1 use crate::traits::specialization_graph;
2 use crate::ty::fast_reject::{self, SimplifiedType, SimplifyParams};
3 use crate::ty::fold::TypeFoldable;
4 use crate::ty::{Ident, Ty, TyCtxt};
6 use rustc_hir::def_id::DefId;
7 use rustc_hir::definitions::DefPathHash;
9 use rustc_data_structures::fx::FxIndexMap;
10 use rustc_errors::ErrorGuaranteed;
11 use rustc_macros::HashStable;
13 /// A trait's definition with type information.
16 // We already have the def_path_hash below, no need to hash it twice
17 #[stable_hasher(ignore)]
20 pub unsafety: hir::Unsafety,
22 /// If `true`, then this trait had the `#[rustc_paren_sugar]`
23 /// attribute, indicating that it should be used with `Foo()`
24 /// sugar. This is a temporary thing -- eventually any trait will
25 /// be usable with the sugar (or without it).
26 pub paren_sugar: bool,
28 pub has_auto_impl: bool,
30 /// If `true`, then this trait has the `#[marker]` attribute, indicating
31 /// that all its associated items have defaults that cannot be overridden,
32 /// and thus `impl`s of it are allowed to overlap.
35 /// If `true`, then this trait has the `#[rustc_skip_array_during_method_dispatch]`
36 /// attribute, indicating that editions before 2021 should not consider this trait
37 /// during method dispatch if the receiver is an array.
38 pub skip_array_during_method_dispatch: bool,
40 /// Used to determine whether the standard library is allowed to specialize
42 pub specialization_kind: TraitSpecializationKind,
44 /// The ICH of this trait's DefPath, cached here so it doesn't have to be
45 /// recomputed all the time.
46 pub def_path_hash: DefPathHash,
48 /// List of functions from `#[rustc_must_implement_one_of]` attribute one of which
49 /// must be implemented.
50 pub must_implement_one_of: Option<Box<[Ident]>>,
53 /// Whether this trait is treated specially by the standard library
54 /// specialization lint.
55 #[derive(HashStable, PartialEq, Clone, Copy, TyEncodable, TyDecodable)]
56 pub enum TraitSpecializationKind {
57 /// The default. Specializing on this trait is not allowed.
59 /// Specializing on this trait is allowed because it doesn't have any
60 /// methods. For example `Sized` or `FusedIterator`.
61 /// Applies to traits with the `rustc_unsafe_specialization_marker`
64 /// Specializing on this trait is allowed because all of the impls of this
65 /// trait are "always applicable". Always applicable means that if
66 /// `X<'x>: T<'y>` for any lifetimes, then `for<'a, 'b> X<'a>: T<'b>`.
67 /// Applies to traits with the `rustc_specialization_trait` attribute.
71 #[derive(Default, Debug, HashStable)]
72 pub struct TraitImpls {
73 blanket_impls: Vec<DefId>,
74 /// Impls indexed by their simplified self type, for fast lookup.
75 non_blanket_impls: FxIndexMap<SimplifiedType, Vec<DefId>>,
79 pub fn blanket_impls(&self) -> &[DefId] {
80 self.blanket_impls.as_slice()
87 unsafety: hir::Unsafety,
91 skip_array_during_method_dispatch: bool,
92 specialization_kind: TraitSpecializationKind,
93 def_path_hash: DefPathHash,
94 must_implement_one_of: Option<Box<[Ident]>>,
102 skip_array_during_method_dispatch,
105 must_implement_one_of,
113 ) -> Result<specialization_graph::Ancestors<'tcx>, ErrorGuaranteed> {
114 specialization_graph::ancestors(tcx, self.def_id, of_impl)
118 impl<'tcx> TyCtxt<'tcx> {
119 pub fn for_each_impl<F: FnMut(DefId)>(self, def_id: DefId, mut f: F) {
120 let impls = self.trait_impls_of(def_id);
122 for &impl_def_id in impls.blanket_impls.iter() {
126 for v in impls.non_blanket_impls.values() {
127 for &impl_def_id in v {
133 /// Iterate over every impl that could possibly match the
134 /// self type `self_ty`.
135 pub fn for_each_relevant_impl<F: FnMut(DefId)>(
141 let _: Option<()> = self.find_map_relevant_impl(def_id, self_ty, |did| {
147 pub fn non_blanket_impls_for_ty(
151 ) -> impl Iterator<Item = DefId> + 'tcx {
152 let impls = self.trait_impls_of(def_id);
153 if let Some(simp) = fast_reject::simplify_type(self, self_ty, SimplifyParams::No) {
154 if let Some(impls) = impls.non_blanket_impls.get(&simp) {
155 return impls.iter().copied();
162 /// Applies function to every impl that could possibly match the self type `self_ty` and returns
163 /// the first non-none value.
164 pub fn find_map_relevant_impl<T, F: FnMut(DefId) -> Option<T>>(
170 // FIXME: This depends on the set of all impls for the trait. That is
171 // unfortunate wrt. incremental compilation.
173 // If we want to be faster, we could have separate queries for
174 // blanket and non-blanket impls, and compare them separately.
175 let impls = self.trait_impls_of(def_id);
177 for &impl_def_id in impls.blanket_impls.iter() {
178 if let result @ Some(_) = f(impl_def_id) {
183 // Note that we're using `SimplifyParams::Yes` to query `non_blanket_impls` while using
184 // `SimplifyParams::No` while actually adding them.
186 // This way, when searching for some impl for `T: Trait`, we do not look at any impls
187 // whose outer level is not a parameter or projection. Especially for things like
188 // `T: Clone` this is incredibly useful as we would otherwise look at all the impls
189 // of `Clone` for `Option<T>`, `Vec<T>`, `ConcreteType` and so on.
190 if let Some(simp) = fast_reject::simplify_type(self, self_ty, SimplifyParams::Yes) {
191 if let Some(impls) = impls.non_blanket_impls.get(&simp) {
192 for &impl_def_id in impls {
193 if let result @ Some(_) = f(impl_def_id) {
199 for &impl_def_id in impls.non_blanket_impls.values().flatten() {
200 if let result @ Some(_) = f(impl_def_id) {
209 /// Returns an iterator containing all impls
210 pub fn all_impls(self, def_id: DefId) -> impl Iterator<Item = DefId> + 'tcx {
211 let TraitImpls { blanket_impls, non_blanket_impls } = self.trait_impls_of(def_id);
213 blanket_impls.iter().chain(non_blanket_impls.iter().flat_map(|(_, v)| v)).cloned()
217 // Query provider for `trait_impls_of`.
218 pub(super) fn trait_impls_of_provider(tcx: TyCtxt<'_>, trait_id: DefId) -> TraitImpls {
219 let mut impls = TraitImpls::default();
221 // Traits defined in the current crate can't have impls in upstream
222 // crates, so we don't bother querying the cstore.
223 if !trait_id.is_local() {
224 for &cnum in tcx.crates(()).iter() {
225 for &(impl_def_id, simplified_self_ty) in
226 tcx.implementations_of_trait((cnum, trait_id)).iter()
228 if let Some(simplified_self_ty) = simplified_self_ty {
231 .entry(simplified_self_ty)
235 impls.blanket_impls.push(impl_def_id);
241 for &impl_def_id in tcx.hir().trait_impls(trait_id) {
242 let impl_def_id = impl_def_id.to_def_id();
244 let impl_self_ty = tcx.type_of(impl_def_id);
245 if impl_self_ty.references_error() {
249 if let Some(simplified_self_ty) =
250 fast_reject::simplify_type(tcx, impl_self_ty, SimplifyParams::No)
252 impls.non_blanket_impls.entry(simplified_self_ty).or_default().push(impl_def_id);
254 impls.blanket_impls.push(impl_def_id);