// 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::util::nodemap::FxHashMap; use syntax::ast; use syntax::symbol::Symbol; use syntax_pos::Span; use rustc_macros::HashStable; use crate::hir::itemlikevisit::ItemLikeVisitor; use crate::hir; // 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! { #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)] pub enum LangItem { $($variant,)* } } impl LangItem { fn name(self) -> &'static str { match self { $( $variant => $name, )* } } } #[derive(HashStable)] pub struct LanguageItems { pub items: Vec>, pub missing: Vec, } impl LanguageItems { pub fn new() -> LanguageItems { fn foo(_: LangItem) -> Option { None } LanguageItems { items: vec![$(foo($variant)),*], missing: Vec::new(), } } pub fn items(&self) -> &[Option] { &*self.items } pub fn require(&self, it: LangItem) -> Result { self.items[it as usize].ok_or_else(|| format!("requires `{}` lang_item", it.name())) } pub fn fn_trait_kind(&self, id: DefId) -> Option { 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 } } $( #[allow(dead_code)] pub fn $method(&self) -> Option { self.items[$variant as usize] } )* } struct LanguageItemCollector<'a, 'tcx: 'a> { items: LanguageItems, tcx: TyCtxt<'a, 'tcx, 'tcx>, item_refs: FxHashMap<&'static str, (usize, Target)>, } impl<'a, 'v, 'tcx> ItemLikeVisitor<'v> for LanguageItemCollector<'a, '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_from_hir_id(item.hir_id); self.collect_item(item_index, def_id); }, // Known lang item with attribute on incorrect target. Some((_, expected_target)) => { let mut err = struct_span_err!( self.tcx.sess, span, E0718, "`{}` language item must be applied to a {}", value, expected_target, ); err.span_label( span, format!( "attribute should be applied to a {}, not a {}", expected_target, actual_target, ), ); err.emit(); }, // Unknown lang item. _ => { let mut err = struct_span_err!( self.tcx.sess, span, E0522, "definition of an unknown language item: `{}`", value ); err.span_label( span, format!("definition of unknown language item `{}`", value) ); err.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<'a, 'tcx> LanguageItemCollector<'a, 'tcx> { fn new(tcx: TyCtxt<'a, 'tcx, 'tcx>) -> LanguageItemCollector<'a, '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 => 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 { 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); } } pub fn extract(attrs: &[ast::Attribute]) -> Option<(Symbol, Span)> { for attribute in attrs { if attribute.check_name("lang") { if let Some(value) = attribute.value_str() { return Some((value, attribute.span)); } } else if attribute.check_name("panic_handler") { return Some((Symbol::intern("panic_impl"), attribute.span)) } else if attribute.check_name("alloc_error_handler") { return Some((Symbol::intern("oom"), attribute.span)) } } None } pub fn collect<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) -> LanguageItems { let mut collector = LanguageItemCollector::new(tcx); 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); } } tcx.hir().krate().visit_all_item_likes(&mut collector); let LanguageItemCollector { mut items, .. } = collector; weak_lang_items::check_crate(tcx, &mut items); items } // End of the macro } } language_item_table! { // Variant name, Name, Method name, Target; 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; 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; 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; EqTraitLangItem, "eq", eq_trait, Target::Trait; PartialOrdTraitLangItem, "partial_ord", partial_ord_trait, Target::Trait; OrdTraitLangItem, "ord", 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; 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; MSVCTryFilterLangItem, "msvc_try_filter", msvc_try_filter, Target::Static; OwnedBoxLangItem, "owned_box", owned_box, Target::Struct; PhantomDataItem, "phantom_data", phantom_data, Target::Struct; ManuallyDropItem, "manually_drop", manually_drop, Target::Struct; DebugTraitLangItem, "debug_trait", debug_trait, Target::Trait; // A lang item for each of the 128-bit operators we can optionally lower. I128AddFnLangItem, "i128_add", i128_add_fn, Target::Fn; U128AddFnLangItem, "u128_add", u128_add_fn, Target::Fn; I128SubFnLangItem, "i128_sub", i128_sub_fn, Target::Fn; U128SubFnLangItem, "u128_sub", u128_sub_fn, Target::Fn; I128MulFnLangItem, "i128_mul", i128_mul_fn, Target::Fn; U128MulFnLangItem, "u128_mul", u128_mul_fn, Target::Fn; I128DivFnLangItem, "i128_div", i128_div_fn, Target::Fn; U128DivFnLangItem, "u128_div", u128_div_fn, Target::Fn; I128RemFnLangItem, "i128_rem", i128_rem_fn, Target::Fn; U128RemFnLangItem, "u128_rem", u128_rem_fn, Target::Fn; I128ShlFnLangItem, "i128_shl", i128_shl_fn, Target::Fn; U128ShlFnLangItem, "u128_shl", u128_shl_fn, Target::Fn; I128ShrFnLangItem, "i128_shr", i128_shr_fn, Target::Fn; U128ShrFnLangItem, "u128_shr", u128_shr_fn, Target::Fn; // And overflow versions for the operators that are checkable. // While MIR calls these Checked*, they return (T,bool), not Option. I128AddoFnLangItem, "i128_addo", i128_addo_fn, Target::Fn; U128AddoFnLangItem, "u128_addo", u128_addo_fn, Target::Fn; I128SuboFnLangItem, "i128_subo", i128_subo_fn, Target::Fn; U128SuboFnLangItem, "u128_subo", u128_subo_fn, Target::Fn; I128MuloFnLangItem, "i128_mulo", i128_mulo_fn, Target::Fn; U128MuloFnLangItem, "u128_mulo", u128_mulo_fn, Target::Fn; I128ShloFnLangItem, "i128_shlo", i128_shlo_fn, Target::Fn; U128ShloFnLangItem, "u128_shlo", u128_shlo_fn, Target::Fn; I128ShroFnLangItem, "i128_shro", i128_shro_fn, Target::Fn; U128ShroFnLangItem, "u128_shro", u128_shro_fn, Target::Fn; // 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<'a, 'tcx, 'gcx> TyCtxt<'a, 'tcx, 'gcx> { pub fn require_lang_item(&self, lang_item: LangItem) -> DefId { self.lang_items().require(lang_item).unwrap_or_else(|msg| { self.sess.fatal(&msg) }) } }