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, $target:expr; )*
45 /// A representation of all the valid language items in Rust.
46 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, Encodable, Decodable)]
49 #[doc = concat!("The `", stringify!($name), "` lang item.")]
56 /// Returns the `name` symbol in `#[lang = "$name"]`.
57 /// For example, [`LangItem::PartialEq`]`.name()`
58 /// would result in [`sym::eq`] since it is `#[lang = "eq"]`.
59 pub fn name(self) -> Symbol {
61 $( LangItem::$variant => $name, )*
65 /// The [group](LangItemGroup) that this lang item belongs to,
66 /// or `None` if it doesn't belong to a group.
67 pub fn group(self) -> Option<LangItemGroup> {
70 $( LangItem::$variant => expand_group!($($group)*), )*
75 /// All of the language items in the current crate, defined or not.
76 #[derive(HashStable_Generic, Debug)]
77 pub struct LanguageItems {
78 /// Mappings from lang items to their possibly found [`DefId`]s.
79 /// The index corresponds to the order in [`LangItem`].
80 pub items: Vec<Option<DefId>>,
81 /// Lang items that were not found during collection.
82 pub missing: Vec<LangItem>,
83 /// Mapping from [`LangItemGroup`] discriminants to all
84 /// [`DefId`]s of lang items in that group.
85 pub groups: [Vec<DefId>; NUM_GROUPS],
89 /// Construct an empty collection of lang items and no missing ones.
90 pub fn new() -> Self {
91 fn init_none(_: LangItem) -> Option<DefId> { None }
94 items: vec![$(init_none(LangItem::$variant)),*],
96 groups: [vec![]; NUM_GROUPS],
100 /// Returns the mappings to the possibly found `DefId`s for each lang item.
101 pub fn items(&self) -> &[Option<DefId>] {
105 /// Requires that a given `LangItem` was bound and returns the corresponding `DefId`.
106 /// If it wasn't bound, e.g. due to a missing `#[lang = "<it.name()>"]`,
107 /// returns an error message as a string.
108 pub fn require(&self, it: LangItem) -> Result<DefId, String> {
109 self.items[it as usize].ok_or_else(|| format!("requires `{}` lang_item", it.name()))
112 /// Returns the [`DefId`]s of all lang items in a group.
113 pub fn group(&self, group: LangItemGroup) -> &[DefId] {
114 self.groups[group as usize].as_ref()
118 #[doc = concat!("Returns the [`DefId`] of the `", stringify!($name), "` lang item if it is defined.")]
120 pub fn $method(&self) -> Option<DefId> {
121 self.items[LangItem::$variant as usize]
126 /// A mapping from the name of the lang item to its order and the form it must be of.
127 pub static ITEM_REFS: SyncLazy<FxHashMap<Symbol, (usize, Target)>> = SyncLazy::new(|| {
128 let mut item_refs = FxHashMap::default();
129 $( item_refs.insert($name, (LangItem::$variant as usize, $target)); )*
137 impl<CTX> HashStable<CTX> for LangItem {
138 fn hash_stable(&self, _: &mut CTX, hasher: &mut StableHasher) {
139 ::std::hash::Hash::hash(self, hasher);
143 /// Extracts the first `lang = "$name"` out of a list of attributes.
144 /// The attributes `#[panic_handler]` and `#[alloc_error_handler]`
145 /// are also extracted out when found.
147 /// About the `check_name` argument: passing in a `Session` would be simpler,
148 /// because then we could call `Session::check_name` directly. But we want to
149 /// avoid the need for `rustc_hir` to depend on `rustc_session`, so we
150 /// use a closure instead.
151 pub fn extract<'a, F>(check_name: F, attrs: &'a [ast::Attribute]) -> Option<(Symbol, Span)>
153 F: Fn(&'a ast::Attribute, Symbol) -> bool,
155 attrs.iter().find_map(|attr| {
157 _ if check_name(attr, sym::lang) => (attr.value_str()?, attr.span),
158 _ if check_name(attr, sym::panic_handler) => (sym::panic_impl, attr.span),
159 _ if check_name(attr, sym::alloc_error_handler) => (sym::oom, attr.span),
165 language_item_table! {
166 // Variant name, Name, Method name, Target;
167 Bool, sym::bool, bool_impl, Target::Impl;
168 Char, sym::char, char_impl, Target::Impl;
169 Str, sym::str, str_impl, Target::Impl;
170 Array, sym::array, array_impl, Target::Impl;
171 Slice, sym::slice, slice_impl, Target::Impl;
172 SliceU8, sym::slice_u8, slice_u8_impl, Target::Impl;
173 StrAlloc, sym::str_alloc, str_alloc_impl, Target::Impl;
174 SliceAlloc, sym::slice_alloc, slice_alloc_impl, Target::Impl;
175 SliceU8Alloc, sym::slice_u8_alloc, slice_u8_alloc_impl, Target::Impl;
176 ConstPtr, sym::const_ptr, const_ptr_impl, Target::Impl;
177 MutPtr, sym::mut_ptr, mut_ptr_impl, Target::Impl;
178 ConstSlicePtr, sym::const_slice_ptr, const_slice_ptr_impl, Target::Impl;
179 MutSlicePtr, sym::mut_slice_ptr, mut_slice_ptr_impl, Target::Impl;
180 I8, sym::i8, i8_impl, Target::Impl;
181 I16, sym::i16, i16_impl, Target::Impl;
182 I32, sym::i32, i32_impl, Target::Impl;
183 I64, sym::i64, i64_impl, Target::Impl;
184 I128, sym::i128, i128_impl, Target::Impl;
185 Isize, sym::isize, isize_impl, Target::Impl;
186 U8, sym::u8, u8_impl, Target::Impl;
187 U16, sym::u16, u16_impl, Target::Impl;
188 U32, sym::u32, u32_impl, Target::Impl;
189 U64, sym::u64, u64_impl, Target::Impl;
190 U128, sym::u128, u128_impl, Target::Impl;
191 Usize, sym::usize, usize_impl, Target::Impl;
192 F32, sym::f32, f32_impl, Target::Impl;
193 F64, sym::f64, f64_impl, Target::Impl;
194 F32Runtime, sym::f32_runtime, f32_runtime_impl, Target::Impl;
195 F64Runtime, sym::f64_runtime, f64_runtime_impl, Target::Impl;
197 Sized, sym::sized, sized_trait, Target::Trait;
198 Unsize, sym::unsize, unsize_trait, Target::Trait;
199 // Trait injected by #[derive(PartialEq)], (i.e. "Partial EQ").
200 StructuralPeq, sym::structural_peq, structural_peq_trait, Target::Trait;
201 // Trait injected by #[derive(Eq)], (i.e. "Total EQ"; no, I will not apologize).
202 StructuralTeq, sym::structural_teq, structural_teq_trait, Target::Trait;
203 Copy, sym::copy, copy_trait, Target::Trait;
204 Clone, sym::clone, clone_trait, Target::Trait;
205 Sync, sym::sync, sync_trait, Target::Trait;
206 DiscriminantKind, sym::discriminant_kind, discriminant_kind_trait, Target::Trait;
207 // The associated item of `trait DiscriminantKind`.
208 Discriminant, sym::discriminant_type, discriminant_type, Target::AssocTy;
210 PointeeTrait, sym::pointee_trait, pointee_trait, Target::Trait;
211 Metadata, sym::metadata_type, metadata_type, Target::AssocTy;
212 DynMetadata, sym::dyn_metadata, dyn_metadata, Target::Struct;
214 Freeze, sym::freeze, freeze_trait, Target::Trait;
216 Drop, sym::drop, drop_trait, Target::Trait;
218 CoerceUnsized, sym::coerce_unsized, coerce_unsized_trait, Target::Trait;
219 DispatchFromDyn, sym::dispatch_from_dyn, dispatch_from_dyn_trait, Target::Trait;
221 Add(Op), sym::add, add_trait, Target::Trait;
222 Sub(Op), sym::sub, sub_trait, Target::Trait;
223 Mul(Op), sym::mul, mul_trait, Target::Trait;
224 Div(Op), sym::div, div_trait, Target::Trait;
225 Rem(Op), sym::rem, rem_trait, Target::Trait;
226 Neg(Op), sym::neg, neg_trait, Target::Trait;
227 Not(Op), sym::not, not_trait, Target::Trait;
228 BitXor(Op), sym::bitxor, bitxor_trait, Target::Trait;
229 BitAnd(Op), sym::bitand, bitand_trait, Target::Trait;
230 BitOr(Op), sym::bitor, bitor_trait, Target::Trait;
231 Shl(Op), sym::shl, shl_trait, Target::Trait;
232 Shr(Op), sym::shr, shr_trait, Target::Trait;
233 AddAssign(Op), sym::add_assign, add_assign_trait, Target::Trait;
234 SubAssign(Op), sym::sub_assign, sub_assign_trait, Target::Trait;
235 MulAssign(Op), sym::mul_assign, mul_assign_trait, Target::Trait;
236 DivAssign(Op), sym::div_assign, div_assign_trait, Target::Trait;
237 RemAssign(Op), sym::rem_assign, rem_assign_trait, Target::Trait;
238 BitXorAssign(Op), sym::bitxor_assign, bitxor_assign_trait, Target::Trait;
239 BitAndAssign(Op), sym::bitand_assign, bitand_assign_trait, Target::Trait;
240 BitOrAssign(Op), sym::bitor_assign, bitor_assign_trait, Target::Trait;
241 ShlAssign(Op), sym::shl_assign, shl_assign_trait, Target::Trait;
242 ShrAssign(Op), sym::shr_assign, shr_assign_trait, Target::Trait;
243 Index(Op), sym::index, index_trait, Target::Trait;
244 IndexMut(Op), sym::index_mut, index_mut_trait, Target::Trait;
246 UnsafeCell, sym::unsafe_cell, unsafe_cell_type, Target::Struct;
247 VaList, sym::va_list, va_list, Target::Struct;
249 Deref, sym::deref, deref_trait, Target::Trait;
250 DerefMut, sym::deref_mut, deref_mut_trait, Target::Trait;
251 DerefTarget, sym::deref_target, deref_target, Target::AssocTy;
252 Receiver, sym::receiver, receiver_trait, Target::Trait;
254 Fn, kw::Fn, fn_trait, Target::Trait;
255 FnMut, sym::fn_mut, fn_mut_trait, Target::Trait;
256 FnOnce, sym::fn_once, fn_once_trait, Target::Trait;
258 FnOnceOutput, sym::fn_once_output, fn_once_output, Target::AssocTy;
260 Future, sym::future_trait, future_trait, Target::Trait;
261 GeneratorState, sym::generator_state, gen_state, Target::Enum;
262 Generator, sym::generator, gen_trait, Target::Trait;
263 Unpin, sym::unpin, unpin_trait, Target::Trait;
264 Pin, sym::pin, pin_type, Target::Struct;
266 PartialEq, sym::eq, eq_trait, Target::Trait;
267 PartialOrd, sym::partial_ord, partial_ord_trait, Target::Trait;
269 // A number of panic-related lang items. The `panic` item corresponds to divide-by-zero and
270 // various panic cases with `match`. The `panic_bounds_check` item is for indexing arrays.
272 // The `begin_unwind` lang item has a predefined symbol name and is sort of a "weak lang item"
273 // in the sense that a crate is not required to have it defined to use it, but a final product
274 // is required to define it somewhere. Additionally, there are restrictions on crates that use
275 // a weak lang item, but do not have it defined.
276 Panic, sym::panic, panic_fn, Target::Fn;
277 PanicStr, sym::panic_str, panic_str, Target::Fn;
278 PanicBoundsCheck, sym::panic_bounds_check, panic_bounds_check_fn, Target::Fn;
279 PanicInfo, sym::panic_info, panic_info, Target::Struct;
280 PanicLocation, sym::panic_location, panic_location, Target::Struct;
281 PanicImpl, sym::panic_impl, panic_impl, Target::Fn;
282 // libstd panic entry point. Necessary for const eval to be able to catch it
283 BeginPanic, sym::begin_panic, begin_panic_fn, Target::Fn;
285 ExchangeMalloc, sym::exchange_malloc, exchange_malloc_fn, Target::Fn;
286 BoxFree, sym::box_free, box_free_fn, Target::Fn;
287 DropInPlace, sym::drop_in_place, drop_in_place_fn, Target::Fn;
288 Oom, sym::oom, oom, Target::Fn;
289 AllocLayout, sym::alloc_layout, alloc_layout, Target::Struct;
291 Start, sym::start, start_fn, Target::Fn;
293 EhPersonality, sym::eh_personality, eh_personality, Target::Fn;
294 EhCatchTypeinfo, sym::eh_catch_typeinfo, eh_catch_typeinfo, Target::Static;
296 OwnedBox, sym::owned_box, owned_box, Target::Struct;
298 PhantomData, sym::phantom_data, phantom_data, Target::Struct;
300 ManuallyDrop, sym::manually_drop, manually_drop, Target::Struct;
302 MaybeUninit, sym::maybe_uninit, maybe_uninit, Target::Union;
304 // Align offset for stride != 1; must not panic.
305 AlignOffset, sym::align_offset, align_offset_fn, Target::Fn;
307 Termination, sym::termination, termination, Target::Trait;
309 Try, kw::Try, try_trait, Target::Trait;
311 // Language items from AST lowering
312 TryFromError, sym::from_error, from_error_fn, Target::Method(MethodKind::Trait { body: false });
313 TryFromOk, sym::from_ok, from_ok_fn, Target::Method(MethodKind::Trait { body: false });
314 TryIntoResult, sym::into_result, into_result_fn, Target::Method(MethodKind::Trait { body: false });
316 PollReady, sym::Ready, poll_ready_variant, Target::Variant;
317 PollPending, sym::Pending, poll_pending_variant, Target::Variant;
319 FromGenerator, sym::from_generator, from_generator_fn, Target::Fn;
320 GetContext, sym::get_context, get_context_fn, Target::Fn;
322 FuturePoll, sym::poll, future_poll_fn, Target::Method(MethodKind::Trait { body: false });
324 FromFrom, sym::from, from_fn, Target::Method(MethodKind::Trait { body: false });
326 OptionSome, sym::Some, option_some_variant, Target::Variant;
327 OptionNone, sym::None, option_none_variant, Target::Variant;
329 ResultOk, sym::Ok, result_ok_variant, Target::Variant;
330 ResultErr, sym::Err, result_err_variant, Target::Variant;
332 IntoIterIntoIter, sym::into_iter, into_iter_fn, Target::Method(MethodKind::Trait { body: false });
333 IteratorNext, sym::next, next_fn, Target::Method(MethodKind::Trait { body: false});
335 PinNewUnchecked, sym::new_unchecked, new_unchecked_fn, Target::Method(MethodKind::Inherent);
337 RangeFrom, sym::RangeFrom, range_from_struct, Target::Struct;
338 RangeFull, sym::RangeFull, range_full_struct, Target::Struct;
339 RangeInclusiveStruct, sym::RangeInclusive, range_inclusive_struct, Target::Struct;
340 RangeInclusiveNew, sym::range_inclusive_new, range_inclusive_new_method, Target::Method(MethodKind::Inherent);
341 Range, sym::Range, range_struct, Target::Struct;
342 RangeToInclusive, sym::RangeToInclusive, range_to_inclusive_struct, Target::Struct;
343 RangeTo, sym::RangeTo, range_to_struct, Target::Struct;