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_macros::{symbols, HashStable_Generic};
   9 use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
  10 use rustc_serialize::{UseSpecializedDecodable, UseSpecializedEncodable};
  11
  12 use std::cmp::{Ord, PartialEq, PartialOrd};
  13 use std::fmt;
  14 use std::hash::{Hash, Hasher};
  15 use std::str;
  16
  17 use crate::{Span, DUMMY_SP, GLOBALS};
  18
  19 #[cfg(test)]
  20 mod tests;
  21
  22 symbols! {
  23     // After modifying this list adjust `is_special`, `is_used_keyword`/`is_unused_keyword`,
  24     // this should be rarely necessary though if the keywords are kept in alphabetic order.
  25     Keywords {
  26         // Special reserved identifiers used internally for elided lifetimes,
  27         // unnamed method parameters, crate root module, error recovery etc.
  28         Invalid:            "",
  29         PathRoot:           "{{root}}",
  30         DollarCrate:        "$crate",
  31         Underscore:         "_",
  32
  33         // Keywords that are used in stable Rust.
  34         As:                 "as",
  35         Break:              "break",
  36         Const:              "const",
  37         Continue:           "continue",
  38         Crate:              "crate",
  39         Else:               "else",
  40         Enum:               "enum",
  41         Extern:             "extern",
  42         False:              "false",
  43         Fn:                 "fn",
  44         For:                "for",
  45         If:                 "if",
  46         Impl:               "impl",
  47         In:                 "in",
  48         Let:                "let",
  49         Loop:               "loop",
  50         Match:              "match",
  51         Mod:                "mod",
  52         Move:               "move",
  53         Mut:                "mut",
  54         Pub:                "pub",
  55         Ref:                "ref",
  56         Return:             "return",
  57         SelfLower:          "self",
  58         SelfUpper:          "Self",
  59         Static:             "static",
  60         Struct:             "struct",
  61         Super:              "super",
  62         Trait:              "trait",
  63         True:               "true",
  64         Type:               "type",
  65         Unsafe:             "unsafe",
  66         Use:                "use",
  67         Where:              "where",
  68         While:              "while",
  69
  70         // Keywords that are used in unstable Rust or reserved for future use.
  71         Abstract:           "abstract",
  72         Become:             "become",
  73         Box:                "box",
  74         Do:                 "do",
  75         Final:              "final",
  76         Macro:              "macro",
  77         Override:           "override",
  78         Priv:               "priv",
  79         Typeof:             "typeof",
  80         Unsized:            "unsized",
  81         Virtual:            "virtual",
  82         Yield:              "yield",
  83
  84         // Edition-specific keywords that are used in stable Rust.
  85         Async:              "async", // >= 2018 Edition only
  86         Await:              "await", // >= 2018 Edition only
  87         Dyn:                "dyn", // >= 2018 Edition only
  88
  89         // Edition-specific keywords that are used in unstable Rust or reserved for future use.
  90         Try:                "try", // >= 2018 Edition only
  91
  92         // Special lifetime names
  93         UnderscoreLifetime: "'_",
  94         StaticLifetime:     "'static",
  95
  96         // Weak keywords, have special meaning only in specific contexts.
  97         Auto:               "auto",
  98         Catch:              "catch",
  99         Default:            "default",
 100         Raw:                "raw",
 101         Union:              "union",
 102     }
 103
 104     // Symbols that can be referred to with rustc_span::sym::*. The symbol is
 105     // the stringified identifier unless otherwise specified (e.g.
 106     // `proc_dash_macro` represents "proc-macro").
 107     //
 108     // As well as the symbols listed, there are symbols for the the strings
 109     // "0", "1", ..., "9", which are accessible via `sym::integer`.
 110     Symbols {
 111         aarch64_target_feature,
 112         abi,
 113         abi_amdgpu_kernel,
 114         abi_efiapi,
 115         abi_msp430_interrupt,
 116         abi_ptx,
 117         abi_sysv64,
 118         abi_thiscall,
 119         abi_unadjusted,
 120         abi_vectorcall,
 121         abi_x86_interrupt,
 122         aborts,
 123         add_with_overflow,
 124         advanced_slice_patterns,
 125         adx_target_feature,
 126         alias,
 127         align,
 128         alignstack,
 129         all,
 130         allocator,
 131         allocator_internals,
 132         alloc_error_handler,
 133         allow,
 134         allowed,
 135         allow_fail,
 136         allow_internal_unsafe,
 137         allow_internal_unstable,
 138         allow_internal_unstable_backcompat_hack,
 139         always,
 140         and,
 141         any,
 142         arbitrary_enum_discriminant,
 143         arbitrary_self_types,
 144         Arguments,
 145         ArgumentV1,
 146         arm_target_feature,
 147         asm,
 148         assert,
 149         associated_consts,
 150         associated_type_bounds,
 151         associated_type_defaults,
 152         associated_types,
 153         assume_init,
 154         async_await,
 155         async_closure,
 156         attr,
 157         attributes,
 158         attr_literals,
 159         augmented_assignments,
 160         automatically_derived,
 161         avx512_target_feature,
 162         await_macro,
 163         begin_panic,
 164         bench,
 165         bin,
 166         bind_by_move_pattern_guards,
 167         bindings_after_at,
 168         block,
 169         bool,
 170         borrowck_graphviz_format,
 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         const_trait_bound_opt_out,
 224         const_trait_impl,
 225         contents,
 226         context,
 227         convert,
 228         Copy,
 229         copy_closures,
 230         core,
 231         core_intrinsics,
 232         crate_id,
 233         crate_in_paths,
 234         crate_local,
 235         crate_name,
 236         crate_type,
 237         crate_visibility_modifier,
 238         ctpop,
 239         cttz,
 240         cttz_nonzero,
 241         ctlz,
 242         ctlz_nonzero,
 243         custom_attribute,
 244         custom_derive,
 245         custom_inner_attributes,
 246         custom_test_frameworks,
 247         c_variadic,
 248         debug_trait,
 249         declare_lint_pass,
 250         decl_macro,
 251         Debug,
 252         Decodable,
 253         Default,
 254         default_lib_allocator,
 255         default_type_parameter_fallback,
 256         default_type_params,
 257         delay_span_bug_from_inside_query,
 258         deny,
 259         deprecated,
 260         deref,
 261         deref_mut,
 262         derive,
 263         diagnostic,
 264         direct,
 265         doc,
 266         doc_alias,
 267         doc_cfg,
 268         doc_keyword,
 269         doc_masked,
 270         doc_spotlight,
 271         doctest,
 272         document_private_items,
 273         dotdoteq_in_patterns,
 274         dotdot_in_tuple_patterns,
 275         double_braced_crate: "{{crate}}",
 276         double_braced_impl: "{{impl}}",
 277         double_braced_misc: "{{misc}}",
 278         double_braced_closure: "{{closure}}",
 279         double_braced_constructor: "{{constructor}}",
 280         double_braced_constant: "{{constant}}",
 281         double_braced_opaque: "{{opaque}}",
 282         dropck_eyepatch,
 283         dropck_parametricity,
 284         drop_types_in_const,
 285         dylib,
 286         dyn_trait,
 287         eh_personality,
 288         eh_unwind_resume,
 289         enable,
 290         Encodable,
 291         env,
 292         eq,
 293         err,
 294         Err,
 295         Eq,
 296         Equal,
 297         enclosing_scope,
 298         except,
 299         exclusive_range_pattern,
 300         exhaustive_integer_patterns,
 301         exhaustive_patterns,
 302         existential_type,
 303         expected,
 304         export_name,
 305         expr,
 306         extern_absolute_paths,
 307         external_doc,
 308         extern_crate_item_prelude,
 309         extern_crate_self,
 310         extern_in_paths,
 311         extern_prelude,
 312         extern_types,
 313         f16c_target_feature,
 314         f32,
 315         f64,
 316         feature,
 317         ffi_returns_twice,
 318         field,
 319         field_init_shorthand,
 320         file,
 321         fmt,
 322         fmt_internals,
 323         fn_must_use,
 324         forbid,
 325         format_args,
 326         format_args_nl,
 327         from,
 328         From,
 329         from_desugaring,
 330         from_error,
 331         from_generator,
 332         from_method,
 333         from_ok,
 334         from_usize,
 335         fundamental,
 336         future,
 337         Future,
 338         FxHashSet,
 339         FxHashMap,
 340         gen_future,
 341         gen_kill,
 342         generators,
 343         generic_associated_types,
 344         generic_param_attrs,
 345         global_allocator,
 346         global_asm,
 347         globs,
 348         half_open_range_patterns,
 349         hash,
 350         Hash,
 351         HashSet,
 352         HashMap,
 353         hexagon_target_feature,
 354         hidden,
 355         homogeneous_aggregate,
 356         html_favicon_url,
 357         html_logo_url,
 358         html_no_source,
 359         html_playground_url,
 360         html_root_url,
 361         i128,
 362         i128_type,
 363         i16,
 364         i32,
 365         i64,
 366         i8,
 367         ident,
 368         if_let,
 369         if_while_or_patterns,
 370         ignore,
 371         impl_header_lifetime_elision,
 372         impl_lint_pass,
 373         impl_trait_in_bindings,
 374         import_shadowing,
 375         index,
 376         index_mut,
 377         in_band_lifetimes,
 378         include,
 379         include_bytes,
 380         include_str,
 381         inclusive_range_syntax,
 382         infer_outlives_requirements,
 383         infer_static_outlives_requirements,
 384         inline,
 385         intel,
 386         into_iter,
 387         IntoIterator,
 388         into_result,
 389         intrinsics,
 390         irrefutable_let_patterns,
 391         isize,
 392         issue,
 393         issue_5723_bootstrap,
 394         issue_tracker_base_url,
 395         item,
 396         item_context: "ItemContext",
 397         item_like_imports,
 398         iter,
 399         Iterator,
 400         keyword,
 401         kind,
 402         label,
 403         label_break_value,
 404         lang,
 405         lang_items,
 406         let_chains,
 407         lhs,
 408         lib,
 409         lifetime,
 410         line,
 411         link,
 412         linkage,
 413         link_args,
 414         link_cfg,
 415         link_llvm_intrinsics,
 416         link_name,
 417         link_ordinal,
 418         link_section,
 419         LintPass,
 420         lint_reasons,
 421         literal,
 422         local_inner_macros,
 423         log_syntax,
 424         loop_break_value,
 425         macro_at_most_once_rep,
 426         macro_escape,
 427         macro_export,
 428         macro_lifetime_matcher,
 429         macro_literal_matcher,
 430         macro_reexport,
 431         macro_rules,
 432         macros_in_extern,
 433         macro_use,
 434         macro_vis_matcher,
 435         main,
 436         managed_boxes,
 437         marker,
 438         marker_trait_attr,
 439         masked,
 440         match_beginning_vert,
 441         match_default_bindings,
 442         may_dangle,
 443         maybe_uninit_uninit,
 444         maybe_uninit_zeroed,
 445         mem_uninitialized,
 446         mem_zeroed,
 447         member_constraints,
 448         message,
 449         meta,
 450         min_align_of,
 451         min_const_fn,
 452         min_const_unsafe_fn,
 453         mips_target_feature,
 454         mmx_target_feature,
 455         module,
 456         module_path,
 457         more_struct_aliases,
 458         move_ref_pattern,
 459         move_val_init,
 460         movbe_target_feature,
 461         mul_with_overflow,
 462         must_use,
 463         naked,
 464         naked_functions,
 465         name,
 466         needs_allocator,
 467         needs_drop,
 468         needs_panic_runtime,
 469         negate_unsigned,
 470         never,
 471         never_type,
 472         never_type_fallback,
 473         new,
 474         next,
 475         __next,
 476         nll,
 477         no_builtins,
 478         no_core,
 479         no_crate_inject,
 480         no_debug,
 481         no_default_passes,
 482         no_implicit_prelude,
 483         no_inline,
 484         no_link,
 485         no_main,
 486         no_mangle,
 487         non_ascii_idents,
 488         None,
 489         non_exhaustive,
 490         non_modrs_mods,
 491         no_stack_check,
 492         no_start,
 493         no_std,
 494         not,
 495         note,
 496         object_safe_for_dispatch,
 497         Ok,
 498         omit_gdb_pretty_printer_section,
 499         on,
 500         on_unimplemented,
 501         oom,
 502         ops,
 503         optimize,
 504         optimize_attribute,
 505         optin_builtin_traits,
 506         option,
 507         Option,
 508         option_env,
 509         opt_out_copy,
 510         or,
 511         or_patterns,
 512         Ord,
 513         Ordering,
 514         Output,
 515         overlapping_marker_traits,
 516         packed,
 517         panic,
 518         panic_handler,
 519         panic_impl,
 520         panic_implementation,
 521         panic_runtime,
 522         parent_trait,
 523         partial_cmp,
 524         param_attrs,
 525         PartialEq,
 526         PartialOrd,
 527         passes,
 528         pat,
 529         path,
 530         pattern_parentheses,
 531         Pending,
 532         pin,
 533         Pin,
 534         pinned,
 535         platform_intrinsics,
 536         plugin,
 537         plugin_registrar,
 538         plugins,
 539         Poll,
 540         poll_with_tls_context,
 541         powerpc_target_feature,
 542         precise_pointer_size_matching,
 543         pref_align_of,
 544         prelude,
 545         prelude_import,
 546         primitive,
 547         proc_dash_macro: "proc-macro",
 548         proc_macro,
 549         proc_macro_attribute,
 550         proc_macro_def_site,
 551         proc_macro_derive,
 552         proc_macro_expr,
 553         proc_macro_gen,
 554         proc_macro_hygiene,
 555         proc_macro_internals,
 556         proc_macro_mod,
 557         proc_macro_non_items,
 558         proc_macro_path_invoc,
 559         profiler_runtime,
 560         ptr_offset_from,
 561         pub_restricted,
 562         pushpop_unsafe,
 563         quad_precision_float,
 564         question_mark,
 565         quote,
 566         Range,
 567         RangeFrom,
 568         RangeFull,
 569         RangeInclusive,
 570         RangeTo,
 571         RangeToInclusive,
 572         raw_dylib,
 573         raw_identifiers,
 574         raw_ref_op,
 575         Ready,
 576         reason,
 577         recursion_limit,
 578         reexport_test_harness_main,
 579         reflect,
 580         register_attr,
 581         register_tool,
 582         relaxed_adts,
 583         repr,
 584         repr128,
 585         repr_align,
 586         repr_align_enum,
 587         repr_packed,
 588         repr_simd,
 589         repr_transparent,
 590         re_rebalance_coherence,
 591         result,
 592         Result,
 593         Return,
 594         rhs,
 595         rlib,
 596         rotate_left,
 597         rotate_right,
 598         rt,
 599         rtm_target_feature,
 600         rust,
 601         rust_2015_preview,
 602         rust_2018_preview,
 603         rust_begin_unwind,
 604         rustc,
 605         RustcDecodable,
 606         RustcEncodable,
 607         rustc_allocator,
 608         rustc_allocator_nounwind,
 609         rustc_allow_const_fn_ptr,
 610         rustc_args_required_const,
 611         rustc_attrs,
 612         rustc_builtin_macro,
 613         rustc_clean,
 614         rustc_const_unstable,
 615         rustc_const_stable,
 616         rustc_conversion_suggestion,
 617         rustc_def_path,
 618         rustc_deprecated,
 619         rustc_diagnostic_item,
 620         rustc_diagnostic_macros,
 621         rustc_dirty,
 622         rustc_dummy,
 623         rustc_dump_env_program_clauses,
 624         rustc_dump_program_clauses,
 625         rustc_dump_user_substs,
 626         rustc_error,
 627         rustc_expected_cgu_reuse,
 628         rustc_if_this_changed,
 629         rustc_inherit_overflow_checks,
 630         rustc_layout,
 631         rustc_layout_scalar_valid_range_end,
 632         rustc_layout_scalar_valid_range_start,
 633         rustc_macro_transparency,
 634         rustc_mir,
 635         rustc_nonnull_optimization_guaranteed,
 636         rustc_object_lifetime_default,
 637         rustc_on_unimplemented,
 638         rustc_outlives,
 639         rustc_paren_sugar,
 640         rustc_partition_codegened,
 641         rustc_partition_reused,
 642         rustc_peek,
 643         rustc_peek_definite_init,
 644         rustc_peek_maybe_init,
 645         rustc_peek_maybe_uninit,
 646         rustc_peek_indirectly_mutable,
 647         rustc_private,
 648         rustc_proc_macro_decls,
 649         rustc_promotable,
 650         rustc_regions,
 651         rustc_stable,
 652         rustc_std_internal_symbol,
 653         rustc_symbol_name,
 654         rustc_synthetic,
 655         rustc_reservation_impl,
 656         rustc_test_marker,
 657         rustc_then_this_would_need,
 658         rustc_variance,
 659         rustfmt,
 660         rust_eh_personality,
 661         rust_eh_unwind_resume,
 662         rust_oom,
 663         rvalue_static_promotion,
 664         sanitize,
 665         sanitizer_runtime,
 666         saturating_add,
 667         saturating_sub,
 668         _Self,
 669         self_in_typedefs,
 670         self_struct_ctor,
 671         send_trait,
 672         should_panic,
 673         simd,
 674         simd_extract,
 675         simd_ffi,
 676         simd_insert,
 677         since,
 678         size,
 679         size_of,
 680         slice_patterns,
 681         slicing_syntax,
 682         soft,
 683         Some,
 684         specialization,
 685         speed,
 686         spotlight,
 687         sse4a_target_feature,
 688         stable,
 689         staged_api,
 690         start,
 691         static_in_const,
 692         staticlib,
 693         static_nobundle,
 694         static_recursion,
 695         std,
 696         std_inject,
 697         str,
 698         stringify,
 699         stmt,
 700         stmt_expr_attributes,
 701         stop_after_dataflow,
 702         struct_field_attributes,
 703         struct_inherit,
 704         structural_match,
 705         struct_variant,
 706         sty,
 707         sub_with_overflow,
 708         suggestion,
 709         sync_trait,
 710         target_feature,
 711         target_has_atomic,
 712         target_has_atomic_load_store,
 713         target_thread_local,
 714         task,
 715         tbm_target_feature,
 716         termination_trait,
 717         termination_trait_test,
 718         test,
 719         test_2018_feature,
 720         test_accepted_feature,
 721         test_case,
 722         test_removed_feature,
 723         test_runner,
 724         then_with,
 725         thread_local,
 726         tool_attributes,
 727         tool_lints,
 728         trace_macros,
 729         track_caller,
 730         trait_alias,
 731         transmute,
 732         transparent,
 733         transparent_enums,
 734         transparent_unions,
 735         trivial_bounds,
 736         Try,
 737         try_blocks,
 738         try_trait,
 739         tt,
 740         tuple_indexing,
 741         two_phase,
 742         Ty,
 743         ty,
 744         type_alias_impl_trait,
 745         type_id,
 746         type_name,
 747         TyCtxt,
 748         TyKind,
 749         type_alias_enum_variants,
 750         type_ascription,
 751         type_length_limit,
 752         type_macros,
 753         u128,
 754         u16,
 755         u32,
 756         u64,
 757         u8,
 758         unboxed_closures,
 759         unchecked_shl,
 760         unchecked_shr,
 761         underscore_const_names,
 762         underscore_imports,
 763         underscore_lifetimes,
 764         uniform_paths,
 765         universal_impl_trait,
 766         unmarked_api,
 767         unreachable_code,
 768         unrestricted_attribute_tokens,
 769         unsafe_no_drop_flag,
 770         unsized_locals,
 771         unsized_tuple_coercion,
 772         unstable,
 773         untagged_unions,
 774         unwind,
 775         unwind_attributes,
 776         unwrap_or,
 777         used,
 778         use_extern_macros,
 779         use_nested_groups,
 780         usize,
 781         v1,
 782         val,
 783         var,
 784         vec,
 785         Vec,
 786         vis,
 787         visible_private_types,
 788         volatile,
 789         warn,
 790         wasm_import_module,
 791         wasm_target_feature,
 792         while_let,
 793         windows,
 794         windows_subsystem,
 795         wrapping_add,
 796         wrapping_sub,
 797         wrapping_mul,
 798         Yield,
 799     }
 800 }
 801
 802 #[derive(Copy, Clone, Eq, HashStable_Generic)]
 803 pub struct Ident {
 804     pub name: Symbol,
 805     pub span: Span,
 806 }
 807
 808 impl Ident {
 809     #[inline]
 810     /// Constructs a new identifier from a symbol and a span.
 811     pub const fn new(name: Symbol, span: Span) -> Ident {
 812         Ident { name, span }
 813     }
 814
 815     /// Constructs a new identifier with a dummy span.
 816     #[inline]
 817     pub const fn with_dummy_span(name: Symbol) -> Ident {
 818         Ident::new(name, DUMMY_SP)
 819     }
 820
 821     #[inline]
 822     pub fn invalid() -> Ident {
 823         Ident::with_dummy_span(kw::Invalid)
 824     }
 825
 826     /// Maps a string to an identifier with a dummy span.
 827     pub fn from_str(string: &str) -> Ident {
 828         Ident::with_dummy_span(Symbol::intern(string))
 829     }
 830
 831     /// Maps a string and a span to an identifier.
 832     pub fn from_str_and_span(string: &str, span: Span) -> Ident {
 833         Ident::new(Symbol::intern(string), span)
 834     }
 835
 836     /// Replaces `lo` and `hi` with those from `span`, but keep hygiene context.
 837     pub fn with_span_pos(self, span: Span) -> Ident {
 838         Ident::new(self.name, span.with_ctxt(self.span.ctxt()))
 839     }
 840
 841     pub fn without_first_quote(self) -> Ident {
 842         Ident::new(Symbol::intern(self.as_str().trim_start_matches('\'')), self.span)
 843     }
 844
 845     /// "Normalize" ident for use in comparisons using "item hygiene".
 846     /// Identifiers with same string value become same if they came from the same "modern" macro
 847     /// (e.g., `macro` item, but not `macro_rules` item) and stay different if they came from
 848     /// different "modern" macros.
 849     /// Technically, this operation strips all non-opaque marks from ident's syntactic context.
 850     pub fn modern(self) -> Ident {
 851         Ident::new(self.name, self.span.modern())
 852     }
 853
 854     /// "Normalize" ident for use in comparisons using "local variable hygiene".
 855     /// Identifiers with same string value become same if they came from the same non-transparent
 856     /// macro (e.g., `macro` or `macro_rules!` items) and stay different if they came from different
 857     /// non-transparent macros.
 858     /// Technically, this operation strips all transparent marks from ident's syntactic context.
 859     pub fn modern_and_legacy(self) -> Ident {
 860         Ident::new(self.name, self.span.modern_and_legacy())
 861     }
 862
 863     /// Convert the name to a `SymbolStr`. This is a slowish operation because
 864     /// it requires locking the symbol interner.
 865     pub fn as_str(self) -> SymbolStr {
 866         self.name.as_str()
 867     }
 868 }
 869
 870 impl PartialEq for Ident {
 871     fn eq(&self, rhs: &Self) -> bool {
 872         self.name == rhs.name && self.span.ctxt() == rhs.span.ctxt()
 873     }
 874 }
 875
 876 impl Hash for Ident {
 877     fn hash<H: Hasher>(&self, state: &mut H) {
 878         self.name.hash(state);
 879         self.span.ctxt().hash(state);
 880     }
 881 }
 882
 883 impl fmt::Debug for Ident {
 884     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 885         if self.is_raw_guess() {
 886             write!(f, "r#")?;
 887         }
 888         write!(f, "{}{:?}", self.name, self.span.ctxt())
 889     }
 890 }
 891
 892 impl fmt::Display for Ident {
 893     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 894         if self.is_raw_guess() {
 895             write!(f, "r#")?;
 896         }
 897         fmt::Display::fmt(&self.name, f)
 898     }
 899 }
 900
 901 impl UseSpecializedEncodable for Ident {
 902     fn default_encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
 903         s.emit_struct("Ident", 2, |s| {
 904             s.emit_struct_field("name", 0, |s| self.name.encode(s))?;
 905             s.emit_struct_field("span", 1, |s| self.span.encode(s))
 906         })
 907     }
 908 }
 909
 910 impl UseSpecializedDecodable for Ident {
 911     fn default_decode<D: Decoder>(d: &mut D) -> Result<Self, D::Error> {
 912         d.read_struct("Ident", 2, |d| {
 913             Ok(Ident {
 914                 name: d.read_struct_field("name", 0, Decodable::decode)?,
 915                 span: d.read_struct_field("span", 1, Decodable::decode)?,
 916             })
 917         })
 918     }
 919 }
 920
 921 /// An interned string.
 922 ///
 923 /// Internally, a `Symbol` is implemented as an index, and all operations
 924 /// (including hashing, equality, and ordering) operate on that index. The use
 925 /// of `rustc_index::newtype_index!` means that `Option<Symbol>` only takes up 4 bytes,
 926 /// because `rustc_index::newtype_index!` reserves the last 256 values for tagging purposes.
 927 ///
 928 /// Note that `Symbol` cannot directly be a `rustc_index::newtype_index!` because it
 929 /// implements `fmt::Debug`, `Encodable`, and `Decodable` in special ways.
 930 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
 931 pub struct Symbol(SymbolIndex);
 932
 933 rustc_index::newtype_index! {
 934     pub struct SymbolIndex { .. }
 935 }
 936
 937 impl Symbol {
 938     const fn new(n: u32) -> Self {
 939         Symbol(SymbolIndex::from_u32_const(n))
 940     }
 941
 942     /// Maps a string to its interned representation.
 943     pub fn intern(string: &str) -> Self {
 944         with_interner(|interner| interner.intern(string))
 945     }
 946
 947     /// Access the symbol's chars. This is a slowish operation because it
 948     /// requires locking the symbol interner.
 949     pub fn with<F: FnOnce(&str) -> R, R>(self, f: F) -> R {
 950         with_interner(|interner| f(interner.get(self)))
 951     }
 952
 953     /// Convert to a `SymbolStr`. This is a slowish operation because it
 954     /// requires locking the symbol interner.
 955     pub fn as_str(self) -> SymbolStr {
 956         with_interner(|interner| unsafe {
 957             SymbolStr { string: std::mem::transmute::<&str, &str>(interner.get(self)) }
 958         })
 959     }
 960
 961     pub fn as_u32(self) -> u32 {
 962         self.0.as_u32()
 963     }
 964 }
 965
 966 impl fmt::Debug for Symbol {
 967     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 968         self.with(|str| fmt::Debug::fmt(&str, f))
 969     }
 970 }
 971
 972 impl fmt::Display for Symbol {
 973     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 974         self.with(|str| fmt::Display::fmt(&str, f))
 975     }
 976 }
 977
 978 impl Encodable for Symbol {
 979     fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
 980         self.with(|string| s.emit_str(string))
 981     }
 982 }
 983
 984 impl Decodable for Symbol {
 985     fn decode<D: Decoder>(d: &mut D) -> Result<Symbol, D::Error> {
 986         Ok(Symbol::intern(&d.read_str()?))
 987     }
 988 }
 989
 990 impl<CTX> HashStable<CTX> for Symbol {
 991     #[inline]
 992     fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
 993         self.as_str().hash_stable(hcx, hasher);
 994     }
 995 }
 996
 997 impl<CTX> ToStableHashKey<CTX> for Symbol {
 998     type KeyType = SymbolStr;
 999
1000     #[inline]
1001     fn to_stable_hash_key(&self, _: &CTX) -> SymbolStr {
1002         self.as_str()
1003     }
1004 }
1005
1006 // The `&'static str`s in this type actually point into the arena.
1007 #[derive(Default)]
1008 pub struct Interner {
1009     arena: DroplessArena,
1010     names: FxHashMap<&'static str, Symbol>,
1011     strings: Vec<&'static str>,
1012 }
1013
1014 impl Interner {
1015     fn prefill(init: &[&'static str]) -> Self {
1016         Interner {
1017             strings: init.into(),
1018             names: init.iter().copied().zip((0..).map(Symbol::new)).collect(),
1019             ..Default::default()
1020         }
1021     }
1022
1023     pub fn intern(&mut self, string: &str) -> Symbol {
1024         if let Some(&name) = self.names.get(string) {
1025             return name;
1026         }
1027
1028         let name = Symbol::new(self.strings.len() as u32);
1029
1030         // `from_utf8_unchecked` is safe since we just allocated a `&str` which is known to be
1031         // UTF-8.
1032         let string: &str =
1033             unsafe { str::from_utf8_unchecked(self.arena.alloc_slice(string.as_bytes())) };
1034         // It is safe to extend the arena allocation to `'static` because we only access
1035         // these while the arena is still alive.
1036         let string: &'static str = unsafe { &*(string as *const str) };
1037         self.strings.push(string);
1038         self.names.insert(string, name);
1039         name
1040     }
1041
1042     // Get the symbol as a string. `Symbol::as_str()` should be used in
1043     // preference to this function.
1044     pub fn get(&self, symbol: Symbol) -> &str {
1045         self.strings[symbol.0.as_usize()]
1046     }
1047 }
1048
1049 // This module has a very short name because it's used a lot.
1050 pub mod kw {
1051     use super::Symbol;
1052     keywords!();
1053 }
1054
1055 // This module has a very short name because it's used a lot.
1056 #[allow(rustc::default_hash_types)]
1057 pub mod sym {
1058     use super::Symbol;
1059     use std::convert::TryInto;
1060
1061     symbols!();
1062
1063     // Get the symbol for an integer. The first few non-negative integers each
1064     // have a static symbol and therefore are fast.
1065     pub fn integer<N: TryInto<usize> + Copy + ToString>(n: N) -> Symbol {
1066         if let Result::Ok(idx) = n.try_into() {
1067             if let Option::Some(&sym) = digits_array.get(idx) {
1068                 return sym;
1069             }
1070         }
1071         Symbol::intern(&n.to_string())
1072     }
1073 }
1074
1075 impl Symbol {
1076     fn is_used_keyword_2018(self) -> bool {
1077         self >= kw::Async && self <= kw::Dyn
1078     }
1079
1080     fn is_unused_keyword_2018(self) -> bool {
1081         self == kw::Try
1082     }
1083
1084     /// Used for sanity checking rustdoc keyword sections.
1085     pub fn is_doc_keyword(self) -> bool {
1086         self <= kw::Union
1087     }
1088
1089     /// A keyword or reserved identifier that can be used as a path segment.
1090     pub fn is_path_segment_keyword(self) -> bool {
1091         self == kw::Super
1092             || self == kw::SelfLower
1093             || self == kw::SelfUpper
1094             || self == kw::Crate
1095             || self == kw::PathRoot
1096             || self == kw::DollarCrate
1097     }
1098
1099     /// Returns `true` if the symbol is `true` or `false`.
1100     pub fn is_bool_lit(self) -> bool {
1101         self == kw::True || self == kw::False
1102     }
1103
1104     /// This symbol can be a raw identifier.
1105     pub fn can_be_raw(self) -> bool {
1106         self != kw::Invalid && self != kw::Underscore && !self.is_path_segment_keyword()
1107     }
1108 }
1109
1110 impl Ident {
1111     // Returns `true` for reserved identifiers used internally for elided lifetimes,
1112     // unnamed method parameters, crate root module, error recovery etc.
1113     pub fn is_special(self) -> bool {
1114         self.name <= kw::Underscore
1115     }
1116
1117     /// Returns `true` if the token is a keyword used in the language.
1118     pub fn is_used_keyword(self) -> bool {
1119         // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
1120         self.name >= kw::As && self.name <= kw::While
1121             || self.name.is_used_keyword_2018() && self.span.rust_2018()
1122     }
1123
1124     /// Returns `true` if the token is a keyword reserved for possible future use.
1125     pub fn is_unused_keyword(self) -> bool {
1126         // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
1127         self.name >= kw::Abstract && self.name <= kw::Yield
1128             || self.name.is_unused_keyword_2018() && self.span.rust_2018()
1129     }
1130
1131     /// Returns `true` if the token is either a special identifier or a keyword.
1132     pub fn is_reserved(self) -> bool {
1133         self.is_special() || self.is_used_keyword() || self.is_unused_keyword()
1134     }
1135
1136     /// A keyword or reserved identifier that can be used as a path segment.
1137     pub fn is_path_segment_keyword(self) -> bool {
1138         self.name.is_path_segment_keyword()
1139     }
1140
1141     /// We see this identifier in a normal identifier position, like variable name or a type.
1142     /// How was it written originally? Did it use the raw form? Let's try to guess.
1143     pub fn is_raw_guess(self) -> bool {
1144         self.name.can_be_raw() && self.is_reserved()
1145     }
1146 }
1147
1148 #[inline]
1149 fn with_interner<T, F: FnOnce(&mut Interner) -> T>(f: F) -> T {
1150     GLOBALS.with(|globals| f(&mut *globals.symbol_interner.lock()))
1151 }
1152
1153 /// An alternative to `Symbol`, useful when the chars within the symbol need to
1154 /// be accessed. It deliberately has limited functionality and should only be
1155 /// used for temporary values.
1156 ///
1157 /// Because the interner outlives any thread which uses this type, we can
1158 /// safely treat `string` which points to interner data, as an immortal string,
1159 /// as long as this type never crosses between threads.
1160 //
1161 // FIXME: ensure that the interner outlives any thread which uses `SymbolStr`,
1162 // by creating a new thread right after constructing the interner.
1163 #[derive(Clone, Eq, PartialOrd, Ord)]
1164 pub struct SymbolStr {
1165     string: &'static str,
1166 }
1167
1168 // This impl allows a `SymbolStr` to be directly equated with a `String` or
1169 // `&str`.
1170 impl<T: std::ops::Deref<Target = str>> std::cmp::PartialEq<T> for SymbolStr {
1171     fn eq(&self, other: &T) -> bool {
1172         self.string == other.deref()
1173     }
1174 }
1175
1176 impl !Send for SymbolStr {}
1177 impl !Sync for SymbolStr {}
1178
1179 /// This impl means that if `ss` is a `SymbolStr`:
1180 /// - `*ss` is a `str`;
1181 /// - `&*ss` is a `&str`;
1182 /// - `&ss as &str` is a `&str`, which means that `&ss` can be passed to a
1183 ///   function expecting a `&str`.
1184 impl std::ops::Deref for SymbolStr {
1185     type Target = str;
1186     #[inline]
1187     fn deref(&self) -> &str {
1188         self.string
1189     }
1190 }
1191
1192 impl fmt::Debug for SymbolStr {
1193     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1194         fmt::Debug::fmt(self.string, f)
1195     }
1196 }
1197
1198 impl fmt::Display for SymbolStr {
1199     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1200         fmt::Display::fmt(self.string, f)
1201     }
1202 }
1203
1204 impl<CTX> HashStable<CTX> for SymbolStr {
1205     #[inline]
1206     fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
1207         self.string.hash_stable(hcx, hasher)
1208     }
1209 }
1210
1211 impl<CTX> ToStableHashKey<CTX> for SymbolStr {
1212     type KeyType = SymbolStr;
1213
1214     #[inline]
1215     fn to_stable_hash_key(&self, _: &CTX) -> SymbolStr {
1216         self.clone()
1217     }
1218 }