1 //! Defines 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 pub use self::LangItem::*;
12 use crate::def_id::DefId;
16 use rustc_data_structures::fx::FxHashMap;
17 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
18 use rustc_macros::HashStable_Generic;
19 use rustc_span::symbol::{kw, sym, Symbol};
22 use lazy_static::lazy_static;
24 pub enum LangItemGroup {
28 const NUM_GROUPS: usize = 1;
30 macro_rules! expand_group {
39 // The actual lang items defined come at the end of this file in one handy table.
40 // So you probably just want to nip down to the end.
41 macro_rules! language_item_table {
43 $( $variant:ident $($group:expr)?, $name:expr, $method:ident, $target:expr; )*
47 /// A representation of all the valid language items in Rust.
48 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
55 /// Returns the `name` symbol in `#[lang = "$name"]`.
56 /// For example, `LangItem::EqTraitLangItem`,
57 /// that is `#[lang = "eq"]` would result in `sym::eq`.
58 pub fn name(self) -> Symbol {
60 $( $variant => $name, )*
64 pub fn group(self) -> Option<LangItemGroup> {
67 $( $variant => expand_group!($($group)*), )*
72 #[derive(HashStable_Generic)]
73 pub struct LanguageItems {
74 /// Mappings from lang items to their possibly found `DefId`s.
75 /// The index corresponds to the order in `LangItem`.
76 pub items: Vec<Option<DefId>>,
77 /// Lang items that were not found during collection.
78 pub missing: Vec<LangItem>,
79 /// Mapping from `LangItemGroup` discriminants to all
80 /// `DefId`s of lang items in that group.
81 pub groups: [Vec<DefId>; NUM_GROUPS],
85 /// Construct an empty collection of lang items and no missing ones.
86 pub fn new() -> Self {
87 fn init_none(_: LangItem) -> Option<DefId> { None }
90 items: vec![$(init_none($variant)),*],
92 groups: [vec![]; NUM_GROUPS],
96 /// Returns the mappings to the possibly found `DefId`s for each lang item.
97 pub fn items(&self) -> &[Option<DefId>] {
101 /// Requires that a given `LangItem` was bound and returns the corresponding `DefId`.
102 /// If it wasn't bound, e.g. due to a missing `#[lang = "<it.name()>"]`,
103 /// returns an error message as a string.
104 pub fn require(&self, it: LangItem) -> Result<DefId, String> {
105 self.items[it as usize].ok_or_else(|| format!("requires `{}` lang_item", it.name()))
108 pub fn group(&self, group: LangItemGroup) -> &[DefId] {
109 self.groups[group as usize].as_ref()
113 /// Returns the corresponding `DefId` for the lang item if it
116 pub fn $method(&self) -> Option<DefId> {
117 self.items[$variant as usize]
123 /// A mapping from the name of the lang item to its order and the form it must be of.
124 pub static ref ITEM_REFS: FxHashMap<Symbol, (usize, Target)> = {
125 let mut item_refs = FxHashMap::default();
126 $( item_refs.insert($name, ($variant as usize, $target)); )*
135 impl<CTX> HashStable<CTX> for LangItem {
136 fn hash_stable(&self, _: &mut CTX, hasher: &mut StableHasher) {
137 ::std::hash::Hash::hash(self, hasher);
141 /// Extracts the first `lang = "$name"` out of a list of attributes.
142 /// The attributes `#[panic_handler]` and `#[alloc_error_handler]`
143 /// are also extracted out when found.
145 /// About the `check_name` argument: passing in a `Session` would be simpler,
146 /// because then we could call `Session::check_name` directly. But we want to
147 /// avoid the need for `librustc_hir` to depend on `librustc_session`, so we
148 /// use a closure instead.
149 pub fn extract<'a, F>(check_name: F, attrs: &'a [ast::Attribute]) -> Option<(Symbol, Span)>
151 F: Fn(&'a ast::Attribute, Symbol) -> bool,
153 attrs.iter().find_map(|attr| {
155 _ if check_name(attr, sym::lang) => (attr.value_str()?, attr.span),
156 _ if check_name(attr, sym::panic_handler) => (sym::panic_impl, attr.span),
157 _ if check_name(attr, sym::alloc_error_handler) => (sym::oom, attr.span),
163 language_item_table! {
164 // Variant name, Name, Method name, Target;
165 BoolImplItem, sym::bool, bool_impl, Target::Impl;
166 CharImplItem, sym::char, char_impl, Target::Impl;
167 StrImplItem, sym::str, str_impl, Target::Impl;
168 SliceImplItem, sym::slice, slice_impl, Target::Impl;
169 SliceU8ImplItem, sym::slice_u8, slice_u8_impl, Target::Impl;
170 StrAllocImplItem, sym::str_alloc, str_alloc_impl, Target::Impl;
171 SliceAllocImplItem, sym::slice_alloc, slice_alloc_impl, Target::Impl;
172 SliceU8AllocImplItem, sym::slice_u8_alloc, slice_u8_alloc_impl, Target::Impl;
173 ConstPtrImplItem, sym::const_ptr, const_ptr_impl, Target::Impl;
174 MutPtrImplItem, sym::mut_ptr, mut_ptr_impl, Target::Impl;
175 ConstSlicePtrImplItem, sym::const_slice_ptr, const_slice_ptr_impl, Target::Impl;
176 MutSlicePtrImplItem, sym::mut_slice_ptr, mut_slice_ptr_impl, Target::Impl;
177 I8ImplItem, sym::i8, i8_impl, Target::Impl;
178 I16ImplItem, sym::i16, i16_impl, Target::Impl;
179 I32ImplItem, sym::i32, i32_impl, Target::Impl;
180 I64ImplItem, sym::i64, i64_impl, Target::Impl;
181 I128ImplItem, sym::i128, i128_impl, Target::Impl;
182 IsizeImplItem, sym::isize, isize_impl, Target::Impl;
183 U8ImplItem, sym::u8, u8_impl, Target::Impl;
184 U16ImplItem, sym::u16, u16_impl, Target::Impl;
185 U32ImplItem, sym::u32, u32_impl, Target::Impl;
186 U64ImplItem, sym::u64, u64_impl, Target::Impl;
187 U128ImplItem, sym::u128, u128_impl, Target::Impl;
188 UsizeImplItem, sym::usize, usize_impl, Target::Impl;
189 F32ImplItem, sym::f32, f32_impl, Target::Impl;
190 F64ImplItem, sym::f64, f64_impl, Target::Impl;
191 F32RuntimeImplItem, sym::f32_runtime, f32_runtime_impl, Target::Impl;
192 F64RuntimeImplItem, sym::f64_runtime, f64_runtime_impl, Target::Impl;
194 SizedTraitLangItem, sym::sized, sized_trait, Target::Trait;
195 UnsizeTraitLangItem, sym::unsize, unsize_trait, Target::Trait;
196 // trait injected by #[derive(PartialEq)], (i.e. "Partial EQ").
197 StructuralPeqTraitLangItem, sym::structural_peq, structural_peq_trait, Target::Trait;
198 // trait injected by #[derive(Eq)], (i.e. "Total EQ"; no, I will not apologize).
199 StructuralTeqTraitLangItem, sym::structural_teq, structural_teq_trait, Target::Trait;
200 CopyTraitLangItem, sym::copy, copy_trait, Target::Trait;
201 CloneTraitLangItem, sym::clone, clone_trait, Target::Trait;
202 SyncTraitLangItem, sym::sync, sync_trait, Target::Trait;
203 DiscriminantKindTraitLangItem, sym::discriminant_kind, discriminant_kind_trait, Target::Trait;
204 // The associated item of `trait DiscriminantKind`.
205 DiscriminantTypeLangItem, sym::discriminant_type, discriminant_type, Target::AssocTy;
207 FreezeTraitLangItem, sym::freeze, freeze_trait, Target::Trait;
209 DropTraitLangItem, sym::drop, drop_trait, Target::Trait;
211 CoerceUnsizedTraitLangItem, sym::coerce_unsized, coerce_unsized_trait, Target::Trait;
212 DispatchFromDynTraitLangItem, sym::dispatch_from_dyn, dispatch_from_dyn_trait, Target::Trait;
214 AddTraitLangItem(Op), sym::add, add_trait, Target::Trait;
215 SubTraitLangItem(Op), sym::sub, sub_trait, Target::Trait;
216 MulTraitLangItem(Op), sym::mul, mul_trait, Target::Trait;
217 DivTraitLangItem(Op), sym::div, div_trait, Target::Trait;
218 RemTraitLangItem(Op), sym::rem, rem_trait, Target::Trait;
219 NegTraitLangItem(Op), sym::neg, neg_trait, Target::Trait;
220 NotTraitLangItem(Op), sym::not, not_trait, Target::Trait;
221 BitXorTraitLangItem(Op), sym::bitxor, bitxor_trait, Target::Trait;
222 BitAndTraitLangItem(Op), sym::bitand, bitand_trait, Target::Trait;
223 BitOrTraitLangItem(Op), sym::bitor, bitor_trait, Target::Trait;
224 ShlTraitLangItem(Op), sym::shl, shl_trait, Target::Trait;
225 ShrTraitLangItem(Op), sym::shr, shr_trait, Target::Trait;
226 AddAssignTraitLangItem(Op), sym::add_assign, add_assign_trait, Target::Trait;
227 SubAssignTraitLangItem(Op), sym::sub_assign, sub_assign_trait, Target::Trait;
228 MulAssignTraitLangItem(Op), sym::mul_assign, mul_assign_trait, Target::Trait;
229 DivAssignTraitLangItem(Op), sym::div_assign, div_assign_trait, Target::Trait;
230 RemAssignTraitLangItem(Op), sym::rem_assign, rem_assign_trait, Target::Trait;
231 BitXorAssignTraitLangItem(Op), sym::bitxor_assign, bitxor_assign_trait, Target::Trait;
232 BitAndAssignTraitLangItem(Op), sym::bitand_assign, bitand_assign_trait, Target::Trait;
233 BitOrAssignTraitLangItem(Op), sym::bitor_assign, bitor_assign_trait, Target::Trait;
234 ShlAssignTraitLangItem(Op), sym::shl_assign, shl_assign_trait, Target::Trait;
235 ShrAssignTraitLangItem(Op), sym::shr_assign, shr_assign_trait, Target::Trait;
236 IndexTraitLangItem(Op), sym::index, index_trait, Target::Trait;
237 IndexMutTraitLangItem(Op), sym::index_mut, index_mut_trait, Target::Trait;
239 UnsafeCellTypeLangItem, sym::unsafe_cell, unsafe_cell_type, Target::Struct;
240 VaListTypeLangItem, sym::va_list, va_list, Target::Struct;
242 DerefTraitLangItem, sym::deref, deref_trait, Target::Trait;
243 DerefMutTraitLangItem, sym::deref_mut, deref_mut_trait, Target::Trait;
244 ReceiverTraitLangItem, sym::receiver, receiver_trait, Target::Trait;
246 FnTraitLangItem, kw::Fn, fn_trait, Target::Trait;
247 FnMutTraitLangItem, sym::fn_mut, fn_mut_trait, Target::Trait;
248 FnOnceTraitLangItem, sym::fn_once, fn_once_trait, Target::Trait;
250 FnOnceOutputLangItem, sym::fn_once_output, fn_once_output, Target::AssocTy;
252 FutureTraitLangItem, sym::future_trait, future_trait, Target::Trait;
253 GeneratorStateLangItem, sym::generator_state, gen_state, Target::Enum;
254 GeneratorTraitLangItem, sym::generator, gen_trait, Target::Trait;
255 UnpinTraitLangItem, sym::unpin, unpin_trait, Target::Trait;
256 PinTypeLangItem, sym::pin, pin_type, Target::Struct;
258 // Don't be fooled by the naming here: this lang item denotes `PartialEq`, not `Eq`.
259 EqTraitLangItem, sym::eq, eq_trait, Target::Trait;
260 PartialOrdTraitLangItem, sym::partial_ord, partial_ord_trait, Target::Trait;
262 // A number of panic-related lang items. The `panic` item corresponds to
263 // divide-by-zero and various panic cases with `match`. The
264 // `panic_bounds_check` item is for indexing arrays.
266 // The `begin_unwind` lang item has a predefined symbol name and is sort of
267 // a "weak lang item" in the sense that a crate is not required to have it
268 // defined to use it, but a final product is required to define it
269 // somewhere. Additionally, there are restrictions on crates that use a weak
270 // lang item, but do not have it defined.
271 PanicFnLangItem, sym::panic, panic_fn, Target::Fn;
272 PanicBoundsCheckFnLangItem, sym::panic_bounds_check, panic_bounds_check_fn, Target::Fn;
273 PanicInfoLangItem, sym::panic_info, panic_info, Target::Struct;
274 PanicLocationLangItem, sym::panic_location, panic_location, Target::Struct;
275 PanicImplLangItem, sym::panic_impl, panic_impl, Target::Fn;
276 // Libstd panic entry point. Necessary for const eval to be able to catch it
277 BeginPanicFnLangItem, sym::begin_panic, begin_panic_fn, Target::Fn;
279 ExchangeMallocFnLangItem, sym::exchange_malloc, exchange_malloc_fn, Target::Fn;
280 BoxFreeFnLangItem, sym::box_free, box_free_fn, Target::Fn;
281 DropInPlaceFnLangItem, sym::drop_in_place, drop_in_place_fn, Target::Fn;
282 OomLangItem, sym::oom, oom, Target::Fn;
283 AllocLayoutLangItem, sym::alloc_layout, alloc_layout, Target::Struct;
285 StartFnLangItem, sym::start, start_fn, Target::Fn;
287 EhPersonalityLangItem, sym::eh_personality, eh_personality, Target::Fn;
288 EhCatchTypeinfoLangItem, sym::eh_catch_typeinfo, eh_catch_typeinfo, Target::Static;
290 OwnedBoxLangItem, sym::owned_box, owned_box, Target::Struct;
292 PhantomDataItem, sym::phantom_data, phantom_data, Target::Struct;
294 ManuallyDropItem, sym::manually_drop, manually_drop, Target::Struct;
296 MaybeUninitLangItem, sym::maybe_uninit, maybe_uninit, Target::Union;
298 // Align offset for stride != 1; must not panic.
299 AlignOffsetLangItem, sym::align_offset, align_offset_fn, Target::Fn;
301 TerminationTraitLangItem, sym::termination, termination, Target::Trait;
303 TryTraitLangItem, kw::Try, try_trait, Target::Trait;
305 // language items related to source code coverage instrumentation (-Zinstrument-coverage)
306 CountCodeRegionFnLangItem, sym::count_code_region, count_code_region_fn, Target::Fn;
307 CoverageCounterAddFnLangItem, sym::coverage_counter_add, coverage_counter_add_fn, Target::Fn;
308 CoverageCounterSubtractFnLangItem, sym::coverage_counter_subtract, coverage_counter_subtract_fn, Target::Fn;