| //! Detecting 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. |
| |
| pub use self::LangItem::*; |
| |
| use crate::hir::def_id::DefId; |
| use crate::hir::check_attr::Target; |
| use crate::ty::{self, TyCtxt}; |
| use crate::middle::weak_lang_items; |
| use crate::middle::cstore::ExternCrate; |
| use crate::util::nodemap::FxHashMap; |
| |
| use syntax::ast; |
| use syntax::symbol::{Symbol, sym}; |
| use syntax_pos::Span; |
| use rustc_macros::HashStable; |
| use crate::hir::itemlikevisit::ItemLikeVisitor; |
| use crate::hir; |
| |
| use rustc_error_codes::*; |
| |
| // 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 { |
| ( |
| $( $variant:ident, $name:expr, $method:ident, $target:path; )* |
| ) => { |
| |
| enum_from_u32! { |
| /// A representation of all the valid language items in Rust. |
| #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)] |
| pub enum LangItem { |
| $($variant,)* |
| } |
| } |
| |
| impl LangItem { |
| /// Returns the `name` in `#[lang = "$name"]`. |
| /// For example, `LangItem::EqTraitLangItem`, |
| /// that is `#[lang = "eq"]` would result in `"eq"`. |
| fn name(self) -> &'static str { |
| match self { |
| $( $variant => $name, )* |
| } |
| } |
| } |
| |
| #[derive(HashStable)] |
| pub struct LanguageItems { |
| /// Mappings from lang items to their possibly found `DefId`s. |
| /// The index corresponds to the order in `LangItem`. |
| pub items: Vec<Option<DefId>>, |
| /// Lang items that were not found during collection. |
| pub missing: Vec<LangItem>, |
| } |
| |
| impl LanguageItems { |
| /// Construct an empty collection of lang items and no missing ones. |
| pub fn new() -> Self { |
| fn init_none(_: LangItem) -> Option<DefId> { None } |
| |
| Self { |
| items: vec![$(init_none($variant)),*], |
| missing: Vec::new(), |
| } |
| } |
| |
| /// 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 kind of closure that `id`, which is one of the `Fn*` traits, corresponds to. |
| /// If `id` is not one of the `Fn*` traits, `None` is returned. |
| pub fn fn_trait_kind(&self, id: DefId) -> Option<ty::ClosureKind> { |
| match Some(id) { |
| x if x == self.fn_trait() => Some(ty::ClosureKind::Fn), |
| x if x == self.fn_mut_trait() => Some(ty::ClosureKind::FnMut), |
| x if x == self.fn_once_trait() => Some(ty::ClosureKind::FnOnce), |
| _ => None |
| } |
| } |
| |
| $( |
| /// Returns the corresponding `DefId` for the lang item |
| #[doc = $name] |
| /// if it exists. |
| #[allow(dead_code)] |
| pub fn $method(&self) -> Option<DefId> { |
| self.items[$variant as usize] |
| } |
| )* |
| } |
| |
| struct LanguageItemCollector<'tcx> { |
| items: LanguageItems, |
| tcx: TyCtxt<'tcx>, |
| /// A mapping from the name of the lang item to its order and the form it must be of. |
| item_refs: FxHashMap<&'static str, (usize, Target)>, |
| } |
| |
| impl ItemLikeVisitor<'v> for LanguageItemCollector<'tcx> { |
| fn visit_item(&mut self, item: &hir::Item) { |
| if let Some((value, span)) = extract(&item.attrs) { |
| let actual_target = Target::from_item(item); |
| match self.item_refs.get(&*value.as_str()).cloned() { |
| // Known lang item with attribute on correct target. |
| Some((item_index, expected_target)) if actual_target == expected_target => { |
| let def_id = self.tcx.hir().local_def_id(item.hir_id); |
| self.collect_item(item_index, def_id); |
| }, |
| // Known lang item with attribute on incorrect target. |
| Some((_, expected_target)) => { |
| struct_span_err!( |
| self.tcx.sess, span, E0718, |
| "`{}` language item must be applied to a {}", |
| value, expected_target, |
| ).span_label( |
| span, |
| format!( |
| "attribute should be applied to a {}, not a {}", |
| expected_target, actual_target, |
| ), |
| ).emit(); |
| }, |
| // Unknown lang item. |
| _ => { |
| struct_span_err!( |
| self.tcx.sess, span, E0522, |
| "definition of an unknown language item: `{}`", |
| value |
| ).span_label( |
| span, |
| format!("definition of unknown language item `{}`", value) |
| ).emit(); |
| }, |
| } |
| } |
| } |
| |
| fn visit_trait_item(&mut self, _trait_item: &hir::TraitItem) { |
| // At present, lang items are always items, not trait items. |
| } |
| |
| fn visit_impl_item(&mut self, _impl_item: &hir::ImplItem) { |
| // At present, lang items are always items, not impl items. |
| } |
| } |
| |
| impl LanguageItemCollector<'tcx> { |
| fn new(tcx: TyCtxt<'tcx>) -> LanguageItemCollector<'tcx> { |
| let mut item_refs = FxHashMap::default(); |
| |
| $( item_refs.insert($name, ($variant as usize, $target)); )* |
| |
| LanguageItemCollector { |
| tcx, |
| items: LanguageItems::new(), |
| item_refs, |
| } |
| } |
| |
| fn collect_item(&mut self, item_index: usize, item_def_id: DefId) { |
| // Check for duplicates. |
| if let Some(original_def_id) = self.items.items[item_index] { |
| if original_def_id != item_def_id { |
| let name = LangItem::from_u32(item_index as u32).unwrap().name(); |
| let mut err = match self.tcx.hir().span_if_local(item_def_id) { |
| Some(span) => struct_span_err!( |
| self.tcx.sess, |
| span, |
| E0152, |
| "duplicate lang item found: `{}`.", |
| name), |
| None => { |
| match self.tcx.extern_crate(item_def_id) { |
| Some(ExternCrate {dependency_of, ..}) => { |
| self.tcx.sess.struct_err(&format!( |
| "duplicate lang item in crate `{}` (which `{}` depends on): `{}`.", |
| self.tcx.crate_name(item_def_id.krate), |
| self.tcx.crate_name(*dependency_of), |
| name)) |
| }, |
| _ => { |
| self.tcx.sess.struct_err(&format!( |
| "duplicate lang item in crate `{}`: `{}`.", |
| self.tcx.crate_name(item_def_id.krate), |
| name)) |
| } |
| } |
| }, |
| }; |
| if let Some(span) = self.tcx.hir().span_if_local(original_def_id) { |
| span_note!(&mut err, span, "first defined here."); |
| } else { |
| match self.tcx.extern_crate(original_def_id) { |
| Some(ExternCrate {dependency_of, ..}) => { |
| err.note(&format!( |
| "first defined in crate `{}` (which `{}` depends on).", |
| self.tcx.crate_name(original_def_id.krate), |
| self.tcx.crate_name(*dependency_of))); |
| }, |
| _ => { |
| err.note(&format!("first defined in crate `{}`.", |
| self.tcx.crate_name(original_def_id.krate))); |
| } |
| } |
| } |
| err.emit(); |
| } |
| } |
| |
| // Matched. |
| self.items.items[item_index] = Some(item_def_id); |
| } |
| } |
| |
| /// Extracts the first `lang = "$name"` out of a list of attributes. |
| /// The attributes `#[panic_handler]` and `#[alloc_error_handler]` |
| /// are also extracted out when found. |
| pub fn extract(attrs: &[ast::Attribute]) -> Option<(Symbol, Span)> { |
| attrs.iter().find_map(|attr| Some(match attr { |
| _ if attr.check_name(sym::lang) => (attr.value_str()?, attr.span), |
| _ if attr.check_name(sym::panic_handler) => (sym::panic_impl, attr.span), |
| _ if attr.check_name(sym::alloc_error_handler) => (sym::oom, attr.span), |
| _ => return None, |
| })) |
| } |
| |
| /// Traverses and collects all the lang items in all crates. |
| pub fn collect<'tcx>(tcx: TyCtxt<'tcx>) -> LanguageItems { |
| // Initialize the collector. |
| let mut collector = LanguageItemCollector::new(tcx); |
| |
| // Collect lang items in other crates. |
| for &cnum in tcx.crates().iter() { |
| for &(def_id, item_index) in tcx.defined_lang_items(cnum).iter() { |
| collector.collect_item(item_index, def_id); |
| } |
| } |
| |
| // Collect lang items in this crate. |
| tcx.hir().krate().visit_all_item_likes(&mut collector); |
| |
| // Extract out the found lang items. |
| let LanguageItemCollector { mut items, .. } = collector; |
| |
| // Find all required but not-yet-defined lang items. |
| weak_lang_items::check_crate(tcx, &mut items); |
| |
| items |
| } |
| |
| // End of the macro |
| } |
| } |
| |
| language_item_table! { |
| // Variant name, Name, Method name, Target; |
| BoolImplItem, "bool", bool_impl, Target::Impl; |
| CharImplItem, "char", char_impl, Target::Impl; |
| StrImplItem, "str", str_impl, Target::Impl; |
| SliceImplItem, "slice", slice_impl, Target::Impl; |
| SliceU8ImplItem, "slice_u8", slice_u8_impl, Target::Impl; |
| StrAllocImplItem, "str_alloc", str_alloc_impl, Target::Impl; |
| SliceAllocImplItem, "slice_alloc", slice_alloc_impl, Target::Impl; |
| SliceU8AllocImplItem, "slice_u8_alloc", slice_u8_alloc_impl, Target::Impl; |
| ConstPtrImplItem, "const_ptr", const_ptr_impl, Target::Impl; |
| MutPtrImplItem, "mut_ptr", mut_ptr_impl, Target::Impl; |
| I8ImplItem, "i8", i8_impl, Target::Impl; |
| I16ImplItem, "i16", i16_impl, Target::Impl; |
| I32ImplItem, "i32", i32_impl, Target::Impl; |
| I64ImplItem, "i64", i64_impl, Target::Impl; |
| I128ImplItem, "i128", i128_impl, Target::Impl; |
| IsizeImplItem, "isize", isize_impl, Target::Impl; |
| U8ImplItem, "u8", u8_impl, Target::Impl; |
| U16ImplItem, "u16", u16_impl, Target::Impl; |
| U32ImplItem, "u32", u32_impl, Target::Impl; |
| U64ImplItem, "u64", u64_impl, Target::Impl; |
| U128ImplItem, "u128", u128_impl, Target::Impl; |
| UsizeImplItem, "usize", usize_impl, Target::Impl; |
| F32ImplItem, "f32", f32_impl, Target::Impl; |
| F64ImplItem, "f64", f64_impl, Target::Impl; |
| F32RuntimeImplItem, "f32_runtime", f32_runtime_impl, Target::Impl; |
| F64RuntimeImplItem, "f64_runtime", f64_runtime_impl, Target::Impl; |
| |
| SizedTraitLangItem, "sized", sized_trait, Target::Trait; |
| UnsizeTraitLangItem, "unsize", unsize_trait, Target::Trait; |
| // trait injected by #[derive(PartialEq)], (i.e. "Partial EQ"). |
| StructuralPeqTraitLangItem, "structural_peq", structural_peq_trait, Target::Trait; |
| // trait injected by #[derive(Eq)], (i.e. "Total EQ"; no, I will not apologize). |
| StructuralTeqTraitLangItem, "structural_teq", structural_teq_trait, Target::Trait; |
| CopyTraitLangItem, "copy", copy_trait, Target::Trait; |
| CloneTraitLangItem, "clone", clone_trait, Target::Trait; |
| SyncTraitLangItem, "sync", sync_trait, Target::Trait; |
| FreezeTraitLangItem, "freeze", freeze_trait, Target::Trait; |
| |
| DropTraitLangItem, "drop", drop_trait, Target::Trait; |
| |
| CoerceUnsizedTraitLangItem, "coerce_unsized", coerce_unsized_trait, Target::Trait; |
| DispatchFromDynTraitLangItem,"dispatch_from_dyn", dispatch_from_dyn_trait, Target::Trait; |
| |
| AddTraitLangItem, "add", add_trait, Target::Trait; |
| SubTraitLangItem, "sub", sub_trait, Target::Trait; |
| MulTraitLangItem, "mul", mul_trait, Target::Trait; |
| DivTraitLangItem, "div", div_trait, Target::Trait; |
| RemTraitLangItem, "rem", rem_trait, Target::Trait; |
| NegTraitLangItem, "neg", neg_trait, Target::Trait; |
| NotTraitLangItem, "not", not_trait, Target::Trait; |
| BitXorTraitLangItem, "bitxor", bitxor_trait, Target::Trait; |
| BitAndTraitLangItem, "bitand", bitand_trait, Target::Trait; |
| BitOrTraitLangItem, "bitor", bitor_trait, Target::Trait; |
| ShlTraitLangItem, "shl", shl_trait, Target::Trait; |
| ShrTraitLangItem, "shr", shr_trait, Target::Trait; |
| AddAssignTraitLangItem, "add_assign", add_assign_trait, Target::Trait; |
| SubAssignTraitLangItem, "sub_assign", sub_assign_trait, Target::Trait; |
| MulAssignTraitLangItem, "mul_assign", mul_assign_trait, Target::Trait; |
| DivAssignTraitLangItem, "div_assign", div_assign_trait, Target::Trait; |
| RemAssignTraitLangItem, "rem_assign", rem_assign_trait, Target::Trait; |
| BitXorAssignTraitLangItem, "bitxor_assign", bitxor_assign_trait, Target::Trait; |
| BitAndAssignTraitLangItem, "bitand_assign", bitand_assign_trait, Target::Trait; |
| BitOrAssignTraitLangItem, "bitor_assign", bitor_assign_trait, Target::Trait; |
| ShlAssignTraitLangItem, "shl_assign", shl_assign_trait, Target::Trait; |
| ShrAssignTraitLangItem, "shr_assign", shr_assign_trait, Target::Trait; |
| IndexTraitLangItem, "index", index_trait, Target::Trait; |
| IndexMutTraitLangItem, "index_mut", index_mut_trait, Target::Trait; |
| |
| UnsafeCellTypeLangItem, "unsafe_cell", unsafe_cell_type, Target::Struct; |
| VaListTypeLangItem, "va_list", va_list, Target::Struct; |
| |
| DerefTraitLangItem, "deref", deref_trait, Target::Trait; |
| DerefMutTraitLangItem, "deref_mut", deref_mut_trait, Target::Trait; |
| ReceiverTraitLangItem, "receiver", receiver_trait, Target::Trait; |
| |
| FnTraitLangItem, "fn", fn_trait, Target::Trait; |
| FnMutTraitLangItem, "fn_mut", fn_mut_trait, Target::Trait; |
| FnOnceTraitLangItem, "fn_once", fn_once_trait, Target::Trait; |
| |
| FutureTraitLangItem, "future_trait", future_trait, Target::Trait; |
| GeneratorStateLangItem, "generator_state", gen_state, Target::Enum; |
| GeneratorTraitLangItem, "generator", gen_trait, Target::Trait; |
| UnpinTraitLangItem, "unpin", unpin_trait, Target::Trait; |
| PinTypeLangItem, "pin", pin_type, Target::Struct; |
| |
| // Don't be fooled by the naming here: this lang item denotes `PartialEq`, not `Eq`. |
| EqTraitLangItem, "eq", eq_trait, Target::Trait; |
| PartialOrdTraitLangItem, "partial_ord", partial_ord_trait, Target::Trait; |
| |
| // 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. |
| PanicFnLangItem, "panic", panic_fn, Target::Fn; |
| PanicBoundsCheckFnLangItem, "panic_bounds_check", panic_bounds_check_fn, Target::Fn; |
| PanicInfoLangItem, "panic_info", panic_info, Target::Struct; |
| PanicLocationLangItem, "panic_location", panic_location, Target::Struct; |
| PanicImplLangItem, "panic_impl", panic_impl, Target::Fn; |
| // Libstd panic entry point. Necessary for const eval to be able to catch it |
| BeginPanicFnLangItem, "begin_panic", begin_panic_fn, Target::Fn; |
| |
| ExchangeMallocFnLangItem, "exchange_malloc", exchange_malloc_fn, Target::Fn; |
| BoxFreeFnLangItem, "box_free", box_free_fn, Target::Fn; |
| DropInPlaceFnLangItem, "drop_in_place", drop_in_place_fn, Target::Fn; |
| OomLangItem, "oom", oom, Target::Fn; |
| AllocLayoutLangItem, "alloc_layout", alloc_layout, Target::Struct; |
| |
| StartFnLangItem, "start", start_fn, Target::Fn; |
| |
| EhPersonalityLangItem, "eh_personality", eh_personality, Target::Fn; |
| EhUnwindResumeLangItem, "eh_unwind_resume", eh_unwind_resume, Target::Fn; |
| EhCatchTypeinfoLangItem, "eh_catch_typeinfo", eh_catch_typeinfo, Target::Static; |
| |
| OwnedBoxLangItem, "owned_box", owned_box, Target::Struct; |
| |
| PhantomDataItem, "phantom_data", phantom_data, Target::Struct; |
| |
| ManuallyDropItem, "manually_drop", manually_drop, Target::Struct; |
| |
| MaybeUninitLangItem, "maybe_uninit", maybe_uninit, Target::Union; |
| |
| // Align offset for stride != 1; must not panic. |
| AlignOffsetLangItem, "align_offset", align_offset_fn, Target::Fn; |
| |
| TerminationTraitLangItem, "termination", termination, Target::Trait; |
| |
| Arc, "arc", arc, Target::Struct; |
| Rc, "rc", rc, Target::Struct; |
| } |
| |
| impl<'tcx> TyCtxt<'tcx> { |
| /// Returns the `DefId` for a given `LangItem`. |
| /// If not found, fatally aborts compilation. |
| pub fn require_lang_item(&self, lang_item: LangItem, span: Option<Span>) -> DefId { |
| self.lang_items().require(lang_item).unwrap_or_else(|msg| { |
| if let Some(span) = span { |
| self.sess.span_fatal(span, &msg) |
| } else { |
| self.sess.fatal(&msg) |
| } |
| }) |
| } |
| } |
