src/librustc_span/symbol.rs

   1 //! An "interner" is a data structure that associates values with usize tags and
   2 //! allows bidirectional lookup; i.e., given a value, one can easily find the
   3 //! type, and vice versa.
   4
   5 use rustc_arena::DroplessArena;
   6 use rustc_data_structures::fx::FxHashMap;
   7 use rustc_data_structures::stable_hasher::{HashStable, StableHasher, ToStableHashKey};
   8 use rustc_macros::{symbols, HashStable_Generic};
   9 use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
  10 use rustc_serialize::{UseSpecializedDecodable, UseSpecializedEncodable};
  11
  12 use std::cmp::{Ord, PartialEq, PartialOrd};
  13 use std::fmt;
  14 use std::hash::{Hash, Hasher};
  15 use std::str;
  16
  17 use crate::{Span, DUMMY_SP, GLOBALS};
  18
  19 #[cfg(test)]
  20 mod tests;
  21
  22 symbols! {
  23     // After modifying this list adjust `is_special`, `is_used_keyword`/`is_unused_keyword`,
  24     // this should be rarely necessary though if the keywords are kept in alphabetic order.
  25     Keywords {
  26         // Special reserved identifiers used internally for elided lifetimes,
  27         // unnamed method parameters, crate root module, error recovery etc.
  28         Invalid:            "",
  29         PathRoot:           "{{root}}",
  30         DollarCrate:        "$crate",
  31         Underscore:         "_",
  32
  33         // Keywords that are used in stable Rust.
  34         As:                 "as",
  35         Break:              "break",
  36         Const:              "const",
  37         Continue:           "continue",
  38         Crate:              "crate",
  39         Else:               "else",
  40         Enum:               "enum",
  41         Extern:             "extern",
  42         False:              "false",
  43         Fn:                 "fn",
  44         For:                "for",
  45         If:                 "if",
  46         Impl:               "impl",
  47         In:                 "in",
  48         Let:                "let",
  49         Loop:               "loop",
  50         Match:              "match",
  51         Mod:                "mod",
  52         Move:               "move",
  53         Mut:                "mut",
  54         Pub:                "pub",
  55         Ref:                "ref",
  56         Return:             "return",
  57         SelfLower:          "self",
  58         SelfUpper:          "Self",
  59         Static:             "static",
  60         Struct:             "struct",
  61         Super:              "super",
  62         Trait:              "trait",
  63         True:               "true",
  64         Type:               "type",
  65         Unsafe:             "unsafe",
  66         Use:                "use",
  67         Where:              "where",
  68         While:              "while",
  69
  70         // Keywords that are used in unstable Rust or reserved for future use.
  71         Abstract:           "abstract",
  72         Become:             "become",
  73         Box:                "box",
  74         Do:                 "do",
  75         Final:              "final",
  76         Macro:              "macro",
  77         Override:           "override",
  78         Priv:               "priv",
  79         Typeof:             "typeof",
  80         Unsized:            "unsized",
  81         Virtual:            "virtual",
  82         Yield:              "yield",
  83
  84         // Edition-specific keywords that are used in stable Rust.
  85         Async:              "async", // >= 2018 Edition only
  86         Await:              "await", // >= 2018 Edition only
  87         Dyn:                "dyn", // >= 2018 Edition only
  88
  89         // Edition-specific keywords that are used in unstable Rust or reserved for future use.
  90         Try:                "try", // >= 2018 Edition only
  91
  92         // Special lifetime names
  93         UnderscoreLifetime: "'_",
  94         StaticLifetime:     "'static",
  95
  96         // Weak keywords, have special meaning only in specific contexts.
  97         Auto:               "auto",
  98         Catch:              "catch",
  99         Default:            "default",
 100         MacroRules:         "macro_rules",
 101         Raw:                "raw",
 102         Union:              "union",
 103     }
 104
 105     // Symbols that can be referred to with rustc_span::sym::*. The symbol is
 106     // the stringified identifier unless otherwise specified (e.g.
 107     // `proc_dash_macro` represents "proc-macro").
 108     //
 109     // As well as the symbols listed, there are symbols for the the strings
 110     // "0", "1", ..., "9", which are accessible via `sym::integer`.
 111     Symbols {
 112         aarch64_target_feature,
 113         abi,
 114         abi_amdgpu_kernel,
 115         abi_efiapi,
 116         abi_msp430_interrupt,
 117         abi_ptx,
 118         abi_sysv64,
 119         abi_thiscall,
 120         abi_unadjusted,
 121         abi_vectorcall,
 122         abi_x86_interrupt,
 123         abi_avr_interrupt,
 124         abort,
 125         aborts,
 126         address,
 127         add_with_overflow,
 128         advanced_slice_patterns,
 129         adx_target_feature,
 130         alias,
 131         align,
 132         alignstack,
 133         all,
 134         allocator,
 135         allocator_internals,
 136         alloc_error_handler,
 137         allow,
 138         allowed,
 139         allow_fail,
 140         allow_internal_unsafe,
 141         allow_internal_unstable,
 142         allow_internal_unstable_backcompat_hack,
 143         always,
 144         and,
 145         any,
 146         arbitrary_enum_discriminant,
 147         arbitrary_self_types,
 148         Arc,
 149         Arguments,
 150         ArgumentV1,
 151         arith_offset,
 152         arm_target_feature,
 153         asm,
 154         assert,
 155         associated_consts,
 156         associated_type_bounds,
 157         associated_type_defaults,
 158         associated_types,
 159         assume_init,
 160         async_await,
 161         async_closure,
 162         attr,
 163         attributes,
 164         attr_literals,
 165         att_syntax,
 166         augmented_assignments,
 167         automatically_derived,
 168         avx512_target_feature,
 169         await_macro,
 170         begin_panic,
 171         bench,
 172         bin,
 173         bind_by_move_pattern_guards,
 174         bindings_after_at,
 175         block,
 176         bool,
 177         borrowck_graphviz_format,
 178         borrowck_graphviz_postflow,
 179         borrowck_graphviz_preflow,
 180         box_patterns,
 181         box_syntax,
 182         braced_empty_structs,
 183         bswap,
 184         bitreverse,
 185         C,
 186         caller_location,
 187         cdylib,
 188         cfg,
 189         cfg_accessible,
 190         cfg_attr,
 191         cfg_attr_multi,
 192         cfg_doctest,
 193         cfg_sanitize,
 194         cfg_target_feature,
 195         cfg_target_has_atomic,
 196         cfg_target_thread_local,
 197         cfg_target_vendor,
 198         cfg_version,
 199         char,
 200         clippy,
 201         clone,
 202         Clone,
 203         clone_closures,
 204         clone_from,
 205         closure_to_fn_coercion,
 206         cmp,
 207         cmpxchg16b_target_feature,
 208         cold,
 209         column,
 210         compile_error,
 211         compiler_builtins,
 212         concat,
 213         concat_idents,
 214         conservative_impl_trait,
 215         console,
 216         const_compare_raw_pointers,
 217         const_constructor,
 218         const_eval_limit,
 219         const_extern_fn,
 220         const_fn,
 221         const_fn_union,
 222         const_generics,
 223         const_if_match,
 224         const_indexing,
 225         const_in_array_repeat_expressions,
 226         const_let,
 227         const_loop,
 228         const_mut_refs,
 229         const_panic,
 230         const_precise_live_drops,
 231         const_raw_ptr_deref,
 232         const_raw_ptr_to_usize_cast,
 233         const_transmute,
 234         const_trait_bound_opt_out,
 235         const_trait_impl,
 236         contents,
 237         context,
 238         convert,
 239         Copy,
 240         copy_closures,
 241         core,
 242         core_intrinsics,
 243         count_code_region,
 244         crate_id,
 245         crate_in_paths,
 246         crate_local,
 247         crate_name,
 248         crate_type,
 249         crate_visibility_modifier,
 250         ctpop,
 251         cttz,
 252         cttz_nonzero,
 253         ctlz,
 254         ctlz_nonzero,
 255         custom_attribute,
 256         custom_derive,
 257         custom_inner_attributes,
 258         custom_test_frameworks,
 259         c_variadic,
 260         debug_trait,
 261         declare_lint_pass,
 262         decl_macro,
 263         debug,
 264         Debug,
 265         Decodable,
 266         Default,
 267         default_lib_allocator,
 268         default_type_parameter_fallback,
 269         default_type_params,
 270         delay_span_bug_from_inside_query,
 271         deny,
 272         deprecated,
 273         deref,
 274         deref_mut,
 275         derive,
 276         diagnostic,
 277         direct,
 278         discriminant_value,
 279         doc,
 280         doc_alias,
 281         doc_cfg,
 282         doc_keyword,
 283         doc_masked,
 284         doctest,
 285         document_private_items,
 286         dotdoteq_in_patterns,
 287         dotdot_in_tuple_patterns,
 288         double_braced_crate: "{{crate}}",
 289         double_braced_impl: "{{impl}}",
 290         double_braced_misc: "{{misc}}",
 291         double_braced_closure: "{{closure}}",
 292         double_braced_constructor: "{{constructor}}",
 293         double_braced_constant: "{{constant}}",
 294         double_braced_opaque: "{{opaque}}",
 295         dropck_eyepatch,
 296         dropck_parametricity,
 297         drop_types_in_const,
 298         dylib,
 299         dyn_trait,
 300         eh_personality,
 301         enable,
 302         Encodable,
 303         env,
 304         eq,
 305         err,
 306         Err,
 307         Eq,
 308         Equal,
 309         enclosing_scope,
 310         except,
 311         exclusive_range_pattern,
 312         exhaustive_integer_patterns,
 313         exhaustive_patterns,
 314         existential_type,
 315         expected,
 316         export_name,
 317         expr,
 318         extern_absolute_paths,
 319         external_doc,
 320         extern_crate_item_prelude,
 321         extern_crate_self,
 322         extern_in_paths,
 323         extern_prelude,
 324         extern_types,
 325         f16c_target_feature,
 326         f32,
 327         f64,
 328         feature,
 329         ffi_const,
 330         ffi_pure,
 331         ffi_returns_twice,
 332         field,
 333         field_init_shorthand,
 334         file,
 335         fmt,
 336         fmt_internals,
 337         fn_must_use,
 338         forbid,
 339         format_args,
 340         format_args_nl,
 341         from,
 342         From,
 343         from_desugaring,
 344         from_error,
 345         from_generator,
 346         from_method,
 347         from_ok,
 348         from_usize,
 349         from_trait,
 350         fundamental,
 351         future,
 352         Future,
 353         FxHashSet,
 354         FxHashMap,
 355         gen_future,
 356         gen_kill,
 357         generators,
 358         generic_associated_types,
 359         generic_param_attrs,
 360         get_context,
 361         global_allocator,
 362         global_asm,
 363         globs,
 364         half_open_range_patterns,
 365         hash,
 366         Hash,
 367         HashSet,
 368         HashMap,
 369         hexagon_target_feature,
 370         hidden,
 371         homogeneous_aggregate,
 372         html_favicon_url,
 373         html_logo_url,
 374         html_no_source,
 375         html_playground_url,
 376         html_root_url,
 377         i128,
 378         i128_type,
 379         i16,
 380         i32,
 381         i64,
 382         i8,
 383         ident,
 384         if_let,
 385         if_while_or_patterns,
 386         ignore,
 387         inlateout,
 388         inout,
 389         impl_header_lifetime_elision,
 390         impl_lint_pass,
 391         impl_trait_in_bindings,
 392         import_shadowing,
 393         index,
 394         index_mut,
 395         in_band_lifetimes,
 396         include,
 397         include_bytes,
 398         include_str,
 399         inclusive_range_syntax,
 400         infer_outlives_requirements,
 401         infer_static_outlives_requirements,
 402         inline,
 403         intel,
 404         into_iter,
 405         IntoIterator,
 406         into_result,
 407         intrinsics,
 408         irrefutable_let_patterns,
 409         isize,
 410         issue,
 411         issue_5723_bootstrap,
 412         issue_tracker_base_url,
 413         item,
 414         item_context: "ItemContext",
 415         item_like_imports,
 416         iter,
 417         Iterator,
 418         keyword,
 419         kind,
 420         label,
 421         label_break_value,
 422         lang,
 423         lang_items,
 424         lateout,
 425         let_chains,
 426         lhs,
 427         lib,
 428         lifetime,
 429         line,
 430         link,
 431         linkage,
 432         link_args,
 433         link_cfg,
 434         link_llvm_intrinsics,
 435         link_name,
 436         link_ordinal,
 437         link_section,
 438         LintPass,
 439         lint_reasons,
 440         literal,
 441         llvm_asm,
 442         local_inner_macros,
 443         log_syntax,
 444         loop_break_value,
 445         macro_at_most_once_rep,
 446         macro_escape,
 447         macro_export,
 448         macro_lifetime_matcher,
 449         macro_literal_matcher,
 450         macro_reexport,
 451         macros_in_extern,
 452         macro_use,
 453         macro_vis_matcher,
 454         main,
 455         managed_boxes,
 456         marker,
 457         marker_trait_attr,
 458         masked,
 459         match_beginning_vert,
 460         match_default_bindings,
 461         may_dangle,
 462         maybe_uninit_uninit,
 463         maybe_uninit_zeroed,
 464         mem_uninitialized,
 465         mem_zeroed,
 466         member_constraints,
 467         memory,
 468         message,
 469         meta,
 470         min_align_of,
 471         min_const_fn,
 472         min_const_unsafe_fn,
 473         min_specialization,
 474         mips_target_feature,
 475         mmx_target_feature,
 476         module,
 477         module_path,
 478         more_struct_aliases,
 479         move_ref_pattern,
 480         move_val_init,
 481         movbe_target_feature,
 482         mul_with_overflow,
 483         must_use,
 484         naked,
 485         naked_functions,
 486         name,
 487         needs_allocator,
 488         needs_drop,
 489         needs_panic_runtime,
 490         negate_unsigned,
 491         negative_impls,
 492         never,
 493         never_type,
 494         never_type_fallback,
 495         new,
 496         next,
 497         __next,
 498         nll,
 499         no_builtins,
 500         no_core,
 501         no_crate_inject,
 502         no_debug,
 503         no_default_passes,
 504         no_implicit_prelude,
 505         no_inline,
 506         no_link,
 507         no_main,
 508         no_mangle,
 509         nomem,
 510         non_ascii_idents,
 511         None,
 512         non_exhaustive,
 513         non_modrs_mods,
 514         noreturn,
 515         no_niche,
 516         no_sanitize,
 517         nostack,
 518         no_stack_check,
 519         no_start,
 520         no_std,
 521         not,
 522         note,
 523         object_safe_for_dispatch,
 524         offset,
 525         Ok,
 526         omit_gdb_pretty_printer_section,
 527         on,
 528         on_unimplemented,
 529         oom,
 530         ops,
 531         optimize,
 532         optimize_attribute,
 533         optin_builtin_traits,
 534         option,
 535         Option,
 536         option_env,
 537         options,
 538         opt_out_copy,
 539         or,
 540         or_patterns,
 541         Ord,
 542         Ordering,
 543         out,
 544         Output,
 545         overlapping_marker_traits,
 546         packed,
 547         panic,
 548         panic_handler,
 549         panic_impl,
 550         panic_implementation,
 551         panic_runtime,
 552         parent_trait,
 553         partial_cmp,
 554         param_attrs,
 555         PartialEq,
 556         PartialOrd,
 557         passes,
 558         pat,
 559         path,
 560         pattern_parentheses,
 561         Pending,
 562         pin,
 563         Pin,
 564         pinned,
 565         platform_intrinsics,
 566         plugin,
 567         plugin_registrar,
 568         plugins,
 569         poll,
 570         Poll,
 571         powerpc_target_feature,
 572         precise_pointer_size_matching,
 573         pref_align_of,
 574         prelude,
 575         prelude_import,
 576         preserves_flags,
 577         primitive,
 578         proc_dash_macro: "proc-macro",
 579         proc_macro,
 580         proc_macro_attribute,
 581         proc_macro_def_site,
 582         proc_macro_derive,
 583         proc_macro_expr,
 584         proc_macro_gen,
 585         proc_macro_hygiene,
 586         proc_macro_internals,
 587         proc_macro_mod,
 588         proc_macro_non_items,
 589         proc_macro_path_invoc,
 590         profiler_runtime,
 591         ptr_guaranteed_eq,
 592         ptr_guaranteed_ne,
 593         ptr_offset_from,
 594         pub_restricted,
 595         pure,
 596         pushpop_unsafe,
 597         quad_precision_float,
 598         question_mark,
 599         quote,
 600         Range,
 601         RangeFrom,
 602         RangeFull,
 603         RangeInclusive,
 604         RangeTo,
 605         RangeToInclusive,
 606         raw_dylib,
 607         raw_identifiers,
 608         raw_ref_op,
 609         Rc,
 610         readonly,
 611         Ready,
 612         reason,
 613         recursion_limit,
 614         reexport_test_harness_main,
 615         reflect,
 616         register_attr,
 617         register_tool,
 618         relaxed_adts,
 619         repr,
 620         repr128,
 621         repr_align,
 622         repr_align_enum,
 623         repr_no_niche,
 624         repr_packed,
 625         repr_simd,
 626         repr_transparent,
 627         re_rebalance_coherence,
 628         result,
 629         Result,
 630         Return,
 631         rhs,
 632         riscv_target_feature,
 633         rlib,
 634         rotate_left,
 635         rotate_right,
 636         rt,
 637         rtm_target_feature,
 638         rust,
 639         rust_2015_preview,
 640         rust_2018_preview,
 641         rust_begin_unwind,
 642         rustc,
 643         RustcDecodable,
 644         RustcEncodable,
 645         rustc_allocator,
 646         rustc_allocator_nounwind,
 647         rustc_allow_const_fn_ptr,
 648         rustc_args_required_const,
 649         rustc_attrs,
 650         rustc_builtin_macro,
 651         rustc_clean,
 652         rustc_const_unstable,
 653         rustc_const_stable,
 654         rustc_conversion_suggestion,
 655         rustc_def_path,
 656         rustc_deprecated,
 657         rustc_diagnostic_item,
 658         rustc_diagnostic_macros,
 659         rustc_dirty,
 660         rustc_dummy,
 661         rustc_dump_env_program_clauses,
 662         rustc_dump_program_clauses,
 663         rustc_dump_user_substs,
 664         rustc_error,
 665         rustc_expected_cgu_reuse,
 666         rustc_if_this_changed,
 667         rustc_inherit_overflow_checks,
 668         rustc_layout,
 669         rustc_layout_scalar_valid_range_end,
 670         rustc_layout_scalar_valid_range_start,
 671         rustc_macro_transparency,
 672         rustc_mir,
 673         rustc_nonnull_optimization_guaranteed,
 674         rustc_object_lifetime_default,
 675         rustc_on_unimplemented,
 676         rustc_outlives,
 677         rustc_paren_sugar,
 678         rustc_partition_codegened,
 679         rustc_partition_reused,
 680         rustc_peek,
 681         rustc_peek_definite_init,
 682         rustc_peek_liveness,
 683         rustc_peek_maybe_init,
 684         rustc_peek_maybe_uninit,
 685         rustc_peek_indirectly_mutable,
 686         rustc_private,
 687         rustc_proc_macro_decls,
 688         rustc_promotable,
 689         rustc_regions,
 690         rustc_unsafe_specialization_marker,
 691         rustc_specialization_trait,
 692         rustc_stable,
 693         rustc_std_internal_symbol,
 694         rustc_symbol_name,
 695         rustc_synthetic,
 696         rustc_reservation_impl,
 697         rustc_test_marker,
 698         rustc_then_this_would_need,
 699         rustc_variance,
 700         rustfmt,
 701         rust_eh_personality,
 702         rust_oom,
 703         rvalue_static_promotion,
 704         sanitize,
 705         sanitizer_runtime,
 706         saturating_add,
 707         saturating_sub,
 708         _Self,
 709         self_in_typedefs,
 710         self_struct_ctor,
 711         send_trait,
 712         should_panic,
 713         simd,
 714         simd_extract,
 715         simd_ffi,
 716         simd_insert,
 717         since,
 718         size,
 719         size_of,
 720         slice_patterns,
 721         slicing_syntax,
 722         soft,
 723         Some,
 724         specialization,
 725         speed,
 726         sse4a_target_feature,
 727         stable,
 728         staged_api,
 729         start,
 730         static_in_const,
 731         staticlib,
 732         static_nobundle,
 733         static_recursion,
 734         std,
 735         std_inject,
 736         str,
 737         stringify,
 738         stmt,
 739         stmt_expr_attributes,
 740         stop_after_dataflow,
 741         struct_field_attributes,
 742         struct_inherit,
 743         structural_match,
 744         struct_variant,
 745         sty,
 746         sub_with_overflow,
 747         suggestion,
 748         sym,
 749         sync_trait,
 750         target_feature,
 751         target_feature_11,
 752         target_has_atomic,
 753         target_has_atomic_load_store,
 754         target_thread_local,
 755         task,
 756         _task_context,
 757         tbm_target_feature,
 758         termination_trait,
 759         termination_trait_test,
 760         test,
 761         test_2018_feature,
 762         test_accepted_feature,
 763         test_case,
 764         test_removed_feature,
 765         test_runner,
 766         then_with,
 767         thread,
 768         thread_local,
 769         tool_attributes,
 770         tool_lints,
 771         trace_macros,
 772         track_caller,
 773         trait_alias,
 774         transmute,
 775         transparent,
 776         transparent_enums,
 777         transparent_unions,
 778         trivial_bounds,
 779         Try,
 780         try_blocks,
 781         try_trait,
 782         tt,
 783         tuple_indexing,
 784         two_phase,
 785         Ty,
 786         ty,
 787         type_alias_impl_trait,
 788         type_id,
 789         type_name,
 790         TyCtxt,
 791         TyKind,
 792         type_alias_enum_variants,
 793         type_ascription,
 794         type_length_limit,
 795         type_macros,
 796         u128,
 797         u16,
 798         u32,
 799         u64,
 800         u8,
 801         unboxed_closures,
 802         unchecked_add,
 803         unchecked_div,
 804         unchecked_mul,
 805         unchecked_rem,
 806         unchecked_shl,
 807         unchecked_shr,
 808         unchecked_sub,
 809         underscore_const_names,
 810         underscore_imports,
 811         underscore_lifetimes,
 812         uniform_paths,
 813         universal_impl_trait,
 814         unmarked_api,
 815         unreachable_code,
 816         unrestricted_attribute_tokens,
 817         unsafe_block_in_unsafe_fn,
 818         unsafe_no_drop_flag,
 819         unsized_locals,
 820         unsized_tuple_coercion,
 821         unstable,
 822         untagged_unions,
 823         unwind,
 824         unwind_attributes,
 825         unwrap_or,
 826         used,
 827         use_extern_macros,
 828         use_nested_groups,
 829         usize,
 830         v1,
 831         val,
 832         var,
 833         vec,
 834         Vec,
 835         version,
 836         vis,
 837         visible_private_types,
 838         volatile,
 839         warn,
 840         wasm_import_module,
 841         wasm_target_feature,
 842         while_let,
 843         windows,
 844         windows_subsystem,
 845         wrapping_add,
 846         wrapping_sub,
 847         wrapping_mul,
 848         Yield,
 849     }
 850 }
 851
 852 #[derive(Copy, Clone, Eq, HashStable_Generic)]
 853 pub struct Ident {
 854     pub name: Symbol,
 855     pub span: Span,
 856 }
 857
 858 impl Ident {
 859     #[inline]
 860     /// Constructs a new identifier from a symbol and a span.
 861     pub const fn new(name: Symbol, span: Span) -> Ident {
 862         Ident { name, span }
 863     }
 864
 865     /// Constructs a new identifier with a dummy span.
 866     #[inline]
 867     pub const fn with_dummy_span(name: Symbol) -> Ident {
 868         Ident::new(name, DUMMY_SP)
 869     }
 870
 871     #[inline]
 872     pub fn invalid() -> Ident {
 873         Ident::with_dummy_span(kw::Invalid)
 874     }
 875
 876     /// Maps a string to an identifier with a dummy span.
 877     pub fn from_str(string: &str) -> Ident {
 878         Ident::with_dummy_span(Symbol::intern(string))
 879     }
 880
 881     /// Maps a string and a span to an identifier.
 882     pub fn from_str_and_span(string: &str, span: Span) -> Ident {
 883         Ident::new(Symbol::intern(string), span)
 884     }
 885
 886     /// Replaces `lo` and `hi` with those from `span`, but keep hygiene context.
 887     pub fn with_span_pos(self, span: Span) -> Ident {
 888         Ident::new(self.name, span.with_ctxt(self.span.ctxt()))
 889     }
 890
 891     pub fn without_first_quote(self) -> Ident {
 892         Ident::new(Symbol::intern(self.as_str().trim_start_matches('\'')), self.span)
 893     }
 894
 895     /// "Normalize" ident for use in comparisons using "item hygiene".
 896     /// Identifiers with same string value become same if they came from the same macro 2.0 macro
 897     /// (e.g., `macro` item, but not `macro_rules` item) and stay different if they came from
 898     /// different macro 2.0 macros.
 899     /// Technically, this operation strips all non-opaque marks from ident's syntactic context.
 900     pub fn normalize_to_macros_2_0(self) -> Ident {
 901         Ident::new(self.name, self.span.normalize_to_macros_2_0())
 902     }
 903
 904     /// "Normalize" ident for use in comparisons using "local variable hygiene".
 905     /// Identifiers with same string value become same if they came from the same non-transparent
 906     /// macro (e.g., `macro` or `macro_rules!` items) and stay different if they came from different
 907     /// non-transparent macros.
 908     /// Technically, this operation strips all transparent marks from ident's syntactic context.
 909     pub fn normalize_to_macro_rules(self) -> Ident {
 910         Ident::new(self.name, self.span.normalize_to_macro_rules())
 911     }
 912
 913     /// Convert the name to a `SymbolStr`. This is a slowish operation because
 914     /// it requires locking the symbol interner.
 915     pub fn as_str(self) -> SymbolStr {
 916         self.name.as_str()
 917     }
 918 }
 919
 920 impl PartialEq for Ident {
 921     fn eq(&self, rhs: &Self) -> bool {
 922         self.name == rhs.name && self.span.ctxt() == rhs.span.ctxt()
 923     }
 924 }
 925
 926 impl Hash for Ident {
 927     fn hash<H: Hasher>(&self, state: &mut H) {
 928         self.name.hash(state);
 929         self.span.ctxt().hash(state);
 930     }
 931 }
 932
 933 impl fmt::Debug for Ident {
 934     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 935         fmt::Display::fmt(self, f)?;
 936         fmt::Debug::fmt(&self.span.ctxt(), f)
 937     }
 938 }
 939
 940 /// This implementation is supposed to be used in error messages, so it's expected to be identical
 941 /// to printing the original identifier token written in source code (`token_to_string`),
 942 /// except that AST identifiers don't keep the rawness flag, so we have to guess it.
 943 impl fmt::Display for Ident {
 944     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 945         fmt::Display::fmt(&IdentPrinter::new(self.name, self.is_raw_guess(), None), f)
 946     }
 947 }
 948
 949 impl UseSpecializedEncodable for Ident {
 950     fn default_encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
 951         s.emit_struct("Ident", 2, |s| {
 952             s.emit_struct_field("name", 0, |s| self.name.encode(s))?;
 953             s.emit_struct_field("span", 1, |s| self.span.encode(s))
 954         })
 955     }
 956 }
 957
 958 impl UseSpecializedDecodable for Ident {
 959     fn default_decode<D: Decoder>(d: &mut D) -> Result<Self, D::Error> {
 960         d.read_struct("Ident", 2, |d| {
 961             Ok(Ident {
 962                 name: d.read_struct_field("name", 0, Decodable::decode)?,
 963                 span: d.read_struct_field("span", 1, Decodable::decode)?,
 964             })
 965         })
 966     }
 967 }
 968
 969 /// This is the most general way to print identifiers.
 970 /// AST pretty-printer is used as a fallback for turning AST structures into token streams for
 971 /// proc macros. Additionally, proc macros may stringify their input and expect it survive the
 972 /// stringification (especially true for proc macro derives written between Rust 1.15 and 1.30).
 973 /// So we need to somehow pretty-print `$crate` in a way preserving at least some of its
 974 /// hygiene data, most importantly name of the crate it refers to.
 975 /// As a result we print `$crate` as `crate` if it refers to the local crate
 976 /// and as `::other_crate_name` if it refers to some other crate.
 977 /// Note, that this is only done if the ident token is printed from inside of AST pretty-pringing,
 978 /// but not otherwise. Pretty-printing is the only way for proc macros to discover token contents,
 979 /// so we should not perform this lossy conversion if the top level call to the pretty-printer was
 980 /// done for a token stream or a single token.
 981 pub struct IdentPrinter {
 982     symbol: Symbol,
 983     is_raw: bool,
 984     /// Span used for retrieving the crate name to which `$crate` refers to,
 985     /// if this field is `None` then the `$crate` conversion doesn't happen.
 986     convert_dollar_crate: Option<Span>,
 987 }
 988
 989 impl IdentPrinter {
 990     /// The most general `IdentPrinter` constructor. Do not use this.
 991     pub fn new(symbol: Symbol, is_raw: bool, convert_dollar_crate: Option<Span>) -> IdentPrinter {
 992         IdentPrinter { symbol, is_raw, convert_dollar_crate }
 993     }
 994
 995     /// This implementation is supposed to be used when printing identifiers
 996     /// as a part of pretty-printing for larger AST pieces.
 997     /// Do not use this either.
 998     pub fn for_ast_ident(ident: Ident, is_raw: bool) -> IdentPrinter {
 999         IdentPrinter::new(ident.name, is_raw, Some(ident.span))
1000     }
1001 }
1002
1003 impl fmt::Display for IdentPrinter {
1004     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1005         if self.is_raw {
1006             f.write_str("r#")?;
1007         } else {
1008             if self.symbol == kw::DollarCrate {
1009                 if let Some(span) = self.convert_dollar_crate {
1010                     let converted = span.ctxt().dollar_crate_name();
1011                     if !converted.is_path_segment_keyword() {
1012                         f.write_str("::")?;
1013                     }
1014                     return fmt::Display::fmt(&converted, f);
1015                 }
1016             }
1017         }
1018         fmt::Display::fmt(&self.symbol, f)
1019     }
1020 }
1021
1022 /// An newtype around `Ident` that calls [Ident::normalize_to_macro_rules] on
1023 /// construction.
1024 // FIXME(matthewj, petrochenkov) Use this more often, add a similar
1025 // `ModernIdent` struct and use that as well.
1026 #[derive(Copy, Clone, Eq, PartialEq, Hash)]
1027 pub struct MacroRulesNormalizedIdent(Ident);
1028
1029 impl MacroRulesNormalizedIdent {
1030     pub fn new(ident: Ident) -> Self {
1031         Self(ident.normalize_to_macro_rules())
1032     }
1033 }
1034
1035 impl fmt::Debug for MacroRulesNormalizedIdent {
1036     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1037         fmt::Debug::fmt(&self.0, f)
1038     }
1039 }
1040
1041 impl fmt::Display for MacroRulesNormalizedIdent {
1042     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1043         fmt::Display::fmt(&self.0, f)
1044     }
1045 }
1046
1047 /// An interned string.
1048 ///
1049 /// Internally, a `Symbol` is implemented as an index, and all operations
1050 /// (including hashing, equality, and ordering) operate on that index. The use
1051 /// of `rustc_index::newtype_index!` means that `Option<Symbol>` only takes up 4 bytes,
1052 /// because `rustc_index::newtype_index!` reserves the last 256 values for tagging purposes.
1053 ///
1054 /// Note that `Symbol` cannot directly be a `rustc_index::newtype_index!` because it
1055 /// implements `fmt::Debug`, `Encodable`, and `Decodable` in special ways.
1056 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
1057 pub struct Symbol(SymbolIndex);
1058
1059 rustc_index::newtype_index! {
1060     pub struct SymbolIndex { .. }
1061 }
1062
1063 impl Symbol {
1064     const fn new(n: u32) -> Self {
1065         Symbol(SymbolIndex::from_u32(n))
1066     }
1067
1068     /// Maps a string to its interned representation.
1069     pub fn intern(string: &str) -> Self {
1070         with_interner(|interner| interner.intern(string))
1071     }
1072
1073     /// Access the symbol's chars. This is a slowish operation because it
1074     /// requires locking the symbol interner.
1075     pub fn with<F: FnOnce(&str) -> R, R>(self, f: F) -> R {
1076         with_interner(|interner| f(interner.get(self)))
1077     }
1078
1079     /// Convert to a `SymbolStr`. This is a slowish operation because it
1080     /// requires locking the symbol interner.
1081     pub fn as_str(self) -> SymbolStr {
1082         with_interner(|interner| unsafe {
1083             SymbolStr { string: std::mem::transmute::<&str, &str>(interner.get(self)) }
1084         })
1085     }
1086
1087     pub fn as_u32(self) -> u32 {
1088         self.0.as_u32()
1089     }
1090
1091     /// This method is supposed to be used in error messages, so it's expected to be
1092     /// identical to printing the original identifier token written in source code
1093     /// (`token_to_string`, `Ident::to_string`), except that symbols don't keep the rawness flag
1094     /// or edition, so we have to guess the rawness using the global edition.
1095     pub fn to_ident_string(self) -> String {
1096         Ident::with_dummy_span(self).to_string()
1097     }
1098 }
1099
1100 impl fmt::Debug for Symbol {
1101     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1102         self.with(|str| fmt::Debug::fmt(&str, f))
1103     }
1104 }
1105
1106 impl fmt::Display for Symbol {
1107     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1108         self.with(|str| fmt::Display::fmt(&str, f))
1109     }
1110 }
1111
1112 impl Encodable for Symbol {
1113     fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
1114         self.with(|string| s.emit_str(string))
1115     }
1116 }
1117
1118 impl Decodable for Symbol {
1119     #[inline]
1120     fn decode<D: Decoder>(d: &mut D) -> Result<Symbol, D::Error> {
1121         Ok(Symbol::intern(&d.read_str()?))
1122     }
1123 }
1124
1125 impl<CTX> HashStable<CTX> for Symbol {
1126     #[inline]
1127     fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
1128         self.as_str().hash_stable(hcx, hasher);
1129     }
1130 }
1131
1132 impl<CTX> ToStableHashKey<CTX> for Symbol {
1133     type KeyType = SymbolStr;
1134
1135     #[inline]
1136     fn to_stable_hash_key(&self, _: &CTX) -> SymbolStr {
1137         self.as_str()
1138     }
1139 }
1140
1141 // The `&'static str`s in this type actually point into the arena.
1142 #[derive(Default)]
1143 pub struct Interner {
1144     arena: DroplessArena,
1145     names: FxHashMap<&'static str, Symbol>,
1146     strings: Vec<&'static str>,
1147 }
1148
1149 impl Interner {
1150     fn prefill(init: &[&'static str]) -> Self {
1151         Interner {
1152             strings: init.into(),
1153             names: init.iter().copied().zip((0..).map(Symbol::new)).collect(),
1154             ..Default::default()
1155         }
1156     }
1157
1158     #[inline]
1159     pub fn intern(&mut self, string: &str) -> Symbol {
1160         if let Some(&name) = self.names.get(string) {
1161             return name;
1162         }
1163
1164         let name = Symbol::new(self.strings.len() as u32);
1165
1166         // `from_utf8_unchecked` is safe since we just allocated a `&str` which is known to be
1167         // UTF-8.
1168         let string: &str =
1169             unsafe { str::from_utf8_unchecked(self.arena.alloc_slice(string.as_bytes())) };
1170         // It is safe to extend the arena allocation to `'static` because we only access
1171         // these while the arena is still alive.
1172         let string: &'static str = unsafe { &*(string as *const str) };
1173         self.strings.push(string);
1174         self.names.insert(string, name);
1175         name
1176     }
1177
1178     // Get the symbol as a string. `Symbol::as_str()` should be used in
1179     // preference to this function.
1180     pub fn get(&self, symbol: Symbol) -> &str {
1181         self.strings[symbol.0.as_usize()]
1182     }
1183 }
1184
1185 // This module has a very short name because it's used a lot.
1186 /// This module contains all the defined keyword `Symbol`s.
1187 ///
1188 /// Given that `kw` is imported, use them like `kw::keyword_name`.
1189 /// For example `kw::Loop` or `kw::Break`.
1190 pub mod kw {
1191     use super::Symbol;
1192     keywords!();
1193 }
1194
1195 // This module has a very short name because it's used a lot.
1196 /// This module contains all the defined non-keyword `Symbol`s.
1197 ///
1198 /// Given that `sym` is imported, use them like `sym::symbol_name`.
1199 /// For example `sym::rustfmt` or `sym::u8`.
1200 #[allow(rustc::default_hash_types)]
1201 pub mod sym {
1202     use super::Symbol;
1203     use std::convert::TryInto;
1204
1205     symbols!();
1206
1207     // Used from a macro in `librustc_feature/accepted.rs`
1208     pub use super::kw::MacroRules as macro_rules;
1209
1210     // Get the symbol for an integer. The first few non-negative integers each
1211     // have a static symbol and therefore are fast.
1212     pub fn integer<N: TryInto<usize> + Copy + ToString>(n: N) -> Symbol {
1213         if let Result::Ok(idx) = n.try_into() {
1214             if let Option::Some(&sym_) = digits_array.get(idx) {
1215                 return sym_;
1216             }
1217         }
1218         Symbol::intern(&n.to_string())
1219     }
1220 }
1221
1222 impl Symbol {
1223     fn is_used_keyword_2018(self) -> bool {
1224         self >= kw::Async && self <= kw::Dyn
1225     }
1226
1227     fn is_unused_keyword_2018(self) -> bool {
1228         self == kw::Try
1229     }
1230
1231     /// Used for sanity checking rustdoc keyword sections.
1232     pub fn is_doc_keyword(self) -> bool {
1233         self <= kw::Union
1234     }
1235
1236     /// A keyword or reserved identifier that can be used as a path segment.
1237     pub fn is_path_segment_keyword(self) -> bool {
1238         self == kw::Super
1239             || self == kw::SelfLower
1240             || self == kw::SelfUpper
1241             || self == kw::Crate
1242             || self == kw::PathRoot
1243             || self == kw::DollarCrate
1244     }
1245
1246     /// Returns `true` if the symbol is `true` or `false`.
1247     pub fn is_bool_lit(self) -> bool {
1248         self == kw::True || self == kw::False
1249     }
1250
1251     /// This symbol can be a raw identifier.
1252     pub fn can_be_raw(self) -> bool {
1253         self != kw::Invalid && self != kw::Underscore && !self.is_path_segment_keyword()
1254     }
1255 }
1256
1257 impl Ident {
1258     // Returns `true` for reserved identifiers used internally for elided lifetimes,
1259     // unnamed method parameters, crate root module, error recovery etc.
1260     pub fn is_special(self) -> bool {
1261         self.name <= kw::Underscore
1262     }
1263
1264     /// Returns `true` if the token is a keyword used in the language.
1265     pub fn is_used_keyword(self) -> bool {
1266         // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
1267         self.name >= kw::As && self.name <= kw::While
1268             || self.name.is_used_keyword_2018() && self.span.rust_2018()
1269     }
1270
1271     /// Returns `true` if the token is a keyword reserved for possible future use.
1272     pub fn is_unused_keyword(self) -> bool {
1273         // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
1274         self.name >= kw::Abstract && self.name <= kw::Yield
1275             || self.name.is_unused_keyword_2018() && self.span.rust_2018()
1276     }
1277
1278     /// Returns `true` if the token is either a special identifier or a keyword.
1279     pub fn is_reserved(self) -> bool {
1280         self.is_special() || self.is_used_keyword() || self.is_unused_keyword()
1281     }
1282
1283     /// A keyword or reserved identifier that can be used as a path segment.
1284     pub fn is_path_segment_keyword(self) -> bool {
1285         self.name.is_path_segment_keyword()
1286     }
1287
1288     /// We see this identifier in a normal identifier position, like variable name or a type.
1289     /// How was it written originally? Did it use the raw form? Let's try to guess.
1290     pub fn is_raw_guess(self) -> bool {
1291         self.name.can_be_raw() && self.is_reserved()
1292     }
1293 }
1294
1295 #[inline]
1296 fn with_interner<T, F: FnOnce(&mut Interner) -> T>(f: F) -> T {
1297     GLOBALS.with(|globals| f(&mut *globals.symbol_interner.lock()))
1298 }
1299
1300 /// An alternative to `Symbol`, useful when the chars within the symbol need to
1301 /// be accessed. It deliberately has limited functionality and should only be
1302 /// used for temporary values.
1303 ///
1304 /// Because the interner outlives any thread which uses this type, we can
1305 /// safely treat `string` which points to interner data, as an immortal string,
1306 /// as long as this type never crosses between threads.
1307 //
1308 // FIXME: ensure that the interner outlives any thread which uses `SymbolStr`,
1309 // by creating a new thread right after constructing the interner.
1310 #[derive(Clone, Eq, PartialOrd, Ord)]
1311 pub struct SymbolStr {
1312     string: &'static str,
1313 }
1314
1315 // This impl allows a `SymbolStr` to be directly equated with a `String` or
1316 // `&str`.
1317 impl<T: std::ops::Deref<Target = str>> std::cmp::PartialEq<T> for SymbolStr {
1318     fn eq(&self, other: &T) -> bool {
1319         self.string == other.deref()
1320     }
1321 }
1322
1323 impl !Send for SymbolStr {}
1324 impl !Sync for SymbolStr {}
1325
1326 /// This impl means that if `ss` is a `SymbolStr`:
1327 /// - `*ss` is a `str`;
1328 /// - `&*ss` is a `&str`;
1329 /// - `&ss as &str` is a `&str`, which means that `&ss` can be passed to a
1330 ///   function expecting a `&str`.
1331 impl std::ops::Deref for SymbolStr {
1332     type Target = str;
1333     #[inline]
1334     fn deref(&self) -> &str {
1335         self.string
1336     }
1337 }
1338
1339 impl fmt::Debug for SymbolStr {
1340     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1341         fmt::Debug::fmt(self.string, f)
1342     }
1343 }
1344
1345 impl fmt::Display for SymbolStr {
1346     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1347         fmt::Display::fmt(self.string, f)
1348     }
1349 }
1350
1351 impl<CTX> HashStable<CTX> for SymbolStr {
1352     #[inline]
1353     fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
1354         self.string.hash_stable(hcx, hasher)
1355     }
1356 }
1357
1358 impl<CTX> ToStableHashKey<CTX> for SymbolStr {
1359     type KeyType = SymbolStr;
1360
1361     #[inline]
1362     fn to_stable_hash_key(&self, _: &CTX) -> SymbolStr {
1363         self.clone()
1364     }
1365 }