_trait_ref(impl_def_id).unwrap();
let is_param = matches!(trait_ref.0.self_ty().kind(), ty::Param(_));
let may_apply = is_param && cx.tcx.infer_ctxt().enter(|infcx| {
let substs = infcx.fresh_substs_for_item(DUMMY_SP, item_def_id);
let ty = ty.subst(infcx.tcx, substs);
let param_env = EarlyBinder(param_env).subst(infcx.tcx, substs);
let impl_substs = infcx.fresh_substs_for_item(DUMMY_SP, impl_def_id);
let trait_ref = trait_ref.subst(infcx.tcx, impl_substs);
// Require the type the impl is implemented on to match
// our type, and ignore the impl if there was a mismatch.
let cause = traits::ObligationCause::dummy();
let eq_result = infcx.at(&cause, param_env).eq(trait_ref.self_ty(), ty);
if let Ok(InferOk { value: (), obligations }) = eq_result {
// FIXME(eddyb) ignoring `obligations` might cause false positives.
drop(obligations);
trace!(
"invoking predicate_may_hold: param_env={:?}, trait_ref={:?}, ty={:?}",
param_env,
trait_ref,
ty
);
let predicates = cx
.tcx
.predicates_of(impl_def_id)
.instantiate(cx.tcx, impl_substs)
.predicates
.into_iter()
.chain(Some(
ty::Binder::dummy(trait_ref)
.to_poly_trait_predicate()
.map_bound(ty::PredicateKind::Trait)
.to_predicate(infcx.tcx),
));
for predicate in predicates {
debug!("testing predicate {:?}", predicate);
let obligation = traits::Obligation::new(
traits::ObligationCause::dummy(),
param_env,
predicate,
);
match infcx.evaluate_obligation(&obligation) {
Ok(eval_result) if eval_result.may_apply() => {}
Err(traits::OverflowError::Canonical) => {}
Err(traits::OverflowError::ErrorReporting) => {}
_ => {
return false;
}
}
}
true
} else {
false
}
});
debug!(
"get_blanket_impls: found applicable impl: {} for trait_ref={:?}, ty={:?}",
may_apply, trait_ref, ty
);
if !may_apply {
continue;
}
cx.generated_synthetics.insert((ty.0, trait_def_id));
impls.push(Item {
name: None,
attrs: Default::default(),
visibility: Inherited,
item_id: ItemId::Blanket { impl_id: impl_def_id, for_: item_def_id },
kind: Box::new(ImplItem(Box::new(Impl {
unsafety: hir::Unsafety::Normal,
generics: clean_ty_generics(
cx,
cx.tcx.generics_of(impl_def_id),
cx.tcx.explicit_predicates_of(impl_def_id),
),
// FIXME(eddyb) compute both `trait_` and `for_` from
// the post-inference `trait_ref`, as it's more accurate.
trait_: Some(clean_trait_ref_with_bindings(cx, trait_ref.0, ThinVec::new())),
for_: clean_middle_ty(ty.0, cx, None),
items: cx.tcx
.associated_items(impl_def_id)
.in_definition_order()
.map(|x| clean_middle_assoc_item(x, cx))
.collect::<Vec<_>>(),
polarity: ty::ImplPolarity::Positive,
kind: ImplKind::Blanket(Box::new(clean_middle_ty(trait_ref.0.self_ty(), cx, None))),
}))),
cfg: None,
});
}
}
});
impls
}
}
|
