1 use crate::ich::{self, StableHashingContext};
2 use crate::ty::fast_reject::SimplifiedType;
3 use crate::ty::{self, TyCtxt};
4 use rustc_ast::ast::Ident;
5 use rustc_data_structures::fx::FxHashMap;
6 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
7 use rustc_hir::def_id::{DefId, DefIdMap};
9 /// A per-trait graph of impls in specialization order. At the moment, this
10 /// graph forms a tree rooted with the trait itself, with all other nodes
11 /// representing impls, and parent-child relationships representing
14 /// The graph provides two key services:
16 /// - Construction. This implicitly checks for overlapping impls (i.e., impls
17 /// that overlap but where neither specializes the other -- an artifact of the
18 /// simple "chain" rule.
20 /// - Parent extraction. In particular, the graph can give you the *immediate*
21 /// parents of a given specializing impl, which is needed for extracting
22 /// default items amongst other things. In the simple "chain" rule, every impl
23 /// has at most one parent.
24 #[derive(RustcEncodable, RustcDecodable, HashStable)]
26 // All impls have a parent; the "root" impls have as their parent the `def_id`
28 pub parent: DefIdMap<DefId>,
30 // The "root" impls are found by looking up the trait's def_id.
31 pub children: DefIdMap<Children>,
35 pub fn new() -> Graph {
36 Graph { parent: Default::default(), children: Default::default() }
39 /// The parent of a given impl, which is the `DefId` of the trait when the
40 /// impl is a "specialization root".
41 pub fn parent(&self, child: DefId) -> DefId {
42 *self.parent.get(&child).unwrap_or_else(|| panic!("Failed to get parent for {:?}", child))
46 /// Children of a given impl, grouped into blanket/non-blanket varieties as is
47 /// done in `TraitDef`.
48 #[derive(Default, RustcEncodable, RustcDecodable)]
50 // Impls of a trait (or specializations of a given impl). To allow for
51 // quicker lookup, the impls are indexed by a simplified version of their
52 // `Self` type: impls with a simplifiable `Self` are stored in
53 // `nonblanket_impls` keyed by it, while all other impls are stored in
56 // A similar division is used within `TraitDef`, but the lists there collect
57 // together *all* the impls for a trait, and are populated prior to building
58 // the specialization graph.
59 /// Impls of the trait.
60 pub nonblanket_impls: FxHashMap<SimplifiedType, Vec<DefId>>,
62 /// Blanket impls associated with the trait.
63 pub blanket_impls: Vec<DefId>,
66 /// A node in the specialization graph is either an impl or a trait
67 /// definition; either can serve as a source of item definitions.
68 /// There is always exactly one trait definition node: the root.
69 #[derive(Debug, Copy, Clone)]
76 pub fn is_from_trait(&self) -> bool {
78 Node::Trait(..) => true,
83 /// Iterate over the items defined directly by the given (impl or trait) node.
84 pub fn items(&self, tcx: TyCtxt<'tcx>) -> impl 'tcx + Iterator<Item = &'tcx ty::AssocItem> {
85 tcx.associated_items(self.def_id()).in_definition_order()
88 /// Finds an associated item defined in this node.
90 /// If this returns `None`, the item can potentially still be found in
91 /// parents of this node.
95 trait_item_name: Ident,
96 trait_item_kind: ty::AssocKind,
98 ) -> Option<ty::AssocItem> {
99 use crate::ty::AssocKind::*;
101 tcx.associated_items(self.def_id())
102 .filter_by_name_unhygienic(trait_item_name.name)
103 .find(move |impl_item| {
104 match (trait_item_kind, impl_item.kind) {
108 | (Type, OpaqueTy) // assoc. types can be made opaque in impls
109 => tcx.hygienic_eq(impl_item.ident, trait_item_name, trait_def_id),
121 pub fn def_id(&self) -> DefId {
123 Node::Impl(did) => did,
124 Node::Trait(did) => did,
129 #[derive(Copy, Clone)]
130 pub struct Ancestors<'tcx> {
132 specialization_graph: &'tcx Graph,
133 current_source: Option<Node>,
136 impl Iterator for Ancestors<'_> {
138 fn next(&mut self) -> Option<Node> {
139 let cur = self.current_source.take();
140 if let Some(Node::Impl(cur_impl)) = cur {
141 let parent = self.specialization_graph.parent(cur_impl);
143 self.current_source = if parent == self.trait_def_id {
144 Some(Node::Trait(parent))
146 Some(Node::Impl(parent))
153 pub struct NodeItem<T> {
158 impl<T> NodeItem<T> {
159 pub fn map<U, F: FnOnce(T) -> U>(self, f: F) -> NodeItem<U> {
160 NodeItem { node: self.node, item: f(self.item) }
164 impl<'tcx> Ancestors<'tcx> {
165 /// Finds the bottom-most (ie. most specialized) definition of an associated
170 trait_item_name: Ident,
171 trait_item_kind: ty::AssocKind,
172 ) -> Option<NodeItem<ty::AssocItem>> {
173 let trait_def_id = self.trait_def_id;
174 self.find_map(|node| {
175 node.item(tcx, trait_item_name, trait_item_kind, trait_def_id)
176 .map(|item| NodeItem { node, item })
181 /// Walk up the specialization ancestors of a given impl, starting with that
186 start_from_impl: DefId,
187 ) -> Ancestors<'tcx> {
188 let specialization_graph = tcx.specialization_graph_of(trait_def_id);
191 specialization_graph,
192 current_source: Some(Node::Impl(start_from_impl)),
196 impl<'a> HashStable<StableHashingContext<'a>> for Children {
197 fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
198 let Children { ref nonblanket_impls, ref blanket_impls } = *self;
200 ich::hash_stable_trait_impls(hcx, hasher, blanket_impls, nonblanket_impls);