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 use crate::def_id::DefId;
11 use crate::{MethodKind, Target};
14 use rustc_data_structures::fx::FxHashMap;
15 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
16 use rustc_macros::HashStable_Generic;
17 use rustc_span::symbol::{kw, sym, Symbol};
20 use std::lazy::SyncLazy;
22 pub enum LangItemGroup {
26 const NUM_GROUPS: usize = 1;
28 macro_rules! expand_group {
37 // The actual lang items defined come at the end of this file in one handy table.
38 // So you probably just want to nip down to the end.
39 macro_rules! language_item_table {
41 $( $variant:ident $($group:expr)?, $name:expr, $method:ident, $target:expr; )*
45 /// A representation of all the valid language items in Rust.
46 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, Encodable, Decodable)]
53 /// Returns the `name` symbol in `#[lang = "$name"]`.
54 /// For example, `LangItem::EqTraitLangItem`,
55 /// that is `#[lang = "eq"]` would result in `sym::eq`.
56 pub fn name(self) -> Symbol {
58 $( LangItem::$variant => $name, )*
62 pub fn group(self) -> Option<LangItemGroup> {
65 $( LangItem::$variant => expand_group!($($group)*), )*
70 #[derive(HashStable_Generic, Debug)]
71 pub struct LanguageItems {
72 /// Mappings from lang items to their possibly found `DefId`s.
73 /// The index corresponds to the order in `LangItem`.
74 pub items: Vec<Option<DefId>>,
75 /// Lang items that were not found during collection.
76 pub missing: Vec<LangItem>,
77 /// Mapping from `LangItemGroup` discriminants to all
78 /// `DefId`s of lang items in that group.
79 pub groups: [Vec<DefId>; NUM_GROUPS],
83 /// Construct an empty collection of lang items and no missing ones.
84 pub fn new() -> Self {
85 fn init_none(_: LangItem) -> Option<DefId> { None }
88 items: vec![$(init_none(LangItem::$variant)),*],
90 groups: [vec![]; NUM_GROUPS],
94 /// Returns the mappings to the possibly found `DefId`s for each lang item.
95 pub fn items(&self) -> &[Option<DefId>] {
99 /// Requires that a given `LangItem` was bound and returns the corresponding `DefId`.
100 /// If it wasn't bound, e.g. due to a missing `#[lang = "<it.name()>"]`,
101 /// returns an error message as a string.
102 pub fn require(&self, it: LangItem) -> Result<DefId, String> {
103 self.items[it as usize].ok_or_else(|| format!("requires `{}` lang_item", it.name()))
106 pub fn group(&self, group: LangItemGroup) -> &[DefId] {
107 self.groups[group as usize].as_ref()
111 /// Returns the corresponding `DefId` for the lang item if it
114 pub fn $method(&self) -> Option<DefId> {
115 self.items[LangItem::$variant as usize]
120 /// A mapping from the name of the lang item to its order and the form it must be of.
121 pub static ITEM_REFS: SyncLazy<FxHashMap<Symbol, (usize, Target)>> = SyncLazy::new(|| {
122 let mut item_refs = FxHashMap::default();
123 $( item_refs.insert($name, (LangItem::$variant as usize, $target)); )*
131 impl<CTX> HashStable<CTX> for LangItem {
132 fn hash_stable(&self, _: &mut CTX, hasher: &mut StableHasher) {
133 ::std::hash::Hash::hash(self, hasher);
137 /// Extracts the first `lang = "$name"` out of a list of attributes.
138 /// The attributes `#[panic_handler]` and `#[alloc_error_handler]`
139 /// are also extracted out when found.
141 /// About the `check_name` argument: passing in a `Session` would be simpler,
142 /// because then we could call `Session::check_name` directly. But we want to
143 /// avoid the need for `librustc_hir` to depend on `librustc_session`, so we
144 /// use a closure instead.
145 pub fn extract<'a, F>(check_name: F, attrs: &'a [ast::Attribute]) -> Option<(Symbol, Span)>
147 F: Fn(&'a ast::Attribute, Symbol) -> bool,
149 attrs.iter().find_map(|attr| {
151 _ if check_name(attr, sym::lang) => (attr.value_str()?, attr.span),
152 _ if check_name(attr, sym::panic_handler) => (sym::panic_impl, attr.span),
153 _ if check_name(attr, sym::alloc_error_handler) => (sym::oom, attr.span),
159 language_item_table! {
160 // Variant name, Name, Method name, Target;
161 Bool, sym::bool, bool_impl, Target::Impl;
162 Char, sym::char, char_impl, Target::Impl;
163 Str, sym::str, str_impl, Target::Impl;
164 Array, sym::array, array_impl, Target::Impl;
165 Slice, sym::slice, slice_impl, Target::Impl;
166 SliceU8, sym::slice_u8, slice_u8_impl, Target::Impl;
167 StrAlloc, sym::str_alloc, str_alloc_impl, Target::Impl;
168 SliceAlloc, sym::slice_alloc, slice_alloc_impl, Target::Impl;
169 SliceU8Alloc, sym::slice_u8_alloc, slice_u8_alloc_impl, Target::Impl;
170 ConstPtr, sym::const_ptr, const_ptr_impl, Target::Impl;
171 MutPtr, sym::mut_ptr, mut_ptr_impl, Target::Impl;
172 ConstSlicePtr, sym::const_slice_ptr, const_slice_ptr_impl, Target::Impl;
173 MutSlicePtr, sym::mut_slice_ptr, mut_slice_ptr_impl, Target::Impl;
174 I8, sym::i8, i8_impl, Target::Impl;
175 I16, sym::i16, i16_impl, Target::Impl;
176 I32, sym::i32, i32_impl, Target::Impl;
177 I64, sym::i64, i64_impl, Target::Impl;
178 I128, sym::i128, i128_impl, Target::Impl;
179 Isize, sym::isize, isize_impl, Target::Impl;
180 U8, sym::u8, u8_impl, Target::Impl;
181 U16, sym::u16, u16_impl, Target::Impl;
182 U32, sym::u32, u32_impl, Target::Impl;
183 U64, sym::u64, u64_impl, Target::Impl;
184 U128, sym::u128, u128_impl, Target::Impl;
185 Usize, sym::usize, usize_impl, Target::Impl;
186 F32, sym::f32, f32_impl, Target::Impl;
187 F64, sym::f64, f64_impl, Target::Impl;
188 F32Runtime, sym::f32_runtime, f32_runtime_impl, Target::Impl;
189 F64Runtime, sym::f64_runtime, f64_runtime_impl, Target::Impl;
191 Sized, sym::sized, sized_trait, Target::Trait;
192 Unsize, sym::unsize, unsize_trait, Target::Trait;
193 // Trait injected by #[derive(PartialEq)], (i.e. "Partial EQ").
194 StructuralPeq, sym::structural_peq, structural_peq_trait, Target::Trait;
195 // Trait injected by #[derive(Eq)], (i.e. "Total EQ"; no, I will not apologize).
196 StructuralTeq, sym::structural_teq, structural_teq_trait, Target::Trait;
197 Copy, sym::copy, copy_trait, Target::Trait;
198 Clone, sym::clone, clone_trait, Target::Trait;
199 Sync, sym::sync, sync_trait, Target::Trait;
200 DiscriminantKind, sym::discriminant_kind, discriminant_kind_trait, Target::Trait;
201 // The associated item of `trait DiscriminantKind`.
202 Discriminant, sym::discriminant_type, discriminant_type, Target::AssocTy;
204 PointeeTrait, sym::pointee_trait, pointee_trait, Target::Trait;
205 Metadata, sym::metadata_type, metadata_type, Target::AssocTy;
206 DynMetadata, sym::dyn_metadata, dyn_metadata, Target::Struct;
208 Freeze, sym::freeze, freeze_trait, Target::Trait;
210 Drop, sym::drop, drop_trait, Target::Trait;
212 CoerceUnsized, sym::coerce_unsized, coerce_unsized_trait, Target::Trait;
213 DispatchFromDyn, sym::dispatch_from_dyn, dispatch_from_dyn_trait, Target::Trait;
215 Add(Op), sym::add, add_trait, Target::Trait;
216 Sub(Op), sym::sub, sub_trait, Target::Trait;
217 Mul(Op), sym::mul, mul_trait, Target::Trait;
218 Div(Op), sym::div, div_trait, Target::Trait;
219 Rem(Op), sym::rem, rem_trait, Target::Trait;
220 Neg(Op), sym::neg, neg_trait, Target::Trait;
221 Not(Op), sym::not, not_trait, Target::Trait;
222 BitXor(Op), sym::bitxor, bitxor_trait, Target::Trait;
223 BitAnd(Op), sym::bitand, bitand_trait, Target::Trait;
224 BitOr(Op), sym::bitor, bitor_trait, Target::Trait;
225 Shl(Op), sym::shl, shl_trait, Target::Trait;
226 Shr(Op), sym::shr, shr_trait, Target::Trait;
227 AddAssign(Op), sym::add_assign, add_assign_trait, Target::Trait;
228 SubAssign(Op), sym::sub_assign, sub_assign_trait, Target::Trait;
229 MulAssign(Op), sym::mul_assign, mul_assign_trait, Target::Trait;
230 DivAssign(Op), sym::div_assign, div_assign_trait, Target::Trait;
231 RemAssign(Op), sym::rem_assign, rem_assign_trait, Target::Trait;
232 BitXorAssign(Op), sym::bitxor_assign, bitxor_assign_trait, Target::Trait;
233 BitAndAssign(Op), sym::bitand_assign, bitand_assign_trait, Target::Trait;
234 BitOrAssign(Op), sym::bitor_assign, bitor_assign_trait, Target::Trait;
235 ShlAssign(Op), sym::shl_assign, shl_assign_trait, Target::Trait;
236 ShrAssign(Op), sym::shr_assign, shr_assign_trait, Target::Trait;
237 Index(Op), sym::index, index_trait, Target::Trait;
238 IndexMut(Op), sym::index_mut, index_mut_trait, Target::Trait;
240 UnsafeCell, sym::unsafe_cell, unsafe_cell_type, Target::Struct;
241 VaList, sym::va_list, va_list, Target::Struct;
243 Deref, sym::deref, deref_trait, Target::Trait;
244 DerefMut, sym::deref_mut, deref_mut_trait, Target::Trait;
245 Receiver, sym::receiver, receiver_trait, Target::Trait;
247 Fn, kw::Fn, fn_trait, Target::Trait;
248 FnMut, sym::fn_mut, fn_mut_trait, Target::Trait;
249 FnOnce, sym::fn_once, fn_once_trait, Target::Trait;
251 FnOnceOutput, sym::fn_once_output, fn_once_output, Target::AssocTy;
253 Future, sym::future_trait, future_trait, Target::Trait;
254 GeneratorState, sym::generator_state, gen_state, Target::Enum;
255 Generator, sym::generator, gen_trait, Target::Trait;
256 Unpin, sym::unpin, unpin_trait, Target::Trait;
257 Pin, sym::pin, pin_type, Target::Struct;
259 PartialEq, sym::eq, eq_trait, Target::Trait;
260 PartialOrd, sym::partial_ord, partial_ord_trait, Target::Trait;
262 // A number of panic-related lang items. The `panic` item corresponds to divide-by-zero and
263 // various panic cases with `match`. The `panic_bounds_check` item is for indexing arrays.
265 // The `begin_unwind` lang item has a predefined symbol name and is sort of a "weak lang item"
266 // in the sense that a crate is not required to have it defined to use it, but a final product
267 // is required to define it somewhere. Additionally, there are restrictions on crates that use
268 // a weak lang item, but do not have it defined.
269 Panic, sym::panic, panic_fn, Target::Fn;
270 PanicStr, sym::panic_str, panic_str, Target::Fn;
271 PanicBoundsCheck, sym::panic_bounds_check, panic_bounds_check_fn, Target::Fn;
272 PanicInfo, sym::panic_info, panic_info, Target::Struct;
273 PanicLocation, sym::panic_location, panic_location, Target::Struct;
274 PanicImpl, sym::panic_impl, panic_impl, Target::Fn;
275 // libstd panic entry point. Necessary for const eval to be able to catch it
276 BeginPanic, sym::begin_panic, begin_panic_fn, Target::Fn;
278 ExchangeMalloc, sym::exchange_malloc, exchange_malloc_fn, Target::Fn;
279 BoxFree, sym::box_free, box_free_fn, Target::Fn;
280 DropInPlace, sym::drop_in_place, drop_in_place_fn, Target::Fn;
281 Oom, sym::oom, oom, Target::Fn;
282 AllocLayout, sym::alloc_layout, alloc_layout, Target::Struct;
284 Start, sym::start, start_fn, Target::Fn;
286 EhPersonality, sym::eh_personality, eh_personality, Target::Fn;
287 EhCatchTypeinfo, sym::eh_catch_typeinfo, eh_catch_typeinfo, Target::Static;
289 OwnedBox, sym::owned_box, owned_box, Target::Struct;
291 PhantomData, sym::phantom_data, phantom_data, Target::Struct;
293 ManuallyDrop, sym::manually_drop, manually_drop, Target::Struct;
295 MaybeUninit, sym::maybe_uninit, maybe_uninit, Target::Union;
297 // Align offset for stride != 1; must not panic.
298 AlignOffset, sym::align_offset, align_offset_fn, Target::Fn;
300 Termination, sym::termination, termination, Target::Trait;
302 Try, kw::Try, try_trait, Target::Trait;
304 // Language items from AST lowering
305 TryFromError, sym::from_error, from_error_fn, Target::Method(MethodKind::Trait { body: false });
306 TryFromOk, sym::from_ok, from_ok_fn, Target::Method(MethodKind::Trait { body: false });
307 TryIntoResult, sym::into_result, into_result_fn, Target::Method(MethodKind::Trait { body: false });
309 PollReady, sym::Ready, poll_ready_variant, Target::Variant;
310 PollPending, sym::Pending, poll_pending_variant, Target::Variant;
312 FromGenerator, sym::from_generator, from_generator_fn, Target::Fn;
313 GetContext, sym::get_context, get_context_fn, Target::Fn;
315 FuturePoll, sym::poll, future_poll_fn, Target::Method(MethodKind::Trait { body: false });
317 FromFrom, sym::from, from_fn, Target::Method(MethodKind::Trait { body: false });
319 OptionSome, sym::Some, option_some_variant, Target::Variant;
320 OptionNone, sym::None, option_none_variant, Target::Variant;
322 ResultOk, sym::Ok, result_ok_variant, Target::Variant;
323 ResultErr, sym::Err, result_err_variant, Target::Variant;
325 IntoIterIntoIter, sym::into_iter, into_iter_fn, Target::Method(MethodKind::Trait { body: false });
326 IteratorNext, sym::next, next_fn, Target::Method(MethodKind::Trait { body: false});
328 PinNewUnchecked, sym::new_unchecked, new_unchecked_fn, Target::Method(MethodKind::Inherent);
330 RangeFrom, sym::RangeFrom, range_from_struct, Target::Struct;
331 RangeFull, sym::RangeFull, range_full_struct, Target::Struct;
332 RangeInclusiveStruct, sym::RangeInclusive, range_inclusive_struct, Target::Struct;
333 RangeInclusiveNew, sym::range_inclusive_new, range_inclusive_new_method, Target::Method(MethodKind::Inherent);
334 Range, sym::Range, range_struct, Target::Struct;
335 RangeToInclusive, sym::RangeToInclusive, range_to_inclusive_struct, Target::Struct;
336 RangeTo, sym::RangeTo, range_to_struct, Target::Struct;