compiler/rustc_hir/src/lang_items.rs

   1 //! Defines language items.
   2 //!
   3 //! Language items are items that represent concepts intrinsic to the language
   4 //! itself. Examples are:
   5 //!
   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.
   9
  10 use crate::def_id::DefId;
  11 use crate::{MethodKind, Target};
  12
  13 use rustc_ast as ast;
  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};
  18 use rustc_span::Span;
  19
  20 use std::lazy::SyncLazy;
  21
  22 pub enum LangItemGroup {
  23     Op,
  24 }
  25
  26 const NUM_GROUPS: usize = 1;
  27
  28 macro_rules! expand_group {
  29     () => {
  30         None
  31     };
  32     ($group:expr) => {
  33         Some($group)
  34     };
  35 }
  36
  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 {
  40     (
  41         $( $(#[$attr:meta])* $variant:ident $($group:expr)?, $module:ident :: $name:ident, $method:ident, $target:expr; )*
  42     ) => {
  43
  44         enum_from_u32! {
  45             /// A representation of all the valid language items in Rust.
  46             #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, Encodable, Decodable)]
  47             pub enum LangItem {
  48                 $(
  49                     #[doc = concat!("The `", stringify!($name), "` lang item.")]
  50                     ///
  51                     $(#[$attr])*
  52                     $variant,
  53                 )*
  54             }
  55         }
  56
  57         impl LangItem {
  58             /// Returns the `name` symbol in `#[lang = "$name"]`.
  59             /// For example, [`LangItem::PartialEq`]`.name()`
  60             /// would result in [`sym::eq`] since it is `#[lang = "eq"]`.
  61             pub fn name(self) -> Symbol {
  62                 match self {
  63                     $( LangItem::$variant => $module::$name, )*
  64                 }
  65             }
  66
  67             /// The [group](LangItemGroup) that this lang item belongs to,
  68             /// or `None` if it doesn't belong to a group.
  69             pub fn group(self) -> Option<LangItemGroup> {
  70                 use LangItemGroup::*;
  71                 match self {
  72                     $( LangItem::$variant => expand_group!($($group)*), )*
  73                 }
  74             }
  75         }
  76
  77         /// All of the language items, defined or not.
  78         /// Defined lang items can come from the current crate or its dependencies.
  79         #[derive(HashStable_Generic, Debug)]
  80         pub struct LanguageItems {
  81             /// Mappings from lang items to their possibly found [`DefId`]s.
  82             /// The index corresponds to the order in [`LangItem`].
  83             pub items: Vec<Option<DefId>>,
  84             /// Lang items that were not found during collection.
  85             pub missing: Vec<LangItem>,
  86             /// Mapping from [`LangItemGroup`] discriminants to all
  87             /// [`DefId`]s of lang items in that group.
  88             pub groups: [Vec<DefId>; NUM_GROUPS],
  89         }
  90
  91         impl LanguageItems {
  92             /// Construct an empty collection of lang items and no missing ones.
  93             pub fn new() -> Self {
  94                 fn init_none(_: LangItem) -> Option<DefId> { None }
  95
  96                 Self {
  97                     items: vec![$(init_none(LangItem::$variant)),*],
  98                     missing: Vec::new(),
  99                     groups: [vec![]; NUM_GROUPS],
 100                 }
 101             }
 102
 103             /// Returns the mappings to the possibly found `DefId`s for each lang item.
 104             pub fn items(&self) -> &[Option<DefId>] {
 105                 &*self.items
 106             }
 107
 108             /// Requires that a given `LangItem` was bound and returns the corresponding `DefId`.
 109             /// If it wasn't bound, e.g. due to a missing `#[lang = "<it.name()>"]`,
 110             /// returns an error message as a string.
 111             pub fn require(&self, it: LangItem) -> Result<DefId, String> {
 112                 self.items[it as usize].ok_or_else(|| format!("requires `{}` lang_item", it.name()))
 113             }
 114
 115             /// Returns the [`DefId`]s of all lang items in a group.
 116             pub fn group(&self, group: LangItemGroup) -> &[DefId] {
 117                 self.groups[group as usize].as_ref()
 118             }
 119
 120             $(
 121                 #[doc = concat!("Returns the [`DefId`] of the `", stringify!($name), "` lang item if it is defined.")]
 122                 #[allow(dead_code)]
 123                 pub fn $method(&self) -> Option<DefId> {
 124                     self.items[LangItem::$variant as usize]
 125                 }
 126             )*
 127         }
 128
 129         /// A mapping from the name of the lang item to its order and the form it must be of.
 130         pub static ITEM_REFS: SyncLazy<FxHashMap<Symbol, (usize, Target)>> = SyncLazy::new(|| {
 131             let mut item_refs = FxHashMap::default();
 132             $( item_refs.insert($module::$name, (LangItem::$variant as usize, $target)); )*
 133             item_refs
 134         });
 135
 136 // End of the macro
 137     }
 138 }
 139
 140 impl<CTX> HashStable<CTX> for LangItem {
 141     fn hash_stable(&self, _: &mut CTX, hasher: &mut StableHasher) {
 142         ::std::hash::Hash::hash(self, hasher);
 143     }
 144 }
 145
 146 /// Extracts the first `lang = "$name"` out of a list of attributes.
 147 /// The attributes `#[panic_handler]` and `#[alloc_error_handler]`
 148 /// are also extracted out when found.
 149 ///
 150 /// About the `check_name` argument: passing in a `Session` would be simpler,
 151 /// because then we could call `Session::check_name` directly. But we want to
 152 /// avoid the need for `rustc_hir` to depend on `rustc_session`, so we
 153 /// use a closure instead.
 154 pub fn extract<'a, F>(check_name: F, attrs: &'a [ast::Attribute]) -> Option<(Symbol, Span)>
 155 where
 156     F: Fn(&'a ast::Attribute, Symbol) -> bool,
 157 {
 158     attrs.iter().find_map(|attr| {
 159         Some(match attr {
 160             _ if check_name(attr, sym::lang) => (attr.value_str()?, attr.span),
 161             _ if check_name(attr, sym::panic_handler) => (sym::panic_impl, attr.span),
 162             _ if check_name(attr, sym::alloc_error_handler) => (sym::oom, attr.span),
 163             _ => return None,
 164         })
 165     })
 166 }
 167
 168 language_item_table! {
 169 //  Variant name,            Name,                     Method name,                Target;
 170     Bool,                    sym::bool,                bool_impl,                  Target::Impl;
 171     Char,                    sym::char,                char_impl,                  Target::Impl;
 172     Str,                     sym::str,                 str_impl,                   Target::Impl;
 173     Array,                   sym::array,               array_impl,                 Target::Impl;
 174     Slice,                   sym::slice,               slice_impl,                 Target::Impl;
 175     SliceU8,                 sym::slice_u8,            slice_u8_impl,              Target::Impl;
 176     StrAlloc,                sym::str_alloc,           str_alloc_impl,             Target::Impl;
 177     SliceAlloc,              sym::slice_alloc,         slice_alloc_impl,           Target::Impl;
 178     SliceU8Alloc,            sym::slice_u8_alloc,      slice_u8_alloc_impl,        Target::Impl;
 179     ConstPtr,                sym::const_ptr,           const_ptr_impl,             Target::Impl;
 180     MutPtr,                  sym::mut_ptr,             mut_ptr_impl,               Target::Impl;
 181     ConstSlicePtr,           sym::const_slice_ptr,     const_slice_ptr_impl,       Target::Impl;
 182     MutSlicePtr,             sym::mut_slice_ptr,       mut_slice_ptr_impl,         Target::Impl;
 183     I8,                      sym::i8,                  i8_impl,                    Target::Impl;
 184     I16,                     sym::i16,                 i16_impl,                   Target::Impl;
 185     I32,                     sym::i32,                 i32_impl,                   Target::Impl;
 186     I64,                     sym::i64,                 i64_impl,                   Target::Impl;
 187     I128,                    sym::i128,                i128_impl,                  Target::Impl;
 188     Isize,                   sym::isize,               isize_impl,                 Target::Impl;
 189     U8,                      sym::u8,                  u8_impl,                    Target::Impl;
 190     U16,                     sym::u16,                 u16_impl,                   Target::Impl;
 191     U32,                     sym::u32,                 u32_impl,                   Target::Impl;
 192     U64,                     sym::u64,                 u64_impl,                   Target::Impl;
 193     U128,                    sym::u128,                u128_impl,                  Target::Impl;
 194     Usize,                   sym::usize,               usize_impl,                 Target::Impl;
 195     F32,                     sym::f32,                 f32_impl,                   Target::Impl;
 196     F64,                     sym::f64,                 f64_impl,                   Target::Impl;
 197     F32Runtime,              sym::f32_runtime,         f32_runtime_impl,           Target::Impl;
 198     F64Runtime,              sym::f64_runtime,         f64_runtime_impl,           Target::Impl;
 199
 200     Sized,                   sym::sized,               sized_trait,                Target::Trait;
 201     Unsize,                  sym::unsize,              unsize_trait,               Target::Trait;
 202     /// Trait injected by `#[derive(PartialEq)]`, (i.e. "Partial EQ").
 203     StructuralPeq,           sym::structural_peq,      structural_peq_trait,       Target::Trait;
 204     /// Trait injected by `#[derive(Eq)]`, (i.e. "Total EQ"; no, I will not apologize).
 205     StructuralTeq,           sym::structural_teq,      structural_teq_trait,       Target::Trait;
 206     Copy,                    sym::copy,                copy_trait,                 Target::Trait;
 207     Clone,                   sym::clone,               clone_trait,                Target::Trait;
 208     Sync,                    sym::sync,                sync_trait,                 Target::Trait;
 209     DiscriminantKind,        sym::discriminant_kind,   discriminant_kind_trait,    Target::Trait;
 210     /// The associated item of the [`DiscriminantKind`] trait.
 211     Discriminant,            sym::discriminant_type,   discriminant_type,          Target::AssocTy;
 212
 213     PointeeTrait,            sym::pointee_trait,       pointee_trait,              Target::Trait;
 214     Metadata,                sym::metadata_type,       metadata_type,              Target::AssocTy;
 215     DynMetadata,             sym::dyn_metadata,        dyn_metadata,               Target::Struct;
 216
 217     Freeze,                  sym::freeze,              freeze_trait,               Target::Trait;
 218
 219     Drop,                    sym::drop,                drop_trait,                 Target::Trait;
 220
 221     CoerceUnsized,           sym::coerce_unsized,      coerce_unsized_trait,       Target::Trait;
 222     DispatchFromDyn,         sym::dispatch_from_dyn,   dispatch_from_dyn_trait,    Target::Trait;
 223
 224     Add(Op),                 sym::add,                 add_trait,                  Target::Trait;
 225     Sub(Op),                 sym::sub,                 sub_trait,                  Target::Trait;
 226     Mul(Op),                 sym::mul,                 mul_trait,                  Target::Trait;
 227     Div(Op),                 sym::div,                 div_trait,                  Target::Trait;
 228     Rem(Op),                 sym::rem,                 rem_trait,                  Target::Trait;
 229     Neg(Op),                 sym::neg,                 neg_trait,                  Target::Trait;
 230     Not(Op),                 sym::not,                 not_trait,                  Target::Trait;
 231     BitXor(Op),              sym::bitxor,              bitxor_trait,               Target::Trait;
 232     BitAnd(Op),              sym::bitand,              bitand_trait,               Target::Trait;
 233     BitOr(Op),               sym::bitor,               bitor_trait,                Target::Trait;
 234     Shl(Op),                 sym::shl,                 shl_trait,                  Target::Trait;
 235     Shr(Op),                 sym::shr,                 shr_trait,                  Target::Trait;
 236     AddAssign(Op),           sym::add_assign,          add_assign_trait,           Target::Trait;
 237     SubAssign(Op),           sym::sub_assign,          sub_assign_trait,           Target::Trait;
 238     MulAssign(Op),           sym::mul_assign,          mul_assign_trait,           Target::Trait;
 239     DivAssign(Op),           sym::div_assign,          div_assign_trait,           Target::Trait;
 240     RemAssign(Op),           sym::rem_assign,          rem_assign_trait,           Target::Trait;
 241     BitXorAssign(Op),        sym::bitxor_assign,       bitxor_assign_trait,        Target::Trait;
 242     BitAndAssign(Op),        sym::bitand_assign,       bitand_assign_trait,        Target::Trait;
 243     BitOrAssign(Op),         sym::bitor_assign,        bitor_assign_trait,         Target::Trait;
 244     ShlAssign(Op),           sym::shl_assign,          shl_assign_trait,           Target::Trait;
 245     ShrAssign(Op),           sym::shr_assign,          shr_assign_trait,           Target::Trait;
 246     Index(Op),               sym::index,               index_trait,                Target::Trait;
 247     IndexMut(Op),            sym::index_mut,           index_mut_trait,            Target::Trait;
 248
 249     UnsafeCell,              sym::unsafe_cell,         unsafe_cell_type,           Target::Struct;
 250     VaList,                  sym::va_list,             va_list,                    Target::Struct;
 251
 252     Deref,                   sym::deref,               deref_trait,                Target::Trait;
 253     DerefMut,                sym::deref_mut,           deref_mut_trait,            Target::Trait;
 254     DerefTarget,             sym::deref_target,        deref_target,               Target::AssocTy;
 255     Receiver,                sym::receiver,            receiver_trait,             Target::Trait;
 256
 257     Fn,                      kw::Fn,                   fn_trait,                   Target::Trait;
 258     FnMut,                   sym::fn_mut,              fn_mut_trait,               Target::Trait;
 259     FnOnce,                  sym::fn_once,             fn_once_trait,              Target::Trait;
 260
 261     FnOnceOutput,            sym::fn_once_output,      fn_once_output,             Target::AssocTy;
 262
 263     Future,                  sym::future_trait,        future_trait,               Target::Trait;
 264     GeneratorState,          sym::generator_state,     gen_state,                  Target::Enum;
 265     Generator,               sym::generator,           gen_trait,                  Target::Trait;
 266     Unpin,                   sym::unpin,               unpin_trait,                Target::Trait;
 267     Pin,                     sym::pin,                 pin_type,                   Target::Struct;
 268
 269     PartialEq,               sym::eq,                  eq_trait,                   Target::Trait;
 270     PartialOrd,              sym::partial_ord,         partial_ord_trait,          Target::Trait;
 271
 272     // A number of panic-related lang items. The `panic` item corresponds to divide-by-zero and
 273     // various panic cases with `match`. The `panic_bounds_check` item is for indexing arrays.
 274     //
 275     // The `begin_unwind` lang item has a predefined symbol name and is sort of a "weak lang item"
 276     // in the sense that a crate is not required to have it defined to use it, but a final product
 277     // is required to define it somewhere. Additionally, there are restrictions on crates that use
 278     // a weak lang item, but do not have it defined.
 279     Panic,                   sym::panic,               panic_fn,                   Target::Fn;
 280     PanicStr,                sym::panic_str,           panic_str,                  Target::Fn;
 281     PanicBoundsCheck,        sym::panic_bounds_check,  panic_bounds_check_fn,      Target::Fn;
 282     PanicInfo,               sym::panic_info,          panic_info,                 Target::Struct;
 283     PanicLocation,           sym::panic_location,      panic_location,             Target::Struct;
 284     PanicImpl,               sym::panic_impl,          panic_impl,                 Target::Fn;
 285     /// libstd panic entry point. Necessary for const eval to be able to catch it
 286     BeginPanic,              sym::begin_panic,         begin_panic_fn,             Target::Fn;
 287
 288     ExchangeMalloc,          sym::exchange_malloc,     exchange_malloc_fn,         Target::Fn;
 289     BoxFree,                 sym::box_free,            box_free_fn,                Target::Fn;
 290     DropInPlace,             sym::drop_in_place,       drop_in_place_fn,           Target::Fn;
 291     Oom,                     sym::oom,                 oom,                        Target::Fn;
 292     AllocLayout,             sym::alloc_layout,        alloc_layout,               Target::Struct;
 293
 294     Start,                   sym::start,               start_fn,                   Target::Fn;
 295
 296     EhPersonality,           sym::eh_personality,      eh_personality,             Target::Fn;
 297     EhCatchTypeinfo,         sym::eh_catch_typeinfo,   eh_catch_typeinfo,          Target::Static;
 298
 299     OwnedBox,                sym::owned_box,           owned_box,                  Target::Struct;
 300
 301     PhantomData,             sym::phantom_data,        phantom_data,               Target::Struct;
 302
 303     ManuallyDrop,            sym::manually_drop,       manually_drop,              Target::Struct;
 304
 305     MaybeUninit,             sym::maybe_uninit,        maybe_uninit,               Target::Union;
 306
 307     /// Align offset for stride != 1; must not panic.
 308     AlignOffset,             sym::align_offset,        align_offset_fn,            Target::Fn;
 309
 310     Termination,             sym::termination,         termination,                Target::Trait;
 311
 312     Try,                     kw::Try,                  try_trait,                  Target::Trait;
 313
 314     // Language items from AST lowering
 315     TryFromError,            sym::from_error,          from_error_fn,              Target::Method(MethodKind::Trait { body: false });
 316     TryFromOk,               sym::from_ok,             from_ok_fn,                 Target::Method(MethodKind::Trait { body: false });
 317     TryIntoResult,           sym::into_result,         into_result_fn,             Target::Method(MethodKind::Trait { body: false });
 318
 319     PollReady,               sym::Ready,               poll_ready_variant,         Target::Variant;
 320     PollPending,             sym::Pending,             poll_pending_variant,       Target::Variant;
 321
 322     FromGenerator,           sym::from_generator,      from_generator_fn,          Target::Fn;
 323     GetContext,              sym::get_context,         get_context_fn,             Target::Fn;
 324
 325     FuturePoll,              sym::poll,                future_poll_fn,             Target::Method(MethodKind::Trait { body: false });
 326
 327     FromFrom,                sym::from,                from_fn,                    Target::Method(MethodKind::Trait { body: false });
 328
 329     OptionSome,              sym::Some,                option_some_variant,        Target::Variant;
 330     OptionNone,              sym::None,                option_none_variant,        Target::Variant;
 331
 332     ResultOk,                sym::Ok,                  result_ok_variant,          Target::Variant;
 333     ResultErr,               sym::Err,                 result_err_variant,         Target::Variant;
 334
 335     IntoIterIntoIter,        sym::into_iter,           into_iter_fn,               Target::Method(MethodKind::Trait { body: false });
 336     IteratorNext,            sym::next,                next_fn,                    Target::Method(MethodKind::Trait { body: false});
 337
 338     PinNewUnchecked,         sym::new_unchecked,       new_unchecked_fn,           Target::Method(MethodKind::Inherent);
 339
 340     RangeFrom,               sym::RangeFrom,           range_from_struct,          Target::Struct;
 341     RangeFull,               sym::RangeFull,           range_full_struct,          Target::Struct;
 342     RangeInclusiveStruct,    sym::RangeInclusive,      range_inclusive_struct,     Target::Struct;
 343     RangeInclusiveNew,       sym::range_inclusive_new, range_inclusive_new_method, Target::Method(MethodKind::Inherent);
 344     Range,                   sym::Range,               range_struct,               Target::Struct;
 345     RangeToInclusive,        sym::RangeToInclusive,    range_to_inclusive_struct,  Target::Struct;
 346     RangeTo,                 sym::RangeTo,             range_to_struct,            Target::Struct;
 347 }