1 use crate::rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt;
3 use rustc_infer::infer::{InferOk, TyCtxtInferExt};
4 use rustc_infer::traits;
5 use rustc_middle::ty::subst::Subst;
6 use rustc_middle::ty::ToPredicate;
7 use rustc_span::DUMMY_SP;
11 pub(crate) struct BlanketImplFinder<'a, 'tcx> {
12 pub(crate) cx: &'a mut core::DocContext<'tcx>,
15 impl<'a, 'tcx> BlanketImplFinder<'a, 'tcx> {
16 pub(crate) fn get_blanket_impls(&mut self, item_def_id: DefId) -> Vec<Item> {
17 let param_env = self.cx.tcx.param_env(item_def_id);
18 let ty = self.cx.tcx.bound_type_of(item_def_id);
20 trace!("get_blanket_impls({:?})", ty);
21 let mut impls = Vec::new();
22 self.cx.with_all_traits(|cx, all_traits| {
23 for &trait_def_id in all_traits {
24 if !cx.cache.access_levels.is_public(trait_def_id)
25 || cx.generated_synthetics.get(&(ty.0, trait_def_id)).is_some()
29 // NOTE: doesn't use `for_each_relevant_impl` to avoid looking at anything besides blanket impls
30 let trait_impls = cx.tcx.trait_impls_of(trait_def_id);
31 for &impl_def_id in trait_impls.blanket_impls() {
33 "get_blanket_impls: Considering impl for trait '{:?}' {:?}",
37 let trait_ref = cx.tcx.bound_impl_trait_ref(impl_def_id).unwrap();
38 let is_param = matches!(trait_ref.0.self_ty().kind(), ty::Param(_));
39 let may_apply = is_param && cx.tcx.infer_ctxt().enter(|infcx| {
40 let substs = infcx.fresh_substs_for_item(DUMMY_SP, item_def_id);
41 let ty = ty.subst(infcx.tcx, substs);
42 let param_env = EarlyBinder(param_env).subst(infcx.tcx, substs);
44 let impl_substs = infcx.fresh_substs_for_item(DUMMY_SP, impl_def_id);
45 let trait_ref = trait_ref.subst(infcx.tcx, impl_substs);
47 // Require the type the impl is implemented on to match
48 // our type, and ignore the impl if there was a mismatch.
49 let cause = traits::ObligationCause::dummy();
50 let eq_result = infcx.at(&cause, param_env).eq(trait_ref.self_ty(), ty);
51 if let Ok(InferOk { value: (), obligations }) = eq_result {
52 // FIXME(eddyb) ignoring `obligations` might cause false positives.
56 "invoking predicate_may_hold: param_env={:?}, trait_ref={:?}, ty={:?}",
63 .predicates_of(impl_def_id)
64 .instantiate(cx.tcx, impl_substs)
68 ty::Binder::dummy(trait_ref)
69 .to_poly_trait_predicate()
70 .map_bound(ty::PredicateKind::Trait)
71 .to_predicate(infcx.tcx),
73 for predicate in predicates {
74 debug!("testing predicate {:?}", predicate);
75 let obligation = traits::Obligation::new(
76 traits::ObligationCause::dummy(),
80 match infcx.evaluate_obligation(&obligation) {
81 Ok(eval_result) if eval_result.may_apply() => {}
82 Err(traits::OverflowError::Canonical) => {}
83 Err(traits::OverflowError::ErrorReporting) => {}
95 "get_blanket_impls: found applicable impl: {} for trait_ref={:?}, ty={:?}",
96 may_apply, trait_ref, ty
102 cx.generated_synthetics.insert((ty.0, trait_def_id));
106 attrs: Default::default(),
107 visibility: Inherited,
108 item_id: ItemId::Blanket { impl_id: impl_def_id, for_: item_def_id },
109 kind: box ImplItem(Impl {
110 unsafety: hir::Unsafety::Normal,
111 generics: clean_ty_generics(
113 cx.tcx.generics_of(impl_def_id),
114 cx.tcx.explicit_predicates_of(impl_def_id),
116 // FIXME(eddyb) compute both `trait_` and `for_` from
117 // the post-inference `trait_ref`, as it's more accurate.
118 trait_: Some(trait_ref.0.clean(cx)),
119 for_: ty.0.clean(cx),
121 .associated_items(impl_def_id)
122 .in_definition_order()
123 .map(|x| x.clean(cx))
124 .collect::<Vec<_>>(),
125 polarity: ty::ImplPolarity::Positive,
126 kind: ImplKind::Blanket(box trait_ref.0.self_ty().clean(cx)),