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, WithConstness};
7 use rustc_span::DUMMY_SP;
11 crate struct BlanketImplFinder<'a, 'tcx> {
12 crate cx: &'a mut core::DocContext<'tcx>,
15 impl<'a, 'tcx> BlanketImplFinder<'a, 'tcx> {
16 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.type_of(item_def_id);
20 debug!("get_blanket_impls({:?})", ty);
21 let mut impls = Vec::new();
22 for &trait_def_id in self.cx.tcx.all_traits(()).iter() {
23 if !self.cx.cache.access_levels.is_public(trait_def_id)
24 || self.cx.generated_synthetics.get(&(ty, trait_def_id)).is_some()
28 // NOTE: doesn't use `for_each_relevant_impl` to avoid looking at anything besides blanket impls
29 let trait_impls = self.cx.tcx.trait_impls_of(trait_def_id);
30 for &impl_def_id in trait_impls.blanket_impls() {
32 "get_blanket_impls: Considering impl for trait '{:?}' {:?}",
33 trait_def_id, impl_def_id
35 let trait_ref = self.cx.tcx.impl_trait_ref(impl_def_id).unwrap();
36 let is_param = matches!(trait_ref.self_ty().kind(), ty::Param(_));
37 let may_apply = is_param && self.cx.tcx.infer_ctxt().enter(|infcx| {
38 let substs = infcx.fresh_substs_for_item(DUMMY_SP, item_def_id);
39 let ty = ty.subst(infcx.tcx, substs);
40 let param_env = param_env.subst(infcx.tcx, substs);
42 let impl_substs = infcx.fresh_substs_for_item(DUMMY_SP, impl_def_id);
43 let trait_ref = trait_ref.subst(infcx.tcx, impl_substs);
45 // Require the type the impl is implemented on to match
46 // our type, and ignore the impl if there was a mismatch.
47 let cause = traits::ObligationCause::dummy();
48 let eq_result = infcx.at(&cause, param_env).eq(trait_ref.self_ty(), ty);
49 if let Ok(InferOk { value: (), obligations }) = eq_result {
50 // FIXME(eddyb) ignoring `obligations` might cause false positives.
54 "invoking predicate_may_hold: param_env={:?}, trait_ref={:?}, ty={:?}",
55 param_env, trait_ref, ty
60 .predicates_of(impl_def_id)
61 .instantiate(self.cx.tcx, impl_substs)
64 .chain(Some(trait_ref.without_const().to_predicate(infcx.tcx)));
65 for predicate in predicates {
66 debug!("testing predicate {:?}", predicate);
67 let obligation = traits::Obligation::new(
68 traits::ObligationCause::dummy(),
72 match infcx.evaluate_obligation(&obligation) {
73 Ok(eval_result) if eval_result.may_apply() => {}
74 Err(traits::OverflowError) => {}
86 "get_blanket_impls: found applicable impl: {} for trait_ref={:?}, ty={:?}",
87 may_apply, trait_ref, ty
93 self.cx.generated_synthetics.insert((ty, trait_def_id));
97 attrs: Default::default(),
98 visibility: Inherited,
99 def_id: FakeDefId::new_fake(item_def_id.krate),
100 kind: box ImplItem(Impl {
101 span: self.cx.tcx.def_span(impl_def_id).clean(self.cx),
102 unsafety: hir::Unsafety::Normal,
104 self.cx.tcx.generics_of(impl_def_id),
105 self.cx.tcx.explicit_predicates_of(impl_def_id),
108 // FIXME(eddyb) compute both `trait_` and `for_` from
109 // the post-inference `trait_ref`, as it's more accurate.
110 trait_: Some(trait_ref.clean(self.cx).get_trait_type().unwrap()),
111 for_: ty.clean(self.cx),
115 .associated_items(impl_def_id)
116 .in_definition_order()
119 negative_polarity: false,
121 blanket_impl: Some(box trait_ref.self_ty().clean(self.cx)),