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::errors::LangItemError;
12 use crate::{MethodKind, Target};
15 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
16 use rustc_macros::HashStable_Generic;
17 use rustc_span::symbol::{kw, sym, Symbol};
20 /// All of the language items, defined or not.
21 /// Defined lang items can come from the current crate or its dependencies.
22 #[derive(HashStable_Generic, Debug)]
23 pub struct LanguageItems {
24 /// Mappings from lang items to their possibly found [`DefId`]s.
25 /// The index corresponds to the order in [`LangItem`].
26 items: [Option<DefId>; std::mem::variant_count::<LangItem>()],
27 /// Lang items that were not found during collection.
28 pub missing: Vec<LangItem>,
32 /// Construct an empty collection of lang items and no missing ones.
33 pub fn new() -> Self {
34 Self { items: [None; std::mem::variant_count::<LangItem>()], missing: Vec::new() }
37 pub fn get(&self, item: LangItem) -> Option<DefId> {
38 self.items[item as usize]
41 pub fn set(&mut self, item: LangItem, def_id: DefId) {
42 self.items[item as usize] = Some(def_id);
45 /// Requires that a given `LangItem` was bound and returns the corresponding `DefId`.
46 /// If it wasn't bound, e.g. due to a missing `#[lang = "<it.name()>"]`,
47 /// returns an error encapsulating the `LangItem`.
48 pub fn require(&self, it: LangItem) -> Result<DefId, LangItemError> {
49 self.get(it).ok_or_else(|| LangItemError(it))
52 pub fn iter<'a>(&'a self) -> impl Iterator<Item = (LangItem, DefId)> + 'a {
56 .filter_map(|(i, id)| id.map(|id| (LangItem::from_u32(i as u32).unwrap(), id)))
60 // The actual lang items defined come at the end of this file in one handy table.
61 // So you probably just want to nip down to the end.
62 macro_rules! language_item_table {
64 $( $(#[$attr:meta])* $variant:ident, $module:ident :: $name:ident, $method:ident, $target:expr, $generics:expr; )*
68 /// A representation of all the valid language items in Rust.
69 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, Encodable, Decodable)]
72 #[doc = concat!("The `", stringify!($name), "` lang item.")]
81 /// Returns the `name` symbol in `#[lang = "$name"]`.
82 /// For example, [`LangItem::PartialEq`]`.name()`
83 /// would result in [`sym::eq`] since it is `#[lang = "eq"]`.
84 pub fn name(self) -> Symbol {
86 $( LangItem::$variant => $module::$name, )*
90 /// Opposite of [`LangItem::name`]
91 pub fn from_name(name: Symbol) -> Option<Self> {
93 $( $module::$name => Some(LangItem::$variant), )*
98 pub fn target(self) -> Target {
100 $( LangItem::$variant => $target, )*
104 pub fn required_generics(&self) -> GenericRequirement {
106 $( LangItem::$variant => $generics, )*
113 #[doc = concat!("Returns the [`DefId`] of the `", stringify!($name), "` lang item if it is defined.")]
114 pub fn $method(&self) -> Option<DefId> {
115 self.items[LangItem::$variant as usize]
122 impl<CTX> HashStable<CTX> for LangItem {
123 fn hash_stable(&self, _: &mut CTX, hasher: &mut StableHasher) {
124 ::std::hash::Hash::hash(self, hasher);
128 /// Extracts the first `lang = "$name"` out of a list of attributes.
129 /// The attributes `#[panic_handler]` and `#[alloc_error_handler]`
130 /// are also extracted out when found.
131 pub fn extract(attrs: &[ast::Attribute]) -> Option<(Symbol, Span)> {
132 attrs.iter().find_map(|attr| {
134 _ if attr.has_name(sym::lang) => (attr.value_str()?, attr.span),
135 _ if attr.has_name(sym::panic_handler) => (sym::panic_impl, attr.span),
136 _ if attr.has_name(sym::alloc_error_handler) => (sym::oom, attr.span),
142 language_item_table! {
143 // Variant name, Name, Method name, Target Generic requirements;
144 Sized, sym::sized, sized_trait, Target::Trait, GenericRequirement::Exact(0);
145 Unsize, sym::unsize, unsize_trait, Target::Trait, GenericRequirement::Minimum(1);
146 /// Trait injected by `#[derive(PartialEq)]`, (i.e. "Partial EQ").
147 StructuralPeq, sym::structural_peq, structural_peq_trait, Target::Trait, GenericRequirement::None;
148 /// Trait injected by `#[derive(Eq)]`, (i.e. "Total EQ"; no, I will not apologize).
149 StructuralTeq, sym::structural_teq, structural_teq_trait, Target::Trait, GenericRequirement::None;
150 Copy, sym::copy, copy_trait, Target::Trait, GenericRequirement::Exact(0);
151 Clone, sym::clone, clone_trait, Target::Trait, GenericRequirement::None;
152 Sync, sym::sync, sync_trait, Target::Trait, GenericRequirement::Exact(0);
153 DiscriminantKind, sym::discriminant_kind, discriminant_kind_trait, Target::Trait, GenericRequirement::None;
154 /// The associated item of the [`DiscriminantKind`] trait.
155 Discriminant, sym::discriminant_type, discriminant_type, Target::AssocTy, GenericRequirement::None;
157 PointeeTrait, sym::pointee_trait, pointee_trait, Target::Trait, GenericRequirement::None;
158 Metadata, sym::metadata_type, metadata_type, Target::AssocTy, GenericRequirement::None;
159 DynMetadata, sym::dyn_metadata, dyn_metadata, Target::Struct, GenericRequirement::None;
161 Freeze, sym::freeze, freeze_trait, Target::Trait, GenericRequirement::Exact(0);
163 Drop, sym::drop, drop_trait, Target::Trait, GenericRequirement::None;
164 Destruct, sym::destruct, destruct_trait, Target::Trait, GenericRequirement::None;
166 CoerceUnsized, sym::coerce_unsized, coerce_unsized_trait, Target::Trait, GenericRequirement::Minimum(1);
167 DispatchFromDyn, sym::dispatch_from_dyn, dispatch_from_dyn_trait, Target::Trait, GenericRequirement::Minimum(1);
169 // language items relating to transmutability
170 TransmuteOpts, sym::transmute_opts, transmute_opts, Target::Struct, GenericRequirement::Exact(0);
171 TransmuteTrait, sym::transmute_trait, transmute_trait, Target::Trait, GenericRequirement::Exact(3);
173 Add, sym::add, add_trait, Target::Trait, GenericRequirement::Exact(1);
174 Sub, sym::sub, sub_trait, Target::Trait, GenericRequirement::Exact(1);
175 Mul, sym::mul, mul_trait, Target::Trait, GenericRequirement::Exact(1);
176 Div, sym::div, div_trait, Target::Trait, GenericRequirement::Exact(1);
177 Rem, sym::rem, rem_trait, Target::Trait, GenericRequirement::Exact(1);
178 Neg, sym::neg, neg_trait, Target::Trait, GenericRequirement::Exact(0);
179 Not, sym::not, not_trait, Target::Trait, GenericRequirement::Exact(0);
180 BitXor, sym::bitxor, bitxor_trait, Target::Trait, GenericRequirement::Exact(1);
181 BitAnd, sym::bitand, bitand_trait, Target::Trait, GenericRequirement::Exact(1);
182 BitOr, sym::bitor, bitor_trait, Target::Trait, GenericRequirement::Exact(1);
183 Shl, sym::shl, shl_trait, Target::Trait, GenericRequirement::Exact(1);
184 Shr, sym::shr, shr_trait, Target::Trait, GenericRequirement::Exact(1);
185 AddAssign, sym::add_assign, add_assign_trait, Target::Trait, GenericRequirement::Exact(1);
186 SubAssign, sym::sub_assign, sub_assign_trait, Target::Trait, GenericRequirement::Exact(1);
187 MulAssign, sym::mul_assign, mul_assign_trait, Target::Trait, GenericRequirement::Exact(1);
188 DivAssign, sym::div_assign, div_assign_trait, Target::Trait, GenericRequirement::Exact(1);
189 RemAssign, sym::rem_assign, rem_assign_trait, Target::Trait, GenericRequirement::Exact(1);
190 BitXorAssign, sym::bitxor_assign, bitxor_assign_trait, Target::Trait, GenericRequirement::Exact(1);
191 BitAndAssign, sym::bitand_assign, bitand_assign_trait, Target::Trait, GenericRequirement::Exact(1);
192 BitOrAssign, sym::bitor_assign, bitor_assign_trait, Target::Trait, GenericRequirement::Exact(1);
193 ShlAssign, sym::shl_assign, shl_assign_trait, Target::Trait, GenericRequirement::Exact(1);
194 ShrAssign, sym::shr_assign, shr_assign_trait, Target::Trait, GenericRequirement::Exact(1);
195 Index, sym::index, index_trait, Target::Trait, GenericRequirement::Exact(1);
196 IndexMut, sym::index_mut, index_mut_trait, Target::Trait, GenericRequirement::Exact(1);
198 UnsafeCell, sym::unsafe_cell, unsafe_cell_type, Target::Struct, GenericRequirement::None;
199 VaList, sym::va_list, va_list, Target::Struct, GenericRequirement::None;
201 Deref, sym::deref, deref_trait, Target::Trait, GenericRequirement::Exact(0);
202 DerefMut, sym::deref_mut, deref_mut_trait, Target::Trait, GenericRequirement::Exact(0);
203 DerefTarget, sym::deref_target, deref_target, Target::AssocTy, GenericRequirement::None;
204 Receiver, sym::receiver, receiver_trait, Target::Trait, GenericRequirement::None;
206 Fn, kw::Fn, fn_trait, Target::Trait, GenericRequirement::Exact(1);
207 FnMut, sym::fn_mut, fn_mut_trait, Target::Trait, GenericRequirement::Exact(1);
208 FnOnce, sym::fn_once, fn_once_trait, Target::Trait, GenericRequirement::Exact(1);
210 FnOnceOutput, sym::fn_once_output, fn_once_output, Target::AssocTy, GenericRequirement::None;
212 Future, sym::future_trait, future_trait, Target::Trait, GenericRequirement::Exact(0);
213 GeneratorState, sym::generator_state, gen_state, Target::Enum, GenericRequirement::None;
214 Generator, sym::generator, gen_trait, Target::Trait, GenericRequirement::Minimum(1);
215 Unpin, sym::unpin, unpin_trait, Target::Trait, GenericRequirement::None;
216 Pin, sym::pin, pin_type, Target::Struct, GenericRequirement::None;
218 PartialEq, sym::eq, eq_trait, Target::Trait, GenericRequirement::Exact(1);
219 PartialOrd, sym::partial_ord, partial_ord_trait, Target::Trait, GenericRequirement::Exact(1);
221 // A number of panic-related lang items. The `panic` item corresponds to divide-by-zero and
222 // various panic cases with `match`. The `panic_bounds_check` item is for indexing arrays.
224 // The `begin_unwind` lang item has a predefined symbol name and is sort of a "weak lang item"
225 // in the sense that a crate is not required to have it defined to use it, but a final product
226 // is required to define it somewhere. Additionally, there are restrictions on crates that use
227 // a weak lang item, but do not have it defined.
228 Panic, sym::panic, panic_fn, Target::Fn, GenericRequirement::Exact(0);
229 PanicFmt, sym::panic_fmt, panic_fmt, Target::Fn, GenericRequirement::None;
230 PanicDisplay, sym::panic_display, panic_display, Target::Fn, GenericRequirement::None;
231 ConstPanicFmt, sym::const_panic_fmt, const_panic_fmt, Target::Fn, GenericRequirement::None;
232 PanicBoundsCheck, sym::panic_bounds_check, panic_bounds_check_fn, Target::Fn, GenericRequirement::Exact(0);
233 PanicInfo, sym::panic_info, panic_info, Target::Struct, GenericRequirement::None;
234 PanicLocation, sym::panic_location, panic_location, Target::Struct, GenericRequirement::None;
235 PanicImpl, sym::panic_impl, panic_impl, Target::Fn, GenericRequirement::None;
236 PanicNoUnwind, sym::panic_no_unwind, panic_no_unwind, Target::Fn, GenericRequirement::Exact(0);
237 /// libstd panic entry point. Necessary for const eval to be able to catch it
238 BeginPanic, sym::begin_panic, begin_panic_fn, Target::Fn, GenericRequirement::None;
240 ExchangeMalloc, sym::exchange_malloc, exchange_malloc_fn, Target::Fn, GenericRequirement::None;
241 BoxFree, sym::box_free, box_free_fn, Target::Fn, GenericRequirement::Minimum(1);
242 DropInPlace, sym::drop_in_place, drop_in_place_fn, Target::Fn, GenericRequirement::Minimum(1);
243 Oom, sym::oom, oom, Target::Fn, GenericRequirement::None;
244 AllocLayout, sym::alloc_layout, alloc_layout, Target::Struct, GenericRequirement::None;
246 Start, sym::start, start_fn, Target::Fn, GenericRequirement::Exact(1);
248 EhPersonality, sym::eh_personality, eh_personality, Target::Fn, GenericRequirement::None;
249 EhCatchTypeinfo, sym::eh_catch_typeinfo, eh_catch_typeinfo, Target::Static, GenericRequirement::None;
251 OwnedBox, sym::owned_box, owned_box, Target::Struct, GenericRequirement::Minimum(1);
253 PhantomData, sym::phantom_data, phantom_data, Target::Struct, GenericRequirement::Exact(1);
255 ManuallyDrop, sym::manually_drop, manually_drop, Target::Struct, GenericRequirement::None;
257 MaybeUninit, sym::maybe_uninit, maybe_uninit, Target::Union, GenericRequirement::None;
259 /// Align offset for stride != 1; must not panic.
260 AlignOffset, sym::align_offset, align_offset_fn, Target::Fn, GenericRequirement::None;
262 Termination, sym::termination, termination, Target::Trait, GenericRequirement::None;
264 Try, sym::Try, try_trait, Target::Trait, GenericRequirement::None;
266 Tuple, sym::tuple_trait, tuple_trait, Target::Trait, GenericRequirement::Exact(0);
268 SliceLen, sym::slice_len_fn, slice_len_fn, Target::Method(MethodKind::Inherent), GenericRequirement::None;
270 // Language items from AST lowering
271 TryTraitFromResidual, sym::from_residual, from_residual_fn, Target::Method(MethodKind::Trait { body: false }), GenericRequirement::None;
272 TryTraitFromOutput, sym::from_output, from_output_fn, Target::Method(MethodKind::Trait { body: false }), GenericRequirement::None;
273 TryTraitBranch, sym::branch, branch_fn, Target::Method(MethodKind::Trait { body: false }), GenericRequirement::None;
274 TryTraitFromYeet, sym::from_yeet, from_yeet_fn, Target::Fn, GenericRequirement::None;
276 PollReady, sym::Ready, poll_ready_variant, Target::Variant, GenericRequirement::None;
277 PollPending, sym::Pending, poll_pending_variant, Target::Variant, GenericRequirement::None;
279 FromGenerator, sym::from_generator, from_generator_fn, Target::Fn, GenericRequirement::None;
280 GetContext, sym::get_context, get_context_fn, Target::Fn, GenericRequirement::None;
282 FuturePoll, sym::poll, future_poll_fn, Target::Method(MethodKind::Trait { body: false }), GenericRequirement::None;
284 FromFrom, sym::from, from_fn, Target::Method(MethodKind::Trait { body: false }), GenericRequirement::None;
286 OptionSome, sym::Some, option_some_variant, Target::Variant, GenericRequirement::None;
287 OptionNone, sym::None, option_none_variant, Target::Variant, GenericRequirement::None;
289 ResultOk, sym::Ok, result_ok_variant, Target::Variant, GenericRequirement::None;
290 ResultErr, sym::Err, result_err_variant, Target::Variant, GenericRequirement::None;
292 ControlFlowContinue, sym::Continue, cf_continue_variant, Target::Variant, GenericRequirement::None;
293 ControlFlowBreak, sym::Break, cf_break_variant, Target::Variant, GenericRequirement::None;
295 IntoFutureIntoFuture, sym::into_future, into_future_fn, Target::Method(MethodKind::Trait { body: false }), GenericRequirement::None;
296 IntoIterIntoIter, sym::into_iter, into_iter_fn, Target::Method(MethodKind::Trait { body: false }), GenericRequirement::None;
297 IteratorNext, sym::next, next_fn, Target::Method(MethodKind::Trait { body: false}), GenericRequirement::None;
299 PinNewUnchecked, sym::new_unchecked, new_unchecked_fn, Target::Method(MethodKind::Inherent), GenericRequirement::None;
301 RangeFrom, sym::RangeFrom, range_from_struct, Target::Struct, GenericRequirement::None;
302 RangeFull, sym::RangeFull, range_full_struct, Target::Struct, GenericRequirement::None;
303 RangeInclusiveStruct, sym::RangeInclusive, range_inclusive_struct, Target::Struct, GenericRequirement::None;
304 RangeInclusiveNew, sym::range_inclusive_new, range_inclusive_new_method, Target::Method(MethodKind::Inherent), GenericRequirement::None;
305 Range, sym::Range, range_struct, Target::Struct, GenericRequirement::None;
306 RangeToInclusive, sym::RangeToInclusive, range_to_inclusive_struct, Target::Struct, GenericRequirement::None;
307 RangeTo, sym::RangeTo, range_to_struct, Target::Struct, GenericRequirement::None;
310 pub enum GenericRequirement {
316 pub static FN_TRAITS: &'static [LangItem] = &[LangItem::Fn, LangItem::FnMut, LangItem::FnOnce];
318 pub static OPERATORS: &'static [LangItem] = &[
336 LangItem::BitXorAssign,
337 LangItem::BitAndAssign,
338 LangItem::BitOrAssign,
344 LangItem::PartialOrd,