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::HashStable_Generic;
   9 use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
  10
  11 use std::cmp::{Ord, PartialEq, PartialOrd};
  12 use std::fmt;
  13 use std::hash::{Hash, Hasher};
  14 use std::str;
  15
  16 use crate::{Span, DUMMY_SP, SESSION_GLOBALS};
  17
  18 #[cfg(test)]
  19 mod tests;
  20
  21 // The proc macro code for this is in `src/librustc_macros/src/symbols.rs`.
  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         MacroRules:         "macro_rules",
 101         Raw:                "raw",
 102         Union:              "union",
 103     }
 104
 105     // Pre-interned symbols that can be referred to with `rustc_span::sym::*`.
 106     //
 107     // The symbol is the stringified identifier unless otherwise specified, in
 108     // which case the name should mention the non-identifier punctuation.
 109     // E.g. `sym::proc_dash_macro` represents "proc-macro", and it shouldn't be
 110     // called `sym::proc_macro` because then it's easy to mistakenly think it
 111     // represents "proc_macro".
 112     //
 113     // As well as the symbols listed, there are symbols for the the strings
 114     // "0", "1", ..., "9", which are accessible via `sym::integer`.
 115     //
 116     // The proc macro will abort if symbols are not in alphabetical order (as
 117     // defined by `impl Ord for str`) or if any symbols are duplicated. Vim
 118     // users can sort the list by selecting it and executing the command
 119     // `:'<,'>!LC_ALL=C sort`.
 120     //
 121     // There is currently no checking that all symbols are used; that would be
 122     // nice to have.
 123     Symbols {
 124         Alignment,
 125         Arc,
 126         Argument,
 127         ArgumentV1,
 128         Arguments,
 129         C,
 130         Center,
 131         Clone,
 132         Copy,
 133         Count,
 134         Debug,
 135         Decodable,
 136         Decoder,
 137         Default,
 138         Encodable,
 139         Encoder,
 140         Eq,
 141         Equal,
 142         Err,
 143         Error,
 144         FormatSpec,
 145         Formatter,
 146         From,
 147         Future,
 148         FxHashMap,
 149         FxHashSet,
 150         GlobalAlloc,
 151         Hash,
 152         HashMap,
 153         HashSet,
 154         Hasher,
 155         Implied,
 156         Input,
 157         IntoIterator,
 158         Is,
 159         ItemContext,
 160         Iterator,
 161         Layout,
 162         Left,
 163         LintPass,
 164         None,
 165         Ok,
 166         Option,
 167         Ord,
 168         Ordering,
 169         Output,
 170         Param,
 171         PartialEq,
 172         PartialOrd,
 173         Pending,
 174         Pin,
 175         Poll,
 176         ProcMacro,
 177         ProcMacroHack,
 178         ProceduralMasqueradeDummyType,
 179         Range,
 180         RangeFrom,
 181         RangeFull,
 182         RangeInclusive,
 183         RangeTo,
 184         RangeToInclusive,
 185         Rc,
 186         Ready,
 187         Result,
 188         Return,
 189         Right,
 190         RustcDecodable,
 191         RustcEncodable,
 192         Send,
 193         Some,
 194         StructuralEq,
 195         StructuralPartialEq,
 196         Sync,
 197         Target,
 198         Try,
 199         Ty,
 200         TyCtxt,
 201         TyKind,
 202         Unknown,
 203         Vec,
 204         Yield,
 205         _DECLS,
 206         _Self,
 207         __D,
 208         __H,
 209         __S,
 210         __next,
 211         __try_var,
 212         _d,
 213         _e,
 214         _task_context,
 215         aarch64_target_feature,
 216         abi,
 217         abi_amdgpu_kernel,
 218         abi_avr_interrupt,
 219         abi_efiapi,
 220         abi_msp430_interrupt,
 221         abi_ptx,
 222         abi_sysv64,
 223         abi_thiscall,
 224         abi_unadjusted,
 225         abi_vectorcall,
 226         abi_x86_interrupt,
 227         abort,
 228         aborts,
 229         add,
 230         add_assign,
 231         add_with_overflow,
 232         address,
 233         advanced_slice_patterns,
 234         adx_target_feature,
 235         alias,
 236         align,
 237         align_offset,
 238         alignstack,
 239         all,
 240         alloc,
 241         alloc_error_handler,
 242         alloc_layout,
 243         alloc_zeroed,
 244         allocator,
 245         allocator_internals,
 246         allow,
 247         allow_fail,
 248         allow_internal_unsafe,
 249         allow_internal_unstable,
 250         allow_internal_unstable_backcompat_hack,
 251         allowed,
 252         always,
 253         and,
 254         and_then,
 255         any,
 256         arbitrary_enum_discriminant,
 257         arbitrary_self_types,
 258         arith_offset,
 259         arm_target_feature,
 260         array,
 261         arrays,
 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         crate_id,
 384         crate_in_paths,
 385         crate_local,
 386         crate_name,
 387         crate_type,
 388         crate_visibility_modifier,
 389         crt_dash_static: "crt-static",
 390         ctlz,
 391         ctlz_nonzero,
 392         ctpop,
 393         cttz,
 394         cttz_nonzero,
 395         custom_attribute,
 396         custom_derive,
 397         custom_inner_attributes,
 398         custom_test_frameworks,
 399         d,
 400         dead_code,
 401         dealloc,
 402         debug,
 403         debug_assertions,
 404         debug_struct,
 405         debug_trait,
 406         debug_trait_builder,
 407         debug_tuple,
 408         decl_macro,
 409         declare_lint_pass,
 410         decode,
 411         default_lib_allocator,
 412         default_type_parameter_fallback,
 413         default_type_params,
 414         delay_span_bug_from_inside_query,
 415         deny,
 416         deprecated,
 417         deref,
 418         deref_mut,
 419         derive,
 420         diagnostic,
 421         direct,
 422         discriminant_kind,
 423         discriminant_type,
 424         discriminant_value,
 425         dispatch_from_dyn,
 426         div,
 427         div_assign,
 428         doc,
 429         doc_alias,
 430         doc_cfg,
 431         doc_keyword,
 432         doc_masked,
 433         doc_spotlight,
 434         doctest,
 435         document_private_items,
 436         dotdot_in_tuple_patterns,
 437         dotdoteq_in_patterns,
 438         double_braced_closure: "{{closure}}",
 439         double_braced_constant: "{{constant}}",
 440         double_braced_constructor: "{{constructor}}",
 441         double_braced_crate: "{{crate}}",
 442         double_braced_impl: "{{impl}}",
 443         double_braced_misc: "{{misc}}",
 444         double_braced_opaque: "{{opaque}}",
 445         drop,
 446         drop_in_place,
 447         drop_types_in_const,
 448         dropck_eyepatch,
 449         dropck_parametricity,
 450         dylib,
 451         dyn_trait,
 452         eh_catch_typeinfo,
 453         eh_personality,
 454         emit_enum,
 455         emit_enum_variant,
 456         emit_enum_variant_arg,
 457         emit_struct,
 458         emit_struct_field,
 459         enable,
 460         enclosing_scope,
 461         encode,
 462         env,
 463         eq,
 464         err,
 465         exact_div,
 466         except,
 467         exchange_malloc,
 468         exclusive_range_pattern,
 469         exhaustive_integer_patterns,
 470         exhaustive_patterns,
 471         existential_type,
 472         exp2f32,
 473         exp2f64,
 474         expected,
 475         expf32,
 476         expf64,
 477         export_name,
 478         expr,
 479         extern_absolute_paths,
 480         extern_crate_item_prelude,
 481         extern_crate_self,
 482         extern_in_paths,
 483         extern_prelude,
 484         extern_types,
 485         external_doc,
 486         f,
 487         f16c_target_feature,
 488         f32,
 489         f32_runtime,
 490         f64,
 491         f64_runtime,
 492         fabsf32,
 493         fabsf64,
 494         fadd_fast,
 495         fdiv_fast,
 496         feature,
 497         ffi_const,
 498         ffi_pure,
 499         ffi_returns_twice,
 500         field,
 501         field_init_shorthand,
 502         file,
 503         fill,
 504         finish,
 505         flags,
 506         float_to_int_unchecked,
 507         floorf32,
 508         floorf64,
 509         fmaf32,
 510         fmaf64,
 511         fmt,
 512         fmt_internals,
 513         fmul_fast,
 514         fn_must_use,
 515         fn_mut,
 516         fn_once,
 517         fn_once_output,
 518         forbid,
 519         forget,
 520         format,
 521         format_args,
 522         format_args_capture,
 523         format_args_nl,
 524         freeze,
 525         frem_fast,
 526         from,
 527         from_desugaring,
 528         from_error,
 529         from_generator,
 530         from_method,
 531         from_ok,
 532         from_size_align_unchecked,
 533         from_trait,
 534         from_usize,
 535         fsub_fast,
 536         fundamental,
 537         future,
 538         future_trait,
 539         ge,
 540         gen_future,
 541         gen_kill,
 542         generator,
 543         generator_state,
 544         generators,
 545         generic_associated_types,
 546         generic_param_attrs,
 547         get_context,
 548         global_allocator,
 549         global_asm,
 550         globs,
 551         gt,
 552         half_open_range_patterns,
 553         hash,
 554         hexagon_target_feature,
 555         hidden,
 556         homogeneous_aggregate,
 557         html_favicon_url,
 558         html_logo_url,
 559         html_no_source,
 560         html_playground_url,
 561         html_root_url,
 562         i,
 563         i128,
 564         i128_type,
 565         i16,
 566         i32,
 567         i64,
 568         i8,
 569         ident,
 570         if_let,
 571         if_let_guard,
 572         if_while_or_patterns,
 573         ignore,
 574         impl_header_lifetime_elision,
 575         impl_lint_pass,
 576         impl_macros,
 577         impl_trait_in_bindings,
 578         import_shadowing,
 579         in_band_lifetimes,
 580         include,
 581         include_bytes,
 582         include_str,
 583         inclusive_range_syntax,
 584         index,
 585         index_mut,
 586         infer_outlives_requirements,
 587         infer_static_outlives_requirements,
 588         inlateout,
 589         inline,
 590         inout,
 591         intel,
 592         into_iter,
 593         into_result,
 594         intrinsics,
 595         irrefutable_let_patterns,
 596         isize,
 597         issue,
 598         issue_5723_bootstrap,
 599         issue_tracker_base_url,
 600         item,
 601         item_like_imports,
 602         iter,
 603         keyword,
 604         kind,
 605         label,
 606         label_break_value,
 607         lang,
 608         lang_items,
 609         lateout,
 610         lazy_normalization_consts,
 611         le,
 612         let_chains,
 613         lhs,
 614         lib,
 615         libc,
 616         lifetime,
 617         likely,
 618         line,
 619         link,
 620         link_args,
 621         link_cfg,
 622         link_llvm_intrinsics,
 623         link_name,
 624         link_ordinal,
 625         link_section,
 626         linkage,
 627         lint_reasons,
 628         literal,
 629         llvm_asm,
 630         local_inner_macros,
 631         log10f32,
 632         log10f64,
 633         log2f32,
 634         log2f64,
 635         log_syntax,
 636         logf32,
 637         logf64,
 638         loop_break_value,
 639         lt,
 640         macro_at_most_once_rep,
 641         macro_escape,
 642         macro_export,
 643         macro_lifetime_matcher,
 644         macro_literal_matcher,
 645         macro_reexport,
 646         macro_use,
 647         macro_vis_matcher,
 648         macros_in_extern,
 649         main,
 650         managed_boxes,
 651         manually_drop,
 652         map,
 653         marker,
 654         marker_trait_attr,
 655         masked,
 656         match_beginning_vert,
 657         match_default_bindings,
 658         maxnumf32,
 659         maxnumf64,
 660         may_dangle,
 661         maybe_uninit,
 662         maybe_uninit_uninit,
 663         maybe_uninit_zeroed,
 664         mem_uninitialized,
 665         mem_zeroed,
 666         member_constraints,
 667         memory,
 668         message,
 669         meta,
 670         min_align_of,
 671         min_align_of_val,
 672         min_const_fn,
 673         min_const_generics,
 674         min_const_unsafe_fn,
 675         min_specialization,
 676         minnumf32,
 677         minnumf64,
 678         mips_target_feature,
 679         mmx_target_feature,
 680         module,
 681         module_path,
 682         more_struct_aliases,
 683         movbe_target_feature,
 684         move_ref_pattern,
 685         move_val_init,
 686         mul,
 687         mul_assign,
 688         mul_with_overflow,
 689         must_use,
 690         mut_ptr,
 691         mut_slice_ptr,
 692         naked,
 693         naked_functions,
 694         name,
 695         ne,
 696         nearbyintf32,
 697         nearbyintf64,
 698         needs_allocator,
 699         needs_drop,
 700         needs_panic_runtime,
 701         neg,
 702         negate_unsigned,
 703         negative_impls,
 704         never,
 705         never_type,
 706         never_type_fallback,
 707         new,
 708         new_unchecked,
 709         next,
 710         nll,
 711         no,
 712         no_builtins,
 713         no_core,
 714         no_crate_inject,
 715         no_debug,
 716         no_default_passes,
 717         no_implicit_prelude,
 718         no_inline,
 719         no_link,
 720         no_main,
 721         no_mangle,
 722         no_niche,
 723         no_sanitize,
 724         no_stack_check,
 725         no_start,
 726         no_std,
 727         nomem,
 728         non_ascii_idents,
 729         non_exhaustive,
 730         non_modrs_mods,
 731         none_error,
 732         nontemporal_store,
 733         nontrapping_dash_fptoint: "nontrapping-fptoint",
 734         noreturn,
 735         nostack,
 736         not,
 737         note,
 738         object_safe_for_dispatch,
 739         of,
 740         offset,
 741         omit_gdb_pretty_printer_section,
 742         on,
 743         on_unimplemented,
 744         oom,
 745         opaque,
 746         ops,
 747         opt_out_copy,
 748         optimize,
 749         optimize_attribute,
 750         optin_builtin_traits,
 751         option,
 752         option_env,
 753         option_type,
 754         options,
 755         or,
 756         or_patterns,
 757         other,
 758         out,
 759         overlapping_marker_traits,
 760         owned_box,
 761         packed,
 762         panic,
 763         panic_abort,
 764         panic_bounds_check,
 765         panic_handler,
 766         panic_impl,
 767         panic_implementation,
 768         panic_info,
 769         panic_location,
 770         panic_runtime,
 771         panic_unwind,
 772         param_attrs,
 773         parent_trait,
 774         partial_cmp,
 775         partial_ord,
 776         passes,
 777         pat,
 778         path,
 779         pattern_parentheses,
 780         phantom_data,
 781         pin,
 782         pinned,
 783         platform_intrinsics,
 784         plugin,
 785         plugin_registrar,
 786         plugins,
 787         pointer,
 788         poll,
 789         position,
 790         post_dash_lto: "post-lto",
 791         powerpc_target_feature,
 792         powf32,
 793         powf64,
 794         powif32,
 795         powif64,
 796         pre_dash_lto: "pre-lto",
 797         precise_pointer_size_matching,
 798         precision,
 799         pref_align_of,
 800         prefetch_read_data,
 801         prefetch_read_instruction,
 802         prefetch_write_data,
 803         prefetch_write_instruction,
 804         prelude,
 805         prelude_import,
 806         preserves_flags,
 807         primitive,
 808         proc_dash_macro: "proc-macro",
 809         proc_macro,
 810         proc_macro_attribute,
 811         proc_macro_def_site,
 812         proc_macro_derive,
 813         proc_macro_expr,
 814         proc_macro_gen,
 815         proc_macro_hygiene,
 816         proc_macro_internals,
 817         proc_macro_mod,
 818         proc_macro_non_items,
 819         proc_macro_path_invoc,
 820         profiler_builtins,
 821         profiler_runtime,
 822         ptr_guaranteed_eq,
 823         ptr_guaranteed_ne,
 824         ptr_offset_from,
 825         pub_restricted,
 826         pure,
 827         pushpop_unsafe,
 828         quad_precision_float,
 829         question_mark,
 830         quote,
 831         range_inclusive_new,
 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, Encodable, Decodable)]
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 /// This is the most general way to print identifiers.
1293 /// AST pretty-printer is used as a fallback for turning AST structures into token streams for
1294 /// proc macros. Additionally, proc macros may stringify their input and expect it survive the
1295 /// stringification (especially true for proc macro derives written between Rust 1.15 and 1.30).
1296 /// So we need to somehow pretty-print `$crate` in a way preserving at least some of its
1297 /// hygiene data, most importantly name of the crate it refers to.
1298 /// As a result we print `$crate` as `crate` if it refers to the local crate
1299 /// and as `::other_crate_name` if it refers to some other crate.
1300 /// Note, that this is only done if the ident token is printed from inside of AST pretty-pringing,
1301 /// but not otherwise. Pretty-printing is the only way for proc macros to discover token contents,
1302 /// so we should not perform this lossy conversion if the top level call to the pretty-printer was
1303 /// done for a token stream or a single token.
1304 pub struct IdentPrinter {
1305     symbol: Symbol,
1306     is_raw: bool,
1307     /// Span used for retrieving the crate name to which `$crate` refers to,
1308     /// if this field is `None` then the `$crate` conversion doesn't happen.
1309     convert_dollar_crate: Option<Span>,
1310 }
1311
1312 impl IdentPrinter {
1313     /// The most general `IdentPrinter` constructor. Do not use this.
1314     pub fn new(symbol: Symbol, is_raw: bool, convert_dollar_crate: Option<Span>) -> IdentPrinter {
1315         IdentPrinter { symbol, is_raw, convert_dollar_crate }
1316     }
1317
1318     /// This implementation is supposed to be used when printing identifiers
1319     /// as a part of pretty-printing for larger AST pieces.
1320     /// Do not use this either.
1321     pub fn for_ast_ident(ident: Ident, is_raw: bool) -> IdentPrinter {
1322         IdentPrinter::new(ident.name, is_raw, Some(ident.span))
1323     }
1324 }
1325
1326 impl fmt::Display for IdentPrinter {
1327     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1328         if self.is_raw {
1329             f.write_str("r#")?;
1330         } else {
1331             if self.symbol == kw::DollarCrate {
1332                 if let Some(span) = self.convert_dollar_crate {
1333                     let converted = span.ctxt().dollar_crate_name();
1334                     if !converted.is_path_segment_keyword() {
1335                         f.write_str("::")?;
1336                     }
1337                     return fmt::Display::fmt(&converted, f);
1338                 }
1339             }
1340         }
1341         fmt::Display::fmt(&self.symbol, f)
1342     }
1343 }
1344
1345 /// An newtype around `Ident` that calls [Ident::normalize_to_macro_rules] on
1346 /// construction.
1347 // FIXME(matthewj, petrochenkov) Use this more often, add a similar
1348 // `ModernIdent` struct and use that as well.
1349 #[derive(Copy, Clone, Eq, PartialEq, Hash)]
1350 pub struct MacroRulesNormalizedIdent(Ident);
1351
1352 impl MacroRulesNormalizedIdent {
1353     pub fn new(ident: Ident) -> Self {
1354         Self(ident.normalize_to_macro_rules())
1355     }
1356 }
1357
1358 impl fmt::Debug for MacroRulesNormalizedIdent {
1359     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1360         fmt::Debug::fmt(&self.0, f)
1361     }
1362 }
1363
1364 impl fmt::Display for MacroRulesNormalizedIdent {
1365     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1366         fmt::Display::fmt(&self.0, f)
1367     }
1368 }
1369
1370 /// An interned string.
1371 ///
1372 /// Internally, a `Symbol` is implemented as an index, and all operations
1373 /// (including hashing, equality, and ordering) operate on that index. The use
1374 /// of `rustc_index::newtype_index!` means that `Option<Symbol>` only takes up 4 bytes,
1375 /// because `rustc_index::newtype_index!` reserves the last 256 values for tagging purposes.
1376 ///
1377 /// Note that `Symbol` cannot directly be a `rustc_index::newtype_index!` because it
1378 /// implements `fmt::Debug`, `Encodable`, and `Decodable` in special ways.
1379 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
1380 pub struct Symbol(SymbolIndex);
1381
1382 rustc_index::newtype_index! {
1383     pub struct SymbolIndex { .. }
1384 }
1385
1386 impl Symbol {
1387     const fn new(n: u32) -> Self {
1388         Symbol(SymbolIndex::from_u32(n))
1389     }
1390
1391     /// Maps a string to its interned representation.
1392     pub fn intern(string: &str) -> Self {
1393         with_interner(|interner| interner.intern(string))
1394     }
1395
1396     /// Access the symbol's chars. This is a slowish operation because it
1397     /// requires locking the symbol interner.
1398     pub fn with<F: FnOnce(&str) -> R, R>(self, f: F) -> R {
1399         with_interner(|interner| f(interner.get(self)))
1400     }
1401
1402     /// Convert to a `SymbolStr`. This is a slowish operation because it
1403     /// requires locking the symbol interner.
1404     pub fn as_str(self) -> SymbolStr {
1405         with_interner(|interner| unsafe {
1406             SymbolStr { string: std::mem::transmute::<&str, &str>(interner.get(self)) }
1407         })
1408     }
1409
1410     pub fn as_u32(self) -> u32 {
1411         self.0.as_u32()
1412     }
1413
1414     /// This method is supposed to be used in error messages, so it's expected to be
1415     /// identical to printing the original identifier token written in source code
1416     /// (`token_to_string`, `Ident::to_string`), except that symbols don't keep the rawness flag
1417     /// or edition, so we have to guess the rawness using the global edition.
1418     pub fn to_ident_string(self) -> String {
1419         Ident::with_dummy_span(self).to_string()
1420     }
1421 }
1422
1423 impl fmt::Debug for Symbol {
1424     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1425         self.with(|str| fmt::Debug::fmt(&str, f))
1426     }
1427 }
1428
1429 impl fmt::Display for Symbol {
1430     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1431         self.with(|str| fmt::Display::fmt(&str, f))
1432     }
1433 }
1434
1435 impl<S: Encoder> Encodable<S> for Symbol {
1436     fn encode(&self, s: &mut S) -> Result<(), S::Error> {
1437         self.with(|string| s.emit_str(string))
1438     }
1439 }
1440
1441 impl<D: Decoder> Decodable<D> for Symbol {
1442     #[inline]
1443     fn decode(d: &mut D) -> Result<Symbol, D::Error> {
1444         Ok(Symbol::intern(&d.read_str()?))
1445     }
1446 }
1447
1448 impl<CTX> HashStable<CTX> for Symbol {
1449     #[inline]
1450     fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
1451         self.as_str().hash_stable(hcx, hasher);
1452     }
1453 }
1454
1455 impl<CTX> ToStableHashKey<CTX> for Symbol {
1456     type KeyType = SymbolStr;
1457
1458     #[inline]
1459     fn to_stable_hash_key(&self, _: &CTX) -> SymbolStr {
1460         self.as_str()
1461     }
1462 }
1463
1464 // The `&'static str`s in this type actually point into the arena.
1465 //
1466 // The `FxHashMap`+`Vec` pair could be replaced by `FxIndexSet`, but #75278
1467 // found that to regress performance up to 2% in some cases. This might be
1468 // revisited after further improvements to `indexmap`.
1469 #[derive(Default)]
1470 pub struct Interner {
1471     arena: DroplessArena,
1472     names: FxHashMap<&'static str, Symbol>,
1473     strings: Vec<&'static str>,
1474 }
1475
1476 impl Interner {
1477     fn prefill(init: &[&'static str]) -> Self {
1478         Interner {
1479             strings: init.into(),
1480             names: init.iter().copied().zip((0..).map(Symbol::new)).collect(),
1481             ..Default::default()
1482         }
1483     }
1484
1485     #[inline]
1486     pub fn intern(&mut self, string: &str) -> Symbol {
1487         if let Some(&name) = self.names.get(string) {
1488             return name;
1489         }
1490
1491         let name = Symbol::new(self.strings.len() as u32);
1492
1493         // `from_utf8_unchecked` is safe since we just allocated a `&str` which is known to be
1494         // UTF-8.
1495         let string: &str =
1496             unsafe { str::from_utf8_unchecked(self.arena.alloc_slice(string.as_bytes())) };
1497         // It is safe to extend the arena allocation to `'static` because we only access
1498         // these while the arena is still alive.
1499         let string: &'static str = unsafe { &*(string as *const str) };
1500         self.strings.push(string);
1501         self.names.insert(string, name);
1502         name
1503     }
1504
1505     // Get the symbol as a string. `Symbol::as_str()` should be used in
1506     // preference to this function.
1507     pub fn get(&self, symbol: Symbol) -> &str {
1508         self.strings[symbol.0.as_usize()]
1509     }
1510 }
1511
1512 // This module has a very short name because it's used a lot.
1513 /// This module contains all the defined keyword `Symbol`s.
1514 ///
1515 /// Given that `kw` is imported, use them like `kw::keyword_name`.
1516 /// For example `kw::Loop` or `kw::Break`.
1517 pub mod kw {
1518     use super::Symbol;
1519     keywords!();
1520 }
1521
1522 // This module has a very short name because it's used a lot.
1523 /// This module contains all the defined non-keyword `Symbol`s.
1524 ///
1525 /// Given that `sym` is imported, use them like `sym::symbol_name`.
1526 /// For example `sym::rustfmt` or `sym::u8`.
1527 #[allow(rustc::default_hash_types)]
1528 pub mod sym {
1529     use super::Symbol;
1530     use std::convert::TryInto;
1531
1532     define_symbols!();
1533
1534     // Used from a macro in `librustc_feature/accepted.rs`
1535     pub use super::kw::MacroRules as macro_rules;
1536
1537     // Get the symbol for an integer. The first few non-negative integers each
1538     // have a static symbol and therefore are fast.
1539     pub fn integer<N: TryInto<usize> + Copy + ToString>(n: N) -> Symbol {
1540         if let Result::Ok(idx) = n.try_into() {
1541             if let Option::Some(&sym_) = digits_array.get(idx) {
1542                 return sym_;
1543             }
1544         }
1545         Symbol::intern(&n.to_string())
1546     }
1547 }
1548
1549 impl Symbol {
1550     fn is_used_keyword_2018(self) -> bool {
1551         self >= kw::Async && self <= kw::Dyn
1552     }
1553
1554     fn is_unused_keyword_2018(self) -> bool {
1555         self == kw::Try
1556     }
1557
1558     /// Used for sanity checking rustdoc keyword sections.
1559     pub fn is_doc_keyword(self) -> bool {
1560         self <= kw::Union
1561     }
1562
1563     /// A keyword or reserved identifier that can be used as a path segment.
1564     pub fn is_path_segment_keyword(self) -> bool {
1565         self == kw::Super
1566             || self == kw::SelfLower
1567             || self == kw::SelfUpper
1568             || self == kw::Crate
1569             || self == kw::PathRoot
1570             || self == kw::DollarCrate
1571     }
1572
1573     /// Returns `true` if the symbol is `true` or `false`.
1574     pub fn is_bool_lit(self) -> bool {
1575         self == kw::True || self == kw::False
1576     }
1577
1578     /// This symbol can be a raw identifier.
1579     pub fn can_be_raw(self) -> bool {
1580         self != kw::Invalid && self != kw::Underscore && !self.is_path_segment_keyword()
1581     }
1582 }
1583
1584 impl Ident {
1585     // Returns `true` for reserved identifiers used internally for elided lifetimes,
1586     // unnamed method parameters, crate root module, error recovery etc.
1587     pub fn is_special(self) -> bool {
1588         self.name <= kw::Underscore
1589     }
1590
1591     /// Returns `true` if the token is a keyword used in the language.
1592     pub fn is_used_keyword(self) -> bool {
1593         // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
1594         self.name >= kw::As && self.name <= kw::While
1595             || self.name.is_used_keyword_2018() && self.span.rust_2018()
1596     }
1597
1598     /// Returns `true` if the token is a keyword reserved for possible future use.
1599     pub fn is_unused_keyword(self) -> bool {
1600         // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
1601         self.name >= kw::Abstract && self.name <= kw::Yield
1602             || self.name.is_unused_keyword_2018() && self.span.rust_2018()
1603     }
1604
1605     /// Returns `true` if the token is either a special identifier or a keyword.
1606     pub fn is_reserved(self) -> bool {
1607         self.is_special() || self.is_used_keyword() || self.is_unused_keyword()
1608     }
1609
1610     /// A keyword or reserved identifier that can be used as a path segment.
1611     pub fn is_path_segment_keyword(self) -> bool {
1612         self.name.is_path_segment_keyword()
1613     }
1614
1615     /// We see this identifier in a normal identifier position, like variable name or a type.
1616     /// How was it written originally? Did it use the raw form? Let's try to guess.
1617     pub fn is_raw_guess(self) -> bool {
1618         self.name.can_be_raw() && self.is_reserved()
1619     }
1620 }
1621
1622 #[inline]
1623 fn with_interner<T, F: FnOnce(&mut Interner) -> T>(f: F) -> T {
1624     SESSION_GLOBALS.with(|session_globals| f(&mut *session_globals.symbol_interner.lock()))
1625 }
1626
1627 /// An alternative to `Symbol`, useful when the chars within the symbol need to
1628 /// be accessed. It deliberately has limited functionality and should only be
1629 /// used for temporary values.
1630 ///
1631 /// Because the interner outlives any thread which uses this type, we can
1632 /// safely treat `string` which points to interner data, as an immortal string,
1633 /// as long as this type never crosses between threads.
1634 //
1635 // FIXME: ensure that the interner outlives any thread which uses `SymbolStr`,
1636 // by creating a new thread right after constructing the interner.
1637 #[derive(Clone, Eq, PartialOrd, Ord)]
1638 pub struct SymbolStr {
1639     string: &'static str,
1640 }
1641
1642 // This impl allows a `SymbolStr` to be directly equated with a `String` or
1643 // `&str`.
1644 impl<T: std::ops::Deref<Target = str>> std::cmp::PartialEq<T> for SymbolStr {
1645     fn eq(&self, other: &T) -> bool {
1646         self.string == other.deref()
1647     }
1648 }
1649
1650 impl !Send for SymbolStr {}
1651 impl !Sync for SymbolStr {}
1652
1653 /// This impl means that if `ss` is a `SymbolStr`:
1654 /// - `*ss` is a `str`;
1655 /// - `&*ss` is a `&str` (and `match &*ss { ... }` is a common pattern).
1656 /// - `&ss as &str` is a `&str`, which means that `&ss` can be passed to a
1657 ///   function expecting a `&str`.
1658 impl std::ops::Deref for SymbolStr {
1659     type Target = str;
1660     #[inline]
1661     fn deref(&self) -> &str {
1662         self.string
1663     }
1664 }
1665
1666 impl fmt::Debug for SymbolStr {
1667     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1668         fmt::Debug::fmt(self.string, f)
1669     }
1670 }
1671
1672 impl fmt::Display for SymbolStr {
1673     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1674         fmt::Display::fmt(self.string, f)
1675     }
1676 }
1677
1678 impl<CTX> HashStable<CTX> for SymbolStr {
1679     #[inline]
1680     fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
1681         self.string.hash_stable(hcx, hasher)
1682     }
1683 }
1684
1685 impl<CTX> ToStableHashKey<CTX> for SymbolStr {
1686     type KeyType = SymbolStr;
1687
1688     #[inline]
1689     fn to_stable_hash_key(&self, _: &CTX) -> SymbolStr {
1690         self.clone()
1691     }
1692 }