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 rustc_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, SESSION_GLOBALS};
  18
  19 #[cfg(test)]
  20 mod tests;
  21
  22 // The proc macro code for this is in `src/librustc_macros/src/symbols.rs`.
  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         MacroRules:         "macro_rules",
 102         Raw:                "raw",
 103         Union:              "union",
 104     }
 105
 106     // Pre-interned symbols that can be referred to with `rustc_span::sym::*`.
 107     //
 108     // The symbol is the stringified identifier unless otherwise specified, in
 109     // which case the name should mention the non-identifier punctuation.
 110     // E.g. `sym::proc_dash_macro` represents "proc-macro", and it shouldn't be
 111     // called `sym::proc_macro` because then it's easy to mistakenly think it
 112     // represents "proc_macro".
 113     //
 114     // As well as the symbols listed, there are symbols for the the strings
 115     // "0", "1", ..., "9", which are accessible via `sym::integer`.
 116     //
 117     // The proc macro will abort if symbols are not in alphabetical order (as
 118     // defined by `impl Ord for str`) or if any symbols are duplicated. Vim
 119     // users can sort the list by selecting it and executing the command
 120     // `:'<,'>!LC_ALL=C sort`.
 121     //
 122     // There is currently no checking that all symbols are used; that would be
 123     // nice to have.
 124     Symbols {
 125         Alignment,
 126         Arc,
 127         Argument,
 128         ArgumentV1,
 129         Arguments,
 130         C,
 131         Center,
 132         Clone,
 133         Copy,
 134         Count,
 135         Debug,
 136         Decodable,
 137         Decoder,
 138         Default,
 139         Encodable,
 140         Encoder,
 141         Eq,
 142         Equal,
 143         Err,
 144         Error,
 145         FormatSpec,
 146         Formatter,
 147         From,
 148         Future,
 149         FxHashMap,
 150         FxHashSet,
 151         GlobalAlloc,
 152         Hash,
 153         HashMap,
 154         HashSet,
 155         Hasher,
 156         Implied,
 157         Input,
 158         IntoIterator,
 159         Is,
 160         ItemContext,
 161         Iterator,
 162         Layout,
 163         Left,
 164         LintPass,
 165         None,
 166         Ok,
 167         Option,
 168         Ord,
 169         Ordering,
 170         Output,
 171         Param,
 172         PartialEq,
 173         PartialOrd,
 174         Pending,
 175         Pin,
 176         Poll,
 177         ProcMacro,
 178         ProcMacroHack,
 179         ProceduralMasqueradeDummyType,
 180         Range,
 181         RangeFrom,
 182         RangeFull,
 183         RangeInclusive,
 184         RangeTo,
 185         RangeToInclusive,
 186         Rc,
 187         Ready,
 188         Result,
 189         Return,
 190         Right,
 191         RustcDecodable,
 192         RustcEncodable,
 193         Send,
 194         Some,
 195         StructuralEq,
 196         StructuralPartialEq,
 197         Sync,
 198         Target,
 199         Try,
 200         Ty,
 201         TyCtxt,
 202         TyKind,
 203         Unknown,
 204         Vec,
 205         Yield,
 206         _DECLS,
 207         _Self,
 208         __D,
 209         __H,
 210         __S,
 211         __next,
 212         __try_var,
 213         _d,
 214         _e,
 215         _task_context,
 216         aarch64_target_feature,
 217         abi,
 218         abi_amdgpu_kernel,
 219         abi_avr_interrupt,
 220         abi_efiapi,
 221         abi_msp430_interrupt,
 222         abi_ptx,
 223         abi_sysv64,
 224         abi_thiscall,
 225         abi_unadjusted,
 226         abi_vectorcall,
 227         abi_x86_interrupt,
 228         abort,
 229         aborts,
 230         add,
 231         add_assign,
 232         add_with_overflow,
 233         address,
 234         advanced_slice_patterns,
 235         adx_target_feature,
 236         alias,
 237         align,
 238         align_offset,
 239         alignstack,
 240         all,
 241         alloc,
 242         alloc_error_handler,
 243         alloc_layout,
 244         alloc_zeroed,
 245         allocator,
 246         allocator_internals,
 247         allow,
 248         allow_fail,
 249         allow_internal_unsafe,
 250         allow_internal_unstable,
 251         allow_internal_unstable_backcompat_hack,
 252         allowed,
 253         always,
 254         and,
 255         and_then,
 256         any,
 257         arbitrary_enum_discriminant,
 258         arbitrary_self_types,
 259         arith_offset,
 260         arm_target_feature,
 261         array,
 262         as_str,
 263         asm,
 264         assert,
 265         assert_inhabited,
 266         assert_receiver_is_total_eq,
 267         assert_uninit_valid,
 268         assert_zero_valid,
 269         associated_consts,
 270         associated_type_bounds,
 271         associated_type_defaults,
 272         associated_types,
 273         assume,
 274         assume_init,
 275         async_await,
 276         async_closure,
 277         atomics,
 278         att_syntax,
 279         attr,
 280         attr_literals,
 281         attributes,
 282         augmented_assignments,
 283         automatically_derived,
 284         avx512_target_feature,
 285         await_macro,
 286         bang,
 287         begin_panic,
 288         bench,
 289         bin,
 290         bind_by_move_pattern_guards,
 291         bindings_after_at,
 292         bitand,
 293         bitand_assign,
 294         bitor,
 295         bitor_assign,
 296         bitreverse,
 297         bitxor,
 298         bitxor_assign,
 299         block,
 300         bool,
 301         borrowck_graphviz_format,
 302         borrowck_graphviz_postflow,
 303         borrowck_graphviz_preflow,
 304         box_free,
 305         box_patterns,
 306         box_syntax,
 307         braced_empty_structs,
 308         breakpoint,
 309         bridge,
 310         bswap,
 311         c_variadic,
 312         call,
 313         call_mut,
 314         call_once,
 315         caller_location,
 316         cdylib,
 317         ceilf32,
 318         ceilf64,
 319         cfg,
 320         cfg_accessible,
 321         cfg_attr,
 322         cfg_attr_multi,
 323         cfg_doctest,
 324         cfg_sanitize,
 325         cfg_target_feature,
 326         cfg_target_has_atomic,
 327         cfg_target_thread_local,
 328         cfg_target_vendor,
 329         cfg_version,
 330         char,
 331         client,
 332         clippy,
 333         clone,
 334         clone_closures,
 335         clone_from,
 336         closure_to_fn_coercion,
 337         cmp,
 338         cmpxchg16b_target_feature,
 339         coerce_unsized,
 340         cold,
 341         column,
 342         compile_error,
 343         compiler_builtins,
 344         concat,
 345         concat_idents,
 346         conservative_impl_trait,
 347         console,
 348         const_compare_raw_pointers,
 349         const_constructor,
 350         const_eval_limit,
 351         const_extern_fn,
 352         const_fn,
 353         const_fn_transmute,
 354         const_fn_union,
 355         const_generics,
 356         const_if_match,
 357         const_in_array_repeat_expressions,
 358         const_indexing,
 359         const_let,
 360         const_loop,
 361         const_mut_refs,
 362         const_panic,
 363         const_precise_live_drops,
 364         const_ptr,
 365         const_raw_ptr_deref,
 366         const_raw_ptr_to_usize_cast,
 367         const_slice_ptr,
 368         const_trait_bound_opt_out,
 369         const_trait_impl,
 370         const_transmute,
 371         contents,
 372         context,
 373         convert,
 374         copy,
 375         copy_closures,
 376         copy_nonoverlapping,
 377         copysignf32,
 378         copysignf64,
 379         core,
 380         core_intrinsics,
 381         cosf32,
 382         cosf64,
 383         count_code_region,
 384         coverage_counter_add,
 385         coverage_counter_subtract,
 386         coverage_unreachable,
 387         crate_id,
 388         crate_in_paths,
 389         crate_local,
 390         crate_name,
 391         crate_type,
 392         crate_visibility_modifier,
 393         crt_dash_static: "crt-static",
 394         ctlz,
 395         ctlz_nonzero,
 396         ctpop,
 397         cttz,
 398         cttz_nonzero,
 399         custom_attribute,
 400         custom_derive,
 401         custom_inner_attributes,
 402         custom_test_frameworks,
 403         d,
 404         dead_code,
 405         dealloc,
 406         debug,
 407         debug_assertions,
 408         debug_struct,
 409         debug_trait,
 410         debug_trait_builder,
 411         debug_tuple,
 412         decl_macro,
 413         declare_lint_pass,
 414         decode,
 415         default_lib_allocator,
 416         default_type_parameter_fallback,
 417         default_type_params,
 418         delay_span_bug_from_inside_query,
 419         deny,
 420         deprecated,
 421         deref,
 422         deref_mut,
 423         derive,
 424         diagnostic,
 425         direct,
 426         discriminant_kind,
 427         discriminant_type,
 428         discriminant_value,
 429         dispatch_from_dyn,
 430         div,
 431         div_assign,
 432         doc,
 433         doc_alias,
 434         doc_cfg,
 435         doc_keyword,
 436         doc_masked,
 437         doc_spotlight,
 438         doctest,
 439         document_private_items,
 440         dotdot_in_tuple_patterns,
 441         dotdoteq_in_patterns,
 442         double_braced_closure: "{{closure}}",
 443         double_braced_constant: "{{constant}}",
 444         double_braced_constructor: "{{constructor}}",
 445         double_braced_crate: "{{crate}}",
 446         double_braced_impl: "{{impl}}",
 447         double_braced_misc: "{{misc}}",
 448         double_braced_opaque: "{{opaque}}",
 449         drop,
 450         drop_in_place,
 451         drop_types_in_const,
 452         dropck_eyepatch,
 453         dropck_parametricity,
 454         dylib,
 455         dyn_trait,
 456         eh_catch_typeinfo,
 457         eh_personality,
 458         emit_enum,
 459         emit_enum_variant,
 460         emit_enum_variant_arg,
 461         emit_struct,
 462         emit_struct_field,
 463         enable,
 464         enclosing_scope,
 465         encode,
 466         env,
 467         eq,
 468         err,
 469         exact_div,
 470         except,
 471         exchange_malloc,
 472         exclusive_range_pattern,
 473         exhaustive_integer_patterns,
 474         exhaustive_patterns,
 475         existential_type,
 476         exp2f32,
 477         exp2f64,
 478         expected,
 479         expf32,
 480         expf64,
 481         export_name,
 482         expr,
 483         extern_absolute_paths,
 484         extern_crate_item_prelude,
 485         extern_crate_self,
 486         extern_in_paths,
 487         extern_prelude,
 488         extern_types,
 489         external_doc,
 490         f,
 491         f16c_target_feature,
 492         f32,
 493         f32_runtime,
 494         f64,
 495         f64_runtime,
 496         fabsf32,
 497         fabsf64,
 498         fadd_fast,
 499         fdiv_fast,
 500         feature,
 501         ffi_const,
 502         ffi_pure,
 503         ffi_returns_twice,
 504         field,
 505         field_init_shorthand,
 506         file,
 507         fill,
 508         finish,
 509         flags,
 510         float_to_int_unchecked,
 511         floorf32,
 512         floorf64,
 513         fmaf32,
 514         fmaf64,
 515         fmt,
 516         fmt_internals,
 517         fmul_fast,
 518         fn_must_use,
 519         fn_mut,
 520         fn_once,
 521         fn_once_output,
 522         forbid,
 523         forget,
 524         format,
 525         format_args,
 526         format_args_capture,
 527         format_args_nl,
 528         freeze,
 529         frem_fast,
 530         from,
 531         from_desugaring,
 532         from_error,
 533         from_generator,
 534         from_method,
 535         from_ok,
 536         from_size_align_unchecked,
 537         from_trait,
 538         from_usize,
 539         fsub_fast,
 540         fundamental,
 541         future,
 542         future_trait,
 543         ge,
 544         gen_future,
 545         gen_kill,
 546         generator,
 547         generator_state,
 548         generators,
 549         generic_associated_types,
 550         generic_param_attrs,
 551         get_context,
 552         global_allocator,
 553         global_asm,
 554         globs,
 555         gt,
 556         half_open_range_patterns,
 557         hash,
 558         hexagon_target_feature,
 559         hidden,
 560         homogeneous_aggregate,
 561         html_favicon_url,
 562         html_logo_url,
 563         html_no_source,
 564         html_playground_url,
 565         html_root_url,
 566         i,
 567         i128,
 568         i128_type,
 569         i16,
 570         i32,
 571         i64,
 572         i8,
 573         ident,
 574         if_let,
 575         if_while_or_patterns,
 576         ignore,
 577         impl_header_lifetime_elision,
 578         impl_lint_pass,
 579         impl_trait_in_bindings,
 580         import_shadowing,
 581         in_band_lifetimes,
 582         include,
 583         include_bytes,
 584         include_str,
 585         inclusive_range_syntax,
 586         index,
 587         index_mut,
 588         infer_outlives_requirements,
 589         infer_static_outlives_requirements,
 590         inlateout,
 591         inline,
 592         inout,
 593         intel,
 594         into_iter,
 595         into_result,
 596         intrinsics,
 597         irrefutable_let_patterns,
 598         isize,
 599         issue,
 600         issue_5723_bootstrap,
 601         issue_tracker_base_url,
 602         item,
 603         item_like_imports,
 604         iter,
 605         keyword,
 606         kind,
 607         label,
 608         label_break_value,
 609         lang,
 610         lang_items,
 611         lateout,
 612         lazy_normalization_consts,
 613         le,
 614         let_chains,
 615         lhs,
 616         lib,
 617         libc,
 618         lifetime,
 619         likely,
 620         line,
 621         link,
 622         link_args,
 623         link_cfg,
 624         link_llvm_intrinsics,
 625         link_name,
 626         link_ordinal,
 627         link_section,
 628         linkage,
 629         lint_reasons,
 630         literal,
 631         llvm_asm,
 632         local_inner_macros,
 633         log10f32,
 634         log10f64,
 635         log2f32,
 636         log2f64,
 637         log_syntax,
 638         logf32,
 639         logf64,
 640         loop_break_value,
 641         lt,
 642         macro_at_most_once_rep,
 643         macro_escape,
 644         macro_export,
 645         macro_lifetime_matcher,
 646         macro_literal_matcher,
 647         macro_reexport,
 648         macro_use,
 649         macro_vis_matcher,
 650         macros_in_extern,
 651         main,
 652         managed_boxes,
 653         manually_drop,
 654         map,
 655         marker,
 656         marker_trait_attr,
 657         masked,
 658         match_beginning_vert,
 659         match_default_bindings,
 660         maxnumf32,
 661         maxnumf64,
 662         may_dangle,
 663         maybe_uninit,
 664         maybe_uninit_uninit,
 665         maybe_uninit_zeroed,
 666         mem_uninitialized,
 667         mem_zeroed,
 668         member_constraints,
 669         memory,
 670         message,
 671         meta,
 672         min_align_of,
 673         min_align_of_val,
 674         min_const_fn,
 675         min_const_generics,
 676         min_const_unsafe_fn,
 677         min_specialization,
 678         minnumf32,
 679         minnumf64,
 680         mips_target_feature,
 681         mmx_target_feature,
 682         module,
 683         module_path,
 684         more_struct_aliases,
 685         movbe_target_feature,
 686         move_ref_pattern,
 687         move_val_init,
 688         mul,
 689         mul_assign,
 690         mul_with_overflow,
 691         must_use,
 692         mut_ptr,
 693         mut_slice_ptr,
 694         naked,
 695         naked_functions,
 696         name,
 697         ne,
 698         nearbyintf32,
 699         nearbyintf64,
 700         needs_allocator,
 701         needs_drop,
 702         needs_panic_runtime,
 703         neg,
 704         negate_unsigned,
 705         negative_impls,
 706         never,
 707         never_type,
 708         never_type_fallback,
 709         new,
 710         next,
 711         nll,
 712         no,
 713         no_builtins,
 714         no_core,
 715         no_crate_inject,
 716         no_debug,
 717         no_default_passes,
 718         no_implicit_prelude,
 719         no_inline,
 720         no_link,
 721         no_main,
 722         no_mangle,
 723         no_niche,
 724         no_sanitize,
 725         no_stack_check,
 726         no_start,
 727         no_std,
 728         nomem,
 729         non_ascii_idents,
 730         non_exhaustive,
 731         non_modrs_mods,
 732         none_error,
 733         nontemporal_store,
 734         nontrapping_dash_fptoint: "nontrapping-fptoint",
 735         noreturn,
 736         nostack,
 737         not,
 738         note,
 739         object_safe_for_dispatch,
 740         of,
 741         offset,
 742         omit_gdb_pretty_printer_section,
 743         on,
 744         on_unimplemented,
 745         oom,
 746         opaque,
 747         ops,
 748         opt_out_copy,
 749         optimize,
 750         optimize_attribute,
 751         optin_builtin_traits,
 752         option,
 753         option_env,
 754         option_type,
 755         options,
 756         or,
 757         or_patterns,
 758         other,
 759         out,
 760         overlapping_marker_traits,
 761         owned_box,
 762         packed,
 763         panic,
 764         panic_abort,
 765         panic_bounds_check,
 766         panic_handler,
 767         panic_impl,
 768         panic_implementation,
 769         panic_info,
 770         panic_location,
 771         panic_runtime,
 772         panic_unwind,
 773         param_attrs,
 774         parent_trait,
 775         partial_cmp,
 776         partial_ord,
 777         passes,
 778         pat,
 779         path,
 780         pattern_parentheses,
 781         phantom_data,
 782         pin,
 783         pinned,
 784         platform_intrinsics,
 785         plugin,
 786         plugin_registrar,
 787         plugins,
 788         pointer,
 789         poll,
 790         position,
 791         post_dash_lto: "post-lto",
 792         powerpc_target_feature,
 793         powf32,
 794         powf64,
 795         powif32,
 796         powif64,
 797         pre_dash_lto: "pre-lto",
 798         precise_pointer_size_matching,
 799         precision,
 800         pref_align_of,
 801         prefetch_read_data,
 802         prefetch_read_instruction,
 803         prefetch_write_data,
 804         prefetch_write_instruction,
 805         prelude,
 806         prelude_import,
 807         preserves_flags,
 808         primitive,
 809         proc_dash_macro: "proc-macro",
 810         proc_macro,
 811         proc_macro_attribute,
 812         proc_macro_def_site,
 813         proc_macro_derive,
 814         proc_macro_expr,
 815         proc_macro_gen,
 816         proc_macro_hygiene,
 817         proc_macro_internals,
 818         proc_macro_mod,
 819         proc_macro_non_items,
 820         proc_macro_path_invoc,
 821         profiler_builtins,
 822         profiler_runtime,
 823         ptr_guaranteed_eq,
 824         ptr_guaranteed_ne,
 825         ptr_offset_from,
 826         pub_restricted,
 827         pure,
 828         pushpop_unsafe,
 829         quad_precision_float,
 830         question_mark,
 831         quote,
 832         raw_dylib,
 833         raw_identifiers,
 834         raw_ref_op,
 835         re_rebalance_coherence,
 836         read_enum,
 837         read_enum_variant,
 838         read_enum_variant_arg,
 839         read_struct,
 840         read_struct_field,
 841         readonly,
 842         realloc,
 843         reason,
 844         receiver,
 845         recursion_limit,
 846         reexport_test_harness_main,
 847         reference,
 848         reflect,
 849         register_attr,
 850         register_tool,
 851         relaxed_adts,
 852         rem,
 853         rem_assign,
 854         repr,
 855         repr128,
 856         repr_align,
 857         repr_align_enum,
 858         repr_no_niche,
 859         repr_packed,
 860         repr_simd,
 861         repr_transparent,
 862         result,
 863         result_type,
 864         rhs,
 865         rintf32,
 866         rintf64,
 867         riscv_target_feature,
 868         rlib,
 869         rotate_left,
 870         rotate_right,
 871         roundf32,
 872         roundf64,
 873         rt,
 874         rtm_target_feature,
 875         rust,
 876         rust_2015_preview,
 877         rust_2018_preview,
 878         rust_begin_unwind,
 879         rust_eh_personality,
 880         rust_eh_register_frames,
 881         rust_eh_unregister_frames,
 882         rust_oom,
 883         rustc,
 884         rustc_allocator,
 885         rustc_allocator_nounwind,
 886         rustc_allow_const_fn_ptr,
 887         rustc_args_required_const,
 888         rustc_attrs,
 889         rustc_builtin_macro,
 890         rustc_clean,
 891         rustc_const_stable,
 892         rustc_const_unstable,
 893         rustc_conversion_suggestion,
 894         rustc_def_path,
 895         rustc_deprecated,
 896         rustc_diagnostic_item,
 897         rustc_diagnostic_macros,
 898         rustc_dirty,
 899         rustc_dummy,
 900         rustc_dump_env_program_clauses,
 901         rustc_dump_program_clauses,
 902         rustc_dump_user_substs,
 903         rustc_error,
 904         rustc_expected_cgu_reuse,
 905         rustc_if_this_changed,
 906         rustc_inherit_overflow_checks,
 907         rustc_layout,
 908         rustc_layout_scalar_valid_range_end,
 909         rustc_layout_scalar_valid_range_start,
 910         rustc_macro_transparency,
 911         rustc_mir,
 912         rustc_nonnull_optimization_guaranteed,
 913         rustc_object_lifetime_default,
 914         rustc_on_unimplemented,
 915         rustc_outlives,
 916         rustc_paren_sugar,
 917         rustc_partition_codegened,
 918         rustc_partition_reused,
 919         rustc_peek,
 920         rustc_peek_definite_init,
 921         rustc_peek_indirectly_mutable,
 922         rustc_peek_liveness,
 923         rustc_peek_maybe_init,
 924         rustc_peek_maybe_uninit,
 925         rustc_polymorphize_error,
 926         rustc_private,
 927         rustc_proc_macro_decls,
 928         rustc_promotable,
 929         rustc_regions,
 930         rustc_reservation_impl,
 931         rustc_serialize,
 932         rustc_specialization_trait,
 933         rustc_stable,
 934         rustc_std_internal_symbol,
 935         rustc_symbol_name,
 936         rustc_synthetic,
 937         rustc_test_marker,
 938         rustc_then_this_would_need,
 939         rustc_unsafe_specialization_marker,
 940         rustc_variance,
 941         rustfmt,
 942         rvalue_static_promotion,
 943         sanitize,
 944         sanitizer_runtime,
 945         saturating_add,
 946         saturating_sub,
 947         self_in_typedefs,
 948         self_struct_ctor,
 949         semitransparent,
 950         send_trait,
 951         shl,
 952         shl_assign,
 953         should_panic,
 954         shr,
 955         shr_assign,
 956         simd,
 957         simd_add,
 958         simd_and,
 959         simd_bitmask,
 960         simd_cast,
 961         simd_ceil,
 962         simd_div,
 963         simd_eq,
 964         simd_extract,
 965         simd_fabs,
 966         simd_fcos,
 967         simd_fexp,
 968         simd_fexp2,
 969         simd_ffi,
 970         simd_flog,
 971         simd_flog10,
 972         simd_flog2,
 973         simd_floor,
 974         simd_fma,
 975         simd_fmax,
 976         simd_fmin,
 977         simd_fpow,
 978         simd_fpowi,
 979         simd_fsin,
 980         simd_fsqrt,
 981         simd_gather,
 982         simd_ge,
 983         simd_gt,
 984         simd_insert,
 985         simd_le,
 986         simd_lt,
 987         simd_mul,
 988         simd_ne,
 989         simd_or,
 990         simd_reduce_add_ordered,
 991         simd_reduce_add_unordered,
 992         simd_reduce_all,
 993         simd_reduce_and,
 994         simd_reduce_any,
 995         simd_reduce_max,
 996         simd_reduce_max_nanless,
 997         simd_reduce_min,
 998         simd_reduce_min_nanless,
 999         simd_reduce_mul_ordered,
1000         simd_reduce_mul_unordered,
1001         simd_reduce_or,
1002         simd_reduce_xor,
1003         simd_rem,
1004         simd_saturating_add,
1005         simd_saturating_sub,
1006         simd_scatter,
1007         simd_select,
1008         simd_select_bitmask,
1009         simd_shl,
1010         simd_shr,
1011         simd_sub,
1012         simd_xor,
1013         since,
1014         sinf32,
1015         sinf64,
1016         size,
1017         size_of,
1018         size_of_val,
1019         sized,
1020         slice,
1021         slice_alloc,
1022         slice_patterns,
1023         slice_u8,
1024         slice_u8_alloc,
1025         slicing_syntax,
1026         soft,
1027         specialization,
1028         speed,
1029         spotlight,
1030         sqrtf32,
1031         sqrtf64,
1032         sse4a_target_feature,
1033         stable,
1034         staged_api,
1035         start,
1036         state,
1037         static_in_const,
1038         static_nobundle,
1039         static_recursion,
1040         staticlib,
1041         std,
1042         std_inject,
1043         stmt,
1044         stmt_expr_attributes,
1045         stop_after_dataflow,
1046         str,
1047         str_alloc,
1048         string_type,
1049         stringify,
1050         struct_field_attributes,
1051         struct_inherit,
1052         struct_variant,
1053         structural_match,
1054         structural_peq,
1055         structural_teq,
1056         sty,
1057         sub,
1058         sub_assign,
1059         sub_with_overflow,
1060         suggestion,
1061         sym,
1062         sync,
1063         sync_trait,
1064         target_arch,
1065         target_endian,
1066         target_env,
1067         target_family,
1068         target_feature,
1069         target_feature_11,
1070         target_has_atomic,
1071         target_has_atomic_load_store,
1072         target_os,
1073         target_pointer_width,
1074         target_target_vendor,
1075         target_thread_local,
1076         target_vendor,
1077         task,
1078         tbm_target_feature,
1079         termination,
1080         termination_trait,
1081         termination_trait_test,
1082         test,
1083         test_2018_feature,
1084         test_accepted_feature,
1085         test_case,
1086         test_removed_feature,
1087         test_runner,
1088         then_with,
1089         thread,
1090         thread_local,
1091         tool_attributes,
1092         tool_lints,
1093         trace_macros,
1094         track_caller,
1095         trait_alias,
1096         transmute,
1097         transparent,
1098         transparent_enums,
1099         transparent_unions,
1100         trivial_bounds,
1101         truncf32,
1102         truncf64,
1103         try_blocks,
1104         try_trait,
1105         tt,
1106         tuple,
1107         tuple_indexing,
1108         two_phase,
1109         ty,
1110         type_alias_enum_variants,
1111         type_alias_impl_trait,
1112         type_ascription,
1113         type_id,
1114         type_length_limit,
1115         type_macros,
1116         type_name,
1117         u128,
1118         u16,
1119         u32,
1120         u64,
1121         u8,
1122         unaligned_volatile_load,
1123         unaligned_volatile_store,
1124         unboxed_closures,
1125         unchecked_add,
1126         unchecked_div,
1127         unchecked_mul,
1128         unchecked_rem,
1129         unchecked_shl,
1130         unchecked_shr,
1131         unchecked_sub,
1132         underscore_const_names,
1133         underscore_imports,
1134         underscore_lifetimes,
1135         uniform_paths,
1136         unit,
1137         universal_impl_trait,
1138         unix,
1139         unlikely,
1140         unmarked_api,
1141         unpin,
1142         unreachable,
1143         unreachable_code,
1144         unrestricted_attribute_tokens,
1145         unsafe_block_in_unsafe_fn,
1146         unsafe_cell,
1147         unsafe_no_drop_flag,
1148         unsize,
1149         unsized_locals,
1150         unsized_tuple_coercion,
1151         unstable,
1152         untagged_unions,
1153         unused_qualifications,
1154         unwind,
1155         unwind_attributes,
1156         unwrap_or,
1157         use_extern_macros,
1158         use_nested_groups,
1159         used,
1160         usize,
1161         v1,
1162         va_arg,
1163         va_copy,
1164         va_end,
1165         va_list,
1166         va_start,
1167         val,
1168         var,
1169         variant_count,
1170         vec,
1171         vec_type,
1172         version,
1173         vis,
1174         visible_private_types,
1175         volatile,
1176         volatile_copy_memory,
1177         volatile_copy_nonoverlapping_memory,
1178         volatile_load,
1179         volatile_set_memory,
1180         volatile_store,
1181         warn,
1182         wasm_import_module,
1183         wasm_target_feature,
1184         while_let,
1185         width,
1186         windows,
1187         windows_subsystem,
1188         wrapping_add,
1189         wrapping_mul,
1190         wrapping_sub,
1191         write_bytes,
1192     }
1193 }
1194
1195 #[derive(Copy, Clone, Eq, HashStable_Generic)]
1196 pub struct Ident {
1197     pub name: Symbol,
1198     pub span: Span,
1199 }
1200
1201 impl Ident {
1202     #[inline]
1203     /// Constructs a new identifier from a symbol and a span.
1204     pub const fn new(name: Symbol, span: Span) -> Ident {
1205         Ident { name, span }
1206     }
1207
1208     /// Constructs a new identifier with a dummy span.
1209     #[inline]
1210     pub const fn with_dummy_span(name: Symbol) -> Ident {
1211         Ident::new(name, DUMMY_SP)
1212     }
1213
1214     #[inline]
1215     pub fn invalid() -> Ident {
1216         Ident::with_dummy_span(kw::Invalid)
1217     }
1218
1219     /// Maps a string to an identifier with a dummy span.
1220     pub fn from_str(string: &str) -> Ident {
1221         Ident::with_dummy_span(Symbol::intern(string))
1222     }
1223
1224     /// Maps a string and a span to an identifier.
1225     pub fn from_str_and_span(string: &str, span: Span) -> Ident {
1226         Ident::new(Symbol::intern(string), span)
1227     }
1228
1229     /// Replaces `lo` and `hi` with those from `span`, but keep hygiene context.
1230     pub fn with_span_pos(self, span: Span) -> Ident {
1231         Ident::new(self.name, span.with_ctxt(self.span.ctxt()))
1232     }
1233
1234     pub fn without_first_quote(self) -> Ident {
1235         Ident::new(Symbol::intern(self.as_str().trim_start_matches('\'')), self.span)
1236     }
1237
1238     /// "Normalize" ident for use in comparisons using "item hygiene".
1239     /// Identifiers with same string value become same if they came from the same macro 2.0 macro
1240     /// (e.g., `macro` item, but not `macro_rules` item) and stay different if they came from
1241     /// different macro 2.0 macros.
1242     /// Technically, this operation strips all non-opaque marks from ident's syntactic context.
1243     pub fn normalize_to_macros_2_0(self) -> Ident {
1244         Ident::new(self.name, self.span.normalize_to_macros_2_0())
1245     }
1246
1247     /// "Normalize" ident for use in comparisons using "local variable hygiene".
1248     /// Identifiers with same string value become same if they came from the same non-transparent
1249     /// macro (e.g., `macro` or `macro_rules!` items) and stay different if they came from different
1250     /// non-transparent macros.
1251     /// Technically, this operation strips all transparent marks from ident's syntactic context.
1252     pub fn normalize_to_macro_rules(self) -> Ident {
1253         Ident::new(self.name, self.span.normalize_to_macro_rules())
1254     }
1255
1256     /// Convert the name to a `SymbolStr`. This is a slowish operation because
1257     /// it requires locking the symbol interner.
1258     pub fn as_str(self) -> SymbolStr {
1259         self.name.as_str()
1260     }
1261 }
1262
1263 impl PartialEq for Ident {
1264     fn eq(&self, rhs: &Self) -> bool {
1265         self.name == rhs.name && self.span.ctxt() == rhs.span.ctxt()
1266     }
1267 }
1268
1269 impl Hash for Ident {
1270     fn hash<H: Hasher>(&self, state: &mut H) {
1271         self.name.hash(state);
1272         self.span.ctxt().hash(state);
1273     }
1274 }
1275
1276 impl fmt::Debug for Ident {
1277     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1278         fmt::Display::fmt(self, f)?;
1279         fmt::Debug::fmt(&self.span.ctxt(), f)
1280     }
1281 }
1282
1283 /// This implementation is supposed to be used in error messages, so it's expected to be identical
1284 /// to printing the original identifier token written in source code (`token_to_string`),
1285 /// except that AST identifiers don't keep the rawness flag, so we have to guess it.
1286 impl fmt::Display for Ident {
1287     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1288         fmt::Display::fmt(&IdentPrinter::new(self.name, self.is_raw_guess(), None), f)
1289     }
1290 }
1291
1292 impl UseSpecializedEncodable for Ident {
1293     fn default_encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
1294         s.emit_struct("Ident", 2, |s| {
1295             s.emit_struct_field("name", 0, |s| self.name.encode(s))?;
1296             s.emit_struct_field("span", 1, |s| self.span.encode(s))
1297         })
1298     }
1299 }
1300
1301 impl UseSpecializedDecodable for Ident {
1302     fn default_decode<D: Decoder>(d: &mut D) -> Result<Self, D::Error> {
1303         d.read_struct("Ident", 2, |d| {
1304             Ok(Ident {
1305                 name: d.read_struct_field("name", 0, Decodable::decode)?,
1306                 span: d.read_struct_field("span", 1, Decodable::decode)?,
1307             })
1308         })
1309     }
1310 }
1311
1312 /// This is the most general way to print identifiers.
1313 /// AST pretty-printer is used as a fallback for turning AST structures into token streams for
1314 /// proc macros. Additionally, proc macros may stringify their input and expect it survive the
1315 /// stringification (especially true for proc macro derives written between Rust 1.15 and 1.30).
1316 /// So we need to somehow pretty-print `$crate` in a way preserving at least some of its
1317 /// hygiene data, most importantly name of the crate it refers to.
1318 /// As a result we print `$crate` as `crate` if it refers to the local crate
1319 /// and as `::other_crate_name` if it refers to some other crate.
1320 /// Note, that this is only done if the ident token is printed from inside of AST pretty-pringing,
1321 /// but not otherwise. Pretty-printing is the only way for proc macros to discover token contents,
1322 /// so we should not perform this lossy conversion if the top level call to the pretty-printer was
1323 /// done for a token stream or a single token.
1324 pub struct IdentPrinter {
1325     symbol: Symbol,
1326     is_raw: bool,
1327     /// Span used for retrieving the crate name to which `$crate` refers to,
1328     /// if this field is `None` then the `$crate` conversion doesn't happen.
1329     convert_dollar_crate: Option<Span>,
1330 }
1331
1332 impl IdentPrinter {
1333     /// The most general `IdentPrinter` constructor. Do not use this.
1334     pub fn new(symbol: Symbol, is_raw: bool, convert_dollar_crate: Option<Span>) -> IdentPrinter {
1335         IdentPrinter { symbol, is_raw, convert_dollar_crate }
1336     }
1337
1338     /// This implementation is supposed to be used when printing identifiers
1339     /// as a part of pretty-printing for larger AST pieces.
1340     /// Do not use this either.
1341     pub fn for_ast_ident(ident: Ident, is_raw: bool) -> IdentPrinter {
1342         IdentPrinter::new(ident.name, is_raw, Some(ident.span))
1343     }
1344 }
1345
1346 impl fmt::Display for IdentPrinter {
1347     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1348         if self.is_raw {
1349             f.write_str("r#")?;
1350         } else {
1351             if self.symbol == kw::DollarCrate {
1352                 if let Some(span) = self.convert_dollar_crate {
1353                     let converted = span.ctxt().dollar_crate_name();
1354                     if !converted.is_path_segment_keyword() {
1355                         f.write_str("::")?;
1356                     }
1357                     return fmt::Display::fmt(&converted, f);
1358                 }
1359             }
1360         }
1361         fmt::Display::fmt(&self.symbol, f)
1362     }
1363 }
1364
1365 /// An newtype around `Ident` that calls [Ident::normalize_to_macro_rules] on
1366 /// construction.
1367 // FIXME(matthewj, petrochenkov) Use this more often, add a similar
1368 // `ModernIdent` struct and use that as well.
1369 #[derive(Copy, Clone, Eq, PartialEq, Hash)]
1370 pub struct MacroRulesNormalizedIdent(Ident);
1371
1372 impl MacroRulesNormalizedIdent {
1373     pub fn new(ident: Ident) -> Self {
1374         Self(ident.normalize_to_macro_rules())
1375     }
1376 }
1377
1378 impl fmt::Debug for MacroRulesNormalizedIdent {
1379     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1380         fmt::Debug::fmt(&self.0, f)
1381     }
1382 }
1383
1384 impl fmt::Display for MacroRulesNormalizedIdent {
1385     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1386         fmt::Display::fmt(&self.0, f)
1387     }
1388 }
1389
1390 /// An interned string.
1391 ///
1392 /// Internally, a `Symbol` is implemented as an index, and all operations
1393 /// (including hashing, equality, and ordering) operate on that index. The use
1394 /// of `rustc_index::newtype_index!` means that `Option<Symbol>` only takes up 4 bytes,
1395 /// because `rustc_index::newtype_index!` reserves the last 256 values for tagging purposes.
1396 ///
1397 /// Note that `Symbol` cannot directly be a `rustc_index::newtype_index!` because it
1398 /// implements `fmt::Debug`, `Encodable`, and `Decodable` in special ways.
1399 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
1400 pub struct Symbol(SymbolIndex);
1401
1402 rustc_index::newtype_index! {
1403     pub struct SymbolIndex { .. }
1404 }
1405
1406 impl Symbol {
1407     const fn new(n: u32) -> Self {
1408         Symbol(SymbolIndex::from_u32(n))
1409     }
1410
1411     /// Maps a string to its interned representation.
1412     pub fn intern(string: &str) -> Self {
1413         with_interner(|interner| interner.intern(string))
1414     }
1415
1416     /// Access the symbol's chars. This is a slowish operation because it
1417     /// requires locking the symbol interner.
1418     pub fn with<F: FnOnce(&str) -> R, R>(self, f: F) -> R {
1419         with_interner(|interner| f(interner.get(self)))
1420     }
1421
1422     /// Convert to a `SymbolStr`. This is a slowish operation because it
1423     /// requires locking the symbol interner.
1424     pub fn as_str(self) -> SymbolStr {
1425         with_interner(|interner| unsafe {
1426             SymbolStr { string: std::mem::transmute::<&str, &str>(interner.get(self)) }
1427         })
1428     }
1429
1430     pub fn as_u32(self) -> u32 {
1431         self.0.as_u32()
1432     }
1433
1434     /// This method is supposed to be used in error messages, so it's expected to be
1435     /// identical to printing the original identifier token written in source code
1436     /// (`token_to_string`, `Ident::to_string`), except that symbols don't keep the rawness flag
1437     /// or edition, so we have to guess the rawness using the global edition.
1438     pub fn to_ident_string(self) -> String {
1439         Ident::with_dummy_span(self).to_string()
1440     }
1441 }
1442
1443 impl fmt::Debug for Symbol {
1444     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1445         self.with(|str| fmt::Debug::fmt(&str, f))
1446     }
1447 }
1448
1449 impl fmt::Display for Symbol {
1450     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1451         self.with(|str| fmt::Display::fmt(&str, f))
1452     }
1453 }
1454
1455 impl Encodable for Symbol {
1456     fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
1457         self.with(|string| s.emit_str(string))
1458     }
1459 }
1460
1461 impl Decodable for Symbol {
1462     #[inline]
1463     fn decode<D: Decoder>(d: &mut D) -> Result<Symbol, D::Error> {
1464         Ok(Symbol::intern(&d.read_str()?))
1465     }
1466 }
1467
1468 impl<CTX> HashStable<CTX> for Symbol {
1469     #[inline]
1470     fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
1471         self.as_str().hash_stable(hcx, hasher);
1472     }
1473 }
1474
1475 impl<CTX> ToStableHashKey<CTX> for Symbol {
1476     type KeyType = SymbolStr;
1477
1478     #[inline]
1479     fn to_stable_hash_key(&self, _: &CTX) -> SymbolStr {
1480         self.as_str()
1481     }
1482 }
1483
1484 // The `&'static str`s in this type actually point into the arena.
1485 //
1486 // The `FxHashMap`+`Vec` pair could be replaced by `FxIndexSet`, but #75278
1487 // found that to regress performance up to 2% in some cases. This might be
1488 // revisited after further improvements to `indexmap`.
1489 #[derive(Default)]
1490 pub struct Interner {
1491     arena: DroplessArena,
1492     names: FxHashMap<&'static str, Symbol>,
1493     strings: Vec<&'static str>,
1494 }
1495
1496 impl Interner {
1497     fn prefill(init: &[&'static str]) -> Self {
1498         Interner {
1499             strings: init.into(),
1500             names: init.iter().copied().zip((0..).map(Symbol::new)).collect(),
1501             ..Default::default()
1502         }
1503     }
1504
1505     #[inline]
1506     pub fn intern(&mut self, string: &str) -> Symbol {
1507         if let Some(&name) = self.names.get(string) {
1508             return name;
1509         }
1510
1511         let name = Symbol::new(self.strings.len() as u32);
1512
1513         // `from_utf8_unchecked` is safe since we just allocated a `&str` which is known to be
1514         // UTF-8.
1515         let string: &str =
1516             unsafe { str::from_utf8_unchecked(self.arena.alloc_slice(string.as_bytes())) };
1517         // It is safe to extend the arena allocation to `'static` because we only access
1518         // these while the arena is still alive.
1519         let string: &'static str = unsafe { &*(string as *const str) };
1520         self.strings.push(string);
1521         self.names.insert(string, name);
1522         name
1523     }
1524
1525     // Get the symbol as a string. `Symbol::as_str()` should be used in
1526     // preference to this function.
1527     pub fn get(&self, symbol: Symbol) -> &str {
1528         self.strings[symbol.0.as_usize()]
1529     }
1530 }
1531
1532 // This module has a very short name because it's used a lot.
1533 /// This module contains all the defined keyword `Symbol`s.
1534 ///
1535 /// Given that `kw` is imported, use them like `kw::keyword_name`.
1536 /// For example `kw::Loop` or `kw::Break`.
1537 pub mod kw {
1538     use super::Symbol;
1539     keywords!();
1540 }
1541
1542 // This module has a very short name because it's used a lot.
1543 /// This module contains all the defined non-keyword `Symbol`s.
1544 ///
1545 /// Given that `sym` is imported, use them like `sym::symbol_name`.
1546 /// For example `sym::rustfmt` or `sym::u8`.
1547 #[allow(rustc::default_hash_types)]
1548 pub mod sym {
1549     use super::Symbol;
1550     use std::convert::TryInto;
1551
1552     symbols!();
1553
1554     // Used from a macro in `librustc_feature/accepted.rs`
1555     pub use super::kw::MacroRules as macro_rules;
1556
1557     // Get the symbol for an integer. The first few non-negative integers each
1558     // have a static symbol and therefore are fast.
1559     pub fn integer<N: TryInto<usize> + Copy + ToString>(n: N) -> Symbol {
1560         if let Result::Ok(idx) = n.try_into() {
1561             if let Option::Some(&sym_) = digits_array.get(idx) {
1562                 return sym_;
1563             }
1564         }
1565         Symbol::intern(&n.to_string())
1566     }
1567 }
1568
1569 impl Symbol {
1570     fn is_used_keyword_2018(self) -> bool {
1571         self >= kw::Async && self <= kw::Dyn
1572     }
1573
1574     fn is_unused_keyword_2018(self) -> bool {
1575         self == kw::Try
1576     }
1577
1578     /// Used for sanity checking rustdoc keyword sections.
1579     pub fn is_doc_keyword(self) -> bool {
1580         self <= kw::Union
1581     }
1582
1583     /// A keyword or reserved identifier that can be used as a path segment.
1584     pub fn is_path_segment_keyword(self) -> bool {
1585         self == kw::Super
1586             || self == kw::SelfLower
1587             || self == kw::SelfUpper
1588             || self == kw::Crate
1589             || self == kw::PathRoot
1590             || self == kw::DollarCrate
1591     }
1592
1593     /// Returns `true` if the symbol is `true` or `false`.
1594     pub fn is_bool_lit(self) -> bool {
1595         self == kw::True || self == kw::False
1596     }
1597
1598     /// This symbol can be a raw identifier.
1599     pub fn can_be_raw(self) -> bool {
1600         self != kw::Invalid && self != kw::Underscore && !self.is_path_segment_keyword()
1601     }
1602 }
1603
1604 impl Ident {
1605     // Returns `true` for reserved identifiers used internally for elided lifetimes,
1606     // unnamed method parameters, crate root module, error recovery etc.
1607     pub fn is_special(self) -> bool {
1608         self.name <= kw::Underscore
1609     }
1610
1611     /// Returns `true` if the token is a keyword used in the language.
1612     pub fn is_used_keyword(self) -> bool {
1613         // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
1614         self.name >= kw::As && self.name <= kw::While
1615             || self.name.is_used_keyword_2018() && self.span.rust_2018()
1616     }
1617
1618     /// Returns `true` if the token is a keyword reserved for possible future use.
1619     pub fn is_unused_keyword(self) -> bool {
1620         // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
1621         self.name >= kw::Abstract && self.name <= kw::Yield
1622             || self.name.is_unused_keyword_2018() && self.span.rust_2018()
1623     }
1624
1625     /// Returns `true` if the token is either a special identifier or a keyword.
1626     pub fn is_reserved(self) -> bool {
1627         self.is_special() || self.is_used_keyword() || self.is_unused_keyword()
1628     }
1629
1630     /// A keyword or reserved identifier that can be used as a path segment.
1631     pub fn is_path_segment_keyword(self) -> bool {
1632         self.name.is_path_segment_keyword()
1633     }
1634
1635     /// We see this identifier in a normal identifier position, like variable name or a type.
1636     /// How was it written originally? Did it use the raw form? Let's try to guess.
1637     pub fn is_raw_guess(self) -> bool {
1638         self.name.can_be_raw() && self.is_reserved()
1639     }
1640 }
1641
1642 #[inline]
1643 fn with_interner<T, F: FnOnce(&mut Interner) -> T>(f: F) -> T {
1644     SESSION_GLOBALS.with(|session_globals| f(&mut *session_globals.symbol_interner.lock()))
1645 }
1646
1647 /// An alternative to `Symbol`, useful when the chars within the symbol need to
1648 /// be accessed. It deliberately has limited functionality and should only be
1649 /// used for temporary values.
1650 ///
1651 /// Because the interner outlives any thread which uses this type, we can
1652 /// safely treat `string` which points to interner data, as an immortal string,
1653 /// as long as this type never crosses between threads.
1654 //
1655 // FIXME: ensure that the interner outlives any thread which uses `SymbolStr`,
1656 // by creating a new thread right after constructing the interner.
1657 #[derive(Clone, Eq, PartialOrd, Ord)]
1658 pub struct SymbolStr {
1659     string: &'static str,
1660 }
1661
1662 // This impl allows a `SymbolStr` to be directly equated with a `String` or
1663 // `&str`.
1664 impl<T: std::ops::Deref<Target = str>> std::cmp::PartialEq<T> for SymbolStr {
1665     fn eq(&self, other: &T) -> bool {
1666         self.string == other.deref()
1667     }
1668 }
1669
1670 impl !Send for SymbolStr {}
1671 impl !Sync for SymbolStr {}
1672
1673 /// This impl means that if `ss` is a `SymbolStr`:
1674 /// - `*ss` is a `str`;
1675 /// - `&*ss` is a `&str` (and `match &*ss { ... }` is a common pattern).
1676 /// - `&ss as &str` is a `&str`, which means that `&ss` can be passed to a
1677 ///   function expecting a `&str`.
1678 impl std::ops::Deref for SymbolStr {
1679     type Target = str;
1680     #[inline]
1681     fn deref(&self) -> &str {
1682         self.string
1683     }
1684 }
1685
1686 impl fmt::Debug for SymbolStr {
1687     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1688         fmt::Debug::fmt(self.string, f)
1689     }
1690 }
1691
1692 impl fmt::Display for SymbolStr {
1693     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1694         fmt::Display::fmt(self.string, f)
1695     }
1696 }
1697
1698 impl<CTX> HashStable<CTX> for SymbolStr {
1699     #[inline]
1700     fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
1701         self.string.hash_stable(hcx, hasher)
1702     }
1703 }
1704
1705 impl<CTX> ToStableHashKey<CTX> for SymbolStr {
1706     type KeyType = SymbolStr;
1707
1708     #[inline]
1709     fn to_stable_hash_key(&self, _: &CTX) -> SymbolStr {
1710         self.clone()
1711     }
1712 }