src/librustc_span/symbol.rs

   1 //! An "interner" is a data structure that associates values with usize tags and
   2 //! allows bidirectional lookup; i.e., given a value, one can easily find the
   3 //! type, and vice versa.
   4
   5 use arena::DroplessArena;
   6 use rustc_data_structures::fx::FxHashMap;
   7 use rustc_data_structures::stable_hasher::{HashStable, StableHasher, ToStableHashKey};
   8 use rustc_index::vec::Idx;
   9 use rustc_macros::{symbols, HashStable_Generic};
  10 use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
  11 use rustc_serialize::{UseSpecializedDecodable, UseSpecializedEncodable};
  12
  13 use std::cmp::{Ord, PartialEq, PartialOrd};
  14 use std::fmt;
  15 use std::hash::{Hash, Hasher};
  16 use std::str;
  17
  18 use crate::{Span, DUMMY_SP, GLOBALS};
  19
  20 #[cfg(test)]
  21 mod tests;
  22
  23 symbols! {
  24     // After modifying this list adjust `is_special`, `is_used_keyword`/`is_unused_keyword`,
  25     // this should be rarely necessary though if the keywords are kept in alphabetic order.
  26     Keywords {
  27         // Special reserved identifiers used internally for elided lifetimes,
  28         // unnamed method parameters, crate root module, error recovery etc.
  29         Invalid:            "",
  30         PathRoot:           "{{root}}",
  31         DollarCrate:        "$crate",
  32         Underscore:         "_",
  33
  34         // Keywords that are used in stable Rust.
  35         As:                 "as",
  36         Break:              "break",
  37         Const:              "const",
  38         Continue:           "continue",
  39         Crate:              "crate",
  40         Else:               "else",
  41         Enum:               "enum",
  42         Extern:             "extern",
  43         False:              "false",
  44         Fn:                 "fn",
  45         For:                "for",
  46         If:                 "if",
  47         Impl:               "impl",
  48         In:                 "in",
  49         Let:                "let",
  50         Loop:               "loop",
  51         Match:              "match",
  52         Mod:                "mod",
  53         Move:               "move",
  54         Mut:                "mut",
  55         Pub:                "pub",
  56         Ref:                "ref",
  57         Return:             "return",
  58         SelfLower:          "self",
  59         SelfUpper:          "Self",
  60         Static:             "static",
  61         Struct:             "struct",
  62         Super:              "super",
  63         Trait:              "trait",
  64         True:               "true",
  65         Type:               "type",
  66         Unsafe:             "unsafe",
  67         Use:                "use",
  68         Where:              "where",
  69         While:              "while",
  70
  71         // Keywords that are used in unstable Rust or reserved for future use.
  72         Abstract:           "abstract",
  73         Become:             "become",
  74         Box:                "box",
  75         Do:                 "do",
  76         Final:              "final",
  77         Macro:              "macro",
  78         Override:           "override",
  79         Priv:               "priv",
  80         Typeof:             "typeof",
  81         Unsized:            "unsized",
  82         Virtual:            "virtual",
  83         Yield:              "yield",
  84
  85         // Edition-specific keywords that are used in stable Rust.
  86         Async:              "async", // >= 2018 Edition only
  87         Await:              "await", // >= 2018 Edition only
  88         Dyn:                "dyn", // >= 2018 Edition only
  89
  90         // Edition-specific keywords that are used in unstable Rust or reserved for future use.
  91         Try:                "try", // >= 2018 Edition only
  92
  93         // Special lifetime names
  94         UnderscoreLifetime: "'_",
  95         StaticLifetime:     "'static",
  96
  97         // Weak keywords, have special meaning only in specific contexts.
  98         Auto:               "auto",
  99         Catch:              "catch",
 100         Default:            "default",
 101         Raw:                "raw",
 102         Union:              "union",
 103     }
 104
 105     // Symbols that can be referred to with rustc_span::sym::*. The symbol is
 106     // the stringified identifier unless otherwise specified (e.g.
 107     // `proc_dash_macro` represents "proc-macro").
 108     //
 109     // As well as the symbols listed, there are symbols for the the strings
 110     // "0", "1", ..., "9", which are accessible via `sym::integer`.
 111     Symbols {
 112         aarch64_target_feature,
 113         abi,
 114         abi_amdgpu_kernel,
 115         abi_efiapi,
 116         abi_msp430_interrupt,
 117         abi_ptx,
 118         abi_sysv64,
 119         abi_thiscall,
 120         abi_unadjusted,
 121         abi_vectorcall,
 122         abi_x86_interrupt,
 123         aborts,
 124         add_with_overflow,
 125         advanced_slice_patterns,
 126         adx_target_feature,
 127         alias,
 128         align,
 129         alignstack,
 130         all,
 131         allocator,
 132         allocator_internals,
 133         alloc_error_handler,
 134         allow,
 135         allowed,
 136         allow_fail,
 137         allow_internal_unsafe,
 138         allow_internal_unstable,
 139         allow_internal_unstable_backcompat_hack,
 140         always,
 141         and,
 142         any,
 143         arbitrary_enum_discriminant,
 144         arbitrary_self_types,
 145         Arguments,
 146         ArgumentV1,
 147         arm_target_feature,
 148         asm,
 149         assert,
 150         associated_consts,
 151         associated_type_bounds,
 152         associated_type_defaults,
 153         associated_types,
 154         assume_init,
 155         async_await,
 156         async_closure,
 157         attr,
 158         attributes,
 159         attr_literals,
 160         augmented_assignments,
 161         automatically_derived,
 162         avx512_target_feature,
 163         await_macro,
 164         begin_panic,
 165         bench,
 166         bin,
 167         bind_by_move_pattern_guards,
 168         bindings_after_at,
 169         block,
 170         bool,
 171         borrowck_graphviz_postflow,
 172         borrowck_graphviz_preflow,
 173         box_patterns,
 174         box_syntax,
 175         braced_empty_structs,
 176         bswap,
 177         bitreverse,
 178         C,
 179         caller_location,
 180         cdylib,
 181         cfg,
 182         cfg_attr,
 183         cfg_attr_multi,
 184         cfg_doctest,
 185         cfg_sanitize,
 186         cfg_target_feature,
 187         cfg_target_has_atomic,
 188         cfg_target_thread_local,
 189         cfg_target_vendor,
 190         char,
 191         clippy,
 192         clone,
 193         Clone,
 194         clone_closures,
 195         clone_from,
 196         closure_to_fn_coercion,
 197         cmp,
 198         cmpxchg16b_target_feature,
 199         cold,
 200         column,
 201         compile_error,
 202         compiler_builtins,
 203         concat,
 204         concat_idents,
 205         conservative_impl_trait,
 206         console,
 207         const_compare_raw_pointers,
 208         const_constructor,
 209         const_extern_fn,
 210         const_fn,
 211         const_fn_union,
 212         const_generics,
 213         const_if_match,
 214         const_indexing,
 215         const_in_array_repeat_expressions,
 216         const_let,
 217         const_loop,
 218         const_mut_refs,
 219         const_panic,
 220         const_raw_ptr_deref,
 221         const_raw_ptr_to_usize_cast,
 222         const_transmute,
 223         contents,
 224         context,
 225         convert,
 226         Copy,
 227         copy_closures,
 228         core,
 229         core_intrinsics,
 230         crate_id,
 231         crate_in_paths,
 232         crate_local,
 233         crate_name,
 234         crate_type,
 235         crate_visibility_modifier,
 236         ctpop,
 237         cttz,
 238         cttz_nonzero,
 239         ctlz,
 240         ctlz_nonzero,
 241         custom_attribute,
 242         custom_derive,
 243         custom_inner_attributes,
 244         custom_test_frameworks,
 245         c_variadic,
 246         debug_trait,
 247         declare_lint_pass,
 248         decl_macro,
 249         Debug,
 250         Decodable,
 251         Default,
 252         default_lib_allocator,
 253         default_type_parameter_fallback,
 254         default_type_params,
 255         delay_span_bug_from_inside_query,
 256         deny,
 257         deprecated,
 258         deref,
 259         deref_mut,
 260         derive,
 261         diagnostic,
 262         direct,
 263         doc,
 264         doc_alias,
 265         doc_cfg,
 266         doc_keyword,
 267         doc_masked,
 268         doc_spotlight,
 269         doctest,
 270         document_private_items,
 271         dotdoteq_in_patterns,
 272         dotdot_in_tuple_patterns,
 273         double_braced_crate: "{{crate}}",
 274         double_braced_impl: "{{impl}}",
 275         double_braced_misc: "{{misc}}",
 276         double_braced_closure: "{{closure}}",
 277         double_braced_constructor: "{{constructor}}",
 278         double_braced_constant: "{{constant}}",
 279         double_braced_opaque: "{{opaque}}",
 280         dropck_eyepatch,
 281         dropck_parametricity,
 282         drop_types_in_const,
 283         dylib,
 284         dyn_trait,
 285         eh_personality,
 286         eh_unwind_resume,
 287         enable,
 288         Encodable,
 289         env,
 290         eq,
 291         err,
 292         Err,
 293         Eq,
 294         Equal,
 295         enclosing_scope,
 296         except,
 297         exclusive_range_pattern,
 298         exhaustive_integer_patterns,
 299         exhaustive_patterns,
 300         existential_type,
 301         expected,
 302         export_name,
 303         expr,
 304         extern_absolute_paths,
 305         external_doc,
 306         extern_crate_item_prelude,
 307         extern_crate_self,
 308         extern_in_paths,
 309         extern_prelude,
 310         extern_types,
 311         f16c_target_feature,
 312         f32,
 313         f64,
 314         feature,
 315         ffi_returns_twice,
 316         field,
 317         field_init_shorthand,
 318         file,
 319         fmt,
 320         fmt_internals,
 321         fn_must_use,
 322         forbid,
 323         format_args,
 324         format_args_nl,
 325         from,
 326         From,
 327         from_desugaring,
 328         from_error,
 329         from_generator,
 330         from_method,
 331         from_ok,
 332         from_usize,
 333         fundamental,
 334         future,
 335         Future,
 336         FxHashSet,
 337         FxHashMap,
 338         gen_future,
 339         generators,
 340         generic_associated_types,
 341         generic_param_attrs,
 342         global_allocator,
 343         global_asm,
 344         globs,
 345         hash,
 346         Hash,
 347         HashSet,
 348         HashMap,
 349         hexagon_target_feature,
 350         hidden,
 351         homogeneous_aggregate,
 352         html_favicon_url,
 353         html_logo_url,
 354         html_no_source,
 355         html_playground_url,
 356         html_root_url,
 357         i128,
 358         i128_type,
 359         i16,
 360         i32,
 361         i64,
 362         i8,
 363         ident,
 364         if_let,
 365         if_while_or_patterns,
 366         ignore,
 367         impl_header_lifetime_elision,
 368         impl_lint_pass,
 369         impl_trait_in_bindings,
 370         import_shadowing,
 371         index,
 372         index_mut,
 373         in_band_lifetimes,
 374         include,
 375         include_bytes,
 376         include_str,
 377         inclusive_range_syntax,
 378         infer_outlives_requirements,
 379         infer_static_outlives_requirements,
 380         inline,
 381         intel,
 382         into_iter,
 383         IntoIterator,
 384         into_result,
 385         intrinsics,
 386         irrefutable_let_patterns,
 387         isize,
 388         issue,
 389         issue_5723_bootstrap,
 390         issue_tracker_base_url,
 391         item,
 392         item_context: "ItemContext",
 393         item_like_imports,
 394         iter,
 395         Iterator,
 396         keyword,
 397         kind,
 398         label,
 399         label_break_value,
 400         lang,
 401         lang_items,
 402         let_chains,
 403         lhs,
 404         lib,
 405         lifetime,
 406         line,
 407         link,
 408         linkage,
 409         link_args,
 410         link_cfg,
 411         link_llvm_intrinsics,
 412         link_name,
 413         link_ordinal,
 414         link_section,
 415         LintPass,
 416         lint_reasons,
 417         literal,
 418         local_inner_macros,
 419         log_syntax,
 420         loop_break_value,
 421         macro_at_most_once_rep,
 422         macro_escape,
 423         macro_export,
 424         macro_lifetime_matcher,
 425         macro_literal_matcher,
 426         macro_reexport,
 427         macro_rules,
 428         macros_in_extern,
 429         macro_use,
 430         macro_vis_matcher,
 431         main,
 432         managed_boxes,
 433         marker,
 434         marker_trait_attr,
 435         masked,
 436         match_beginning_vert,
 437         match_default_bindings,
 438         may_dangle,
 439         maybe_uninit_uninit,
 440         maybe_uninit_zeroed,
 441         mem_uninitialized,
 442         mem_zeroed,
 443         member_constraints,
 444         message,
 445         meta,
 446         min_align_of,
 447         min_const_fn,
 448         min_const_unsafe_fn,
 449         mips_target_feature,
 450         mmx_target_feature,
 451         module,
 452         module_path,
 453         more_struct_aliases,
 454         move_val_init,
 455         movbe_target_feature,
 456         mul_with_overflow,
 457         must_use,
 458         naked,
 459         naked_functions,
 460         name,
 461         needs_allocator,
 462         needs_drop,
 463         needs_panic_runtime,
 464         negate_unsigned,
 465         never,
 466         never_type,
 467         never_type_fallback,
 468         new,
 469         next,
 470         __next,
 471         nll,
 472         no_builtins,
 473         no_core,
 474         no_crate_inject,
 475         no_debug,
 476         no_default_passes,
 477         no_implicit_prelude,
 478         no_inline,
 479         no_link,
 480         no_main,
 481         no_mangle,
 482         non_ascii_idents,
 483         None,
 484         non_exhaustive,
 485         non_modrs_mods,
 486         no_stack_check,
 487         no_start,
 488         no_std,
 489         not,
 490         note,
 491         object_safe_for_dispatch,
 492         Ok,
 493         omit_gdb_pretty_printer_section,
 494         on,
 495         on_unimplemented,
 496         oom,
 497         ops,
 498         optimize,
 499         optimize_attribute,
 500         optin_builtin_traits,
 501         option,
 502         Option,
 503         option_env,
 504         opt_out_copy,
 505         or,
 506         or_patterns,
 507         Ord,
 508         Ordering,
 509         Output,
 510         overlapping_marker_traits,
 511         packed,
 512         panic,
 513         panic_handler,
 514         panic_impl,
 515         panic_implementation,
 516         panic_runtime,
 517         parent_trait,
 518         partial_cmp,
 519         param_attrs,
 520         PartialEq,
 521         PartialOrd,
 522         passes,
 523         pat,
 524         path,
 525         pattern_parentheses,
 526         Pending,
 527         pin,
 528         Pin,
 529         pinned,
 530         platform_intrinsics,
 531         plugin,
 532         plugin_registrar,
 533         plugins,
 534         Poll,
 535         poll_with_tls_context,
 536         powerpc_target_feature,
 537         precise_pointer_size_matching,
 538         pref_align_of,
 539         prelude,
 540         prelude_import,
 541         primitive,
 542         proc_dash_macro: "proc-macro",
 543         proc_macro,
 544         proc_macro_attribute,
 545         proc_macro_def_site,
 546         proc_macro_derive,
 547         proc_macro_expr,
 548         proc_macro_gen,
 549         proc_macro_hygiene,
 550         proc_macro_internals,
 551         proc_macro_mod,
 552         proc_macro_non_items,
 553         proc_macro_path_invoc,
 554         profiler_runtime,
 555         ptr_offset_from,
 556         pub_restricted,
 557         pushpop_unsafe,
 558         quad_precision_float,
 559         question_mark,
 560         quote,
 561         Range,
 562         RangeFrom,
 563         RangeFull,
 564         RangeInclusive,
 565         RangeTo,
 566         RangeToInclusive,
 567         raw_dylib,
 568         raw_identifiers,
 569         raw_ref_op,
 570         Ready,
 571         reason,
 572         recursion_limit,
 573         reexport_test_harness_main,
 574         reflect,
 575         register_attr,
 576         register_tool,
 577         relaxed_adts,
 578         repr,
 579         repr128,
 580         repr_align,
 581         repr_align_enum,
 582         repr_packed,
 583         repr_simd,
 584         repr_transparent,
 585         re_rebalance_coherence,
 586         result,
 587         Result,
 588         Return,
 589         rhs,
 590         rlib,
 591         rotate_left,
 592         rotate_right,
 593         rt,
 594         rtm_target_feature,
 595         rust,
 596         rust_2015_preview,
 597         rust_2018_preview,
 598         rust_begin_unwind,
 599         rustc,
 600         RustcDecodable,
 601         RustcEncodable,
 602         rustc_allocator,
 603         rustc_allocator_nounwind,
 604         rustc_allow_const_fn_ptr,
 605         rustc_args_required_const,
 606         rustc_attrs,
 607         rustc_builtin_macro,
 608         rustc_clean,
 609         rustc_const_unstable,
 610         rustc_const_stable,
 611         rustc_conversion_suggestion,
 612         rustc_def_path,
 613         rustc_deprecated,
 614         rustc_diagnostic_item,
 615         rustc_diagnostic_macros,
 616         rustc_dirty,
 617         rustc_dummy,
 618         rustc_dump_env_program_clauses,
 619         rustc_dump_program_clauses,
 620         rustc_dump_user_substs,
 621         rustc_error,
 622         rustc_expected_cgu_reuse,
 623         rustc_if_this_changed,
 624         rustc_inherit_overflow_checks,
 625         rustc_layout,
 626         rustc_layout_scalar_valid_range_end,
 627         rustc_layout_scalar_valid_range_start,
 628         rustc_macro_transparency,
 629         rustc_mir,
 630         rustc_nonnull_optimization_guaranteed,
 631         rustc_object_lifetime_default,
 632         rustc_on_unimplemented,
 633         rustc_outlives,
 634         rustc_paren_sugar,
 635         rustc_partition_codegened,
 636         rustc_partition_reused,
 637         rustc_peek,
 638         rustc_peek_definite_init,
 639         rustc_peek_maybe_init,
 640         rustc_peek_maybe_uninit,
 641         rustc_peek_indirectly_mutable,
 642         rustc_private,
 643         rustc_proc_macro_decls,
 644         rustc_promotable,
 645         rustc_regions,
 646         rustc_stable,
 647         rustc_std_internal_symbol,
 648         rustc_symbol_name,
 649         rustc_synthetic,
 650         rustc_reservation_impl,
 651         rustc_test_marker,
 652         rustc_then_this_would_need,
 653         rustc_variance,
 654         rustfmt,
 655         rust_eh_personality,
 656         rust_eh_unwind_resume,
 657         rust_oom,
 658         rvalue_static_promotion,
 659         sanitize,
 660         sanitizer_runtime,
 661         saturating_add,
 662         saturating_sub,
 663         _Self,
 664         self_in_typedefs,
 665         self_struct_ctor,
 666         send_trait,
 667         should_panic,
 668         simd,
 669         simd_extract,
 670         simd_ffi,
 671         simd_insert,
 672         since,
 673         size,
 674         size_of,
 675         slice_patterns,
 676         slicing_syntax,
 677         soft,
 678         Some,
 679         specialization,
 680         speed,
 681         spotlight,
 682         sse4a_target_feature,
 683         stable,
 684         staged_api,
 685         start,
 686         static_in_const,
 687         staticlib,
 688         static_nobundle,
 689         static_recursion,
 690         std,
 691         std_inject,
 692         str,
 693         stringify,
 694         stmt,
 695         stmt_expr_attributes,
 696         stop_after_dataflow,
 697         struct_field_attributes,
 698         struct_inherit,
 699         structural_match,
 700         struct_variant,
 701         sty,
 702         sub_with_overflow,
 703         suggestion,
 704         sync_trait,
 705         target_feature,
 706         target_has_atomic,
 707         target_has_atomic_load_store,
 708         target_thread_local,
 709         task,
 710         tbm_target_feature,
 711         termination_trait,
 712         termination_trait_test,
 713         test,
 714         test_2018_feature,
 715         test_accepted_feature,
 716         test_case,
 717         test_removed_feature,
 718         test_runner,
 719         then_with,
 720         thread_local,
 721         tool_attributes,
 722         tool_lints,
 723         trace_macros,
 724         track_caller,
 725         trait_alias,
 726         transmute,
 727         transparent,
 728         transparent_enums,
 729         transparent_unions,
 730         trivial_bounds,
 731         Try,
 732         try_blocks,
 733         try_trait,
 734         tt,
 735         tuple_indexing,
 736         Ty,
 737         ty,
 738         type_alias_impl_trait,
 739         type_id,
 740         type_name,
 741         TyCtxt,
 742         TyKind,
 743         type_alias_enum_variants,
 744         type_ascription,
 745         type_length_limit,
 746         type_macros,
 747         u128,
 748         u16,
 749         u32,
 750         u64,
 751         u8,
 752         unboxed_closures,
 753         unchecked_shl,
 754         unchecked_shr,
 755         underscore_const_names,
 756         underscore_imports,
 757         underscore_lifetimes,
 758         uniform_paths,
 759         universal_impl_trait,
 760         unmarked_api,
 761         unreachable_code,
 762         unrestricted_attribute_tokens,
 763         unsafe_no_drop_flag,
 764         unsized_locals,
 765         unsized_tuple_coercion,
 766         unstable,
 767         untagged_unions,
 768         unwind,
 769         unwind_attributes,
 770         unwrap_or,
 771         used,
 772         use_extern_macros,
 773         use_nested_groups,
 774         usize,
 775         v1,
 776         val,
 777         var,
 778         vec,
 779         Vec,
 780         vis,
 781         visible_private_types,
 782         volatile,
 783         warn,
 784         wasm_import_module,
 785         wasm_target_feature,
 786         while_let,
 787         windows,
 788         windows_subsystem,
 789         wrapping_add,
 790         wrapping_sub,
 791         wrapping_mul,
 792         Yield,
 793     }
 794 }
 795
 796 #[derive(Copy, Clone, Eq, HashStable_Generic)]
 797 pub struct Ident {
 798     pub name: Symbol,
 799     pub span: Span,
 800 }
 801
 802 impl Ident {
 803     #[inline]
 804     /// Constructs a new identifier from a symbol and a span.
 805     pub const fn new(name: Symbol, span: Span) -> Ident {
 806         Ident { name, span }
 807     }
 808
 809     /// Constructs a new identifier with a dummy span.
 810     #[inline]
 811     pub const fn with_dummy_span(name: Symbol) -> Ident {
 812         Ident::new(name, DUMMY_SP)
 813     }
 814
 815     #[inline]
 816     pub fn invalid() -> Ident {
 817         Ident::with_dummy_span(kw::Invalid)
 818     }
 819
 820     /// Maps a string to an identifier with a dummy span.
 821     pub fn from_str(string: &str) -> Ident {
 822         Ident::with_dummy_span(Symbol::intern(string))
 823     }
 824
 825     /// Maps a string and a span to an identifier.
 826     pub fn from_str_and_span(string: &str, span: Span) -> Ident {
 827         Ident::new(Symbol::intern(string), span)
 828     }
 829
 830     /// Replaces `lo` and `hi` with those from `span`, but keep hygiene context.
 831     pub fn with_span_pos(self, span: Span) -> Ident {
 832         Ident::new(self.name, span.with_ctxt(self.span.ctxt()))
 833     }
 834
 835     pub fn without_first_quote(self) -> Ident {
 836         Ident::new(Symbol::intern(self.as_str().trim_start_matches('\'')), self.span)
 837     }
 838
 839     /// "Normalize" ident for use in comparisons using "item hygiene".
 840     /// Identifiers with same string value become same if they came from the same "modern" macro
 841     /// (e.g., `macro` item, but not `macro_rules` item) and stay different if they came from
 842     /// different "modern" macros.
 843     /// Technically, this operation strips all non-opaque marks from ident's syntactic context.
 844     pub fn modern(self) -> Ident {
 845         Ident::new(self.name, self.span.modern())
 846     }
 847
 848     /// "Normalize" ident for use in comparisons using "local variable hygiene".
 849     /// Identifiers with same string value become same if they came from the same non-transparent
 850     /// macro (e.g., `macro` or `macro_rules!` items) and stay different if they came from different
 851     /// non-transparent macros.
 852     /// Technically, this operation strips all transparent marks from ident's syntactic context.
 853     pub fn modern_and_legacy(self) -> Ident {
 854         Ident::new(self.name, self.span.modern_and_legacy())
 855     }
 856
 857     /// Convert the name to a `SymbolStr`. This is a slowish operation because
 858     /// it requires locking the symbol interner.
 859     pub fn as_str(self) -> SymbolStr {
 860         self.name.as_str()
 861     }
 862 }
 863
 864 impl PartialEq for Ident {
 865     fn eq(&self, rhs: &Self) -> bool {
 866         self.name == rhs.name && self.span.ctxt() == rhs.span.ctxt()
 867     }
 868 }
 869
 870 impl Hash for Ident {
 871     fn hash<H: Hasher>(&self, state: &mut H) {
 872         self.name.hash(state);
 873         self.span.ctxt().hash(state);
 874     }
 875 }
 876
 877 impl fmt::Debug for Ident {
 878     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 879         if self.is_raw_guess() {
 880             write!(f, "r#")?;
 881         }
 882         write!(f, "{}{:?}", self.name, self.span.ctxt())
 883     }
 884 }
 885
 886 impl fmt::Display for Ident {
 887     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 888         if self.is_raw_guess() {
 889             write!(f, "r#")?;
 890         }
 891         fmt::Display::fmt(&self.name, f)
 892     }
 893 }
 894
 895 impl UseSpecializedEncodable for Ident {
 896     fn default_encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
 897         s.emit_struct("Ident", 2, |s| {
 898             s.emit_struct_field("name", 0, |s| self.name.encode(s))?;
 899             s.emit_struct_field("span", 1, |s| self.span.encode(s))
 900         })
 901     }
 902 }
 903
 904 impl UseSpecializedDecodable for Ident {
 905     fn default_decode<D: Decoder>(d: &mut D) -> Result<Self, D::Error> {
 906         d.read_struct("Ident", 2, |d| {
 907             Ok(Ident {
 908                 name: d.read_struct_field("name", 0, Decodable::decode)?,
 909                 span: d.read_struct_field("span", 1, Decodable::decode)?,
 910             })
 911         })
 912     }
 913 }
 914
 915 /// An interned string.
 916 ///
 917 /// Internally, a `Symbol` is implemented as an index, and all operations
 918 /// (including hashing, equality, and ordering) operate on that index. The use
 919 /// of `rustc_index::newtype_index!` means that `Option<Symbol>` only takes up 4 bytes,
 920 /// because `rustc_index::newtype_index!` reserves the last 256 values for tagging purposes.
 921 ///
 922 /// Note that `Symbol` cannot directly be a `rustc_index::newtype_index!` because it
 923 /// implements `fmt::Debug`, `Encodable`, and `Decodable` in special ways.
 924 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
 925 pub struct Symbol(SymbolIndex);
 926
 927 rustc_index::newtype_index! {
 928     pub struct SymbolIndex { .. }
 929 }
 930
 931 impl Symbol {
 932     const fn new(n: u32) -> Self {
 933         Symbol(SymbolIndex::from_u32_const(n))
 934     }
 935
 936     /// Maps a string to its interned representation.
 937     pub fn intern(string: &str) -> Self {
 938         with_interner(|interner| interner.intern(string))
 939     }
 940
 941     /// Access the symbol's chars. This is a slowish operation because it
 942     /// requires locking the symbol interner.
 943     pub fn with<F: FnOnce(&str) -> R, R>(self, f: F) -> R {
 944         with_interner(|interner| f(interner.get(self)))
 945     }
 946
 947     /// Convert to a `SymbolStr`. This is a slowish operation because it
 948     /// requires locking the symbol interner.
 949     pub fn as_str(self) -> SymbolStr {
 950         with_interner(|interner| unsafe {
 951             SymbolStr { string: std::mem::transmute::<&str, &str>(interner.get(self)) }
 952         })
 953     }
 954
 955     pub fn as_u32(self) -> u32 {
 956         self.0.as_u32()
 957     }
 958 }
 959
 960 impl fmt::Debug for Symbol {
 961     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 962         self.with(|str| fmt::Debug::fmt(&str, f))
 963     }
 964 }
 965
 966 impl fmt::Display for Symbol {
 967     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 968         self.with(|str| fmt::Display::fmt(&str, f))
 969     }
 970 }
 971
 972 impl Encodable for Symbol {
 973     fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
 974         self.with(|string| s.emit_str(string))
 975     }
 976 }
 977
 978 impl Decodable for Symbol {
 979     fn decode<D: Decoder>(d: &mut D) -> Result<Symbol, D::Error> {
 980         Ok(Symbol::intern(&d.read_str()?))
 981     }
 982 }
 983
 984 impl<CTX> HashStable<CTX> for Symbol {
 985     #[inline]
 986     fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
 987         self.as_str().hash_stable(hcx, hasher);
 988     }
 989 }
 990
 991 impl<CTX> ToStableHashKey<CTX> for Symbol {
 992     type KeyType = SymbolStr;
 993
 994     #[inline]
 995     fn to_stable_hash_key(&self, _: &CTX) -> SymbolStr {
 996         self.as_str()
 997     }
 998 }
 999
1000 // The `&'static str`s in this type actually point into the arena.
1001 #[derive(Default)]
1002 pub struct Interner {
1003     arena: DroplessArena,
1004     names: FxHashMap<&'static str, Symbol>,
1005     strings: Vec<&'static str>,
1006 }
1007
1008 impl Interner {
1009     fn prefill(init: &[&'static str]) -> Self {
1010         Interner {
1011             strings: init.into(),
1012             names: init.iter().copied().zip((0..).map(Symbol::new)).collect(),
1013             ..Default::default()
1014         }
1015     }
1016
1017     pub fn intern(&mut self, string: &str) -> Symbol {
1018         if let Some(&name) = self.names.get(string) {
1019             return name;
1020         }
1021
1022         let name = Symbol::new(self.strings.len() as u32);
1023
1024         // `from_utf8_unchecked` is safe since we just allocated a `&str` which is known to be
1025         // UTF-8.
1026         let string: &str =
1027             unsafe { str::from_utf8_unchecked(self.arena.alloc_slice(string.as_bytes())) };
1028         // It is safe to extend the arena allocation to `'static` because we only access
1029         // these while the arena is still alive.
1030         let string: &'static str = unsafe { &*(string as *const str) };
1031         self.strings.push(string);
1032         self.names.insert(string, name);
1033         name
1034     }
1035
1036     // Get the symbol as a string. `Symbol::as_str()` should be used in
1037     // preference to this function.
1038     pub fn get(&self, symbol: Symbol) -> &str {
1039         self.strings[symbol.0.as_usize()]
1040     }
1041 }
1042
1043 // This module has a very short name because it's used a lot.
1044 pub mod kw {
1045     use super::Symbol;
1046     keywords!();
1047 }
1048
1049 // This module has a very short name because it's used a lot.
1050 pub mod sym {
1051     use super::Symbol;
1052     use std::convert::TryInto;
1053
1054     symbols!();
1055
1056     // Get the symbol for an integer. The first few non-negative integers each
1057     // have a static symbol and therefore are fast.
1058     pub fn integer<N: TryInto<usize> + Copy + ToString>(n: N) -> Symbol {
1059         if let Result::Ok(idx) = n.try_into() {
1060             if let Option::Some(&sym) = digits_array.get(idx) {
1061                 return sym;
1062             }
1063         }
1064         Symbol::intern(&n.to_string())
1065     }
1066 }
1067
1068 impl Symbol {
1069     fn is_used_keyword_2018(self) -> bool {
1070         self >= kw::Async && self <= kw::Dyn
1071     }
1072
1073     fn is_unused_keyword_2018(self) -> bool {
1074         self == kw::Try
1075     }
1076
1077     /// Used for sanity checking rustdoc keyword sections.
1078     pub fn is_doc_keyword(self) -> bool {
1079         self <= kw::Union
1080     }
1081
1082     /// A keyword or reserved identifier that can be used as a path segment.
1083     pub fn is_path_segment_keyword(self) -> bool {
1084         self == kw::Super
1085             || self == kw::SelfLower
1086             || self == kw::SelfUpper
1087             || self == kw::Crate
1088             || self == kw::PathRoot
1089             || self == kw::DollarCrate
1090     }
1091
1092     /// Returns `true` if the symbol is `true` or `false`.
1093     pub fn is_bool_lit(self) -> bool {
1094         self == kw::True || self == kw::False
1095     }
1096
1097     /// This symbol can be a raw identifier.
1098     pub fn can_be_raw(self) -> bool {
1099         self != kw::Invalid && self != kw::Underscore && !self.is_path_segment_keyword()
1100     }
1101 }
1102
1103 impl Ident {
1104     // Returns `true` for reserved identifiers used internally for elided lifetimes,
1105     // unnamed method parameters, crate root module, error recovery etc.
1106     pub fn is_special(self) -> bool {
1107         self.name <= kw::Underscore
1108     }
1109
1110     /// Returns `true` if the token is a keyword used in the language.
1111     pub fn is_used_keyword(self) -> bool {
1112         // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
1113         self.name >= kw::As && self.name <= kw::While
1114             || self.name.is_used_keyword_2018() && self.span.rust_2018()
1115     }
1116
1117     /// Returns `true` if the token is a keyword reserved for possible future use.
1118     pub fn is_unused_keyword(self) -> bool {
1119         // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
1120         self.name >= kw::Abstract && self.name <= kw::Yield
1121             || self.name.is_unused_keyword_2018() && self.span.rust_2018()
1122     }
1123
1124     /// Returns `true` if the token is either a special identifier or a keyword.
1125     pub fn is_reserved(self) -> bool {
1126         self.is_special() || self.is_used_keyword() || self.is_unused_keyword()
1127     }
1128
1129     /// A keyword or reserved identifier that can be used as a path segment.
1130     pub fn is_path_segment_keyword(self) -> bool {
1131         self.name.is_path_segment_keyword()
1132     }
1133
1134     /// We see this identifier in a normal identifier position, like variable name or a type.
1135     /// How was it written originally? Did it use the raw form? Let's try to guess.
1136     pub fn is_raw_guess(self) -> bool {
1137         self.name.can_be_raw() && self.is_reserved()
1138     }
1139 }
1140
1141 #[inline]
1142 fn with_interner<T, F: FnOnce(&mut Interner) -> T>(f: F) -> T {
1143     GLOBALS.with(|globals| f(&mut *globals.symbol_interner.lock()))
1144 }
1145
1146 /// An alternative to `Symbol`, useful when the chars within the symbol need to
1147 /// be accessed. It deliberately has limited functionality and should only be
1148 /// used for temporary values.
1149 ///
1150 /// Because the interner outlives any thread which uses this type, we can
1151 /// safely treat `string` which points to interner data, as an immortal string,
1152 /// as long as this type never crosses between threads.
1153 //
1154 // FIXME: ensure that the interner outlives any thread which uses `SymbolStr`,
1155 // by creating a new thread right after constructing the interner.
1156 #[derive(Clone, Eq, PartialOrd, Ord)]
1157 pub struct SymbolStr {
1158     string: &'static str,
1159 }
1160
1161 // This impl allows a `SymbolStr` to be directly equated with a `String` or
1162 // `&str`.
1163 impl<T: std::ops::Deref<Target = str>> std::cmp::PartialEq<T> for SymbolStr {
1164     fn eq(&self, other: &T) -> bool {
1165         self.string == other.deref()
1166     }
1167 }
1168
1169 impl !Send for SymbolStr {}
1170 impl !Sync for SymbolStr {}
1171
1172 /// This impl means that if `ss` is a `SymbolStr`:
1173 /// - `*ss` is a `str`;
1174 /// - `&*ss` is a `&str`;
1175 /// - `&ss as &str` is a `&str`, which means that `&ss` can be passed to a
1176 ///   function expecting a `&str`.
1177 impl std::ops::Deref for SymbolStr {
1178     type Target = str;
1179     #[inline]
1180     fn deref(&self) -> &str {
1181         self.string
1182     }
1183 }
1184
1185 impl fmt::Debug for SymbolStr {
1186     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1187         fmt::Debug::fmt(self.string, f)
1188     }
1189 }
1190
1191 impl fmt::Display for SymbolStr {
1192     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1193         fmt::Display::fmt(self.string, f)
1194     }
1195 }
1196
1197 impl<CTX> HashStable<CTX> for SymbolStr {
1198     #[inline]
1199     fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
1200         self.string.hash_stable(hcx, hasher)
1201     }
1202 }
1203
1204 impl<CTX> ToStableHashKey<CTX> for SymbolStr {
1205     type KeyType = SymbolStr;
1206
1207     #[inline]
1208     fn to_stable_hash_key(&self, _: &CTX) -> SymbolStr {
1209         self.clone()
1210     }
1211 }