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lang_items.rs
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//! Defines language items.
//!
//! Language items are items that represent concepts intrinsic to the language
//! itself. Examples are:
//!
//! * Traits that specify "kinds"; e.g., `Sync`, `Send`.
//! * Traits that represent operators; e.g., `Add`, `Sub`, `Index`.
//! * Functions called by the compiler itself.
use crate::def_id::DefId;
use crate::{MethodKind, Target};
use rustc_ast as ast;
use rustc_data_structures::fx::FxHashMap;
use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
use rustc_macros::HashStable_Generic;
use rustc_span::symbol::{kw, sym, Symbol};
use rustc_span::Span;
use std::lazy::SyncLazy;
pub enum LangItemGroup {
Op,
}
const NUM_GROUPS: usize = 1;
macro_rules! expand_group {
() => {
None
};
($group:expr) => {
Some($group)
};
}
// The actual lang items defined come at the end of this file in one handy table.
// So you probably just want to nip down to the end.
macro_rules! language_item_table {
(
$( $(#[$attr:meta])* $variant:ident $($group:expr)?, $module:ident :: $name:ident, $method:ident, $target:expr, $generics:expr; )*
) => {
enum_from_u32! {
/// A representation of all the valid language items in Rust.
#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, Encodable, Decodable)]
pub enum LangItem {
$(
#[doc = concat!("The `", stringify!($name), "` lang item.")]
///
$(#[$attr])*
$variant,
)*
}
}
impl LangItem {
/// Returns the `name` symbol in `#[lang = "$name"]`.
/// For example, [`LangItem::PartialEq`]`.name()`
/// would result in [`sym::eq`] since it is `#[lang = "eq"]`.
pub fn name(self) -> Symbol {
match self {
$( LangItem::$variant => $module::$name, )*
}
}
/// The [group](LangItemGroup) that this lang item belongs to,
/// or `None` if it doesn't belong to a group.
pub fn group(self) -> Option<LangItemGroup> {
use LangItemGroup::*;
match self {
$( LangItem::$variant => expand_group!($($group)*), )*
}
}
pub fn required_generics(&self) -> GenericRequirement {
match self {
$( LangItem::$variant => $generics, )*
}
}
}
/// All of the language items, defined or not.
/// Defined lang items can come from the current crate or its dependencies.
#[derive(HashStable_Generic, Debug)]
pub struct LanguageItems {
/// Mappings from lang items to their possibly found [`DefId`]s.
/// The index corresponds to the order in [`LangItem`].
pub items: Vec<Option<DefId>>,
/// Lang items that were not found during collection.
pub missing: Vec<LangItem>,
/// Mapping from [`LangItemGroup`] discriminants to all
/// [`DefId`]s of lang items in that group.
pub groups: [Vec<DefId>; NUM_GROUPS],
}
impl LanguageItems {
/// Construct an empty collection of lang items and no missing ones.
pub fn new() -> Self {
fn init_none(_: LangItem) -> Option<DefId> { None }
Self {
items: vec![$(init_none(LangItem::$variant)),*],
missing: Vec::new(),
groups: [vec![]; NUM_GROUPS],
}
}
/// Returns the mappings to the possibly found `DefId`s for each lang item.
pub fn items(&self) -> &[Option<DefId>] {
&*self.items
}
/// Requires that a given `LangItem` was bound and returns the corresponding `DefId`.
/// If it wasn't bound, e.g. due to a missing `#[lang = "<it.name()>"]`,
/// returns an error message as a string.
pub fn require(&self, it: LangItem) -> Result<DefId, String> {
self.items[it as usize].ok_or_else(|| format!("requires `{}` lang_item", it.name()))
}
/// Returns the [`DefId`]s of all lang items in a group.
pub fn group(&self, group: LangItemGroup) -> &[DefId] {
self.groups[group as usize].as_ref()
}
$(
#[doc = concat!("Returns the [`DefId`] of the `", stringify!($name), "` lang item if it is defined.")]
pub fn $method(&self) -> Option<DefId> {
self.items[LangItem::$variant as usize]
}
)*
}
/// A mapping from the name of the lang item to its order and the form it must be of.
pub static ITEM_REFS: SyncLazy<FxHashMap<Symbol, (usize, Target)>> = SyncLazy::new(|| {
let mut item_refs = FxHashMap::default();
$( item_refs.insert($module::$name, (LangItem::$variant as usize, $target)); )*
item_refs
});
// End of the macro
}
}
impl<CTX> HashStable<CTX> for LangItem {
fn hash_stable(&self, _: &mut CTX, hasher: &mut StableHasher) {
::std::hash::Hash::hash(self, hasher);
}
}
/// Extracts the first `lang = "$name"` out of a list of attributes.
/// The attributes `#[panic_handler]` and `#[alloc_error_handler]`
/// are also extracted out when found.
///
/// About the `check_name` argument: passing in a `Session` would be simpler,
/// because then we could call `Session::check_name` directly. But we want to
/// avoid the need for `rustc_hir` to depend on `rustc_session`, so we
/// use a closure instead.
pub fn extract<'a, F>(check_name: F, attrs: &'a [ast::Attribute]) -> Option<(Symbol, Span)>
where
F: Fn(&'a ast::Attribute, Symbol) -> bool,
{
attrs.iter().find_map(|attr| {
Some(match attr {
_ if check_name(attr, sym::lang) => (attr.value_str()?, attr.span),
_ if check_name(attr, sym::panic_handler) => (sym::panic_impl, attr.span),
_ if check_name(attr, sym::alloc_error_handler) => (sym::oom, attr.span),
_ => return None,
})
})
}
language_item_table! {
// Variant name, Name, Method name, Target Generic requirements;
Bool, sym::bool, bool_impl, Target::Impl, GenericRequirement::None;
Char, sym::char, char_impl, Target::Impl, GenericRequirement::None;
Str, sym::str, str_impl, Target::Impl, GenericRequirement::None;
Array, sym::array, array_impl, Target::Impl, GenericRequirement::None;
Slice, sym::slice, slice_impl, Target::Impl, GenericRequirement::None;
SliceU8, sym::slice_u8, slice_u8_impl, Target::Impl, GenericRequirement::None;
StrAlloc, sym::str_alloc, str_alloc_impl, Target::Impl, GenericRequirement::None;
SliceAlloc, sym::slice_alloc, slice_alloc_impl, Target::Impl, GenericRequirement::None;
SliceU8Alloc, sym::slice_u8_alloc, slice_u8_alloc_impl, Target::Impl, GenericRequirement::None;
ConstPtr, sym::const_ptr, const_ptr_impl, Target::Impl, GenericRequirement::None;
MutPtr, sym::mut_ptr, mut_ptr_impl, Target::Impl, GenericRequirement::None;
ConstSlicePtr, sym::const_slice_ptr, const_slice_ptr_impl, Target::Impl, GenericRequirement::None;
ConstStrPtr, sym::const_str_ptr, const_str_ptr_impl, Target::Impl, GenericRequirement::None;
MutSlicePtr, sym::mut_slice_ptr, mut_slice_ptr_impl, Target::Impl, GenericRequirement::None;
MutStrPtr, sym::mut_str_ptr, mut_str_ptr_impl, Target::Impl, GenericRequirement::None;
I8, sym::i8, i8_impl, Target::Impl, GenericRequirement::None;
I16, sym::i16, i16_impl, Target::Impl, GenericRequirement::None;
I32, sym::i32, i32_impl, Target::Impl, GenericRequirement::None;
I64, sym::i64, i64_impl, Target::Impl, GenericRequirement::None;
I128, sym::i128, i128_impl, Target::Impl, GenericRequirement::None;
Isize, sym::isize, isize_impl, Target::Impl, GenericRequirement::None;
U8, sym::u8, u8_impl, Target::Impl, GenericRequirement::None;
U16, sym::u16, u16_impl, Target::Impl, GenericRequirement::None;
U32, sym::u32, u32_impl, Target::Impl, GenericRequirement::None;
U64, sym::u64, u64_impl, Target::Impl, GenericRequirement::None;
U128, sym::u128, u128_impl, Target::Impl, GenericRequirement::None;
Usize, sym::usize, usize_impl, Target::Impl, GenericRequirement::None;
F32, sym::f32, f32_impl, Target::Impl, GenericRequirement::None;
F64, sym::f64, f64_impl, Target::Impl, GenericRequirement::None;
F32Runtime, sym::f32_runtime, f32_runtime_impl, Target::Impl, GenericRequirement::None;
F64Runtime, sym::f64_runtime, f64_runtime_impl, Target::Impl, GenericRequirement::None;
Sized, sym::sized, sized_trait, Target::Trait, GenericRequirement::Exact(0);
Unsize, sym::unsize, unsize_trait, Target::Trait, GenericRequirement::Minimum(1);
/// Trait injected by `#[derive(PartialEq)]`, (i.e. "Partial EQ").
StructuralPeq, sym::structural_peq, structural_peq_trait, Target::Trait, GenericRequirement::None;
/// Trait injected by `#[derive(Eq)]`, (i.e. "Total EQ"; no, I will not apologize).
StructuralTeq, sym::structural_teq, structural_teq_trait, Target::Trait, GenericRequirement::None;
Copy, sym::copy, copy_trait, Target::Trait, GenericRequirement::Exact(0);
Clone, sym::clone, clone_trait, Target::Trait, GenericRequirement::None;
Sync, sym::sync, sync_trait, Target::Trait, GenericRequirement::Exact(0);
DiscriminantKind, sym::discriminant_kind, discriminant_kind_trait, Target::Trait, GenericRequirement::None;
/// The associated item of the [`DiscriminantKind`] trait.
Discriminant, sym::discriminant_type, discriminant_type, Target::AssocTy, GenericRequirement::None;
PointeeTrait, sym::pointee_trait, pointee_trait, Target::Trait, GenericRequirement::None;
Metadata, sym::metadata_type, metadata_type, Target::AssocTy, GenericRequirement::None;
DynMetadata, sym::dyn_metadata, dyn_metadata, Target::Struct, GenericRequirement::None;
Freeze, sym::freeze, freeze_trait, Target::Trait, GenericRequirement::Exact(0);
Drop, sym::drop, drop_trait, Target::Trait, GenericRequirement::None;
CoerceUnsized, sym::coerce_unsized, coerce_unsized_trait, Target::Trait, GenericRequirement::Minimum(1);
DispatchFromDyn, sym::dispatch_from_dyn, dispatch_from_dyn_trait, Target::Trait, GenericRequirement::Minimum(1);
Add(Op), sym::add, add_trait, Target::Trait, GenericRequirement::Exact(1);
Sub(Op), sym::sub, sub_trait, Target::Trait, GenericRequirement::Exact(1);
Mul(Op), sym::mul, mul_trait, Target::Trait, GenericRequirement::Exact(1);
Div(Op), sym::div, div_trait, Target::Trait, GenericRequirement::Exact(1);
Rem(Op), sym::rem, rem_trait, Target::Trait, GenericRequirement::Exact(1);
Neg(Op), sym::neg, neg_trait, Target::Trait, GenericRequirement::Exact(0);
Not(Op), sym::not, not_trait, Target::Trait, GenericRequirement::Exact(0);
BitXor(Op), sym::bitxor, bitxor_trait, Target::Trait, GenericRequirement::Exact(1);
BitAnd(Op), sym::bitand, bitand_trait, Target::Trait, GenericRequirement::Exact(1);
BitOr(Op), sym::bitor, bitor_trait, Target::Trait, GenericRequirement::Exact(1);
Shl(Op), sym::shl, shl_trait, Target::Trait, GenericRequirement::Exact(1);
Shr(Op), sym::shr, shr_trait, Target::Trait, GenericRequirement::Exact(1);
AddAssign(Op), sym::add_assign, add_assign_trait, Target::Trait, GenericRequirement::Exact(1);
SubAssign(Op), sym::sub_assign, sub_assign_trait, Target::Trait, GenericRequirement::Exact(1);
MulAssign(Op), sym::mul_assign, mul_assign_trait, Target::Trait, GenericRequirement::Exact(1);
DivAssign(Op), sym::div_assign, div_assign_trait, Target::Trait, GenericRequirement::Exact(1);
RemAssign(Op), sym::rem_assign, rem_assign_trait, Target::Trait, GenericRequirement::Exact(1);
BitXorAssign(Op), sym::bitxor_assign, bitxor_assign_trait, Target::Trait, GenericRequirement::Exact(1);
BitAndAssign(Op), sym::bitand_assign, bitand_assign_trait, Target::Trait, GenericRequirement::Exact(1);
BitOrAssign(Op), sym::bitor_assign, bitor_assign_trait, Target::Trait, GenericRequirement::Exact(1);
ShlAssign(Op), sym::shl_assign, shl_assign_trait, Target::Trait, GenericRequirement::Exact(1);
ShrAssign(Op), sym::shr_assign, shr_assign_trait, Target::Trait, GenericRequirement::Exact(1);
Index(Op), sym::index, index_trait, Target::Trait, GenericRequirement::Exact(1);
IndexMut(Op), sym::index_mut, index_mut_trait, Target::Trait, GenericRequirement::Exact(1);
UnsafeCell, sym::unsafe_cell, unsafe_cell_type, Target::Struct, GenericRequirement::None;
VaList, sym::va_list, va_list, Target::Struct, GenericRequirement::None;
Deref, sym::deref, deref_trait, Target::Trait, GenericRequirement::Exact(0);
DerefMut, sym::deref_mut, deref_mut_trait, Target::Trait, GenericRequirement::Exact(0);
DerefTarget, sym::deref_target, deref_target, Target::AssocTy, GenericRequirement::None;
Receiver, sym::receiver, receiver_trait, Target::Trait, GenericRequirement::None;
Fn, kw::Fn, fn_trait, Target::Trait, GenericRequirement::Exact(1);
FnMut, sym::fn_mut, fn_mut_trait, Target::Trait, GenericRequirement::Exact(1);
FnOnce, sym::fn_once, fn_once_trait, Target::Trait, GenericRequirement::Exact(1);
FnOnceOutput, sym::fn_once_output, fn_once_output, Target::AssocTy, GenericRequirement::None;
Future, sym::future_trait, future_trait, Target::Trait, GenericRequirement::Exact(0);
GeneratorState, sym::generator_state, gen_state, Target::Enum, GenericRequirement::None;
Generator, sym::generator, gen_trait, Target::Trait, GenericRequirement::Minimum(1);
Unpin, sym::unpin, unpin_trait, Target::Trait, GenericRequirement::None;
Pin, sym::pin, pin_type, Target::Struct, GenericRequirement::None;
PartialEq, sym::eq, eq_trait, Target::Trait, GenericRequirement::Exact(1);
PartialOrd, sym::partial_ord, partial_ord_trait, Target::Trait, GenericRequirement::Exact(1);
// A number of panic-related lang items. The `panic` item corresponds to divide-by-zero and
// various panic cases with `match`. The `panic_bounds_check` item is for indexing arrays.
//
// The `begin_unwind` lang item has a predefined symbol name and is sort of a "weak lang item"
// in the sense that a crate is not required to have it defined to use it, but a final product
// is required to define it somewhere. Additionally, there are restrictions on crates that use
// a weak lang item, but do not have it defined.
Panic, sym::panic, panic_fn, Target::Fn, GenericRequirement::None;
PanicFmt, sym::panic_fmt, panic_fmt, Target::Fn, GenericRequirement::None;
PanicStr, sym::panic_str, panic_str, Target::Fn, GenericRequirement::None;
ConstPanicFmt, sym::const_panic_fmt, const_panic_fmt, Target::Fn, GenericRequirement::None;
PanicBoundsCheck, sym::panic_bounds_check, panic_bounds_check_fn, Target::Fn, GenericRequirement::None;
PanicInfo, sym::panic_info, panic_info, Target::Struct, GenericRequirement::None;
PanicLocation, sym::panic_location, panic_location, Target::Struct, GenericRequirement::None;
PanicImpl, sym::panic_impl, panic_impl, Target::Fn, GenericRequirement::None;
/// libstd panic entry point. Necessary for const eval to be able to catch it
BeginPanic, sym::begin_panic, begin_panic_fn, Target::Fn, GenericRequirement::None;
BeginPanicFmt, sym::begin_panic_fmt, begin_panic_fmt, Target::Fn, GenericRequirement::None;
ExchangeMalloc, sym::exchange_malloc, exchange_malloc_fn, Target::Fn, GenericRequirement::None;
BoxFree, sym::box_free, box_free_fn, Target::Fn, GenericRequirement::Minimum(1);
DropInPlace, sym::drop_in_place, drop_in_place_fn, Target::Fn, GenericRequirement::Minimum(1);
Oom, sym::oom, oom, Target::Fn, GenericRequirement::None;
AllocLayout, sym::alloc_layout, alloc_layout, Target::Struct, GenericRequirement::None;
Start, sym::start, start_fn, Target::Fn, GenericRequirement::None;
EhPersonality, sym::eh_personality, eh_personality, Target::Fn, GenericRequirement::None;
EhCatchTypeinfo, sym::eh_catch_typeinfo, eh_catch_typeinfo, Target::Static, GenericRequirement::None;
OwnedBox, sym::owned_box, owned_box, Target::Struct, GenericRequirement::Minimum(1);
PhantomData, sym::phantom_data, phantom_data, Target::Struct, GenericRequirement::Exact(1);
ManuallyDrop, sym::manually_drop, manually_drop, Target::Struct, GenericRequirement::None;
MaybeUninit, sym::maybe_uninit, maybe_uninit, Target::Union, GenericRequirement::None;
/// Align offset for stride != 1; must not panic.
AlignOffset, sym::align_offset, align_offset_fn, Target::Fn, GenericRequirement::None;
Termination, sym::termination, termination, Target::Trait, GenericRequirement::None;
Try, sym::Try, try_trait, Target::Trait, GenericRequirement::None;
SliceLen, sym::slice_len_fn, slice_len_fn, Target::Method(MethodKind::Inherent), GenericRequirement::None;
// Language items from AST lowering
TryTraitFromResidual, sym::from_residual, from_residual_fn, Target::Method(MethodKind::Trait { body: false }), GenericRequirement::None;
TryTraitFromOutput, sym::from_output, from_output_fn, Target::Method(MethodKind::Trait { body: false }), GenericRequirement::None;
TryTraitBranch, sym::branch, branch_fn, Target::Method(MethodKind::Trait { body: false }), GenericRequirement::None;
PollReady, sym::Ready, poll_ready_variant, Target::Variant, GenericRequirement::None;
PollPending, sym::Pending, poll_pending_variant, Target::Variant, GenericRequirement::None;
FromGenerator, sym::from_generator, from_generator_fn, Target::Fn, GenericRequirement::None;
GetContext, sym::get_context, get_context_fn, Target::Fn, GenericRequirement::None;
FuturePoll, sym::poll, future_poll_fn, Target::Method(MethodKind::Trait { body: false }), GenericRequirement::None;
FromFrom, sym::from, from_fn, Target::Method(MethodKind::Trait { body: false }), GenericRequirement::None;
OptionSome, sym::Some, option_some_variant, Target::Variant, GenericRequirement::None;
OptionNone, sym::None, option_none_variant, Target::Variant, GenericRequirement::None;
ResultOk, sym::Ok, result_ok_variant, Target::Variant, GenericRequirement::None;
ResultErr, sym::Err, result_err_variant, Target::Variant, GenericRequirement::None;
ControlFlowContinue, sym::Continue, cf_continue_variant, Target::Variant, GenericRequirement::None;
ControlFlowBreak, sym::Break, cf_break_variant, Target::Variant, GenericRequirement::None;
IntoIterIntoIter, sym::into_iter, into_iter_fn, Target::Method(MethodKind::Trait { body: false }), GenericRequirement::None;
IteratorNext, sym::next, next_fn, Target::Method(MethodKind::Trait { body: false}), GenericRequirement::None;
PinNewUnchecked, sym::new_unchecked, new_unchecked_fn, Target::Method(MethodKind::Inherent), GenericRequirement::None;
RangeFrom, sym::RangeFrom, range_from_struct, Target::Struct, GenericRequirement::None;
RangeFull, sym::RangeFull, range_full_struct, Target::Struct, GenericRequirement::None;
RangeInclusiveStruct, sym::RangeInclusive, range_inclusive_struct, Target::Struct, GenericRequirement::None;
RangeInclusiveNew, sym::range_inclusive_new, range_inclusive_new_method, Target::Method(MethodKind::Inherent), GenericRequirement::None;
Range, sym::Range, range_struct, Target::Struct, GenericRequirement::None;
RangeToInclusive, sym::RangeToInclusive, range_to_inclusive_struct, Target::Struct, GenericRequirement::None;
RangeTo, sym::RangeTo, range_to_struct, Target::Struct, GenericRequirement::None;
}
pub enum GenericRequirement {
None,
Minimum(usize),
Exact(usize),
}