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_ref_pattern,
 461         move_val_init,
 462         movbe_target_feature,
 463         mul_with_overflow,
 464         must_use,
 465         naked,
 466         naked_functions,
 467         name,
 468         needs_allocator,
 469         needs_drop,
 470         needs_panic_runtime,
 471         negate_unsigned,
 472         never,
 473         never_type,
 474         never_type_fallback,
 475         new,
 476         next,
 477         __next,
 478         nll,
 479         no_builtins,
 480         no_core,
 481         no_crate_inject,
 482         no_debug,
 483         no_default_passes,
 484         no_implicit_prelude,
 485         no_inline,
 486         no_link,
 487         no_main,
 488         no_mangle,
 489         non_ascii_idents,
 490         None,
 491         non_exhaustive,
 492         non_modrs_mods,
 493         no_sanitize,
 494         no_stack_check,
 495         no_start,
 496         no_std,
 497         not,
 498         note,
 499         object_safe_for_dispatch,
 500         Ok,
 501         omit_gdb_pretty_printer_section,
 502         on,
 503         on_unimplemented,
 504         oom,
 505         ops,
 506         optimize,
 507         optimize_attribute,
 508         optin_builtin_traits,
 509         option,
 510         Option,
 511         option_env,
 512         opt_out_copy,
 513         or,
 514         or_patterns,
 515         Ord,
 516         Ordering,
 517         Output,
 518         overlapping_marker_traits,
 519         packed,
 520         panic,
 521         panic_handler,
 522         panic_impl,
 523         panic_implementation,
 524         panic_runtime,
 525         parent_trait,
 526         partial_cmp,
 527         param_attrs,
 528         PartialEq,
 529         PartialOrd,
 530         passes,
 531         pat,
 532         path,
 533         pattern_parentheses,
 534         Pending,
 535         pin,
 536         Pin,
 537         pinned,
 538         platform_intrinsics,
 539         plugin,
 540         plugin_registrar,
 541         plugins,
 542         Poll,
 543         poll_with_tls_context,
 544         powerpc_target_feature,
 545         precise_pointer_size_matching,
 546         pref_align_of,
 547         prelude,
 548         prelude_import,
 549         primitive,
 550         proc_dash_macro: "proc-macro",
 551         proc_macro,
 552         proc_macro_attribute,
 553         proc_macro_def_site,
 554         proc_macro_derive,
 555         proc_macro_expr,
 556         proc_macro_gen,
 557         proc_macro_hygiene,
 558         proc_macro_internals,
 559         proc_macro_mod,
 560         proc_macro_non_items,
 561         proc_macro_path_invoc,
 562         profiler_runtime,
 563         ptr_offset_from,
 564         pub_restricted,
 565         pushpop_unsafe,
 566         quad_precision_float,
 567         question_mark,
 568         quote,
 569         Range,
 570         RangeFrom,
 571         RangeFull,
 572         RangeInclusive,
 573         RangeTo,
 574         RangeToInclusive,
 575         raw_dylib,
 576         raw_identifiers,
 577         raw_ref_op,
 578         Ready,
 579         reason,
 580         recursion_limit,
 581         reexport_test_harness_main,
 582         reflect,
 583         register_attr,
 584         register_tool,
 585         relaxed_adts,
 586         repr,
 587         repr128,
 588         repr_align,
 589         repr_align_enum,
 590         repr_packed,
 591         repr_simd,
 592         repr_transparent,
 593         re_rebalance_coherence,
 594         result,
 595         Result,
 596         Return,
 597         rhs,
 598         rlib,
 599         rotate_left,
 600         rotate_right,
 601         rt,
 602         rtm_target_feature,
 603         rust,
 604         rust_2015_preview,
 605         rust_2018_preview,
 606         rust_begin_unwind,
 607         rustc,
 608         RustcDecodable,
 609         RustcEncodable,
 610         rustc_allocator,
 611         rustc_allocator_nounwind,
 612         rustc_allow_const_fn_ptr,
 613         rustc_args_required_const,
 614         rustc_attrs,
 615         rustc_builtin_macro,
 616         rustc_clean,
 617         rustc_const_unstable,
 618         rustc_const_stable,
 619         rustc_conversion_suggestion,
 620         rustc_def_path,
 621         rustc_deprecated,
 622         rustc_diagnostic_item,
 623         rustc_diagnostic_macros,
 624         rustc_dirty,
 625         rustc_dummy,
 626         rustc_dump_env_program_clauses,
 627         rustc_dump_program_clauses,
 628         rustc_dump_user_substs,
 629         rustc_error,
 630         rustc_expected_cgu_reuse,
 631         rustc_if_this_changed,
 632         rustc_inherit_overflow_checks,
 633         rustc_layout,
 634         rustc_layout_scalar_valid_range_end,
 635         rustc_layout_scalar_valid_range_start,
 636         rustc_macro_transparency,
 637         rustc_mir,
 638         rustc_nonnull_optimization_guaranteed,
 639         rustc_object_lifetime_default,
 640         rustc_on_unimplemented,
 641         rustc_outlives,
 642         rustc_paren_sugar,
 643         rustc_partition_codegened,
 644         rustc_partition_reused,
 645         rustc_peek,
 646         rustc_peek_definite_init,
 647         rustc_peek_maybe_init,
 648         rustc_peek_maybe_uninit,
 649         rustc_peek_indirectly_mutable,
 650         rustc_private,
 651         rustc_proc_macro_decls,
 652         rustc_promotable,
 653         rustc_regions,
 654         rustc_stable,
 655         rustc_std_internal_symbol,
 656         rustc_symbol_name,
 657         rustc_synthetic,
 658         rustc_reservation_impl,
 659         rustc_test_marker,
 660         rustc_then_this_would_need,
 661         rustc_variance,
 662         rustfmt,
 663         rust_eh_personality,
 664         rust_eh_unwind_resume,
 665         rust_oom,
 666         rvalue_static_promotion,
 667         sanitize,
 668         sanitizer_runtime,
 669         saturating_add,
 670         saturating_sub,
 671         _Self,
 672         self_in_typedefs,
 673         self_struct_ctor,
 674         send_trait,
 675         should_panic,
 676         simd,
 677         simd_extract,
 678         simd_ffi,
 679         simd_insert,
 680         since,
 681         size,
 682         size_of,
 683         slice_patterns,
 684         slicing_syntax,
 685         soft,
 686         Some,
 687         specialization,
 688         speed,
 689         spotlight,
 690         sse4a_target_feature,
 691         stable,
 692         staged_api,
 693         start,
 694         static_in_const,
 695         staticlib,
 696         static_nobundle,
 697         static_recursion,
 698         std,
 699         std_inject,
 700         str,
 701         stringify,
 702         stmt,
 703         stmt_expr_attributes,
 704         stop_after_dataflow,
 705         struct_field_attributes,
 706         struct_inherit,
 707         structural_match,
 708         struct_variant,
 709         sty,
 710         sub_with_overflow,
 711         suggestion,
 712         sync_trait,
 713         target_feature,
 714         target_has_atomic,
 715         target_has_atomic_load_store,
 716         target_thread_local,
 717         task,
 718         tbm_target_feature,
 719         termination_trait,
 720         termination_trait_test,
 721         test,
 722         test_2018_feature,
 723         test_accepted_feature,
 724         test_case,
 725         test_removed_feature,
 726         test_runner,
 727         then_with,
 728         thread,
 729         thread_local,
 730         tool_attributes,
 731         tool_lints,
 732         trace_macros,
 733         track_caller,
 734         trait_alias,
 735         transmute,
 736         transparent,
 737         transparent_enums,
 738         transparent_unions,
 739         trivial_bounds,
 740         Try,
 741         try_blocks,
 742         try_trait,
 743         tt,
 744         tuple_indexing,
 745         two_phase,
 746         Ty,
 747         ty,
 748         type_alias_impl_trait,
 749         type_id,
 750         type_name,
 751         TyCtxt,
 752         TyKind,
 753         type_alias_enum_variants,
 754         type_ascription,
 755         type_length_limit,
 756         type_macros,
 757         u128,
 758         u16,
 759         u32,
 760         u64,
 761         u8,
 762         unboxed_closures,
 763         unchecked_add,
 764         unchecked_div,
 765         unchecked_mul,
 766         unchecked_rem,
 767         unchecked_shl,
 768         unchecked_shr,
 769         unchecked_sub,
 770         underscore_const_names,
 771         underscore_imports,
 772         underscore_lifetimes,
 773         uniform_paths,
 774         universal_impl_trait,
 775         unmarked_api,
 776         unreachable_code,
 777         unrestricted_attribute_tokens,
 778         unsafe_no_drop_flag,
 779         unsized_locals,
 780         unsized_tuple_coercion,
 781         unstable,
 782         untagged_unions,
 783         unwind,
 784         unwind_attributes,
 785         unwrap_or,
 786         used,
 787         use_extern_macros,
 788         use_nested_groups,
 789         usize,
 790         v1,
 791         val,
 792         var,
 793         vec,
 794         Vec,
 795         vis,
 796         visible_private_types,
 797         volatile,
 798         warn,
 799         wasm_import_module,
 800         wasm_target_feature,
 801         while_let,
 802         windows,
 803         windows_subsystem,
 804         wrapping_add,
 805         wrapping_sub,
 806         wrapping_mul,
 807         Yield,
 808     }
 809 }
 810
 811 #[derive(Copy, Clone, Eq, HashStable_Generic)]
 812 pub struct Ident {
 813     pub name: Symbol,
 814     pub span: Span,
 815 }
 816
 817 impl Ident {
 818     #[inline]
 819     /// Constructs a new identifier from a symbol and a span.
 820     pub const fn new(name: Symbol, span: Span) -> Ident {
 821         Ident { name, span }
 822     }
 823
 824     /// Constructs a new identifier with a dummy span.
 825     #[inline]
 826     pub const fn with_dummy_span(name: Symbol) -> Ident {
 827         Ident::new(name, DUMMY_SP)
 828     }
 829
 830     #[inline]
 831     pub fn invalid() -> Ident {
 832         Ident::with_dummy_span(kw::Invalid)
 833     }
 834
 835     /// Maps a string to an identifier with a dummy span.
 836     pub fn from_str(string: &str) -> Ident {
 837         Ident::with_dummy_span(Symbol::intern(string))
 838     }
 839
 840     /// Maps a string and a span to an identifier.
 841     pub fn from_str_and_span(string: &str, span: Span) -> Ident {
 842         Ident::new(Symbol::intern(string), span)
 843     }
 844
 845     /// Replaces `lo` and `hi` with those from `span`, but keep hygiene context.
 846     pub fn with_span_pos(self, span: Span) -> Ident {
 847         Ident::new(self.name, span.with_ctxt(self.span.ctxt()))
 848     }
 849
 850     pub fn without_first_quote(self) -> Ident {
 851         Ident::new(Symbol::intern(self.as_str().trim_start_matches('\'')), self.span)
 852     }
 853
 854     /// "Normalize" ident for use in comparisons using "item hygiene".
 855     /// Identifiers with same string value become same if they came from the same "modern" macro
 856     /// (e.g., `macro` item, but not `macro_rules` item) and stay different if they came from
 857     /// different "modern" macros.
 858     /// Technically, this operation strips all non-opaque marks from ident's syntactic context.
 859     pub fn modern(self) -> Ident {
 860         Ident::new(self.name, self.span.modern())
 861     }
 862
 863     /// "Normalize" ident for use in comparisons using "local variable hygiene".
 864     /// Identifiers with same string value become same if they came from the same non-transparent
 865     /// macro (e.g., `macro` or `macro_rules!` items) and stay different if they came from different
 866     /// non-transparent macros.
 867     /// Technically, this operation strips all transparent marks from ident's syntactic context.
 868     pub fn modern_and_legacy(self) -> Ident {
 869         Ident::new(self.name, self.span.modern_and_legacy())
 870     }
 871
 872     /// Convert the name to a `SymbolStr`. This is a slowish operation because
 873     /// it requires locking the symbol interner.
 874     pub fn as_str(self) -> SymbolStr {
 875         self.name.as_str()
 876     }
 877 }
 878
 879 impl PartialEq for Ident {
 880     fn eq(&self, rhs: &Self) -> bool {
 881         self.name == rhs.name && self.span.ctxt() == rhs.span.ctxt()
 882     }
 883 }
 884
 885 impl Hash for Ident {
 886     fn hash<H: Hasher>(&self, state: &mut H) {
 887         self.name.hash(state);
 888         self.span.ctxt().hash(state);
 889     }
 890 }
 891
 892 impl fmt::Debug for Ident {
 893     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 894         if self.is_raw_guess() {
 895             write!(f, "r#")?;
 896         }
 897         write!(f, "{}{:?}", self.name, self.span.ctxt())
 898     }
 899 }
 900
 901 impl fmt::Display for Ident {
 902     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 903         if self.is_raw_guess() {
 904             write!(f, "r#")?;
 905         }
 906         fmt::Display::fmt(&self.name, f)
 907     }
 908 }
 909
 910 impl UseSpecializedEncodable for Ident {
 911     fn default_encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
 912         s.emit_struct("Ident", 2, |s| {
 913             s.emit_struct_field("name", 0, |s| self.name.encode(s))?;
 914             s.emit_struct_field("span", 1, |s| self.span.encode(s))
 915         })
 916     }
 917 }
 918
 919 impl UseSpecializedDecodable for Ident {
 920     fn default_decode<D: Decoder>(d: &mut D) -> Result<Self, D::Error> {
 921         d.read_struct("Ident", 2, |d| {
 922             Ok(Ident {
 923                 name: d.read_struct_field("name", 0, Decodable::decode)?,
 924                 span: d.read_struct_field("span", 1, Decodable::decode)?,
 925             })
 926         })
 927     }
 928 }
 929
 930 /// An interned string.
 931 ///
 932 /// Internally, a `Symbol` is implemented as an index, and all operations
 933 /// (including hashing, equality, and ordering) operate on that index. The use
 934 /// of `rustc_index::newtype_index!` means that `Option<Symbol>` only takes up 4 bytes,
 935 /// because `rustc_index::newtype_index!` reserves the last 256 values for tagging purposes.
 936 ///
 937 /// Note that `Symbol` cannot directly be a `rustc_index::newtype_index!` because it
 938 /// implements `fmt::Debug`, `Encodable`, and `Decodable` in special ways.
 939 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
 940 pub struct Symbol(SymbolIndex);
 941
 942 rustc_index::newtype_index! {
 943     pub struct SymbolIndex { .. }
 944 }
 945
 946 impl Symbol {
 947     const fn new(n: u32) -> Self {
 948         Symbol(SymbolIndex::from_u32_const(n))
 949     }
 950
 951     /// Maps a string to its interned representation.
 952     pub fn intern(string: &str) -> Self {
 953         with_interner(|interner| interner.intern(string))
 954     }
 955
 956     /// Access the symbol's chars. This is a slowish operation because it
 957     /// requires locking the symbol interner.
 958     pub fn with<F: FnOnce(&str) -> R, R>(self, f: F) -> R {
 959         with_interner(|interner| f(interner.get(self)))
 960     }
 961
 962     /// Convert to a `SymbolStr`. This is a slowish operation because it
 963     /// requires locking the symbol interner.
 964     pub fn as_str(self) -> SymbolStr {
 965         with_interner(|interner| unsafe {
 966             SymbolStr { string: std::mem::transmute::<&str, &str>(interner.get(self)) }
 967         })
 968     }
 969
 970     pub fn as_u32(self) -> u32 {
 971         self.0.as_u32()
 972     }
 973 }
 974
 975 impl fmt::Debug for Symbol {
 976     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 977         self.with(|str| fmt::Debug::fmt(&str, f))
 978     }
 979 }
 980
 981 impl fmt::Display for Symbol {
 982     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 983         self.with(|str| fmt::Display::fmt(&str, f))
 984     }
 985 }
 986
 987 impl Encodable for Symbol {
 988     fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
 989         self.with(|string| s.emit_str(string))
 990     }
 991 }
 992
 993 impl Decodable for Symbol {
 994     fn decode<D: Decoder>(d: &mut D) -> Result<Symbol, D::Error> {
 995         Ok(Symbol::intern(&d.read_str()?))
 996     }
 997 }
 998
 999 impl<CTX> HashStable<CTX> for Symbol {
1000     #[inline]
1001     fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
1002         self.as_str().hash_stable(hcx, hasher);
1003     }
1004 }
1005
1006 impl<CTX> ToStableHashKey<CTX> for Symbol {
1007     type KeyType = SymbolStr;
1008
1009     #[inline]
1010     fn to_stable_hash_key(&self, _: &CTX) -> SymbolStr {
1011         self.as_str()
1012     }
1013 }
1014
1015 // The `&'static str`s in this type actually point into the arena.
1016 #[derive(Default)]
1017 pub struct Interner {
1018     arena: DroplessArena,
1019     names: FxHashMap<&'static str, Symbol>,
1020     strings: Vec<&'static str>,
1021 }
1022
1023 impl Interner {
1024     fn prefill(init: &[&'static str]) -> Self {
1025         Interner {
1026             strings: init.into(),
1027             names: init.iter().copied().zip((0..).map(Symbol::new)).collect(),
1028             ..Default::default()
1029         }
1030     }
1031
1032     pub fn intern(&mut self, string: &str) -> Symbol {
1033         if let Some(&name) = self.names.get(string) {
1034             return name;
1035         }
1036
1037         let name = Symbol::new(self.strings.len() as u32);
1038
1039         // `from_utf8_unchecked` is safe since we just allocated a `&str` which is known to be
1040         // UTF-8.
1041         let string: &str =
1042             unsafe { str::from_utf8_unchecked(self.arena.alloc_slice(string.as_bytes())) };
1043         // It is safe to extend the arena allocation to `'static` because we only access
1044         // these while the arena is still alive.
1045         let string: &'static str = unsafe { &*(string as *const str) };
1046         self.strings.push(string);
1047         self.names.insert(string, name);
1048         name
1049     }
1050
1051     // Get the symbol as a string. `Symbol::as_str()` should be used in
1052     // preference to this function.
1053     pub fn get(&self, symbol: Symbol) -> &str {
1054         self.strings[symbol.0.as_usize()]
1055     }
1056 }
1057
1058 // This module has a very short name because it's used a lot.
1059 pub mod kw {
1060     use super::Symbol;
1061     keywords!();
1062 }
1063
1064 // This module has a very short name because it's used a lot.
1065 #[allow(rustc::default_hash_types)]
1066 pub mod sym {
1067     use super::Symbol;
1068     use std::convert::TryInto;
1069
1070     symbols!();
1071
1072     // Get the symbol for an integer. The first few non-negative integers each
1073     // have a static symbol and therefore are fast.
1074     pub fn integer<N: TryInto<usize> + Copy + ToString>(n: N) -> Symbol {
1075         if let Result::Ok(idx) = n.try_into() {
1076             if let Option::Some(&sym) = digits_array.get(idx) {
1077                 return sym;
1078             }
1079         }
1080         Symbol::intern(&n.to_string())
1081     }
1082 }
1083
1084 impl Symbol {
1085     fn is_used_keyword_2018(self) -> bool {
1086         self >= kw::Async && self <= kw::Dyn
1087     }
1088
1089     fn is_unused_keyword_2018(self) -> bool {
1090         self == kw::Try
1091     }
1092
1093     /// Used for sanity checking rustdoc keyword sections.
1094     pub fn is_doc_keyword(self) -> bool {
1095         self <= kw::Union
1096     }
1097
1098     /// A keyword or reserved identifier that can be used as a path segment.
1099     pub fn is_path_segment_keyword(self) -> bool {
1100         self == kw::Super
1101             || self == kw::SelfLower
1102             || self == kw::SelfUpper
1103             || self == kw::Crate
1104             || self == kw::PathRoot
1105             || self == kw::DollarCrate
1106     }
1107
1108     /// Returns `true` if the symbol is `true` or `false`.
1109     pub fn is_bool_lit(self) -> bool {
1110         self == kw::True || self == kw::False
1111     }
1112
1113     /// This symbol can be a raw identifier.
1114     pub fn can_be_raw(self) -> bool {
1115         self != kw::Invalid && self != kw::Underscore && !self.is_path_segment_keyword()
1116     }
1117 }
1118
1119 impl Ident {
1120     // Returns `true` for reserved identifiers used internally for elided lifetimes,
1121     // unnamed method parameters, crate root module, error recovery etc.
1122     pub fn is_special(self) -> bool {
1123         self.name <= kw::Underscore
1124     }
1125
1126     /// Returns `true` if the token is a keyword used in the language.
1127     pub fn is_used_keyword(self) -> bool {
1128         // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
1129         self.name >= kw::As && self.name <= kw::While
1130             || self.name.is_used_keyword_2018() && self.span.rust_2018()
1131     }
1132
1133     /// Returns `true` if the token is a keyword reserved for possible future use.
1134     pub fn is_unused_keyword(self) -> bool {
1135         // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
1136         self.name >= kw::Abstract && self.name <= kw::Yield
1137             || self.name.is_unused_keyword_2018() && self.span.rust_2018()
1138     }
1139
1140     /// Returns `true` if the token is either a special identifier or a keyword.
1141     pub fn is_reserved(self) -> bool {
1142         self.is_special() || self.is_used_keyword() || self.is_unused_keyword()
1143     }
1144
1145     /// A keyword or reserved identifier that can be used as a path segment.
1146     pub fn is_path_segment_keyword(self) -> bool {
1147         self.name.is_path_segment_keyword()
1148     }
1149
1150     /// We see this identifier in a normal identifier position, like variable name or a type.
1151     /// How was it written originally? Did it use the raw form? Let's try to guess.
1152     pub fn is_raw_guess(self) -> bool {
1153         self.name.can_be_raw() && self.is_reserved()
1154     }
1155 }
1156
1157 #[inline]
1158 fn with_interner<T, F: FnOnce(&mut Interner) -> T>(f: F) -> T {
1159     GLOBALS.with(|globals| f(&mut *globals.symbol_interner.lock()))
1160 }
1161
1162 /// An alternative to `Symbol`, useful when the chars within the symbol need to
1163 /// be accessed. It deliberately has limited functionality and should only be
1164 /// used for temporary values.
1165 ///
1166 /// Because the interner outlives any thread which uses this type, we can
1167 /// safely treat `string` which points to interner data, as an immortal string,
1168 /// as long as this type never crosses between threads.
1169 //
1170 // FIXME: ensure that the interner outlives any thread which uses `SymbolStr`,
1171 // by creating a new thread right after constructing the interner.
1172 #[derive(Clone, Eq, PartialOrd, Ord)]
1173 pub struct SymbolStr {
1174     string: &'static str,
1175 }
1176
1177 // This impl allows a `SymbolStr` to be directly equated with a `String` or
1178 // `&str`.
1179 impl<T: std::ops::Deref<Target = str>> std::cmp::PartialEq<T> for SymbolStr {
1180     fn eq(&self, other: &T) -> bool {
1181         self.string == other.deref()
1182     }
1183 }
1184
1185 impl !Send for SymbolStr {}
1186 impl !Sync for SymbolStr {}
1187
1188 /// This impl means that if `ss` is a `SymbolStr`:
1189 /// - `*ss` is a `str`;
1190 /// - `&*ss` is a `&str`;
1191 /// - `&ss as &str` is a `&str`, which means that `&ss` can be passed to a
1192 ///   function expecting a `&str`.
1193 impl std::ops::Deref for SymbolStr {
1194     type Target = str;
1195     #[inline]
1196     fn deref(&self) -> &str {
1197         self.string
1198     }
1199 }
1200
1201 impl fmt::Debug for SymbolStr {
1202     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1203         fmt::Debug::fmt(self.string, f)
1204     }
1205 }
1206
1207 impl fmt::Display for SymbolStr {
1208     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1209         fmt::Display::fmt(self.string, f)
1210     }
1211 }
1212
1213 impl<CTX> HashStable<CTX> for SymbolStr {
1214     #[inline]
1215     fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
1216         self.string.hash_stable(hcx, hasher)
1217     }
1218 }
1219
1220 impl<CTX> ToStableHashKey<CTX> for SymbolStr {
1221     type KeyType = SymbolStr;
1222
1223     #[inline]
1224     fn to_stable_hash_key(&self, _: &CTX) -> SymbolStr {
1225         self.clone()
1226     }
1227 }