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         abort,
 124         aborts,
 125         address,
 126         add_with_overflow,
 127         advanced_slice_patterns,
 128         adx_target_feature,
 129         alias,
 130         align,
 131         alignstack,
 132         all,
 133         allocator,
 134         allocator_internals,
 135         alloc_error_handler,
 136         allow,
 137         allowed,
 138         allow_fail,
 139         allow_internal_unsafe,
 140         allow_internal_unstable,
 141         allow_internal_unstable_backcompat_hack,
 142         always,
 143         and,
 144         any,
 145         arbitrary_enum_discriminant,
 146         arbitrary_self_types,
 147         Arc,
 148         Arguments,
 149         ArgumentV1,
 150         arm_target_feature,
 151         asm,
 152         assert,
 153         associated_consts,
 154         associated_type_bounds,
 155         associated_type_defaults,
 156         associated_types,
 157         assume_init,
 158         async_await,
 159         async_closure,
 160         attr,
 161         attributes,
 162         attr_literals,
 163         augmented_assignments,
 164         automatically_derived,
 165         avx512_target_feature,
 166         await_macro,
 167         begin_panic,
 168         bench,
 169         bin,
 170         bind_by_move_pattern_guards,
 171         bindings_after_at,
 172         block,
 173         bool,
 174         borrowck_graphviz_format,
 175         borrowck_graphviz_postflow,
 176         borrowck_graphviz_preflow,
 177         box_patterns,
 178         box_syntax,
 179         braced_empty_structs,
 180         bswap,
 181         bitreverse,
 182         C,
 183         caller_location,
 184         cdylib,
 185         cfg,
 186         cfg_accessible,
 187         cfg_attr,
 188         cfg_attr_multi,
 189         cfg_doctest,
 190         cfg_sanitize,
 191         cfg_target_feature,
 192         cfg_target_has_atomic,
 193         cfg_target_thread_local,
 194         cfg_target_vendor,
 195         char,
 196         clippy,
 197         clone,
 198         Clone,
 199         clone_closures,
 200         clone_from,
 201         closure_to_fn_coercion,
 202         cmp,
 203         cmpxchg16b_target_feature,
 204         cold,
 205         column,
 206         compile_error,
 207         compiler_builtins,
 208         concat,
 209         concat_idents,
 210         conservative_impl_trait,
 211         console,
 212         const_compare_raw_pointers,
 213         const_constructor,
 214         const_eval_limit,
 215         const_extern_fn,
 216         const_fn,
 217         const_fn_union,
 218         const_generics,
 219         const_if_match,
 220         const_indexing,
 221         const_in_array_repeat_expressions,
 222         const_let,
 223         const_loop,
 224         const_mut_refs,
 225         const_panic,
 226         const_raw_ptr_deref,
 227         const_raw_ptr_to_usize_cast,
 228         const_transmute,
 229         const_trait_bound_opt_out,
 230         const_trait_impl,
 231         contents,
 232         context,
 233         convert,
 234         Copy,
 235         copy_closures,
 236         core,
 237         core_intrinsics,
 238         crate_id,
 239         crate_in_paths,
 240         crate_local,
 241         crate_name,
 242         crate_type,
 243         crate_visibility_modifier,
 244         ctpop,
 245         cttz,
 246         cttz_nonzero,
 247         ctlz,
 248         ctlz_nonzero,
 249         custom_attribute,
 250         custom_derive,
 251         custom_inner_attributes,
 252         custom_test_frameworks,
 253         c_variadic,
 254         debug_trait,
 255         declare_lint_pass,
 256         decl_macro,
 257         debug,
 258         Debug,
 259         Decodable,
 260         Default,
 261         default_lib_allocator,
 262         default_type_parameter_fallback,
 263         default_type_params,
 264         delay_span_bug_from_inside_query,
 265         deny,
 266         deprecated,
 267         deref,
 268         deref_mut,
 269         derive,
 270         diagnostic,
 271         direct,
 272         discriminant_value,
 273         doc,
 274         doc_alias,
 275         doc_cfg,
 276         doc_keyword,
 277         doc_masked,
 278         doctest,
 279         document_private_items,
 280         dotdoteq_in_patterns,
 281         dotdot_in_tuple_patterns,
 282         double_braced_crate: "{{crate}}",
 283         double_braced_impl: "{{impl}}",
 284         double_braced_misc: "{{misc}}",
 285         double_braced_closure: "{{closure}}",
 286         double_braced_constructor: "{{constructor}}",
 287         double_braced_constant: "{{constant}}",
 288         double_braced_opaque: "{{opaque}}",
 289         dropck_eyepatch,
 290         dropck_parametricity,
 291         drop_types_in_const,
 292         dylib,
 293         dyn_trait,
 294         eh_personality,
 295         enable,
 296         Encodable,
 297         env,
 298         eq,
 299         err,
 300         Err,
 301         Eq,
 302         Equal,
 303         enclosing_scope,
 304         except,
 305         exclusive_range_pattern,
 306         exhaustive_integer_patterns,
 307         exhaustive_patterns,
 308         existential_type,
 309         expected,
 310         export_name,
 311         expr,
 312         extern_absolute_paths,
 313         external_doc,
 314         extern_crate_item_prelude,
 315         extern_crate_self,
 316         extern_in_paths,
 317         extern_prelude,
 318         extern_types,
 319         f16c_target_feature,
 320         f32,
 321         f64,
 322         feature,
 323         ffi_returns_twice,
 324         field,
 325         field_init_shorthand,
 326         file,
 327         fmt,
 328         fmt_internals,
 329         fn_must_use,
 330         forbid,
 331         format_args,
 332         format_args_nl,
 333         from,
 334         From,
 335         from_desugaring,
 336         from_error,
 337         from_generator,
 338         from_method,
 339         from_ok,
 340         from_usize,
 341         fundamental,
 342         future,
 343         Future,
 344         FxHashSet,
 345         FxHashMap,
 346         gen_future,
 347         gen_kill,
 348         generators,
 349         generic_associated_types,
 350         generic_param_attrs,
 351         get_context,
 352         global_allocator,
 353         global_asm,
 354         globs,
 355         half_open_range_patterns,
 356         hash,
 357         Hash,
 358         HashSet,
 359         HashMap,
 360         hexagon_target_feature,
 361         hidden,
 362         homogeneous_aggregate,
 363         html_favicon_url,
 364         html_logo_url,
 365         html_no_source,
 366         html_playground_url,
 367         html_root_url,
 368         i128,
 369         i128_type,
 370         i16,
 371         i32,
 372         i64,
 373         i8,
 374         ident,
 375         if_let,
 376         if_while_or_patterns,
 377         ignore,
 378         impl_header_lifetime_elision,
 379         impl_lint_pass,
 380         impl_trait_in_bindings,
 381         import_shadowing,
 382         index,
 383         index_mut,
 384         in_band_lifetimes,
 385         include,
 386         include_bytes,
 387         include_str,
 388         inclusive_range_syntax,
 389         infer_outlives_requirements,
 390         infer_static_outlives_requirements,
 391         inline,
 392         intel,
 393         into_iter,
 394         IntoIterator,
 395         into_result,
 396         intrinsics,
 397         irrefutable_let_patterns,
 398         isize,
 399         issue,
 400         issue_5723_bootstrap,
 401         issue_tracker_base_url,
 402         item,
 403         item_context: "ItemContext",
 404         item_like_imports,
 405         iter,
 406         Iterator,
 407         keyword,
 408         kind,
 409         label,
 410         label_break_value,
 411         lang,
 412         lang_items,
 413         let_chains,
 414         lhs,
 415         lib,
 416         lifetime,
 417         line,
 418         link,
 419         linkage,
 420         link_args,
 421         link_cfg,
 422         link_llvm_intrinsics,
 423         link_name,
 424         link_ordinal,
 425         link_section,
 426         LintPass,
 427         lint_reasons,
 428         literal,
 429         llvm_asm,
 430         local_inner_macros,
 431         log_syntax,
 432         loop_break_value,
 433         macro_at_most_once_rep,
 434         macro_escape,
 435         macro_export,
 436         macro_lifetime_matcher,
 437         macro_literal_matcher,
 438         macro_reexport,
 439         macros_in_extern,
 440         macro_use,
 441         macro_vis_matcher,
 442         main,
 443         managed_boxes,
 444         marker,
 445         marker_trait_attr,
 446         masked,
 447         match_beginning_vert,
 448         match_default_bindings,
 449         may_dangle,
 450         maybe_uninit_uninit,
 451         maybe_uninit_zeroed,
 452         mem_uninitialized,
 453         mem_zeroed,
 454         member_constraints,
 455         memory,
 456         message,
 457         meta,
 458         min_align_of,
 459         min_const_fn,
 460         min_const_unsafe_fn,
 461         min_specialization,
 462         mips_target_feature,
 463         mmx_target_feature,
 464         module,
 465         module_path,
 466         more_struct_aliases,
 467         move_ref_pattern,
 468         move_val_init,
 469         movbe_target_feature,
 470         mul_with_overflow,
 471         must_use,
 472         naked,
 473         naked_functions,
 474         name,
 475         needs_allocator,
 476         needs_drop,
 477         needs_panic_runtime,
 478         negate_unsigned,
 479         negative_impls,
 480         never,
 481         never_type,
 482         never_type_fallback,
 483         new,
 484         next,
 485         __next,
 486         nll,
 487         no_builtins,
 488         no_core,
 489         no_crate_inject,
 490         no_debug,
 491         no_default_passes,
 492         no_implicit_prelude,
 493         no_inline,
 494         no_link,
 495         no_main,
 496         no_mangle,
 497         non_ascii_idents,
 498         None,
 499         non_exhaustive,
 500         non_modrs_mods,
 501         no_sanitize,
 502         no_niche,
 503         no_stack_check,
 504         no_start,
 505         no_std,
 506         not,
 507         note,
 508         object_safe_for_dispatch,
 509         Ok,
 510         omit_gdb_pretty_printer_section,
 511         on,
 512         on_unimplemented,
 513         oom,
 514         ops,
 515         optimize,
 516         optimize_attribute,
 517         optin_builtin_traits,
 518         option,
 519         Option,
 520         option_env,
 521         opt_out_copy,
 522         or,
 523         or_patterns,
 524         Ord,
 525         Ordering,
 526         Output,
 527         overlapping_marker_traits,
 528         packed,
 529         panic,
 530         panic_handler,
 531         panic_impl,
 532         panic_implementation,
 533         panic_runtime,
 534         parent_trait,
 535         partial_cmp,
 536         param_attrs,
 537         PartialEq,
 538         PartialOrd,
 539         passes,
 540         pat,
 541         path,
 542         pattern_parentheses,
 543         Pending,
 544         pin,
 545         Pin,
 546         pinned,
 547         platform_intrinsics,
 548         plugin,
 549         plugin_registrar,
 550         plugins,
 551         poll,
 552         Poll,
 553         powerpc_target_feature,
 554         precise_pointer_size_matching,
 555         pref_align_of,
 556         prelude,
 557         prelude_import,
 558         primitive,
 559         proc_dash_macro: "proc-macro",
 560         proc_macro,
 561         proc_macro_attribute,
 562         proc_macro_def_site,
 563         proc_macro_derive,
 564         proc_macro_expr,
 565         proc_macro_gen,
 566         proc_macro_hygiene,
 567         proc_macro_internals,
 568         proc_macro_mod,
 569         proc_macro_non_items,
 570         proc_macro_path_invoc,
 571         profiler_runtime,
 572         ptr_offset_from,
 573         pub_restricted,
 574         pushpop_unsafe,
 575         quad_precision_float,
 576         question_mark,
 577         quote,
 578         Range,
 579         RangeFrom,
 580         RangeFull,
 581         RangeInclusive,
 582         RangeTo,
 583         RangeToInclusive,
 584         raw_dylib,
 585         raw_identifiers,
 586         raw_ref_op,
 587         Rc,
 588         Ready,
 589         reason,
 590         recursion_limit,
 591         reexport_test_harness_main,
 592         reflect,
 593         register_attr,
 594         register_tool,
 595         relaxed_adts,
 596         repr,
 597         repr128,
 598         repr_align,
 599         repr_align_enum,
 600         repr_no_niche,
 601         repr_packed,
 602         repr_simd,
 603         repr_transparent,
 604         re_rebalance_coherence,
 605         result,
 606         Result,
 607         Return,
 608         rhs,
 609         rlib,
 610         rotate_left,
 611         rotate_right,
 612         rt,
 613         rtm_target_feature,
 614         rust,
 615         rust_2015_preview,
 616         rust_2018_preview,
 617         rust_begin_unwind,
 618         rustc,
 619         RustcDecodable,
 620         RustcEncodable,
 621         rustc_allocator,
 622         rustc_allocator_nounwind,
 623         rustc_allow_const_fn_ptr,
 624         rustc_args_required_const,
 625         rustc_attrs,
 626         rustc_builtin_macro,
 627         rustc_clean,
 628         rustc_const_unstable,
 629         rustc_const_stable,
 630         rustc_conversion_suggestion,
 631         rustc_def_path,
 632         rustc_deprecated,
 633         rustc_diagnostic_item,
 634         rustc_diagnostic_macros,
 635         rustc_dirty,
 636         rustc_dummy,
 637         rustc_dump_env_program_clauses,
 638         rustc_dump_program_clauses,
 639         rustc_dump_user_substs,
 640         rustc_error,
 641         rustc_expected_cgu_reuse,
 642         rustc_if_this_changed,
 643         rustc_inherit_overflow_checks,
 644         rustc_layout,
 645         rustc_layout_scalar_valid_range_end,
 646         rustc_layout_scalar_valid_range_start,
 647         rustc_macro_transparency,
 648         rustc_mir,
 649         rustc_nonnull_optimization_guaranteed,
 650         rustc_object_lifetime_default,
 651         rustc_on_unimplemented,
 652         rustc_outlives,
 653         rustc_paren_sugar,
 654         rustc_partition_codegened,
 655         rustc_partition_reused,
 656         rustc_peek,
 657         rustc_peek_definite_init,
 658         rustc_peek_maybe_init,
 659         rustc_peek_maybe_uninit,
 660         rustc_peek_indirectly_mutable,
 661         rustc_private,
 662         rustc_proc_macro_decls,
 663         rustc_promotable,
 664         rustc_regions,
 665         rustc_unsafe_specialization_marker,
 666         rustc_specialization_trait,
 667         rustc_stable,
 668         rustc_std_internal_symbol,
 669         rustc_symbol_name,
 670         rustc_synthetic,
 671         rustc_reservation_impl,
 672         rustc_test_marker,
 673         rustc_then_this_would_need,
 674         rustc_variance,
 675         rustfmt,
 676         rust_eh_personality,
 677         rust_oom,
 678         rvalue_static_promotion,
 679         sanitize,
 680         sanitizer_runtime,
 681         saturating_add,
 682         saturating_sub,
 683         _Self,
 684         self_in_typedefs,
 685         self_struct_ctor,
 686         send_trait,
 687         should_panic,
 688         simd,
 689         simd_extract,
 690         simd_ffi,
 691         simd_insert,
 692         since,
 693         size,
 694         size_of,
 695         slice_patterns,
 696         slicing_syntax,
 697         soft,
 698         Some,
 699         specialization,
 700         speed,
 701         sse4a_target_feature,
 702         stable,
 703         staged_api,
 704         start,
 705         static_in_const,
 706         staticlib,
 707         static_nobundle,
 708         static_recursion,
 709         std,
 710         std_inject,
 711         str,
 712         stringify,
 713         stmt,
 714         stmt_expr_attributes,
 715         stop_after_dataflow,
 716         struct_field_attributes,
 717         struct_inherit,
 718         structural_match,
 719         struct_variant,
 720         sty,
 721         sub_with_overflow,
 722         suggestion,
 723         sync_trait,
 724         target_feature,
 725         target_has_atomic,
 726         target_has_atomic_load_store,
 727         target_thread_local,
 728         task,
 729         _task_context,
 730         tbm_target_feature,
 731         termination_trait,
 732         termination_trait_test,
 733         test,
 734         test_2018_feature,
 735         test_accepted_feature,
 736         test_case,
 737         test_removed_feature,
 738         test_runner,
 739         then_with,
 740         thread,
 741         thread_local,
 742         tool_attributes,
 743         tool_lints,
 744         trace_macros,
 745         track_caller,
 746         trait_alias,
 747         transmute,
 748         transparent,
 749         transparent_enums,
 750         transparent_unions,
 751         trivial_bounds,
 752         Try,
 753         try_blocks,
 754         try_trait,
 755         tt,
 756         tuple_indexing,
 757         two_phase,
 758         Ty,
 759         ty,
 760         type_alias_impl_trait,
 761         type_id,
 762         type_name,
 763         TyCtxt,
 764         TyKind,
 765         type_alias_enum_variants,
 766         type_ascription,
 767         type_length_limit,
 768         type_macros,
 769         u128,
 770         u16,
 771         u32,
 772         u64,
 773         u8,
 774         unboxed_closures,
 775         unchecked_add,
 776         unchecked_div,
 777         unchecked_mul,
 778         unchecked_rem,
 779         unchecked_shl,
 780         unchecked_shr,
 781         unchecked_sub,
 782         underscore_const_names,
 783         underscore_imports,
 784         underscore_lifetimes,
 785         uniform_paths,
 786         universal_impl_trait,
 787         unmarked_api,
 788         unreachable_code,
 789         unrestricted_attribute_tokens,
 790         unsafe_no_drop_flag,
 791         unsized_locals,
 792         unsized_tuple_coercion,
 793         unstable,
 794         untagged_unions,
 795         unwind,
 796         unwind_attributes,
 797         unwrap_or,
 798         used,
 799         use_extern_macros,
 800         use_nested_groups,
 801         usize,
 802         v1,
 803         val,
 804         var,
 805         vec,
 806         Vec,
 807         vis,
 808         visible_private_types,
 809         volatile,
 810         warn,
 811         wasm_import_module,
 812         wasm_target_feature,
 813         while_let,
 814         windows,
 815         windows_subsystem,
 816         wrapping_add,
 817         wrapping_sub,
 818         wrapping_mul,
 819         Yield,
 820     }
 821 }
 822
 823 #[derive(Copy, Clone, Eq, HashStable_Generic)]
 824 pub struct Ident {
 825     pub name: Symbol,
 826     pub span: Span,
 827 }
 828
 829 impl Ident {
 830     #[inline]
 831     /// Constructs a new identifier from a symbol and a span.
 832     pub const fn new(name: Symbol, span: Span) -> Ident {
 833         Ident { name, span }
 834     }
 835
 836     /// Constructs a new identifier with a dummy span.
 837     #[inline]
 838     pub const fn with_dummy_span(name: Symbol) -> Ident {
 839         Ident::new(name, DUMMY_SP)
 840     }
 841
 842     #[inline]
 843     pub fn invalid() -> Ident {
 844         Ident::with_dummy_span(kw::Invalid)
 845     }
 846
 847     /// Maps a string to an identifier with a dummy span.
 848     pub fn from_str(string: &str) -> Ident {
 849         Ident::with_dummy_span(Symbol::intern(string))
 850     }
 851
 852     /// Maps a string and a span to an identifier.
 853     pub fn from_str_and_span(string: &str, span: Span) -> Ident {
 854         Ident::new(Symbol::intern(string), span)
 855     }
 856
 857     /// Replaces `lo` and `hi` with those from `span`, but keep hygiene context.
 858     pub fn with_span_pos(self, span: Span) -> Ident {
 859         Ident::new(self.name, span.with_ctxt(self.span.ctxt()))
 860     }
 861
 862     pub fn without_first_quote(self) -> Ident {
 863         Ident::new(Symbol::intern(self.as_str().trim_start_matches('\'')), self.span)
 864     }
 865
 866     /// "Normalize" ident for use in comparisons using "item hygiene".
 867     /// Identifiers with same string value become same if they came from the same macro 2.0 macro
 868     /// (e.g., `macro` item, but not `macro_rules` item) and stay different if they came from
 869     /// different macro 2.0 macros.
 870     /// Technically, this operation strips all non-opaque marks from ident's syntactic context.
 871     pub fn normalize_to_macros_2_0(self) -> Ident {
 872         Ident::new(self.name, self.span.normalize_to_macros_2_0())
 873     }
 874
 875     /// "Normalize" ident for use in comparisons using "local variable hygiene".
 876     /// Identifiers with same string value become same if they came from the same non-transparent
 877     /// macro (e.g., `macro` or `macro_rules!` items) and stay different if they came from different
 878     /// non-transparent macros.
 879     /// Technically, this operation strips all transparent marks from ident's syntactic context.
 880     pub fn normalize_to_macro_rules(self) -> Ident {
 881         Ident::new(self.name, self.span.normalize_to_macro_rules())
 882     }
 883
 884     /// Convert the name to a `SymbolStr`. This is a slowish operation because
 885     /// it requires locking the symbol interner.
 886     pub fn as_str(self) -> SymbolStr {
 887         self.name.as_str()
 888     }
 889 }
 890
 891 impl PartialEq for Ident {
 892     fn eq(&self, rhs: &Self) -> bool {
 893         self.name == rhs.name && self.span.ctxt() == rhs.span.ctxt()
 894     }
 895 }
 896
 897 impl Hash for Ident {
 898     fn hash<H: Hasher>(&self, state: &mut H) {
 899         self.name.hash(state);
 900         self.span.ctxt().hash(state);
 901     }
 902 }
 903
 904 impl fmt::Debug for Ident {
 905     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 906         fmt::Display::fmt(self, f)?;
 907         fmt::Debug::fmt(&self.span.ctxt(), f)
 908     }
 909 }
 910
 911 /// This implementation is supposed to be used in error messages, so it's expected to be identical
 912 /// to printing the original identifier token written in source code (`token_to_string`),
 913 /// except that AST identifiers don't keep the rawness flag, so we have to guess it.
 914 impl fmt::Display for Ident {
 915     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 916         fmt::Display::fmt(&IdentPrinter::new(self.name, self.is_raw_guess(), None), f)
 917     }
 918 }
 919
 920 impl UseSpecializedEncodable for Ident {
 921     fn default_encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
 922         s.emit_struct("Ident", 2, |s| {
 923             s.emit_struct_field("name", 0, |s| self.name.encode(s))?;
 924             s.emit_struct_field("span", 1, |s| self.span.encode(s))
 925         })
 926     }
 927 }
 928
 929 impl UseSpecializedDecodable for Ident {
 930     fn default_decode<D: Decoder>(d: &mut D) -> Result<Self, D::Error> {
 931         d.read_struct("Ident", 2, |d| {
 932             Ok(Ident {
 933                 name: d.read_struct_field("name", 0, Decodable::decode)?,
 934                 span: d.read_struct_field("span", 1, Decodable::decode)?,
 935             })
 936         })
 937     }
 938 }
 939
 940 /// This is the most general way to print identifiers.
 941 /// AST pretty-printer is used as a fallback for turning AST structures into token streams for
 942 /// proc macros. Additionally, proc macros may stringify their input and expect it survive the
 943 /// stringification (especially true for proc macro derives written between Rust 1.15 and 1.30).
 944 /// So we need to somehow pretty-print `$crate` in a way preserving at least some of its
 945 /// hygiene data, most importantly name of the crate it refers to.
 946 /// As a result we print `$crate` as `crate` if it refers to the local crate
 947 /// and as `::other_crate_name` if it refers to some other crate.
 948 /// Note, that this is only done if the ident token is printed from inside of AST pretty-pringing,
 949 /// but not otherwise. Pretty-printing is the only way for proc macros to discover token contents,
 950 /// so we should not perform this lossy conversion if the top level call to the pretty-printer was
 951 /// done for a token stream or a single token.
 952 pub struct IdentPrinter {
 953     symbol: Symbol,
 954     is_raw: bool,
 955     /// Span used for retrieving the crate name to which `$crate` refers to,
 956     /// if this field is `None` then the `$crate` conversion doesn't happen.
 957     convert_dollar_crate: Option<Span>,
 958 }
 959
 960 impl IdentPrinter {
 961     /// The most general `IdentPrinter` constructor. Do not use this.
 962     pub fn new(symbol: Symbol, is_raw: bool, convert_dollar_crate: Option<Span>) -> IdentPrinter {
 963         IdentPrinter { symbol, is_raw, convert_dollar_crate }
 964     }
 965
 966     /// This implementation is supposed to be used when printing identifiers
 967     /// as a part of pretty-printing for larger AST pieces.
 968     /// Do not use this either.
 969     pub fn for_ast_ident(ident: Ident, is_raw: bool) -> IdentPrinter {
 970         IdentPrinter::new(ident.name, is_raw, Some(ident.span))
 971     }
 972 }
 973
 974 impl fmt::Display for IdentPrinter {
 975     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 976         if self.is_raw {
 977             f.write_str("r#")?;
 978         } else {
 979             if self.symbol == kw::DollarCrate {
 980                 if let Some(span) = self.convert_dollar_crate {
 981                     let converted = span.ctxt().dollar_crate_name();
 982                     if !converted.is_path_segment_keyword() {
 983                         f.write_str("::")?;
 984                     }
 985                     return fmt::Display::fmt(&converted, f);
 986                 }
 987             }
 988         }
 989         fmt::Display::fmt(&self.symbol, f)
 990     }
 991 }
 992
 993 /// An newtype around `Ident` that calls [Ident::normalize_to_macro_rules] on
 994 /// construction.
 995 // FIXME(matthewj, petrochenkov) Use this more often, add a similar
 996 // `ModernIdent` struct and use that as well.
 997 #[derive(Copy, Clone, Eq, PartialEq, Hash)]
 998 pub struct MacroRulesNormalizedIdent(Ident);
 999
1000 impl MacroRulesNormalizedIdent {
1001     pub fn new(ident: Ident) -> Self {
1002         Self(ident.normalize_to_macro_rules())
1003     }
1004 }
1005
1006 impl fmt::Debug for MacroRulesNormalizedIdent {
1007     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1008         fmt::Debug::fmt(&self.0, f)
1009     }
1010 }
1011
1012 impl fmt::Display for MacroRulesNormalizedIdent {
1013     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1014         fmt::Display::fmt(&self.0, f)
1015     }
1016 }
1017
1018 /// An interned string.
1019 ///
1020 /// Internally, a `Symbol` is implemented as an index, and all operations
1021 /// (including hashing, equality, and ordering) operate on that index. The use
1022 /// of `rustc_index::newtype_index!` means that `Option<Symbol>` only takes up 4 bytes,
1023 /// because `rustc_index::newtype_index!` reserves the last 256 values for tagging purposes.
1024 ///
1025 /// Note that `Symbol` cannot directly be a `rustc_index::newtype_index!` because it
1026 /// implements `fmt::Debug`, `Encodable`, and `Decodable` in special ways.
1027 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
1028 pub struct Symbol(SymbolIndex);
1029
1030 rustc_index::newtype_index! {
1031     pub struct SymbolIndex { .. }
1032 }
1033
1034 impl Symbol {
1035     const fn new(n: u32) -> Self {
1036         Symbol(SymbolIndex::from_u32(n))
1037     }
1038
1039     /// Maps a string to its interned representation.
1040     pub fn intern(string: &str) -> Self {
1041         with_interner(|interner| interner.intern(string))
1042     }
1043
1044     /// Access the symbol's chars. This is a slowish operation because it
1045     /// requires locking the symbol interner.
1046     pub fn with<F: FnOnce(&str) -> R, R>(self, f: F) -> R {
1047         with_interner(|interner| f(interner.get(self)))
1048     }
1049
1050     /// Convert to a `SymbolStr`. This is a slowish operation because it
1051     /// requires locking the symbol interner.
1052     pub fn as_str(self) -> SymbolStr {
1053         with_interner(|interner| unsafe {
1054             SymbolStr { string: std::mem::transmute::<&str, &str>(interner.get(self)) }
1055         })
1056     }
1057
1058     pub fn as_u32(self) -> u32 {
1059         self.0.as_u32()
1060     }
1061
1062     /// This method is supposed to be used in error messages, so it's expected to be
1063     /// identical to printing the original identifier token written in source code
1064     /// (`token_to_string`, `Ident::to_string`), except that symbols don't keep the rawness flag
1065     /// or edition, so we have to guess the rawness using the global edition.
1066     pub fn to_ident_string(self) -> String {
1067         Ident::with_dummy_span(self).to_string()
1068     }
1069 }
1070
1071 impl fmt::Debug for Symbol {
1072     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1073         self.with(|str| fmt::Debug::fmt(&str, f))
1074     }
1075 }
1076
1077 impl fmt::Display for Symbol {
1078     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1079         self.with(|str| fmt::Display::fmt(&str, f))
1080     }
1081 }
1082
1083 impl Encodable for Symbol {
1084     fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
1085         self.with(|string| s.emit_str(string))
1086     }
1087 }
1088
1089 impl Decodable for Symbol {
1090     #[inline]
1091     fn decode<D: Decoder>(d: &mut D) -> Result<Symbol, D::Error> {
1092         Ok(Symbol::intern(&d.read_str()?))
1093     }
1094 }
1095
1096 impl<CTX> HashStable<CTX> for Symbol {
1097     #[inline]
1098     fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
1099         self.as_str().hash_stable(hcx, hasher);
1100     }
1101 }
1102
1103 impl<CTX> ToStableHashKey<CTX> for Symbol {
1104     type KeyType = SymbolStr;
1105
1106     #[inline]
1107     fn to_stable_hash_key(&self, _: &CTX) -> SymbolStr {
1108         self.as_str()
1109     }
1110 }
1111
1112 // The `&'static str`s in this type actually point into the arena.
1113 #[derive(Default)]
1114 pub struct Interner {
1115     arena: DroplessArena,
1116     names: FxHashMap<&'static str, Symbol>,
1117     strings: Vec<&'static str>,
1118 }
1119
1120 impl Interner {
1121     fn prefill(init: &[&'static str]) -> Self {
1122         Interner {
1123             strings: init.into(),
1124             names: init.iter().copied().zip((0..).map(Symbol::new)).collect(),
1125             ..Default::default()
1126         }
1127     }
1128
1129     #[inline]
1130     pub fn intern(&mut self, string: &str) -> Symbol {
1131         if let Some(&name) = self.names.get(string) {
1132             return name;
1133         }
1134
1135         let name = Symbol::new(self.strings.len() as u32);
1136
1137         // `from_utf8_unchecked` is safe since we just allocated a `&str` which is known to be
1138         // UTF-8.
1139         let string: &str =
1140             unsafe { str::from_utf8_unchecked(self.arena.alloc_slice(string.as_bytes())) };
1141         // It is safe to extend the arena allocation to `'static` because we only access
1142         // these while the arena is still alive.
1143         let string: &'static str = unsafe { &*(string as *const str) };
1144         self.strings.push(string);
1145         self.names.insert(string, name);
1146         name
1147     }
1148
1149     // Get the symbol as a string. `Symbol::as_str()` should be used in
1150     // preference to this function.
1151     pub fn get(&self, symbol: Symbol) -> &str {
1152         self.strings[symbol.0.as_usize()]
1153     }
1154 }
1155
1156 // This module has a very short name because it's used a lot.
1157 /// This module contains all the defined keyword `Symbol`s.
1158 ///
1159 /// Given that `kw` is imported, use them like `kw::keyword_name`.
1160 /// For example `kw::Loop` or `kw::Break`.
1161 pub mod kw {
1162     use super::Symbol;
1163     keywords!();
1164 }
1165
1166 // This module has a very short name because it's used a lot.
1167 /// This module contains all the defined non-keyword `Symbol`s.
1168 ///
1169 /// Given that `sym` is imported, use them like `sym::symbol_name`.
1170 /// For example `sym::rustfmt` or `sym::u8`.
1171 #[allow(rustc::default_hash_types)]
1172 pub mod sym {
1173     use super::Symbol;
1174     use std::convert::TryInto;
1175
1176     symbols!();
1177
1178     // Used from a macro in `librustc_feature/accepted.rs`
1179     pub use super::kw::MacroRules as macro_rules;
1180
1181     // Get the symbol for an integer. The first few non-negative integers each
1182     // have a static symbol and therefore are fast.
1183     pub fn integer<N: TryInto<usize> + Copy + ToString>(n: N) -> Symbol {
1184         if let Result::Ok(idx) = n.try_into() {
1185             if let Option::Some(&sym) = digits_array.get(idx) {
1186                 return sym;
1187             }
1188         }
1189         Symbol::intern(&n.to_string())
1190     }
1191 }
1192
1193 impl Symbol {
1194     fn is_used_keyword_2018(self) -> bool {
1195         self >= kw::Async && self <= kw::Dyn
1196     }
1197
1198     fn is_unused_keyword_2018(self) -> bool {
1199         self == kw::Try
1200     }
1201
1202     /// Used for sanity checking rustdoc keyword sections.
1203     pub fn is_doc_keyword(self) -> bool {
1204         self <= kw::Union
1205     }
1206
1207     /// A keyword or reserved identifier that can be used as a path segment.
1208     pub fn is_path_segment_keyword(self) -> bool {
1209         self == kw::Super
1210             || self == kw::SelfLower
1211             || self == kw::SelfUpper
1212             || self == kw::Crate
1213             || self == kw::PathRoot
1214             || self == kw::DollarCrate
1215     }
1216
1217     /// Returns `true` if the symbol is `true` or `false`.
1218     pub fn is_bool_lit(self) -> bool {
1219         self == kw::True || self == kw::False
1220     }
1221
1222     /// This symbol can be a raw identifier.
1223     pub fn can_be_raw(self) -> bool {
1224         self != kw::Invalid && self != kw::Underscore && !self.is_path_segment_keyword()
1225     }
1226 }
1227
1228 impl Ident {
1229     // Returns `true` for reserved identifiers used internally for elided lifetimes,
1230     // unnamed method parameters, crate root module, error recovery etc.
1231     pub fn is_special(self) -> bool {
1232         self.name <= kw::Underscore
1233     }
1234
1235     /// Returns `true` if the token is a keyword used in the language.
1236     pub fn is_used_keyword(self) -> bool {
1237         // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
1238         self.name >= kw::As && self.name <= kw::While
1239             || self.name.is_used_keyword_2018() && self.span.rust_2018()
1240     }
1241
1242     /// Returns `true` if the token is a keyword reserved for possible future use.
1243     pub fn is_unused_keyword(self) -> bool {
1244         // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
1245         self.name >= kw::Abstract && self.name <= kw::Yield
1246             || self.name.is_unused_keyword_2018() && self.span.rust_2018()
1247     }
1248
1249     /// Returns `true` if the token is either a special identifier or a keyword.
1250     pub fn is_reserved(self) -> bool {
1251         self.is_special() || self.is_used_keyword() || self.is_unused_keyword()
1252     }
1253
1254     /// A keyword or reserved identifier that can be used as a path segment.
1255     pub fn is_path_segment_keyword(self) -> bool {
1256         self.name.is_path_segment_keyword()
1257     }
1258
1259     /// We see this identifier in a normal identifier position, like variable name or a type.
1260     /// How was it written originally? Did it use the raw form? Let's try to guess.
1261     pub fn is_raw_guess(self) -> bool {
1262         self.name.can_be_raw() && self.is_reserved()
1263     }
1264 }
1265
1266 #[inline]
1267 fn with_interner<T, F: FnOnce(&mut Interner) -> T>(f: F) -> T {
1268     GLOBALS.with(|globals| f(&mut *globals.symbol_interner.lock()))
1269 }
1270
1271 /// An alternative to `Symbol`, useful when the chars within the symbol need to
1272 /// be accessed. It deliberately has limited functionality and should only be
1273 /// used for temporary values.
1274 ///
1275 /// Because the interner outlives any thread which uses this type, we can
1276 /// safely treat `string` which points to interner data, as an immortal string,
1277 /// as long as this type never crosses between threads.
1278 //
1279 // FIXME: ensure that the interner outlives any thread which uses `SymbolStr`,
1280 // by creating a new thread right after constructing the interner.
1281 #[derive(Clone, Eq, PartialOrd, Ord)]
1282 pub struct SymbolStr {
1283     string: &'static str,
1284 }
1285
1286 // This impl allows a `SymbolStr` to be directly equated with a `String` or
1287 // `&str`.
1288 impl<T: std::ops::Deref<Target = str>> std::cmp::PartialEq<T> for SymbolStr {
1289     fn eq(&self, other: &T) -> bool {
1290         self.string == other.deref()
1291     }
1292 }
1293
1294 impl !Send for SymbolStr {}
1295 impl !Sync for SymbolStr {}
1296
1297 /// This impl means that if `ss` is a `SymbolStr`:
1298 /// - `*ss` is a `str`;
1299 /// - `&*ss` is a `&str`;
1300 /// - `&ss as &str` is a `&str`, which means that `&ss` can be passed to a
1301 ///   function expecting a `&str`.
1302 impl std::ops::Deref for SymbolStr {
1303     type Target = str;
1304     #[inline]
1305     fn deref(&self) -> &str {
1306         self.string
1307     }
1308 }
1309
1310 impl fmt::Debug for SymbolStr {
1311     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1312         fmt::Debug::fmt(self.string, f)
1313     }
1314 }
1315
1316 impl fmt::Display for SymbolStr {
1317     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1318         fmt::Display::fmt(self.string, f)
1319     }
1320 }
1321
1322 impl<CTX> HashStable<CTX> for SymbolStr {
1323     #[inline]
1324     fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
1325         self.string.hash_stable(hcx, hasher)
1326     }
1327 }
1328
1329 impl<CTX> ToStableHashKey<CTX> for SymbolStr {
1330     type KeyType = SymbolStr;
1331
1332     #[inline]
1333     fn to_stable_hash_key(&self, _: &CTX) -> SymbolStr {
1334         self.clone()
1335     }
1336 }