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 `#[panic_handler]` attribute is also extracted out when found.
130 pub fn extract(attrs: &[ast::Attribute]) -> Option<(Symbol, Span)> {
131 attrs.iter().find_map(|attr| {
133 _ if attr.has_name(sym::lang) => (attr.value_str()?, attr.span),
134 _ if attr.has_name(sym::panic_handler) => (sym::panic_impl, attr.span),
140 language_item_table! {
141 // Variant name, Name, Method name, Target Generic requirements;
142 Sized, sym::sized, sized_trait, Target::Trait, GenericRequirement::Exact(0);
143 Unsize, sym::unsize, unsize_trait, Target::Trait, GenericRequirement::Minimum(1);
144 /// Trait injected by `#[derive(PartialEq)]`, (i.e. "Partial EQ").
145 StructuralPeq, sym::structural_peq, structural_peq_trait, Target::Trait, GenericRequirement::None;
146 /// Trait injected by `#[derive(Eq)]`, (i.e. "Total EQ"; no, I will not apologize).
147 StructuralTeq, sym::structural_teq, structural_teq_trait, Target::Trait, GenericRequirement::None;
148 Copy, sym::copy, copy_trait, Target::Trait, GenericRequirement::Exact(0);
149 Clone, sym::clone, clone_trait, Target::Trait, GenericRequirement::None;
150 Sync, sym::sync, sync_trait, Target::Trait, GenericRequirement::Exact(0);
151 DiscriminantKind, sym::discriminant_kind, discriminant_kind_trait, Target::Trait, GenericRequirement::None;
152 /// The associated item of the [`DiscriminantKind`] trait.
153 Discriminant, sym::discriminant_type, discriminant_type, Target::AssocTy, GenericRequirement::None;
155 PointeeTrait, sym::pointee_trait, pointee_trait, Target::Trait, GenericRequirement::None;
156 Metadata, sym::metadata_type, metadata_type, Target::AssocTy, GenericRequirement::None;
157 DynMetadata, sym::dyn_metadata, dyn_metadata, Target::Struct, GenericRequirement::None;
159 Freeze, sym::freeze, freeze_trait, Target::Trait, GenericRequirement::Exact(0);
161 Drop, sym::drop, drop_trait, Target::Trait, GenericRequirement::None;
162 Destruct, sym::destruct, destruct_trait, Target::Trait, GenericRequirement::None;
164 CoerceUnsized, sym::coerce_unsized, coerce_unsized_trait, Target::Trait, GenericRequirement::Minimum(1);
165 DispatchFromDyn, sym::dispatch_from_dyn, dispatch_from_dyn_trait, Target::Trait, GenericRequirement::Minimum(1);
167 // language items relating to transmutability
168 TransmuteOpts, sym::transmute_opts, transmute_opts, Target::Struct, GenericRequirement::Exact(0);
169 TransmuteTrait, sym::transmute_trait, transmute_trait, Target::Trait, GenericRequirement::Exact(3);
171 Add, sym::add, add_trait, Target::Trait, GenericRequirement::Exact(1);
172 Sub, sym::sub, sub_trait, Target::Trait, GenericRequirement::Exact(1);
173 Mul, sym::mul, mul_trait, Target::Trait, GenericRequirement::Exact(1);
174 Div, sym::div, div_trait, Target::Trait, GenericRequirement::Exact(1);
175 Rem, sym::rem, rem_trait, Target::Trait, GenericRequirement::Exact(1);
176 Neg, sym::neg, neg_trait, Target::Trait, GenericRequirement::Exact(0);
177 Not, sym::not, not_trait, Target::Trait, GenericRequirement::Exact(0);
178 BitXor, sym::bitxor, bitxor_trait, Target::Trait, GenericRequirement::Exact(1);
179 BitAnd, sym::bitand, bitand_trait, Target::Trait, GenericRequirement::Exact(1);
180 BitOr, sym::bitor, bitor_trait, Target::Trait, GenericRequirement::Exact(1);
181 Shl, sym::shl, shl_trait, Target::Trait, GenericRequirement::Exact(1);
182 Shr, sym::shr, shr_trait, Target::Trait, GenericRequirement::Exact(1);
183 AddAssign, sym::add_assign, add_assign_trait, Target::Trait, GenericRequirement::Exact(1);
184 SubAssign, sym::sub_assign, sub_assign_trait, Target::Trait, GenericRequirement::Exact(1);
185 MulAssign, sym::mul_assign, mul_assign_trait, Target::Trait, GenericRequirement::Exact(1);
186 DivAssign, sym::div_assign, div_assign_trait, Target::Trait, GenericRequirement::Exact(1);
187 RemAssign, sym::rem_assign, rem_assign_trait, Target::Trait, GenericRequirement::Exact(1);
188 BitXorAssign, sym::bitxor_assign, bitxor_assign_trait, Target::Trait, GenericRequirement::Exact(1);
189 BitAndAssign, sym::bitand_assign, bitand_assign_trait, Target::Trait, GenericRequirement::Exact(1);
190 BitOrAssign, sym::bitor_assign, bitor_assign_trait, Target::Trait, GenericRequirement::Exact(1);
191 ShlAssign, sym::shl_assign, shl_assign_trait, Target::Trait, GenericRequirement::Exact(1);
192 ShrAssign, sym::shr_assign, shr_assign_trait, Target::Trait, GenericRequirement::Exact(1);
193 Index, sym::index, index_trait, Target::Trait, GenericRequirement::Exact(1);
194 IndexMut, sym::index_mut, index_mut_trait, Target::Trait, GenericRequirement::Exact(1);
196 UnsafeCell, sym::unsafe_cell, unsafe_cell_type, Target::Struct, GenericRequirement::None;
197 VaList, sym::va_list, va_list, Target::Struct, GenericRequirement::None;
199 Deref, sym::deref, deref_trait, Target::Trait, GenericRequirement::Exact(0);
200 DerefMut, sym::deref_mut, deref_mut_trait, Target::Trait, GenericRequirement::Exact(0);
201 DerefTarget, sym::deref_target, deref_target, Target::AssocTy, GenericRequirement::None;
202 Receiver, sym::receiver, receiver_trait, Target::Trait, GenericRequirement::None;
204 Fn, kw::Fn, fn_trait, Target::Trait, GenericRequirement::Exact(1);
205 FnMut, sym::fn_mut, fn_mut_trait, Target::Trait, GenericRequirement::Exact(1);
206 FnOnce, sym::fn_once, fn_once_trait, Target::Trait, GenericRequirement::Exact(1);
208 FnOnceOutput, sym::fn_once_output, fn_once_output, Target::AssocTy, GenericRequirement::None;
210 Future, sym::future_trait, future_trait, Target::Trait, GenericRequirement::Exact(0);
211 GeneratorState, sym::generator_state, gen_state, Target::Enum, GenericRequirement::None;
212 Generator, sym::generator, gen_trait, Target::Trait, GenericRequirement::Minimum(1);
213 Unpin, sym::unpin, unpin_trait, Target::Trait, GenericRequirement::None;
214 Pin, sym::pin, pin_type, Target::Struct, GenericRequirement::None;
216 PartialEq, sym::eq, eq_trait, Target::Trait, GenericRequirement::Exact(1);
217 PartialOrd, sym::partial_ord, partial_ord_trait, Target::Trait, GenericRequirement::Exact(1);
219 // A number of panic-related lang items. The `panic` item corresponds to divide-by-zero and
220 // various panic cases with `match`. The `panic_bounds_check` item is for indexing arrays.
222 // The `begin_unwind` lang item has a predefined symbol name and is sort of a "weak lang item"
223 // in the sense that a crate is not required to have it defined to use it, but a final product
224 // is required to define it somewhere. Additionally, there are restrictions on crates that use
225 // a weak lang item, but do not have it defined.
226 Panic, sym::panic, panic_fn, Target::Fn, GenericRequirement::Exact(0);
227 PanicFmt, sym::panic_fmt, panic_fmt, Target::Fn, GenericRequirement::None;
228 PanicDisplay, sym::panic_display, panic_display, Target::Fn, GenericRequirement::None;
229 ConstPanicFmt, sym::const_panic_fmt, const_panic_fmt, Target::Fn, GenericRequirement::None;
230 PanicBoundsCheck, sym::panic_bounds_check, panic_bounds_check_fn, Target::Fn, GenericRequirement::Exact(0);
231 PanicInfo, sym::panic_info, panic_info, Target::Struct, GenericRequirement::None;
232 PanicLocation, sym::panic_location, panic_location, Target::Struct, GenericRequirement::None;
233 PanicImpl, sym::panic_impl, panic_impl, Target::Fn, GenericRequirement::None;
234 PanicNoUnwind, sym::panic_no_unwind, panic_no_unwind, Target::Fn, GenericRequirement::Exact(0);
235 /// libstd panic entry point. Necessary for const eval to be able to catch it
236 BeginPanic, sym::begin_panic, begin_panic_fn, Target::Fn, GenericRequirement::None;
238 ExchangeMalloc, sym::exchange_malloc, exchange_malloc_fn, Target::Fn, GenericRequirement::None;
239 BoxFree, sym::box_free, box_free_fn, Target::Fn, GenericRequirement::Minimum(1);
240 DropInPlace, sym::drop_in_place, drop_in_place_fn, Target::Fn, GenericRequirement::Minimum(1);
241 AllocLayout, sym::alloc_layout, alloc_layout, Target::Struct, GenericRequirement::None;
243 Start, sym::start, start_fn, Target::Fn, GenericRequirement::Exact(1);
245 EhPersonality, sym::eh_personality, eh_personality, Target::Fn, GenericRequirement::None;
246 EhCatchTypeinfo, sym::eh_catch_typeinfo, eh_catch_typeinfo, Target::Static, GenericRequirement::None;
248 OwnedBox, sym::owned_box, owned_box, Target::Struct, GenericRequirement::Minimum(1);
250 PhantomData, sym::phantom_data, phantom_data, Target::Struct, GenericRequirement::Exact(1);
252 ManuallyDrop, sym::manually_drop, manually_drop, Target::Struct, GenericRequirement::None;
254 MaybeUninit, sym::maybe_uninit, maybe_uninit, Target::Union, GenericRequirement::None;
256 /// Align offset for stride != 1; must not panic.
257 AlignOffset, sym::align_offset, align_offset_fn, Target::Fn, GenericRequirement::None;
259 Termination, sym::termination, termination, Target::Trait, GenericRequirement::None;
261 Try, sym::Try, try_trait, Target::Trait, GenericRequirement::None;
263 Tuple, sym::tuple_trait, tuple_trait, Target::Trait, GenericRequirement::Exact(0);
265 SliceLen, sym::slice_len_fn, slice_len_fn, Target::Method(MethodKind::Inherent), GenericRequirement::None;
267 // Language items from AST lowering
268 TryTraitFromResidual, sym::from_residual, from_residual_fn, Target::Method(MethodKind::Trait { body: false }), GenericRequirement::None;
269 TryTraitFromOutput, sym::from_output, from_output_fn, Target::Method(MethodKind::Trait { body: false }), GenericRequirement::None;
270 TryTraitBranch, sym::branch, branch_fn, Target::Method(MethodKind::Trait { body: false }), GenericRequirement::None;
271 TryTraitFromYeet, sym::from_yeet, from_yeet_fn, Target::Fn, GenericRequirement::None;
273 PollReady, sym::Ready, poll_ready_variant, Target::Variant, GenericRequirement::None;
274 PollPending, sym::Pending, poll_pending_variant, Target::Variant, GenericRequirement::None;
276 FromGenerator, sym::from_generator, from_generator_fn, Target::Fn, GenericRequirement::None;
277 GetContext, sym::get_context, get_context_fn, Target::Fn, GenericRequirement::None;
279 FuturePoll, sym::poll, future_poll_fn, Target::Method(MethodKind::Trait { body: false }), GenericRequirement::None;
281 FromFrom, sym::from, from_fn, Target::Method(MethodKind::Trait { body: false }), GenericRequirement::None;
283 OptionSome, sym::Some, option_some_variant, Target::Variant, GenericRequirement::None;
284 OptionNone, sym::None, option_none_variant, Target::Variant, GenericRequirement::None;
286 ResultOk, sym::Ok, result_ok_variant, Target::Variant, GenericRequirement::None;
287 ResultErr, sym::Err, result_err_variant, Target::Variant, GenericRequirement::None;
289 ControlFlowContinue, sym::Continue, cf_continue_variant, Target::Variant, GenericRequirement::None;
290 ControlFlowBreak, sym::Break, cf_break_variant, Target::Variant, GenericRequirement::None;
292 IntoFutureIntoFuture, sym::into_future, into_future_fn, Target::Method(MethodKind::Trait { body: false }), GenericRequirement::None;
293 IntoIterIntoIter, sym::into_iter, into_iter_fn, Target::Method(MethodKind::Trait { body: false }), GenericRequirement::None;
294 IteratorNext, sym::next, next_fn, Target::Method(MethodKind::Trait { body: false}), GenericRequirement::None;
296 PinNewUnchecked, sym::new_unchecked, new_unchecked_fn, Target::Method(MethodKind::Inherent), GenericRequirement::None;
298 RangeFrom, sym::RangeFrom, range_from_struct, Target::Struct, GenericRequirement::None;
299 RangeFull, sym::RangeFull, range_full_struct, Target::Struct, GenericRequirement::None;
300 RangeInclusiveStruct, sym::RangeInclusive, range_inclusive_struct, Target::Struct, GenericRequirement::None;
301 RangeInclusiveNew, sym::range_inclusive_new, range_inclusive_new_method, Target::Method(MethodKind::Inherent), GenericRequirement::None;
302 Range, sym::Range, range_struct, Target::Struct, GenericRequirement::None;
303 RangeToInclusive, sym::RangeToInclusive, range_to_inclusive_struct, Target::Struct, GenericRequirement::None;
304 RangeTo, sym::RangeTo, range_to_struct, Target::Struct, GenericRequirement::None;
307 pub enum GenericRequirement {
313 pub static FN_TRAITS: &'static [LangItem] = &[LangItem::Fn, LangItem::FnMut, LangItem::FnOnce];
315 pub static OPERATORS: &'static [LangItem] = &[
333 LangItem::BitXorAssign,
334 LangItem::BitAndAssign,
335 LangItem::BitOrAssign,
341 LangItem::PartialOrd,