compiler/rustc_span/src/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_data_structures::sync::Lock;
   9 use rustc_macros::HashStable_Generic;
  10 use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
  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::{with_session_globals, Edition, Span, DUMMY_SP};
  18
  19 #[cfg(test)]
  20 mod tests;
  21
  22 // The proc macro code for this is in `compiler/rustc_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         Empty:              "",
  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         Yeet:               "yeet",
 105     }
 106
 107     // Pre-interned symbols that can be referred to with `rustc_span::sym::*`.
 108     //
 109     // The symbol is the stringified identifier unless otherwise specified, in
 110     // which case the name should mention the non-identifier punctuation.
 111     // E.g. `sym::proc_dash_macro` represents "proc-macro", and it shouldn't be
 112     // called `sym::proc_macro` because then it's easy to mistakenly think it
 113     // represents "proc_macro".
 114     //
 115     // As well as the symbols listed, there are symbols for the strings
 116     // "0", "1", ..., "9", which are accessible via `sym::integer`.
 117     //
 118     // The proc macro will abort if symbols are not in alphabetical order (as
 119     // defined by `impl Ord for str`) or if any symbols are duplicated. Vim
 120     // users can sort the list by selecting it and executing the command
 121     // `:'<,'>!LC_ALL=C sort`.
 122     //
 123     // There is currently no checking that all symbols are used; that would be
 124     // nice to have.
 125     Symbols {
 126         AcqRel,
 127         Acquire,
 128         AddSubdiagnostic,
 129         Alignment,
 130         Any,
 131         Arc,
 132         Argument,
 133         ArgumentV1,
 134         ArgumentV1Methods,
 135         Arguments,
 136         AsMut,
 137         AsRef,
 138         AssertParamIsClone,
 139         AssertParamIsCopy,
 140         AssertParamIsEq,
 141         AtomicBool,
 142         AtomicI128,
 143         AtomicI16,
 144         AtomicI32,
 145         AtomicI64,
 146         AtomicI8,
 147         AtomicIsize,
 148         AtomicPtr,
 149         AtomicU128,
 150         AtomicU16,
 151         AtomicU32,
 152         AtomicU64,
 153         AtomicU8,
 154         AtomicUsize,
 155         BTreeEntry,
 156         BTreeMap,
 157         BTreeSet,
 158         BinaryHeap,
 159         Borrow,
 160         BorrowMut,
 161         Break,
 162         C,
 163         CStr,
 164         CString,
 165         Capture,
 166         Center,
 167         Clone,
 168         Continue,
 169         Copy,
 170         Count,
 171         Cow,
 172         Debug,
 173         DebugStruct,
 174         DebugTuple,
 175         Decodable,
 176         Decoder,
 177         DecorateLint,
 178         Default,
 179         Deref,
 180         DiagnosticMessage,
 181         DirBuilder,
 182         Display,
 183         DoubleEndedIterator,
 184         Duration,
 185         Encodable,
 186         Encoder,
 187         Eq,
 188         Equal,
 189         Err,
 190         Error,
 191         File,
 192         FileType,
 193         Fn,
 194         FnMut,
 195         FnOnce,
 196         FormatSpec,
 197         Formatter,
 198         From,
 199         FromIterator,
 200         FromResidual,
 201         Future,
 202         FxHashMap,
 203         FxHashSet,
 204         GlobalAlloc,
 205         Hash,
 206         HashMap,
 207         HashMapEntry,
 208         HashSet,
 209         Hasher,
 210         Implied,
 211         Input,
 212         Into,
 213         IntoFuture,
 214         IntoIterator,
 215         IoRead,
 216         IoWrite,
 217         IrTyKind,
 218         Is,
 219         ItemContext,
 220         Iterator,
 221         Layout,
 222         Left,
 223         LinkedList,
 224         LintPass,
 225         Mutex,
 226         MutexGuard,
 227         N,
 228         NonZeroI128,
 229         NonZeroI16,
 230         NonZeroI32,
 231         NonZeroI64,
 232         NonZeroI8,
 233         NonZeroU128,
 234         NonZeroU16,
 235         NonZeroU32,
 236         NonZeroU64,
 237         NonZeroU8,
 238         None,
 239         Ok,
 240         Option,
 241         Ord,
 242         Ordering,
 243         OsStr,
 244         OsString,
 245         Output,
 246         Param,
 247         PartialEq,
 248         PartialOrd,
 249         Path,
 250         PathBuf,
 251         Pending,
 252         Pin,
 253         Pointer,
 254         Poll,
 255         ProcMacro,
 256         ProcMacroHack,
 257         ProceduralMasqueradeDummyType,
 258         Range,
 259         RangeFrom,
 260         RangeFull,
 261         RangeInclusive,
 262         RangeTo,
 263         RangeToInclusive,
 264         Rc,
 265         Ready,
 266         Receiver,
 267         Relaxed,
 268         Release,
 269         Result,
 270         Return,
 271         Right,
 272         Rust,
 273         RustcDecodable,
 274         RustcEncodable,
 275         RwLockReadGuard,
 276         RwLockWriteGuard,
 277         Send,
 278         SeqCst,
 279         SessionDiagnostic,
 280         SliceIndex,
 281         Some,
 282         String,
 283         StructuralEq,
 284         StructuralPartialEq,
 285         SubdiagnosticMessage,
 286         Sync,
 287         T,
 288         Target,
 289         ToOwned,
 290         ToString,
 291         Try,
 292         TryCaptureGeneric,
 293         TryCapturePrintable,
 294         TryFrom,
 295         TryInto,
 296         Ty,
 297         TyCtxt,
 298         TyKind,
 299         Unknown,
 300         UnsafeArg,
 301         Vec,
 302         VecDeque,
 303         Wrapper,
 304         Yield,
 305         _DECLS,
 306         _Self,
 307         __D,
 308         __H,
 309         __S,
 310         __awaitee,
 311         __try_var,
 312         _d,
 313         _e,
 314         _task_context,
 315         a32,
 316         aarch64_target_feature,
 317         aarch64_ver_target_feature,
 318         abi,
 319         abi_amdgpu_kernel,
 320         abi_avr_interrupt,
 321         abi_c_cmse_nonsecure_call,
 322         abi_efiapi,
 323         abi_msp430_interrupt,
 324         abi_ptx,
 325         abi_sysv64,
 326         abi_thiscall,
 327         abi_unadjusted,
 328         abi_vectorcall,
 329         abi_x86_interrupt,
 330         abort,
 331         aborts,
 332         add,
 333         add_assign,
 334         add_with_overflow,
 335         address,
 336         adt_const_params,
 337         advanced_slice_patterns,
 338         adx_target_feature,
 339         alias,
 340         align,
 341         align_offset,
 342         alignment,
 343         alignstack,
 344         all,
 345         alloc,
 346         alloc_error_handler,
 347         alloc_layout,
 348         alloc_zeroed,
 349         allocator,
 350         allocator_api,
 351         allocator_internals,
 352         allow,
 353         allow_fail,
 354         allow_internal_unsafe,
 355         allow_internal_unstable,
 356         allowed,
 357         alu32,
 358         always,
 359         and,
 360         and_then,
 361         anonymous_lifetime_in_impl_trait,
 362         any,
 363         append_const_msg,
 364         arbitrary_enum_discriminant,
 365         arbitrary_self_types,
 366         args,
 367         arith_offset,
 368         arm,
 369         arm_target_feature,
 370         array,
 371         arrays,
 372         as_ptr,
 373         as_ref,
 374         as_str,
 375         asm,
 376         asm_const,
 377         asm_experimental_arch,
 378         asm_sym,
 379         asm_unwind,
 380         assert,
 381         assert_eq_macro,
 382         assert_inhabited,
 383         assert_macro,
 384         assert_ne_macro,
 385         assert_receiver_is_total_eq,
 386         assert_uninit_valid,
 387         assert_zero_valid,
 388         asserting,
 389         associated_const_equality,
 390         associated_consts,
 391         associated_type_bounds,
 392         associated_type_defaults,
 393         associated_types,
 394         assume,
 395         assume_init,
 396         async_await,
 397         async_closure,
 398         atomic,
 399         atomic_mod,
 400         atomics,
 401         att_syntax,
 402         attr,
 403         attr_literals,
 404         attributes,
 405         augmented_assignments,
 406         auto_traits,
 407         automatically_derived,
 408         avx,
 409         avx512_target_feature,
 410         avx512bw,
 411         avx512f,
 412         await_macro,
 413         bang,
 414         begin_panic,
 415         bench,
 416         bin,
 417         bind_by_move_pattern_guards,
 418         bindings_after_at,
 419         bitand,
 420         bitand_assign,
 421         bitor,
 422         bitor_assign,
 423         bitreverse,
 424         bitxor,
 425         bitxor_assign,
 426         black_box,
 427         block,
 428         bool,
 429         borrowck_graphviz_format,
 430         borrowck_graphviz_postflow,
 431         borrowck_graphviz_preflow,
 432         box_free,
 433         box_patterns,
 434         box_syntax,
 435         bpf_target_feature,
 436         braced_empty_structs,
 437         branch,
 438         breakpoint,
 439         bridge,
 440         bswap,
 441         c_str,
 442         c_unwind,
 443         c_variadic,
 444         call,
 445         call_mut,
 446         call_once,
 447         caller_location,
 448         capture_disjoint_fields,
 449         cdylib,
 450         ceilf32,
 451         ceilf64,
 452         cfg,
 453         cfg_accessible,
 454         cfg_attr,
 455         cfg_attr_multi,
 456         cfg_doctest,
 457         cfg_eval,
 458         cfg_hide,
 459         cfg_macro,
 460         cfg_panic,
 461         cfg_sanitize,
 462         cfg_target_abi,
 463         cfg_target_compact,
 464         cfg_target_feature,
 465         cfg_target_has_atomic,
 466         cfg_target_has_atomic_equal_alignment,
 467         cfg_target_has_atomic_load_store,
 468         cfg_target_thread_local,
 469         cfg_target_vendor,
 470         cfg_version,
 471         cfi,
 472         char,
 473         client,
 474         clippy,
 475         clobber_abi,
 476         clone,
 477         clone_closures,
 478         clone_from,
 479         closure,
 480         closure_lifetime_binder,
 481         closure_to_fn_coercion,
 482         closure_track_caller,
 483         cmp,
 484         cmp_max,
 485         cmp_min,
 486         cmpxchg16b_target_feature,
 487         cmse_nonsecure_entry,
 488         coerce_unsized,
 489         cold,
 490         column,
 491         column_macro,
 492         compare_and_swap,
 493         compare_exchange,
 494         compare_exchange_weak,
 495         compile_error,
 496         compile_error_macro,
 497         compiler,
 498         compiler_builtins,
 499         compiler_fence,
 500         concat,
 501         concat_bytes,
 502         concat_idents,
 503         concat_macro,
 504         conservative_impl_trait,
 505         console,
 506         const_allocate,
 507         const_async_blocks,
 508         const_compare_raw_pointers,
 509         const_constructor,
 510         const_deallocate,
 511         const_eval_limit,
 512         const_eval_select,
 513         const_evaluatable_checked,
 514         const_extern_fn,
 515         const_fn,
 516         const_fn_floating_point_arithmetic,
 517         const_fn_fn_ptr_basics,
 518         const_fn_trait_bound,
 519         const_fn_transmute,
 520         const_fn_union,
 521         const_fn_unsize,
 522         const_for,
 523         const_format_args,
 524         const_generic_defaults,
 525         const_generics,
 526         const_generics_defaults,
 527         const_if_match,
 528         const_impl_trait,
 529         const_in_array_repeat_expressions,
 530         const_indexing,
 531         const_let,
 532         const_loop,
 533         const_mut_refs,
 534         const_panic,
 535         const_panic_fmt,
 536         const_precise_live_drops,
 537         const_raw_ptr_deref,
 538         const_raw_ptr_to_usize_cast,
 539         const_refs_to_cell,
 540         const_trait,
 541         const_trait_bound_opt_out,
 542         const_trait_impl,
 543         const_transmute,
 544         const_try,
 545         constant,
 546         constructor,
 547         contents,
 548         context,
 549         convert,
 550         copy,
 551         copy_closures,
 552         copy_nonoverlapping,
 553         copysignf32,
 554         copysignf64,
 555         core,
 556         core_intrinsics,
 557         core_panic,
 558         core_panic_2015_macro,
 559         core_panic_macro,
 560         cosf32,
 561         cosf64,
 562         count,
 563         cr,
 564         crate_id,
 565         crate_in_paths,
 566         crate_local,
 567         crate_name,
 568         crate_type,
 569         crate_visibility_modifier,
 570         crt_dash_static: "crt-static",
 571         cstring_type,
 572         ctlz,
 573         ctlz_nonzero,
 574         ctpop,
 575         cttz,
 576         cttz_nonzero,
 577         custom_attribute,
 578         custom_derive,
 579         custom_inner_attributes,
 580         custom_test_frameworks,
 581         d,
 582         d32,
 583         dbg_macro,
 584         dead_code,
 585         dealloc,
 586         debug,
 587         debug_assert_eq_macro,
 588         debug_assert_macro,
 589         debug_assert_ne_macro,
 590         debug_assertions,
 591         debug_struct,
 592         debug_struct_fields_finish,
 593         debug_trait_builder,
 594         debug_tuple,
 595         debug_tuple_fields_finish,
 596         debugger_visualizer,
 597         decl_macro,
 598         declare_lint_pass,
 599         decode,
 600         default_alloc_error_handler,
 601         default_lib_allocator,
 602         default_method_body_is_const,
 603         default_type_parameter_fallback,
 604         default_type_params,
 605         delay_span_bug_from_inside_query,
 606         deny,
 607         deprecated,
 608         deprecated_safe,
 609         deprecated_suggestion,
 610         deref,
 611         deref_method,
 612         deref_mut,
 613         deref_target,
 614         derive,
 615         derive_default_enum,
 616         destruct,
 617         destructuring_assignment,
 618         diagnostic,
 619         direct,
 620         discriminant_kind,
 621         discriminant_type,
 622         discriminant_value,
 623         dispatch_from_dyn,
 624         display_trait,
 625         div,
 626         div_assign,
 627         doc,
 628         doc_alias,
 629         doc_auto_cfg,
 630         doc_cfg,
 631         doc_cfg_hide,
 632         doc_keyword,
 633         doc_masked,
 634         doc_notable_trait,
 635         doc_primitive,
 636         doc_spotlight,
 637         doctest,
 638         document_private_items,
 639         dotdot: "..",
 640         dotdot_in_tuple_patterns,
 641         dotdoteq_in_patterns,
 642         dreg,
 643         dreg_low16,
 644         dreg_low8,
 645         drop,
 646         drop_in_place,
 647         drop_types_in_const,
 648         dropck_eyepatch,
 649         dropck_parametricity,
 650         dylib,
 651         dyn_metadata,
 652         dyn_trait,
 653         e,
 654         edition_macro_pats,
 655         edition_panic,
 656         eh_catch_typeinfo,
 657         eh_personality,
 658         emit_enum,
 659         emit_enum_variant,
 660         emit_enum_variant_arg,
 661         emit_struct,
 662         emit_struct_field,
 663         enable,
 664         encode,
 665         end,
 666         env,
 667         env_macro,
 668         eprint_macro,
 669         eprintln_macro,
 670         eq,
 671         ermsb_target_feature,
 672         exact_div,
 673         except,
 674         exchange_malloc,
 675         exclusive_range_pattern,
 676         exhaustive_integer_patterns,
 677         exhaustive_patterns,
 678         existential_type,
 679         exp2f32,
 680         exp2f64,
 681         expect,
 682         expected,
 683         expf32,
 684         expf64,
 685         explicit_generic_args_with_impl_trait,
 686         export_name,
 687         expr,
 688         extended_key_value_attributes,
 689         extern_absolute_paths,
 690         extern_crate_item_prelude,
 691         extern_crate_self,
 692         extern_in_paths,
 693         extern_prelude,
 694         extern_types,
 695         external_doc,
 696         f,
 697         f16c_target_feature,
 698         f32,
 699         f64,
 700         fabsf32,
 701         fabsf64,
 702         fadd_fast,
 703         fake_variadic,
 704         fdiv_fast,
 705         feature,
 706         fence,
 707         ferris: "🦀",
 708         fetch_update,
 709         ffi,
 710         ffi_const,
 711         ffi_pure,
 712         ffi_returns_twice,
 713         field,
 714         field_init_shorthand,
 715         file,
 716         file_macro,
 717         fill,
 718         finish,
 719         flags,
 720         float,
 721         float_to_int_unchecked,
 722         floorf32,
 723         floorf64,
 724         fmaf32,
 725         fmaf64,
 726         fmt,
 727         fmt_as_str,
 728         fmt_internals,
 729         fmul_fast,
 730         fn_align,
 731         fn_must_use,
 732         fn_mut,
 733         fn_once,
 734         fn_once_output,
 735         forbid,
 736         forget,
 737         format,
 738         format_args,
 739         format_args_capture,
 740         format_args_macro,
 741         format_args_nl,
 742         format_macro,
 743         fp,
 744         freeze,
 745         freg,
 746         frem_fast,
 747         from,
 748         from_desugaring,
 749         from_generator,
 750         from_iter,
 751         from_method,
 752         from_output,
 753         from_residual,
 754         from_size_align_unchecked,
 755         from_usize,
 756         from_yeet,
 757         fsub_fast,
 758         fundamental,
 759         future,
 760         future_trait,
 761         gdb_script_file,
 762         ge,
 763         gen_future,
 764         gen_kill,
 765         generator,
 766         generator_state,
 767         generators,
 768         generic_arg_infer,
 769         generic_assert,
 770         generic_associated_types,
 771         generic_associated_types_extended,
 772         generic_const_exprs,
 773         generic_param_attrs,
 774         get_context,
 775         global_allocator,
 776         global_asm,
 777         globs,
 778         gt,
 779         half_open_range_patterns,
 780         hash,
 781         hexagon_target_feature,
 782         hidden,
 783         homogeneous_aggregate,
 784         html_favicon_url,
 785         html_logo_url,
 786         html_no_source,
 787         html_playground_url,
 788         html_root_url,
 789         hwaddress,
 790         i,
 791         i128,
 792         i128_type,
 793         i16,
 794         i32,
 795         i64,
 796         i8,
 797         ident,
 798         if_let,
 799         if_let_guard,
 800         if_while_or_patterns,
 801         ignore,
 802         impl_header_lifetime_elision,
 803         impl_lint_pass,
 804         impl_macros,
 805         impl_trait_in_bindings,
 806         implied_by,
 807         import,
 808         import_name_type,
 809         import_shadowing,
 810         imported_main,
 811         in_band_lifetimes,
 812         include,
 813         include_bytes,
 814         include_bytes_macro,
 815         include_macro,
 816         include_str,
 817         include_str_macro,
 818         inclusive_range_syntax,
 819         index,
 820         index_mut,
 821         infer_outlives_requirements,
 822         infer_static_outlives_requirements,
 823         inherent_associated_types,
 824         inherit,
 825         inlateout,
 826         inline,
 827         inline_const,
 828         inline_const_pat,
 829         inout,
 830         instruction_set,
 831         integer_: "integer",
 832         integral,
 833         intel,
 834         into_future,
 835         into_iter,
 836         intra_doc_pointers,
 837         intrinsics,
 838         irrefutable_let_patterns,
 839         isa_attribute,
 840         isize,
 841         issue,
 842         issue_5723_bootstrap,
 843         issue_tracker_base_url,
 844         item,
 845         item_like_imports,
 846         iter,
 847         iter_repeat,
 848         keyword,
 849         kind,
 850         kreg,
 851         kreg0,
 852         label,
 853         label_break_value,
 854         lang,
 855         lang_items,
 856         large_assignments,
 857         lateout,
 858         lazy_normalization_consts,
 859         le,
 860         len,
 861         let_chains,
 862         let_else,
 863         lhs,
 864         lib,
 865         libc,
 866         lifetime,
 867         lifetimes,
 868         likely,
 869         line,
 870         line_macro,
 871         link,
 872         link_args,
 873         link_cfg,
 874         link_llvm_intrinsics,
 875         link_name,
 876         link_ordinal,
 877         link_section,
 878         linkage,
 879         linker,
 880         lint_reasons,
 881         literal,
 882         load,
 883         loaded_from_disk,
 884         local,
 885         local_inner_macros,
 886         log10f32,
 887         log10f64,
 888         log2f32,
 889         log2f64,
 890         log_syntax,
 891         logf32,
 892         logf64,
 893         loop_break_value,
 894         lt,
 895         macro_at_most_once_rep,
 896         macro_attributes_in_derive_output,
 897         macro_escape,
 898         macro_export,
 899         macro_lifetime_matcher,
 900         macro_literal_matcher,
 901         macro_metavar_expr,
 902         macro_reexport,
 903         macro_use,
 904         macro_vis_matcher,
 905         macros_in_extern,
 906         main,
 907         managed_boxes,
 908         manually_drop,
 909         map,
 910         marker,
 911         marker_trait_attr,
 912         masked,
 913         match_beginning_vert,
 914         match_default_bindings,
 915         matches_macro,
 916         maxnumf32,
 917         maxnumf64,
 918         may_dangle,
 919         may_unwind,
 920         maybe_uninit,
 921         maybe_uninit_uninit,
 922         maybe_uninit_zeroed,
 923         mem_discriminant,
 924         mem_drop,
 925         mem_forget,
 926         mem_replace,
 927         mem_size_of,
 928         mem_size_of_val,
 929         mem_uninitialized,
 930         mem_variant_count,
 931         mem_zeroed,
 932         member_constraints,
 933         memory,
 934         memtag,
 935         message,
 936         meta,
 937         metadata_type,
 938         min_align_of,
 939         min_align_of_val,
 940         min_const_fn,
 941         min_const_generics,
 942         min_const_unsafe_fn,
 943         min_specialization,
 944         min_type_alias_impl_trait,
 945         minnumf32,
 946         minnumf64,
 947         mips_target_feature,
 948         miri,
 949         misc,
 950         mmx_reg,
 951         modifiers,
 952         module,
 953         module_path,
 954         module_path_macro,
 955         more_qualified_paths,
 956         more_struct_aliases,
 957         movbe_target_feature,
 958         move_ref_pattern,
 959         move_size_limit,
 960         mul,
 961         mul_assign,
 962         mul_with_overflow,
 963         must_not_suspend,
 964         must_use,
 965         naked,
 966         naked_functions,
 967         name,
 968         names,
 969         native_link_modifiers,
 970         native_link_modifiers_as_needed,
 971         native_link_modifiers_bundle,
 972         native_link_modifiers_verbatim,
 973         native_link_modifiers_whole_archive,
 974         natvis_file,
 975         ne,
 976         nearbyintf32,
 977         nearbyintf64,
 978         needs_allocator,
 979         needs_drop,
 980         needs_panic_runtime,
 981         neg,
 982         negate_unsigned,
 983         negative_impls,
 984         neon,
 985         never,
 986         never_type,
 987         never_type_fallback,
 988         new,
 989         new_unchecked,
 990         next,
 991         nll,
 992         no,
 993         no_builtins,
 994         no_core,
 995         no_coverage,
 996         no_crate_inject,
 997         no_debug,
 998         no_default_passes,
 999         no_implicit_prelude,
1000         no_inline,
1001         no_link,
1002         no_main,
1003         no_mangle,
1004         no_sanitize,
1005         no_stack_check,
1006         no_start,
1007         no_std,
1008         nomem,
1009         non_ascii_idents,
1010         non_exhaustive,
1011         non_exhaustive_omitted_patterns_lint,
1012         non_modrs_mods,
1013         none_error,
1014         nontemporal_store,
1015         noop_method_borrow,
1016         noop_method_clone,
1017         noop_method_deref,
1018         noreturn,
1019         nostack,
1020         not,
1021         notable_trait,
1022         note,
1023         object_safe_for_dispatch,
1024         of,
1025         offset,
1026         omit_gdb_pretty_printer_section,
1027         on,
1028         on_unimplemented,
1029         oom,
1030         opaque,
1031         ops,
1032         opt_out_copy,
1033         optimize,
1034         optimize_attribute,
1035         optin_builtin_traits,
1036         option,
1037         option_env,
1038         option_env_macro,
1039         options,
1040         or,
1041         or_patterns,
1042         other,
1043         out,
1044         overlapping_marker_traits,
1045         owned_box,
1046         packed,
1047         panic,
1048         panic_2015,
1049         panic_2021,
1050         panic_abort,
1051         panic_bounds_check,
1052         panic_display,
1053         panic_fmt,
1054         panic_handler,
1055         panic_impl,
1056         panic_implementation,
1057         panic_info,
1058         panic_location,
1059         panic_no_unwind,
1060         panic_runtime,
1061         panic_str,
1062         panic_unwind,
1063         panicking,
1064         param_attrs,
1065         parent_label,
1066         partial_cmp,
1067         partial_ord,
1068         passes,
1069         pat,
1070         pat_param,
1071         path,
1072         pattern_parentheses,
1073         phantom_data,
1074         pin,
1075         platform_intrinsics,
1076         plugin,
1077         plugin_registrar,
1078         plugins,
1079         pointee_trait,
1080         pointer,
1081         pointer_trait_fmt,
1082         poll,
1083         position,
1084         post_dash_lto: "post-lto",
1085         powerpc_target_feature,
1086         powf32,
1087         powf64,
1088         powif32,
1089         powif64,
1090         pre_dash_lto: "pre-lto",
1091         precise_pointer_size_matching,
1092         precision,
1093         pref_align_of,
1094         prefetch_read_data,
1095         prefetch_read_instruction,
1096         prefetch_write_data,
1097         prefetch_write_instruction,
1098         preg,
1099         prelude,
1100         prelude_import,
1101         preserves_flags,
1102         primitive,
1103         print_macro,
1104         println_macro,
1105         proc_dash_macro: "proc-macro",
1106         proc_macro,
1107         proc_macro_attribute,
1108         proc_macro_def_site,
1109         proc_macro_derive,
1110         proc_macro_expr,
1111         proc_macro_gen,
1112         proc_macro_hygiene,
1113         proc_macro_internals,
1114         proc_macro_mod,
1115         proc_macro_non_items,
1116         proc_macro_path_invoc,
1117         profiler_builtins,
1118         profiler_runtime,
1119         ptr,
1120         ptr_guaranteed_cmp,
1121         ptr_mask,
1122         ptr_null,
1123         ptr_null_mut,
1124         ptr_offset_from,
1125         ptr_offset_from_unsigned,
1126         pub_macro_rules,
1127         pub_restricted,
1128         public,
1129         pure,
1130         pushpop_unsafe,
1131         qreg,
1132         qreg_low4,
1133         qreg_low8,
1134         quad_precision_float,
1135         question_mark,
1136         quote,
1137         range_inclusive_new,
1138         raw_dylib,
1139         raw_eq,
1140         raw_identifiers,
1141         raw_ref_op,
1142         re_rebalance_coherence,
1143         read_enum,
1144         read_enum_variant,
1145         read_enum_variant_arg,
1146         read_struct,
1147         read_struct_field,
1148         readonly,
1149         realloc,
1150         reason,
1151         receiver,
1152         recursion_limit,
1153         reexport_test_harness_main,
1154         ref_unwind_safe_trait,
1155         reference,
1156         reflect,
1157         reg,
1158         reg16,
1159         reg32,
1160         reg64,
1161         reg_abcd,
1162         reg_byte,
1163         reg_iw,
1164         reg_nonzero,
1165         reg_pair,
1166         reg_ptr,
1167         reg_upper,
1168         register_attr,
1169         register_tool,
1170         relaxed_adts,
1171         relaxed_struct_unsize,
1172         rem,
1173         rem_assign,
1174         repr,
1175         repr128,
1176         repr_align,
1177         repr_align_enum,
1178         repr_packed,
1179         repr_simd,
1180         repr_transparent,
1181         require,
1182         residual,
1183         result,
1184         return_position_impl_trait_in_trait,
1185         rhs,
1186         rintf32,
1187         rintf64,
1188         riscv_target_feature,
1189         rlib,
1190         rotate_left,
1191         rotate_right,
1192         roundf32,
1193         roundf64,
1194         rt,
1195         rtm_target_feature,
1196         rust,
1197         rust_2015,
1198         rust_2015_preview,
1199         rust_2018,
1200         rust_2018_preview,
1201         rust_2021,
1202         rust_2021_preview,
1203         rust_2024,
1204         rust_2024_preview,
1205         rust_begin_unwind,
1206         rust_cold_cc,
1207         rust_eh_catch_typeinfo,
1208         rust_eh_personality,
1209         rust_eh_register_frames,
1210         rust_eh_unregister_frames,
1211         rust_oom,
1212         rustc,
1213         rustc_access_level,
1214         rustc_allocator,
1215         rustc_allocator_nounwind,
1216         rustc_allocator_zeroed,
1217         rustc_allow_const_fn_unstable,
1218         rustc_allow_incoherent_impl,
1219         rustc_allowed_through_unstable_modules,
1220         rustc_attrs,
1221         rustc_box,
1222         rustc_builtin_macro,
1223         rustc_capture_analysis,
1224         rustc_clean,
1225         rustc_coherence_is_core,
1226         rustc_const_stable,
1227         rustc_const_unstable,
1228         rustc_conversion_suggestion,
1229         rustc_deallocator,
1230         rustc_def_path,
1231         rustc_default_body_unstable,
1232         rustc_diagnostic_item,
1233         rustc_diagnostic_macros,
1234         rustc_dirty,
1235         rustc_do_not_const_check,
1236         rustc_dummy,
1237         rustc_dump_env_program_clauses,
1238         rustc_dump_program_clauses,
1239         rustc_dump_user_substs,
1240         rustc_dump_vtable,
1241         rustc_error,
1242         rustc_evaluate_where_clauses,
1243         rustc_expected_cgu_reuse,
1244         rustc_has_incoherent_inherent_impls,
1245         rustc_if_this_changed,
1246         rustc_inherit_overflow_checks,
1247         rustc_insignificant_dtor,
1248         rustc_layout,
1249         rustc_layout_scalar_valid_range_end,
1250         rustc_layout_scalar_valid_range_start,
1251         rustc_legacy_const_generics,
1252         rustc_lint_diagnostics,
1253         rustc_lint_opt_deny_field_access,
1254         rustc_lint_opt_ty,
1255         rustc_lint_query_instability,
1256         rustc_macro_transparency,
1257         rustc_main,
1258         rustc_mir,
1259         rustc_must_implement_one_of,
1260         rustc_nonnull_optimization_guaranteed,
1261         rustc_object_lifetime_default,
1262         rustc_on_unimplemented,
1263         rustc_outlives,
1264         rustc_paren_sugar,
1265         rustc_partition_codegened,
1266         rustc_partition_reused,
1267         rustc_pass_by_value,
1268         rustc_peek,
1269         rustc_peek_definite_init,
1270         rustc_peek_liveness,
1271         rustc_peek_maybe_init,
1272         rustc_peek_maybe_uninit,
1273         rustc_polymorphize_error,
1274         rustc_private,
1275         rustc_proc_macro_decls,
1276         rustc_promotable,
1277         rustc_reallocator,
1278         rustc_regions,
1279         rustc_reservation_impl,
1280         rustc_serialize,
1281         rustc_skip_array_during_method_dispatch,
1282         rustc_specialization_trait,
1283         rustc_stable,
1284         rustc_std_internal_symbol,
1285         rustc_strict_coherence,
1286         rustc_symbol_name,
1287         rustc_test_marker,
1288         rustc_then_this_would_need,
1289         rustc_trivial_field_reads,
1290         rustc_unsafe_specialization_marker,
1291         rustc_variance,
1292         rustdoc,
1293         rustdoc_internals,
1294         rustfmt,
1295         rvalue_static_promotion,
1296         s,
1297         safety,
1298         sanitize,
1299         sanitizer_runtime,
1300         saturating_add,
1301         saturating_sub,
1302         self_in_typedefs,
1303         self_struct_ctor,
1304         semitransparent,
1305         shadow_call_stack,
1306         shl,
1307         shl_assign,
1308         should_panic,
1309         shr,
1310         shr_assign,
1311         sig_dfl,
1312         sig_ign,
1313         simd,
1314         simd_add,
1315         simd_and,
1316         simd_arith_offset,
1317         simd_as,
1318         simd_bitmask,
1319         simd_cast,
1320         simd_ceil,
1321         simd_div,
1322         simd_eq,
1323         simd_extract,
1324         simd_fabs,
1325         simd_fcos,
1326         simd_fexp,
1327         simd_fexp2,
1328         simd_ffi,
1329         simd_flog,
1330         simd_flog10,
1331         simd_flog2,
1332         simd_floor,
1333         simd_fma,
1334         simd_fmax,
1335         simd_fmin,
1336         simd_fpow,
1337         simd_fpowi,
1338         simd_fsin,
1339         simd_fsqrt,
1340         simd_gather,
1341         simd_ge,
1342         simd_gt,
1343         simd_insert,
1344         simd_le,
1345         simd_lt,
1346         simd_mul,
1347         simd_ne,
1348         simd_neg,
1349         simd_or,
1350         simd_reduce_add_ordered,
1351         simd_reduce_add_unordered,
1352         simd_reduce_all,
1353         simd_reduce_and,
1354         simd_reduce_any,
1355         simd_reduce_max,
1356         simd_reduce_max_nanless,
1357         simd_reduce_min,
1358         simd_reduce_min_nanless,
1359         simd_reduce_mul_ordered,
1360         simd_reduce_mul_unordered,
1361         simd_reduce_or,
1362         simd_reduce_xor,
1363         simd_rem,
1364         simd_round,
1365         simd_saturating_add,
1366         simd_saturating_sub,
1367         simd_scatter,
1368         simd_select,
1369         simd_select_bitmask,
1370         simd_shl,
1371         simd_shr,
1372         simd_shuffle,
1373         simd_sub,
1374         simd_trunc,
1375         simd_xor,
1376         since,
1377         sinf32,
1378         sinf64,
1379         size,
1380         size_of,
1381         size_of_val,
1382         sized,
1383         skip,
1384         slice,
1385         slice_len_fn,
1386         slice_patterns,
1387         slicing_syntax,
1388         soft,
1389         specialization,
1390         speed,
1391         spotlight,
1392         sqrtf32,
1393         sqrtf64,
1394         sreg,
1395         sreg_low16,
1396         sse,
1397         sse4a_target_feature,
1398         stable,
1399         staged_api,
1400         start,
1401         state,
1402         static_in_const,
1403         static_nobundle,
1404         static_recursion,
1405         staticlib,
1406         std,
1407         std_inject,
1408         std_panic,
1409         std_panic_2015_macro,
1410         std_panic_macro,
1411         stmt,
1412         stmt_expr_attributes,
1413         stop_after_dataflow,
1414         store,
1415         str,
1416         str_split_whitespace,
1417         str_trim,
1418         str_trim_end,
1419         str_trim_start,
1420         strict_provenance,
1421         stringify,
1422         stringify_macro,
1423         struct_field_attributes,
1424         struct_inherit,
1425         struct_variant,
1426         structural_match,
1427         structural_peq,
1428         structural_teq,
1429         sty,
1430         sub,
1431         sub_assign,
1432         sub_with_overflow,
1433         suggestion,
1434         sym,
1435         sync,
1436         t32,
1437         target,
1438         target_abi,
1439         target_arch,
1440         target_endian,
1441         target_env,
1442         target_family,
1443         target_feature,
1444         target_feature_11,
1445         target_has_atomic,
1446         target_has_atomic_equal_alignment,
1447         target_has_atomic_load_store,
1448         target_os,
1449         target_pointer_width,
1450         target_target_vendor,
1451         target_thread_local,
1452         target_vendor,
1453         task,
1454         tbm_target_feature,
1455         termination,
1456         termination_trait,
1457         termination_trait_test,
1458         test,
1459         test_2018_feature,
1460         test_accepted_feature,
1461         test_case,
1462         test_removed_feature,
1463         test_runner,
1464         test_unstable_lint,
1465         then_with,
1466         thread,
1467         thread_local,
1468         thread_local_macro,
1469         thumb2,
1470         thumb_mode: "thumb-mode",
1471         tmm_reg,
1472         to_string,
1473         to_vec,
1474         todo_macro,
1475         tool_attributes,
1476         tool_lints,
1477         trace_macros,
1478         track_caller,
1479         trait_alias,
1480         trait_upcasting,
1481         transmute,
1482         transmute_opts,
1483         transmute_trait,
1484         transparent,
1485         transparent_enums,
1486         transparent_unions,
1487         trivial_bounds,
1488         truncf32,
1489         truncf64,
1490         try_blocks,
1491         try_capture,
1492         try_from,
1493         try_into,
1494         try_trait_v2,
1495         tt,
1496         tuple,
1497         tuple_from_req,
1498         tuple_indexing,
1499         two_phase,
1500         ty,
1501         type_alias_enum_variants,
1502         type_alias_impl_trait,
1503         type_ascription,
1504         type_changing_struct_update,
1505         type_id,
1506         type_length_limit,
1507         type_macros,
1508         type_name,
1509         u128,
1510         u16,
1511         u32,
1512         u64,
1513         u8,
1514         unaligned_volatile_load,
1515         unaligned_volatile_store,
1516         unboxed_closures,
1517         unchecked_add,
1518         unchecked_div,
1519         unchecked_mul,
1520         unchecked_rem,
1521         unchecked_shl,
1522         unchecked_shr,
1523         unchecked_sub,
1524         underscore_const_names,
1525         underscore_imports,
1526         underscore_lifetimes,
1527         uniform_paths,
1528         unimplemented_macro,
1529         unit,
1530         universal_impl_trait,
1531         unix,
1532         unix_sigpipe,
1533         unlikely,
1534         unmarked_api,
1535         unpin,
1536         unreachable,
1537         unreachable_2015,
1538         unreachable_2015_macro,
1539         unreachable_2021,
1540         unreachable_2021_macro,
1541         unreachable_code,
1542         unreachable_display,
1543         unreachable_macro,
1544         unrestricted_attribute_tokens,
1545         unsafe_block_in_unsafe_fn,
1546         unsafe_cell,
1547         unsafe_no_drop_flag,
1548         unsafe_pin_internals,
1549         unsize,
1550         unsized_fn_params,
1551         unsized_locals,
1552         unsized_tuple_coercion,
1553         unstable,
1554         unstable_location_reason_default: "this crate is being loaded from the sysroot, an \
1555                           unstable location; did you mean to load this crate \
1556                           from crates.io via `Cargo.toml` instead?",
1557         untagged_unions,
1558         unused_imports,
1559         unused_qualifications,
1560         unwind,
1561         unwind_attributes,
1562         unwind_safe_trait,
1563         unwrap,
1564         unwrap_or,
1565         use_extern_macros,
1566         use_nested_groups,
1567         used,
1568         used_with_arg,
1569         using,
1570         usize,
1571         v1,
1572         va_arg,
1573         va_copy,
1574         va_end,
1575         va_list,
1576         va_start,
1577         val,
1578         validity,
1579         values,
1580         var,
1581         variant_count,
1582         vec,
1583         vec_macro,
1584         version,
1585         vfp2,
1586         vis,
1587         visible_private_types,
1588         volatile,
1589         volatile_copy_memory,
1590         volatile_copy_nonoverlapping_memory,
1591         volatile_load,
1592         volatile_set_memory,
1593         volatile_store,
1594         vreg,
1595         vreg_low16,
1596         vtable_align,
1597         vtable_size,
1598         warn,
1599         wasm_abi,
1600         wasm_import_module,
1601         wasm_target_feature,
1602         while_let,
1603         width,
1604         windows,
1605         windows_subsystem,
1606         with_negative_coherence,
1607         wrapping_add,
1608         wrapping_mul,
1609         wrapping_sub,
1610         wreg,
1611         write_bytes,
1612         write_macro,
1613         write_str,
1614         writeln_macro,
1615         x87_reg,
1616         xer,
1617         xmm_reg,
1618         yeet_desugar_details,
1619         yeet_expr,
1620         ymm_reg,
1621         zmm_reg,
1622     }
1623 }
1624
1625 #[derive(Copy, Clone, Eq, HashStable_Generic, Encodable, Decodable)]
1626 pub struct Ident {
1627     pub name: Symbol,
1628     pub span: Span,
1629 }
1630
1631 impl Ident {
1632     #[inline]
1633     /// Constructs a new identifier from a symbol and a span.
1634     pub const fn new(name: Symbol, span: Span) -> Ident {
1635         Ident { name, span }
1636     }
1637
1638     /// Constructs a new identifier with a dummy span.
1639     #[inline]
1640     pub const fn with_dummy_span(name: Symbol) -> Ident {
1641         Ident::new(name, DUMMY_SP)
1642     }
1643
1644     #[inline]
1645     pub fn empty() -> Ident {
1646         Ident::with_dummy_span(kw::Empty)
1647     }
1648
1649     /// Maps a string to an identifier with a dummy span.
1650     pub fn from_str(string: &str) -> Ident {
1651         Ident::with_dummy_span(Symbol::intern(string))
1652     }
1653
1654     /// Maps a string and a span to an identifier.
1655     pub fn from_str_and_span(string: &str, span: Span) -> Ident {
1656         Ident::new(Symbol::intern(string), span)
1657     }
1658
1659     /// Replaces `lo` and `hi` with those from `span`, but keep hygiene context.
1660     pub fn with_span_pos(self, span: Span) -> Ident {
1661         Ident::new(self.name, span.with_ctxt(self.span.ctxt()))
1662     }
1663
1664     pub fn without_first_quote(self) -> Ident {
1665         Ident::new(Symbol::intern(self.as_str().trim_start_matches('\'')), self.span)
1666     }
1667
1668     /// "Normalize" ident for use in comparisons using "item hygiene".
1669     /// Identifiers with same string value become same if they came from the same macro 2.0 macro
1670     /// (e.g., `macro` item, but not `macro_rules` item) and stay different if they came from
1671     /// different macro 2.0 macros.
1672     /// Technically, this operation strips all non-opaque marks from ident's syntactic context.
1673     pub fn normalize_to_macros_2_0(self) -> Ident {
1674         Ident::new(self.name, self.span.normalize_to_macros_2_0())
1675     }
1676
1677     /// "Normalize" ident for use in comparisons using "local variable hygiene".
1678     /// Identifiers with same string value become same if they came from the same non-transparent
1679     /// macro (e.g., `macro` or `macro_rules!` items) and stay different if they came from different
1680     /// non-transparent macros.
1681     /// Technically, this operation strips all transparent marks from ident's syntactic context.
1682     pub fn normalize_to_macro_rules(self) -> Ident {
1683         Ident::new(self.name, self.span.normalize_to_macro_rules())
1684     }
1685
1686     /// Access the underlying string. This is a slowish operation because it
1687     /// requires locking the symbol interner.
1688     ///
1689     /// Note that the lifetime of the return value is a lie. See
1690     /// `Symbol::as_str()` for details.
1691     pub fn as_str(&self) -> &str {
1692         self.name.as_str()
1693     }
1694 }
1695
1696 impl PartialEq for Ident {
1697     fn eq(&self, rhs: &Self) -> bool {
1698         self.name == rhs.name && self.span.eq_ctxt(rhs.span)
1699     }
1700 }
1701
1702 impl Hash for Ident {
1703     fn hash<H: Hasher>(&self, state: &mut H) {
1704         self.name.hash(state);
1705         self.span.ctxt().hash(state);
1706     }
1707 }
1708
1709 impl fmt::Debug for Ident {
1710     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1711         fmt::Display::fmt(self, f)?;
1712         fmt::Debug::fmt(&self.span.ctxt(), f)
1713     }
1714 }
1715
1716 /// This implementation is supposed to be used in error messages, so it's expected to be identical
1717 /// to printing the original identifier token written in source code (`token_to_string`),
1718 /// except that AST identifiers don't keep the rawness flag, so we have to guess it.
1719 impl fmt::Display for Ident {
1720     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1721         fmt::Display::fmt(&IdentPrinter::new(self.name, self.is_raw_guess(), None), f)
1722     }
1723 }
1724
1725 /// This is the most general way to print identifiers.
1726 /// AST pretty-printer is used as a fallback for turning AST structures into token streams for
1727 /// proc macros. Additionally, proc macros may stringify their input and expect it survive the
1728 /// stringification (especially true for proc macro derives written between Rust 1.15 and 1.30).
1729 /// So we need to somehow pretty-print `$crate` in a way preserving at least some of its
1730 /// hygiene data, most importantly name of the crate it refers to.
1731 /// As a result we print `$crate` as `crate` if it refers to the local crate
1732 /// and as `::other_crate_name` if it refers to some other crate.
1733 /// Note, that this is only done if the ident token is printed from inside of AST pretty-printing,
1734 /// but not otherwise. Pretty-printing is the only way for proc macros to discover token contents,
1735 /// so we should not perform this lossy conversion if the top level call to the pretty-printer was
1736 /// done for a token stream or a single token.
1737 pub struct IdentPrinter {
1738     symbol: Symbol,
1739     is_raw: bool,
1740     /// Span used for retrieving the crate name to which `$crate` refers to,
1741     /// if this field is `None` then the `$crate` conversion doesn't happen.
1742     convert_dollar_crate: Option<Span>,
1743 }
1744
1745 impl IdentPrinter {
1746     /// The most general `IdentPrinter` constructor. Do not use this.
1747     pub fn new(symbol: Symbol, is_raw: bool, convert_dollar_crate: Option<Span>) -> IdentPrinter {
1748         IdentPrinter { symbol, is_raw, convert_dollar_crate }
1749     }
1750
1751     /// This implementation is supposed to be used when printing identifiers
1752     /// as a part of pretty-printing for larger AST pieces.
1753     /// Do not use this either.
1754     pub fn for_ast_ident(ident: Ident, is_raw: bool) -> IdentPrinter {
1755         IdentPrinter::new(ident.name, is_raw, Some(ident.span))
1756     }
1757 }
1758
1759 impl fmt::Display for IdentPrinter {
1760     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1761         if self.is_raw {
1762             f.write_str("r#")?;
1763         } else if self.symbol == kw::DollarCrate {
1764             if let Some(span) = self.convert_dollar_crate {
1765                 let converted = span.ctxt().dollar_crate_name();
1766                 if !converted.is_path_segment_keyword() {
1767                     f.write_str("::")?;
1768                 }
1769                 return fmt::Display::fmt(&converted, f);
1770             }
1771         }
1772         fmt::Display::fmt(&self.symbol, f)
1773     }
1774 }
1775
1776 /// An newtype around `Ident` that calls [Ident::normalize_to_macro_rules] on
1777 /// construction.
1778 // FIXME(matthewj, petrochenkov) Use this more often, add a similar
1779 // `ModernIdent` struct and use that as well.
1780 #[derive(Copy, Clone, Eq, PartialEq, Hash)]
1781 pub struct MacroRulesNormalizedIdent(Ident);
1782
1783 impl MacroRulesNormalizedIdent {
1784     pub fn new(ident: Ident) -> Self {
1785         Self(ident.normalize_to_macro_rules())
1786     }
1787 }
1788
1789 impl fmt::Debug for MacroRulesNormalizedIdent {
1790     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1791         fmt::Debug::fmt(&self.0, f)
1792     }
1793 }
1794
1795 impl fmt::Display for MacroRulesNormalizedIdent {
1796     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1797         fmt::Display::fmt(&self.0, f)
1798     }
1799 }
1800
1801 /// An interned string.
1802 ///
1803 /// Internally, a `Symbol` is implemented as an index, and all operations
1804 /// (including hashing, equality, and ordering) operate on that index. The use
1805 /// of `rustc_index::newtype_index!` means that `Option<Symbol>` only takes up 4 bytes,
1806 /// because `rustc_index::newtype_index!` reserves the last 256 values for tagging purposes.
1807 ///
1808 /// Note that `Symbol` cannot directly be a `rustc_index::newtype_index!` because it
1809 /// implements `fmt::Debug`, `Encodable`, and `Decodable` in special ways.
1810 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
1811 pub struct Symbol(SymbolIndex);
1812
1813 rustc_index::newtype_index! {
1814     struct SymbolIndex { .. }
1815 }
1816
1817 impl Symbol {
1818     const fn new(n: u32) -> Self {
1819         Symbol(SymbolIndex::from_u32(n))
1820     }
1821
1822     /// for use in Decoder only
1823     pub fn new_from_decoded(n: u32) -> Self {
1824         Self::new(n)
1825     }
1826
1827     /// Maps a string to its interned representation.
1828     pub fn intern(string: &str) -> Self {
1829         with_session_globals(|session_globals| session_globals.symbol_interner.intern(string))
1830     }
1831
1832     /// Access the underlying string. This is a slowish operation because it
1833     /// requires locking the symbol interner.
1834     ///
1835     /// Note that the lifetime of the return value is a lie. It's not the same
1836     /// as `&self`, but actually tied to the lifetime of the underlying
1837     /// interner. Interners are long-lived, and there are very few of them, and
1838     /// this function is typically used for short-lived things, so in practice
1839     /// it works out ok.
1840     pub fn as_str(&self) -> &str {
1841         with_session_globals(|session_globals| unsafe {
1842             std::mem::transmute::<&str, &str>(session_globals.symbol_interner.get(*self))
1843         })
1844     }
1845
1846     pub fn as_u32(self) -> u32 {
1847         self.0.as_u32()
1848     }
1849
1850     pub fn is_empty(self) -> bool {
1851         self == kw::Empty
1852     }
1853
1854     /// This method is supposed to be used in error messages, so it's expected to be
1855     /// identical to printing the original identifier token written in source code
1856     /// (`token_to_string`, `Ident::to_string`), except that symbols don't keep the rawness flag
1857     /// or edition, so we have to guess the rawness using the global edition.
1858     pub fn to_ident_string(self) -> String {
1859         Ident::with_dummy_span(self).to_string()
1860     }
1861 }
1862
1863 impl fmt::Debug for Symbol {
1864     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1865         fmt::Debug::fmt(self.as_str(), f)
1866     }
1867 }
1868
1869 impl fmt::Display for Symbol {
1870     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1871         fmt::Display::fmt(self.as_str(), f)
1872     }
1873 }
1874
1875 impl<S: Encoder> Encodable<S> for Symbol {
1876     default fn encode(&self, s: &mut S) {
1877         s.emit_str(self.as_str());
1878     }
1879 }
1880
1881 impl<D: Decoder> Decodable<D> for Symbol {
1882     #[inline]
1883     default fn decode(d: &mut D) -> Symbol {
1884         Symbol::intern(&d.read_str())
1885     }
1886 }
1887
1888 impl<CTX> HashStable<CTX> for Symbol {
1889     #[inline]
1890     fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
1891         self.as_str().hash_stable(hcx, hasher);
1892     }
1893 }
1894
1895 impl<CTX> ToStableHashKey<CTX> for Symbol {
1896     type KeyType = String;
1897     #[inline]
1898     fn to_stable_hash_key(&self, _: &CTX) -> String {
1899         self.as_str().to_string()
1900     }
1901 }
1902
1903 #[derive(Default)]
1904 pub(crate) struct Interner(Lock<InternerInner>);
1905
1906 // The `&'static str`s in this type actually point into the arena.
1907 //
1908 // The `FxHashMap`+`Vec` pair could be replaced by `FxIndexSet`, but #75278
1909 // found that to regress performance up to 2% in some cases. This might be
1910 // revisited after further improvements to `indexmap`.
1911 //
1912 // This type is private to prevent accidentally constructing more than one
1913 // `Interner` on the same thread, which makes it easy to mix up `Symbol`s
1914 // between `Interner`s.
1915 #[derive(Default)]
1916 struct InternerInner {
1917     arena: DroplessArena,
1918     names: FxHashMap<&'static str, Symbol>,
1919     strings: Vec<&'static str>,
1920 }
1921
1922 impl Interner {
1923     fn prefill(init: &[&'static str]) -> Self {
1924         Interner(Lock::new(InternerInner {
1925             strings: init.into(),
1926             names: init.iter().copied().zip((0..).map(Symbol::new)).collect(),
1927             ..Default::default()
1928         }))
1929     }
1930
1931     #[inline]
1932     fn intern(&self, string: &str) -> Symbol {
1933         let mut inner = self.0.lock();
1934         if let Some(&name) = inner.names.get(string) {
1935             return name;
1936         }
1937
1938         let name = Symbol::new(inner.strings.len() as u32);
1939
1940         // SAFETY: we convert from `&str` to `&[u8]`, clone it into the arena,
1941         // and immediately convert the clone back to `&[u8], all because there
1942         // is no `inner.arena.alloc_str()` method. This is clearly safe.
1943         let string: &str =
1944             unsafe { str::from_utf8_unchecked(inner.arena.alloc_slice(string.as_bytes())) };
1945
1946         // SAFETY: we can extend the arena allocation to `'static` because we
1947         // only access these while the arena is still alive.
1948         let string: &'static str = unsafe { &*(string as *const str) };
1949         inner.strings.push(string);
1950
1951         // This second hash table lookup can be avoided by using `RawEntryMut`,
1952         // but this code path isn't hot enough for it to be worth it. See
1953         // #91445 for details.
1954         inner.names.insert(string, name);
1955         name
1956     }
1957
1958     // Get the symbol as a string. `Symbol::as_str()` should be used in
1959     // preference to this function.
1960     fn get(&self, symbol: Symbol) -> &str {
1961         self.0.lock().strings[symbol.0.as_usize()]
1962     }
1963 }
1964
1965 // This module has a very short name because it's used a lot.
1966 /// This module contains all the defined keyword `Symbol`s.
1967 ///
1968 /// Given that `kw` is imported, use them like `kw::keyword_name`.
1969 /// For example `kw::Loop` or `kw::Break`.
1970 pub mod kw {
1971     pub use super::kw_generated::*;
1972 }
1973
1974 // This module has a very short name because it's used a lot.
1975 /// This module contains all the defined non-keyword `Symbol`s.
1976 ///
1977 /// Given that `sym` is imported, use them like `sym::symbol_name`.
1978 /// For example `sym::rustfmt` or `sym::u8`.
1979 pub mod sym {
1980     use super::Symbol;
1981     use std::convert::TryInto;
1982
1983     #[doc(inline)]
1984     pub use super::sym_generated::*;
1985
1986     // Used from a macro in `librustc_feature/accepted.rs`
1987     pub use super::kw::MacroRules as macro_rules;
1988
1989     /// Get the symbol for an integer.
1990     ///
1991     /// The first few non-negative integers each have a static symbol and therefore
1992     /// are fast.
1993     pub fn integer<N: TryInto<usize> + Copy + ToString>(n: N) -> Symbol {
1994         if let Result::Ok(idx) = n.try_into() {
1995             if idx < 10 {
1996                 return Symbol::new(super::SYMBOL_DIGITS_BASE + idx as u32);
1997             }
1998         }
1999         Symbol::intern(&n.to_string())
2000     }
2001 }
2002
2003 impl Symbol {
2004     fn is_special(self) -> bool {
2005         self <= kw::Underscore
2006     }
2007
2008     fn is_used_keyword_always(self) -> bool {
2009         self >= kw::As && self <= kw::While
2010     }
2011
2012     fn is_used_keyword_conditional(self, edition: impl FnOnce() -> Edition) -> bool {
2013         (self >= kw::Async && self <= kw::Dyn) && edition() >= Edition::Edition2018
2014     }
2015
2016     fn is_unused_keyword_always(self) -> bool {
2017         self >= kw::Abstract && self <= kw::Yield
2018     }
2019
2020     fn is_unused_keyword_conditional(self, edition: impl FnOnce() -> Edition) -> bool {
2021         self == kw::Try && edition() >= Edition::Edition2018
2022     }
2023
2024     pub fn is_reserved(self, edition: impl Copy + FnOnce() -> Edition) -> bool {
2025         self.is_special()
2026             || self.is_used_keyword_always()
2027             || self.is_unused_keyword_always()
2028             || self.is_used_keyword_conditional(edition)
2029             || self.is_unused_keyword_conditional(edition)
2030     }
2031
2032     /// A keyword or reserved identifier that can be used as a path segment.
2033     pub fn is_path_segment_keyword(self) -> bool {
2034         self == kw::Super
2035             || self == kw::SelfLower
2036             || self == kw::SelfUpper
2037             || self == kw::Crate
2038             || self == kw::PathRoot
2039             || self == kw::DollarCrate
2040     }
2041
2042     /// Returns `true` if the symbol is `true` or `false`.
2043     pub fn is_bool_lit(self) -> bool {
2044         self == kw::True || self == kw::False
2045     }
2046
2047     /// Returns `true` if this symbol can be a raw identifier.
2048     pub fn can_be_raw(self) -> bool {
2049         self != kw::Empty && self != kw::Underscore && !self.is_path_segment_keyword()
2050     }
2051
2052     /// Is this symbol was interned in compiler's `symbols!` macro
2053     pub fn is_preinterned(self) -> bool {
2054         self.as_u32() < PREINTERNED_SYMBOLS_COUNT
2055     }
2056 }
2057
2058 impl Ident {
2059     // Returns `true` for reserved identifiers used internally for elided lifetimes,
2060     // unnamed method parameters, crate root module, error recovery etc.
2061     pub fn is_special(self) -> bool {
2062         self.name.is_special()
2063     }
2064
2065     /// Returns `true` if the token is a keyword used in the language.
2066     pub fn is_used_keyword(self) -> bool {
2067         // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
2068         self.name.is_used_keyword_always()
2069             || self.name.is_used_keyword_conditional(|| self.span.edition())
2070     }
2071
2072     /// Returns `true` if the token is a keyword reserved for possible future use.
2073     pub fn is_unused_keyword(self) -> bool {
2074         // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
2075         self.name.is_unused_keyword_always()
2076             || self.name.is_unused_keyword_conditional(|| self.span.edition())
2077     }
2078
2079     /// Returns `true` if the token is either a special identifier or a keyword.
2080     pub fn is_reserved(self) -> bool {
2081         // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
2082         self.name.is_reserved(|| self.span.edition())
2083     }
2084
2085     /// A keyword or reserved identifier that can be used as a path segment.
2086     pub fn is_path_segment_keyword(self) -> bool {
2087         self.name.is_path_segment_keyword()
2088     }
2089
2090     /// We see this identifier in a normal identifier position, like variable name or a type.
2091     /// How was it written originally? Did it use the raw form? Let's try to guess.
2092     pub fn is_raw_guess(self) -> bool {
2093         self.name.can_be_raw() && self.is_reserved()
2094     }
2095 }