2 use crate::hir::def_id::DefId;
3 use crate::hir::map::DefPathHash;
4 use crate::ich::{self, StableHashingContext};
5 use crate::traits::specialization_graph;
6 use crate::ty::fast_reject;
7 use crate::ty::fold::TypeFoldable;
8 use crate::ty::{Ty, TyCtxt};
10 use rustc_data_structures::fx::FxHashMap;
11 use rustc_data_structures::stable_hasher::{HashStable, StableHasher,
13 use rustc_macros::HashStable;
15 /// A trait's definition with type information.
18 // We already have the def_path_hash below, no need to hash it twice
19 #[stable_hasher(ignore)]
22 pub unsafety: hir::Unsafety,
24 /// If `true`, then this trait had the `#[rustc_paren_sugar]`
25 /// attribute, indicating that it should be used with `Foo()`
26 /// sugar. This is a temporary thing -- eventually any trait will
27 /// be usable with the sugar (or without it).
28 pub paren_sugar: bool,
30 pub has_auto_impl: bool,
32 /// If `true`, then this trait has the `#[marker]` attribute, indicating
33 /// that all its associated items have defaults that cannot be overridden,
34 /// and thus `impl`s of it are allowed to overlap.
37 /// The ICH of this trait's DefPath, cached here so it doesn't have to be
38 /// recomputed all the time.
39 pub def_path_hash: DefPathHash,
43 pub struct TraitImpls {
44 blanket_impls: Vec<DefId>,
45 /// Impls indexed by their simplified self type, for fast lookup.
46 non_blanket_impls: FxHashMap<fast_reject::SimplifiedType, Vec<DefId>>,
49 impl<'a, 'gcx, 'tcx> TraitDef {
50 pub fn new(def_id: DefId,
51 unsafety: hir::Unsafety,
55 def_path_hash: DefPathHash)
67 pub fn ancestors(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>,
69 -> specialization_graph::Ancestors<'gcx> {
70 specialization_graph::ancestors(tcx, self.def_id, of_impl)
74 impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
75 pub fn for_each_impl<F: FnMut(DefId)>(self, def_id: DefId, mut f: F) {
76 let impls = self.trait_impls_of(def_id);
78 for &impl_def_id in impls.blanket_impls.iter() {
82 for v in impls.non_blanket_impls.values() {
83 for &impl_def_id in v {
89 /// Iterate over every impl that could possibly match the
90 /// self type `self_ty`.
91 pub fn for_each_relevant_impl<F: FnMut(DefId)>(self,
96 let impls = self.trait_impls_of(def_id);
98 for &impl_def_id in impls.blanket_impls.iter() {
102 // simplify_type(.., false) basically replaces type parameters and
103 // projections with infer-variables. This is, of course, done on
104 // the impl trait-ref when it is instantiated, but not on the
105 // predicate trait-ref which is passed here.
107 // for example, if we match `S: Copy` against an impl like
108 // `impl<T:Copy> Copy for Option<T>`, we replace the type variable
109 // in `Option<T>` with an infer variable, to `Option<_>` (this
110 // doesn't actually change fast_reject output), but we don't
111 // replace `S` with anything - this impl of course can't be
112 // selected, and as there are hundreds of similar impls,
113 // considering them would significantly harm performance.
115 // This depends on the set of all impls for the trait. That is
116 // unfortunate. When we get red-green recompilation, we would like
117 // to have a way of knowing whether the set of relevant impls
118 // changed. The most naive
119 // way would be to compute the Vec of relevant impls and see whether
120 // it differs between compilations. That shouldn't be too slow by
121 // itself - we do quite a bit of work for each relevant impl anyway.
123 // If we want to be faster, we could have separate queries for
124 // blanket and non-blanket impls, and compare them separately.
126 // I think we'll cross that bridge when we get to it.
127 if let Some(simp) = fast_reject::simplify_type(self, self_ty, true) {
128 if let Some(impls) = impls.non_blanket_impls.get(&simp) {
129 for &impl_def_id in impls {
134 for &impl_def_id in impls.non_blanket_impls.values().flatten() {
140 /// Returns a vector containing all impls
141 pub fn all_impls(self, def_id: DefId) -> Vec<DefId> {
142 let impls = self.trait_impls_of(def_id);
144 impls.blanket_impls.iter().chain(
145 impls.non_blanket_impls.values().flatten()
150 // Query provider for `trait_impls_of`.
151 pub(super) fn trait_impls_of_provider<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
153 -> &'tcx TraitImpls {
154 let mut impls = TraitImpls::default();
157 let mut add_impl = |impl_def_id| {
158 let impl_self_ty = tcx.type_of(impl_def_id);
159 if impl_def_id.is_local() && impl_self_ty.references_error() {
163 if let Some(simplified_self_ty) =
164 fast_reject::simplify_type(tcx, impl_self_ty, false)
166 impls.non_blanket_impls
167 .entry(simplified_self_ty)
171 impls.blanket_impls.push(impl_def_id);
175 // Traits defined in the current crate can't have impls in upstream
176 // crates, so we don't bother querying the cstore.
177 if !trait_id.is_local() {
178 for &cnum in tcx.crates().iter() {
179 for &def_id in tcx.implementations_of_trait((cnum, trait_id)).iter() {
185 for &hir_id in tcx.hir().trait_impls(trait_id) {
186 add_impl(tcx.hir().local_def_id_from_hir_id(hir_id));
190 tcx.arena.alloc(impls)
193 impl<'a> HashStable<StableHashingContext<'a>> for TraitImpls {
194 fn hash_stable<W: StableHasherResult>(&self,
195 hcx: &mut StableHashingContext<'a>,
196 hasher: &mut StableHasher<W>) {
199 ref non_blanket_impls,
202 ich::hash_stable_trait_impls(hcx, hasher, blanket_impls, non_blanket_impls);