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 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         Raw:                "raw",
 101         Union:              "union",
 102     }
 103
 104     // Symbols that can be referred to with rustc_span::sym::*. The symbol is
 105     // the stringified identifier unless otherwise specified (e.g.
 106     // `proc_dash_macro` represents "proc-macro").
 107     //
 108     // As well as the symbols listed, there are symbols for the the strings
 109     // "0", "1", ..., "9", which are accessible via `sym::integer`.
 110     Symbols {
 111         aarch64_target_feature,
 112         abi,
 113         abi_amdgpu_kernel,
 114         abi_efiapi,
 115         abi_msp430_interrupt,
 116         abi_ptx,
 117         abi_sysv64,
 118         abi_thiscall,
 119         abi_unadjusted,
 120         abi_vectorcall,
 121         abi_x86_interrupt,
 122         aborts,
 123         address,
 124         add_with_overflow,
 125         advanced_slice_patterns,
 126         adx_target_feature,
 127         alias,
 128         align,
 129         alignstack,
 130         all,
 131         allocator,
 132         allocator_internals,
 133         alloc_error_handler,
 134         allow,
 135         allowed,
 136         allow_fail,
 137         allow_internal_unsafe,
 138         allow_internal_unstable,
 139         allow_internal_unstable_backcompat_hack,
 140         always,
 141         and,
 142         any,
 143         arbitrary_enum_discriminant,
 144         arbitrary_self_types,
 145         Arguments,
 146         ArgumentV1,
 147         arm_target_feature,
 148         asm,
 149         assert,
 150         associated_consts,
 151         associated_type_bounds,
 152         associated_type_defaults,
 153         associated_types,
 154         assume_init,
 155         async_await,
 156         async_closure,
 157         attr,
 158         attributes,
 159         attr_literals,
 160         augmented_assignments,
 161         automatically_derived,
 162         avx512_target_feature,
 163         await_macro,
 164         begin_panic,
 165         bench,
 166         bin,
 167         bind_by_move_pattern_guards,
 168         bindings_after_at,
 169         block,
 170         bool,
 171         borrowck_graphviz_format,
 172         borrowck_graphviz_postflow,
 173         borrowck_graphviz_preflow,
 174         box_patterns,
 175         box_syntax,
 176         braced_empty_structs,
 177         bswap,
 178         bitreverse,
 179         C,
 180         caller_location,
 181         cdylib,
 182         cfg,
 183         cfg_attr,
 184         cfg_attr_multi,
 185         cfg_doctest,
 186         cfg_sanitize,
 187         cfg_target_feature,
 188         cfg_target_has_atomic,
 189         cfg_target_thread_local,
 190         cfg_target_vendor,
 191         char,
 192         clippy,
 193         clone,
 194         Clone,
 195         clone_closures,
 196         clone_from,
 197         closure_to_fn_coercion,
 198         cmp,
 199         cmpxchg16b_target_feature,
 200         cold,
 201         column,
 202         compile_error,
 203         compiler_builtins,
 204         concat,
 205         concat_idents,
 206         conservative_impl_trait,
 207         console,
 208         const_compare_raw_pointers,
 209         const_constructor,
 210         const_extern_fn,
 211         const_fn,
 212         const_fn_union,
 213         const_generics,
 214         const_if_match,
 215         const_indexing,
 216         const_in_array_repeat_expressions,
 217         const_let,
 218         const_loop,
 219         const_mut_refs,
 220         const_panic,
 221         const_raw_ptr_deref,
 222         const_raw_ptr_to_usize_cast,
 223         const_transmute,
 224         const_trait_bound_opt_out,
 225         const_trait_impl,
 226         contents,
 227         context,
 228         convert,
 229         Copy,
 230         copy_closures,
 231         core,
 232         core_intrinsics,
 233         crate_id,
 234         crate_in_paths,
 235         crate_local,
 236         crate_name,
 237         crate_type,
 238         crate_visibility_modifier,
 239         ctpop,
 240         cttz,
 241         cttz_nonzero,
 242         ctlz,
 243         ctlz_nonzero,
 244         custom_attribute,
 245         custom_derive,
 246         custom_inner_attributes,
 247         custom_test_frameworks,
 248         c_variadic,
 249         debug_trait,
 250         declare_lint_pass,
 251         decl_macro,
 252         Debug,
 253         Decodable,
 254         Default,
 255         default_lib_allocator,
 256         default_type_parameter_fallback,
 257         default_type_params,
 258         delay_span_bug_from_inside_query,
 259         deny,
 260         deprecated,
 261         deref,
 262         deref_mut,
 263         derive,
 264         diagnostic,
 265         direct,
 266         doc,
 267         doc_alias,
 268         doc_cfg,
 269         doc_keyword,
 270         doc_masked,
 271         doc_spotlight,
 272         doctest,
 273         document_private_items,
 274         dotdoteq_in_patterns,
 275         dotdot_in_tuple_patterns,
 276         double_braced_crate: "{{crate}}",
 277         double_braced_impl: "{{impl}}",
 278         double_braced_misc: "{{misc}}",
 279         double_braced_closure: "{{closure}}",
 280         double_braced_constructor: "{{constructor}}",
 281         double_braced_constant: "{{constant}}",
 282         double_braced_opaque: "{{opaque}}",
 283         dropck_eyepatch,
 284         dropck_parametricity,
 285         drop_types_in_const,
 286         dylib,
 287         dyn_trait,
 288         eh_personality,
 289         eh_unwind_resume,
 290         enable,
 291         Encodable,
 292         env,
 293         eq,
 294         err,
 295         Err,
 296         Eq,
 297         Equal,
 298         enclosing_scope,
 299         except,
 300         exclusive_range_pattern,
 301         exhaustive_integer_patterns,
 302         exhaustive_patterns,
 303         existential_type,
 304         expected,
 305         export_name,
 306         expr,
 307         extern_absolute_paths,
 308         external_doc,
 309         extern_crate_item_prelude,
 310         extern_crate_self,
 311         extern_in_paths,
 312         extern_prelude,
 313         extern_types,
 314         f16c_target_feature,
 315         f32,
 316         f64,
 317         feature,
 318         ffi_returns_twice,
 319         field,
 320         field_init_shorthand,
 321         file,
 322         fmt,
 323         fmt_internals,
 324         fn_must_use,
 325         forbid,
 326         format_args,
 327         format_args_nl,
 328         from,
 329         From,
 330         from_desugaring,
 331         from_error,
 332         from_generator,
 333         from_method,
 334         from_ok,
 335         from_usize,
 336         fundamental,
 337         future,
 338         Future,
 339         FxHashSet,
 340         FxHashMap,
 341         gen_future,
 342         gen_kill,
 343         generators,
 344         generic_associated_types,
 345         generic_param_attrs,
 346         global_allocator,
 347         global_asm,
 348         globs,
 349         half_open_range_patterns,
 350         hash,
 351         Hash,
 352         HashSet,
 353         HashMap,
 354         hexagon_target_feature,
 355         hidden,
 356         homogeneous_aggregate,
 357         html_favicon_url,
 358         html_logo_url,
 359         html_no_source,
 360         html_playground_url,
 361         html_root_url,
 362         i128,
 363         i128_type,
 364         i16,
 365         i32,
 366         i64,
 367         i8,
 368         ident,
 369         if_let,
 370         if_while_or_patterns,
 371         ignore,
 372         impl_header_lifetime_elision,
 373         impl_lint_pass,
 374         impl_trait_in_bindings,
 375         import_shadowing,
 376         index,
 377         index_mut,
 378         in_band_lifetimes,
 379         include,
 380         include_bytes,
 381         include_str,
 382         inclusive_range_syntax,
 383         infer_outlives_requirements,
 384         infer_static_outlives_requirements,
 385         inline,
 386         intel,
 387         into_iter,
 388         IntoIterator,
 389         into_result,
 390         intrinsics,
 391         irrefutable_let_patterns,
 392         isize,
 393         issue,
 394         issue_5723_bootstrap,
 395         issue_tracker_base_url,
 396         item,
 397         item_context: "ItemContext",
 398         item_like_imports,
 399         iter,
 400         Iterator,
 401         keyword,
 402         kind,
 403         label,
 404         label_break_value,
 405         lang,
 406         lang_items,
 407         let_chains,
 408         lhs,
 409         lib,
 410         lifetime,
 411         line,
 412         link,
 413         linkage,
 414         link_args,
 415         link_cfg,
 416         link_llvm_intrinsics,
 417         link_name,
 418         link_ordinal,
 419         link_section,
 420         LintPass,
 421         lint_reasons,
 422         literal,
 423         local_inner_macros,
 424         log_syntax,
 425         loop_break_value,
 426         macro_at_most_once_rep,
 427         macro_escape,
 428         macro_export,
 429         macro_lifetime_matcher,
 430         macro_literal_matcher,
 431         macro_reexport,
 432         macro_rules,
 433         macros_in_extern,
 434         macro_use,
 435         macro_vis_matcher,
 436         main,
 437         managed_boxes,
 438         marker,
 439         marker_trait_attr,
 440         masked,
 441         match_beginning_vert,
 442         match_default_bindings,
 443         may_dangle,
 444         maybe_uninit_uninit,
 445         maybe_uninit_zeroed,
 446         mem_uninitialized,
 447         mem_zeroed,
 448         member_constraints,
 449         memory,
 450         message,
 451         meta,
 452         min_align_of,
 453         min_const_fn,
 454         min_const_unsafe_fn,
 455         mips_target_feature,
 456         mmx_target_feature,
 457         module,
 458         module_path,
 459         more_struct_aliases,
 460         move_val_init,
 461         movbe_target_feature,
 462         mul_with_overflow,
 463         must_use,
 464         naked,
 465         naked_functions,
 466         name,
 467         needs_allocator,
 468         needs_drop,
 469         needs_panic_runtime,
 470         negate_unsigned,
 471         never,
 472         never_type,
 473         never_type_fallback,
 474         new,
 475         next,
 476         __next,
 477         nll,
 478         no_builtins,
 479         no_core,
 480         no_crate_inject,
 481         no_debug,
 482         no_default_passes,
 483         no_implicit_prelude,
 484         no_inline,
 485         no_link,
 486         no_main,
 487         no_mangle,
 488         non_ascii_idents,
 489         None,
 490         non_exhaustive,
 491         non_modrs_mods,
 492         no_sanitize,
 493         no_stack_check,
 494         no_start,
 495         no_std,
 496         not,
 497         note,
 498         object_safe_for_dispatch,
 499         Ok,
 500         omit_gdb_pretty_printer_section,
 501         on,
 502         on_unimplemented,
 503         oom,
 504         ops,
 505         optimize,
 506         optimize_attribute,
 507         optin_builtin_traits,
 508         option,
 509         Option,
 510         option_env,
 511         opt_out_copy,
 512         or,
 513         or_patterns,
 514         Ord,
 515         Ordering,
 516         Output,
 517         overlapping_marker_traits,
 518         packed,
 519         panic,
 520         panic_handler,
 521         panic_impl,
 522         panic_implementation,
 523         panic_runtime,
 524         parent_trait,
 525         partial_cmp,
 526         param_attrs,
 527         PartialEq,
 528         PartialOrd,
 529         passes,
 530         pat,
 531         path,
 532         pattern_parentheses,
 533         Pending,
 534         pin,
 535         Pin,
 536         pinned,
 537         platform_intrinsics,
 538         plugin,
 539         plugin_registrar,
 540         plugins,
 541         Poll,
 542         poll_with_tls_context,
 543         powerpc_target_feature,
 544         precise_pointer_size_matching,
 545         pref_align_of,
 546         prelude,
 547         prelude_import,
 548         primitive,
 549         proc_dash_macro: "proc-macro",
 550         proc_macro,
 551         proc_macro_attribute,
 552         proc_macro_def_site,
 553         proc_macro_derive,
 554         proc_macro_expr,
 555         proc_macro_gen,
 556         proc_macro_hygiene,
 557         proc_macro_internals,
 558         proc_macro_mod,
 559         proc_macro_non_items,
 560         proc_macro_path_invoc,
 561         profiler_runtime,
 562         ptr_offset_from,
 563         pub_restricted,
 564         pushpop_unsafe,
 565         quad_precision_float,
 566         question_mark,
 567         quote,
 568         Range,
 569         RangeFrom,
 570         RangeFull,
 571         RangeInclusive,
 572         RangeTo,
 573         RangeToInclusive,
 574         raw_dylib,
 575         raw_identifiers,
 576         raw_ref_op,
 577         Ready,
 578         reason,
 579         recursion_limit,
 580         reexport_test_harness_main,
 581         reflect,
 582         register_attr,
 583         register_tool,
 584         relaxed_adts,
 585         repr,
 586         repr128,
 587         repr_align,
 588         repr_align_enum,
 589         repr_packed,
 590         repr_simd,
 591         repr_transparent,
 592         re_rebalance_coherence,
 593         result,
 594         Result,
 595         Return,
 596         rhs,
 597         rlib,
 598         rotate_left,
 599         rotate_right,
 600         rt,
 601         rtm_target_feature,
 602         rust,
 603         rust_2015_preview,
 604         rust_2018_preview,
 605         rust_begin_unwind,
 606         rustc,
 607         RustcDecodable,
 608         RustcEncodable,
 609         rustc_allocator,
 610         rustc_allocator_nounwind,
 611         rustc_allow_const_fn_ptr,
 612         rustc_args_required_const,
 613         rustc_attrs,
 614         rustc_builtin_macro,
 615         rustc_clean,
 616         rustc_const_unstable,
 617         rustc_const_stable,
 618         rustc_conversion_suggestion,
 619         rustc_def_path,
 620         rustc_deprecated,
 621         rustc_diagnostic_item,
 622         rustc_diagnostic_macros,
 623         rustc_dirty,
 624         rustc_dummy,
 625         rustc_dump_env_program_clauses,
 626         rustc_dump_program_clauses,
 627         rustc_dump_user_substs,
 628         rustc_error,
 629         rustc_expected_cgu_reuse,
 630         rustc_if_this_changed,
 631         rustc_inherit_overflow_checks,
 632         rustc_layout,
 633         rustc_layout_scalar_valid_range_end,
 634         rustc_layout_scalar_valid_range_start,
 635         rustc_macro_transparency,
 636         rustc_mir,
 637         rustc_nonnull_optimization_guaranteed,
 638         rustc_object_lifetime_default,
 639         rustc_on_unimplemented,
 640         rustc_outlives,
 641         rustc_paren_sugar,
 642         rustc_partition_codegened,
 643         rustc_partition_reused,
 644         rustc_peek,
 645         rustc_peek_definite_init,
 646         rustc_peek_maybe_init,
 647         rustc_peek_maybe_uninit,
 648         rustc_peek_indirectly_mutable,
 649         rustc_private,
 650         rustc_proc_macro_decls,
 651         rustc_promotable,
 652         rustc_regions,
 653         rustc_stable,
 654         rustc_std_internal_symbol,
 655         rustc_symbol_name,
 656         rustc_synthetic,
 657         rustc_reservation_impl,
 658         rustc_test_marker,
 659         rustc_then_this_would_need,
 660         rustc_variance,
 661         rustfmt,
 662         rust_eh_personality,
 663         rust_eh_unwind_resume,
 664         rust_oom,
 665         rvalue_static_promotion,
 666         sanitize,
 667         sanitizer_runtime,
 668         saturating_add,
 669         saturating_sub,
 670         _Self,
 671         self_in_typedefs,
 672         self_struct_ctor,
 673         send_trait,
 674         should_panic,
 675         simd,
 676         simd_extract,
 677         simd_ffi,
 678         simd_insert,
 679         since,
 680         size,
 681         size_of,
 682         slice_patterns,
 683         slicing_syntax,
 684         soft,
 685         Some,
 686         specialization,
 687         speed,
 688         spotlight,
 689         sse4a_target_feature,
 690         stable,
 691         staged_api,
 692         start,
 693         static_in_const,
 694         staticlib,
 695         static_nobundle,
 696         static_recursion,
 697         std,
 698         std_inject,
 699         str,
 700         stringify,
 701         stmt,
 702         stmt_expr_attributes,
 703         stop_after_dataflow,
 704         struct_field_attributes,
 705         struct_inherit,
 706         structural_match,
 707         struct_variant,
 708         sty,
 709         sub_with_overflow,
 710         suggestion,
 711         sync_trait,
 712         target_feature,
 713         target_has_atomic,
 714         target_has_atomic_load_store,
 715         target_thread_local,
 716         task,
 717         tbm_target_feature,
 718         termination_trait,
 719         termination_trait_test,
 720         test,
 721         test_2018_feature,
 722         test_accepted_feature,
 723         test_case,
 724         test_removed_feature,
 725         test_runner,
 726         then_with,
 727         thread,
 728         thread_local,
 729         tool_attributes,
 730         tool_lints,
 731         trace_macros,
 732         track_caller,
 733         trait_alias,
 734         transmute,
 735         transparent,
 736         transparent_enums,
 737         transparent_unions,
 738         trivial_bounds,
 739         Try,
 740         try_blocks,
 741         try_trait,
 742         tt,
 743         tuple_indexing,
 744         two_phase,
 745         Ty,
 746         ty,
 747         type_alias_impl_trait,
 748         type_id,
 749         type_name,
 750         TyCtxt,
 751         TyKind,
 752         type_alias_enum_variants,
 753         type_ascription,
 754         type_length_limit,
 755         type_macros,
 756         u128,
 757         u16,
 758         u32,
 759         u64,
 760         u8,
 761         unboxed_closures,
 762         unchecked_add,
 763         unchecked_div,
 764         unchecked_mul,
 765         unchecked_rem,
 766         unchecked_shl,
 767         unchecked_shr,
 768         unchecked_sub,
 769         underscore_const_names,
 770         underscore_imports,
 771         underscore_lifetimes,
 772         uniform_paths,
 773         universal_impl_trait,
 774         unmarked_api,
 775         unreachable_code,
 776         unrestricted_attribute_tokens,
 777         unsafe_no_drop_flag,
 778         unsized_locals,
 779         unsized_tuple_coercion,
 780         unstable,
 781         untagged_unions,
 782         unwind,
 783         unwind_attributes,
 784         unwrap_or,
 785         used,
 786         use_extern_macros,
 787         use_nested_groups,
 788         usize,
 789         v1,
 790         val,
 791         var,
 792         vec,
 793         Vec,
 794         vis,
 795         visible_private_types,
 796         volatile,
 797         warn,
 798         wasm_import_module,
 799         wasm_target_feature,
 800         while_let,
 801         windows,
 802         windows_subsystem,
 803         wrapping_add,
 804         wrapping_sub,
 805         wrapping_mul,
 806         Yield,
 807     }
 808 }
 809
 810 #[derive(Copy, Clone, Eq, HashStable_Generic)]
 811 pub struct Ident {
 812     pub name: Symbol,
 813     pub span: Span,
 814 }
 815
 816 impl Ident {
 817     #[inline]
 818     /// Constructs a new identifier from a symbol and a span.
 819     pub const fn new(name: Symbol, span: Span) -> Ident {
 820         Ident { name, span }
 821     }
 822
 823     /// Constructs a new identifier with a dummy span.
 824     #[inline]
 825     pub const fn with_dummy_span(name: Symbol) -> Ident {
 826         Ident::new(name, DUMMY_SP)
 827     }
 828
 829     #[inline]
 830     pub fn invalid() -> Ident {
 831         Ident::with_dummy_span(kw::Invalid)
 832     }
 833
 834     /// Maps a string to an identifier with a dummy span.
 835     pub fn from_str(string: &str) -> Ident {
 836         Ident::with_dummy_span(Symbol::intern(string))
 837     }
 838
 839     /// Maps a string and a span to an identifier.
 840     pub fn from_str_and_span(string: &str, span: Span) -> Ident {
 841         Ident::new(Symbol::intern(string), span)
 842     }
 843
 844     /// Replaces `lo` and `hi` with those from `span`, but keep hygiene context.
 845     pub fn with_span_pos(self, span: Span) -> Ident {
 846         Ident::new(self.name, span.with_ctxt(self.span.ctxt()))
 847     }
 848
 849     pub fn without_first_quote(self) -> Ident {
 850         Ident::new(Symbol::intern(self.as_str().trim_start_matches('\'')), self.span)
 851     }
 852
 853     /// "Normalize" ident for use in comparisons using "item hygiene".
 854     /// Identifiers with same string value become same if they came from the same "modern" macro
 855     /// (e.g., `macro` item, but not `macro_rules` item) and stay different if they came from
 856     /// different "modern" macros.
 857     /// Technically, this operation strips all non-opaque marks from ident's syntactic context.
 858     pub fn modern(self) -> Ident {
 859         Ident::new(self.name, self.span.modern())
 860     }
 861
 862     /// "Normalize" ident for use in comparisons using "local variable hygiene".
 863     /// Identifiers with same string value become same if they came from the same non-transparent
 864     /// macro (e.g., `macro` or `macro_rules!` items) and stay different if they came from different
 865     /// non-transparent macros.
 866     /// Technically, this operation strips all transparent marks from ident's syntactic context.
 867     pub fn modern_and_legacy(self) -> Ident {
 868         Ident::new(self.name, self.span.modern_and_legacy())
 869     }
 870
 871     /// Convert the name to a `SymbolStr`. This is a slowish operation because
 872     /// it requires locking the symbol interner.
 873     pub fn as_str(self) -> SymbolStr {
 874         self.name.as_str()
 875     }
 876 }
 877
 878 impl PartialEq for Ident {
 879     fn eq(&self, rhs: &Self) -> bool {
 880         self.name == rhs.name && self.span.ctxt() == rhs.span.ctxt()
 881     }
 882 }
 883
 884 impl Hash for Ident {
 885     fn hash<H: Hasher>(&self, state: &mut H) {
 886         self.name.hash(state);
 887         self.span.ctxt().hash(state);
 888     }
 889 }
 890
 891 impl fmt::Debug for Ident {
 892     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 893         if self.is_raw_guess() {
 894             write!(f, "r#")?;
 895         }
 896         write!(f, "{}{:?}", self.name, self.span.ctxt())
 897     }
 898 }
 899
 900 impl fmt::Display for Ident {
 901     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 902         if self.is_raw_guess() {
 903             write!(f, "r#")?;
 904         }
 905         fmt::Display::fmt(&self.name, f)
 906     }
 907 }
 908
 909 impl UseSpecializedEncodable for Ident {
 910     fn default_encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
 911         s.emit_struct("Ident", 2, |s| {
 912             s.emit_struct_field("name", 0, |s| self.name.encode(s))?;
 913             s.emit_struct_field("span", 1, |s| self.span.encode(s))
 914         })
 915     }
 916 }
 917
 918 impl UseSpecializedDecodable for Ident {
 919     fn default_decode<D: Decoder>(d: &mut D) -> Result<Self, D::Error> {
 920         d.read_struct("Ident", 2, |d| {
 921             Ok(Ident {
 922                 name: d.read_struct_field("name", 0, Decodable::decode)?,
 923                 span: d.read_struct_field("span", 1, Decodable::decode)?,
 924             })
 925         })
 926     }
 927 }
 928
 929 /// An interned string.
 930 ///
 931 /// Internally, a `Symbol` is implemented as an index, and all operations
 932 /// (including hashing, equality, and ordering) operate on that index. The use
 933 /// of `rustc_index::newtype_index!` means that `Option<Symbol>` only takes up 4 bytes,
 934 /// because `rustc_index::newtype_index!` reserves the last 256 values for tagging purposes.
 935 ///
 936 /// Note that `Symbol` cannot directly be a `rustc_index::newtype_index!` because it
 937 /// implements `fmt::Debug`, `Encodable`, and `Decodable` in special ways.
 938 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
 939 pub struct Symbol(SymbolIndex);
 940
 941 rustc_index::newtype_index! {
 942     pub struct SymbolIndex { .. }
 943 }
 944
 945 impl Symbol {
 946     const fn new(n: u32) -> Self {
 947         Symbol(SymbolIndex::from_u32_const(n))
 948     }
 949
 950     /// Maps a string to its interned representation.
 951     pub fn intern(string: &str) -> Self {
 952         with_interner(|interner| interner.intern(string))
 953     }
 954
 955     /// Access the symbol's chars. This is a slowish operation because it
 956     /// requires locking the symbol interner.
 957     pub fn with<F: FnOnce(&str) -> R, R>(self, f: F) -> R {
 958         with_interner(|interner| f(interner.get(self)))
 959     }
 960
 961     /// Convert to a `SymbolStr`. This is a slowish operation because it
 962     /// requires locking the symbol interner.
 963     pub fn as_str(self) -> SymbolStr {
 964         with_interner(|interner| unsafe {
 965             SymbolStr { string: std::mem::transmute::<&str, &str>(interner.get(self)) }
 966         })
 967     }
 968
 969     pub fn as_u32(self) -> u32 {
 970         self.0.as_u32()
 971     }
 972 }
 973
 974 impl fmt::Debug for Symbol {
 975     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 976         self.with(|str| fmt::Debug::fmt(&str, f))
 977     }
 978 }
 979
 980 impl fmt::Display for Symbol {
 981     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 982         self.with(|str| fmt::Display::fmt(&str, f))
 983     }
 984 }
 985
 986 impl Encodable for Symbol {
 987     fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
 988         self.with(|string| s.emit_str(string))
 989     }
 990 }
 991
 992 impl Decodable for Symbol {
 993     fn decode<D: Decoder>(d: &mut D) -> Result<Symbol, D::Error> {
 994         Ok(Symbol::intern(&d.read_str()?))
 995     }
 996 }
 997
 998 impl<CTX> HashStable<CTX> for Symbol {
 999     #[inline]
1000     fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
1001         self.as_str().hash_stable(hcx, hasher);
1002     }
1003 }
1004
1005 impl<CTX> ToStableHashKey<CTX> for Symbol {
1006     type KeyType = SymbolStr;
1007
1008     #[inline]
1009     fn to_stable_hash_key(&self, _: &CTX) -> SymbolStr {
1010         self.as_str()
1011     }
1012 }
1013
1014 // The `&'static str`s in this type actually point into the arena.
1015 #[derive(Default)]
1016 pub struct Interner {
1017     arena: DroplessArena,
1018     names: FxHashMap<&'static str, Symbol>,
1019     strings: Vec<&'static str>,
1020 }
1021
1022 impl Interner {
1023     fn prefill(init: &[&'static str]) -> Self {
1024         Interner {
1025             strings: init.into(),
1026             names: init.iter().copied().zip((0..).map(Symbol::new)).collect(),
1027             ..Default::default()
1028         }
1029     }
1030
1031     pub fn intern(&mut self, string: &str) -> Symbol {
1032         if let Some(&name) = self.names.get(string) {
1033             return name;
1034         }
1035
1036         let name = Symbol::new(self.strings.len() as u32);
1037
1038         // `from_utf8_unchecked` is safe since we just allocated a `&str` which is known to be
1039         // UTF-8.
1040         let string: &str =
1041             unsafe { str::from_utf8_unchecked(self.arena.alloc_slice(string.as_bytes())) };
1042         // It is safe to extend the arena allocation to `'static` because we only access
1043         // these while the arena is still alive.
1044         let string: &'static str = unsafe { &*(string as *const str) };
1045         self.strings.push(string);
1046         self.names.insert(string, name);
1047         name
1048     }
1049
1050     // Get the symbol as a string. `Symbol::as_str()` should be used in
1051     // preference to this function.
1052     pub fn get(&self, symbol: Symbol) -> &str {
1053         self.strings[symbol.0.as_usize()]
1054     }
1055 }
1056
1057 // This module has a very short name because it's used a lot.
1058 pub mod kw {
1059     use super::Symbol;
1060     keywords!();
1061 }
1062
1063 // This module has a very short name because it's used a lot.
1064 #[allow(rustc::default_hash_types)]
1065 pub mod sym {
1066     use super::Symbol;
1067     use std::convert::TryInto;
1068
1069     symbols!();
1070
1071     // Get the symbol for an integer. The first few non-negative integers each
1072     // have a static symbol and therefore are fast.
1073     pub fn integer<N: TryInto<usize> + Copy + ToString>(n: N) -> Symbol {
1074         if let Result::Ok(idx) = n.try_into() {
1075             if let Option::Some(&sym) = digits_array.get(idx) {
1076                 return sym;
1077             }
1078         }
1079         Symbol::intern(&n.to_string())
1080     }
1081 }
1082
1083 impl Symbol {
1084     fn is_used_keyword_2018(self) -> bool {
1085         self >= kw::Async && self <= kw::Dyn
1086     }
1087
1088     fn is_unused_keyword_2018(self) -> bool {
1089         self == kw::Try
1090     }
1091
1092     /// Used for sanity checking rustdoc keyword sections.
1093     pub fn is_doc_keyword(self) -> bool {
1094         self <= kw::Union
1095     }
1096
1097     /// A keyword or reserved identifier that can be used as a path segment.
1098     pub fn is_path_segment_keyword(self) -> bool {
1099         self == kw::Super
1100             || self == kw::SelfLower
1101             || self == kw::SelfUpper
1102             || self == kw::Crate
1103             || self == kw::PathRoot
1104             || self == kw::DollarCrate
1105     }
1106
1107     /// Returns `true` if the symbol is `true` or `false`.
1108     pub fn is_bool_lit(self) -> bool {
1109         self == kw::True || self == kw::False
1110     }
1111
1112     /// This symbol can be a raw identifier.
1113     pub fn can_be_raw(self) -> bool {
1114         self != kw::Invalid && self != kw::Underscore && !self.is_path_segment_keyword()
1115     }
1116 }
1117
1118 impl Ident {
1119     // Returns `true` for reserved identifiers used internally for elided lifetimes,
1120     // unnamed method parameters, crate root module, error recovery etc.
1121     pub fn is_special(self) -> bool {
1122         self.name <= kw::Underscore
1123     }
1124
1125     /// Returns `true` if the token is a keyword used in the language.
1126     pub fn is_used_keyword(self) -> bool {
1127         // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
1128         self.name >= kw::As && self.name <= kw::While
1129             || self.name.is_used_keyword_2018() && self.span.rust_2018()
1130     }
1131
1132     /// Returns `true` if the token is a keyword reserved for possible future use.
1133     pub fn is_unused_keyword(self) -> bool {
1134         // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
1135         self.name >= kw::Abstract && self.name <= kw::Yield
1136             || self.name.is_unused_keyword_2018() && self.span.rust_2018()
1137     }
1138
1139     /// Returns `true` if the token is either a special identifier or a keyword.
1140     pub fn is_reserved(self) -> bool {
1141         self.is_special() || self.is_used_keyword() || self.is_unused_keyword()
1142     }
1143
1144     /// A keyword or reserved identifier that can be used as a path segment.
1145     pub fn is_path_segment_keyword(self) -> bool {
1146         self.name.is_path_segment_keyword()
1147     }
1148
1149     /// We see this identifier in a normal identifier position, like variable name or a type.
1150     /// How was it written originally? Did it use the raw form? Let's try to guess.
1151     pub fn is_raw_guess(self) -> bool {
1152         self.name.can_be_raw() && self.is_reserved()
1153     }
1154 }
1155
1156 #[inline]
1157 fn with_interner<T, F: FnOnce(&mut Interner) -> T>(f: F) -> T {
1158     GLOBALS.with(|globals| f(&mut *globals.symbol_interner.lock()))
1159 }
1160
1161 /// An alternative to `Symbol`, useful when the chars within the symbol need to
1162 /// be accessed. It deliberately has limited functionality and should only be
1163 /// used for temporary values.
1164 ///
1165 /// Because the interner outlives any thread which uses this type, we can
1166 /// safely treat `string` which points to interner data, as an immortal string,
1167 /// as long as this type never crosses between threads.
1168 //
1169 // FIXME: ensure that the interner outlives any thread which uses `SymbolStr`,
1170 // by creating a new thread right after constructing the interner.
1171 #[derive(Clone, Eq, PartialOrd, Ord)]
1172 pub struct SymbolStr {
1173     string: &'static str,
1174 }
1175
1176 // This impl allows a `SymbolStr` to be directly equated with a `String` or
1177 // `&str`.
1178 impl<T: std::ops::Deref<Target = str>> std::cmp::PartialEq<T> for SymbolStr {
1179     fn eq(&self, other: &T) -> bool {
1180         self.string == other.deref()
1181     }
1182 }
1183
1184 impl !Send for SymbolStr {}
1185 impl !Sync for SymbolStr {}
1186
1187 /// This impl means that if `ss` is a `SymbolStr`:
1188 /// - `*ss` is a `str`;
1189 /// - `&*ss` is a `&str`;
1190 /// - `&ss as &str` is a `&str`, which means that `&ss` can be passed to a
1191 ///   function expecting a `&str`.
1192 impl std::ops::Deref for SymbolStr {
1193     type Target = str;
1194     #[inline]
1195     fn deref(&self) -> &str {
1196         self.string
1197     }
1198 }
1199
1200 impl fmt::Debug for SymbolStr {
1201     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1202         fmt::Debug::fmt(self.string, f)
1203     }
1204 }
1205
1206 impl fmt::Display for SymbolStr {
1207     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1208         fmt::Display::fmt(self.string, f)
1209     }
1210 }
1211
1212 impl<CTX> HashStable<CTX> for SymbolStr {
1213     #[inline]
1214     fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
1215         self.string.hash_stable(hcx, hasher)
1216     }
1217 }
1218
1219 impl<CTX> ToStableHashKey<CTX> for SymbolStr {
1220     type KeyType = SymbolStr;
1221
1222     #[inline]
1223     fn to_stable_hash_key(&self, _: &CTX) -> SymbolStr {
1224         self.clone()
1225     }
1226 }