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::fmt;
  13 use std::hash::{Hash, Hasher};
  14 use std::str;
  15
  16 use crate::{with_session_globals, Edition, Span, DUMMY_SP};
  17
  18 #[cfg(test)]
  19 mod tests;
  20
  21 // The proc macro code for this is in `compiler/rustc_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         Empty:              "",
  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         Yeet:               "yeet",
 104     }
 105
 106     // Pre-interned symbols that can be referred to with `rustc_span::sym::*`.
 107     //
 108     // The symbol is the stringified identifier unless otherwise specified, in
 109     // which case the name should mention the non-identifier punctuation.
 110     // E.g. `sym::proc_dash_macro` represents "proc-macro", and it shouldn't be
 111     // called `sym::proc_macro` because then it's easy to mistakenly think it
 112     // represents "proc_macro".
 113     //
 114     // As well as the symbols listed, there are symbols for the strings
 115     // "0", "1", ..., "9", which are accessible via `sym::integer`.
 116     //
 117     // The proc macro will abort if symbols are not in alphabetical order (as
 118     // defined by `impl Ord for str`) or if any symbols are duplicated. Vim
 119     // users can sort the list by selecting it and executing the command
 120     // `:'<,'>!LC_ALL=C sort`.
 121     //
 122     // There is currently no checking that all symbols are used; that would be
 123     // nice to have.
 124     Symbols {
 125         AcqRel,
 126         Acquire,
 127         AddToDiagnostic,
 128         Alignment,
 129         Any,
 130         Arc,
 131         Argument,
 132         ArgumentV1,
 133         ArgumentV1Methods,
 134         Arguments,
 135         AsMut,
 136         AsRef,
 137         AssertParamIsClone,
 138         AssertParamIsCopy,
 139         AssertParamIsEq,
 140         AtomicBool,
 141         AtomicI128,
 142         AtomicI16,
 143         AtomicI32,
 144         AtomicI64,
 145         AtomicI8,
 146         AtomicIsize,
 147         AtomicPtr,
 148         AtomicU128,
 149         AtomicU16,
 150         AtomicU32,
 151         AtomicU64,
 152         AtomicU8,
 153         AtomicUsize,
 154         BTreeEntry,
 155         BTreeMap,
 156         BTreeSet,
 157         BinaryHeap,
 158         Borrow,
 159         BorrowMut,
 160         Break,
 161         C,
 162         CStr,
 163         CString,
 164         Capture,
 165         Center,
 166         Clone,
 167         Continue,
 168         Copy,
 169         Count,
 170         Cow,
 171         Debug,
 172         Decodable,
 173         Decoder,
 174         DecorateLint,
 175         Default,
 176         Deref,
 177         DiagnosticMessage,
 178         DirBuilder,
 179         Display,
 180         DoubleEndedIterator,
 181         Duration,
 182         Encodable,
 183         Encoder,
 184         Eq,
 185         Equal,
 186         Err,
 187         Error,
 188         File,
 189         FileType,
 190         FormatSpec,
 191         Formatter,
 192         From,
 193         FromIterator,
 194         FromResidual,
 195         Future,
 196         FxHashMap,
 197         FxHashSet,
 198         GlobalAlloc,
 199         Hash,
 200         HashMap,
 201         HashMapEntry,
 202         HashSet,
 203         Hasher,
 204         Implied,
 205         Input,
 206         Into,
 207         IntoDiagnostic,
 208         IntoIterator,
 209         IoRead,
 210         IoWrite,
 211         IpAddr,
 212         IrTyKind,
 213         Is,
 214         ItemContext,
 215         Iterator,
 216         IteratorItem,
 217         Layout,
 218         Left,
 219         LinkedList,
 220         LintPass,
 221         LocalKey,
 222         Mutex,
 223         MutexGuard,
 224         N,
 225         NonZeroI128,
 226         NonZeroI16,
 227         NonZeroI32,
 228         NonZeroI64,
 229         NonZeroI8,
 230         NonZeroU128,
 231         NonZeroU16,
 232         NonZeroU32,
 233         NonZeroU64,
 234         NonZeroU8,
 235         None,
 236         Ok,
 237         Option,
 238         Ord,
 239         Ordering,
 240         OsStr,
 241         OsString,
 242         Output,
 243         Param,
 244         PartialEq,
 245         PartialOrd,
 246         Path,
 247         PathBuf,
 248         Pending,
 249         Pin,
 250         Pointer,
 251         Poll,
 252         ProcMacro,
 253         ProceduralMasqueradeDummyType,
 254         Range,
 255         RangeFrom,
 256         RangeFull,
 257         RangeInclusive,
 258         RangeTo,
 259         RangeToInclusive,
 260         Rc,
 261         Ready,
 262         Receiver,
 263         RefCell,
 264         Relaxed,
 265         Release,
 266         Result,
 267         ResumeTy,
 268         Return,
 269         Right,
 270         Rust,
 271         RustcDecodable,
 272         RustcEncodable,
 273         RwLock,
 274         RwLockReadGuard,
 275         RwLockWriteGuard,
 276         Send,
 277         SeqCst,
 278         SliceIndex,
 279         Some,
 280         String,
 281         StructuralEq,
 282         StructuralPartialEq,
 283         SubdiagnosticMessage,
 284         Sync,
 285         T,
 286         Target,
 287         ToOwned,
 288         ToString,
 289         Try,
 290         TryCaptureGeneric,
 291         TryCapturePrintable,
 292         TryFrom,
 293         TryInto,
 294         Ty,
 295         TyCtxt,
 296         TyKind,
 297         Unknown,
 298         UnsafeArg,
 299         Vec,
 300         VecDeque,
 301         Wrapper,
 302         Yield,
 303         _DECLS,
 304         _Self,
 305         __D,
 306         __H,
 307         __S,
 308         __awaitee,
 309         __try_var,
 310         _d,
 311         _e,
 312         _task_context,
 313         a32,
 314         aarch64_target_feature,
 315         aarch64_ver_target_feature,
 316         abi,
 317         abi_amdgpu_kernel,
 318         abi_avr_interrupt,
 319         abi_c_cmse_nonsecure_call,
 320         abi_efiapi,
 321         abi_msp430_interrupt,
 322         abi_ptx,
 323         abi_sysv64,
 324         abi_thiscall,
 325         abi_unadjusted,
 326         abi_vectorcall,
 327         abi_x86_interrupt,
 328         abort,
 329         add,
 330         add_assign,
 331         add_with_overflow,
 332         address,
 333         adt_const_params,
 334         advanced_slice_patterns,
 335         adx_target_feature,
 336         alias,
 337         align,
 338         align_offset,
 339         alignment,
 340         all,
 341         alloc,
 342         alloc_error_handler,
 343         alloc_layout,
 344         alloc_zeroed,
 345         allocator,
 346         allocator_api,
 347         allocator_internals,
 348         allow,
 349         allow_fail,
 350         allow_internal_unsafe,
 351         allow_internal_unstable,
 352         allowed,
 353         alu32,
 354         always,
 355         and,
 356         and_then,
 357         anonymous_lifetime_in_impl_trait,
 358         any,
 359         append_const_msg,
 360         arbitrary_enum_discriminant,
 361         arbitrary_self_types,
 362         args,
 363         arith_offset,
 364         arm,
 365         arm_target_feature,
 366         array,
 367         arrays,
 368         as_ptr,
 369         as_ref,
 370         as_str,
 371         asm,
 372         asm_const,
 373         asm_experimental_arch,
 374         asm_sym,
 375         asm_unwind,
 376         assert,
 377         assert_eq_macro,
 378         assert_inhabited,
 379         assert_macro,
 380         assert_mem_uninitialized_valid,
 381         assert_ne_macro,
 382         assert_receiver_is_total_eq,
 383         assert_zero_valid,
 384         asserting,
 385         associated_const_equality,
 386         associated_consts,
 387         associated_type_bounds,
 388         associated_type_defaults,
 389         associated_types,
 390         assume,
 391         assume_init,
 392         async_await,
 393         async_closure,
 394         async_fn_in_trait,
 395         atomic,
 396         atomic_mod,
 397         atomics,
 398         att_syntax,
 399         attr,
 400         attr_literals,
 401         attributes,
 402         augmented_assignments,
 403         auto_traits,
 404         automatically_derived,
 405         avx,
 406         avx512_target_feature,
 407         avx512bw,
 408         avx512f,
 409         await_macro,
 410         bang,
 411         begin_panic,
 412         bench,
 413         bin,
 414         bind_by_move_pattern_guards,
 415         bindings_after_at,
 416         bitand,
 417         bitand_assign,
 418         bitor,
 419         bitor_assign,
 420         bitreverse,
 421         bitxor,
 422         bitxor_assign,
 423         black_box,
 424         block,
 425         bool,
 426         borrowck_graphviz_format,
 427         borrowck_graphviz_postflow,
 428         box_free,
 429         box_patterns,
 430         box_syntax,
 431         bpf_target_feature,
 432         braced_empty_structs,
 433         branch,
 434         breakpoint,
 435         bridge,
 436         bswap,
 437         c_str,
 438         c_unwind,
 439         c_variadic,
 440         call,
 441         call_mut,
 442         call_once,
 443         caller_location,
 444         capture_disjoint_fields,
 445         cause,
 446         cdylib,
 447         ceilf32,
 448         ceilf64,
 449         cfg,
 450         cfg_accessible,
 451         cfg_attr,
 452         cfg_attr_multi,
 453         cfg_doctest,
 454         cfg_eval,
 455         cfg_hide,
 456         cfg_panic,
 457         cfg_sanitize,
 458         cfg_target_abi,
 459         cfg_target_compact,
 460         cfg_target_feature,
 461         cfg_target_has_atomic,
 462         cfg_target_has_atomic_equal_alignment,
 463         cfg_target_thread_local,
 464         cfg_target_vendor,
 465         cfg_version,
 466         cfi,
 467         char,
 468         client,
 469         clippy,
 470         clobber_abi,
 471         clone,
 472         clone_closures,
 473         clone_from,
 474         closure,
 475         closure_lifetime_binder,
 476         closure_to_fn_coercion,
 477         closure_track_caller,
 478         cmp,
 479         cmp_max,
 480         cmp_min,
 481         cmpxchg16b_target_feature,
 482         cmse_nonsecure_entry,
 483         coerce_unsized,
 484         cold,
 485         collapse_debuginfo,
 486         column,
 487         compare_exchange,
 488         compare_exchange_weak,
 489         compile_error,
 490         compiler,
 491         compiler_builtins,
 492         compiler_fence,
 493         concat,
 494         concat_bytes,
 495         concat_idents,
 496         conservative_impl_trait,
 497         console,
 498         const_allocate,
 499         const_async_blocks,
 500         const_compare_raw_pointers,
 501         const_constructor,
 502         const_deallocate,
 503         const_eval_limit,
 504         const_eval_select,
 505         const_evaluatable_checked,
 506         const_extern_fn,
 507         const_fn,
 508         const_fn_floating_point_arithmetic,
 509         const_fn_fn_ptr_basics,
 510         const_fn_trait_bound,
 511         const_fn_transmute,
 512         const_fn_union,
 513         const_fn_unsize,
 514         const_for,
 515         const_format_args,
 516         const_generics,
 517         const_generics_defaults,
 518         const_if_match,
 519         const_impl_trait,
 520         const_in_array_repeat_expressions,
 521         const_indexing,
 522         const_let,
 523         const_loop,
 524         const_mut_refs,
 525         const_panic,
 526         const_panic_fmt,
 527         const_precise_live_drops,
 528         const_raw_ptr_deref,
 529         const_raw_ptr_to_usize_cast,
 530         const_refs_to_cell,
 531         const_trait,
 532         const_trait_bound_opt_out,
 533         const_trait_impl,
 534         const_try,
 535         constant,
 536         constructor,
 537         context,
 538         copy,
 539         copy_closures,
 540         copy_nonoverlapping,
 541         copysignf32,
 542         copysignf64,
 543         core,
 544         core_panic,
 545         core_panic_2015_macro,
 546         core_panic_2021_macro,
 547         core_panic_macro,
 548         cosf32,
 549         cosf64,
 550         count,
 551         cr,
 552         crate_id,
 553         crate_in_paths,
 554         crate_local,
 555         crate_name,
 556         crate_type,
 557         crate_visibility_modifier,
 558         crt_dash_static: "crt-static",
 559         cstring_type,
 560         ctlz,
 561         ctlz_nonzero,
 562         ctpop,
 563         cttz,
 564         cttz_nonzero,
 565         custom_attribute,
 566         custom_derive,
 567         custom_inner_attributes,
 568         custom_mir,
 569         custom_test_frameworks,
 570         d,
 571         d32,
 572         dbg_macro,
 573         dead_code,
 574         dealloc,
 575         debug,
 576         debug_assert_eq_macro,
 577         debug_assert_macro,
 578         debug_assert_ne_macro,
 579         debug_assertions,
 580         debug_struct,
 581         debug_struct_fields_finish,
 582         debug_tuple,
 583         debug_tuple_fields_finish,
 584         debugger_visualizer,
 585         decl_macro,
 586         declare_lint_pass,
 587         decode,
 588         default_alloc_error_handler,
 589         default_lib_allocator,
 590         default_method_body_is_const,
 591         default_type_parameter_fallback,
 592         default_type_params,
 593         delay_span_bug_from_inside_query,
 594         deny,
 595         deprecated,
 596         deprecated_safe,
 597         deprecated_suggestion,
 598         deref,
 599         deref_method,
 600         deref_mut,
 601         deref_target,
 602         derive,
 603         derive_const,
 604         derive_default_enum,
 605         destruct,
 606         destructuring_assignment,
 607         diagnostic,
 608         direct,
 609         discriminant_kind,
 610         discriminant_type,
 611         discriminant_value,
 612         dispatch_from_dyn,
 613         div,
 614         div_assign,
 615         doc,
 616         doc_alias,
 617         doc_auto_cfg,
 618         doc_cfg,
 619         doc_cfg_hide,
 620         doc_keyword,
 621         doc_masked,
 622         doc_notable_trait,
 623         doc_primitive,
 624         doc_spotlight,
 625         doctest,
 626         document_private_items,
 627         dotdot: "..",
 628         dotdot_in_tuple_patterns,
 629         dotdoteq_in_patterns,
 630         dreg,
 631         dreg_low16,
 632         dreg_low8,
 633         drop,
 634         drop_in_place,
 635         drop_types_in_const,
 636         dropck_eyepatch,
 637         dropck_parametricity,
 638         dylib,
 639         dyn_metadata,
 640         dyn_star,
 641         dyn_trait,
 642         e,
 643         edition_panic,
 644         eh_catch_typeinfo,
 645         eh_personality,
 646         emit_enum,
 647         emit_enum_variant,
 648         emit_enum_variant_arg,
 649         emit_struct,
 650         emit_struct_field,
 651         enable,
 652         encode,
 653         end,
 654         env,
 655         eprint_macro,
 656         eprintln_macro,
 657         eq,
 658         ermsb_target_feature,
 659         exact_div,
 660         except,
 661         exchange_malloc,
 662         exclusive_range_pattern,
 663         exhaustive_integer_patterns,
 664         exhaustive_patterns,
 665         existential_type,
 666         exp2f32,
 667         exp2f64,
 668         expect,
 669         expected,
 670         expf32,
 671         expf64,
 672         explicit_generic_args_with_impl_trait,
 673         export_name,
 674         expr,
 675         extended_key_value_attributes,
 676         extended_varargs_abi_support,
 677         extern_absolute_paths,
 678         extern_crate_item_prelude,
 679         extern_crate_self,
 680         extern_in_paths,
 681         extern_prelude,
 682         extern_types,
 683         external_doc,
 684         f,
 685         f16c_target_feature,
 686         f32,
 687         f64,
 688         fabsf32,
 689         fabsf64,
 690         fadd_fast,
 691         fake_variadic,
 692         fdiv_fast,
 693         feature,
 694         fence,
 695         ferris: "🦀",
 696         fetch_update,
 697         ffi,
 698         ffi_const,
 699         ffi_pure,
 700         ffi_returns_twice,
 701         field,
 702         field_init_shorthand,
 703         file,
 704         fill,
 705         flags,
 706         float,
 707         float_to_int_unchecked,
 708         floorf32,
 709         floorf64,
 710         fmaf32,
 711         fmaf64,
 712         fmt,
 713         fmul_fast,
 714         fn_align,
 715         fn_must_use,
 716         fn_mut,
 717         fn_once,
 718         fn_once_output,
 719         forbid,
 720         forget,
 721         format,
 722         format_args,
 723         format_args_capture,
 724         format_args_macro,
 725         format_args_nl,
 726         format_macro,
 727         freeze,
 728         freg,
 729         frem_fast,
 730         from,
 731         from_desugaring,
 732         from_iter,
 733         from_method,
 734         from_output,
 735         from_residual,
 736         from_size_align_unchecked,
 737         from_usize,
 738         from_yeet,
 739         fsub_fast,
 740         fundamental,
 741         future,
 742         future_trait,
 743         gdb_script_file,
 744         ge,
 745         gen_future,
 746         gen_kill,
 747         generator,
 748         generator_clone,
 749         generator_state,
 750         generators,
 751         generic_arg_infer,
 752         generic_assert,
 753         generic_associated_types,
 754         generic_associated_types_extended,
 755         generic_const_exprs,
 756         generic_param_attrs,
 757         get_context,
 758         global_allocator,
 759         global_asm,
 760         globs,
 761         gt,
 762         half_open_range_patterns,
 763         half_open_range_patterns_in_slices,
 764         hash,
 765         hexagon_target_feature,
 766         hidden,
 767         homogeneous_aggregate,
 768         html_favicon_url,
 769         html_logo_url,
 770         html_no_source,
 771         html_playground_url,
 772         html_root_url,
 773         hwaddress,
 774         i,
 775         i128,
 776         i128_type,
 777         i16,
 778         i32,
 779         i64,
 780         i8,
 781         ident,
 782         identity_future,
 783         if_let,
 784         if_let_guard,
 785         if_while_or_patterns,
 786         ignore,
 787         impl_header_lifetime_elision,
 788         impl_lint_pass,
 789         impl_trait_in_bindings,
 790         impl_trait_in_fn_trait_return,
 791         impl_trait_projections,
 792         implied_by,
 793         import,
 794         import_name_type,
 795         import_shadowing,
 796         imported_main,
 797         in_band_lifetimes,
 798         include,
 799         include_bytes,
 800         include_bytes_macro,
 801         include_str,
 802         include_str_macro,
 803         inclusive_range_syntax,
 804         index,
 805         index_mut,
 806         infer_outlives_requirements,
 807         infer_static_outlives_requirements,
 808         inherent_associated_types,
 809         inherit,
 810         inlateout,
 811         inline,
 812         inline_const,
 813         inline_const_pat,
 814         inout,
 815         instruction_set,
 816         integer_: "integer",
 817         integral,
 818         into_future,
 819         into_iter,
 820         intra_doc_pointers,
 821         intrinsics,
 822         irrefutable_let_patterns,
 823         isa_attribute,
 824         isize,
 825         issue,
 826         issue_5723_bootstrap,
 827         issue_tracker_base_url,
 828         item,
 829         item_like_imports,
 830         iter,
 831         iter_repeat,
 832         iterator_collect_fn,
 833         kcfi,
 834         keyword,
 835         kind,
 836         kreg,
 837         kreg0,
 838         label,
 839         label_break_value,
 840         lang,
 841         lang_items,
 842         large_assignments,
 843         lateout,
 844         lazy_normalization_consts,
 845         le,
 846         len,
 847         let_chains,
 848         let_else,
 849         lhs,
 850         lib,
 851         libc,
 852         lifetime,
 853         lifetimes,
 854         likely,
 855         line,
 856         link,
 857         link_args,
 858         link_cfg,
 859         link_llvm_intrinsics,
 860         link_name,
 861         link_ordinal,
 862         link_section,
 863         linkage,
 864         linker,
 865         lint_reasons,
 866         literal,
 867         load,
 868         loaded_from_disk,
 869         local,
 870         local_inner_macros,
 871         log10f32,
 872         log10f64,
 873         log2f32,
 874         log2f64,
 875         log_syntax,
 876         logf32,
 877         logf64,
 878         loop_break_value,
 879         lt,
 880         macro_at_most_once_rep,
 881         macro_attributes_in_derive_output,
 882         macro_escape,
 883         macro_export,
 884         macro_lifetime_matcher,
 885         macro_literal_matcher,
 886         macro_metavar_expr,
 887         macro_reexport,
 888         macro_use,
 889         macro_vis_matcher,
 890         macros_in_extern,
 891         main,
 892         managed_boxes,
 893         manually_drop,
 894         map,
 895         marker,
 896         marker_trait_attr,
 897         masked,
 898         match_beginning_vert,
 899         match_default_bindings,
 900         matches_macro,
 901         maxnumf32,
 902         maxnumf64,
 903         may_dangle,
 904         may_unwind,
 905         maybe_uninit,
 906         maybe_uninit_uninit,
 907         maybe_uninit_zeroed,
 908         mem_discriminant,
 909         mem_drop,
 910         mem_forget,
 911         mem_replace,
 912         mem_size_of,
 913         mem_size_of_val,
 914         mem_uninitialized,
 915         mem_variant_count,
 916         mem_zeroed,
 917         member_constraints,
 918         memory,
 919         memtag,
 920         message,
 921         meta,
 922         metadata_type,
 923         min_align_of,
 924         min_align_of_val,
 925         min_const_fn,
 926         min_const_generics,
 927         min_const_unsafe_fn,
 928         min_specialization,
 929         min_type_alias_impl_trait,
 930         minnumf32,
 931         minnumf64,
 932         mips_target_feature,
 933         miri,
 934         misc,
 935         mmx_reg,
 936         modifiers,
 937         module,
 938         module_path,
 939         more_qualified_paths,
 940         more_struct_aliases,
 941         movbe_target_feature,
 942         move_ref_pattern,
 943         move_size_limit,
 944         mul,
 945         mul_assign,
 946         mul_with_overflow,
 947         multiple_supertrait_upcastable,
 948         must_not_suspend,
 949         must_use,
 950         naked,
 951         naked_functions,
 952         name,
 953         names,
 954         native_link_modifiers,
 955         native_link_modifiers_as_needed,
 956         native_link_modifiers_bundle,
 957         native_link_modifiers_verbatim,
 958         native_link_modifiers_whole_archive,
 959         natvis_file,
 960         ne,
 961         nearbyintf32,
 962         nearbyintf64,
 963         needs_allocator,
 964         needs_drop,
 965         needs_panic_runtime,
 966         neg,
 967         negate_unsigned,
 968         negative_impls,
 969         neon,
 970         never,
 971         never_type,
 972         never_type_fallback,
 973         new,
 974         new_binary,
 975         new_debug,
 976         new_display,
 977         new_lower_exp,
 978         new_lower_hex,
 979         new_octal,
 980         new_pointer,
 981         new_unchecked,
 982         new_upper_exp,
 983         new_upper_hex,
 984         new_v1,
 985         new_v1_formatted,
 986         next,
 987         nll,
 988         no,
 989         no_builtins,
 990         no_core,
 991         no_coverage,
 992         no_crate_inject,
 993         no_debug,
 994         no_default_passes,
 995         no_implicit_prelude,
 996         no_inline,
 997         no_link,
 998         no_main,
 999         no_mangle,
1000         no_sanitize,
1001         no_stack_check,
1002         no_start,
1003         no_std,
1004         nomem,
1005         non_ascii_idents,
1006         non_exhaustive,
1007         non_exhaustive_omitted_patterns_lint,
1008         non_modrs_mods,
1009         nontemporal_store,
1010         noop_method_borrow,
1011         noop_method_clone,
1012         noop_method_deref,
1013         noreturn,
1014         nostack,
1015         not,
1016         notable_trait,
1017         note,
1018         object_safe_for_dispatch,
1019         of,
1020         offset,
1021         omit_gdb_pretty_printer_section,
1022         on,
1023         on_unimplemented,
1024         oom,
1025         opaque,
1026         ops,
1027         opt_out_copy,
1028         optimize,
1029         optimize_attribute,
1030         optin_builtin_traits,
1031         option,
1032         option_env,
1033         options,
1034         or,
1035         or_patterns,
1036         other,
1037         out,
1038         overlapping_marker_traits,
1039         owned_box,
1040         packed,
1041         panic,
1042         panic_2015,
1043         panic_2021,
1044         panic_abort,
1045         panic_bounds_check,
1046         panic_cannot_unwind,
1047         panic_display,
1048         panic_fmt,
1049         panic_handler,
1050         panic_impl,
1051         panic_implementation,
1052         panic_info,
1053         panic_location,
1054         panic_nounwind,
1055         panic_runtime,
1056         panic_str,
1057         panic_unwind,
1058         panicking,
1059         param_attrs,
1060         parent_label,
1061         partial_cmp,
1062         partial_ord,
1063         passes,
1064         pat,
1065         pat_param,
1066         path,
1067         pattern_parentheses,
1068         phantom_data,
1069         pin,
1070         platform_intrinsics,
1071         plugin,
1072         plugin_registrar,
1073         plugins,
1074         pointee_trait,
1075         pointer,
1076         pointer_sized,
1077         poll,
1078         position,
1079         post_dash_lto: "post-lto",
1080         powerpc_target_feature,
1081         powf32,
1082         powf64,
1083         powif32,
1084         powif64,
1085         pre_dash_lto: "pre-lto",
1086         precise_pointer_size_matching,
1087         precision,
1088         pref_align_of,
1089         prefetch_read_data,
1090         prefetch_read_instruction,
1091         prefetch_write_data,
1092         prefetch_write_instruction,
1093         preg,
1094         prelude,
1095         prelude_import,
1096         preserves_flags,
1097         primitive,
1098         print_macro,
1099         println_macro,
1100         proc_dash_macro: "proc-macro",
1101         proc_macro,
1102         proc_macro_attribute,
1103         proc_macro_derive,
1104         proc_macro_expr,
1105         proc_macro_gen,
1106         proc_macro_hygiene,
1107         proc_macro_internals,
1108         proc_macro_mod,
1109         proc_macro_non_items,
1110         proc_macro_path_invoc,
1111         profiler_builtins,
1112         profiler_runtime,
1113         ptr,
1114         ptr_guaranteed_cmp,
1115         ptr_mask,
1116         ptr_null,
1117         ptr_null_mut,
1118         ptr_offset_from,
1119         ptr_offset_from_unsigned,
1120         pub_macro_rules,
1121         pub_restricted,
1122         public,
1123         pure,
1124         pushpop_unsafe,
1125         qreg,
1126         qreg_low4,
1127         qreg_low8,
1128         quad_precision_float,
1129         question_mark,
1130         quote,
1131         range_inclusive_new,
1132         raw_dylib,
1133         raw_eq,
1134         raw_identifiers,
1135         raw_ref_op,
1136         re_rebalance_coherence,
1137         read_enum,
1138         read_enum_variant,
1139         read_enum_variant_arg,
1140         read_struct,
1141         read_struct_field,
1142         readonly,
1143         realloc,
1144         reason,
1145         receiver,
1146         recursion_limit,
1147         reexport_test_harness_main,
1148         ref_unwind_safe_trait,
1149         reference,
1150         reflect,
1151         reg,
1152         reg16,
1153         reg32,
1154         reg64,
1155         reg_abcd,
1156         reg_byte,
1157         reg_iw,
1158         reg_nonzero,
1159         reg_pair,
1160         reg_ptr,
1161         reg_upper,
1162         register_attr,
1163         register_tool,
1164         relaxed_adts,
1165         relaxed_struct_unsize,
1166         rem,
1167         rem_assign,
1168         repr,
1169         repr128,
1170         repr_align,
1171         repr_align_enum,
1172         repr_packed,
1173         repr_simd,
1174         repr_transparent,
1175         require,
1176         residual,
1177         result,
1178         return_position_impl_trait_in_trait,
1179         rhs,
1180         rintf32,
1181         rintf64,
1182         riscv_target_feature,
1183         rlib,
1184         rotate_left,
1185         rotate_right,
1186         roundf32,
1187         roundf64,
1188         rt,
1189         rtm_target_feature,
1190         rust,
1191         rust_2015,
1192         rust_2015_preview,
1193         rust_2018,
1194         rust_2018_preview,
1195         rust_2021,
1196         rust_2021_preview,
1197         rust_2024,
1198         rust_2024_preview,
1199         rust_begin_unwind,
1200         rust_cold_cc,
1201         rust_eh_catch_typeinfo,
1202         rust_eh_personality,
1203         rustc,
1204         rustc_allocator,
1205         rustc_allocator_zeroed,
1206         rustc_allow_const_fn_unstable,
1207         rustc_allow_incoherent_impl,
1208         rustc_allowed_through_unstable_modules,
1209         rustc_attrs,
1210         rustc_box,
1211         rustc_builtin_macro,
1212         rustc_capture_analysis,
1213         rustc_clean,
1214         rustc_coherence_is_core,
1215         rustc_const_stable,
1216         rustc_const_unstable,
1217         rustc_conversion_suggestion,
1218         rustc_deallocator,
1219         rustc_def_path,
1220         rustc_default_body_unstable,
1221         rustc_deny_explicit_impl,
1222         rustc_diagnostic_item,
1223         rustc_diagnostic_macros,
1224         rustc_dirty,
1225         rustc_do_not_const_check,
1226         rustc_dummy,
1227         rustc_dump_env_program_clauses,
1228         rustc_dump_program_clauses,
1229         rustc_dump_user_substs,
1230         rustc_dump_vtable,
1231         rustc_effective_visibility,
1232         rustc_error,
1233         rustc_evaluate_where_clauses,
1234         rustc_expected_cgu_reuse,
1235         rustc_has_incoherent_inherent_impls,
1236         rustc_if_this_changed,
1237         rustc_inherit_overflow_checks,
1238         rustc_insignificant_dtor,
1239         rustc_layout,
1240         rustc_layout_scalar_valid_range_end,
1241         rustc_layout_scalar_valid_range_start,
1242         rustc_legacy_const_generics,
1243         rustc_lint_diagnostics,
1244         rustc_lint_opt_deny_field_access,
1245         rustc_lint_opt_ty,
1246         rustc_lint_query_instability,
1247         rustc_macro_transparency,
1248         rustc_main,
1249         rustc_mir,
1250         rustc_must_implement_one_of,
1251         rustc_nonnull_optimization_guaranteed,
1252         rustc_nounwind,
1253         rustc_object_lifetime_default,
1254         rustc_on_unimplemented,
1255         rustc_outlives,
1256         rustc_paren_sugar,
1257         rustc_partition_codegened,
1258         rustc_partition_reused,
1259         rustc_pass_by_value,
1260         rustc_peek,
1261         rustc_peek_definite_init,
1262         rustc_peek_liveness,
1263         rustc_peek_maybe_init,
1264         rustc_peek_maybe_uninit,
1265         rustc_polymorphize_error,
1266         rustc_private,
1267         rustc_proc_macro_decls,
1268         rustc_promotable,
1269         rustc_reallocator,
1270         rustc_regions,
1271         rustc_reservation_impl,
1272         rustc_safe_intrinsic,
1273         rustc_serialize,
1274         rustc_skip_array_during_method_dispatch,
1275         rustc_specialization_trait,
1276         rustc_std_internal_symbol,
1277         rustc_strict_coherence,
1278         rustc_symbol_name,
1279         rustc_test_marker,
1280         rustc_then_this_would_need,
1281         rustc_trivial_field_reads,
1282         rustc_unsafe_specialization_marker,
1283         rustc_variance,
1284         rustdoc,
1285         rustdoc_internals,
1286         rustdoc_missing_doc_code_examples,
1287         rustfmt,
1288         rvalue_static_promotion,
1289         s,
1290         safety,
1291         sanitize,
1292         sanitizer_runtime,
1293         saturating_add,
1294         saturating_sub,
1295         self_in_typedefs,
1296         self_struct_ctor,
1297         semitransparent,
1298         shadow_call_stack,
1299         shl,
1300         shl_assign,
1301         should_panic,
1302         shr,
1303         shr_assign,
1304         sig_dfl,
1305         sig_ign,
1306         simd,
1307         simd_add,
1308         simd_and,
1309         simd_arith_offset,
1310         simd_as,
1311         simd_bitmask,
1312         simd_cast,
1313         simd_cast_ptr,
1314         simd_ceil,
1315         simd_div,
1316         simd_eq,
1317         simd_expose_addr,
1318         simd_extract,
1319         simd_fabs,
1320         simd_fcos,
1321         simd_fexp,
1322         simd_fexp2,
1323         simd_ffi,
1324         simd_flog,
1325         simd_flog10,
1326         simd_flog2,
1327         simd_floor,
1328         simd_fma,
1329         simd_fmax,
1330         simd_fmin,
1331         simd_fpow,
1332         simd_fpowi,
1333         simd_from_exposed_addr,
1334         simd_fsin,
1335         simd_fsqrt,
1336         simd_gather,
1337         simd_ge,
1338         simd_gt,
1339         simd_insert,
1340         simd_le,
1341         simd_lt,
1342         simd_mul,
1343         simd_ne,
1344         simd_neg,
1345         simd_or,
1346         simd_reduce_add_ordered,
1347         simd_reduce_add_unordered,
1348         simd_reduce_all,
1349         simd_reduce_and,
1350         simd_reduce_any,
1351         simd_reduce_max,
1352         simd_reduce_max_nanless,
1353         simd_reduce_min,
1354         simd_reduce_min_nanless,
1355         simd_reduce_mul_ordered,
1356         simd_reduce_mul_unordered,
1357         simd_reduce_or,
1358         simd_reduce_xor,
1359         simd_rem,
1360         simd_round,
1361         simd_saturating_add,
1362         simd_saturating_sub,
1363         simd_scatter,
1364         simd_select,
1365         simd_select_bitmask,
1366         simd_shl,
1367         simd_shr,
1368         simd_shuffle,
1369         simd_sub,
1370         simd_trunc,
1371         simd_xor,
1372         since,
1373         sinf32,
1374         sinf64,
1375         size,
1376         size_of,
1377         size_of_val,
1378         sized,
1379         skip,
1380         slice,
1381         slice_len_fn,
1382         slice_patterns,
1383         slicing_syntax,
1384         soft,
1385         specialization,
1386         speed,
1387         spotlight,
1388         sqrtf32,
1389         sqrtf64,
1390         sreg,
1391         sreg_low16,
1392         sse,
1393         sse4a_target_feature,
1394         stable,
1395         staged_api,
1396         start,
1397         state,
1398         static_in_const,
1399         static_nobundle,
1400         static_recursion,
1401         staticlib,
1402         std,
1403         std_panic,
1404         std_panic_2015_macro,
1405         std_panic_macro,
1406         stmt,
1407         stmt_expr_attributes,
1408         stop_after_dataflow,
1409         store,
1410         str,
1411         str_split_whitespace,
1412         str_trim,
1413         str_trim_end,
1414         str_trim_start,
1415         strict_provenance,
1416         string_deref_patterns,
1417         stringify,
1418         struct_field_attributes,
1419         struct_inherit,
1420         struct_variant,
1421         structural_match,
1422         structural_peq,
1423         structural_teq,
1424         sty,
1425         sub,
1426         sub_assign,
1427         sub_with_overflow,
1428         suggestion,
1429         sym,
1430         sync,
1431         t32,
1432         target,
1433         target_abi,
1434         target_arch,
1435         target_endian,
1436         target_env,
1437         target_family,
1438         target_feature,
1439         target_feature_11,
1440         target_has_atomic,
1441         target_has_atomic_equal_alignment,
1442         target_has_atomic_load_store,
1443         target_os,
1444         target_pointer_width,
1445         target_thread_local,
1446         target_vendor,
1447         tbm_target_feature,
1448         termination,
1449         termination_trait,
1450         termination_trait_test,
1451         test,
1452         test_2018_feature,
1453         test_accepted_feature,
1454         test_case,
1455         test_removed_feature,
1456         test_runner,
1457         test_unstable_lint,
1458         thread,
1459         thread_local,
1460         thread_local_macro,
1461         thumb2,
1462         thumb_mode: "thumb-mode",
1463         tmm_reg,
1464         to_string,
1465         to_vec,
1466         todo_macro,
1467         tool_attributes,
1468         tool_lints,
1469         trace_macros,
1470         track_caller,
1471         trait_alias,
1472         trait_upcasting,
1473         transmute,
1474         transmute_opts,
1475         transmute_trait,
1476         transparent,
1477         transparent_enums,
1478         transparent_unions,
1479         trivial_bounds,
1480         truncf32,
1481         truncf64,
1482         try_blocks,
1483         try_capture,
1484         try_from,
1485         try_into,
1486         try_trait_v2,
1487         tt,
1488         tuple,
1489         tuple_indexing,
1490         tuple_trait,
1491         two_phase,
1492         ty,
1493         type_alias_enum_variants,
1494         type_alias_impl_trait,
1495         type_ascribe,
1496         type_ascription,
1497         type_changing_struct_update,
1498         type_id,
1499         type_length_limit,
1500         type_macros,
1501         type_name,
1502         u128,
1503         u16,
1504         u32,
1505         u64,
1506         u8,
1507         unaligned_volatile_load,
1508         unaligned_volatile_store,
1509         unboxed_closures,
1510         unchecked_add,
1511         unchecked_div,
1512         unchecked_mul,
1513         unchecked_rem,
1514         unchecked_shl,
1515         unchecked_shr,
1516         unchecked_sub,
1517         underscore_const_names,
1518         underscore_imports,
1519         underscore_lifetimes,
1520         uniform_paths,
1521         unimplemented_macro,
1522         unit,
1523         universal_impl_trait,
1524         unix,
1525         unix_sigpipe,
1526         unlikely,
1527         unmarked_api,
1528         unpin,
1529         unreachable,
1530         unreachable_2015,
1531         unreachable_2015_macro,
1532         unreachable_2021,
1533         unreachable_code,
1534         unreachable_display,
1535         unreachable_macro,
1536         unrestricted_attribute_tokens,
1537         unsafe_block_in_unsafe_fn,
1538         unsafe_cell,
1539         unsafe_no_drop_flag,
1540         unsafe_pin_internals,
1541         unsize,
1542         unsized_fn_params,
1543         unsized_locals,
1544         unsized_tuple_coercion,
1545         unstable,
1546         unstable_location_reason_default: "this crate is being loaded from the sysroot, an \
1547                           unstable location; did you mean to load this crate \
1548                           from crates.io via `Cargo.toml` instead?",
1549         untagged_unions,
1550         unused_imports,
1551         unwind,
1552         unwind_attributes,
1553         unwind_safe_trait,
1554         unwrap,
1555         unwrap_or,
1556         use_extern_macros,
1557         use_nested_groups,
1558         used,
1559         used_with_arg,
1560         using,
1561         usize,
1562         v1,
1563         va_arg,
1564         va_copy,
1565         va_end,
1566         va_list,
1567         va_start,
1568         val,
1569         validity,
1570         values,
1571         var,
1572         variant_count,
1573         vec,
1574         vec_macro,
1575         version,
1576         vfp2,
1577         vis,
1578         visible_private_types,
1579         volatile,
1580         volatile_copy_memory,
1581         volatile_copy_nonoverlapping_memory,
1582         volatile_load,
1583         volatile_set_memory,
1584         volatile_store,
1585         vreg,
1586         vreg_low16,
1587         vtable_align,
1588         vtable_size,
1589         warn,
1590         wasm_abi,
1591         wasm_import_module,
1592         wasm_target_feature,
1593         while_let,
1594         width,
1595         windows,
1596         windows_subsystem,
1597         with_negative_coherence,
1598         wrapping_add,
1599         wrapping_mul,
1600         wrapping_sub,
1601         wreg,
1602         write_bytes,
1603         write_macro,
1604         write_str,
1605         writeln_macro,
1606         x87_reg,
1607         xer,
1608         xmm_reg,
1609         yeet_desugar_details,
1610         yeet_expr,
1611         ymm_reg,
1612         zmm_reg,
1613     }
1614 }
1615
1616 #[derive(Copy, Clone, Eq, HashStable_Generic, Encodable, Decodable)]
1617 pub struct Ident {
1618     pub name: Symbol,
1619     pub span: Span,
1620 }
1621
1622 impl Ident {
1623     #[inline]
1624     /// Constructs a new identifier from a symbol and a span.
1625     pub const fn new(name: Symbol, span: Span) -> Ident {
1626         Ident { name, span }
1627     }
1628
1629     /// Constructs a new identifier with a dummy span.
1630     #[inline]
1631     pub const fn with_dummy_span(name: Symbol) -> Ident {
1632         Ident::new(name, DUMMY_SP)
1633     }
1634
1635     #[inline]
1636     pub fn empty() -> Ident {
1637         Ident::with_dummy_span(kw::Empty)
1638     }
1639
1640     /// Maps a string to an identifier with a dummy span.
1641     pub fn from_str(string: &str) -> Ident {
1642         Ident::with_dummy_span(Symbol::intern(string))
1643     }
1644
1645     /// Maps a string and a span to an identifier.
1646     pub fn from_str_and_span(string: &str, span: Span) -> Ident {
1647         Ident::new(Symbol::intern(string), span)
1648     }
1649
1650     /// Replaces `lo` and `hi` with those from `span`, but keep hygiene context.
1651     pub fn with_span_pos(self, span: Span) -> Ident {
1652         Ident::new(self.name, span.with_ctxt(self.span.ctxt()))
1653     }
1654
1655     pub fn without_first_quote(self) -> Ident {
1656         Ident::new(Symbol::intern(self.as_str().trim_start_matches('\'')), self.span)
1657     }
1658
1659     /// "Normalize" ident for use in comparisons using "item hygiene".
1660     /// Identifiers with same string value become same if they came from the same macro 2.0 macro
1661     /// (e.g., `macro` item, but not `macro_rules` item) and stay different if they came from
1662     /// different macro 2.0 macros.
1663     /// Technically, this operation strips all non-opaque marks from ident's syntactic context.
1664     pub fn normalize_to_macros_2_0(self) -> Ident {
1665         Ident::new(self.name, self.span.normalize_to_macros_2_0())
1666     }
1667
1668     /// "Normalize" ident for use in comparisons using "local variable hygiene".
1669     /// Identifiers with same string value become same if they came from the same non-transparent
1670     /// macro (e.g., `macro` or `macro_rules!` items) and stay different if they came from different
1671     /// non-transparent macros.
1672     /// Technically, this operation strips all transparent marks from ident's syntactic context.
1673     #[inline]
1674     pub fn normalize_to_macro_rules(self) -> Ident {
1675         Ident::new(self.name, self.span.normalize_to_macro_rules())
1676     }
1677
1678     /// Access the underlying string. This is a slowish operation because it
1679     /// requires locking the symbol interner.
1680     ///
1681     /// Note that the lifetime of the return value is a lie. See
1682     /// `Symbol::as_str()` for details.
1683     pub fn as_str(&self) -> &str {
1684         self.name.as_str()
1685     }
1686 }
1687
1688 impl PartialEq for Ident {
1689     #[inline]
1690     fn eq(&self, rhs: &Self) -> bool {
1691         self.name == rhs.name && self.span.eq_ctxt(rhs.span)
1692     }
1693 }
1694
1695 impl Hash for Ident {
1696     fn hash<H: Hasher>(&self, state: &mut H) {
1697         self.name.hash(state);
1698         self.span.ctxt().hash(state);
1699     }
1700 }
1701
1702 impl fmt::Debug for Ident {
1703     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1704         fmt::Display::fmt(self, f)?;
1705         fmt::Debug::fmt(&self.span.ctxt(), f)
1706     }
1707 }
1708
1709 /// This implementation is supposed to be used in error messages, so it's expected to be identical
1710 /// to printing the original identifier token written in source code (`token_to_string`),
1711 /// except that AST identifiers don't keep the rawness flag, so we have to guess it.
1712 impl fmt::Display for Ident {
1713     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1714         fmt::Display::fmt(&IdentPrinter::new(self.name, self.is_raw_guess(), None), f)
1715     }
1716 }
1717
1718 /// The most general type to print identifiers.
1719 ///
1720 /// AST pretty-printer is used as a fallback for turning AST structures into token streams for
1721 /// proc macros. Additionally, proc macros may stringify their input and expect it survive the
1722 /// stringification (especially true for proc macro derives written between Rust 1.15 and 1.30).
1723 /// So we need to somehow pretty-print `$crate` in a way preserving at least some of its
1724 /// hygiene data, most importantly name of the crate it refers to.
1725 /// As a result we print `$crate` as `crate` if it refers to the local crate
1726 /// and as `::other_crate_name` if it refers to some other crate.
1727 /// Note, that this is only done if the ident token is printed from inside of AST pretty-printing,
1728 /// but not otherwise. Pretty-printing is the only way for proc macros to discover token contents,
1729 /// so we should not perform this lossy conversion if the top level call to the pretty-printer was
1730 /// done for a token stream or a single token.
1731 pub struct IdentPrinter {
1732     symbol: Symbol,
1733     is_raw: bool,
1734     /// Span used for retrieving the crate name to which `$crate` refers to,
1735     /// if this field is `None` then the `$crate` conversion doesn't happen.
1736     convert_dollar_crate: Option<Span>,
1737 }
1738
1739 impl IdentPrinter {
1740     /// The most general `IdentPrinter` constructor. Do not use this.
1741     pub fn new(symbol: Symbol, is_raw: bool, convert_dollar_crate: Option<Span>) -> IdentPrinter {
1742         IdentPrinter { symbol, is_raw, convert_dollar_crate }
1743     }
1744
1745     /// This implementation is supposed to be used when printing identifiers
1746     /// as a part of pretty-printing for larger AST pieces.
1747     /// Do not use this either.
1748     pub fn for_ast_ident(ident: Ident, is_raw: bool) -> IdentPrinter {
1749         IdentPrinter::new(ident.name, is_raw, Some(ident.span))
1750     }
1751 }
1752
1753 impl fmt::Display for IdentPrinter {
1754     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1755         if self.is_raw {
1756             f.write_str("r#")?;
1757         } else if self.symbol == kw::DollarCrate {
1758             if let Some(span) = self.convert_dollar_crate {
1759                 let converted = span.ctxt().dollar_crate_name();
1760                 if !converted.is_path_segment_keyword() {
1761                     f.write_str("::")?;
1762                 }
1763                 return fmt::Display::fmt(&converted, f);
1764             }
1765         }
1766         fmt::Display::fmt(&self.symbol, f)
1767     }
1768 }
1769
1770 /// An newtype around `Ident` that calls [Ident::normalize_to_macro_rules] on
1771 /// construction.
1772 // FIXME(matthewj, petrochenkov) Use this more often, add a similar
1773 // `ModernIdent` struct and use that as well.
1774 #[derive(Copy, Clone, Eq, PartialEq, Hash)]
1775 pub struct MacroRulesNormalizedIdent(Ident);
1776
1777 impl MacroRulesNormalizedIdent {
1778     pub fn new(ident: Ident) -> Self {
1779         Self(ident.normalize_to_macro_rules())
1780     }
1781 }
1782
1783 impl fmt::Debug for MacroRulesNormalizedIdent {
1784     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1785         fmt::Debug::fmt(&self.0, f)
1786     }
1787 }
1788
1789 impl fmt::Display for MacroRulesNormalizedIdent {
1790     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1791         fmt::Display::fmt(&self.0, f)
1792     }
1793 }
1794
1795 /// An interned string.
1796 ///
1797 /// Internally, a `Symbol` is implemented as an index, and all operations
1798 /// (including hashing, equality, and ordering) operate on that index. The use
1799 /// of `rustc_index::newtype_index!` means that `Option<Symbol>` only takes up 4 bytes,
1800 /// because `rustc_index::newtype_index!` reserves the last 256 values for tagging purposes.
1801 ///
1802 /// Note that `Symbol` cannot directly be a `rustc_index::newtype_index!` because it
1803 /// implements `fmt::Debug`, `Encodable`, and `Decodable` in special ways.
1804 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
1805 pub struct Symbol(SymbolIndex);
1806
1807 rustc_index::newtype_index! {
1808     struct SymbolIndex {}
1809 }
1810
1811 impl Symbol {
1812     const fn new(n: u32) -> Self {
1813         Symbol(SymbolIndex::from_u32(n))
1814     }
1815
1816     /// for use in Decoder only
1817     pub fn new_from_decoded(n: u32) -> Self {
1818         Self::new(n)
1819     }
1820
1821     /// Maps a string to its interned representation.
1822     pub fn intern(string: &str) -> Self {
1823         with_session_globals(|session_globals| session_globals.symbol_interner.intern(string))
1824     }
1825
1826     /// Access the underlying string. This is a slowish operation because it
1827     /// requires locking the symbol interner.
1828     ///
1829     /// Note that the lifetime of the return value is a lie. It's not the same
1830     /// as `&self`, but actually tied to the lifetime of the underlying
1831     /// interner. Interners are long-lived, and there are very few of them, and
1832     /// this function is typically used for short-lived things, so in practice
1833     /// it works out ok.
1834     pub fn as_str(&self) -> &str {
1835         with_session_globals(|session_globals| unsafe {
1836             std::mem::transmute::<&str, &str>(session_globals.symbol_interner.get(*self))
1837         })
1838     }
1839
1840     pub fn as_u32(self) -> u32 {
1841         self.0.as_u32()
1842     }
1843
1844     pub fn is_empty(self) -> bool {
1845         self == kw::Empty
1846     }
1847
1848     /// This method is supposed to be used in error messages, so it's expected to be
1849     /// identical to printing the original identifier token written in source code
1850     /// (`token_to_string`, `Ident::to_string`), except that symbols don't keep the rawness flag
1851     /// or edition, so we have to guess the rawness using the global edition.
1852     pub fn to_ident_string(self) -> String {
1853         Ident::with_dummy_span(self).to_string()
1854     }
1855 }
1856
1857 impl fmt::Debug for Symbol {
1858     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1859         fmt::Debug::fmt(self.as_str(), f)
1860     }
1861 }
1862
1863 impl fmt::Display for Symbol {
1864     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1865         fmt::Display::fmt(self.as_str(), f)
1866     }
1867 }
1868
1869 // takes advantage of `str::to_string` specialization
1870 impl ToString for Symbol {
1871     fn to_string(&self) -> String {
1872         self.as_str().to_string()
1873     }
1874 }
1875
1876 impl<S: Encoder> Encodable<S> for Symbol {
1877     default fn encode(&self, s: &mut S) {
1878         s.emit_str(self.as_str());
1879     }
1880 }
1881
1882 impl<D: Decoder> Decodable<D> for Symbol {
1883     #[inline]
1884     default fn decode(d: &mut D) -> Symbol {
1885         Symbol::intern(d.read_str())
1886     }
1887 }
1888
1889 impl<CTX> HashStable<CTX> for Symbol {
1890     #[inline]
1891     fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
1892         self.as_str().hash_stable(hcx, hasher);
1893     }
1894 }
1895
1896 impl<CTX> ToStableHashKey<CTX> for Symbol {
1897     type KeyType = String;
1898     #[inline]
1899     fn to_stable_hash_key(&self, _: &CTX) -> String {
1900         self.as_str().to_string()
1901     }
1902 }
1903
1904 #[derive(Default)]
1905 pub(crate) struct Interner(Lock<InternerInner>);
1906
1907 // The `&'static str`s in this type actually point into the arena.
1908 //
1909 // The `FxHashMap`+`Vec` pair could be replaced by `FxIndexSet`, but #75278
1910 // found that to regress performance up to 2% in some cases. This might be
1911 // revisited after further improvements to `indexmap`.
1912 //
1913 // This type is private to prevent accidentally constructing more than one
1914 // `Interner` on the same thread, which makes it easy to mix up `Symbol`s
1915 // between `Interner`s.
1916 #[derive(Default)]
1917 struct InternerInner {
1918     arena: DroplessArena,
1919     names: FxHashMap<&'static str, Symbol>,
1920     strings: Vec<&'static str>,
1921 }
1922
1923 impl Interner {
1924     fn prefill(init: &[&'static str]) -> Self {
1925         Interner(Lock::new(InternerInner {
1926             strings: init.into(),
1927             names: init.iter().copied().zip((0..).map(Symbol::new)).collect(),
1928             ..Default::default()
1929         }))
1930     }
1931
1932     #[inline]
1933     fn intern(&self, string: &str) -> Symbol {
1934         let mut inner = self.0.lock();
1935         if let Some(&name) = inner.names.get(string) {
1936             return name;
1937         }
1938
1939         let name = Symbol::new(inner.strings.len() as u32);
1940
1941         // SAFETY: we convert from `&str` to `&[u8]`, clone it into the arena,
1942         // and immediately convert the clone back to `&[u8], all because there
1943         // is no `inner.arena.alloc_str()` method. This is clearly safe.
1944         let string: &str =
1945             unsafe { str::from_utf8_unchecked(inner.arena.alloc_slice(string.as_bytes())) };
1946
1947         // SAFETY: we can extend the arena allocation to `'static` because we
1948         // only access these while the arena is still alive.
1949         let string: &'static str = unsafe { &*(string as *const str) };
1950         inner.strings.push(string);
1951
1952         // This second hash table lookup can be avoided by using `RawEntryMut`,
1953         // but this code path isn't hot enough for it to be worth it. See
1954         // #91445 for details.
1955         inner.names.insert(string, name);
1956         name
1957     }
1958
1959     // Get the symbol as a string. `Symbol::as_str()` should be used in
1960     // preference to this function.
1961     fn get(&self, symbol: Symbol) -> &str {
1962         self.0.lock().strings[symbol.0.as_usize()]
1963     }
1964 }
1965
1966 // This module has a very short name because it's used a lot.
1967 /// This module contains all the defined keyword `Symbol`s.
1968 ///
1969 /// Given that `kw` is imported, use them like `kw::keyword_name`.
1970 /// For example `kw::Loop` or `kw::Break`.
1971 pub mod kw {
1972     pub use super::kw_generated::*;
1973 }
1974
1975 // This module has a very short name because it's used a lot.
1976 /// This module contains all the defined non-keyword `Symbol`s.
1977 ///
1978 /// Given that `sym` is imported, use them like `sym::symbol_name`.
1979 /// For example `sym::rustfmt` or `sym::u8`.
1980 pub mod sym {
1981     use super::Symbol;
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 }