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         Layout,
 217         Left,
 218         LinkedList,
 219         LintPass,
 220         LocalKey,
 221         Mutex,
 222         MutexGuard,
 223         N,
 224         NonZeroI128,
 225         NonZeroI16,
 226         NonZeroI32,
 227         NonZeroI64,
 228         NonZeroI8,
 229         NonZeroU128,
 230         NonZeroU16,
 231         NonZeroU32,
 232         NonZeroU64,
 233         NonZeroU8,
 234         None,
 235         Ok,
 236         Option,
 237         Ord,
 238         Ordering,
 239         OsStr,
 240         OsString,
 241         Output,
 242         Param,
 243         PartialEq,
 244         PartialOrd,
 245         Path,
 246         PathBuf,
 247         Pending,
 248         Pin,
 249         Pointer,
 250         Poll,
 251         ProcMacro,
 252         ProceduralMasqueradeDummyType,
 253         Range,
 254         RangeFrom,
 255         RangeFull,
 256         RangeInclusive,
 257         RangeTo,
 258         RangeToInclusive,
 259         Rc,
 260         Ready,
 261         Receiver,
 262         RefCell,
 263         Relaxed,
 264         Release,
 265         Result,
 266         ResumeTy,
 267         Return,
 268         Right,
 269         Rust,
 270         RustcDecodable,
 271         RustcEncodable,
 272         RwLock,
 273         RwLockReadGuard,
 274         RwLockWriteGuard,
 275         Send,
 276         SeqCst,
 277         SliceIndex,
 278         Some,
 279         String,
 280         StructuralEq,
 281         StructuralPartialEq,
 282         SubdiagnosticMessage,
 283         Sync,
 284         T,
 285         Target,
 286         ToOwned,
 287         ToString,
 288         Try,
 289         TryCaptureGeneric,
 290         TryCapturePrintable,
 291         TryFrom,
 292         TryInto,
 293         Ty,
 294         TyCtxt,
 295         TyKind,
 296         Unknown,
 297         UnsafeArg,
 298         Vec,
 299         VecDeque,
 300         Wrapper,
 301         Yield,
 302         _DECLS,
 303         _Self,
 304         __D,
 305         __H,
 306         __S,
 307         __awaitee,
 308         __try_var,
 309         _d,
 310         _e,
 311         _task_context,
 312         a32,
 313         aarch64_target_feature,
 314         aarch64_ver_target_feature,
 315         abi,
 316         abi_amdgpu_kernel,
 317         abi_avr_interrupt,
 318         abi_c_cmse_nonsecure_call,
 319         abi_efiapi,
 320         abi_msp430_interrupt,
 321         abi_ptx,
 322         abi_sysv64,
 323         abi_thiscall,
 324         abi_unadjusted,
 325         abi_vectorcall,
 326         abi_x86_interrupt,
 327         abort,
 328         add,
 329         add_assign,
 330         add_with_overflow,
 331         address,
 332         adt_const_params,
 333         advanced_slice_patterns,
 334         adx_target_feature,
 335         alias,
 336         align,
 337         align_offset,
 338         alignment,
 339         all,
 340         alloc,
 341         alloc_error_handler,
 342         alloc_layout,
 343         alloc_zeroed,
 344         allocator,
 345         allocator_api,
 346         allocator_internals,
 347         allow,
 348         allow_fail,
 349         allow_internal_unsafe,
 350         allow_internal_unstable,
 351         allowed,
 352         alu32,
 353         always,
 354         and,
 355         and_then,
 356         anonymous_lifetime_in_impl_trait,
 357         any,
 358         append_const_msg,
 359         arbitrary_enum_discriminant,
 360         arbitrary_self_types,
 361         args,
 362         arith_offset,
 363         arm,
 364         arm_target_feature,
 365         array,
 366         arrays,
 367         as_ptr,
 368         as_ref,
 369         as_str,
 370         asm,
 371         asm_const,
 372         asm_experimental_arch,
 373         asm_sym,
 374         asm_unwind,
 375         assert,
 376         assert_eq_macro,
 377         assert_inhabited,
 378         assert_macro,
 379         assert_mem_uninitialized_valid,
 380         assert_ne_macro,
 381         assert_receiver_is_total_eq,
 382         assert_zero_valid,
 383         asserting,
 384         associated_const_equality,
 385         associated_consts,
 386         associated_type_bounds,
 387         associated_type_defaults,
 388         associated_types,
 389         assume,
 390         assume_init,
 391         async_await,
 392         async_closure,
 393         async_fn_in_trait,
 394         atomic,
 395         atomic_mod,
 396         atomics,
 397         att_syntax,
 398         attr,
 399         attr_literals,
 400         attributes,
 401         augmented_assignments,
 402         auto_traits,
 403         automatically_derived,
 404         avx,
 405         avx512_target_feature,
 406         avx512bw,
 407         avx512f,
 408         await_macro,
 409         bang,
 410         begin_panic,
 411         bench,
 412         bin,
 413         bind_by_move_pattern_guards,
 414         bindings_after_at,
 415         bitand,
 416         bitand_assign,
 417         bitor,
 418         bitor_assign,
 419         bitreverse,
 420         bitxor,
 421         bitxor_assign,
 422         black_box,
 423         block,
 424         bool,
 425         borrowck_graphviz_format,
 426         borrowck_graphviz_postflow,
 427         box_free,
 428         box_patterns,
 429         box_syntax,
 430         bpf_target_feature,
 431         braced_empty_structs,
 432         branch,
 433         breakpoint,
 434         bridge,
 435         bswap,
 436         c_str,
 437         c_unwind,
 438         c_variadic,
 439         call,
 440         call_mut,
 441         call_once,
 442         caller_location,
 443         capture_disjoint_fields,
 444         cause,
 445         cdylib,
 446         ceilf32,
 447         ceilf64,
 448         cfg,
 449         cfg_accessible,
 450         cfg_attr,
 451         cfg_attr_multi,
 452         cfg_doctest,
 453         cfg_eval,
 454         cfg_hide,
 455         cfg_panic,
 456         cfg_sanitize,
 457         cfg_target_abi,
 458         cfg_target_compact,
 459         cfg_target_feature,
 460         cfg_target_has_atomic,
 461         cfg_target_has_atomic_equal_alignment,
 462         cfg_target_thread_local,
 463         cfg_target_vendor,
 464         cfg_version,
 465         cfi,
 466         char,
 467         client,
 468         clippy,
 469         clobber_abi,
 470         clone,
 471         clone_closures,
 472         clone_from,
 473         closure,
 474         closure_lifetime_binder,
 475         closure_to_fn_coercion,
 476         closure_track_caller,
 477         cmp,
 478         cmp_max,
 479         cmp_min,
 480         cmpxchg16b_target_feature,
 481         cmse_nonsecure_entry,
 482         coerce_unsized,
 483         cold,
 484         collapse_debuginfo,
 485         column,
 486         compare_exchange,
 487         compare_exchange_weak,
 488         compile_error,
 489         compiler,
 490         compiler_builtins,
 491         compiler_fence,
 492         concat,
 493         concat_bytes,
 494         concat_idents,
 495         conservative_impl_trait,
 496         console,
 497         const_allocate,
 498         const_async_blocks,
 499         const_compare_raw_pointers,
 500         const_constructor,
 501         const_deallocate,
 502         const_eval_limit,
 503         const_eval_select,
 504         const_evaluatable_checked,
 505         const_extern_fn,
 506         const_fn,
 507         const_fn_floating_point_arithmetic,
 508         const_fn_fn_ptr_basics,
 509         const_fn_trait_bound,
 510         const_fn_transmute,
 511         const_fn_union,
 512         const_fn_unsize,
 513         const_for,
 514         const_format_args,
 515         const_generics,
 516         const_generics_defaults,
 517         const_if_match,
 518         const_impl_trait,
 519         const_in_array_repeat_expressions,
 520         const_indexing,
 521         const_let,
 522         const_loop,
 523         const_mut_refs,
 524         const_panic,
 525         const_panic_fmt,
 526         const_precise_live_drops,
 527         const_raw_ptr_deref,
 528         const_raw_ptr_to_usize_cast,
 529         const_refs_to_cell,
 530         const_trait,
 531         const_trait_bound_opt_out,
 532         const_trait_impl,
 533         const_try,
 534         constant,
 535         constructor,
 536         context,
 537         copy,
 538         copy_closures,
 539         copy_nonoverlapping,
 540         copysignf32,
 541         copysignf64,
 542         core,
 543         core_panic,
 544         core_panic_2015_macro,
 545         core_panic_2021_macro,
 546         core_panic_macro,
 547         cosf32,
 548         cosf64,
 549         count,
 550         cr,
 551         crate_id,
 552         crate_in_paths,
 553         crate_local,
 554         crate_name,
 555         crate_type,
 556         crate_visibility_modifier,
 557         crt_dash_static: "crt-static",
 558         cstring_type,
 559         ctlz,
 560         ctlz_nonzero,
 561         ctpop,
 562         cttz,
 563         cttz_nonzero,
 564         custom_attribute,
 565         custom_derive,
 566         custom_inner_attributes,
 567         custom_mir,
 568         custom_test_frameworks,
 569         d,
 570         d32,
 571         dbg_macro,
 572         dead_code,
 573         dealloc,
 574         debug,
 575         debug_assert_eq_macro,
 576         debug_assert_macro,
 577         debug_assert_ne_macro,
 578         debug_assertions,
 579         debug_struct,
 580         debug_struct_fields_finish,
 581         debug_tuple,
 582         debug_tuple_fields_finish,
 583         debugger_visualizer,
 584         decl_macro,
 585         declare_lint_pass,
 586         decode,
 587         default_alloc_error_handler,
 588         default_lib_allocator,
 589         default_method_body_is_const,
 590         default_type_parameter_fallback,
 591         default_type_params,
 592         delay_span_bug_from_inside_query,
 593         deny,
 594         deprecated,
 595         deprecated_safe,
 596         deprecated_suggestion,
 597         deref,
 598         deref_method,
 599         deref_mut,
 600         deref_target,
 601         derive,
 602         derive_const,
 603         derive_default_enum,
 604         destruct,
 605         destructuring_assignment,
 606         diagnostic,
 607         direct,
 608         discriminant_kind,
 609         discriminant_type,
 610         discriminant_value,
 611         dispatch_from_dyn,
 612         div,
 613         div_assign,
 614         doc,
 615         doc_alias,
 616         doc_auto_cfg,
 617         doc_cfg,
 618         doc_cfg_hide,
 619         doc_keyword,
 620         doc_masked,
 621         doc_notable_trait,
 622         doc_primitive,
 623         doc_spotlight,
 624         doctest,
 625         document_private_items,
 626         dotdot: "..",
 627         dotdot_in_tuple_patterns,
 628         dotdoteq_in_patterns,
 629         dreg,
 630         dreg_low16,
 631         dreg_low8,
 632         drop,
 633         drop_in_place,
 634         drop_types_in_const,
 635         dropck_eyepatch,
 636         dropck_parametricity,
 637         dylib,
 638         dyn_metadata,
 639         dyn_star,
 640         dyn_trait,
 641         e,
 642         edition_panic,
 643         eh_catch_typeinfo,
 644         eh_personality,
 645         emit_enum,
 646         emit_enum_variant,
 647         emit_enum_variant_arg,
 648         emit_struct,
 649         emit_struct_field,
 650         enable,
 651         encode,
 652         end,
 653         env,
 654         eprint_macro,
 655         eprintln_macro,
 656         eq,
 657         ermsb_target_feature,
 658         exact_div,
 659         except,
 660         exchange_malloc,
 661         exclusive_range_pattern,
 662         exhaustive_integer_patterns,
 663         exhaustive_patterns,
 664         existential_type,
 665         exp2f32,
 666         exp2f64,
 667         expect,
 668         expected,
 669         expf32,
 670         expf64,
 671         explicit_generic_args_with_impl_trait,
 672         export_name,
 673         expr,
 674         extended_key_value_attributes,
 675         extended_varargs_abi_support,
 676         extern_absolute_paths,
 677         extern_crate_item_prelude,
 678         extern_crate_self,
 679         extern_in_paths,
 680         extern_prelude,
 681         extern_types,
 682         external_doc,
 683         f,
 684         f16c_target_feature,
 685         f32,
 686         f64,
 687         fabsf32,
 688         fabsf64,
 689         fadd_fast,
 690         fake_variadic,
 691         fdiv_fast,
 692         feature,
 693         fence,
 694         ferris: "🦀",
 695         fetch_update,
 696         ffi,
 697         ffi_const,
 698         ffi_pure,
 699         ffi_returns_twice,
 700         field,
 701         field_init_shorthand,
 702         file,
 703         fill,
 704         flags,
 705         float,
 706         float_to_int_unchecked,
 707         floorf32,
 708         floorf64,
 709         fmaf32,
 710         fmaf64,
 711         fmt,
 712         fmul_fast,
 713         fn_align,
 714         fn_must_use,
 715         fn_mut,
 716         fn_once,
 717         fn_once_output,
 718         forbid,
 719         forget,
 720         format,
 721         format_args,
 722         format_args_capture,
 723         format_args_macro,
 724         format_args_nl,
 725         format_macro,
 726         freeze,
 727         freg,
 728         frem_fast,
 729         from,
 730         from_desugaring,
 731         from_iter,
 732         from_method,
 733         from_output,
 734         from_residual,
 735         from_size_align_unchecked,
 736         from_usize,
 737         from_yeet,
 738         fsub_fast,
 739         fundamental,
 740         future,
 741         future_trait,
 742         gdb_script_file,
 743         ge,
 744         gen_future,
 745         gen_kill,
 746         generator,
 747         generator_clone,
 748         generator_state,
 749         generators,
 750         generic_arg_infer,
 751         generic_assert,
 752         generic_associated_types,
 753         generic_associated_types_extended,
 754         generic_const_exprs,
 755         generic_param_attrs,
 756         get_context,
 757         global_allocator,
 758         global_asm,
 759         globs,
 760         gt,
 761         half_open_range_patterns,
 762         half_open_range_patterns_in_slices,
 763         hash,
 764         hexagon_target_feature,
 765         hidden,
 766         homogeneous_aggregate,
 767         html_favicon_url,
 768         html_logo_url,
 769         html_no_source,
 770         html_playground_url,
 771         html_root_url,
 772         hwaddress,
 773         i,
 774         i128,
 775         i128_type,
 776         i16,
 777         i32,
 778         i64,
 779         i8,
 780         ident,
 781         identity_future,
 782         if_let,
 783         if_let_guard,
 784         if_while_or_patterns,
 785         ignore,
 786         impl_header_lifetime_elision,
 787         impl_lint_pass,
 788         impl_trait_in_bindings,
 789         impl_trait_in_fn_trait_return,
 790         impl_trait_projections,
 791         implied_by,
 792         import,
 793         import_name_type,
 794         import_shadowing,
 795         imported_main,
 796         in_band_lifetimes,
 797         include,
 798         include_bytes,
 799         include_bytes_macro,
 800         include_str,
 801         include_str_macro,
 802         inclusive_range_syntax,
 803         index,
 804         index_mut,
 805         infer_outlives_requirements,
 806         infer_static_outlives_requirements,
 807         inherent_associated_types,
 808         inherit,
 809         inlateout,
 810         inline,
 811         inline_const,
 812         inline_const_pat,
 813         inout,
 814         instruction_set,
 815         integer_: "integer",
 816         integral,
 817         into_future,
 818         into_iter,
 819         intra_doc_pointers,
 820         intrinsics,
 821         irrefutable_let_patterns,
 822         isa_attribute,
 823         isize,
 824         issue,
 825         issue_5723_bootstrap,
 826         issue_tracker_base_url,
 827         item,
 828         item_like_imports,
 829         iter,
 830         iter_repeat,
 831         iterator_collect_fn,
 832         kcfi,
 833         keyword,
 834         kind,
 835         kreg,
 836         kreg0,
 837         label,
 838         label_break_value,
 839         lang,
 840         lang_items,
 841         large_assignments,
 842         lateout,
 843         lazy_normalization_consts,
 844         le,
 845         len,
 846         let_chains,
 847         let_else,
 848         lhs,
 849         lib,
 850         libc,
 851         lifetime,
 852         lifetimes,
 853         likely,
 854         line,
 855         link,
 856         link_args,
 857         link_cfg,
 858         link_llvm_intrinsics,
 859         link_name,
 860         link_ordinal,
 861         link_section,
 862         linkage,
 863         linker,
 864         lint_reasons,
 865         literal,
 866         load,
 867         loaded_from_disk,
 868         local,
 869         local_inner_macros,
 870         log10f32,
 871         log10f64,
 872         log2f32,
 873         log2f64,
 874         log_syntax,
 875         logf32,
 876         logf64,
 877         loop_break_value,
 878         lt,
 879         macro_at_most_once_rep,
 880         macro_attributes_in_derive_output,
 881         macro_escape,
 882         macro_export,
 883         macro_lifetime_matcher,
 884         macro_literal_matcher,
 885         macro_metavar_expr,
 886         macro_reexport,
 887         macro_use,
 888         macro_vis_matcher,
 889         macros_in_extern,
 890         main,
 891         managed_boxes,
 892         manually_drop,
 893         map,
 894         marker,
 895         marker_trait_attr,
 896         masked,
 897         match_beginning_vert,
 898         match_default_bindings,
 899         matches_macro,
 900         maxnumf32,
 901         maxnumf64,
 902         may_dangle,
 903         may_unwind,
 904         maybe_uninit,
 905         maybe_uninit_uninit,
 906         maybe_uninit_zeroed,
 907         mem_discriminant,
 908         mem_drop,
 909         mem_forget,
 910         mem_replace,
 911         mem_size_of,
 912         mem_size_of_val,
 913         mem_uninitialized,
 914         mem_variant_count,
 915         mem_zeroed,
 916         member_constraints,
 917         memory,
 918         memtag,
 919         message,
 920         meta,
 921         metadata_type,
 922         min_align_of,
 923         min_align_of_val,
 924         min_const_fn,
 925         min_const_generics,
 926         min_const_unsafe_fn,
 927         min_specialization,
 928         min_type_alias_impl_trait,
 929         minnumf32,
 930         minnumf64,
 931         mips_target_feature,
 932         miri,
 933         misc,
 934         mmx_reg,
 935         modifiers,
 936         module,
 937         module_path,
 938         more_qualified_paths,
 939         more_struct_aliases,
 940         movbe_target_feature,
 941         move_ref_pattern,
 942         move_size_limit,
 943         mul,
 944         mul_assign,
 945         mul_with_overflow,
 946         multiple_supertrait_upcastable,
 947         must_not_suspend,
 948         must_use,
 949         naked,
 950         naked_functions,
 951         name,
 952         names,
 953         native_link_modifiers,
 954         native_link_modifiers_as_needed,
 955         native_link_modifiers_bundle,
 956         native_link_modifiers_verbatim,
 957         native_link_modifiers_whole_archive,
 958         natvis_file,
 959         ne,
 960         nearbyintf32,
 961         nearbyintf64,
 962         needs_allocator,
 963         needs_drop,
 964         needs_panic_runtime,
 965         neg,
 966         negate_unsigned,
 967         negative_impls,
 968         neon,
 969         never,
 970         never_type,
 971         never_type_fallback,
 972         new,
 973         new_binary,
 974         new_debug,
 975         new_display,
 976         new_lower_exp,
 977         new_lower_hex,
 978         new_octal,
 979         new_pointer,
 980         new_unchecked,
 981         new_upper_exp,
 982         new_upper_hex,
 983         new_v1,
 984         new_v1_formatted,
 985         next,
 986         nll,
 987         no,
 988         no_builtins,
 989         no_core,
 990         no_coverage,
 991         no_crate_inject,
 992         no_debug,
 993         no_default_passes,
 994         no_implicit_prelude,
 995         no_inline,
 996         no_link,
 997         no_main,
 998         no_mangle,
 999         no_sanitize,
1000         no_stack_check,
1001         no_start,
1002         no_std,
1003         nomem,
1004         non_ascii_idents,
1005         non_exhaustive,
1006         non_exhaustive_omitted_patterns_lint,
1007         non_modrs_mods,
1008         nontemporal_store,
1009         noop_method_borrow,
1010         noop_method_clone,
1011         noop_method_deref,
1012         noreturn,
1013         nostack,
1014         not,
1015         notable_trait,
1016         note,
1017         object_safe_for_dispatch,
1018         of,
1019         offset,
1020         omit_gdb_pretty_printer_section,
1021         on,
1022         on_unimplemented,
1023         oom,
1024         opaque,
1025         ops,
1026         opt_out_copy,
1027         optimize,
1028         optimize_attribute,
1029         optin_builtin_traits,
1030         option,
1031         option_env,
1032         options,
1033         or,
1034         or_patterns,
1035         other,
1036         out,
1037         overlapping_marker_traits,
1038         owned_box,
1039         packed,
1040         panic,
1041         panic_2015,
1042         panic_2021,
1043         panic_abort,
1044         panic_bounds_check,
1045         panic_cannot_unwind,
1046         panic_display,
1047         panic_fmt,
1048         panic_handler,
1049         panic_impl,
1050         panic_implementation,
1051         panic_info,
1052         panic_location,
1053         panic_nounwind,
1054         panic_runtime,
1055         panic_str,
1056         panic_unwind,
1057         panicking,
1058         param_attrs,
1059         parent_label,
1060         partial_cmp,
1061         partial_ord,
1062         passes,
1063         pat,
1064         pat_param,
1065         path,
1066         pattern_parentheses,
1067         phantom_data,
1068         pin,
1069         platform_intrinsics,
1070         plugin,
1071         plugin_registrar,
1072         plugins,
1073         pointee_trait,
1074         pointer,
1075         pointer_sized,
1076         poll,
1077         position,
1078         post_dash_lto: "post-lto",
1079         powerpc_target_feature,
1080         powf32,
1081         powf64,
1082         powif32,
1083         powif64,
1084         pre_dash_lto: "pre-lto",
1085         precise_pointer_size_matching,
1086         precision,
1087         pref_align_of,
1088         prefetch_read_data,
1089         prefetch_read_instruction,
1090         prefetch_write_data,
1091         prefetch_write_instruction,
1092         preg,
1093         prelude,
1094         prelude_import,
1095         preserves_flags,
1096         primitive,
1097         print_macro,
1098         println_macro,
1099         proc_dash_macro: "proc-macro",
1100         proc_macro,
1101         proc_macro_attribute,
1102         proc_macro_derive,
1103         proc_macro_expr,
1104         proc_macro_gen,
1105         proc_macro_hygiene,
1106         proc_macro_internals,
1107         proc_macro_mod,
1108         proc_macro_non_items,
1109         proc_macro_path_invoc,
1110         profiler_builtins,
1111         profiler_runtime,
1112         ptr,
1113         ptr_guaranteed_cmp,
1114         ptr_mask,
1115         ptr_null,
1116         ptr_null_mut,
1117         ptr_offset_from,
1118         ptr_offset_from_unsigned,
1119         pub_macro_rules,
1120         pub_restricted,
1121         public,
1122         pure,
1123         pushpop_unsafe,
1124         qreg,
1125         qreg_low4,
1126         qreg_low8,
1127         quad_precision_float,
1128         question_mark,
1129         quote,
1130         range_inclusive_new,
1131         raw_dylib,
1132         raw_eq,
1133         raw_identifiers,
1134         raw_ref_op,
1135         re_rebalance_coherence,
1136         read_enum,
1137         read_enum_variant,
1138         read_enum_variant_arg,
1139         read_struct,
1140         read_struct_field,
1141         readonly,
1142         realloc,
1143         reason,
1144         receiver,
1145         recursion_limit,
1146         reexport_test_harness_main,
1147         ref_unwind_safe_trait,
1148         reference,
1149         reflect,
1150         reg,
1151         reg16,
1152         reg32,
1153         reg64,
1154         reg_abcd,
1155         reg_byte,
1156         reg_iw,
1157         reg_nonzero,
1158         reg_pair,
1159         reg_ptr,
1160         reg_upper,
1161         register_attr,
1162         register_tool,
1163         relaxed_adts,
1164         relaxed_struct_unsize,
1165         rem,
1166         rem_assign,
1167         repr,
1168         repr128,
1169         repr_align,
1170         repr_align_enum,
1171         repr_packed,
1172         repr_simd,
1173         repr_transparent,
1174         require,
1175         residual,
1176         result,
1177         return_position_impl_trait_in_trait,
1178         rhs,
1179         rintf32,
1180         rintf64,
1181         riscv_target_feature,
1182         rlib,
1183         rotate_left,
1184         rotate_right,
1185         roundf32,
1186         roundf64,
1187         rt,
1188         rtm_target_feature,
1189         rust,
1190         rust_2015,
1191         rust_2015_preview,
1192         rust_2018,
1193         rust_2018_preview,
1194         rust_2021,
1195         rust_2021_preview,
1196         rust_2024,
1197         rust_2024_preview,
1198         rust_begin_unwind,
1199         rust_cold_cc,
1200         rust_eh_catch_typeinfo,
1201         rust_eh_personality,
1202         rustc,
1203         rustc_allocator,
1204         rustc_allocator_zeroed,
1205         rustc_allow_const_fn_unstable,
1206         rustc_allow_incoherent_impl,
1207         rustc_allowed_through_unstable_modules,
1208         rustc_attrs,
1209         rustc_box,
1210         rustc_builtin_macro,
1211         rustc_capture_analysis,
1212         rustc_clean,
1213         rustc_coherence_is_core,
1214         rustc_const_stable,
1215         rustc_const_unstable,
1216         rustc_conversion_suggestion,
1217         rustc_deallocator,
1218         rustc_def_path,
1219         rustc_default_body_unstable,
1220         rustc_deny_explicit_impl,
1221         rustc_diagnostic_item,
1222         rustc_diagnostic_macros,
1223         rustc_dirty,
1224         rustc_do_not_const_check,
1225         rustc_dummy,
1226         rustc_dump_env_program_clauses,
1227         rustc_dump_program_clauses,
1228         rustc_dump_user_substs,
1229         rustc_dump_vtable,
1230         rustc_effective_visibility,
1231         rustc_error,
1232         rustc_evaluate_where_clauses,
1233         rustc_expected_cgu_reuse,
1234         rustc_has_incoherent_inherent_impls,
1235         rustc_if_this_changed,
1236         rustc_inherit_overflow_checks,
1237         rustc_insignificant_dtor,
1238         rustc_layout,
1239         rustc_layout_scalar_valid_range_end,
1240         rustc_layout_scalar_valid_range_start,
1241         rustc_legacy_const_generics,
1242         rustc_lint_diagnostics,
1243         rustc_lint_opt_deny_field_access,
1244         rustc_lint_opt_ty,
1245         rustc_lint_query_instability,
1246         rustc_macro_transparency,
1247         rustc_main,
1248         rustc_mir,
1249         rustc_must_implement_one_of,
1250         rustc_nonnull_optimization_guaranteed,
1251         rustc_nounwind,
1252         rustc_object_lifetime_default,
1253         rustc_on_unimplemented,
1254         rustc_outlives,
1255         rustc_paren_sugar,
1256         rustc_partition_codegened,
1257         rustc_partition_reused,
1258         rustc_pass_by_value,
1259         rustc_peek,
1260         rustc_peek_definite_init,
1261         rustc_peek_liveness,
1262         rustc_peek_maybe_init,
1263         rustc_peek_maybe_uninit,
1264         rustc_polymorphize_error,
1265         rustc_private,
1266         rustc_proc_macro_decls,
1267         rustc_promotable,
1268         rustc_reallocator,
1269         rustc_regions,
1270         rustc_reservation_impl,
1271         rustc_safe_intrinsic,
1272         rustc_serialize,
1273         rustc_skip_array_during_method_dispatch,
1274         rustc_specialization_trait,
1275         rustc_std_internal_symbol,
1276         rustc_strict_coherence,
1277         rustc_symbol_name,
1278         rustc_test_marker,
1279         rustc_then_this_would_need,
1280         rustc_trivial_field_reads,
1281         rustc_unsafe_specialization_marker,
1282         rustc_variance,
1283         rustdoc,
1284         rustdoc_internals,
1285         rustdoc_missing_doc_code_examples,
1286         rustfmt,
1287         rvalue_static_promotion,
1288         s,
1289         safety,
1290         sanitize,
1291         sanitizer_runtime,
1292         saturating_add,
1293         saturating_sub,
1294         self_in_typedefs,
1295         self_struct_ctor,
1296         semitransparent,
1297         shadow_call_stack,
1298         shl,
1299         shl_assign,
1300         should_panic,
1301         shr,
1302         shr_assign,
1303         sig_dfl,
1304         sig_ign,
1305         simd,
1306         simd_add,
1307         simd_and,
1308         simd_arith_offset,
1309         simd_as,
1310         simd_bitmask,
1311         simd_cast,
1312         simd_cast_ptr,
1313         simd_ceil,
1314         simd_div,
1315         simd_eq,
1316         simd_expose_addr,
1317         simd_extract,
1318         simd_fabs,
1319         simd_fcos,
1320         simd_fexp,
1321         simd_fexp2,
1322         simd_ffi,
1323         simd_flog,
1324         simd_flog10,
1325         simd_flog2,
1326         simd_floor,
1327         simd_fma,
1328         simd_fmax,
1329         simd_fmin,
1330         simd_fpow,
1331         simd_fpowi,
1332         simd_from_exposed_addr,
1333         simd_fsin,
1334         simd_fsqrt,
1335         simd_gather,
1336         simd_ge,
1337         simd_gt,
1338         simd_insert,
1339         simd_le,
1340         simd_lt,
1341         simd_mul,
1342         simd_ne,
1343         simd_neg,
1344         simd_or,
1345         simd_reduce_add_ordered,
1346         simd_reduce_add_unordered,
1347         simd_reduce_all,
1348         simd_reduce_and,
1349         simd_reduce_any,
1350         simd_reduce_max,
1351         simd_reduce_max_nanless,
1352         simd_reduce_min,
1353         simd_reduce_min_nanless,
1354         simd_reduce_mul_ordered,
1355         simd_reduce_mul_unordered,
1356         simd_reduce_or,
1357         simd_reduce_xor,
1358         simd_rem,
1359         simd_round,
1360         simd_saturating_add,
1361         simd_saturating_sub,
1362         simd_scatter,
1363         simd_select,
1364         simd_select_bitmask,
1365         simd_shl,
1366         simd_shr,
1367         simd_shuffle,
1368         simd_sub,
1369         simd_trunc,
1370         simd_xor,
1371         since,
1372         sinf32,
1373         sinf64,
1374         size,
1375         size_of,
1376         size_of_val,
1377         sized,
1378         skip,
1379         slice,
1380         slice_len_fn,
1381         slice_patterns,
1382         slicing_syntax,
1383         soft,
1384         specialization,
1385         speed,
1386         spotlight,
1387         sqrtf32,
1388         sqrtf64,
1389         sreg,
1390         sreg_low16,
1391         sse,
1392         sse4a_target_feature,
1393         stable,
1394         staged_api,
1395         start,
1396         state,
1397         static_in_const,
1398         static_nobundle,
1399         static_recursion,
1400         staticlib,
1401         std,
1402         std_panic,
1403         std_panic_2015_macro,
1404         std_panic_macro,
1405         stmt,
1406         stmt_expr_attributes,
1407         stop_after_dataflow,
1408         store,
1409         str,
1410         str_split_whitespace,
1411         str_trim,
1412         str_trim_end,
1413         str_trim_start,
1414         strict_provenance,
1415         string_deref_patterns,
1416         stringify,
1417         struct_field_attributes,
1418         struct_inherit,
1419         struct_variant,
1420         structural_match,
1421         structural_peq,
1422         structural_teq,
1423         sty,
1424         sub,
1425         sub_assign,
1426         sub_with_overflow,
1427         suggestion,
1428         sym,
1429         sync,
1430         t32,
1431         target,
1432         target_abi,
1433         target_arch,
1434         target_endian,
1435         target_env,
1436         target_family,
1437         target_feature,
1438         target_feature_11,
1439         target_has_atomic,
1440         target_has_atomic_equal_alignment,
1441         target_has_atomic_load_store,
1442         target_os,
1443         target_pointer_width,
1444         target_thread_local,
1445         target_vendor,
1446         tbm_target_feature,
1447         termination,
1448         termination_trait,
1449         termination_trait_test,
1450         test,
1451         test_2018_feature,
1452         test_accepted_feature,
1453         test_case,
1454         test_removed_feature,
1455         test_runner,
1456         test_unstable_lint,
1457         thread,
1458         thread_local,
1459         thread_local_macro,
1460         thumb2,
1461         thumb_mode: "thumb-mode",
1462         tmm_reg,
1463         to_string,
1464         to_vec,
1465         todo_macro,
1466         tool_attributes,
1467         tool_lints,
1468         trace_macros,
1469         track_caller,
1470         trait_alias,
1471         trait_upcasting,
1472         transmute,
1473         transmute_opts,
1474         transmute_trait,
1475         transparent,
1476         transparent_enums,
1477         transparent_unions,
1478         trivial_bounds,
1479         truncf32,
1480         truncf64,
1481         try_blocks,
1482         try_capture,
1483         try_from,
1484         try_into,
1485         try_trait_v2,
1486         tt,
1487         tuple,
1488         tuple_indexing,
1489         tuple_trait,
1490         two_phase,
1491         ty,
1492         type_alias_enum_variants,
1493         type_alias_impl_trait,
1494         type_ascribe,
1495         type_ascription,
1496         type_changing_struct_update,
1497         type_id,
1498         type_length_limit,
1499         type_macros,
1500         type_name,
1501         u128,
1502         u16,
1503         u32,
1504         u64,
1505         u8,
1506         unaligned_volatile_load,
1507         unaligned_volatile_store,
1508         unboxed_closures,
1509         unchecked_add,
1510         unchecked_div,
1511         unchecked_mul,
1512         unchecked_rem,
1513         unchecked_shl,
1514         unchecked_shr,
1515         unchecked_sub,
1516         underscore_const_names,
1517         underscore_imports,
1518         underscore_lifetimes,
1519         uniform_paths,
1520         unimplemented_macro,
1521         unit,
1522         universal_impl_trait,
1523         unix,
1524         unix_sigpipe,
1525         unlikely,
1526         unmarked_api,
1527         unpin,
1528         unreachable,
1529         unreachable_2015,
1530         unreachable_2015_macro,
1531         unreachable_2021,
1532         unreachable_code,
1533         unreachable_display,
1534         unreachable_macro,
1535         unrestricted_attribute_tokens,
1536         unsafe_block_in_unsafe_fn,
1537         unsafe_cell,
1538         unsafe_no_drop_flag,
1539         unsafe_pin_internals,
1540         unsize,
1541         unsized_fn_params,
1542         unsized_locals,
1543         unsized_tuple_coercion,
1544         unstable,
1545         unstable_location_reason_default: "this crate is being loaded from the sysroot, an \
1546                           unstable location; did you mean to load this crate \
1547                           from crates.io via `Cargo.toml` instead?",
1548         untagged_unions,
1549         unused_imports,
1550         unwind,
1551         unwind_attributes,
1552         unwind_safe_trait,
1553         unwrap,
1554         unwrap_or,
1555         use_extern_macros,
1556         use_nested_groups,
1557         used,
1558         used_with_arg,
1559         using,
1560         usize,
1561         v1,
1562         va_arg,
1563         va_copy,
1564         va_end,
1565         va_list,
1566         va_start,
1567         val,
1568         validity,
1569         values,
1570         var,
1571         variant_count,
1572         vec,
1573         vec_macro,
1574         version,
1575         vfp2,
1576         vis,
1577         visible_private_types,
1578         volatile,
1579         volatile_copy_memory,
1580         volatile_copy_nonoverlapping_memory,
1581         volatile_load,
1582         volatile_set_memory,
1583         volatile_store,
1584         vreg,
1585         vreg_low16,
1586         vtable_align,
1587         vtable_size,
1588         warn,
1589         wasm_abi,
1590         wasm_import_module,
1591         wasm_target_feature,
1592         while_let,
1593         width,
1594         windows,
1595         windows_subsystem,
1596         with_negative_coherence,
1597         wrapping_add,
1598         wrapping_mul,
1599         wrapping_sub,
1600         wreg,
1601         write_bytes,
1602         write_macro,
1603         write_str,
1604         writeln_macro,
1605         x87_reg,
1606         xer,
1607         xmm_reg,
1608         yeet_desugar_details,
1609         yeet_expr,
1610         ymm_reg,
1611         zmm_reg,
1612     }
1613 }
1614
1615 #[derive(Copy, Clone, Eq, HashStable_Generic, Encodable, Decodable)]
1616 pub struct Ident {
1617     pub name: Symbol,
1618     pub span: Span,
1619 }
1620
1621 impl Ident {
1622     #[inline]
1623     /// Constructs a new identifier from a symbol and a span.
1624     pub const fn new(name: Symbol, span: Span) -> Ident {
1625         Ident { name, span }
1626     }
1627
1628     /// Constructs a new identifier with a dummy span.
1629     #[inline]
1630     pub const fn with_dummy_span(name: Symbol) -> Ident {
1631         Ident::new(name, DUMMY_SP)
1632     }
1633
1634     #[inline]
1635     pub fn empty() -> Ident {
1636         Ident::with_dummy_span(kw::Empty)
1637     }
1638
1639     /// Maps a string to an identifier with a dummy span.
1640     pub fn from_str(string: &str) -> Ident {
1641         Ident::with_dummy_span(Symbol::intern(string))
1642     }
1643
1644     /// Maps a string and a span to an identifier.
1645     pub fn from_str_and_span(string: &str, span: Span) -> Ident {
1646         Ident::new(Symbol::intern(string), span)
1647     }
1648
1649     /// Replaces `lo` and `hi` with those from `span`, but keep hygiene context.
1650     pub fn with_span_pos(self, span: Span) -> Ident {
1651         Ident::new(self.name, span.with_ctxt(self.span.ctxt()))
1652     }
1653
1654     pub fn without_first_quote(self) -> Ident {
1655         Ident::new(Symbol::intern(self.as_str().trim_start_matches('\'')), self.span)
1656     }
1657
1658     /// "Normalize" ident for use in comparisons using "item hygiene".
1659     /// Identifiers with same string value become same if they came from the same macro 2.0 macro
1660     /// (e.g., `macro` item, but not `macro_rules` item) and stay different if they came from
1661     /// different macro 2.0 macros.
1662     /// Technically, this operation strips all non-opaque marks from ident's syntactic context.
1663     pub fn normalize_to_macros_2_0(self) -> Ident {
1664         Ident::new(self.name, self.span.normalize_to_macros_2_0())
1665     }
1666
1667     /// "Normalize" ident for use in comparisons using "local variable hygiene".
1668     /// Identifiers with same string value become same if they came from the same non-transparent
1669     /// macro (e.g., `macro` or `macro_rules!` items) and stay different if they came from different
1670     /// non-transparent macros.
1671     /// Technically, this operation strips all transparent marks from ident's syntactic context.
1672     #[inline]
1673     pub fn normalize_to_macro_rules(self) -> Ident {
1674         Ident::new(self.name, self.span.normalize_to_macro_rules())
1675     }
1676
1677     /// Access the underlying string. This is a slowish operation because it
1678     /// requires locking the symbol interner.
1679     ///
1680     /// Note that the lifetime of the return value is a lie. See
1681     /// `Symbol::as_str()` for details.
1682     pub fn as_str(&self) -> &str {
1683         self.name.as_str()
1684     }
1685 }
1686
1687 impl PartialEq for Ident {
1688     #[inline]
1689     fn eq(&self, rhs: &Self) -> bool {
1690         self.name == rhs.name && self.span.eq_ctxt(rhs.span)
1691     }
1692 }
1693
1694 impl Hash for Ident {
1695     fn hash<H: Hasher>(&self, state: &mut H) {
1696         self.name.hash(state);
1697         self.span.ctxt().hash(state);
1698     }
1699 }
1700
1701 impl fmt::Debug for Ident {
1702     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1703         fmt::Display::fmt(self, f)?;
1704         fmt::Debug::fmt(&self.span.ctxt(), f)
1705     }
1706 }
1707
1708 /// This implementation is supposed to be used in error messages, so it's expected to be identical
1709 /// to printing the original identifier token written in source code (`token_to_string`),
1710 /// except that AST identifiers don't keep the rawness flag, so we have to guess it.
1711 impl fmt::Display for Ident {
1712     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1713         fmt::Display::fmt(&IdentPrinter::new(self.name, self.is_raw_guess(), None), f)
1714     }
1715 }
1716
1717 /// The most general type to print identifiers.
1718 ///
1719 /// AST pretty-printer is used as a fallback for turning AST structures into token streams for
1720 /// proc macros. Additionally, proc macros may stringify their input and expect it survive the
1721 /// stringification (especially true for proc macro derives written between Rust 1.15 and 1.30).
1722 /// So we need to somehow pretty-print `$crate` in a way preserving at least some of its
1723 /// hygiene data, most importantly name of the crate it refers to.
1724 /// As a result we print `$crate` as `crate` if it refers to the local crate
1725 /// and as `::other_crate_name` if it refers to some other crate.
1726 /// Note, that this is only done if the ident token is printed from inside of AST pretty-printing,
1727 /// but not otherwise. Pretty-printing is the only way for proc macros to discover token contents,
1728 /// so we should not perform this lossy conversion if the top level call to the pretty-printer was
1729 /// done for a token stream or a single token.
1730 pub struct IdentPrinter {
1731     symbol: Symbol,
1732     is_raw: bool,
1733     /// Span used for retrieving the crate name to which `$crate` refers to,
1734     /// if this field is `None` then the `$crate` conversion doesn't happen.
1735     convert_dollar_crate: Option<Span>,
1736 }
1737
1738 impl IdentPrinter {
1739     /// The most general `IdentPrinter` constructor. Do not use this.
1740     pub fn new(symbol: Symbol, is_raw: bool, convert_dollar_crate: Option<Span>) -> IdentPrinter {
1741         IdentPrinter { symbol, is_raw, convert_dollar_crate }
1742     }
1743
1744     /// This implementation is supposed to be used when printing identifiers
1745     /// as a part of pretty-printing for larger AST pieces.
1746     /// Do not use this either.
1747     pub fn for_ast_ident(ident: Ident, is_raw: bool) -> IdentPrinter {
1748         IdentPrinter::new(ident.name, is_raw, Some(ident.span))
1749     }
1750 }
1751
1752 impl fmt::Display for IdentPrinter {
1753     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1754         if self.is_raw {
1755             f.write_str("r#")?;
1756         } else if self.symbol == kw::DollarCrate {
1757             if let Some(span) = self.convert_dollar_crate {
1758                 let converted = span.ctxt().dollar_crate_name();
1759                 if !converted.is_path_segment_keyword() {
1760                     f.write_str("::")?;
1761                 }
1762                 return fmt::Display::fmt(&converted, f);
1763             }
1764         }
1765         fmt::Display::fmt(&self.symbol, f)
1766     }
1767 }
1768
1769 /// An newtype around `Ident` that calls [Ident::normalize_to_macro_rules] on
1770 /// construction.
1771 // FIXME(matthewj, petrochenkov) Use this more often, add a similar
1772 // `ModernIdent` struct and use that as well.
1773 #[derive(Copy, Clone, Eq, PartialEq, Hash)]
1774 pub struct MacroRulesNormalizedIdent(Ident);
1775
1776 impl MacroRulesNormalizedIdent {
1777     pub fn new(ident: Ident) -> Self {
1778         Self(ident.normalize_to_macro_rules())
1779     }
1780 }
1781
1782 impl fmt::Debug for MacroRulesNormalizedIdent {
1783     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1784         fmt::Debug::fmt(&self.0, f)
1785     }
1786 }
1787
1788 impl fmt::Display for MacroRulesNormalizedIdent {
1789     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1790         fmt::Display::fmt(&self.0, f)
1791     }
1792 }
1793
1794 /// An interned string.
1795 ///
1796 /// Internally, a `Symbol` is implemented as an index, and all operations
1797 /// (including hashing, equality, and ordering) operate on that index. The use
1798 /// of `rustc_index::newtype_index!` means that `Option<Symbol>` only takes up 4 bytes,
1799 /// because `rustc_index::newtype_index!` reserves the last 256 values for tagging purposes.
1800 ///
1801 /// Note that `Symbol` cannot directly be a `rustc_index::newtype_index!` because it
1802 /// implements `fmt::Debug`, `Encodable`, and `Decodable` in special ways.
1803 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
1804 pub struct Symbol(SymbolIndex);
1805
1806 rustc_index::newtype_index! {
1807     struct SymbolIndex {}
1808 }
1809
1810 impl Symbol {
1811     const fn new(n: u32) -> Self {
1812         Symbol(SymbolIndex::from_u32(n))
1813     }
1814
1815     /// for use in Decoder only
1816     pub fn new_from_decoded(n: u32) -> Self {
1817         Self::new(n)
1818     }
1819
1820     /// Maps a string to its interned representation.
1821     pub fn intern(string: &str) -> Self {
1822         with_session_globals(|session_globals| session_globals.symbol_interner.intern(string))
1823     }
1824
1825     /// Access the underlying string. This is a slowish operation because it
1826     /// requires locking the symbol interner.
1827     ///
1828     /// Note that the lifetime of the return value is a lie. It's not the same
1829     /// as `&self`, but actually tied to the lifetime of the underlying
1830     /// interner. Interners are long-lived, and there are very few of them, and
1831     /// this function is typically used for short-lived things, so in practice
1832     /// it works out ok.
1833     pub fn as_str(&self) -> &str {
1834         with_session_globals(|session_globals| unsafe {
1835             std::mem::transmute::<&str, &str>(session_globals.symbol_interner.get(*self))
1836         })
1837     }
1838
1839     pub fn as_u32(self) -> u32 {
1840         self.0.as_u32()
1841     }
1842
1843     pub fn is_empty(self) -> bool {
1844         self == kw::Empty
1845     }
1846
1847     /// This method is supposed to be used in error messages, so it's expected to be
1848     /// identical to printing the original identifier token written in source code
1849     /// (`token_to_string`, `Ident::to_string`), except that symbols don't keep the rawness flag
1850     /// or edition, so we have to guess the rawness using the global edition.
1851     pub fn to_ident_string(self) -> String {
1852         Ident::with_dummy_span(self).to_string()
1853     }
1854 }
1855
1856 impl fmt::Debug for Symbol {
1857     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1858         fmt::Debug::fmt(self.as_str(), f)
1859     }
1860 }
1861
1862 impl fmt::Display for Symbol {
1863     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1864         fmt::Display::fmt(self.as_str(), f)
1865     }
1866 }
1867
1868 // takes advantage of `str::to_string` specialization
1869 impl ToString for Symbol {
1870     fn to_string(&self) -> String {
1871         self.as_str().to_string()
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
1982     #[doc(inline)]
1983     pub use super::sym_generated::*;
1984
1985     // Used from a macro in `librustc_feature/accepted.rs`
1986     pub use super::kw::MacroRules as macro_rules;
1987
1988     /// Get the symbol for an integer.
1989     ///
1990     /// The first few non-negative integers each have a static symbol and therefore
1991     /// are fast.
1992     pub fn integer<N: TryInto<usize> + Copy + ToString>(n: N) -> Symbol {
1993         if let Result::Ok(idx) = n.try_into() {
1994             if idx < 10 {
1995                 return Symbol::new(super::SYMBOL_DIGITS_BASE + idx as u32);
1996             }
1997         }
1998         Symbol::intern(&n.to_string())
1999     }
2000 }
2001
2002 impl Symbol {
2003     fn is_special(self) -> bool {
2004         self <= kw::Underscore
2005     }
2006
2007     fn is_used_keyword_always(self) -> bool {
2008         self >= kw::As && self <= kw::While
2009     }
2010
2011     fn is_used_keyword_conditional(self, edition: impl FnOnce() -> Edition) -> bool {
2012         (self >= kw::Async && self <= kw::Dyn) && edition() >= Edition::Edition2018
2013     }
2014
2015     fn is_unused_keyword_always(self) -> bool {
2016         self >= kw::Abstract && self <= kw::Yield
2017     }
2018
2019     fn is_unused_keyword_conditional(self, edition: impl FnOnce() -> Edition) -> bool {
2020         self == kw::Try && edition() >= Edition::Edition2018
2021     }
2022
2023     pub fn is_reserved(self, edition: impl Copy + FnOnce() -> Edition) -> bool {
2024         self.is_special()
2025             || self.is_used_keyword_always()
2026             || self.is_unused_keyword_always()
2027             || self.is_used_keyword_conditional(edition)
2028             || self.is_unused_keyword_conditional(edition)
2029     }
2030
2031     /// A keyword or reserved identifier that can be used as a path segment.
2032     pub fn is_path_segment_keyword(self) -> bool {
2033         self == kw::Super
2034             || self == kw::SelfLower
2035             || self == kw::SelfUpper
2036             || self == kw::Crate
2037             || self == kw::PathRoot
2038             || self == kw::DollarCrate
2039     }
2040
2041     /// Returns `true` if the symbol is `true` or `false`.
2042     pub fn is_bool_lit(self) -> bool {
2043         self == kw::True || self == kw::False
2044     }
2045
2046     /// Returns `true` if this symbol can be a raw identifier.
2047     pub fn can_be_raw(self) -> bool {
2048         self != kw::Empty && self != kw::Underscore && !self.is_path_segment_keyword()
2049     }
2050
2051     /// Is this symbol was interned in compiler's `symbols!` macro
2052     pub fn is_preinterned(self) -> bool {
2053         self.as_u32() < PREINTERNED_SYMBOLS_COUNT
2054     }
2055 }
2056
2057 impl Ident {
2058     /// Returns `true` for reserved identifiers used internally for elided lifetimes,
2059     /// unnamed method parameters, crate root module, error recovery etc.
2060     pub fn is_special(self) -> bool {
2061         self.name.is_special()
2062     }
2063
2064     /// Returns `true` if the token is a keyword used in the language.
2065     pub fn is_used_keyword(self) -> bool {
2066         // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
2067         self.name.is_used_keyword_always()
2068             || self.name.is_used_keyword_conditional(|| self.span.edition())
2069     }
2070
2071     /// Returns `true` if the token is a keyword reserved for possible future use.
2072     pub fn is_unused_keyword(self) -> bool {
2073         // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
2074         self.name.is_unused_keyword_always()
2075             || self.name.is_unused_keyword_conditional(|| self.span.edition())
2076     }
2077
2078     /// Returns `true` if the token is either a special identifier or a keyword.
2079     pub fn is_reserved(self) -> bool {
2080         // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
2081         self.name.is_reserved(|| self.span.edition())
2082     }
2083
2084     /// A keyword or reserved identifier that can be used as a path segment.
2085     pub fn is_path_segment_keyword(self) -> bool {
2086         self.name.is_path_segment_keyword()
2087     }
2088
2089     /// We see this identifier in a normal identifier position, like variable name or a type.
2090     /// How was it written originally? Did it use the raw form? Let's try to guess.
2091     pub fn is_raw_guess(self) -> bool {
2092         self.name.can_be_raw() && self.is_reserved()
2093     }
2094 }