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".
8 //! * Traits that represent operators; e.g., "Add", "Sub", "Index".
10 //! * Functions called by the compiler itself.
12 pub use self::LangItem::*;
14 use crate::hir::def_id::DefId;
15 use crate::hir::check_attr::Target;
16 use crate::ty::{self, TyCtxt};
17 use crate::middle::weak_lang_items;
18 use crate::util::nodemap::FxHashMap;
21 use syntax::symbol::{Symbol, sym};
23 use rustc_macros::HashStable;
24 use crate::hir::itemlikevisit::ItemLikeVisitor;
27 // The actual lang items defined come at the end of this file in one handy table.
28 // So you probably just want to nip down to the end.
29 macro_rules! language_item_table {
31 $( $variant:ident, $name:expr, $method:ident, $target:path; )*
35 /// A representation of all the valid language items in Rust.
36 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
43 /// Returns the `name` in `#[lang = "$name"]`.
44 /// For example, `LangItem::EqTraitLangItem`,
45 /// that is `#[lang = "eq"]` would result in `"eq"`.
46 fn name(self) -> &'static str {
48 $( $variant => $name, )*
54 pub struct LanguageItems {
55 /// Mappings from lang items to their possibly found `DefId`s.
56 /// The index corresponds to the order in `LangItem`.
57 pub items: Vec<Option<DefId>>,
58 /// Lang items that were not found during collection.
59 pub missing: Vec<LangItem>,
63 /// Construct an empty collection of lang items and no missing ones.
64 pub fn new() -> Self {
65 fn init_none(_: LangItem) -> Option<DefId> { None }
68 items: vec![$(init_none($variant)),*],
73 /// Returns the mappings to the possibly found `DefId`s for each lang item.
74 pub fn items(&self) -> &[Option<DefId>] {
78 /// Requires that a given `LangItem` was bound and returns the corresponding `DefId`.
79 /// If it wasn't bound, e.g. due to a missing `#[lang = "<it.name()>"]`,
80 /// returns an error message as a string.
81 pub fn require(&self, it: LangItem) -> Result<DefId, String> {
82 self.items[it as usize].ok_or_else(|| format!("requires `{}` lang_item", it.name()))
85 /// Returns the kind of closure that `id`, which is one of the `Fn*` traits, corresponds to.
86 /// If `id` is not one of the `Fn*` traits, `None` is returned.
87 pub fn fn_trait_kind(&self, id: DefId) -> Option<ty::ClosureKind> {
89 x if x == self.fn_trait() => Some(ty::ClosureKind::Fn),
90 x if x == self.fn_mut_trait() => Some(ty::ClosureKind::FnMut),
91 x if x == self.fn_once_trait() => Some(ty::ClosureKind::FnOnce),
97 /// Returns the corresponding `DefId` for the lang item
101 pub fn $method(&self) -> Option<DefId> {
102 self.items[$variant as usize]
107 struct LanguageItemCollector<'a, 'tcx: 'a> {
108 items: LanguageItems,
109 tcx: TyCtxt<'a, 'tcx, 'tcx>,
110 /// A mapping from the name of the lang item to its order and the form it must be of.
111 item_refs: FxHashMap<&'static str, (usize, Target)>,
114 impl<'a, 'v, 'tcx> ItemLikeVisitor<'v> for LanguageItemCollector<'a, 'tcx> {
115 fn visit_item(&mut self, item: &hir::Item) {
116 if let Some((value, span)) = extract(&item.attrs) {
117 let actual_target = Target::from_item(item);
118 match self.item_refs.get(&*value.as_str()).cloned() {
119 // Known lang item with attribute on correct target.
120 Some((item_index, expected_target)) if actual_target == expected_target => {
121 let def_id = self.tcx.hir().local_def_id_from_hir_id(item.hir_id);
122 self.collect_item(item_index, def_id);
124 // Known lang item with attribute on incorrect target.
125 Some((_, expected_target)) => {
127 self.tcx.sess, span, E0718,
128 "`{}` language item must be applied to a {}",
129 value, expected_target,
133 "attribute should be applied to a {}, not a {}",
134 expected_target, actual_target,
138 // Unknown lang item.
141 self.tcx.sess, span, E0522,
142 "definition of an unknown language item: `{}`",
146 format!("definition of unknown language item `{}`", value)
153 fn visit_trait_item(&mut self, _trait_item: &hir::TraitItem) {
154 // at present, lang items are always items, not trait items
157 fn visit_impl_item(&mut self, _impl_item: &hir::ImplItem) {
158 // at present, lang items are always items, not impl items
162 impl<'a, 'tcx> LanguageItemCollector<'a, 'tcx> {
163 fn new(tcx: TyCtxt<'a, 'tcx, 'tcx>) -> LanguageItemCollector<'a, 'tcx> {
164 let mut item_refs = FxHashMap::default();
166 $( item_refs.insert($name, ($variant as usize, $target)); )*
168 LanguageItemCollector {
170 items: LanguageItems::new(),
175 fn collect_item(&mut self, item_index: usize, item_def_id: DefId) {
176 // Check for duplicates.
177 if let Some(original_def_id) = self.items.items[item_index] {
178 if original_def_id != item_def_id {
179 let name = LangItem::from_u32(item_index as u32).unwrap().name();
180 let mut err = match self.tcx.hir().span_if_local(item_def_id) {
181 Some(span) => struct_span_err!(
185 "duplicate lang item found: `{}`.",
187 None => self.tcx.sess.struct_err(&format!(
188 "duplicate lang item in crate `{}`: `{}`.",
189 self.tcx.crate_name(item_def_id.krate),
192 if let Some(span) = self.tcx.hir().span_if_local(original_def_id) {
193 span_note!(&mut err, span, "first defined here.");
195 err.note(&format!("first defined in crate `{}`.",
196 self.tcx.crate_name(original_def_id.krate)));
203 self.items.items[item_index] = Some(item_def_id);
207 /// Extract the first `lang = "$name"` out of a list of attributes.
208 /// The attributes `#[panic_handler]` and `#[alloc_error_handler]`
209 /// are also extracted out when found.
210 pub fn extract(attrs: &[ast::Attribute]) -> Option<(Symbol, Span)> {
211 attrs.iter().find_map(|attr| Some(match attr {
212 _ if attr.check_name(sym::lang) => (attr.value_str()?, attr.span),
213 _ if attr.check_name(sym::panic_handler) => (sym::panic_impl, attr.span),
214 _ if attr.check_name(sym::alloc_error_handler) => (sym::oom, attr.span),
219 /// Traverse and collect all the lang items in all crates.
220 pub fn collect<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) -> LanguageItems {
221 // Initialize the collector.
222 let mut collector = LanguageItemCollector::new(tcx);
224 // Collect lang items in other crates.
225 for &cnum in tcx.crates().iter() {
226 for &(def_id, item_index) in tcx.defined_lang_items(cnum).iter() {
227 collector.collect_item(item_index, def_id);
231 // Collect lang items in this crate.
232 tcx.hir().krate().visit_all_item_likes(&mut collector);
234 // Extract out the found lang items.
235 let LanguageItemCollector { mut items, .. } = collector;
237 // Find all required but not-yet-defined lang items.
238 weak_lang_items::check_crate(tcx, &mut items);
247 language_item_table! {
248 // Variant name, Name, Method name, Target;
249 CharImplItem, "char", char_impl, Target::Impl;
250 StrImplItem, "str", str_impl, Target::Impl;
251 SliceImplItem, "slice", slice_impl, Target::Impl;
252 SliceU8ImplItem, "slice_u8", slice_u8_impl, Target::Impl;
253 StrAllocImplItem, "str_alloc", str_alloc_impl, Target::Impl;
254 SliceAllocImplItem, "slice_alloc", slice_alloc_impl, Target::Impl;
255 SliceU8AllocImplItem, "slice_u8_alloc", slice_u8_alloc_impl, Target::Impl;
256 ConstPtrImplItem, "const_ptr", const_ptr_impl, Target::Impl;
257 MutPtrImplItem, "mut_ptr", mut_ptr_impl, Target::Impl;
258 I8ImplItem, "i8", i8_impl, Target::Impl;
259 I16ImplItem, "i16", i16_impl, Target::Impl;
260 I32ImplItem, "i32", i32_impl, Target::Impl;
261 I64ImplItem, "i64", i64_impl, Target::Impl;
262 I128ImplItem, "i128", i128_impl, Target::Impl;
263 IsizeImplItem, "isize", isize_impl, Target::Impl;
264 U8ImplItem, "u8", u8_impl, Target::Impl;
265 U16ImplItem, "u16", u16_impl, Target::Impl;
266 U32ImplItem, "u32", u32_impl, Target::Impl;
267 U64ImplItem, "u64", u64_impl, Target::Impl;
268 U128ImplItem, "u128", u128_impl, Target::Impl;
269 UsizeImplItem, "usize", usize_impl, Target::Impl;
270 F32ImplItem, "f32", f32_impl, Target::Impl;
271 F64ImplItem, "f64", f64_impl, Target::Impl;
272 F32RuntimeImplItem, "f32_runtime", f32_runtime_impl, Target::Impl;
273 F64RuntimeImplItem, "f64_runtime", f64_runtime_impl, Target::Impl;
275 SizedTraitLangItem, "sized", sized_trait, Target::Trait;
276 UnsizeTraitLangItem, "unsize", unsize_trait, Target::Trait;
277 CopyTraitLangItem, "copy", copy_trait, Target::Trait;
278 CloneTraitLangItem, "clone", clone_trait, Target::Trait;
279 SyncTraitLangItem, "sync", sync_trait, Target::Trait;
280 FreezeTraitLangItem, "freeze", freeze_trait, Target::Trait;
282 DropTraitLangItem, "drop", drop_trait, Target::Trait;
284 CoerceUnsizedTraitLangItem, "coerce_unsized", coerce_unsized_trait, Target::Trait;
285 DispatchFromDynTraitLangItem,"dispatch_from_dyn", dispatch_from_dyn_trait, Target::Trait;
287 AddTraitLangItem, "add", add_trait, Target::Trait;
288 SubTraitLangItem, "sub", sub_trait, Target::Trait;
289 MulTraitLangItem, "mul", mul_trait, Target::Trait;
290 DivTraitLangItem, "div", div_trait, Target::Trait;
291 RemTraitLangItem, "rem", rem_trait, Target::Trait;
292 NegTraitLangItem, "neg", neg_trait, Target::Trait;
293 NotTraitLangItem, "not", not_trait, Target::Trait;
294 BitXorTraitLangItem, "bitxor", bitxor_trait, Target::Trait;
295 BitAndTraitLangItem, "bitand", bitand_trait, Target::Trait;
296 BitOrTraitLangItem, "bitor", bitor_trait, Target::Trait;
297 ShlTraitLangItem, "shl", shl_trait, Target::Trait;
298 ShrTraitLangItem, "shr", shr_trait, Target::Trait;
299 AddAssignTraitLangItem, "add_assign", add_assign_trait, Target::Trait;
300 SubAssignTraitLangItem, "sub_assign", sub_assign_trait, Target::Trait;
301 MulAssignTraitLangItem, "mul_assign", mul_assign_trait, Target::Trait;
302 DivAssignTraitLangItem, "div_assign", div_assign_trait, Target::Trait;
303 RemAssignTraitLangItem, "rem_assign", rem_assign_trait, Target::Trait;
304 BitXorAssignTraitLangItem, "bitxor_assign", bitxor_assign_trait, Target::Trait;
305 BitAndAssignTraitLangItem, "bitand_assign", bitand_assign_trait, Target::Trait;
306 BitOrAssignTraitLangItem, "bitor_assign", bitor_assign_trait, Target::Trait;
307 ShlAssignTraitLangItem, "shl_assign", shl_assign_trait, Target::Trait;
308 ShrAssignTraitLangItem, "shr_assign", shr_assign_trait, Target::Trait;
309 IndexTraitLangItem, "index", index_trait, Target::Trait;
310 IndexMutTraitLangItem, "index_mut", index_mut_trait, Target::Trait;
312 UnsafeCellTypeLangItem, "unsafe_cell", unsafe_cell_type, Target::Struct;
313 VaListTypeLangItem, "va_list", va_list, Target::Struct;
315 DerefTraitLangItem, "deref", deref_trait, Target::Trait;
316 DerefMutTraitLangItem, "deref_mut", deref_mut_trait, Target::Trait;
317 ReceiverTraitLangItem, "receiver", receiver_trait, Target::Trait;
319 FnTraitLangItem, "fn", fn_trait, Target::Trait;
320 FnMutTraitLangItem, "fn_mut", fn_mut_trait, Target::Trait;
321 FnOnceTraitLangItem, "fn_once", fn_once_trait, Target::Trait;
323 GeneratorStateLangItem, "generator_state", gen_state, Target::Enum;
324 GeneratorTraitLangItem, "generator", gen_trait, Target::Trait;
325 UnpinTraitLangItem, "unpin", unpin_trait, Target::Trait;
326 PinTypeLangItem, "pin", pin_type, Target::Struct;
328 EqTraitLangItem, "eq", eq_trait, Target::Trait;
329 PartialOrdTraitLangItem, "partial_ord", partial_ord_trait, Target::Trait;
330 OrdTraitLangItem, "ord", ord_trait, Target::Trait;
332 // A number of panic-related lang items. The `panic` item corresponds to
333 // divide-by-zero and various panic cases with `match`. The
334 // `panic_bounds_check` item is for indexing arrays.
336 // The `begin_unwind` lang item has a predefined symbol name and is sort of
337 // a "weak lang item" in the sense that a crate is not required to have it
338 // defined to use it, but a final product is required to define it
339 // somewhere. Additionally, there are restrictions on crates that use a weak
340 // lang item, but do not have it defined.
341 PanicFnLangItem, "panic", panic_fn, Target::Fn;
342 PanicBoundsCheckFnLangItem, "panic_bounds_check", panic_bounds_check_fn, Target::Fn;
343 PanicInfoLangItem, "panic_info", panic_info, Target::Struct;
344 PanicImplLangItem, "panic_impl", panic_impl, Target::Fn;
345 // Libstd panic entry point. Necessary for const eval to be able to catch it
346 BeginPanicFnLangItem, "begin_panic", begin_panic_fn, Target::Fn;
348 ExchangeMallocFnLangItem, "exchange_malloc", exchange_malloc_fn, Target::Fn;
349 BoxFreeFnLangItem, "box_free", box_free_fn, Target::Fn;
350 DropInPlaceFnLangItem, "drop_in_place", drop_in_place_fn, Target::Fn;
351 OomLangItem, "oom", oom, Target::Fn;
352 AllocLayoutLangItem, "alloc_layout", alloc_layout, Target::Struct;
354 StartFnLangItem, "start", start_fn, Target::Fn;
356 EhPersonalityLangItem, "eh_personality", eh_personality, Target::Fn;
357 EhUnwindResumeLangItem, "eh_unwind_resume", eh_unwind_resume, Target::Fn;
358 MSVCTryFilterLangItem, "msvc_try_filter", msvc_try_filter, Target::Static;
360 OwnedBoxLangItem, "owned_box", owned_box, Target::Struct;
362 PhantomDataItem, "phantom_data", phantom_data, Target::Struct;
364 ManuallyDropItem, "manually_drop", manually_drop, Target::Struct;
366 DebugTraitLangItem, "debug_trait", debug_trait, Target::Trait;
368 // A lang item for each of the 128-bit operators we can optionally lower.
369 I128AddFnLangItem, "i128_add", i128_add_fn, Target::Fn;
370 U128AddFnLangItem, "u128_add", u128_add_fn, Target::Fn;
371 I128SubFnLangItem, "i128_sub", i128_sub_fn, Target::Fn;
372 U128SubFnLangItem, "u128_sub", u128_sub_fn, Target::Fn;
373 I128MulFnLangItem, "i128_mul", i128_mul_fn, Target::Fn;
374 U128MulFnLangItem, "u128_mul", u128_mul_fn, Target::Fn;
375 I128DivFnLangItem, "i128_div", i128_div_fn, Target::Fn;
376 U128DivFnLangItem, "u128_div", u128_div_fn, Target::Fn;
377 I128RemFnLangItem, "i128_rem", i128_rem_fn, Target::Fn;
378 U128RemFnLangItem, "u128_rem", u128_rem_fn, Target::Fn;
379 I128ShlFnLangItem, "i128_shl", i128_shl_fn, Target::Fn;
380 U128ShlFnLangItem, "u128_shl", u128_shl_fn, Target::Fn;
381 I128ShrFnLangItem, "i128_shr", i128_shr_fn, Target::Fn;
382 U128ShrFnLangItem, "u128_shr", u128_shr_fn, Target::Fn;
383 // And overflow versions for the operators that are checkable.
384 // While MIR calls these Checked*, they return (T,bool), not Option<T>.
385 I128AddoFnLangItem, "i128_addo", i128_addo_fn, Target::Fn;
386 U128AddoFnLangItem, "u128_addo", u128_addo_fn, Target::Fn;
387 I128SuboFnLangItem, "i128_subo", i128_subo_fn, Target::Fn;
388 U128SuboFnLangItem, "u128_subo", u128_subo_fn, Target::Fn;
389 I128MuloFnLangItem, "i128_mulo", i128_mulo_fn, Target::Fn;
390 U128MuloFnLangItem, "u128_mulo", u128_mulo_fn, Target::Fn;
391 I128ShloFnLangItem, "i128_shlo", i128_shlo_fn, Target::Fn;
392 U128ShloFnLangItem, "u128_shlo", u128_shlo_fn, Target::Fn;
393 I128ShroFnLangItem, "i128_shro", i128_shro_fn, Target::Fn;
394 U128ShroFnLangItem, "u128_shro", u128_shro_fn, Target::Fn;
396 // Align offset for stride != 1, must not panic.
397 AlignOffsetLangItem, "align_offset", align_offset_fn, Target::Fn;
399 TerminationTraitLangItem, "termination", termination, Target::Trait;
401 Arc, "arc", arc, Target::Struct;
402 Rc, "rc", rc, Target::Struct;
405 impl<'a, 'tcx, 'gcx> TyCtxt<'a, 'tcx, 'gcx> {
406 /// Returns the `DefId` for a given `LangItem`.
407 /// If not found, fatally abort compilation.
408 pub fn require_lang_item(&self, lang_item: LangItem) -> DefId {
409 self.lang_items().require(lang_item).unwrap_or_else(|msg| {
410 self.sess.fatal(&msg)