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_builtins,
 591         profiler_runtime,
 592         ptr_guaranteed_eq,
 593         ptr_guaranteed_ne,
 594         ptr_offset_from,
 595         pub_restricted,
 596         pure,
 597         pushpop_unsafe,
 598         quad_precision_float,
 599         question_mark,
 600         quote,
 601         Range,
 602         RangeFrom,
 603         RangeFull,
 604         RangeInclusive,
 605         RangeTo,
 606         RangeToInclusive,
 607         raw_dylib,
 608         raw_identifiers,
 609         raw_ref_op,
 610         Rc,
 611         readonly,
 612         Ready,
 613         reason,
 614         recursion_limit,
 615         reexport_test_harness_main,
 616         reflect,
 617         register_attr,
 618         register_tool,
 619         relaxed_adts,
 620         repr,
 621         repr128,
 622         repr_align,
 623         repr_align_enum,
 624         repr_no_niche,
 625         repr_packed,
 626         repr_simd,
 627         repr_transparent,
 628         re_rebalance_coherence,
 629         result,
 630         Result,
 631         Return,
 632         rhs,
 633         riscv_target_feature,
 634         rlib,
 635         rotate_left,
 636         rotate_right,
 637         rt,
 638         rtm_target_feature,
 639         rust,
 640         rust_2015_preview,
 641         rust_2018_preview,
 642         rust_begin_unwind,
 643         rustc,
 644         RustcDecodable,
 645         RustcEncodable,
 646         rustc_allocator,
 647         rustc_allocator_nounwind,
 648         rustc_allow_const_fn_ptr,
 649         rustc_args_required_const,
 650         rustc_attrs,
 651         rustc_builtin_macro,
 652         rustc_clean,
 653         rustc_const_unstable,
 654         rustc_const_stable,
 655         rustc_conversion_suggestion,
 656         rustc_def_path,
 657         rustc_deprecated,
 658         rustc_diagnostic_item,
 659         rustc_diagnostic_macros,
 660         rustc_dirty,
 661         rustc_dummy,
 662         rustc_dump_env_program_clauses,
 663         rustc_dump_program_clauses,
 664         rustc_dump_user_substs,
 665         rustc_error,
 666         rustc_expected_cgu_reuse,
 667         rustc_if_this_changed,
 668         rustc_inherit_overflow_checks,
 669         rustc_layout,
 670         rustc_layout_scalar_valid_range_end,
 671         rustc_layout_scalar_valid_range_start,
 672         rustc_macro_transparency,
 673         rustc_mir,
 674         rustc_nonnull_optimization_guaranteed,
 675         rustc_object_lifetime_default,
 676         rustc_on_unimplemented,
 677         rustc_outlives,
 678         rustc_paren_sugar,
 679         rustc_partition_codegened,
 680         rustc_partition_reused,
 681         rustc_peek,
 682         rustc_peek_definite_init,
 683         rustc_peek_liveness,
 684         rustc_peek_maybe_init,
 685         rustc_peek_maybe_uninit,
 686         rustc_peek_indirectly_mutable,
 687         rustc_private,
 688         rustc_proc_macro_decls,
 689         rustc_promotable,
 690         rustc_regions,
 691         rustc_unsafe_specialization_marker,
 692         rustc_specialization_trait,
 693         rustc_stable,
 694         rustc_std_internal_symbol,
 695         rustc_symbol_name,
 696         rustc_synthetic,
 697         rustc_reservation_impl,
 698         rustc_test_marker,
 699         rustc_then_this_would_need,
 700         rustc_variance,
 701         rustfmt,
 702         rust_eh_personality,
 703         rust_oom,
 704         rvalue_static_promotion,
 705         sanitize,
 706         sanitizer_runtime,
 707         saturating_add,
 708         saturating_sub,
 709         _Self,
 710         self_in_typedefs,
 711         self_struct_ctor,
 712         send_trait,
 713         should_panic,
 714         simd,
 715         simd_extract,
 716         simd_ffi,
 717         simd_insert,
 718         since,
 719         size,
 720         size_of,
 721         slice_patterns,
 722         slicing_syntax,
 723         soft,
 724         Some,
 725         specialization,
 726         speed,
 727         sse4a_target_feature,
 728         stable,
 729         staged_api,
 730         start,
 731         static_in_const,
 732         staticlib,
 733         static_nobundle,
 734         static_recursion,
 735         std,
 736         std_inject,
 737         str,
 738         stringify,
 739         stmt,
 740         stmt_expr_attributes,
 741         stop_after_dataflow,
 742         struct_field_attributes,
 743         struct_inherit,
 744         structural_match,
 745         struct_variant,
 746         sty,
 747         sub_with_overflow,
 748         suggestion,
 749         sym,
 750         sync_trait,
 751         target_feature,
 752         target_feature_11,
 753         target_has_atomic,
 754         target_has_atomic_load_store,
 755         target_thread_local,
 756         task,
 757         _task_context,
 758         tbm_target_feature,
 759         termination_trait,
 760         termination_trait_test,
 761         test,
 762         test_2018_feature,
 763         test_accepted_feature,
 764         test_case,
 765         test_removed_feature,
 766         test_runner,
 767         then_with,
 768         thread,
 769         thread_local,
 770         tool_attributes,
 771         tool_lints,
 772         trace_macros,
 773         track_caller,
 774         trait_alias,
 775         transmute,
 776         transparent,
 777         transparent_enums,
 778         transparent_unions,
 779         trivial_bounds,
 780         Try,
 781         try_blocks,
 782         try_trait,
 783         tt,
 784         tuple_indexing,
 785         two_phase,
 786         Ty,
 787         ty,
 788         type_alias_impl_trait,
 789         type_id,
 790         type_name,
 791         TyCtxt,
 792         TyKind,
 793         type_alias_enum_variants,
 794         type_ascription,
 795         type_length_limit,
 796         type_macros,
 797         u128,
 798         u16,
 799         u32,
 800         u64,
 801         u8,
 802         unboxed_closures,
 803         unchecked_add,
 804         unchecked_div,
 805         unchecked_mul,
 806         unchecked_rem,
 807         unchecked_shl,
 808         unchecked_shr,
 809         unchecked_sub,
 810         underscore_const_names,
 811         underscore_imports,
 812         underscore_lifetimes,
 813         uniform_paths,
 814         universal_impl_trait,
 815         unmarked_api,
 816         unreachable_code,
 817         unrestricted_attribute_tokens,
 818         unsafe_block_in_unsafe_fn,
 819         unsafe_no_drop_flag,
 820         unsized_locals,
 821         unsized_tuple_coercion,
 822         unstable,
 823         untagged_unions,
 824         unwind,
 825         unwind_attributes,
 826         unwrap_or,
 827         used,
 828         use_extern_macros,
 829         use_nested_groups,
 830         usize,
 831         v1,
 832         val,
 833         var,
 834         vec,
 835         Vec,
 836         version,
 837         vis,
 838         visible_private_types,
 839         volatile,
 840         warn,
 841         wasm_import_module,
 842         wasm_target_feature,
 843         while_let,
 844         windows,
 845         windows_subsystem,
 846         wrapping_add,
 847         wrapping_sub,
 848         wrapping_mul,
 849         Yield,
 850     }
 851 }
 852
 853 #[derive(Copy, Clone, Eq, HashStable_Generic)]
 854 pub struct Ident {
 855     pub name: Symbol,
 856     pub span: Span,
 857 }
 858
 859 impl Ident {
 860     #[inline]
 861     /// Constructs a new identifier from a symbol and a span.
 862     pub const fn new(name: Symbol, span: Span) -> Ident {
 863         Ident { name, span }
 864     }
 865
 866     /// Constructs a new identifier with a dummy span.
 867     #[inline]
 868     pub const fn with_dummy_span(name: Symbol) -> Ident {
 869         Ident::new(name, DUMMY_SP)
 870     }
 871
 872     #[inline]
 873     pub fn invalid() -> Ident {
 874         Ident::with_dummy_span(kw::Invalid)
 875     }
 876
 877     /// Maps a string to an identifier with a dummy span.
 878     pub fn from_str(string: &str) -> Ident {
 879         Ident::with_dummy_span(Symbol::intern(string))
 880     }
 881
 882     /// Maps a string and a span to an identifier.
 883     pub fn from_str_and_span(string: &str, span: Span) -> Ident {
 884         Ident::new(Symbol::intern(string), span)
 885     }
 886
 887     /// Replaces `lo` and `hi` with those from `span`, but keep hygiene context.
 888     pub fn with_span_pos(self, span: Span) -> Ident {
 889         Ident::new(self.name, span.with_ctxt(self.span.ctxt()))
 890     }
 891
 892     pub fn without_first_quote(self) -> Ident {
 893         Ident::new(Symbol::intern(self.as_str().trim_start_matches('\'')), self.span)
 894     }
 895
 896     /// "Normalize" ident for use in comparisons using "item hygiene".
 897     /// Identifiers with same string value become same if they came from the same macro 2.0 macro
 898     /// (e.g., `macro` item, but not `macro_rules` item) and stay different if they came from
 899     /// different macro 2.0 macros.
 900     /// Technically, this operation strips all non-opaque marks from ident's syntactic context.
 901     pub fn normalize_to_macros_2_0(self) -> Ident {
 902         Ident::new(self.name, self.span.normalize_to_macros_2_0())
 903     }
 904
 905     /// "Normalize" ident for use in comparisons using "local variable hygiene".
 906     /// Identifiers with same string value become same if they came from the same non-transparent
 907     /// macro (e.g., `macro` or `macro_rules!` items) and stay different if they came from different
 908     /// non-transparent macros.
 909     /// Technically, this operation strips all transparent marks from ident's syntactic context.
 910     pub fn normalize_to_macro_rules(self) -> Ident {
 911         Ident::new(self.name, self.span.normalize_to_macro_rules())
 912     }
 913
 914     /// Convert the name to a `SymbolStr`. This is a slowish operation because
 915     /// it requires locking the symbol interner.
 916     pub fn as_str(self) -> SymbolStr {
 917         self.name.as_str()
 918     }
 919 }
 920
 921 impl PartialEq for Ident {
 922     fn eq(&self, rhs: &Self) -> bool {
 923         self.name == rhs.name && self.span.ctxt() == rhs.span.ctxt()
 924     }
 925 }
 926
 927 impl Hash for Ident {
 928     fn hash<H: Hasher>(&self, state: &mut H) {
 929         self.name.hash(state);
 930         self.span.ctxt().hash(state);
 931     }
 932 }
 933
 934 impl fmt::Debug for Ident {
 935     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 936         fmt::Display::fmt(self, f)?;
 937         fmt::Debug::fmt(&self.span.ctxt(), f)
 938     }
 939 }
 940
 941 /// This implementation is supposed to be used in error messages, so it's expected to be identical
 942 /// to printing the original identifier token written in source code (`token_to_string`),
 943 /// except that AST identifiers don't keep the rawness flag, so we have to guess it.
 944 impl fmt::Display for Ident {
 945     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 946         fmt::Display::fmt(&IdentPrinter::new(self.name, self.is_raw_guess(), None), f)
 947     }
 948 }
 949
 950 impl UseSpecializedEncodable for Ident {
 951     fn default_encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
 952         s.emit_struct("Ident", 2, |s| {
 953             s.emit_struct_field("name", 0, |s| self.name.encode(s))?;
 954             s.emit_struct_field("span", 1, |s| self.span.encode(s))
 955         })
 956     }
 957 }
 958
 959 impl UseSpecializedDecodable for Ident {
 960     fn default_decode<D: Decoder>(d: &mut D) -> Result<Self, D::Error> {
 961         d.read_struct("Ident", 2, |d| {
 962             Ok(Ident {
 963                 name: d.read_struct_field("name", 0, Decodable::decode)?,
 964                 span: d.read_struct_field("span", 1, Decodable::decode)?,
 965             })
 966         })
 967     }
 968 }
 969
 970 /// This is the most general way to print identifiers.
 971 /// AST pretty-printer is used as a fallback for turning AST structures into token streams for
 972 /// proc macros. Additionally, proc macros may stringify their input and expect it survive the
 973 /// stringification (especially true for proc macro derives written between Rust 1.15 and 1.30).
 974 /// So we need to somehow pretty-print `$crate` in a way preserving at least some of its
 975 /// hygiene data, most importantly name of the crate it refers to.
 976 /// As a result we print `$crate` as `crate` if it refers to the local crate
 977 /// and as `::other_crate_name` if it refers to some other crate.
 978 /// Note, that this is only done if the ident token is printed from inside of AST pretty-pringing,
 979 /// but not otherwise. Pretty-printing is the only way for proc macros to discover token contents,
 980 /// so we should not perform this lossy conversion if the top level call to the pretty-printer was
 981 /// done for a token stream or a single token.
 982 pub struct IdentPrinter {
 983     symbol: Symbol,
 984     is_raw: bool,
 985     /// Span used for retrieving the crate name to which `$crate` refers to,
 986     /// if this field is `None` then the `$crate` conversion doesn't happen.
 987     convert_dollar_crate: Option<Span>,
 988 }
 989
 990 impl IdentPrinter {
 991     /// The most general `IdentPrinter` constructor. Do not use this.
 992     pub fn new(symbol: Symbol, is_raw: bool, convert_dollar_crate: Option<Span>) -> IdentPrinter {
 993         IdentPrinter { symbol, is_raw, convert_dollar_crate }
 994     }
 995
 996     /// This implementation is supposed to be used when printing identifiers
 997     /// as a part of pretty-printing for larger AST pieces.
 998     /// Do not use this either.
 999     pub fn for_ast_ident(ident: Ident, is_raw: bool) -> IdentPrinter {
1000         IdentPrinter::new(ident.name, is_raw, Some(ident.span))
1001     }
1002 }
1003
1004 impl fmt::Display for IdentPrinter {
1005     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1006         if self.is_raw {
1007             f.write_str("r#")?;
1008         } else {
1009             if self.symbol == kw::DollarCrate {
1010                 if let Some(span) = self.convert_dollar_crate {
1011                     let converted = span.ctxt().dollar_crate_name();
1012                     if !converted.is_path_segment_keyword() {
1013                         f.write_str("::")?;
1014                     }
1015                     return fmt::Display::fmt(&converted, f);
1016                 }
1017             }
1018         }
1019         fmt::Display::fmt(&self.symbol, f)
1020     }
1021 }
1022
1023 /// An newtype around `Ident` that calls [Ident::normalize_to_macro_rules] on
1024 /// construction.
1025 // FIXME(matthewj, petrochenkov) Use this more often, add a similar
1026 // `ModernIdent` struct and use that as well.
1027 #[derive(Copy, Clone, Eq, PartialEq, Hash)]
1028 pub struct MacroRulesNormalizedIdent(Ident);
1029
1030 impl MacroRulesNormalizedIdent {
1031     pub fn new(ident: Ident) -> Self {
1032         Self(ident.normalize_to_macro_rules())
1033     }
1034 }
1035
1036 impl fmt::Debug for MacroRulesNormalizedIdent {
1037     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1038         fmt::Debug::fmt(&self.0, f)
1039     }
1040 }
1041
1042 impl fmt::Display for MacroRulesNormalizedIdent {
1043     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1044         fmt::Display::fmt(&self.0, f)
1045     }
1046 }
1047
1048 /// An interned string.
1049 ///
1050 /// Internally, a `Symbol` is implemented as an index, and all operations
1051 /// (including hashing, equality, and ordering) operate on that index. The use
1052 /// of `rustc_index::newtype_index!` means that `Option<Symbol>` only takes up 4 bytes,
1053 /// because `rustc_index::newtype_index!` reserves the last 256 values for tagging purposes.
1054 ///
1055 /// Note that `Symbol` cannot directly be a `rustc_index::newtype_index!` because it
1056 /// implements `fmt::Debug`, `Encodable`, and `Decodable` in special ways.
1057 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
1058 pub struct Symbol(SymbolIndex);
1059
1060 rustc_index::newtype_index! {
1061     pub struct SymbolIndex { .. }
1062 }
1063
1064 impl Symbol {
1065     const fn new(n: u32) -> Self {
1066         Symbol(SymbolIndex::from_u32(n))
1067     }
1068
1069     /// Maps a string to its interned representation.
1070     pub fn intern(string: &str) -> Self {
1071         with_interner(|interner| interner.intern(string))
1072     }
1073
1074     /// Access the symbol's chars. This is a slowish operation because it
1075     /// requires locking the symbol interner.
1076     pub fn with<F: FnOnce(&str) -> R, R>(self, f: F) -> R {
1077         with_interner(|interner| f(interner.get(self)))
1078     }
1079
1080     /// Convert to a `SymbolStr`. This is a slowish operation because it
1081     /// requires locking the symbol interner.
1082     pub fn as_str(self) -> SymbolStr {
1083         with_interner(|interner| unsafe {
1084             SymbolStr { string: std::mem::transmute::<&str, &str>(interner.get(self)) }
1085         })
1086     }
1087
1088     pub fn as_u32(self) -> u32 {
1089         self.0.as_u32()
1090     }
1091
1092     /// This method is supposed to be used in error messages, so it's expected to be
1093     /// identical to printing the original identifier token written in source code
1094     /// (`token_to_string`, `Ident::to_string`), except that symbols don't keep the rawness flag
1095     /// or edition, so we have to guess the rawness using the global edition.
1096     pub fn to_ident_string(self) -> String {
1097         Ident::with_dummy_span(self).to_string()
1098     }
1099 }
1100
1101 impl fmt::Debug for Symbol {
1102     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1103         self.with(|str| fmt::Debug::fmt(&str, f))
1104     }
1105 }
1106
1107 impl fmt::Display for Symbol {
1108     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1109         self.with(|str| fmt::Display::fmt(&str, f))
1110     }
1111 }
1112
1113 impl Encodable for Symbol {
1114     fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
1115         self.with(|string| s.emit_str(string))
1116     }
1117 }
1118
1119 impl Decodable for Symbol {
1120     #[inline]
1121     fn decode<D: Decoder>(d: &mut D) -> Result<Symbol, D::Error> {
1122         Ok(Symbol::intern(&d.read_str()?))
1123     }
1124 }
1125
1126 impl<CTX> HashStable<CTX> for Symbol {
1127     #[inline]
1128     fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
1129         self.as_str().hash_stable(hcx, hasher);
1130     }
1131 }
1132
1133 impl<CTX> ToStableHashKey<CTX> for Symbol {
1134     type KeyType = SymbolStr;
1135
1136     #[inline]
1137     fn to_stable_hash_key(&self, _: &CTX) -> SymbolStr {
1138         self.as_str()
1139     }
1140 }
1141
1142 // The `&'static str`s in this type actually point into the arena.
1143 #[derive(Default)]
1144 pub struct Interner {
1145     arena: DroplessArena,
1146     names: FxHashMap<&'static str, Symbol>,
1147     strings: Vec<&'static str>,
1148 }
1149
1150 impl Interner {
1151     fn prefill(init: &[&'static str]) -> Self {
1152         Interner {
1153             strings: init.into(),
1154             names: init.iter().copied().zip((0..).map(Symbol::new)).collect(),
1155             ..Default::default()
1156         }
1157     }
1158
1159     #[inline]
1160     pub fn intern(&mut self, string: &str) -> Symbol {
1161         if let Some(&name) = self.names.get(string) {
1162             return name;
1163         }
1164
1165         let name = Symbol::new(self.strings.len() as u32);
1166
1167         // `from_utf8_unchecked` is safe since we just allocated a `&str` which is known to be
1168         // UTF-8.
1169         let string: &str =
1170             unsafe { str::from_utf8_unchecked(self.arena.alloc_slice(string.as_bytes())) };
1171         // It is safe to extend the arena allocation to `'static` because we only access
1172         // these while the arena is still alive.
1173         let string: &'static str = unsafe { &*(string as *const str) };
1174         self.strings.push(string);
1175         self.names.insert(string, name);
1176         name
1177     }
1178
1179     // Get the symbol as a string. `Symbol::as_str()` should be used in
1180     // preference to this function.
1181     pub fn get(&self, symbol: Symbol) -> &str {
1182         self.strings[symbol.0.as_usize()]
1183     }
1184 }
1185
1186 // This module has a very short name because it's used a lot.
1187 /// This module contains all the defined keyword `Symbol`s.
1188 ///
1189 /// Given that `kw` is imported, use them like `kw::keyword_name`.
1190 /// For example `kw::Loop` or `kw::Break`.
1191 pub mod kw {
1192     use super::Symbol;
1193     keywords!();
1194 }
1195
1196 // This module has a very short name because it's used a lot.
1197 /// This module contains all the defined non-keyword `Symbol`s.
1198 ///
1199 /// Given that `sym` is imported, use them like `sym::symbol_name`.
1200 /// For example `sym::rustfmt` or `sym::u8`.
1201 #[allow(rustc::default_hash_types)]
1202 pub mod sym {
1203     use super::Symbol;
1204     use std::convert::TryInto;
1205
1206     symbols!();
1207
1208     // Used from a macro in `librustc_feature/accepted.rs`
1209     pub use super::kw::MacroRules as macro_rules;
1210
1211     // Get the symbol for an integer. The first few non-negative integers each
1212     // have a static symbol and therefore are fast.
1213     pub fn integer<N: TryInto<usize> + Copy + ToString>(n: N) -> Symbol {
1214         if let Result::Ok(idx) = n.try_into() {
1215             if let Option::Some(&sym_) = digits_array.get(idx) {
1216                 return sym_;
1217             }
1218         }
1219         Symbol::intern(&n.to_string())
1220     }
1221 }
1222
1223 impl Symbol {
1224     fn is_used_keyword_2018(self) -> bool {
1225         self >= kw::Async && self <= kw::Dyn
1226     }
1227
1228     fn is_unused_keyword_2018(self) -> bool {
1229         self == kw::Try
1230     }
1231
1232     /// Used for sanity checking rustdoc keyword sections.
1233     pub fn is_doc_keyword(self) -> bool {
1234         self <= kw::Union
1235     }
1236
1237     /// A keyword or reserved identifier that can be used as a path segment.
1238     pub fn is_path_segment_keyword(self) -> bool {
1239         self == kw::Super
1240             || self == kw::SelfLower
1241             || self == kw::SelfUpper
1242             || self == kw::Crate
1243             || self == kw::PathRoot
1244             || self == kw::DollarCrate
1245     }
1246
1247     /// Returns `true` if the symbol is `true` or `false`.
1248     pub fn is_bool_lit(self) -> bool {
1249         self == kw::True || self == kw::False
1250     }
1251
1252     /// This symbol can be a raw identifier.
1253     pub fn can_be_raw(self) -> bool {
1254         self != kw::Invalid && self != kw::Underscore && !self.is_path_segment_keyword()
1255     }
1256 }
1257
1258 impl Ident {
1259     // Returns `true` for reserved identifiers used internally for elided lifetimes,
1260     // unnamed method parameters, crate root module, error recovery etc.
1261     pub fn is_special(self) -> bool {
1262         self.name <= kw::Underscore
1263     }
1264
1265     /// Returns `true` if the token is a keyword used in the language.
1266     pub fn is_used_keyword(self) -> bool {
1267         // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
1268         self.name >= kw::As && self.name <= kw::While
1269             || self.name.is_used_keyword_2018() && self.span.rust_2018()
1270     }
1271
1272     /// Returns `true` if the token is a keyword reserved for possible future use.
1273     pub fn is_unused_keyword(self) -> bool {
1274         // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
1275         self.name >= kw::Abstract && self.name <= kw::Yield
1276             || self.name.is_unused_keyword_2018() && self.span.rust_2018()
1277     }
1278
1279     /// Returns `true` if the token is either a special identifier or a keyword.
1280     pub fn is_reserved(self) -> bool {
1281         self.is_special() || self.is_used_keyword() || self.is_unused_keyword()
1282     }
1283
1284     /// A keyword or reserved identifier that can be used as a path segment.
1285     pub fn is_path_segment_keyword(self) -> bool {
1286         self.name.is_path_segment_keyword()
1287     }
1288
1289     /// We see this identifier in a normal identifier position, like variable name or a type.
1290     /// How was it written originally? Did it use the raw form? Let's try to guess.
1291     pub fn is_raw_guess(self) -> bool {
1292         self.name.can_be_raw() && self.is_reserved()
1293     }
1294 }
1295
1296 #[inline]
1297 fn with_interner<T, F: FnOnce(&mut Interner) -> T>(f: F) -> T {
1298     GLOBALS.with(|globals| f(&mut *globals.symbol_interner.lock()))
1299 }
1300
1301 /// An alternative to `Symbol`, useful when the chars within the symbol need to
1302 /// be accessed. It deliberately has limited functionality and should only be
1303 /// used for temporary values.
1304 ///
1305 /// Because the interner outlives any thread which uses this type, we can
1306 /// safely treat `string` which points to interner data, as an immortal string,
1307 /// as long as this type never crosses between threads.
1308 //
1309 // FIXME: ensure that the interner outlives any thread which uses `SymbolStr`,
1310 // by creating a new thread right after constructing the interner.
1311 #[derive(Clone, Eq, PartialOrd, Ord)]
1312 pub struct SymbolStr {
1313     string: &'static str,
1314 }
1315
1316 // This impl allows a `SymbolStr` to be directly equated with a `String` or
1317 // `&str`.
1318 impl<T: std::ops::Deref<Target = str>> std::cmp::PartialEq<T> for SymbolStr {
1319     fn eq(&self, other: &T) -> bool {
1320         self.string == other.deref()
1321     }
1322 }
1323
1324 impl !Send for SymbolStr {}
1325 impl !Sync for SymbolStr {}
1326
1327 /// This impl means that if `ss` is a `SymbolStr`:
1328 /// - `*ss` is a `str`;
1329 /// - `&*ss` is a `&str`;
1330 /// - `&ss as &str` is a `&str`, which means that `&ss` can be passed to a
1331 ///   function expecting a `&str`.
1332 impl std::ops::Deref for SymbolStr {
1333     type Target = str;
1334     #[inline]
1335     fn deref(&self) -> &str {
1336         self.string
1337     }
1338 }
1339
1340 impl fmt::Debug for SymbolStr {
1341     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1342         fmt::Debug::fmt(self.string, f)
1343     }
1344 }
1345
1346 impl fmt::Display for SymbolStr {
1347     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1348         fmt::Display::fmt(self.string, f)
1349     }
1350 }
1351
1352 impl<CTX> HashStable<CTX> for SymbolStr {
1353     #[inline]
1354     fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
1355         self.string.hash_stable(hcx, hasher)
1356     }
1357 }
1358
1359 impl<CTX> ToStableHashKey<CTX> for SymbolStr {
1360     type KeyType = SymbolStr;
1361
1362     #[inline]
1363     fn to_stable_hash_key(&self, _: &CTX) -> SymbolStr {
1364         self.clone()
1365     }
1366 }