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::map as hir_map;
  25 use session::Session;
  26 use hir::def_id::DefId;
  27 use ty;
  28 use middle::weak_lang_items;
  29 use util::nodemap::FxHashMap;
  30
  31 use syntax::ast;
  32 use syntax::symbol::Symbol;
  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; )*
  41     ) => {
  42
  43
  44 enum_from_u32! {
  45     #[derive(Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
  46     pub enum LangItem {
  47         $($variant,)*
  48     }
  49 }
  50
  51 pub struct LanguageItems {
  52     pub items: Vec<Option<DefId>>,
  53     pub missing: Vec<LangItem>,
  54 }
  55
  56 impl LanguageItems {
  57     pub fn new() -> LanguageItems {
  58         fn foo(_: LangItem) -> Option<DefId> { None }
  59
  60         LanguageItems {
  61             items: vec![$(foo($variant)),*],
  62             missing: Vec::new(),
  63         }
  64     }
  65
  66     pub fn items(&self) -> &[Option<DefId>] {
  67         &*self.items
  68     }
  69
  70     pub fn item_name(index: usize) -> &'static str {
  71         let item: Option<LangItem> = LangItem::from_u32(index as u32);
  72         match item {
  73             $( Some($variant) => $name, )*
  74             None => "???"
  75         }
  76     }
  77
  78     pub fn require(&self, it: LangItem) -> Result<DefId, String> {
  79         match self.items[it as usize] {
  80             Some(id) => Ok(id),
  81             None => {
  82                 Err(format!("requires `{}` lang_item",
  83                             LanguageItems::item_name(it as usize)))
  84             }
  85         }
  86     }
  87
  88     pub fn require_owned_box(&self) -> Result<DefId, String> {
  89         self.require(OwnedBoxLangItem)
  90     }
  91
  92     pub fn fn_trait_kind(&self, id: DefId) -> Option<ty::ClosureKind> {
  93         let def_id_kinds = [
  94             (self.fn_trait(), ty::ClosureKind::Fn),
  95             (self.fn_mut_trait(), ty::ClosureKind::FnMut),
  96             (self.fn_once_trait(), ty::ClosureKind::FnOnce),
  97             ];
  98
  99         for &(opt_def_id, kind) in &def_id_kinds {
 100             if Some(id) == opt_def_id {
 101                 return Some(kind);
 102             }
 103         }
 104
 105         None
 106     }
 107
 108     $(
 109         #[allow(dead_code)]
 110         pub fn $method(&self) -> Option<DefId> {
 111             self.items[$variant as usize]
 112         }
 113     )*
 114 }
 115
 116 struct LanguageItemCollector<'a, 'tcx: 'a> {
 117     items: LanguageItems,
 118
 119     hir_map: &'a hir_map::Map<'tcx>,
 120
 121     session: &'a Session,
 122
 123     item_refs: FxHashMap<&'static str, usize>,
 124 }
 125
 126 impl<'a, 'v, 'tcx> ItemLikeVisitor<'v> for LanguageItemCollector<'a, 'tcx> {
 127     fn visit_item(&mut self, item: &hir::Item) {
 128         if let Some(value) = extract(&item.attrs) {
 129             let item_index = self.item_refs.get(&*value.as_str()).cloned();
 130
 131             if let Some(item_index) = item_index {
 132                 self.collect_item(item_index, self.hir_map.local_def_id(item.id))
 133             } else {
 134                 let span = self.hir_map.span(item.id);
 135                 span_err!(self.session, span, E0522,
 136                           "definition of an unknown language item: `{}`.",
 137                           value);
 138             }
 139         }
 140     }
 141
 142     fn visit_trait_item(&mut self, _trait_item: &hir::TraitItem) {
 143         // at present, lang items are always items, not trait items
 144     }
 145
 146     fn visit_impl_item(&mut self, _impl_item: &hir::ImplItem) {
 147         // at present, lang items are always items, not impl items
 148     }
 149 }
 150
 151 impl<'a, 'tcx> LanguageItemCollector<'a, 'tcx> {
 152     pub fn new(session: &'a Session, hir_map: &'a hir_map::Map<'tcx>)
 153                -> LanguageItemCollector<'a, 'tcx> {
 154         let mut item_refs = FxHashMap();
 155
 156         $( item_refs.insert($name, $variant as usize); )*
 157
 158         LanguageItemCollector {
 159             session,
 160             hir_map,
 161             items: LanguageItems::new(),
 162             item_refs,
 163         }
 164     }
 165
 166     pub fn collect_item(&mut self, item_index: usize,
 167                         item_def_id: DefId) {
 168         // Check for duplicates.
 169         match self.items.items[item_index] {
 170             Some(original_def_id) if original_def_id != item_def_id => {
 171                 let cstore = &self.session.cstore;
 172                 let name = LanguageItems::item_name(item_index);
 173                 let mut err = match self.hir_map.span_if_local(item_def_id) {
 174                     Some(span) => struct_span_err!(
 175                         self.session,
 176                         span,
 177                         E0152,
 178                         "duplicate lang item found: `{}`.",
 179                         name),
 180                     None => self.session.struct_err(&format!(
 181                             "duplicate lang item in crate `{}`: `{}`.",
 182                             cstore.crate_name(item_def_id.krate),
 183                             name)),
 184                 };
 185                 if let Some(span) = self.hir_map.span_if_local(original_def_id) {
 186                     span_note!(&mut err, span,
 187                                "first defined here.");
 188                 } else {
 189                     err.note(&format!("first defined in crate `{}`.",
 190                                       cstore.crate_name(original_def_id.krate)));
 191                 }
 192                 err.emit();
 193             }
 194             _ => {
 195                 // OK.
 196             }
 197         }
 198
 199         // Matched.
 200         self.items.items[item_index] = Some(item_def_id);
 201     }
 202
 203     pub fn collect_local_language_items(&mut self, krate: &hir::Crate) {
 204         krate.visit_all_item_likes(self);
 205     }
 206
 207     pub fn collect_external_language_items(&mut self) {
 208         let cstore = &self.session.cstore;
 209
 210         for cnum in cstore.crates() {
 211             for (index, item_index) in cstore.lang_items(cnum) {
 212                 let def_id = DefId { krate: cnum, index: index };
 213                 self.collect_item(item_index, def_id);
 214             }
 215         }
 216     }
 217
 218     pub fn collect(&mut self, krate: &hir::Crate) {
 219         self.collect_external_language_items();
 220         self.collect_local_language_items(krate);
 221     }
 222 }
 223
 224 pub fn extract(attrs: &[ast::Attribute]) -> Option<Symbol> {
 225     for attribute in attrs {
 226         if attribute.check_name("lang") {
 227             if let Some(value) = attribute.value_str() {
 228                 return Some(value)
 229             }
 230         }
 231     }
 232
 233     return None;
 234 }
 235
 236 pub fn collect_language_items(session: &Session,
 237                               map: &hir_map::Map)
 238                               -> LanguageItems {
 239     let krate: &hir::Crate = map.krate();
 240     let mut collector = LanguageItemCollector::new(session, map);
 241     collector.collect(krate);
 242     let LanguageItemCollector { mut items, .. } = collector;
 243     weak_lang_items::check_crate(krate, session, &mut items);
 244     items
 245 }
 246
 247 // End of the macro
 248     }
 249 }
 250
 251 language_item_table! {
 252 //  Variant name,                    Name,                      Method name;
 253     CharImplItem,                    "char",                    char_impl;
 254     StrImplItem,                     "str",                     str_impl;
 255     SliceImplItem,                   "slice",                   slice_impl;
 256     ConstPtrImplItem,                "const_ptr",               const_ptr_impl;
 257     MutPtrImplItem,                  "mut_ptr",                 mut_ptr_impl;
 258     I8ImplItem,                      "i8",                      i8_impl;
 259     I16ImplItem,                     "i16",                     i16_impl;
 260     I32ImplItem,                     "i32",                     i32_impl;
 261     I64ImplItem,                     "i64",                     i64_impl;
 262     I128ImplItem,                     "i128",                   i128_impl;
 263     IsizeImplItem,                   "isize",                   isize_impl;
 264     U8ImplItem,                      "u8",                      u8_impl;
 265     U16ImplItem,                     "u16",                     u16_impl;
 266     U32ImplItem,                     "u32",                     u32_impl;
 267     U64ImplItem,                     "u64",                     u64_impl;
 268     U128ImplItem,                    "u128",                    u128_impl;
 269     UsizeImplItem,                   "usize",                   usize_impl;
 270     F32ImplItem,                     "f32",                     f32_impl;
 271     F64ImplItem,                     "f64",                     f64_impl;
 272
 273     SendTraitLangItem,               "send",                    send_trait;
 274     SizedTraitLangItem,              "sized",                   sized_trait;
 275     UnsizeTraitLangItem,             "unsize",                  unsize_trait;
 276     CopyTraitLangItem,               "copy",                    copy_trait;
 277     SyncTraitLangItem,               "sync",                    sync_trait;
 278     FreezeTraitLangItem,             "freeze",                  freeze_trait;
 279
 280     DropTraitLangItem,               "drop",                    drop_trait;
 281
 282     CoerceUnsizedTraitLangItem,      "coerce_unsized",          coerce_unsized_trait;
 283
 284     AddTraitLangItem,                "add",                     add_trait;
 285     SubTraitLangItem,                "sub",                     sub_trait;
 286     MulTraitLangItem,                "mul",                     mul_trait;
 287     DivTraitLangItem,                "div",                     div_trait;
 288     RemTraitLangItem,                "rem",                     rem_trait;
 289     NegTraitLangItem,                "neg",                     neg_trait;
 290     NotTraitLangItem,                "not",                     not_trait;
 291     BitXorTraitLangItem,             "bitxor",                  bitxor_trait;
 292     BitAndTraitLangItem,             "bitand",                  bitand_trait;
 293     BitOrTraitLangItem,              "bitor",                   bitor_trait;
 294     ShlTraitLangItem,                "shl",                     shl_trait;
 295     ShrTraitLangItem,                "shr",                     shr_trait;
 296     AddAssignTraitLangItem,          "add_assign",              add_assign_trait;
 297     SubAssignTraitLangItem,          "sub_assign",              sub_assign_trait;
 298     MulAssignTraitLangItem,          "mul_assign",              mul_assign_trait;
 299     DivAssignTraitLangItem,          "div_assign",              div_assign_trait;
 300     RemAssignTraitLangItem,          "rem_assign",              rem_assign_trait;
 301     BitXorAssignTraitLangItem,       "bitxor_assign",           bitxor_assign_trait;
 302     BitAndAssignTraitLangItem,       "bitand_assign",           bitand_assign_trait;
 303     BitOrAssignTraitLangItem,        "bitor_assign",            bitor_assign_trait;
 304     ShlAssignTraitLangItem,          "shl_assign",              shl_assign_trait;
 305     ShrAssignTraitLangItem,          "shr_assign",              shr_assign_trait;
 306     IndexTraitLangItem,              "index",                   index_trait;
 307     IndexMutTraitLangItem,           "index_mut",               index_mut_trait;
 308
 309     UnsafeCellTypeLangItem,          "unsafe_cell",             unsafe_cell_type;
 310
 311     DerefTraitLangItem,              "deref",                   deref_trait;
 312     DerefMutTraitLangItem,           "deref_mut",               deref_mut_trait;
 313
 314     FnTraitLangItem,                 "fn",                      fn_trait;
 315     FnMutTraitLangItem,              "fn_mut",                  fn_mut_trait;
 316     FnOnceTraitLangItem,             "fn_once",                 fn_once_trait;
 317
 318     EqTraitLangItem,                 "eq",                      eq_trait;
 319     OrdTraitLangItem,                "ord",                     ord_trait;
 320
 321     StrEqFnLangItem,                 "str_eq",                  str_eq_fn;
 322
 323     // A number of panic-related lang items. The `panic` item corresponds to
 324     // divide-by-zero and various panic cases with `match`. The
 325     // `panic_bounds_check` item is for indexing arrays.
 326     //
 327     // The `begin_unwind` lang item has a predefined symbol name and is sort of
 328     // a "weak lang item" in the sense that a crate is not required to have it
 329     // defined to use it, but a final product is required to define it
 330     // somewhere. Additionally, there are restrictions on crates that use a weak
 331     // lang item, but do not have it defined.
 332     PanicFnLangItem,                 "panic",                   panic_fn;
 333     PanicBoundsCheckFnLangItem,      "panic_bounds_check",      panic_bounds_check_fn;
 334     PanicFmtLangItem,                "panic_fmt",               panic_fmt;
 335
 336     ExchangeMallocFnLangItem,        "exchange_malloc",         exchange_malloc_fn;
 337     BoxFreeFnLangItem,               "box_free",                box_free_fn;
 338     DropInPlaceFnLangItem,             "drop_in_place",           drop_in_place_fn;
 339
 340     StartFnLangItem,                 "start",                   start_fn;
 341
 342     EhPersonalityLangItem,           "eh_personality",          eh_personality;
 343     EhUnwindResumeLangItem,          "eh_unwind_resume",        eh_unwind_resume;
 344     MSVCTryFilterLangItem,           "msvc_try_filter",         msvc_try_filter;
 345
 346     OwnedBoxLangItem,                "owned_box",               owned_box;
 347
 348     PhantomDataItem,                 "phantom_data",            phantom_data;
 349
 350     // Deprecated:
 351     CovariantTypeItem,               "covariant_type",          covariant_type;
 352     ContravariantTypeItem,           "contravariant_type",      contravariant_type;
 353     InvariantTypeItem,               "invariant_type",          invariant_type;
 354     CovariantLifetimeItem,           "covariant_lifetime",      covariant_lifetime;
 355     ContravariantLifetimeItem,       "contravariant_lifetime",  contravariant_lifetime;
 356     InvariantLifetimeItem,           "invariant_lifetime",      invariant_lifetime;
 357
 358     NonZeroItem,                     "non_zero",                non_zero;
 359
 360     DebugTraitLangItem,              "debug_trait",             debug_trait;
 361 }
 362
 363 impl<'a, 'tcx, 'gcx> ty::TyCtxt<'a, 'tcx, 'gcx> {
 364     pub fn require_lang_item(&self, lang_item: LangItem) -> DefId {
 365         self.lang_items.require(lang_item).unwrap_or_else(|msg| {
 366             self.sess.fatal(&msg)
 367         })
 368     }
 369 }