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 traits::specialization_graph;
16 use ty::fold::TypeFoldable;
19 use rustc_data_structures::fx::FxHashMap;
23 /// A trait's definition with type information.
27 pub unsafety: hir::Unsafety,
29 /// If `true`, then this trait had the `#[rustc_paren_sugar]`
30 /// attribute, indicating that it should be used with `Foo()`
31 /// sugar. This is a temporary thing -- eventually any trait will
32 /// be usable with the sugar (or without it).
33 pub paren_sugar: bool,
35 pub has_default_impl: bool,
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,
42 pub struct TraitImpls {
43 blanket_impls: Vec<DefId>,
44 /// Impls indexed by their simplified self-type, for fast lookup.
45 non_blanket_impls: FxHashMap<fast_reject::SimplifiedType, Vec<DefId>>,
48 impl<'a, 'gcx, 'tcx> TraitDef {
49 pub fn new(def_id: DefId,
50 unsafety: hir::Unsafety,
52 has_default_impl: bool,
53 def_path_hash: DefPathHash)
64 pub fn ancestors(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>,
66 -> specialization_graph::Ancestors {
67 specialization_graph::ancestors(tcx, self.def_id, of_impl)
71 impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
72 pub fn for_each_impl<F: FnMut(DefId)>(self, def_id: DefId, mut f: F) {
73 let impls = self.trait_impls_of(def_id);
75 for &impl_def_id in impls.blanket_impls.iter() {
79 for v in impls.non_blanket_impls.values() {
80 for &impl_def_id in v {
86 /// Iterate over every impl that could possibly match the
87 /// self-type `self_ty`.
88 pub fn for_each_relevant_impl<F: FnMut(DefId)>(self,
93 let impls = self.trait_impls_of(def_id);
95 for &impl_def_id in impls.blanket_impls.iter() {
99 // simplify_type(.., false) basically replaces type parameters and
100 // projections with infer-variables. This is, of course, done on
101 // the impl trait-ref when it is instantiated, but not on the
102 // predicate trait-ref which is passed here.
104 // for example, if we match `S: Copy` against an impl like
105 // `impl<T:Copy> Copy for Option<T>`, we replace the type variable
106 // in `Option<T>` with an infer variable, to `Option<_>` (this
107 // doesn't actually change fast_reject output), but we don't
108 // replace `S` with anything - this impl of course can't be
109 // selected, and as there are hundreds of similar impls,
110 // considering them would significantly harm performance.
112 // This depends on the set of all impls for the trait. That is
113 // unfortunate. When we get red-green recompilation, we would like
114 // to have a way of knowing whether the set of relevant impls
115 // changed. The most naive
116 // way would be to compute the Vec of relevant impls and see whether
117 // it differs between compilations. That shouldn't be too slow by
118 // itself - we do quite a bit of work for each relevant impl anyway.
120 // If we want to be faster, we could have separate queries for
121 // blanket and non-blanket impls, and compare them separately.
123 // I think we'll cross that bridge when we get to it.
124 if let Some(simp) = fast_reject::simplify_type(self, self_ty, true) {
125 if let Some(impls) = impls.non_blanket_impls.get(&simp) {
126 for &impl_def_id in impls {
131 for v in impls.non_blanket_impls.values() {
132 for &impl_def_id in v {
140 // Query provider for `trait_impls_of`.
141 pub(super) fn trait_impls_of_provider<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
144 let mut remote_impls = Vec::new();
146 // Traits defined in the current crate can't have impls in upstream
147 // crates, so we don't bother querying the cstore.
148 if !trait_id.is_local() {
149 for cnum in tcx.sess.cstore.crates() {
150 let impls = tcx.implementations_of_trait((cnum, trait_id));
151 remote_impls.extend(impls.iter().cloned());
155 let mut blanket_impls = Vec::new();
156 let mut non_blanket_impls = FxHashMap();
158 let local_impls = tcx.hir
159 .trait_impls(trait_id)
161 .map(|&node_id| tcx.hir.local_def_id(node_id));
163 for impl_def_id in local_impls.chain(remote_impls.into_iter()) {
164 let impl_self_ty = tcx.type_of(impl_def_id);
165 if impl_def_id.is_local() && impl_self_ty.references_error() {
169 if let Some(simplified_self_ty) =
170 fast_reject::simplify_type(tcx, impl_self_ty, false)
173 .entry(simplified_self_ty)
177 blanket_impls.push(impl_def_id);
182 blanket_impls: blanket_impls,
183 non_blanket_impls: non_blanket_impls,