src/librustc/middle/lang_items.rs

   1 // Copyright 2012 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 // Detecting language items.
  12 //
  13 // Language items are items that represent concepts intrinsic to the language
  14 // itself. Examples are:
  15 //
  16 // * Traits that specify "kinds"; e.g., "Sync", "Send".
  17 //
  18 // * Traits that represent operators; e.g., "Add", "Sub", "Index".
  19 //
  20 // * Functions called by the compiler itself.
  21
  22 pub use self::LangItem::*;
  23
  24 use hir::def_id::DefId;
  25 use hir::check_attr::Target;
  26 use ty::{self, TyCtxt};
  27 use middle::weak_lang_items;
  28 use util::nodemap::FxHashMap;
  29
  30 use syntax::ast;
  31 use syntax::symbol::Symbol;
  32 use syntax_pos::Span;
  33 use hir::itemlikevisit::ItemLikeVisitor;
  34 use hir;
  35
  36 // The actual lang items defined come at the end of this file in one handy table.
  37 // So you probably just want to nip down to the end.
  38 macro_rules! language_item_table {
  39     (
  40         $( $variant:ident, $name:expr, $method:ident, $target:path; )*
  41     ) => {
  42
  43 enum_from_u32! {
  44     #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
  45     pub enum LangItem {
  46         $($variant,)*
  47     }
  48 }
  49
  50 impl LangItem {
  51     fn name(self) -> &'static str {
  52         match self {
  53             $( $variant => $name, )*
  54         }
  55     }
  56 }
  57
  58 pub struct LanguageItems {
  59     pub items: Vec<Option<DefId>>,
  60     pub missing: Vec<LangItem>,
  61 }
  62
  63 impl LanguageItems {
  64     pub fn new() -> LanguageItems {
  65         fn foo(_: LangItem) -> Option<DefId> { None }
  66
  67         LanguageItems {
  68             items: vec![$(foo($variant)),*],
  69             missing: Vec::new(),
  70         }
  71     }
  72
  73     pub fn items(&self) -> &[Option<DefId>] {
  74         &*self.items
  75     }
  76
  77     pub fn require(&self, it: LangItem) -> Result<DefId, String> {
  78         self.items[it as usize].ok_or_else(|| format!("requires `{}` lang_item", it.name()))
  79     }
  80
  81     pub fn fn_trait_kind(&self, id: DefId) -> Option<ty::ClosureKind> {
  82         match Some(id) {
  83             x if x == self.fn_trait() => Some(ty::ClosureKind::Fn),
  84             x if x == self.fn_mut_trait() => Some(ty::ClosureKind::FnMut),
  85             x if x == self.fn_once_trait() => Some(ty::ClosureKind::FnOnce),
  86             _ => None
  87         }
  88     }
  89
  90     $(
  91         #[allow(dead_code)]
  92         pub fn $method(&self) -> Option<DefId> {
  93             self.items[$variant as usize]
  94         }
  95     )*
  96 }
  97
  98 struct LanguageItemCollector<'a, 'tcx: 'a> {
  99     items: LanguageItems,
 100     tcx: TyCtxt<'a, 'tcx, 'tcx>,
 101     item_refs: FxHashMap<&'static str, (usize, Target)>,
 102 }
 103
 104 impl<'a, 'v, 'tcx> ItemLikeVisitor<'v> for LanguageItemCollector<'a, 'tcx> {
 105     fn visit_item(&mut self, item: &hir::Item) {
 106         if let Some((value, span)) = extract(&item.attrs) {
 107             let actual_target = Target::from_item(item);
 108             match self.item_refs.get(&*value.as_str()).cloned() {
 109                 // Known lang item with attribute on correct target.
 110                 Some((item_index, expected_target)) if actual_target == expected_target => {
 111                     let def_id = self.tcx.hir().local_def_id(item.id);
 112                     self.collect_item(item_index, def_id);
 113                 },
 114                 // Known lang item with attribute on incorrect target.
 115                 Some((_, expected_target)) => {
 116                     let mut err = struct_span_err!(
 117                         self.tcx.sess, span, E0718,
 118                         "`{}` language item must be applied to a {}",
 119                         value, expected_target,
 120                     );
 121                     err.span_label(
 122                         span,
 123                         format!(
 124                             "attribute should be applied to a {}, not a {}",
 125                             expected_target, actual_target,
 126                         ),
 127                     );
 128                     err.emit();
 129                 },
 130                 // Unknown lang item.
 131                 _ => {
 132                     let mut err = struct_span_err!(
 133                         self.tcx.sess, span, E0522,
 134                         "definition of an unknown language item: `{}`",
 135                         value
 136                     );
 137                     err.span_label(
 138                         span,
 139                         format!("definition of unknown language item `{}`", value)
 140                     );
 141                     err.emit();
 142                 },
 143             }
 144         }
 145     }
 146
 147     fn visit_trait_item(&mut self, _trait_item: &hir::TraitItem) {
 148         // at present, lang items are always items, not trait items
 149     }
 150
 151     fn visit_impl_item(&mut self, _impl_item: &hir::ImplItem) {
 152         // at present, lang items are always items, not impl items
 153     }
 154 }
 155
 156 impl<'a, 'tcx> LanguageItemCollector<'a, 'tcx> {
 157     fn new(tcx: TyCtxt<'a, 'tcx, 'tcx>) -> LanguageItemCollector<'a, 'tcx> {
 158         let mut item_refs = FxHashMap::default();
 159
 160         $( item_refs.insert($name, ($variant as usize, $target)); )*
 161
 162         LanguageItemCollector {
 163             tcx,
 164             items: LanguageItems::new(),
 165             item_refs,
 166         }
 167     }
 168
 169     fn collect_item(&mut self, item_index: usize, item_def_id: DefId) {
 170         // Check for duplicates.
 171         if let Some(original_def_id) = self.items.items[item_index] {
 172             if original_def_id != item_def_id {
 173                 let name = LangItem::from_u32(item_index as u32).unwrap().name();
 174                 let mut err = match self.tcx.hir().span_if_local(item_def_id) {
 175                     Some(span) => struct_span_err!(
 176                         self.tcx.sess,
 177                         span,
 178                         E0152,
 179                         "duplicate lang item found: `{}`.",
 180                         name),
 181                     None => self.tcx.sess.struct_err(&format!(
 182                             "duplicate lang item in crate `{}`: `{}`.",
 183                             self.tcx.crate_name(item_def_id.krate),
 184                             name)),
 185                 };
 186                 if let Some(span) = self.tcx.hir().span_if_local(original_def_id) {
 187                     span_note!(&mut err, span, "first defined here.");
 188                 } else {
 189                     err.note(&format!("first defined in crate `{}`.",
 190                                       self.tcx.crate_name(original_def_id.krate)));
 191                 }
 192                 err.emit();
 193             }
 194         }
 195
 196         // Matched.
 197         self.items.items[item_index] = Some(item_def_id);
 198     }
 199 }
 200
 201 pub fn extract(attrs: &[ast::Attribute]) -> Option<(Symbol, Span)> {
 202     for attribute in attrs {
 203         if attribute.check_name("lang") {
 204             if let Some(value) = attribute.value_str() {
 205                 return Some((value, attribute.span));
 206             }
 207         } else if attribute.check_name("panic_handler") {
 208             return Some((Symbol::intern("panic_impl"), attribute.span))
 209         } else if attribute.check_name("alloc_error_handler") {
 210             return Some((Symbol::intern("oom"), attribute.span))
 211         }
 212     }
 213
 214     None
 215 }
 216
 217 pub fn collect<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) -> LanguageItems {
 218     let mut collector = LanguageItemCollector::new(tcx);
 219     for &cnum in tcx.crates().iter() {
 220         for &(def_id, item_index) in tcx.defined_lang_items(cnum).iter() {
 221             collector.collect_item(item_index, def_id);
 222         }
 223     }
 224     tcx.hir().krate().visit_all_item_likes(&mut collector);
 225     let LanguageItemCollector { mut items, .. } = collector;
 226     weak_lang_items::check_crate(tcx, &mut items);
 227     items
 228 }
 229
 230 // End of the macro
 231     }
 232 }
 233
 234 language_item_table! {
 235 //  Variant name,                Name,                 Method name,             Target;
 236     CharImplItem,                "char",               char_impl,               Target::Impl;
 237     StrImplItem,                 "str",                str_impl,                Target::Impl;
 238     SliceImplItem,               "slice",              slice_impl,              Target::Impl;
 239     SliceU8ImplItem,             "slice_u8",           slice_u8_impl,           Target::Impl;
 240     StrAllocImplItem,            "str_alloc",          str_alloc_impl,          Target::Impl;
 241     SliceAllocImplItem,          "slice_alloc",        slice_alloc_impl,        Target::Impl;
 242     SliceU8AllocImplItem,        "slice_u8_alloc",     slice_u8_alloc_impl,     Target::Impl;
 243     ConstPtrImplItem,            "const_ptr",          const_ptr_impl,          Target::Impl;
 244     MutPtrImplItem,              "mut_ptr",            mut_ptr_impl,            Target::Impl;
 245     I8ImplItem,                  "i8",                 i8_impl,                 Target::Impl;
 246     I16ImplItem,                 "i16",                i16_impl,                Target::Impl;
 247     I32ImplItem,                 "i32",                i32_impl,                Target::Impl;
 248     I64ImplItem,                 "i64",                i64_impl,                Target::Impl;
 249     I128ImplItem,                "i128",               i128_impl,               Target::Impl;
 250     IsizeImplItem,               "isize",              isize_impl,              Target::Impl;
 251     U8ImplItem,                  "u8",                 u8_impl,                 Target::Impl;
 252     U16ImplItem,                 "u16",                u16_impl,                Target::Impl;
 253     U32ImplItem,                 "u32",                u32_impl,                Target::Impl;
 254     U64ImplItem,                 "u64",                u64_impl,                Target::Impl;
 255     U128ImplItem,                "u128",               u128_impl,               Target::Impl;
 256     UsizeImplItem,               "usize",              usize_impl,              Target::Impl;
 257     F32ImplItem,                 "f32",                f32_impl,                Target::Impl;
 258     F64ImplItem,                 "f64",                f64_impl,                Target::Impl;
 259     F32RuntimeImplItem,          "f32_runtime",        f32_runtime_impl,        Target::Impl;
 260     F64RuntimeImplItem,          "f64_runtime",        f64_runtime_impl,        Target::Impl;
 261
 262     SizedTraitLangItem,          "sized",              sized_trait,             Target::Trait;
 263     UnsizeTraitLangItem,         "unsize",             unsize_trait,            Target::Trait;
 264     CopyTraitLangItem,           "copy",               copy_trait,              Target::Trait;
 265     CloneTraitLangItem,          "clone",              clone_trait,             Target::Trait;
 266     SyncTraitLangItem,           "sync",               sync_trait,              Target::Trait;
 267     FreezeTraitLangItem,         "freeze",             freeze_trait,            Target::Trait;
 268
 269     DropTraitLangItem,           "drop",               drop_trait,              Target::Trait;
 270
 271     CoerceUnsizedTraitLangItem,  "coerce_unsized",     coerce_unsized_trait,    Target::Trait;
 272     DispatchFromDynTraitLangItem,"dispatch_from_dyn",  dispatch_from_dyn_trait, Target::Trait;
 273
 274     AddTraitLangItem,            "add",                add_trait,               Target::Trait;
 275     SubTraitLangItem,            "sub",                sub_trait,               Target::Trait;
 276     MulTraitLangItem,            "mul",                mul_trait,               Target::Trait;
 277     DivTraitLangItem,            "div",                div_trait,               Target::Trait;
 278     RemTraitLangItem,            "rem",                rem_trait,               Target::Trait;
 279     NegTraitLangItem,            "neg",                neg_trait,               Target::Trait;
 280     NotTraitLangItem,            "not",                not_trait,               Target::Trait;
 281     BitXorTraitLangItem,         "bitxor",             bitxor_trait,            Target::Trait;
 282     BitAndTraitLangItem,         "bitand",             bitand_trait,            Target::Trait;
 283     BitOrTraitLangItem,          "bitor",              bitor_trait,             Target::Trait;
 284     ShlTraitLangItem,            "shl",                shl_trait,               Target::Trait;
 285     ShrTraitLangItem,            "shr",                shr_trait,               Target::Trait;
 286     AddAssignTraitLangItem,      "add_assign",         add_assign_trait,        Target::Trait;
 287     SubAssignTraitLangItem,      "sub_assign",         sub_assign_trait,        Target::Trait;
 288     MulAssignTraitLangItem,      "mul_assign",         mul_assign_trait,        Target::Trait;
 289     DivAssignTraitLangItem,      "div_assign",         div_assign_trait,        Target::Trait;
 290     RemAssignTraitLangItem,      "rem_assign",         rem_assign_trait,        Target::Trait;
 291     BitXorAssignTraitLangItem,   "bitxor_assign",      bitxor_assign_trait,     Target::Trait;
 292     BitAndAssignTraitLangItem,   "bitand_assign",      bitand_assign_trait,     Target::Trait;
 293     BitOrAssignTraitLangItem,    "bitor_assign",       bitor_assign_trait,      Target::Trait;
 294     ShlAssignTraitLangItem,      "shl_assign",         shl_assign_trait,        Target::Trait;
 295     ShrAssignTraitLangItem,      "shr_assign",         shr_assign_trait,        Target::Trait;
 296     IndexTraitLangItem,          "index",              index_trait,             Target::Trait;
 297     IndexMutTraitLangItem,       "index_mut",          index_mut_trait,         Target::Trait;
 298
 299     UnsafeCellTypeLangItem,      "unsafe_cell",        unsafe_cell_type,        Target::Struct;
 300     VaListTypeLangItem,          "va_list",            va_list,                 Target::Struct;
 301
 302     DerefTraitLangItem,          "deref",              deref_trait,             Target::Trait;
 303     DerefMutTraitLangItem,       "deref_mut",          deref_mut_trait,         Target::Trait;
 304
 305     FnTraitLangItem,             "fn",                 fn_trait,                Target::Trait;
 306     FnMutTraitLangItem,          "fn_mut",             fn_mut_trait,            Target::Trait;
 307     FnOnceTraitLangItem,         "fn_once",            fn_once_trait,           Target::Trait;
 308
 309     GeneratorStateLangItem,      "generator_state",    gen_state,               Target::Enum;
 310     GeneratorTraitLangItem,      "generator",          gen_trait,               Target::Trait;
 311
 312     EqTraitLangItem,             "eq",                 eq_trait,                Target::Trait;
 313     PartialOrdTraitLangItem,     "partial_ord",        partial_ord_trait,       Target::Trait;
 314     OrdTraitLangItem,            "ord",                ord_trait,               Target::Trait;
 315
 316     // A number of panic-related lang items. The `panic` item corresponds to
 317     // divide-by-zero and various panic cases with `match`. The
 318     // `panic_bounds_check` item is for indexing arrays.
 319     //
 320     // The `begin_unwind` lang item has a predefined symbol name and is sort of
 321     // a "weak lang item" in the sense that a crate is not required to have it
 322     // defined to use it, but a final product is required to define it
 323     // somewhere. Additionally, there are restrictions on crates that use a weak
 324     // lang item, but do not have it defined.
 325     PanicFnLangItem,             "panic",              panic_fn,                Target::Fn;
 326     PanicBoundsCheckFnLangItem,  "panic_bounds_check", panic_bounds_check_fn,   Target::Fn;
 327     PanicInfoLangItem,           "panic_info",         panic_info,              Target::Struct;
 328     PanicImplLangItem,           "panic_impl",         panic_impl,              Target::Fn;
 329     // Libstd panic entry point. Necessary for const eval to be able to catch it
 330     BeginPanicFnLangItem,        "begin_panic",        begin_panic_fn,          Target::Fn;
 331
 332     ExchangeMallocFnLangItem,    "exchange_malloc",    exchange_malloc_fn,      Target::Fn;
 333     BoxFreeFnLangItem,           "box_free",           box_free_fn,             Target::Fn;
 334     DropInPlaceFnLangItem,       "drop_in_place",      drop_in_place_fn,        Target::Fn;
 335     OomLangItem,                 "oom",                oom,                     Target::Fn;
 336     AllocLayoutLangItem,         "alloc_layout",       alloc_layout,            Target::Struct;
 337
 338     StartFnLangItem,             "start",              start_fn,                Target::Fn;
 339
 340     EhPersonalityLangItem,       "eh_personality",     eh_personality,          Target::Fn;
 341     EhUnwindResumeLangItem,      "eh_unwind_resume",   eh_unwind_resume,        Target::Fn;
 342     MSVCTryFilterLangItem,       "msvc_try_filter",    msvc_try_filter,         Target::Static;
 343
 344     OwnedBoxLangItem,            "owned_box",          owned_box,               Target::Struct;
 345
 346     PhantomDataItem,             "phantom_data",       phantom_data,            Target::Struct;
 347
 348     ManuallyDropItem,            "manually_drop",      manually_drop,           Target::Struct;
 349
 350     DebugTraitLangItem,          "debug_trait",        debug_trait,             Target::Trait;
 351
 352     // A lang item for each of the 128-bit operators we can optionally lower.
 353     I128AddFnLangItem,           "i128_add",           i128_add_fn,             Target::Fn;
 354     U128AddFnLangItem,           "u128_add",           u128_add_fn,             Target::Fn;
 355     I128SubFnLangItem,           "i128_sub",           i128_sub_fn,             Target::Fn;
 356     U128SubFnLangItem,           "u128_sub",           u128_sub_fn,             Target::Fn;
 357     I128MulFnLangItem,           "i128_mul",           i128_mul_fn,             Target::Fn;
 358     U128MulFnLangItem,           "u128_mul",           u128_mul_fn,             Target::Fn;
 359     I128DivFnLangItem,           "i128_div",           i128_div_fn,             Target::Fn;
 360     U128DivFnLangItem,           "u128_div",           u128_div_fn,             Target::Fn;
 361     I128RemFnLangItem,           "i128_rem",           i128_rem_fn,             Target::Fn;
 362     U128RemFnLangItem,           "u128_rem",           u128_rem_fn,             Target::Fn;
 363     I128ShlFnLangItem,           "i128_shl",           i128_shl_fn,             Target::Fn;
 364     U128ShlFnLangItem,           "u128_shl",           u128_shl_fn,             Target::Fn;
 365     I128ShrFnLangItem,           "i128_shr",           i128_shr_fn,             Target::Fn;
 366     U128ShrFnLangItem,           "u128_shr",           u128_shr_fn,             Target::Fn;
 367     // And overflow versions for the operators that are checkable.
 368     // While MIR calls these Checked*, they return (T,bool), not Option<T>.
 369     I128AddoFnLangItem,          "i128_addo",          i128_addo_fn,            Target::Fn;
 370     U128AddoFnLangItem,          "u128_addo",          u128_addo_fn,            Target::Fn;
 371     I128SuboFnLangItem,          "i128_subo",          i128_subo_fn,            Target::Fn;
 372     U128SuboFnLangItem,          "u128_subo",          u128_subo_fn,            Target::Fn;
 373     I128MuloFnLangItem,          "i128_mulo",          i128_mulo_fn,            Target::Fn;
 374     U128MuloFnLangItem,          "u128_mulo",          u128_mulo_fn,            Target::Fn;
 375     I128ShloFnLangItem,          "i128_shlo",          i128_shlo_fn,            Target::Fn;
 376     U128ShloFnLangItem,          "u128_shlo",          u128_shlo_fn,            Target::Fn;
 377     I128ShroFnLangItem,          "i128_shro",          i128_shro_fn,            Target::Fn;
 378     U128ShroFnLangItem,          "u128_shro",          u128_shro_fn,            Target::Fn;
 379
 380     // Align offset for stride != 1, must not panic.
 381     AlignOffsetLangItem,         "align_offset",       align_offset_fn,         Target::Fn;
 382
 383     TerminationTraitLangItem,    "termination",        termination,             Target::Trait;
 384
 385     Arc,                         "arc",                arc,                     Target::Struct;
 386     Rc,                          "rc",                 rc,                      Target::Struct;
 387 }
 388
 389 impl<'a, 'tcx, 'gcx> TyCtxt<'a, 'tcx, 'gcx> {
 390     pub fn require_lang_item(&self, lang_item: LangItem) -> DefId {
 391         self.lang_items().require(lang_item).unwrap_or_else(|msg| {
 392             self.sess.fatal(&msg)
 393         })
 394     }
 395 }