3 use rustc::ty::ToPredicate;
4 use rustc::ty::subst::Subst;
5 use rustc::infer::InferOk;
6 use rustc::hir::def_id::LOCAL_CRATE;
7 use syntax_pos::DUMMY_SP;
11 pub struct BlanketImplFinder<'a, 'tcx> {
12 pub cx: &'a core::DocContext<'tcx>,
15 impl<'a, 'tcx> BlanketImplFinder<'a, 'tcx> {
16 pub fn new(cx: &'a core::DocContext<'tcx>) -> Self {
17 BlanketImplFinder { cx }
20 // FIXME(eddyb) figure out a better way to pass information about
21 // parametrization of `ty` than `param_env_def_id`.
22 pub fn get_blanket_impls(
25 param_env_def_id: DefId,
27 let param_env = self.cx.tcx.param_env(param_env_def_id);
29 debug!("get_blanket_impls({:?})", ty);
30 let mut impls = Vec::new();
31 for &trait_def_id in self.cx.tcx.all_traits(LOCAL_CRATE).iter() {
32 if !self.cx.renderinfo.borrow().access_levels.is_public(trait_def_id) ||
33 self.cx.generated_synthetics
35 .get(&(ty, trait_def_id))
39 self.cx.tcx.for_each_relevant_impl(trait_def_id, ty, |impl_def_id| {
40 debug!("get_blanket_impls: Considering impl for trait '{:?}' {:?}",
41 trait_def_id, impl_def_id);
42 let trait_ref = self.cx.tcx.impl_trait_ref(impl_def_id).unwrap();
43 let may_apply = self.cx.tcx.infer_ctxt().enter(|infcx| {
44 match trait_ref.self_ty().kind {
49 let substs = infcx.fresh_substs_for_item(DUMMY_SP, param_env_def_id);
50 let ty = ty.subst(infcx.tcx, substs);
51 let param_env = param_env.subst(infcx.tcx, substs);
53 let impl_substs = infcx.fresh_substs_for_item(DUMMY_SP, impl_def_id);
54 let trait_ref = trait_ref.subst(infcx.tcx, impl_substs);
56 // Require the type the impl is implemented on to match
57 // our type, and ignore the impl if there was a mismatch.
58 let cause = traits::ObligationCause::dummy();
59 let eq_result = infcx.at(&cause, param_env)
60 .eq(trait_ref.self_ty(), ty);
61 if let Ok(InferOk { value: (), obligations }) = eq_result {
62 // FIXME(eddyb) ignoring `obligations` might cause false positives.
66 "invoking predicate_may_hold: param_env={:?}, trait_ref={:?}, ty={:?}",
67 param_env, trait_ref, ty
69 match infcx.evaluate_obligation(
70 &traits::Obligation::new(
73 trait_ref.to_predicate(),
76 Ok(eval_result) => eval_result.may_apply(),
77 Err(traits::OverflowError) => true, // overflow doesn't mean yes *or* no
83 debug!("get_blanket_impls: found applicable impl: {}\
84 for trait_ref={:?}, ty={:?}",
85 may_apply, trait_ref, ty);
90 self.cx.generated_synthetics.borrow_mut()
91 .insert((ty, trait_def_id));
92 let provided_trait_methods =
93 self.cx.tcx.provided_trait_methods(trait_def_id)
95 .map(|meth| meth.ident.to_string())
99 source: self.cx.tcx.def_span(impl_def_id).clean(self.cx),
101 attrs: Default::default(),
102 visibility: Inherited,
103 def_id: self.cx.next_def_id(impl_def_id.krate),
106 inner: ImplItem(Impl {
107 unsafety: hir::Unsafety::Normal,
109 self.cx.tcx.generics_of(impl_def_id),
110 self.cx.tcx.explicit_predicates_of(impl_def_id),
112 provided_trait_methods,
113 // FIXME(eddyb) compute both `trait_` and `for_` from
114 // the post-inference `trait_ref`, as it's more accurate.
115 trait_: Some(trait_ref.clean(self.cx).get_trait_type().unwrap()),
116 for_: ty.clean(self.cx),
117 items: self.cx.tcx.associated_items(impl_def_id)
122 blanket_impl: Some(trait_ref.self_ty().clean(self.cx)),