1 // Copyright 2012-2015 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
12 use hir::def_id::DefId;
13 use hir::map::DefPathHash;
14 use ich::{self, StableHashingContext};
15 use traits::specialization_graph;
17 use ty::fold::TypeFoldable;
20 use rustc_data_structures::fx::FxHashMap;
21 use rustc_data_structures::stable_hasher::{HashStable, StableHasher,
25 /// A trait's definition with type information.
29 pub unsafety: hir::Unsafety,
31 /// If `true`, then this trait had the `#[rustc_paren_sugar]`
32 /// attribute, indicating that it should be used with `Foo()`
33 /// sugar. This is a temporary thing -- eventually any trait will
34 /// be usable with the sugar (or without it).
35 pub paren_sugar: bool,
37 pub has_auto_impl: bool,
39 /// The ICH of this trait's DefPath, cached here so it doesn't have to be
40 /// recomputed all the time.
41 pub def_path_hash: DefPathHash,
44 pub struct TraitImpls {
45 blanket_impls: Vec<DefId>,
46 /// Impls indexed by their simplified self-type, for fast lookup.
47 non_blanket_impls: FxHashMap<fast_reject::SimplifiedType, Vec<DefId>>,
50 impl<'a, 'gcx, 'tcx> TraitDef {
51 pub fn new(def_id: DefId,
52 unsafety: hir::Unsafety,
55 def_path_hash: DefPathHash)
66 pub fn ancestors(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>,
68 -> specialization_graph::Ancestors {
69 specialization_graph::ancestors(tcx, self.def_id, of_impl)
73 impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
74 pub fn for_each_impl<F: FnMut(DefId)>(self, def_id: DefId, mut f: F) {
75 let impls = self.trait_impls_of(def_id);
77 for &impl_def_id in impls.blanket_impls.iter() {
81 for v in impls.non_blanket_impls.values() {
82 for &impl_def_id in v {
88 /// Iterate over every impl that could possibly match the
89 /// self-type `self_ty`.
90 pub fn for_each_relevant_impl<F: FnMut(DefId)>(self,
95 let impls = self.trait_impls_of(def_id);
97 for &impl_def_id in impls.blanket_impls.iter() {
101 // simplify_type(.., false) basically replaces type parameters and
102 // projections with infer-variables. This is, of course, done on
103 // the impl trait-ref when it is instantiated, but not on the
104 // predicate trait-ref which is passed here.
106 // for example, if we match `S: Copy` against an impl like
107 // `impl<T:Copy> Copy for Option<T>`, we replace the type variable
108 // in `Option<T>` with an infer variable, to `Option<_>` (this
109 // doesn't actually change fast_reject output), but we don't
110 // replace `S` with anything - this impl of course can't be
111 // selected, and as there are hundreds of similar impls,
112 // considering them would significantly harm performance.
114 // This depends on the set of all impls for the trait. That is
115 // unfortunate. When we get red-green recompilation, we would like
116 // to have a way of knowing whether the set of relevant impls
117 // changed. The most naive
118 // way would be to compute the Vec of relevant impls and see whether
119 // it differs between compilations. That shouldn't be too slow by
120 // itself - we do quite a bit of work for each relevant impl anyway.
122 // If we want to be faster, we could have separate queries for
123 // blanket and non-blanket impls, and compare them separately.
125 // I think we'll cross that bridge when we get to it.
126 if let Some(simp) = fast_reject::simplify_type(self, self_ty, true) {
127 if let Some(impls) = impls.non_blanket_impls.get(&simp) {
128 for &impl_def_id in impls {
133 for v in impls.non_blanket_impls.values() {
134 for &impl_def_id in v {
142 // Query provider for `trait_impls_of`.
143 pub(super) fn trait_impls_of_provider<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
146 let mut remote_impls = Vec::new();
148 // Traits defined in the current crate can't have impls in upstream
149 // crates, so we don't bother querying the cstore.
150 if !trait_id.is_local() {
151 for &cnum in tcx.crates().iter() {
152 let impls = tcx.implementations_of_trait((cnum, trait_id));
153 remote_impls.extend(impls.iter().cloned());
157 let mut blanket_impls = Vec::new();
158 let mut non_blanket_impls = FxHashMap();
160 let local_impls = tcx.hir
161 .trait_impls(trait_id)
163 .map(|&node_id| tcx.hir.local_def_id(node_id));
165 for impl_def_id in local_impls.chain(remote_impls.into_iter()) {
166 let impl_self_ty = tcx.type_of(impl_def_id);
167 if impl_def_id.is_local() && impl_self_ty.references_error() {
171 if let Some(simplified_self_ty) =
172 fast_reject::simplify_type(tcx, impl_self_ty, false)
175 .entry(simplified_self_ty)
179 blanket_impls.push(impl_def_id);
184 blanket_impls: blanket_impls,
185 non_blanket_impls: non_blanket_impls,
189 impl<'gcx> HashStable<StableHashingContext<'gcx>> for TraitImpls {
190 fn hash_stable<W: StableHasherResult>(&self,
191 hcx: &mut StableHashingContext<'gcx>,
192 hasher: &mut StableHasher<W>) {
195 ref non_blanket_impls,
198 ich::hash_stable_trait_impls(hcx, hasher, blanket_impls, non_blanket_impls);