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