1 //! Detecting language items.
3 //! Language items are items that represent concepts intrinsic to the language
4 //! itself. Examples are:
6 //! * Traits that specify "kinds"; e.g., `Sync`, `Send`.
7 //! * Traits that represent operators; e.g., `Add`, `Sub`, `Index`.
8 //! * Functions called by the compiler itself.
10 use crate::check_attr::target_from_impl_item;
12 DuplicateLangItem, IncorrectTarget, LangItemOnIncorrectTarget, UnknownLangItem,
14 use crate::weak_lang_items;
17 use rustc_hir::def::DefKind;
18 use rustc_hir::def_id::DefId;
19 use rustc_hir::lang_items::{extract, GenericRequirement, ITEM_REFS};
20 use rustc_hir::{HirId, LangItem, LanguageItems, Target};
21 use rustc_middle::ty::TyCtxt;
22 use rustc_session::cstore::ExternCrate;
23 use rustc_span::{symbol::kw::Empty, Span};
25 use rustc_middle::ty::query::Providers;
27 pub(crate) enum Duplicate {
33 struct LanguageItemCollector<'tcx> {
38 impl<'tcx> LanguageItemCollector<'tcx> {
39 fn new(tcx: TyCtxt<'tcx>) -> LanguageItemCollector<'tcx> {
40 LanguageItemCollector { tcx, items: LanguageItems::new() }
43 fn check_for_lang(&mut self, actual_target: Target, hir_id: HirId) {
44 let attrs = self.tcx.hir().attrs(hir_id);
45 if let Some((name, span)) = extract(&attrs) {
46 match ITEM_REFS.get(&name).cloned() {
47 // Known lang item with attribute on correct target.
48 Some((item_index, expected_target)) if actual_target == expected_target => {
49 self.collect_item_extended(item_index, hir_id, span);
51 // Known lang item with attribute on incorrect target.
52 Some((_, expected_target)) => {
53 self.tcx.sess.emit_err(LangItemOnIncorrectTarget {
62 self.tcx.sess.emit_err(UnknownLangItem { span, name });
68 fn collect_item(&mut self, item_index: usize, item_def_id: DefId) {
69 // Check for duplicates.
70 if let Some(original_def_id) = self.items.items[item_index] {
71 if original_def_id != item_def_id {
72 let local_span = self.tcx.hir().span_if_local(item_def_id);
73 let lang_item_name = LangItem::from_u32(item_index as u32).unwrap().name();
74 let crate_name = self.tcx.crate_name(item_def_id.krate);
75 let mut dependency_of = Empty;
76 let is_local = item_def_id.is_local();
77 let path = if is_local {
81 .crate_extern_paths(item_def_id.krate)
83 .map(|p| p.display().to_string())
88 let first_defined_span = self.tcx.hir().span_if_local(original_def_id);
89 let mut orig_crate_name = Empty;
90 let mut orig_dependency_of = Empty;
91 let orig_is_local = original_def_id.is_local();
92 let orig_path = if orig_is_local {
96 .crate_extern_paths(original_def_id.krate)
98 .map(|p| p.display().to_string())
103 if first_defined_span.is_none() {
104 orig_crate_name = self.tcx.crate_name(original_def_id.krate);
105 if let Some(ExternCrate { dependency_of: inner_dependency_of, .. }) =
106 self.tcx.extern_crate(original_def_id)
108 orig_dependency_of = self.tcx.crate_name(*inner_dependency_of);
112 let duplicate = if local_span.is_some() {
115 match self.tcx.extern_crate(item_def_id) {
116 Some(ExternCrate { dependency_of: inner_dependency_of, .. }) => {
117 dependency_of = self.tcx.crate_name(*inner_dependency_of);
118 Duplicate::CrateDepends
120 _ => Duplicate::Crate,
124 self.tcx.sess.emit_err(DuplicateLangItem {
142 self.items.items[item_index] = Some(item_def_id);
143 if let Some(group) = LangItem::from_u32(item_index as u32).unwrap().group() {
144 self.items.groups[group as usize].push(item_def_id);
148 // Like collect_item() above, but also checks whether the lang item is declared
149 // with the right number of generic arguments.
150 fn collect_item_extended(&mut self, item_index: usize, hir_id: HirId, span: Span) {
151 let item_def_id = self.tcx.hir().local_def_id(hir_id).to_def_id();
152 let lang_item = LangItem::from_u32(item_index as u32).unwrap();
153 let name = lang_item.name();
155 // Now check whether the lang_item has the expected number of generic
156 // arguments. Generally speaking, binary and indexing operations have
157 // one (for the RHS/index), unary operations have none, the closure
158 // traits have one for the argument list, generators have one for the
159 // resume argument, and ordering/equality relations have one for the RHS
160 // Some other types like Box and various functions like drop_in_place
161 // have minimum requirements.
163 if let hir::Node::Item(hir::Item { kind, span: item_span, .. }) = self.tcx.hir().get(hir_id)
165 let (actual_num, generics_span) = match kind.generics() {
166 Some(generics) => (generics.params.len(), generics.span),
167 None => (0, *item_span),
170 let mut at_least = false;
171 let required = match lang_item.required_generics() {
172 GenericRequirement::Exact(num) if num != actual_num => Some(num),
173 GenericRequirement::Minimum(num) if actual_num < num => {
177 // If the number matches, or there is no requirement, handle it normally
181 if let Some(num) = required {
182 // We are issuing E0718 "incorrect target" here, because while the
183 // item kind of the target is correct, the target is still wrong
184 // because of the wrong number of generic arguments.
185 self.tcx.sess.emit_err(IncorrectTarget {
195 // return early to not collect the lang item
200 self.collect_item(item_index, item_def_id);
204 /// Traverses and collects all the lang items in all crates.
205 fn get_lang_items(tcx: TyCtxt<'_>, (): ()) -> LanguageItems {
206 // Initialize the collector.
207 let mut collector = LanguageItemCollector::new(tcx);
209 // Collect lang items in other crates.
210 for &cnum in tcx.crates(()).iter() {
211 for &(def_id, item_index) in tcx.defined_lang_items(cnum).iter() {
212 collector.collect_item(item_index, def_id);
216 // Collect lang items in this crate.
217 let crate_items = tcx.hir_crate_items(());
219 for id in crate_items.items() {
220 collector.check_for_lang(Target::from_def_kind(tcx.def_kind(id.owner_id)), id.hir_id());
222 if matches!(tcx.def_kind(id.owner_id), DefKind::Enum) {
223 let item = tcx.hir().item(id);
224 if let hir::ItemKind::Enum(def, ..) = &item.kind {
225 for variant in def.variants {
226 collector.check_for_lang(Target::Variant, variant.id);
232 // FIXME: avoid calling trait_item() when possible
233 for id in crate_items.trait_items() {
234 let item = tcx.hir().trait_item(id);
235 collector.check_for_lang(Target::from_trait_item(item), item.hir_id())
238 // FIXME: avoid calling impl_item() when possible
239 for id in crate_items.impl_items() {
240 let item = tcx.hir().impl_item(id);
241 collector.check_for_lang(target_from_impl_item(tcx, item), item.hir_id())
244 // Extract out the found lang items.
245 let LanguageItemCollector { mut items, .. } = collector;
247 // Find all required but not-yet-defined lang items.
248 weak_lang_items::check_crate(tcx, &mut items);
253 pub fn provide(providers: &mut Providers) {
254 providers.get_lang_items = get_lang_items;