src/librustc/middle/lang_items.rs

   1 // Detecting 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 //
   8 // * Traits that represent operators; e.g., "Add", "Sub", "Index".
   9 //
  10 // * Functions called by the compiler itself.
  11
  12 pub use self::LangItem::*;
  13
  14 use crate::hir::def_id::DefId;
  15 use crate::hir::check_attr::Target;
  16 use crate::ty::{self, TyCtxt};
  17 use crate::middle::weak_lang_items;
  18 use crate::util::nodemap::FxHashMap;
  19
  20 use syntax::ast;
  21 use syntax::symbol::Symbol;
  22 use syntax_pos::Span;
  23 use crate::hir::itemlikevisit::ItemLikeVisitor;
  24 use crate::hir;
  25
  26 // The actual lang items defined come at the end of this file in one handy table.
  27 // So you probably just want to nip down to the end.
  28 macro_rules! language_item_table {
  29     (
  30         $( $variant:ident, $name:expr, $method:ident, $target:path; )*
  31     ) => {
  32
  33 enum_from_u32! {
  34     #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
  35     pub enum LangItem {
  36         $($variant,)*
  37     }
  38 }
  39
  40 impl LangItem {
  41     fn name(self) -> &'static str {
  42         match self {
  43             $( $variant => $name, )*
  44         }
  45     }
  46 }
  47
  48 pub struct LanguageItems {
  49     pub items: Vec<Option<DefId>>,
  50     pub missing: Vec<LangItem>,
  51 }
  52
  53 impl LanguageItems {
  54     pub fn new() -> LanguageItems {
  55         fn foo(_: LangItem) -> Option<DefId> { None }
  56
  57         LanguageItems {
  58             items: vec![$(foo($variant)),*],
  59             missing: Vec::new(),
  60         }
  61     }
  62
  63     pub fn items(&self) -> &[Option<DefId>] {
  64         &*self.items
  65     }
  66
  67     pub fn require(&self, it: LangItem) -> Result<DefId, String> {
  68         self.items[it as usize].ok_or_else(|| format!("requires `{}` lang_item", it.name()))
  69     }
  70
  71     pub fn fn_trait_kind(&self, id: DefId) -> Option<ty::ClosureKind> {
  72         match Some(id) {
  73             x if x == self.fn_trait() => Some(ty::ClosureKind::Fn),
  74             x if x == self.fn_mut_trait() => Some(ty::ClosureKind::FnMut),
  75             x if x == self.fn_once_trait() => Some(ty::ClosureKind::FnOnce),
  76             _ => None
  77         }
  78     }
  79
  80     $(
  81         #[allow(dead_code)]
  82         pub fn $method(&self) -> Option<DefId> {
  83             self.items[$variant as usize]
  84         }
  85     )*
  86 }
  87
  88 struct LanguageItemCollector<'a, 'tcx: 'a> {
  89     items: LanguageItems,
  90     tcx: TyCtxt<'a, 'tcx, 'tcx>,
  91     item_refs: FxHashMap<&'static str, (usize, Target)>,
  92 }
  93
  94 impl<'a, 'v, 'tcx> ItemLikeVisitor<'v> for LanguageItemCollector<'a, 'tcx> {
  95     fn visit_item(&mut self, item: &hir::Item) {
  96         if let Some((value, span)) = extract(&item.attrs) {
  97             let actual_target = Target::from_item(item);
  98             match self.item_refs.get(&*value.as_str()).cloned() {
  99                 // Known lang item with attribute on correct target.
 100                 Some((item_index, expected_target)) if actual_target == expected_target => {
 101                     let def_id = self.tcx.hir().local_def_id(item.id);
 102                     self.collect_item(item_index, def_id);
 103                 },
 104                 // Known lang item with attribute on incorrect target.
 105                 Some((_, expected_target)) => {
 106                     let mut err = struct_span_err!(
 107                         self.tcx.sess, span, E0718,
 108                         "`{}` language item must be applied to a {}",
 109                         value, expected_target,
 110                     );
 111                     err.span_label(
 112                         span,
 113                         format!(
 114                             "attribute should be applied to a {}, not a {}",
 115                             expected_target, actual_target,
 116                         ),
 117                     );
 118                     err.emit();
 119                 },
 120                 // Unknown lang item.
 121                 _ => {
 122                     let mut err = struct_span_err!(
 123                         self.tcx.sess, span, E0522,
 124                         "definition of an unknown language item: `{}`",
 125                         value
 126                     );
 127                     err.span_label(
 128                         span,
 129                         format!("definition of unknown language item `{}`", value)
 130                     );
 131                     err.emit();
 132                 },
 133             }
 134         }
 135     }
 136
 137     fn visit_trait_item(&mut self, _trait_item: &hir::TraitItem) {
 138         // at present, lang items are always items, not trait items
 139     }
 140
 141     fn visit_impl_item(&mut self, _impl_item: &hir::ImplItem) {
 142         // at present, lang items are always items, not impl items
 143     }
 144 }
 145
 146 impl<'a, 'tcx> LanguageItemCollector<'a, 'tcx> {
 147     fn new(tcx: TyCtxt<'a, 'tcx, 'tcx>) -> LanguageItemCollector<'a, 'tcx> {
 148         let mut item_refs = FxHashMap::default();
 149
 150         $( item_refs.insert($name, ($variant as usize, $target)); )*
 151
 152         LanguageItemCollector {
 153             tcx,
 154             items: LanguageItems::new(),
 155             item_refs,
 156         }
 157     }
 158
 159     fn collect_item(&mut self, item_index: usize, item_def_id: DefId) {
 160         // Check for duplicates.
 161         if let Some(original_def_id) = self.items.items[item_index] {
 162             if original_def_id != item_def_id {
 163                 let name = LangItem::from_u32(item_index as u32).unwrap().name();
 164                 let mut err = match self.tcx.hir().span_if_local(item_def_id) {
 165                     Some(span) => struct_span_err!(
 166                         self.tcx.sess,
 167                         span,
 168                         E0152,
 169                         "duplicate lang item found: `{}`.",
 170                         name),
 171                     None => self.tcx.sess.struct_err(&format!(
 172                             "duplicate lang item in crate `{}`: `{}`.",
 173                             self.tcx.crate_name(item_def_id.krate),
 174                             name)),
 175                 };
 176                 if let Some(span) = self.tcx.hir().span_if_local(original_def_id) {
 177                     span_note!(&mut err, span, "first defined here.");
 178                 } else {
 179                     err.note(&format!("first defined in crate `{}`.",
 180                                       self.tcx.crate_name(original_def_id.krate)));
 181                 }
 182                 err.emit();
 183             }
 184         }
 185
 186         // Matched.
 187         self.items.items[item_index] = Some(item_def_id);
 188     }
 189 }
 190
 191 pub fn extract(attrs: &[ast::Attribute]) -> Option<(Symbol, Span)> {
 192     for attribute in attrs {
 193         if attribute.check_name("lang") {
 194             if let Some(value) = attribute.value_str() {
 195                 return Some((value, attribute.span));
 196             }
 197         } else if attribute.check_name("panic_handler") {
 198             return Some((Symbol::intern("panic_impl"), attribute.span))
 199         } else if attribute.check_name("alloc_error_handler") {
 200             return Some((Symbol::intern("oom"), attribute.span))
 201         }
 202     }
 203
 204     None
 205 }
 206
 207 pub fn collect<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) -> LanguageItems {
 208     let mut collector = LanguageItemCollector::new(tcx);
 209     for &cnum in tcx.crates().iter() {
 210         for &(def_id, item_index) in tcx.defined_lang_items(cnum).iter() {
 211             collector.collect_item(item_index, def_id);
 212         }
 213     }
 214     tcx.hir().krate().visit_all_item_likes(&mut collector);
 215     let LanguageItemCollector { mut items, .. } = collector;
 216     weak_lang_items::check_crate(tcx, &mut items);
 217     items
 218 }
 219
 220 // End of the macro
 221     }
 222 }
 223
 224 language_item_table! {
 225 //  Variant name,                Name,                 Method name,             Target;
 226     CharImplItem,                "char",               char_impl,               Target::Impl;
 227     StrImplItem,                 "str",                str_impl,                Target::Impl;
 228     SliceImplItem,               "slice",              slice_impl,              Target::Impl;
 229     SliceU8ImplItem,             "slice_u8",           slice_u8_impl,           Target::Impl;
 230     StrAllocImplItem,            "str_alloc",          str_alloc_impl,          Target::Impl;
 231     SliceAllocImplItem,          "slice_alloc",        slice_alloc_impl,        Target::Impl;
 232     SliceU8AllocImplItem,        "slice_u8_alloc",     slice_u8_alloc_impl,     Target::Impl;
 233     ConstPtrImplItem,            "const_ptr",          const_ptr_impl,          Target::Impl;
 234     MutPtrImplItem,              "mut_ptr",            mut_ptr_impl,            Target::Impl;
 235     I8ImplItem,                  "i8",                 i8_impl,                 Target::Impl;
 236     I16ImplItem,                 "i16",                i16_impl,                Target::Impl;
 237     I32ImplItem,                 "i32",                i32_impl,                Target::Impl;
 238     I64ImplItem,                 "i64",                i64_impl,                Target::Impl;
 239     I128ImplItem,                "i128",               i128_impl,               Target::Impl;
 240     IsizeImplItem,               "isize",              isize_impl,              Target::Impl;
 241     U8ImplItem,                  "u8",                 u8_impl,                 Target::Impl;
 242     U16ImplItem,                 "u16",                u16_impl,                Target::Impl;
 243     U32ImplItem,                 "u32",                u32_impl,                Target::Impl;
 244     U64ImplItem,                 "u64",                u64_impl,                Target::Impl;
 245     U128ImplItem,                "u128",               u128_impl,               Target::Impl;
 246     UsizeImplItem,               "usize",              usize_impl,              Target::Impl;
 247     F32ImplItem,                 "f32",                f32_impl,                Target::Impl;
 248     F64ImplItem,                 "f64",                f64_impl,                Target::Impl;
 249     F32RuntimeImplItem,          "f32_runtime",        f32_runtime_impl,        Target::Impl;
 250     F64RuntimeImplItem,          "f64_runtime",        f64_runtime_impl,        Target::Impl;
 251
 252     SizedTraitLangItem,          "sized",              sized_trait,             Target::Trait;
 253     UnsizeTraitLangItem,         "unsize",             unsize_trait,            Target::Trait;
 254     CopyTraitLangItem,           "copy",               copy_trait,              Target::Trait;
 255     CloneTraitLangItem,          "clone",              clone_trait,             Target::Trait;
 256     SyncTraitLangItem,           "sync",               sync_trait,              Target::Trait;
 257     FreezeTraitLangItem,         "freeze",             freeze_trait,            Target::Trait;
 258
 259     DropTraitLangItem,           "drop",               drop_trait,              Target::Trait;
 260
 261     CoerceUnsizedTraitLangItem,  "coerce_unsized",     coerce_unsized_trait,    Target::Trait;
 262     DispatchFromDynTraitLangItem,"dispatch_from_dyn",  dispatch_from_dyn_trait, Target::Trait;
 263
 264     AddTraitLangItem,            "add",                add_trait,               Target::Trait;
 265     SubTraitLangItem,            "sub",                sub_trait,               Target::Trait;
 266     MulTraitLangItem,            "mul",                mul_trait,               Target::Trait;
 267     DivTraitLangItem,            "div",                div_trait,               Target::Trait;
 268     RemTraitLangItem,            "rem",                rem_trait,               Target::Trait;
 269     NegTraitLangItem,            "neg",                neg_trait,               Target::Trait;
 270     NotTraitLangItem,            "not",                not_trait,               Target::Trait;
 271     BitXorTraitLangItem,         "bitxor",             bitxor_trait,            Target::Trait;
 272     BitAndTraitLangItem,         "bitand",             bitand_trait,            Target::Trait;
 273     BitOrTraitLangItem,          "bitor",              bitor_trait,             Target::Trait;
 274     ShlTraitLangItem,            "shl",                shl_trait,               Target::Trait;
 275     ShrTraitLangItem,            "shr",                shr_trait,               Target::Trait;
 276     AddAssignTraitLangItem,      "add_assign",         add_assign_trait,        Target::Trait;
 277     SubAssignTraitLangItem,      "sub_assign",         sub_assign_trait,        Target::Trait;
 278     MulAssignTraitLangItem,      "mul_assign",         mul_assign_trait,        Target::Trait;
 279     DivAssignTraitLangItem,      "div_assign",         div_assign_trait,        Target::Trait;
 280     RemAssignTraitLangItem,      "rem_assign",         rem_assign_trait,        Target::Trait;
 281     BitXorAssignTraitLangItem,   "bitxor_assign",      bitxor_assign_trait,     Target::Trait;
 282     BitAndAssignTraitLangItem,   "bitand_assign",      bitand_assign_trait,     Target::Trait;
 283     BitOrAssignTraitLangItem,    "bitor_assign",       bitor_assign_trait,      Target::Trait;
 284     ShlAssignTraitLangItem,      "shl_assign",         shl_assign_trait,        Target::Trait;
 285     ShrAssignTraitLangItem,      "shr_assign",         shr_assign_trait,        Target::Trait;
 286     IndexTraitLangItem,          "index",              index_trait,             Target::Trait;
 287     IndexMutTraitLangItem,       "index_mut",          index_mut_trait,         Target::Trait;
 288
 289     UnsafeCellTypeLangItem,      "unsafe_cell",        unsafe_cell_type,        Target::Struct;
 290     VaListTypeLangItem,          "va_list",            va_list,                 Target::Struct;
 291
 292     DerefTraitLangItem,          "deref",              deref_trait,             Target::Trait;
 293     DerefMutTraitLangItem,       "deref_mut",          deref_mut_trait,         Target::Trait;
 294     ReceiverTraitLangItem,       "receiver",           receiver_trait,          Target::Trait;
 295
 296     FnTraitLangItem,             "fn",                 fn_trait,                Target::Trait;
 297     FnMutTraitLangItem,          "fn_mut",             fn_mut_trait,            Target::Trait;
 298     FnOnceTraitLangItem,         "fn_once",            fn_once_trait,           Target::Trait;
 299
 300     GeneratorStateLangItem,      "generator_state",    gen_state,               Target::Enum;
 301     GeneratorTraitLangItem,      "generator",          gen_trait,               Target::Trait;
 302     UnpinTraitLangItem,          "unpin",              unpin_trait,             Target::Trait;
 303     PinTypeLangItem,             "pin",                pin_type,                Target::Struct;
 304
 305     EqTraitLangItem,             "eq",                 eq_trait,                Target::Trait;
 306     PartialOrdTraitLangItem,     "partial_ord",        partial_ord_trait,       Target::Trait;
 307     OrdTraitLangItem,            "ord",                ord_trait,               Target::Trait;
 308
 309     // A number of panic-related lang items. The `panic` item corresponds to
 310     // divide-by-zero and various panic cases with `match`. The
 311     // `panic_bounds_check` item is for indexing arrays.
 312     //
 313     // The `begin_unwind` lang item has a predefined symbol name and is sort of
 314     // a "weak lang item" in the sense that a crate is not required to have it
 315     // defined to use it, but a final product is required to define it
 316     // somewhere. Additionally, there are restrictions on crates that use a weak
 317     // lang item, but do not have it defined.
 318     PanicFnLangItem,             "panic",              panic_fn,                Target::Fn;
 319     PanicBoundsCheckFnLangItem,  "panic_bounds_check", panic_bounds_check_fn,   Target::Fn;
 320     PanicInfoLangItem,           "panic_info",         panic_info,              Target::Struct;
 321     PanicImplLangItem,           "panic_impl",         panic_impl,              Target::Fn;
 322     // Libstd panic entry point. Necessary for const eval to be able to catch it
 323     BeginPanicFnLangItem,        "begin_panic",        begin_panic_fn,          Target::Fn;
 324
 325     ExchangeMallocFnLangItem,    "exchange_malloc",    exchange_malloc_fn,      Target::Fn;
 326     BoxFreeFnLangItem,           "box_free",           box_free_fn,             Target::Fn;
 327     DropInPlaceFnLangItem,       "drop_in_place",      drop_in_place_fn,        Target::Fn;
 328     OomLangItem,                 "oom",                oom,                     Target::Fn;
 329     AllocLayoutLangItem,         "alloc_layout",       alloc_layout,            Target::Struct;
 330
 331     StartFnLangItem,             "start",              start_fn,                Target::Fn;
 332
 333     EhPersonalityLangItem,       "eh_personality",     eh_personality,          Target::Fn;
 334     EhUnwindResumeLangItem,      "eh_unwind_resume",   eh_unwind_resume,        Target::Fn;
 335     MSVCTryFilterLangItem,       "msvc_try_filter",    msvc_try_filter,         Target::Static;
 336
 337     OwnedBoxLangItem,            "owned_box",          owned_box,               Target::Struct;
 338
 339     PhantomDataItem,             "phantom_data",       phantom_data,            Target::Struct;
 340
 341     ManuallyDropItem,            "manually_drop",      manually_drop,           Target::Struct;
 342
 343     DebugTraitLangItem,          "debug_trait",        debug_trait,             Target::Trait;
 344
 345     // A lang item for each of the 128-bit operators we can optionally lower.
 346     I128AddFnLangItem,           "i128_add",           i128_add_fn,             Target::Fn;
 347     U128AddFnLangItem,           "u128_add",           u128_add_fn,             Target::Fn;
 348     I128SubFnLangItem,           "i128_sub",           i128_sub_fn,             Target::Fn;
 349     U128SubFnLangItem,           "u128_sub",           u128_sub_fn,             Target::Fn;
 350     I128MulFnLangItem,           "i128_mul",           i128_mul_fn,             Target::Fn;
 351     U128MulFnLangItem,           "u128_mul",           u128_mul_fn,             Target::Fn;
 352     I128DivFnLangItem,           "i128_div",           i128_div_fn,             Target::Fn;
 353     U128DivFnLangItem,           "u128_div",           u128_div_fn,             Target::Fn;
 354     I128RemFnLangItem,           "i128_rem",           i128_rem_fn,             Target::Fn;
 355     U128RemFnLangItem,           "u128_rem",           u128_rem_fn,             Target::Fn;
 356     I128ShlFnLangItem,           "i128_shl",           i128_shl_fn,             Target::Fn;
 357     U128ShlFnLangItem,           "u128_shl",           u128_shl_fn,             Target::Fn;
 358     I128ShrFnLangItem,           "i128_shr",           i128_shr_fn,             Target::Fn;
 359     U128ShrFnLangItem,           "u128_shr",           u128_shr_fn,             Target::Fn;
 360     // And overflow versions for the operators that are checkable.
 361     // While MIR calls these Checked*, they return (T,bool), not Option<T>.
 362     I128AddoFnLangItem,          "i128_addo",          i128_addo_fn,            Target::Fn;
 363     U128AddoFnLangItem,          "u128_addo",          u128_addo_fn,            Target::Fn;
 364     I128SuboFnLangItem,          "i128_subo",          i128_subo_fn,            Target::Fn;
 365     U128SuboFnLangItem,          "u128_subo",          u128_subo_fn,            Target::Fn;
 366     I128MuloFnLangItem,          "i128_mulo",          i128_mulo_fn,            Target::Fn;
 367     U128MuloFnLangItem,          "u128_mulo",          u128_mulo_fn,            Target::Fn;
 368     I128ShloFnLangItem,          "i128_shlo",          i128_shlo_fn,            Target::Fn;
 369     U128ShloFnLangItem,          "u128_shlo",          u128_shlo_fn,            Target::Fn;
 370     I128ShroFnLangItem,          "i128_shro",          i128_shro_fn,            Target::Fn;
 371     U128ShroFnLangItem,          "u128_shro",          u128_shro_fn,            Target::Fn;
 372
 373     // Align offset for stride != 1, must not panic.
 374     AlignOffsetLangItem,         "align_offset",       align_offset_fn,         Target::Fn;
 375
 376     TerminationTraitLangItem,    "termination",        termination,             Target::Trait;
 377
 378     Arc,                         "arc",                arc,                     Target::Struct;
 379     Rc,                          "rc",                 rc,                      Target::Struct;
 380 }
 381
 382 impl<'a, 'tcx, 'gcx> TyCtxt<'a, 'tcx, 'gcx> {
 383     pub fn require_lang_item(&self, lang_item: LangItem) -> DefId {
 384         self.lang_items().require(lang_item).unwrap_or_else(|msg| {
 385             self.sess.fatal(&msg)
 386         })
 387     }
 388 }