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         MacroRules:         "macro_rules",
 101         Raw:                "raw",
 102         Union:              "union",
 103     }
 104
 105     // Symbols that can be referred to with rustc_span::sym::*. The symbol is
 106     // the stringified identifier unless otherwise specified (e.g.
 107     // `proc_dash_macro` represents "proc-macro").
 108     //
 109     // As well as the symbols listed, there are symbols for the the strings
 110     // "0", "1", ..., "9", which are accessible via `sym::integer`.
 111     Symbols {
 112         aarch64_target_feature,
 113         abi,
 114         abi_amdgpu_kernel,
 115         abi_efiapi,
 116         abi_msp430_interrupt,
 117         abi_ptx,
 118         abi_sysv64,
 119         abi_thiscall,
 120         abi_unadjusted,
 121         abi_vectorcall,
 122         abi_x86_interrupt,
 123         aborts,
 124         address,
 125         add_with_overflow,
 126         advanced_slice_patterns,
 127         adx_target_feature,
 128         alias,
 129         align,
 130         alignstack,
 131         all,
 132         allocator,
 133         allocator_internals,
 134         alloc_error_handler,
 135         allow,
 136         allowed,
 137         allow_fail,
 138         allow_internal_unsafe,
 139         allow_internal_unstable,
 140         allow_internal_unstable_backcompat_hack,
 141         always,
 142         and,
 143         any,
 144         arbitrary_enum_discriminant,
 145         arbitrary_self_types,
 146         Arguments,
 147         ArgumentV1,
 148         arm_target_feature,
 149         asm,
 150         assert,
 151         associated_consts,
 152         associated_type_bounds,
 153         associated_type_defaults,
 154         associated_types,
 155         assume_init,
 156         async_await,
 157         async_closure,
 158         attr,
 159         attributes,
 160         attr_literals,
 161         augmented_assignments,
 162         automatically_derived,
 163         avx512_target_feature,
 164         await_macro,
 165         begin_panic,
 166         bench,
 167         bin,
 168         bind_by_move_pattern_guards,
 169         bindings_after_at,
 170         block,
 171         bool,
 172         borrowck_graphviz_format,
 173         borrowck_graphviz_postflow,
 174         borrowck_graphviz_preflow,
 175         box_patterns,
 176         box_syntax,
 177         braced_empty_structs,
 178         bswap,
 179         bitreverse,
 180         C,
 181         caller_location,
 182         cdylib,
 183         cfg,
 184         cfg_attr,
 185         cfg_attr_multi,
 186         cfg_doctest,
 187         cfg_sanitize,
 188         cfg_target_feature,
 189         cfg_target_has_atomic,
 190         cfg_target_thread_local,
 191         cfg_target_vendor,
 192         char,
 193         clippy,
 194         clone,
 195         Clone,
 196         clone_closures,
 197         clone_from,
 198         closure_to_fn_coercion,
 199         cmp,
 200         cmpxchg16b_target_feature,
 201         cold,
 202         column,
 203         compile_error,
 204         compiler_builtins,
 205         concat,
 206         concat_idents,
 207         conservative_impl_trait,
 208         console,
 209         const_compare_raw_pointers,
 210         const_constructor,
 211         const_extern_fn,
 212         const_fn,
 213         const_fn_union,
 214         const_generics,
 215         const_if_match,
 216         const_indexing,
 217         const_in_array_repeat_expressions,
 218         const_let,
 219         const_loop,
 220         const_mut_refs,
 221         const_panic,
 222         const_raw_ptr_deref,
 223         const_raw_ptr_to_usize_cast,
 224         const_transmute,
 225         const_trait_bound_opt_out,
 226         const_trait_impl,
 227         contents,
 228         context,
 229         convert,
 230         Copy,
 231         copy_closures,
 232         core,
 233         core_intrinsics,
 234         crate_id,
 235         crate_in_paths,
 236         crate_local,
 237         crate_name,
 238         crate_type,
 239         crate_visibility_modifier,
 240         ctpop,
 241         cttz,
 242         cttz_nonzero,
 243         ctlz,
 244         ctlz_nonzero,
 245         custom_attribute,
 246         custom_derive,
 247         custom_inner_attributes,
 248         custom_test_frameworks,
 249         c_variadic,
 250         debug_trait,
 251         declare_lint_pass,
 252         decl_macro,
 253         Debug,
 254         Decodable,
 255         Default,
 256         default_lib_allocator,
 257         default_type_parameter_fallback,
 258         default_type_params,
 259         delay_span_bug_from_inside_query,
 260         deny,
 261         deprecated,
 262         deref,
 263         deref_mut,
 264         derive,
 265         diagnostic,
 266         direct,
 267         doc,
 268         doc_alias,
 269         doc_cfg,
 270         doc_keyword,
 271         doc_masked,
 272         doc_spotlight,
 273         doctest,
 274         document_private_items,
 275         dotdoteq_in_patterns,
 276         dotdot_in_tuple_patterns,
 277         double_braced_crate: "{{crate}}",
 278         double_braced_impl: "{{impl}}",
 279         double_braced_misc: "{{misc}}",
 280         double_braced_closure: "{{closure}}",
 281         double_braced_constructor: "{{constructor}}",
 282         double_braced_constant: "{{constant}}",
 283         double_braced_opaque: "{{opaque}}",
 284         dropck_eyepatch,
 285         dropck_parametricity,
 286         drop_types_in_const,
 287         dylib,
 288         dyn_trait,
 289         eh_personality,
 290         eh_unwind_resume,
 291         enable,
 292         Encodable,
 293         env,
 294         eq,
 295         err,
 296         Err,
 297         Eq,
 298         Equal,
 299         enclosing_scope,
 300         except,
 301         exclusive_range_pattern,
 302         exhaustive_integer_patterns,
 303         exhaustive_patterns,
 304         existential_type,
 305         expected,
 306         export_name,
 307         expr,
 308         extern_absolute_paths,
 309         external_doc,
 310         extern_crate_item_prelude,
 311         extern_crate_self,
 312         extern_in_paths,
 313         extern_prelude,
 314         extern_types,
 315         f16c_target_feature,
 316         f32,
 317         f64,
 318         feature,
 319         ffi_returns_twice,
 320         field,
 321         field_init_shorthand,
 322         file,
 323         fmt,
 324         fmt_internals,
 325         fn_must_use,
 326         forbid,
 327         format_args,
 328         format_args_nl,
 329         from,
 330         From,
 331         from_desugaring,
 332         from_error,
 333         from_generator,
 334         from_method,
 335         from_ok,
 336         from_usize,
 337         fundamental,
 338         future,
 339         Future,
 340         FxHashSet,
 341         FxHashMap,
 342         gen_future,
 343         gen_kill,
 344         generators,
 345         generic_associated_types,
 346         generic_param_attrs,
 347         global_allocator,
 348         global_asm,
 349         globs,
 350         half_open_range_patterns,
 351         hash,
 352         Hash,
 353         HashSet,
 354         HashMap,
 355         hexagon_target_feature,
 356         hidden,
 357         homogeneous_aggregate,
 358         html_favicon_url,
 359         html_logo_url,
 360         html_no_source,
 361         html_playground_url,
 362         html_root_url,
 363         i128,
 364         i128_type,
 365         i16,
 366         i32,
 367         i64,
 368         i8,
 369         ident,
 370         if_let,
 371         if_while_or_patterns,
 372         ignore,
 373         impl_header_lifetime_elision,
 374         impl_lint_pass,
 375         impl_trait_in_bindings,
 376         import_shadowing,
 377         index,
 378         index_mut,
 379         in_band_lifetimes,
 380         include,
 381         include_bytes,
 382         include_str,
 383         inclusive_range_syntax,
 384         infer_outlives_requirements,
 385         infer_static_outlives_requirements,
 386         inline,
 387         intel,
 388         into_iter,
 389         IntoIterator,
 390         into_result,
 391         intrinsics,
 392         irrefutable_let_patterns,
 393         isize,
 394         issue,
 395         issue_5723_bootstrap,
 396         issue_tracker_base_url,
 397         item,
 398         item_context: "ItemContext",
 399         item_like_imports,
 400         iter,
 401         Iterator,
 402         keyword,
 403         kind,
 404         label,
 405         label_break_value,
 406         lang,
 407         lang_items,
 408         let_chains,
 409         lhs,
 410         lib,
 411         lifetime,
 412         line,
 413         link,
 414         linkage,
 415         link_args,
 416         link_cfg,
 417         link_llvm_intrinsics,
 418         link_name,
 419         link_ordinal,
 420         link_section,
 421         LintPass,
 422         lint_reasons,
 423         literal,
 424         local_inner_macros,
 425         log_syntax,
 426         loop_break_value,
 427         macro_at_most_once_rep,
 428         macro_escape,
 429         macro_export,
 430         macro_lifetime_matcher,
 431         macro_literal_matcher,
 432         macro_reexport,
 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_niche,
 495         no_stack_check,
 496         no_start,
 497         no_std,
 498         not,
 499         note,
 500         object_safe_for_dispatch,
 501         Ok,
 502         omit_gdb_pretty_printer_section,
 503         on,
 504         on_unimplemented,
 505         oom,
 506         ops,
 507         optimize,
 508         optimize_attribute,
 509         optin_builtin_traits,
 510         option,
 511         Option,
 512         option_env,
 513         opt_out_copy,
 514         or,
 515         or_patterns,
 516         Ord,
 517         Ordering,
 518         Output,
 519         overlapping_marker_traits,
 520         packed,
 521         panic,
 522         panic_handler,
 523         panic_impl,
 524         panic_implementation,
 525         panic_runtime,
 526         parent_trait,
 527         partial_cmp,
 528         param_attrs,
 529         PartialEq,
 530         PartialOrd,
 531         passes,
 532         pat,
 533         path,
 534         pattern_parentheses,
 535         Pending,
 536         pin,
 537         Pin,
 538         pinned,
 539         platform_intrinsics,
 540         plugin,
 541         plugin_registrar,
 542         plugins,
 543         Poll,
 544         poll_with_tls_context,
 545         powerpc_target_feature,
 546         precise_pointer_size_matching,
 547         pref_align_of,
 548         prelude,
 549         prelude_import,
 550         primitive,
 551         proc_dash_macro: "proc-macro",
 552         proc_macro,
 553         proc_macro_attribute,
 554         proc_macro_def_site,
 555         proc_macro_derive,
 556         proc_macro_expr,
 557         proc_macro_gen,
 558         proc_macro_hygiene,
 559         proc_macro_internals,
 560         proc_macro_mod,
 561         proc_macro_non_items,
 562         proc_macro_path_invoc,
 563         profiler_runtime,
 564         ptr_offset_from,
 565         pub_restricted,
 566         pushpop_unsafe,
 567         quad_precision_float,
 568         question_mark,
 569         quote,
 570         Range,
 571         RangeFrom,
 572         RangeFull,
 573         RangeInclusive,
 574         RangeTo,
 575         RangeToInclusive,
 576         raw_dylib,
 577         raw_identifiers,
 578         raw_ref_op,
 579         Ready,
 580         reason,
 581         recursion_limit,
 582         reexport_test_harness_main,
 583         reflect,
 584         register_attr,
 585         register_tool,
 586         relaxed_adts,
 587         repr,
 588         repr128,
 589         repr_align,
 590         repr_align_enum,
 591         repr_no_niche,
 592         repr_packed,
 593         repr_simd,
 594         repr_transparent,
 595         re_rebalance_coherence,
 596         result,
 597         Result,
 598         Return,
 599         rhs,
 600         rlib,
 601         rotate_left,
 602         rotate_right,
 603         rt,
 604         rtm_target_feature,
 605         rust,
 606         rust_2015_preview,
 607         rust_2018_preview,
 608         rust_begin_unwind,
 609         rustc,
 610         RustcDecodable,
 611         RustcEncodable,
 612         rustc_allocator,
 613         rustc_allocator_nounwind,
 614         rustc_allow_const_fn_ptr,
 615         rustc_args_required_const,
 616         rustc_attrs,
 617         rustc_builtin_macro,
 618         rustc_clean,
 619         rustc_const_unstable,
 620         rustc_const_stable,
 621         rustc_conversion_suggestion,
 622         rustc_def_path,
 623         rustc_deprecated,
 624         rustc_diagnostic_item,
 625         rustc_diagnostic_macros,
 626         rustc_dirty,
 627         rustc_dummy,
 628         rustc_dump_env_program_clauses,
 629         rustc_dump_program_clauses,
 630         rustc_dump_user_substs,
 631         rustc_error,
 632         rustc_expected_cgu_reuse,
 633         rustc_if_this_changed,
 634         rustc_inherit_overflow_checks,
 635         rustc_layout,
 636         rustc_layout_scalar_valid_range_end,
 637         rustc_layout_scalar_valid_range_start,
 638         rustc_macro_transparency,
 639         rustc_mir,
 640         rustc_nonnull_optimization_guaranteed,
 641         rustc_object_lifetime_default,
 642         rustc_on_unimplemented,
 643         rustc_outlives,
 644         rustc_paren_sugar,
 645         rustc_partition_codegened,
 646         rustc_partition_reused,
 647         rustc_peek,
 648         rustc_peek_definite_init,
 649         rustc_peek_maybe_init,
 650         rustc_peek_maybe_uninit,
 651         rustc_peek_indirectly_mutable,
 652         rustc_private,
 653         rustc_proc_macro_decls,
 654         rustc_promotable,
 655         rustc_regions,
 656         rustc_stable,
 657         rustc_std_internal_symbol,
 658         rustc_symbol_name,
 659         rustc_synthetic,
 660         rustc_reservation_impl,
 661         rustc_test_marker,
 662         rustc_then_this_would_need,
 663         rustc_variance,
 664         rustfmt,
 665         rust_eh_personality,
 666         rust_eh_unwind_resume,
 667         rust_oom,
 668         rvalue_static_promotion,
 669         sanitize,
 670         sanitizer_runtime,
 671         saturating_add,
 672         saturating_sub,
 673         _Self,
 674         self_in_typedefs,
 675         self_struct_ctor,
 676         send_trait,
 677         should_panic,
 678         simd,
 679         simd_extract,
 680         simd_ffi,
 681         simd_insert,
 682         since,
 683         size,
 684         size_of,
 685         slice_patterns,
 686         slicing_syntax,
 687         soft,
 688         Some,
 689         specialization,
 690         speed,
 691         spotlight,
 692         sse4a_target_feature,
 693         stable,
 694         staged_api,
 695         start,
 696         static_in_const,
 697         staticlib,
 698         static_nobundle,
 699         static_recursion,
 700         std,
 701         std_inject,
 702         str,
 703         stringify,
 704         stmt,
 705         stmt_expr_attributes,
 706         stop_after_dataflow,
 707         struct_field_attributes,
 708         struct_inherit,
 709         structural_match,
 710         struct_variant,
 711         sty,
 712         sub_with_overflow,
 713         suggestion,
 714         sync_trait,
 715         target_feature,
 716         target_has_atomic,
 717         target_has_atomic_load_store,
 718         target_thread_local,
 719         task,
 720         tbm_target_feature,
 721         termination_trait,
 722         termination_trait_test,
 723         test,
 724         test_2018_feature,
 725         test_accepted_feature,
 726         test_case,
 727         test_removed_feature,
 728         test_runner,
 729         then_with,
 730         thread,
 731         thread_local,
 732         tool_attributes,
 733         tool_lints,
 734         trace_macros,
 735         track_caller,
 736         trait_alias,
 737         transmute,
 738         transparent,
 739         transparent_enums,
 740         transparent_unions,
 741         trivial_bounds,
 742         Try,
 743         try_blocks,
 744         try_trait,
 745         tt,
 746         tuple_indexing,
 747         two_phase,
 748         Ty,
 749         ty,
 750         type_alias_impl_trait,
 751         type_id,
 752         type_name,
 753         TyCtxt,
 754         TyKind,
 755         type_alias_enum_variants,
 756         type_ascription,
 757         type_length_limit,
 758         type_macros,
 759         u128,
 760         u16,
 761         u32,
 762         u64,
 763         u8,
 764         unboxed_closures,
 765         unchecked_add,
 766         unchecked_div,
 767         unchecked_mul,
 768         unchecked_rem,
 769         unchecked_shl,
 770         unchecked_shr,
 771         unchecked_sub,
 772         underscore_const_names,
 773         underscore_imports,
 774         underscore_lifetimes,
 775         uniform_paths,
 776         universal_impl_trait,
 777         unmarked_api,
 778         unreachable_code,
 779         unrestricted_attribute_tokens,
 780         unsafe_no_drop_flag,
 781         unsized_locals,
 782         unsized_tuple_coercion,
 783         unstable,
 784         untagged_unions,
 785         unwind,
 786         unwind_attributes,
 787         unwrap_or,
 788         used,
 789         use_extern_macros,
 790         use_nested_groups,
 791         usize,
 792         v1,
 793         val,
 794         var,
 795         vec,
 796         Vec,
 797         vis,
 798         visible_private_types,
 799         volatile,
 800         warn,
 801         wasm_import_module,
 802         wasm_target_feature,
 803         while_let,
 804         windows,
 805         windows_subsystem,
 806         wrapping_add,
 807         wrapping_sub,
 808         wrapping_mul,
 809         Yield,
 810     }
 811 }
 812
 813 #[derive(Copy, Clone, Eq, HashStable_Generic)]
 814 pub struct Ident {
 815     pub name: Symbol,
 816     pub span: Span,
 817 }
 818
 819 impl Ident {
 820     #[inline]
 821     /// Constructs a new identifier from a symbol and a span.
 822     pub const fn new(name: Symbol, span: Span) -> Ident {
 823         Ident { name, span }
 824     }
 825
 826     /// Constructs a new identifier with a dummy span.
 827     #[inline]
 828     pub const fn with_dummy_span(name: Symbol) -> Ident {
 829         Ident::new(name, DUMMY_SP)
 830     }
 831
 832     #[inline]
 833     pub fn invalid() -> Ident {
 834         Ident::with_dummy_span(kw::Invalid)
 835     }
 836
 837     /// Maps a string to an identifier with a dummy span.
 838     pub fn from_str(string: &str) -> Ident {
 839         Ident::with_dummy_span(Symbol::intern(string))
 840     }
 841
 842     /// Maps a string and a span to an identifier.
 843     pub fn from_str_and_span(string: &str, span: Span) -> Ident {
 844         Ident::new(Symbol::intern(string), span)
 845     }
 846
 847     /// Replaces `lo` and `hi` with those from `span`, but keep hygiene context.
 848     pub fn with_span_pos(self, span: Span) -> Ident {
 849         Ident::new(self.name, span.with_ctxt(self.span.ctxt()))
 850     }
 851
 852     pub fn without_first_quote(self) -> Ident {
 853         Ident::new(Symbol::intern(self.as_str().trim_start_matches('\'')), self.span)
 854     }
 855
 856     /// "Normalize" ident for use in comparisons using "item hygiene".
 857     /// Identifiers with same string value become same if they came from the same "modern" macro
 858     /// (e.g., `macro` item, but not `macro_rules` item) and stay different if they came from
 859     /// different "modern" macros.
 860     /// Technically, this operation strips all non-opaque marks from ident's syntactic context.
 861     pub fn modern(self) -> Ident {
 862         Ident::new(self.name, self.span.modern())
 863     }
 864
 865     /// "Normalize" ident for use in comparisons using "local variable hygiene".
 866     /// Identifiers with same string value become same if they came from the same non-transparent
 867     /// macro (e.g., `macro` or `macro_rules!` items) and stay different if they came from different
 868     /// non-transparent macros.
 869     /// Technically, this operation strips all transparent marks from ident's syntactic context.
 870     pub fn modern_and_legacy(self) -> Ident {
 871         Ident::new(self.name, self.span.modern_and_legacy())
 872     }
 873
 874     /// Convert the name to a `SymbolStr`. This is a slowish operation because
 875     /// it requires locking the symbol interner.
 876     pub fn as_str(self) -> SymbolStr {
 877         self.name.as_str()
 878     }
 879 }
 880
 881 impl PartialEq for Ident {
 882     fn eq(&self, rhs: &Self) -> bool {
 883         self.name == rhs.name && self.span.ctxt() == rhs.span.ctxt()
 884     }
 885 }
 886
 887 impl Hash for Ident {
 888     fn hash<H: Hasher>(&self, state: &mut H) {
 889         self.name.hash(state);
 890         self.span.ctxt().hash(state);
 891     }
 892 }
 893
 894 impl fmt::Debug for Ident {
 895     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 896         fmt::Display::fmt(self, f)?;
 897         fmt::Debug::fmt(&self.span.ctxt(), f)
 898     }
 899 }
 900
 901 /// This implementation is supposed to be used in error messages, so it's expected to be identical
 902 /// to printing the original identifier token written in source code (`token_to_string`),
 903 /// except that AST identifiers don't keep the rawness flag, so we have to guess it.
 904 impl fmt::Display for Ident {
 905     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 906         fmt::Display::fmt(&IdentPrinter::new(self.name, self.is_raw_guess(), None), 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 /// This is the most general way to print identifiers.
 931 /// AST pretty-printer is used as a fallback for turning AST structures into token streams for
 932 /// proc macros. Additionally, proc macros may stringify their input and expect it survive the
 933 /// stringification (especially true for proc macro derives written between Rust 1.15 and 1.30).
 934 /// So we need to somehow pretty-print `$crate` in a way preserving at least some of its
 935 /// hygiene data, most importantly name of the crate it refers to.
 936 /// As a result we print `$crate` as `crate` if it refers to the local crate
 937 /// and as `::other_crate_name` if it refers to some other crate.
 938 /// Note, that this is only done if the ident token is printed from inside of AST pretty-pringing,
 939 /// but not otherwise. Pretty-printing is the only way for proc macros to discover token contents,
 940 /// so we should not perform this lossy conversion if the top level call to the pretty-printer was
 941 /// done for a token stream or a single token.
 942 pub struct IdentPrinter {
 943     symbol: Symbol,
 944     is_raw: bool,
 945     /// Span used for retrieving the crate name to which `$crate` refers to,
 946     /// if this field is `None` then the `$crate` conversion doesn't happen.
 947     convert_dollar_crate: Option<Span>,
 948 }
 949
 950 impl IdentPrinter {
 951     /// The most general `IdentPrinter` constructor. Do not use this.
 952     pub fn new(symbol: Symbol, is_raw: bool, convert_dollar_crate: Option<Span>) -> IdentPrinter {
 953         IdentPrinter { symbol, is_raw, convert_dollar_crate }
 954     }
 955
 956     /// This implementation is supposed to be used when printing identifiers
 957     /// as a part of pretty-printing for larger AST pieces.
 958     /// Do not use this either.
 959     pub fn for_ast_ident(ident: Ident, is_raw: bool) -> IdentPrinter {
 960         IdentPrinter::new(ident.name, is_raw, Some(ident.span))
 961     }
 962 }
 963
 964 impl fmt::Display for IdentPrinter {
 965     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 966         if self.is_raw {
 967             f.write_str("r#")?;
 968         } else {
 969             if self.symbol == kw::DollarCrate {
 970                 if let Some(span) = self.convert_dollar_crate {
 971                     let converted = span.ctxt().dollar_crate_name();
 972                     if !converted.is_path_segment_keyword() {
 973                         f.write_str("::")?;
 974                     }
 975                     return fmt::Display::fmt(&converted, f);
 976                 }
 977             }
 978         }
 979         fmt::Display::fmt(&self.symbol, f)
 980     }
 981 }
 982
 983 /// An interned string.
 984 ///
 985 /// Internally, a `Symbol` is implemented as an index, and all operations
 986 /// (including hashing, equality, and ordering) operate on that index. The use
 987 /// of `rustc_index::newtype_index!` means that `Option<Symbol>` only takes up 4 bytes,
 988 /// because `rustc_index::newtype_index!` reserves the last 256 values for tagging purposes.
 989 ///
 990 /// Note that `Symbol` cannot directly be a `rustc_index::newtype_index!` because it
 991 /// implements `fmt::Debug`, `Encodable`, and `Decodable` in special ways.
 992 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
 993 pub struct Symbol(SymbolIndex);
 994
 995 rustc_index::newtype_index! {
 996     pub struct SymbolIndex { .. }
 997 }
 998
 999 impl Symbol {
1000     const fn new(n: u32) -> Self {
1001         Symbol(SymbolIndex::from_u32_const(n))
1002     }
1003
1004     /// Maps a string to its interned representation.
1005     pub fn intern(string: &str) -> Self {
1006         with_interner(|interner| interner.intern(string))
1007     }
1008
1009     /// Access the symbol's chars. This is a slowish operation because it
1010     /// requires locking the symbol interner.
1011     pub fn with<F: FnOnce(&str) -> R, R>(self, f: F) -> R {
1012         with_interner(|interner| f(interner.get(self)))
1013     }
1014
1015     /// Convert to a `SymbolStr`. This is a slowish operation because it
1016     /// requires locking the symbol interner.
1017     pub fn as_str(self) -> SymbolStr {
1018         with_interner(|interner| unsafe {
1019             SymbolStr { string: std::mem::transmute::<&str, &str>(interner.get(self)) }
1020         })
1021     }
1022
1023     pub fn as_u32(self) -> u32 {
1024         self.0.as_u32()
1025     }
1026 }
1027
1028 impl fmt::Debug for Symbol {
1029     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1030         self.with(|str| fmt::Debug::fmt(&str, f))
1031     }
1032 }
1033
1034 impl fmt::Display for Symbol {
1035     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1036         self.with(|str| fmt::Display::fmt(&str, f))
1037     }
1038 }
1039
1040 impl Encodable for Symbol {
1041     fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
1042         self.with(|string| s.emit_str(string))
1043     }
1044 }
1045
1046 impl Decodable for Symbol {
1047     #[inline]
1048     fn decode<D: Decoder>(d: &mut D) -> Result<Symbol, D::Error> {
1049         Ok(Symbol::intern(&d.read_str()?))
1050     }
1051 }
1052
1053 impl<CTX> HashStable<CTX> for Symbol {
1054     #[inline]
1055     fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
1056         self.as_str().hash_stable(hcx, hasher);
1057     }
1058 }
1059
1060 impl<CTX> ToStableHashKey<CTX> for Symbol {
1061     type KeyType = SymbolStr;
1062
1063     #[inline]
1064     fn to_stable_hash_key(&self, _: &CTX) -> SymbolStr {
1065         self.as_str()
1066     }
1067 }
1068
1069 // The `&'static str`s in this type actually point into the arena.
1070 #[derive(Default)]
1071 pub struct Interner {
1072     arena: DroplessArena,
1073     names: FxHashMap<&'static str, Symbol>,
1074     strings: Vec<&'static str>,
1075 }
1076
1077 impl Interner {
1078     fn prefill(init: &[&'static str]) -> Self {
1079         Interner {
1080             strings: init.into(),
1081             names: init.iter().copied().zip((0..).map(Symbol::new)).collect(),
1082             ..Default::default()
1083         }
1084     }
1085
1086     #[inline]
1087     pub fn intern(&mut self, string: &str) -> Symbol {
1088         if let Some(&name) = self.names.get(string) {
1089             return name;
1090         }
1091
1092         let name = Symbol::new(self.strings.len() as u32);
1093
1094         // `from_utf8_unchecked` is safe since we just allocated a `&str` which is known to be
1095         // UTF-8.
1096         let string: &str =
1097             unsafe { str::from_utf8_unchecked(self.arena.alloc_slice(string.as_bytes())) };
1098         // It is safe to extend the arena allocation to `'static` because we only access
1099         // these while the arena is still alive.
1100         let string: &'static str = unsafe { &*(string as *const str) };
1101         self.strings.push(string);
1102         self.names.insert(string, name);
1103         name
1104     }
1105
1106     // Get the symbol as a string. `Symbol::as_str()` should be used in
1107     // preference to this function.
1108     pub fn get(&self, symbol: Symbol) -> &str {
1109         self.strings[symbol.0.as_usize()]
1110     }
1111 }
1112
1113 // This module has a very short name because it's used a lot.
1114 pub mod kw {
1115     use super::Symbol;
1116     keywords!();
1117 }
1118
1119 // This module has a very short name because it's used a lot.
1120 #[allow(rustc::default_hash_types)]
1121 pub mod sym {
1122     use super::Symbol;
1123     use std::convert::TryInto;
1124
1125     symbols!();
1126
1127     // Used from a macro in `librustc_feature/accepted.rs`
1128     pub use super::kw::MacroRules as macro_rules;
1129
1130     // Get the symbol for an integer. The first few non-negative integers each
1131     // have a static symbol and therefore are fast.
1132     pub fn integer<N: TryInto<usize> + Copy + ToString>(n: N) -> Symbol {
1133         if let Result::Ok(idx) = n.try_into() {
1134             if let Option::Some(&sym) = digits_array.get(idx) {
1135                 return sym;
1136             }
1137         }
1138         Symbol::intern(&n.to_string())
1139     }
1140 }
1141
1142 impl Symbol {
1143     fn is_used_keyword_2018(self) -> bool {
1144         self >= kw::Async && self <= kw::Dyn
1145     }
1146
1147     fn is_unused_keyword_2018(self) -> bool {
1148         self == kw::Try
1149     }
1150
1151     /// Used for sanity checking rustdoc keyword sections.
1152     pub fn is_doc_keyword(self) -> bool {
1153         self <= kw::Union
1154     }
1155
1156     /// A keyword or reserved identifier that can be used as a path segment.
1157     pub fn is_path_segment_keyword(self) -> bool {
1158         self == kw::Super
1159             || self == kw::SelfLower
1160             || self == kw::SelfUpper
1161             || self == kw::Crate
1162             || self == kw::PathRoot
1163             || self == kw::DollarCrate
1164     }
1165
1166     /// Returns `true` if the symbol is `true` or `false`.
1167     pub fn is_bool_lit(self) -> bool {
1168         self == kw::True || self == kw::False
1169     }
1170
1171     /// This symbol can be a raw identifier.
1172     pub fn can_be_raw(self) -> bool {
1173         self != kw::Invalid && self != kw::Underscore && !self.is_path_segment_keyword()
1174     }
1175 }
1176
1177 impl Ident {
1178     // Returns `true` for reserved identifiers used internally for elided lifetimes,
1179     // unnamed method parameters, crate root module, error recovery etc.
1180     pub fn is_special(self) -> bool {
1181         self.name <= kw::Underscore
1182     }
1183
1184     /// Returns `true` if the token is a keyword used in the language.
1185     pub fn is_used_keyword(self) -> bool {
1186         // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
1187         self.name >= kw::As && self.name <= kw::While
1188             || self.name.is_used_keyword_2018() && self.span.rust_2018()
1189     }
1190
1191     /// Returns `true` if the token is a keyword reserved for possible future use.
1192     pub fn is_unused_keyword(self) -> bool {
1193         // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
1194         self.name >= kw::Abstract && self.name <= kw::Yield
1195             || self.name.is_unused_keyword_2018() && self.span.rust_2018()
1196     }
1197
1198     /// Returns `true` if the token is either a special identifier or a keyword.
1199     pub fn is_reserved(self) -> bool {
1200         self.is_special() || self.is_used_keyword() || self.is_unused_keyword()
1201     }
1202
1203     /// A keyword or reserved identifier that can be used as a path segment.
1204     pub fn is_path_segment_keyword(self) -> bool {
1205         self.name.is_path_segment_keyword()
1206     }
1207
1208     /// We see this identifier in a normal identifier position, like variable name or a type.
1209     /// How was it written originally? Did it use the raw form? Let's try to guess.
1210     pub fn is_raw_guess(self) -> bool {
1211         self.name.can_be_raw() && self.is_reserved()
1212     }
1213 }
1214
1215 #[inline]
1216 fn with_interner<T, F: FnOnce(&mut Interner) -> T>(f: F) -> T {
1217     GLOBALS.with(|globals| f(&mut *globals.symbol_interner.lock()))
1218 }
1219
1220 /// An alternative to `Symbol`, useful when the chars within the symbol need to
1221 /// be accessed. It deliberately has limited functionality and should only be
1222 /// used for temporary values.
1223 ///
1224 /// Because the interner outlives any thread which uses this type, we can
1225 /// safely treat `string` which points to interner data, as an immortal string,
1226 /// as long as this type never crosses between threads.
1227 //
1228 // FIXME: ensure that the interner outlives any thread which uses `SymbolStr`,
1229 // by creating a new thread right after constructing the interner.
1230 #[derive(Clone, Eq, PartialOrd, Ord)]
1231 pub struct SymbolStr {
1232     string: &'static str,
1233 }
1234
1235 // This impl allows a `SymbolStr` to be directly equated with a `String` or
1236 // `&str`.
1237 impl<T: std::ops::Deref<Target = str>> std::cmp::PartialEq<T> for SymbolStr {
1238     fn eq(&self, other: &T) -> bool {
1239         self.string == other.deref()
1240     }
1241 }
1242
1243 impl !Send for SymbolStr {}
1244 impl !Sync for SymbolStr {}
1245
1246 /// This impl means that if `ss` is a `SymbolStr`:
1247 /// - `*ss` is a `str`;
1248 /// - `&*ss` is a `&str`;
1249 /// - `&ss as &str` is a `&str`, which means that `&ss` can be passed to a
1250 ///   function expecting a `&str`.
1251 impl std::ops::Deref for SymbolStr {
1252     type Target = str;
1253     #[inline]
1254     fn deref(&self) -> &str {
1255         self.string
1256     }
1257 }
1258
1259 impl fmt::Debug for SymbolStr {
1260     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1261         fmt::Debug::fmt(self.string, f)
1262     }
1263 }
1264
1265 impl fmt::Display for SymbolStr {
1266     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1267         fmt::Display::fmt(self.string, f)
1268     }
1269 }
1270
1271 impl<CTX> HashStable<CTX> for SymbolStr {
1272     #[inline]
1273     fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
1274         self.string.hash_stable(hcx, hasher)
1275     }
1276 }
1277
1278 impl<CTX> ToStableHashKey<CTX> for SymbolStr {
1279     type KeyType = SymbolStr;
1280
1281     #[inline]
1282     fn to_stable_hash_key(&self, _: &CTX) -> SymbolStr {
1283         self.clone()
1284     }
1285 }