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,
23 use rustc_data_structures::sync::Lrc;
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,
45 pub struct TraitImpls {
46 blanket_impls: Vec<DefId>,
47 /// Impls indexed by their simplified self-type, for fast lookup.
48 non_blanket_impls: FxHashMap<fast_reject::SimplifiedType, Vec<DefId>>,
51 impl<'a, 'gcx, 'tcx> TraitDef {
52 pub fn new(def_id: DefId,
53 unsafety: hir::Unsafety,
56 def_path_hash: DefPathHash)
67 pub fn ancestors(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>,
69 -> specialization_graph::Ancestors {
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 v in impls.non_blanket_impls.values() {
135 for &impl_def_id in v {
143 // Query provider for `trait_impls_of`.
144 pub(super) fn trait_impls_of_provider<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
147 let mut impls = TraitImpls::default();
150 let mut add_impl = |impl_def_id| {
151 let impl_self_ty = tcx.type_of(impl_def_id);
152 if impl_def_id.is_local() && impl_self_ty.references_error() {
156 if let Some(simplified_self_ty) =
157 fast_reject::simplify_type(tcx, impl_self_ty, false)
159 impls.non_blanket_impls
160 .entry(simplified_self_ty)
164 impls.blanket_impls.push(impl_def_id);
168 // Traits defined in the current crate can't have impls in upstream
169 // crates, so we don't bother querying the cstore.
170 if !trait_id.is_local() {
171 for &cnum in tcx.crates().iter() {
172 for &def_id in tcx.implementations_of_trait((cnum, trait_id)).iter() {
178 for &node_id in tcx.hir.trait_impls(trait_id) {
179 add_impl(tcx.hir.local_def_id(node_id));
186 impl<'a> HashStable<StableHashingContext<'a>> for TraitImpls {
187 fn hash_stable<W: StableHasherResult>(&self,
188 hcx: &mut StableHashingContext<'a>,
189 hasher: &mut StableHasher<W>) {
192 ref non_blanket_impls,
195 ich::hash_stable_trait_impls(hcx, hasher, blanket_impls, non_blanket_impls);