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;
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 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
42 fn name(self) -> &'static str {
44 $( $variant => $name, )*
50 pub struct LanguageItems {
51 pub items: Vec<Option<DefId>>,
52 pub missing: Vec<LangItem>,
56 pub fn new() -> LanguageItems {
57 fn foo(_: LangItem) -> Option<DefId> { None }
60 items: vec![$(foo($variant)),*],
65 pub fn items(&self) -> &[Option<DefId>] {
69 pub fn require(&self, it: LangItem) -> Result<DefId, String> {
70 self.items[it as usize].ok_or_else(|| format!("requires `{}` lang_item", it.name()))
73 pub fn fn_trait_kind(&self, id: DefId) -> Option<ty::ClosureKind> {
75 x if x == self.fn_trait() => Some(ty::ClosureKind::Fn),
76 x if x == self.fn_mut_trait() => Some(ty::ClosureKind::FnMut),
77 x if x == self.fn_once_trait() => Some(ty::ClosureKind::FnOnce),
84 pub fn $method(&self) -> Option<DefId> {
85 self.items[$variant as usize]
90 struct LanguageItemCollector<'a, 'tcx: 'a> {
92 tcx: TyCtxt<'a, 'tcx, 'tcx>,
93 item_refs: FxHashMap<&'static str, (usize, Target)>,
96 impl<'a, 'v, 'tcx> ItemLikeVisitor<'v> for LanguageItemCollector<'a, 'tcx> {
97 fn visit_item(&mut self, item: &hir::Item) {
98 if let Some((value, span)) = extract(&item.attrs) {
99 let actual_target = Target::from_item(item);
100 match self.item_refs.get(&*value.as_str()).cloned() {
101 // Known lang item with attribute on correct target.
102 Some((item_index, expected_target)) if actual_target == expected_target => {
103 let def_id = self.tcx.hir().local_def_id_from_hir_id(item.hir_id);
104 self.collect_item(item_index, def_id);
106 // Known lang item with attribute on incorrect target.
107 Some((_, expected_target)) => {
108 let mut err = struct_span_err!(
109 self.tcx.sess, span, E0718,
110 "`{}` language item must be applied to a {}",
111 value, expected_target,
116 "attribute should be applied to a {}, not a {}",
117 expected_target, actual_target,
122 // Unknown lang item.
124 let mut err = struct_span_err!(
125 self.tcx.sess, span, E0522,
126 "definition of an unknown language item: `{}`",
131 format!("definition of unknown language item `{}`", value)
139 fn visit_trait_item(&mut self, _trait_item: &hir::TraitItem) {
140 // at present, lang items are always items, not trait items
143 fn visit_impl_item(&mut self, _impl_item: &hir::ImplItem) {
144 // at present, lang items are always items, not impl items
148 impl<'a, 'tcx> LanguageItemCollector<'a, 'tcx> {
149 fn new(tcx: TyCtxt<'a, 'tcx, 'tcx>) -> LanguageItemCollector<'a, 'tcx> {
150 let mut item_refs = FxHashMap::default();
152 $( item_refs.insert($name, ($variant as usize, $target)); )*
154 LanguageItemCollector {
156 items: LanguageItems::new(),
161 fn collect_item(&mut self, item_index: usize, item_def_id: DefId) {
162 // Check for duplicates.
163 if let Some(original_def_id) = self.items.items[item_index] {
164 if original_def_id != item_def_id {
165 let name = LangItem::from_u32(item_index as u32).unwrap().name();
166 let mut err = match self.tcx.hir().span_if_local(item_def_id) {
167 Some(span) => struct_span_err!(
171 "duplicate lang item found: `{}`.",
173 None => self.tcx.sess.struct_err(&format!(
174 "duplicate lang item in crate `{}`: `{}`.",
175 self.tcx.crate_name(item_def_id.krate),
178 if let Some(span) = self.tcx.hir().span_if_local(original_def_id) {
179 span_note!(&mut err, span, "first defined here.");
181 err.note(&format!("first defined in crate `{}`.",
182 self.tcx.crate_name(original_def_id.krate)));
189 self.items.items[item_index] = Some(item_def_id);
193 pub fn extract(attrs: &[ast::Attribute]) -> Option<(Symbol, Span)> {
194 for attribute in attrs {
195 if attribute.check_name("lang") {
196 if let Some(value) = attribute.value_str() {
197 return Some((value, attribute.span));
199 } else if attribute.check_name("panic_handler") {
200 return Some((Symbol::intern("panic_impl"), attribute.span))
201 } else if attribute.check_name("alloc_error_handler") {
202 return Some((Symbol::intern("oom"), attribute.span))
209 pub fn collect<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) -> LanguageItems {
210 let mut collector = LanguageItemCollector::new(tcx);
211 for &cnum in tcx.crates().iter() {
212 for &(def_id, item_index) in tcx.defined_lang_items(cnum).iter() {
213 collector.collect_item(item_index, def_id);
216 tcx.hir().krate().visit_all_item_likes(&mut collector);
217 let LanguageItemCollector { mut items, .. } = collector;
218 weak_lang_items::check_crate(tcx, &mut items);
226 language_item_table! {
227 // Variant name, Name, Method name, Target;
228 CharImplItem, "char", char_impl, Target::Impl;
229 StrImplItem, "str", str_impl, Target::Impl;
230 SliceImplItem, "slice", slice_impl, Target::Impl;
231 SliceU8ImplItem, "slice_u8", slice_u8_impl, Target::Impl;
232 StrAllocImplItem, "str_alloc", str_alloc_impl, Target::Impl;
233 SliceAllocImplItem, "slice_alloc", slice_alloc_impl, Target::Impl;
234 SliceU8AllocImplItem, "slice_u8_alloc", slice_u8_alloc_impl, Target::Impl;
235 ConstPtrImplItem, "const_ptr", const_ptr_impl, Target::Impl;
236 MutPtrImplItem, "mut_ptr", mut_ptr_impl, Target::Impl;
237 I8ImplItem, "i8", i8_impl, Target::Impl;
238 I16ImplItem, "i16", i16_impl, Target::Impl;
239 I32ImplItem, "i32", i32_impl, Target::Impl;
240 I64ImplItem, "i64", i64_impl, Target::Impl;
241 I128ImplItem, "i128", i128_impl, Target::Impl;
242 IsizeImplItem, "isize", isize_impl, Target::Impl;
243 U8ImplItem, "u8", u8_impl, Target::Impl;
244 U16ImplItem, "u16", u16_impl, Target::Impl;
245 U32ImplItem, "u32", u32_impl, Target::Impl;
246 U64ImplItem, "u64", u64_impl, Target::Impl;
247 U128ImplItem, "u128", u128_impl, Target::Impl;
248 UsizeImplItem, "usize", usize_impl, Target::Impl;
249 F32ImplItem, "f32", f32_impl, Target::Impl;
250 F64ImplItem, "f64", f64_impl, Target::Impl;
251 F32RuntimeImplItem, "f32_runtime", f32_runtime_impl, Target::Impl;
252 F64RuntimeImplItem, "f64_runtime", f64_runtime_impl, Target::Impl;
254 SizedTraitLangItem, "sized", sized_trait, Target::Trait;
255 UnsizeTraitLangItem, "unsize", unsize_trait, Target::Trait;
256 CopyTraitLangItem, "copy", copy_trait, Target::Trait;
257 CloneTraitLangItem, "clone", clone_trait, Target::Trait;
258 SyncTraitLangItem, "sync", sync_trait, Target::Trait;
259 FreezeTraitLangItem, "freeze", freeze_trait, Target::Trait;
261 DropTraitLangItem, "drop", drop_trait, Target::Trait;
263 CoerceUnsizedTraitLangItem, "coerce_unsized", coerce_unsized_trait, Target::Trait;
264 DispatchFromDynTraitLangItem,"dispatch_from_dyn", dispatch_from_dyn_trait, Target::Trait;
266 AddTraitLangItem, "add", add_trait, Target::Trait;
267 SubTraitLangItem, "sub", sub_trait, Target::Trait;
268 MulTraitLangItem, "mul", mul_trait, Target::Trait;
269 DivTraitLangItem, "div", div_trait, Target::Trait;
270 RemTraitLangItem, "rem", rem_trait, Target::Trait;
271 NegTraitLangItem, "neg", neg_trait, Target::Trait;
272 NotTraitLangItem, "not", not_trait, Target::Trait;
273 BitXorTraitLangItem, "bitxor", bitxor_trait, Target::Trait;
274 BitAndTraitLangItem, "bitand", bitand_trait, Target::Trait;
275 BitOrTraitLangItem, "bitor", bitor_trait, Target::Trait;
276 ShlTraitLangItem, "shl", shl_trait, Target::Trait;
277 ShrTraitLangItem, "shr", shr_trait, Target::Trait;
278 AddAssignTraitLangItem, "add_assign", add_assign_trait, Target::Trait;
279 SubAssignTraitLangItem, "sub_assign", sub_assign_trait, Target::Trait;
280 MulAssignTraitLangItem, "mul_assign", mul_assign_trait, Target::Trait;
281 DivAssignTraitLangItem, "div_assign", div_assign_trait, Target::Trait;
282 RemAssignTraitLangItem, "rem_assign", rem_assign_trait, Target::Trait;
283 BitXorAssignTraitLangItem, "bitxor_assign", bitxor_assign_trait, Target::Trait;
284 BitAndAssignTraitLangItem, "bitand_assign", bitand_assign_trait, Target::Trait;
285 BitOrAssignTraitLangItem, "bitor_assign", bitor_assign_trait, Target::Trait;
286 ShlAssignTraitLangItem, "shl_assign", shl_assign_trait, Target::Trait;
287 ShrAssignTraitLangItem, "shr_assign", shr_assign_trait, Target::Trait;
288 IndexTraitLangItem, "index", index_trait, Target::Trait;
289 IndexMutTraitLangItem, "index_mut", index_mut_trait, Target::Trait;
291 UnsafeCellTypeLangItem, "unsafe_cell", unsafe_cell_type, Target::Struct;
292 VaListTypeLangItem, "va_list", va_list, Target::Struct;
294 DerefTraitLangItem, "deref", deref_trait, Target::Trait;
295 DerefMutTraitLangItem, "deref_mut", deref_mut_trait, Target::Trait;
296 ReceiverTraitLangItem, "receiver", receiver_trait, Target::Trait;
298 FnTraitLangItem, "fn", fn_trait, Target::Trait;
299 FnMutTraitLangItem, "fn_mut", fn_mut_trait, Target::Trait;
300 FnOnceTraitLangItem, "fn_once", fn_once_trait, Target::Trait;
302 GeneratorStateLangItem, "generator_state", gen_state, Target::Enum;
303 GeneratorTraitLangItem, "generator", gen_trait, Target::Trait;
304 UnpinTraitLangItem, "unpin", unpin_trait, Target::Trait;
305 PinTypeLangItem, "pin", pin_type, Target::Struct;
307 EqTraitLangItem, "eq", eq_trait, Target::Trait;
308 PartialOrdTraitLangItem, "partial_ord", partial_ord_trait, Target::Trait;
309 OrdTraitLangItem, "ord", ord_trait, Target::Trait;
311 // A number of panic-related lang items. The `panic` item corresponds to
312 // divide-by-zero and various panic cases with `match`. The
313 // `panic_bounds_check` item is for indexing arrays.
315 // The `begin_unwind` lang item has a predefined symbol name and is sort of
316 // a "weak lang item" in the sense that a crate is not required to have it
317 // defined to use it, but a final product is required to define it
318 // somewhere. Additionally, there are restrictions on crates that use a weak
319 // lang item, but do not have it defined.
320 PanicFnLangItem, "panic", panic_fn, Target::Fn;
321 PanicBoundsCheckFnLangItem, "panic_bounds_check", panic_bounds_check_fn, Target::Fn;
322 PanicInfoLangItem, "panic_info", panic_info, Target::Struct;
323 PanicImplLangItem, "panic_impl", panic_impl, Target::Fn;
324 // Libstd panic entry point. Necessary for const eval to be able to catch it
325 BeginPanicFnLangItem, "begin_panic", begin_panic_fn, Target::Fn;
327 ExchangeMallocFnLangItem, "exchange_malloc", exchange_malloc_fn, Target::Fn;
328 BoxFreeFnLangItem, "box_free", box_free_fn, Target::Fn;
329 DropInPlaceFnLangItem, "drop_in_place", drop_in_place_fn, Target::Fn;
330 OomLangItem, "oom", oom, Target::Fn;
331 AllocLayoutLangItem, "alloc_layout", alloc_layout, Target::Struct;
333 StartFnLangItem, "start", start_fn, Target::Fn;
335 EhPersonalityLangItem, "eh_personality", eh_personality, Target::Fn;
336 EhUnwindResumeLangItem, "eh_unwind_resume", eh_unwind_resume, Target::Fn;
337 MSVCTryFilterLangItem, "msvc_try_filter", msvc_try_filter, Target::Static;
339 OwnedBoxLangItem, "owned_box", owned_box, Target::Struct;
341 PhantomDataItem, "phantom_data", phantom_data, Target::Struct;
343 ManuallyDropItem, "manually_drop", manually_drop, Target::Struct;
345 DebugTraitLangItem, "debug_trait", debug_trait, Target::Trait;
347 // A lang item for each of the 128-bit operators we can optionally lower.
348 I128AddFnLangItem, "i128_add", i128_add_fn, Target::Fn;
349 U128AddFnLangItem, "u128_add", u128_add_fn, Target::Fn;
350 I128SubFnLangItem, "i128_sub", i128_sub_fn, Target::Fn;
351 U128SubFnLangItem, "u128_sub", u128_sub_fn, Target::Fn;
352 I128MulFnLangItem, "i128_mul", i128_mul_fn, Target::Fn;
353 U128MulFnLangItem, "u128_mul", u128_mul_fn, Target::Fn;
354 I128DivFnLangItem, "i128_div", i128_div_fn, Target::Fn;
355 U128DivFnLangItem, "u128_div", u128_div_fn, Target::Fn;
356 I128RemFnLangItem, "i128_rem", i128_rem_fn, Target::Fn;
357 U128RemFnLangItem, "u128_rem", u128_rem_fn, Target::Fn;
358 I128ShlFnLangItem, "i128_shl", i128_shl_fn, Target::Fn;
359 U128ShlFnLangItem, "u128_shl", u128_shl_fn, Target::Fn;
360 I128ShrFnLangItem, "i128_shr", i128_shr_fn, Target::Fn;
361 U128ShrFnLangItem, "u128_shr", u128_shr_fn, Target::Fn;
362 // And overflow versions for the operators that are checkable.
363 // While MIR calls these Checked*, they return (T,bool), not Option<T>.
364 I128AddoFnLangItem, "i128_addo", i128_addo_fn, Target::Fn;
365 U128AddoFnLangItem, "u128_addo", u128_addo_fn, Target::Fn;
366 I128SuboFnLangItem, "i128_subo", i128_subo_fn, Target::Fn;
367 U128SuboFnLangItem, "u128_subo", u128_subo_fn, Target::Fn;
368 I128MuloFnLangItem, "i128_mulo", i128_mulo_fn, Target::Fn;
369 U128MuloFnLangItem, "u128_mulo", u128_mulo_fn, Target::Fn;
370 I128ShloFnLangItem, "i128_shlo", i128_shlo_fn, Target::Fn;
371 U128ShloFnLangItem, "u128_shlo", u128_shlo_fn, Target::Fn;
372 I128ShroFnLangItem, "i128_shro", i128_shro_fn, Target::Fn;
373 U128ShroFnLangItem, "u128_shro", u128_shro_fn, Target::Fn;
375 // Align offset for stride != 1, must not panic.
376 AlignOffsetLangItem, "align_offset", align_offset_fn, Target::Fn;
378 TerminationTraitLangItem, "termination", termination, Target::Trait;
380 Arc, "arc", arc, Target::Struct;
381 Rc, "rc", rc, Target::Struct;
384 impl<'a, 'tcx, 'gcx> TyCtxt<'a, 'tcx, 'gcx> {
385 pub fn require_lang_item(&self, lang_item: LangItem) -> DefId {
386 self.lang_items().require(lang_item).unwrap_or_else(|msg| {
387 self.sess.fatal(&msg)