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 rustc_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         abi_avr_interrupt,
 124         abort,
 125         aborts,
 126         address,
 127         add_with_overflow,
 128         advanced_slice_patterns,
 129         adx_target_feature,
 130         alias,
 131         align,
 132         alignstack,
 133         all,
 134         allocator,
 135         allocator_internals,
 136         alloc_error_handler,
 137         allow,
 138         allowed,
 139         allow_fail,
 140         allow_internal_unsafe,
 141         allow_internal_unstable,
 142         allow_internal_unstable_backcompat_hack,
 143         always,
 144         and,
 145         any,
 146         arbitrary_enum_discriminant,
 147         arbitrary_self_types,
 148         Arc,
 149         Arguments,
 150         ArgumentV1,
 151         arith_offset,
 152         arm_target_feature,
 153         asm,
 154         assert,
 155         associated_consts,
 156         associated_type_bounds,
 157         associated_type_defaults,
 158         associated_types,
 159         assume_init,
 160         async_await,
 161         async_closure,
 162         atomics,
 163         attr,
 164         attributes,
 165         attr_literals,
 166         att_syntax,
 167         augmented_assignments,
 168         automatically_derived,
 169         avx512_target_feature,
 170         await_macro,
 171         begin_panic,
 172         bench,
 173         bin,
 174         bind_by_move_pattern_guards,
 175         bindings_after_at,
 176         block,
 177         bool,
 178         borrowck_graphviz_format,
 179         borrowck_graphviz_postflow,
 180         borrowck_graphviz_preflow,
 181         box_patterns,
 182         box_syntax,
 183         braced_empty_structs,
 184         bswap,
 185         bitreverse,
 186         C,
 187         caller_location,
 188         cdylib,
 189         cfg,
 190         cfg_accessible,
 191         cfg_attr,
 192         cfg_attr_multi,
 193         cfg_doctest,
 194         cfg_sanitize,
 195         cfg_target_feature,
 196         cfg_target_has_atomic,
 197         cfg_target_thread_local,
 198         cfg_target_vendor,
 199         cfg_version,
 200         char,
 201         clippy,
 202         clone,
 203         Clone,
 204         clone_closures,
 205         clone_from,
 206         closure_to_fn_coercion,
 207         cmp,
 208         cmpxchg16b_target_feature,
 209         cold,
 210         column,
 211         compile_error,
 212         compiler_builtins,
 213         concat,
 214         concat_idents,
 215         conservative_impl_trait,
 216         console,
 217         const_compare_raw_pointers,
 218         const_constructor,
 219         const_eval_limit,
 220         const_extern_fn,
 221         const_fn,
 222         const_fn_union,
 223         const_generics,
 224         const_if_match,
 225         const_indexing,
 226         const_in_array_repeat_expressions,
 227         const_let,
 228         const_loop,
 229         const_mut_refs,
 230         const_panic,
 231         const_precise_live_drops,
 232         const_raw_ptr_deref,
 233         const_raw_ptr_to_usize_cast,
 234         const_transmute,
 235         const_trait_bound_opt_out,
 236         const_trait_impl,
 237         contents,
 238         context,
 239         convert,
 240         Copy,
 241         copy_closures,
 242         core,
 243         core_intrinsics,
 244         count_code_region,
 245         crate_id,
 246         crate_in_paths,
 247         crate_local,
 248         crate_name,
 249         crate_type,
 250         crate_visibility_modifier,
 251         ctpop,
 252         cttz,
 253         cttz_nonzero,
 254         ctlz,
 255         ctlz_nonzero,
 256         custom_attribute,
 257         custom_derive,
 258         custom_inner_attributes,
 259         custom_test_frameworks,
 260         c_variadic,
 261         debug_trait,
 262         declare_lint_pass,
 263         decl_macro,
 264         debug,
 265         Debug,
 266         Decodable,
 267         Default,
 268         default_lib_allocator,
 269         default_type_parameter_fallback,
 270         default_type_params,
 271         delay_span_bug_from_inside_query,
 272         deny,
 273         deprecated,
 274         deref,
 275         deref_mut,
 276         derive,
 277         diagnostic,
 278         direct,
 279         discriminant_value,
 280         doc,
 281         doc_alias,
 282         doc_cfg,
 283         doc_keyword,
 284         doc_masked,
 285         doctest,
 286         document_private_items,
 287         dotdoteq_in_patterns,
 288         dotdot_in_tuple_patterns,
 289         double_braced_crate: "{{crate}}",
 290         double_braced_impl: "{{impl}}",
 291         double_braced_misc: "{{misc}}",
 292         double_braced_closure: "{{closure}}",
 293         double_braced_constructor: "{{constructor}}",
 294         double_braced_constant: "{{constant}}",
 295         double_braced_opaque: "{{opaque}}",
 296         dropck_eyepatch,
 297         dropck_parametricity,
 298         drop_types_in_const,
 299         dylib,
 300         dyn_trait,
 301         eh_personality,
 302         enable,
 303         Encodable,
 304         env,
 305         eq,
 306         err,
 307         Err,
 308         Eq,
 309         Equal,
 310         enclosing_scope,
 311         except,
 312         exclusive_range_pattern,
 313         exhaustive_integer_patterns,
 314         exhaustive_patterns,
 315         existential_type,
 316         expected,
 317         export_name,
 318         expr,
 319         extern_absolute_paths,
 320         external_doc,
 321         extern_crate_item_prelude,
 322         extern_crate_self,
 323         extern_in_paths,
 324         extern_prelude,
 325         extern_types,
 326         f16c_target_feature,
 327         f32,
 328         f64,
 329         feature,
 330         ffi_const,
 331         ffi_pure,
 332         ffi_returns_twice,
 333         field,
 334         field_init_shorthand,
 335         file,
 336         fmt,
 337         fmt_internals,
 338         fn_must_use,
 339         forbid,
 340         format_args,
 341         format_args_nl,
 342         from,
 343         From,
 344         from_desugaring,
 345         from_error,
 346         from_generator,
 347         from_method,
 348         from_ok,
 349         from_usize,
 350         from_trait,
 351         fundamental,
 352         future,
 353         Future,
 354         FxHashSet,
 355         FxHashMap,
 356         gen_future,
 357         gen_kill,
 358         generators,
 359         generic_associated_types,
 360         generic_param_attrs,
 361         get_context,
 362         global_allocator,
 363         global_asm,
 364         globs,
 365         half_open_range_patterns,
 366         hash,
 367         Hash,
 368         HashSet,
 369         HashMap,
 370         hexagon_target_feature,
 371         hidden,
 372         homogeneous_aggregate,
 373         html_favicon_url,
 374         html_logo_url,
 375         html_no_source,
 376         html_playground_url,
 377         html_root_url,
 378         i128,
 379         i128_type,
 380         i16,
 381         i32,
 382         i64,
 383         i8,
 384         ident,
 385         if_let,
 386         if_while_or_patterns,
 387         ignore,
 388         inlateout,
 389         inout,
 390         impl_header_lifetime_elision,
 391         impl_lint_pass,
 392         impl_trait_in_bindings,
 393         import_shadowing,
 394         index,
 395         index_mut,
 396         in_band_lifetimes,
 397         include,
 398         include_bytes,
 399         include_str,
 400         inclusive_range_syntax,
 401         infer_outlives_requirements,
 402         infer_static_outlives_requirements,
 403         inline,
 404         intel,
 405         into_iter,
 406         IntoIterator,
 407         into_result,
 408         intrinsics,
 409         irrefutable_let_patterns,
 410         isize,
 411         issue,
 412         issue_5723_bootstrap,
 413         issue_tracker_base_url,
 414         item,
 415         item_context: "ItemContext",
 416         item_like_imports,
 417         iter,
 418         Iterator,
 419         keyword,
 420         kind,
 421         label,
 422         label_break_value,
 423         lang,
 424         lang_items,
 425         lateout,
 426         let_chains,
 427         lhs,
 428         lib,
 429         lifetime,
 430         line,
 431         link,
 432         linkage,
 433         link_args,
 434         link_cfg,
 435         link_llvm_intrinsics,
 436         link_name,
 437         link_ordinal,
 438         link_section,
 439         LintPass,
 440         lint_reasons,
 441         literal,
 442         llvm_asm,
 443         local_inner_macros,
 444         log_syntax,
 445         loop_break_value,
 446         macro_at_most_once_rep,
 447         macro_escape,
 448         macro_export,
 449         macro_lifetime_matcher,
 450         macro_literal_matcher,
 451         macro_reexport,
 452         macros_in_extern,
 453         macro_use,
 454         macro_vis_matcher,
 455         main,
 456         managed_boxes,
 457         marker,
 458         marker_trait_attr,
 459         masked,
 460         match_beginning_vert,
 461         match_default_bindings,
 462         may_dangle,
 463         maybe_uninit_uninit,
 464         maybe_uninit_zeroed,
 465         mem_uninitialized,
 466         mem_zeroed,
 467         member_constraints,
 468         memory,
 469         message,
 470         meta,
 471         min_align_of,
 472         min_const_fn,
 473         min_const_unsafe_fn,
 474         min_specialization,
 475         mips_target_feature,
 476         mmx_target_feature,
 477         module,
 478         module_path,
 479         more_struct_aliases,
 480         move_ref_pattern,
 481         move_val_init,
 482         movbe_target_feature,
 483         mul_with_overflow,
 484         must_use,
 485         naked,
 486         naked_functions,
 487         name,
 488         needs_allocator,
 489         needs_drop,
 490         needs_panic_runtime,
 491         negate_unsigned,
 492         negative_impls,
 493         never,
 494         never_type,
 495         never_type_fallback,
 496         new,
 497         next,
 498         __next,
 499         nll,
 500         no_builtins,
 501         no_core,
 502         no_crate_inject,
 503         no_debug,
 504         no_default_passes,
 505         no_implicit_prelude,
 506         no_inline,
 507         no_link,
 508         no_main,
 509         no_mangle,
 510         nomem,
 511         non_ascii_idents,
 512         None,
 513         non_exhaustive,
 514         non_modrs_mods,
 515         noreturn,
 516         no_niche,
 517         no_sanitize,
 518         nostack,
 519         no_stack_check,
 520         no_start,
 521         no_std,
 522         not,
 523         note,
 524         object_safe_for_dispatch,
 525         offset,
 526         Ok,
 527         omit_gdb_pretty_printer_section,
 528         on,
 529         on_unimplemented,
 530         oom,
 531         ops,
 532         optimize,
 533         optimize_attribute,
 534         optin_builtin_traits,
 535         option,
 536         Option,
 537         option_env,
 538         options,
 539         opt_out_copy,
 540         or,
 541         or_patterns,
 542         Ord,
 543         Ordering,
 544         out,
 545         Output,
 546         overlapping_marker_traits,
 547         packed,
 548         panic,
 549         panic_handler,
 550         panic_impl,
 551         panic_implementation,
 552         panic_runtime,
 553         parent_trait,
 554         partial_cmp,
 555         param_attrs,
 556         PartialEq,
 557         PartialOrd,
 558         passes,
 559         pat,
 560         path,
 561         pattern_parentheses,
 562         Pending,
 563         pin,
 564         Pin,
 565         pinned,
 566         platform_intrinsics,
 567         plugin,
 568         plugin_registrar,
 569         plugins,
 570         poll,
 571         Poll,
 572         powerpc_target_feature,
 573         precise_pointer_size_matching,
 574         pref_align_of,
 575         prelude,
 576         prelude_import,
 577         preserves_flags,
 578         primitive,
 579         proc_dash_macro: "proc-macro",
 580         proc_macro,
 581         proc_macro_attribute,
 582         proc_macro_def_site,
 583         proc_macro_derive,
 584         proc_macro_expr,
 585         proc_macro_gen,
 586         proc_macro_hygiene,
 587         proc_macro_internals,
 588         proc_macro_mod,
 589         proc_macro_non_items,
 590         proc_macro_path_invoc,
 591         profiler_builtins,
 592         profiler_runtime,
 593         ptr_guaranteed_eq,
 594         ptr_guaranteed_ne,
 595         ptr_offset_from,
 596         pub_restricted,
 597         pure,
 598         pushpop_unsafe,
 599         quad_precision_float,
 600         question_mark,
 601         quote,
 602         Range,
 603         RangeFrom,
 604         RangeFull,
 605         RangeInclusive,
 606         RangeTo,
 607         RangeToInclusive,
 608         raw_dylib,
 609         raw_identifiers,
 610         raw_ref_op,
 611         Rc,
 612         readonly,
 613         Ready,
 614         reason,
 615         recursion_limit,
 616         reexport_test_harness_main,
 617         reflect,
 618         register_attr,
 619         register_tool,
 620         relaxed_adts,
 621         repr,
 622         repr128,
 623         repr_align,
 624         repr_align_enum,
 625         repr_no_niche,
 626         repr_packed,
 627         repr_simd,
 628         repr_transparent,
 629         re_rebalance_coherence,
 630         result,
 631         Result,
 632         Return,
 633         rhs,
 634         riscv_target_feature,
 635         rlib,
 636         rotate_left,
 637         rotate_right,
 638         rt,
 639         rtm_target_feature,
 640         rust,
 641         rust_2015_preview,
 642         rust_2018_preview,
 643         rust_begin_unwind,
 644         rustc,
 645         RustcDecodable,
 646         RustcEncodable,
 647         rustc_allocator,
 648         rustc_allocator_nounwind,
 649         rustc_allow_const_fn_ptr,
 650         rustc_args_required_const,
 651         rustc_attrs,
 652         rustc_builtin_macro,
 653         rustc_clean,
 654         rustc_const_unstable,
 655         rustc_const_stable,
 656         rustc_conversion_suggestion,
 657         rustc_def_path,
 658         rustc_deprecated,
 659         rustc_diagnostic_item,
 660         rustc_diagnostic_macros,
 661         rustc_dirty,
 662         rustc_dummy,
 663         rustc_dump_env_program_clauses,
 664         rustc_dump_program_clauses,
 665         rustc_dump_user_substs,
 666         rustc_error,
 667         rustc_expected_cgu_reuse,
 668         rustc_if_this_changed,
 669         rustc_inherit_overflow_checks,
 670         rustc_layout,
 671         rustc_layout_scalar_valid_range_end,
 672         rustc_layout_scalar_valid_range_start,
 673         rustc_macro_transparency,
 674         rustc_mir,
 675         rustc_nonnull_optimization_guaranteed,
 676         rustc_object_lifetime_default,
 677         rustc_on_unimplemented,
 678         rustc_outlives,
 679         rustc_paren_sugar,
 680         rustc_partition_codegened,
 681         rustc_partition_reused,
 682         rustc_peek,
 683         rustc_peek_definite_init,
 684         rustc_peek_liveness,
 685         rustc_peek_maybe_init,
 686         rustc_peek_maybe_uninit,
 687         rustc_peek_indirectly_mutable,
 688         rustc_private,
 689         rustc_proc_macro_decls,
 690         rustc_promotable,
 691         rustc_regions,
 692         rustc_unsafe_specialization_marker,
 693         rustc_specialization_trait,
 694         rustc_stable,
 695         rustc_std_internal_symbol,
 696         rustc_symbol_name,
 697         rustc_synthetic,
 698         rustc_reservation_impl,
 699         rustc_test_marker,
 700         rustc_then_this_would_need,
 701         rustc_variance,
 702         rustfmt,
 703         rust_eh_personality,
 704         rust_oom,
 705         rvalue_static_promotion,
 706         sanitize,
 707         sanitizer_runtime,
 708         saturating_add,
 709         saturating_sub,
 710         _Self,
 711         self_in_typedefs,
 712         self_struct_ctor,
 713         send_trait,
 714         should_panic,
 715         simd,
 716         simd_extract,
 717         simd_ffi,
 718         simd_insert,
 719         since,
 720         size,
 721         size_of,
 722         slice_patterns,
 723         slicing_syntax,
 724         soft,
 725         Some,
 726         specialization,
 727         speed,
 728         sse4a_target_feature,
 729         stable,
 730         staged_api,
 731         start,
 732         static_in_const,
 733         staticlib,
 734         static_nobundle,
 735         static_recursion,
 736         std,
 737         std_inject,
 738         str,
 739         stringify,
 740         stmt,
 741         stmt_expr_attributes,
 742         stop_after_dataflow,
 743         struct_field_attributes,
 744         struct_inherit,
 745         structural_match,
 746         struct_variant,
 747         sty,
 748         sub_with_overflow,
 749         suggestion,
 750         sym,
 751         sync_trait,
 752         target_feature,
 753         target_feature_11,
 754         target_has_atomic,
 755         target_has_atomic_load_store,
 756         target_thread_local,
 757         task,
 758         _task_context,
 759         tbm_target_feature,
 760         termination_trait,
 761         termination_trait_test,
 762         test,
 763         test_2018_feature,
 764         test_accepted_feature,
 765         test_case,
 766         test_removed_feature,
 767         test_runner,
 768         then_with,
 769         thread,
 770         thread_local,
 771         tool_attributes,
 772         tool_lints,
 773         trace_macros,
 774         track_caller,
 775         trait_alias,
 776         transmute,
 777         transparent,
 778         transparent_enums,
 779         transparent_unions,
 780         trivial_bounds,
 781         Try,
 782         try_blocks,
 783         try_trait,
 784         tt,
 785         tuple_indexing,
 786         two_phase,
 787         Ty,
 788         ty,
 789         type_alias_impl_trait,
 790         type_id,
 791         type_name,
 792         TyCtxt,
 793         TyKind,
 794         type_alias_enum_variants,
 795         type_ascription,
 796         type_length_limit,
 797         type_macros,
 798         u128,
 799         u16,
 800         u32,
 801         u64,
 802         u8,
 803         unboxed_closures,
 804         unchecked_add,
 805         unchecked_div,
 806         unchecked_mul,
 807         unchecked_rem,
 808         unchecked_shl,
 809         unchecked_shr,
 810         unchecked_sub,
 811         underscore_const_names,
 812         underscore_imports,
 813         underscore_lifetimes,
 814         uniform_paths,
 815         universal_impl_trait,
 816         unmarked_api,
 817         unreachable_code,
 818         unrestricted_attribute_tokens,
 819         unsafe_block_in_unsafe_fn,
 820         unsafe_no_drop_flag,
 821         unsized_locals,
 822         unsized_tuple_coercion,
 823         unstable,
 824         untagged_unions,
 825         unwind,
 826         unwind_attributes,
 827         unwrap_or,
 828         used,
 829         use_extern_macros,
 830         use_nested_groups,
 831         usize,
 832         v1,
 833         val,
 834         var,
 835         variant_count,
 836         vec,
 837         Vec,
 838         version,
 839         vis,
 840         visible_private_types,
 841         volatile,
 842         warn,
 843         wasm_import_module,
 844         wasm_target_feature,
 845         while_let,
 846         windows,
 847         windows_subsystem,
 848         wrapping_add,
 849         wrapping_sub,
 850         wrapping_mul,
 851         Yield,
 852     }
 853 }
 854
 855 #[derive(Copy, Clone, Eq, HashStable_Generic)]
 856 pub struct Ident {
 857     pub name: Symbol,
 858     pub span: Span,
 859 }
 860
 861 impl Ident {
 862     #[inline]
 863     /// Constructs a new identifier from a symbol and a span.
 864     pub const fn new(name: Symbol, span: Span) -> Ident {
 865         Ident { name, span }
 866     }
 867
 868     /// Constructs a new identifier with a dummy span.
 869     #[inline]
 870     pub const fn with_dummy_span(name: Symbol) -> Ident {
 871         Ident::new(name, DUMMY_SP)
 872     }
 873
 874     #[inline]
 875     pub fn invalid() -> Ident {
 876         Ident::with_dummy_span(kw::Invalid)
 877     }
 878
 879     /// Maps a string to an identifier with a dummy span.
 880     pub fn from_str(string: &str) -> Ident {
 881         Ident::with_dummy_span(Symbol::intern(string))
 882     }
 883
 884     /// Maps a string and a span to an identifier.
 885     pub fn from_str_and_span(string: &str, span: Span) -> Ident {
 886         Ident::new(Symbol::intern(string), span)
 887     }
 888
 889     /// Replaces `lo` and `hi` with those from `span`, but keep hygiene context.
 890     pub fn with_span_pos(self, span: Span) -> Ident {
 891         Ident::new(self.name, span.with_ctxt(self.span.ctxt()))
 892     }
 893
 894     pub fn without_first_quote(self) -> Ident {
 895         Ident::new(Symbol::intern(self.as_str().trim_start_matches('\'')), self.span)
 896     }
 897
 898     /// "Normalize" ident for use in comparisons using "item hygiene".
 899     /// Identifiers with same string value become same if they came from the same macro 2.0 macro
 900     /// (e.g., `macro` item, but not `macro_rules` item) and stay different if they came from
 901     /// different macro 2.0 macros.
 902     /// Technically, this operation strips all non-opaque marks from ident's syntactic context.
 903     pub fn normalize_to_macros_2_0(self) -> Ident {
 904         Ident::new(self.name, self.span.normalize_to_macros_2_0())
 905     }
 906
 907     /// "Normalize" ident for use in comparisons using "local variable hygiene".
 908     /// Identifiers with same string value become same if they came from the same non-transparent
 909     /// macro (e.g., `macro` or `macro_rules!` items) and stay different if they came from different
 910     /// non-transparent macros.
 911     /// Technically, this operation strips all transparent marks from ident's syntactic context.
 912     pub fn normalize_to_macro_rules(self) -> Ident {
 913         Ident::new(self.name, self.span.normalize_to_macro_rules())
 914     }
 915
 916     /// Convert the name to a `SymbolStr`. This is a slowish operation because
 917     /// it requires locking the symbol interner.
 918     pub fn as_str(self) -> SymbolStr {
 919         self.name.as_str()
 920     }
 921 }
 922
 923 impl PartialEq for Ident {
 924     fn eq(&self, rhs: &Self) -> bool {
 925         self.name == rhs.name && self.span.ctxt() == rhs.span.ctxt()
 926     }
 927 }
 928
 929 impl Hash for Ident {
 930     fn hash<H: Hasher>(&self, state: &mut H) {
 931         self.name.hash(state);
 932         self.span.ctxt().hash(state);
 933     }
 934 }
 935
 936 impl fmt::Debug for Ident {
 937     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 938         fmt::Display::fmt(self, f)?;
 939         fmt::Debug::fmt(&self.span.ctxt(), f)
 940     }
 941 }
 942
 943 /// This implementation is supposed to be used in error messages, so it's expected to be identical
 944 /// to printing the original identifier token written in source code (`token_to_string`),
 945 /// except that AST identifiers don't keep the rawness flag, so we have to guess it.
 946 impl fmt::Display for Ident {
 947     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 948         fmt::Display::fmt(&IdentPrinter::new(self.name, self.is_raw_guess(), None), f)
 949     }
 950 }
 951
 952 impl UseSpecializedEncodable for Ident {
 953     fn default_encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
 954         s.emit_struct("Ident", 2, |s| {
 955             s.emit_struct_field("name", 0, |s| self.name.encode(s))?;
 956             s.emit_struct_field("span", 1, |s| self.span.encode(s))
 957         })
 958     }
 959 }
 960
 961 impl UseSpecializedDecodable for Ident {
 962     fn default_decode<D: Decoder>(d: &mut D) -> Result<Self, D::Error> {
 963         d.read_struct("Ident", 2, |d| {
 964             Ok(Ident {
 965                 name: d.read_struct_field("name", 0, Decodable::decode)?,
 966                 span: d.read_struct_field("span", 1, Decodable::decode)?,
 967             })
 968         })
 969     }
 970 }
 971
 972 /// This is the most general way to print identifiers.
 973 /// AST pretty-printer is used as a fallback for turning AST structures into token streams for
 974 /// proc macros. Additionally, proc macros may stringify their input and expect it survive the
 975 /// stringification (especially true for proc macro derives written between Rust 1.15 and 1.30).
 976 /// So we need to somehow pretty-print `$crate` in a way preserving at least some of its
 977 /// hygiene data, most importantly name of the crate it refers to.
 978 /// As a result we print `$crate` as `crate` if it refers to the local crate
 979 /// and as `::other_crate_name` if it refers to some other crate.
 980 /// Note, that this is only done if the ident token is printed from inside of AST pretty-pringing,
 981 /// but not otherwise. Pretty-printing is the only way for proc macros to discover token contents,
 982 /// so we should not perform this lossy conversion if the top level call to the pretty-printer was
 983 /// done for a token stream or a single token.
 984 pub struct IdentPrinter {
 985     symbol: Symbol,
 986     is_raw: bool,
 987     /// Span used for retrieving the crate name to which `$crate` refers to,
 988     /// if this field is `None` then the `$crate` conversion doesn't happen.
 989     convert_dollar_crate: Option<Span>,
 990 }
 991
 992 impl IdentPrinter {
 993     /// The most general `IdentPrinter` constructor. Do not use this.
 994     pub fn new(symbol: Symbol, is_raw: bool, convert_dollar_crate: Option<Span>) -> IdentPrinter {
 995         IdentPrinter { symbol, is_raw, convert_dollar_crate }
 996     }
 997
 998     /// This implementation is supposed to be used when printing identifiers
 999     /// as a part of pretty-printing for larger AST pieces.
1000     /// Do not use this either.
1001     pub fn for_ast_ident(ident: Ident, is_raw: bool) -> IdentPrinter {
1002         IdentPrinter::new(ident.name, is_raw, Some(ident.span))
1003     }
1004 }
1005
1006 impl fmt::Display for IdentPrinter {
1007     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1008         if self.is_raw {
1009             f.write_str("r#")?;
1010         } else {
1011             if self.symbol == kw::DollarCrate {
1012                 if let Some(span) = self.convert_dollar_crate {
1013                     let converted = span.ctxt().dollar_crate_name();
1014                     if !converted.is_path_segment_keyword() {
1015                         f.write_str("::")?;
1016                     }
1017                     return fmt::Display::fmt(&converted, f);
1018                 }
1019             }
1020         }
1021         fmt::Display::fmt(&self.symbol, f)
1022     }
1023 }
1024
1025 /// An newtype around `Ident` that calls [Ident::normalize_to_macro_rules] on
1026 /// construction.
1027 // FIXME(matthewj, petrochenkov) Use this more often, add a similar
1028 // `ModernIdent` struct and use that as well.
1029 #[derive(Copy, Clone, Eq, PartialEq, Hash)]
1030 pub struct MacroRulesNormalizedIdent(Ident);
1031
1032 impl MacroRulesNormalizedIdent {
1033     pub fn new(ident: Ident) -> Self {
1034         Self(ident.normalize_to_macro_rules())
1035     }
1036 }
1037
1038 impl fmt::Debug for MacroRulesNormalizedIdent {
1039     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1040         fmt::Debug::fmt(&self.0, f)
1041     }
1042 }
1043
1044 impl fmt::Display for MacroRulesNormalizedIdent {
1045     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1046         fmt::Display::fmt(&self.0, f)
1047     }
1048 }
1049
1050 /// An interned string.
1051 ///
1052 /// Internally, a `Symbol` is implemented as an index, and all operations
1053 /// (including hashing, equality, and ordering) operate on that index. The use
1054 /// of `rustc_index::newtype_index!` means that `Option<Symbol>` only takes up 4 bytes,
1055 /// because `rustc_index::newtype_index!` reserves the last 256 values for tagging purposes.
1056 ///
1057 /// Note that `Symbol` cannot directly be a `rustc_index::newtype_index!` because it
1058 /// implements `fmt::Debug`, `Encodable`, and `Decodable` in special ways.
1059 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
1060 pub struct Symbol(SymbolIndex);
1061
1062 rustc_index::newtype_index! {
1063     pub struct SymbolIndex { .. }
1064 }
1065
1066 impl Symbol {
1067     const fn new(n: u32) -> Self {
1068         Symbol(SymbolIndex::from_u32(n))
1069     }
1070
1071     /// Maps a string to its interned representation.
1072     pub fn intern(string: &str) -> Self {
1073         with_interner(|interner| interner.intern(string))
1074     }
1075
1076     /// Access the symbol's chars. This is a slowish operation because it
1077     /// requires locking the symbol interner.
1078     pub fn with<F: FnOnce(&str) -> R, R>(self, f: F) -> R {
1079         with_interner(|interner| f(interner.get(self)))
1080     }
1081
1082     /// Convert to a `SymbolStr`. This is a slowish operation because it
1083     /// requires locking the symbol interner.
1084     pub fn as_str(self) -> SymbolStr {
1085         with_interner(|interner| unsafe {
1086             SymbolStr { string: std::mem::transmute::<&str, &str>(interner.get(self)) }
1087         })
1088     }
1089
1090     pub fn as_u32(self) -> u32 {
1091         self.0.as_u32()
1092     }
1093
1094     /// This method is supposed to be used in error messages, so it's expected to be
1095     /// identical to printing the original identifier token written in source code
1096     /// (`token_to_string`, `Ident::to_string`), except that symbols don't keep the rawness flag
1097     /// or edition, so we have to guess the rawness using the global edition.
1098     pub fn to_ident_string(self) -> String {
1099         Ident::with_dummy_span(self).to_string()
1100     }
1101 }
1102
1103 impl fmt::Debug for Symbol {
1104     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1105         self.with(|str| fmt::Debug::fmt(&str, f))
1106     }
1107 }
1108
1109 impl fmt::Display for Symbol {
1110     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1111         self.with(|str| fmt::Display::fmt(&str, f))
1112     }
1113 }
1114
1115 impl Encodable for Symbol {
1116     fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
1117         self.with(|string| s.emit_str(string))
1118     }
1119 }
1120
1121 impl Decodable for Symbol {
1122     #[inline]
1123     fn decode<D: Decoder>(d: &mut D) -> Result<Symbol, D::Error> {
1124         Ok(Symbol::intern(&d.read_str()?))
1125     }
1126 }
1127
1128 impl<CTX> HashStable<CTX> for Symbol {
1129     #[inline]
1130     fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
1131         self.as_str().hash_stable(hcx, hasher);
1132     }
1133 }
1134
1135 impl<CTX> ToStableHashKey<CTX> for Symbol {
1136     type KeyType = SymbolStr;
1137
1138     #[inline]
1139     fn to_stable_hash_key(&self, _: &CTX) -> SymbolStr {
1140         self.as_str()
1141     }
1142 }
1143
1144 // The `&'static str`s in this type actually point into the arena.
1145 #[derive(Default)]
1146 pub struct Interner {
1147     arena: DroplessArena,
1148     names: FxHashMap<&'static str, Symbol>,
1149     strings: Vec<&'static str>,
1150 }
1151
1152 impl Interner {
1153     fn prefill(init: &[&'static str]) -> Self {
1154         Interner {
1155             strings: init.into(),
1156             names: init.iter().copied().zip((0..).map(Symbol::new)).collect(),
1157             ..Default::default()
1158         }
1159     }
1160
1161     #[inline]
1162     pub fn intern(&mut self, string: &str) -> Symbol {
1163         if let Some(&name) = self.names.get(string) {
1164             return name;
1165         }
1166
1167         let name = Symbol::new(self.strings.len() as u32);
1168
1169         // `from_utf8_unchecked` is safe since we just allocated a `&str` which is known to be
1170         // UTF-8.
1171         let string: &str =
1172             unsafe { str::from_utf8_unchecked(self.arena.alloc_slice(string.as_bytes())) };
1173         // It is safe to extend the arena allocation to `'static` because we only access
1174         // these while the arena is still alive.
1175         let string: &'static str = unsafe { &*(string as *const str) };
1176         self.strings.push(string);
1177         self.names.insert(string, name);
1178         name
1179     }
1180
1181     // Get the symbol as a string. `Symbol::as_str()` should be used in
1182     // preference to this function.
1183     pub fn get(&self, symbol: Symbol) -> &str {
1184         self.strings[symbol.0.as_usize()]
1185     }
1186 }
1187
1188 // This module has a very short name because it's used a lot.
1189 /// This module contains all the defined keyword `Symbol`s.
1190 ///
1191 /// Given that `kw` is imported, use them like `kw::keyword_name`.
1192 /// For example `kw::Loop` or `kw::Break`.
1193 pub mod kw {
1194     use super::Symbol;
1195     keywords!();
1196 }
1197
1198 // This module has a very short name because it's used a lot.
1199 /// This module contains all the defined non-keyword `Symbol`s.
1200 ///
1201 /// Given that `sym` is imported, use them like `sym::symbol_name`.
1202 /// For example `sym::rustfmt` or `sym::u8`.
1203 #[allow(rustc::default_hash_types)]
1204 pub mod sym {
1205     use super::Symbol;
1206     use std::convert::TryInto;
1207
1208     symbols!();
1209
1210     // Used from a macro in `librustc_feature/accepted.rs`
1211     pub use super::kw::MacroRules as macro_rules;
1212
1213     // Get the symbol for an integer. The first few non-negative integers each
1214     // have a static symbol and therefore are fast.
1215     pub fn integer<N: TryInto<usize> + Copy + ToString>(n: N) -> Symbol {
1216         if let Result::Ok(idx) = n.try_into() {
1217             if let Option::Some(&sym_) = digits_array.get(idx) {
1218                 return sym_;
1219             }
1220         }
1221         Symbol::intern(&n.to_string())
1222     }
1223 }
1224
1225 impl Symbol {
1226     fn is_used_keyword_2018(self) -> bool {
1227         self >= kw::Async && self <= kw::Dyn
1228     }
1229
1230     fn is_unused_keyword_2018(self) -> bool {
1231         self == kw::Try
1232     }
1233
1234     /// Used for sanity checking rustdoc keyword sections.
1235     pub fn is_doc_keyword(self) -> bool {
1236         self <= kw::Union
1237     }
1238
1239     /// A keyword or reserved identifier that can be used as a path segment.
1240     pub fn is_path_segment_keyword(self) -> bool {
1241         self == kw::Super
1242             || self == kw::SelfLower
1243             || self == kw::SelfUpper
1244             || self == kw::Crate
1245             || self == kw::PathRoot
1246             || self == kw::DollarCrate
1247     }
1248
1249     /// Returns `true` if the symbol is `true` or `false`.
1250     pub fn is_bool_lit(self) -> bool {
1251         self == kw::True || self == kw::False
1252     }
1253
1254     /// This symbol can be a raw identifier.
1255     pub fn can_be_raw(self) -> bool {
1256         self != kw::Invalid && self != kw::Underscore && !self.is_path_segment_keyword()
1257     }
1258 }
1259
1260 impl Ident {
1261     // Returns `true` for reserved identifiers used internally for elided lifetimes,
1262     // unnamed method parameters, crate root module, error recovery etc.
1263     pub fn is_special(self) -> bool {
1264         self.name <= kw::Underscore
1265     }
1266
1267     /// Returns `true` if the token is a keyword used in the language.
1268     pub fn is_used_keyword(self) -> bool {
1269         // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
1270         self.name >= kw::As && self.name <= kw::While
1271             || self.name.is_used_keyword_2018() && self.span.rust_2018()
1272     }
1273
1274     /// Returns `true` if the token is a keyword reserved for possible future use.
1275     pub fn is_unused_keyword(self) -> bool {
1276         // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
1277         self.name >= kw::Abstract && self.name <= kw::Yield
1278             || self.name.is_unused_keyword_2018() && self.span.rust_2018()
1279     }
1280
1281     /// Returns `true` if the token is either a special identifier or a keyword.
1282     pub fn is_reserved(self) -> bool {
1283         self.is_special() || self.is_used_keyword() || self.is_unused_keyword()
1284     }
1285
1286     /// A keyword or reserved identifier that can be used as a path segment.
1287     pub fn is_path_segment_keyword(self) -> bool {
1288         self.name.is_path_segment_keyword()
1289     }
1290
1291     /// We see this identifier in a normal identifier position, like variable name or a type.
1292     /// How was it written originally? Did it use the raw form? Let's try to guess.
1293     pub fn is_raw_guess(self) -> bool {
1294         self.name.can_be_raw() && self.is_reserved()
1295     }
1296 }
1297
1298 #[inline]
1299 fn with_interner<T, F: FnOnce(&mut Interner) -> T>(f: F) -> T {
1300     GLOBALS.with(|globals| f(&mut *globals.symbol_interner.lock()))
1301 }
1302
1303 /// An alternative to `Symbol`, useful when the chars within the symbol need to
1304 /// be accessed. It deliberately has limited functionality and should only be
1305 /// used for temporary values.
1306 ///
1307 /// Because the interner outlives any thread which uses this type, we can
1308 /// safely treat `string` which points to interner data, as an immortal string,
1309 /// as long as this type never crosses between threads.
1310 //
1311 // FIXME: ensure that the interner outlives any thread which uses `SymbolStr`,
1312 // by creating a new thread right after constructing the interner.
1313 #[derive(Clone, Eq, PartialOrd, Ord)]
1314 pub struct SymbolStr {
1315     string: &'static str,
1316 }
1317
1318 // This impl allows a `SymbolStr` to be directly equated with a `String` or
1319 // `&str`.
1320 impl<T: std::ops::Deref<Target = str>> std::cmp::PartialEq<T> for SymbolStr {
1321     fn eq(&self, other: &T) -> bool {
1322         self.string == other.deref()
1323     }
1324 }
1325
1326 impl !Send for SymbolStr {}
1327 impl !Sync for SymbolStr {}
1328
1329 /// This impl means that if `ss` is a `SymbolStr`:
1330 /// - `*ss` is a `str`;
1331 /// - `&*ss` is a `&str`;
1332 /// - `&ss as &str` is a `&str`, which means that `&ss` can be passed to a
1333 ///   function expecting a `&str`.
1334 impl std::ops::Deref for SymbolStr {
1335     type Target = str;
1336     #[inline]
1337     fn deref(&self) -> &str {
1338         self.string
1339     }
1340 }
1341
1342 impl fmt::Debug for SymbolStr {
1343     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1344         fmt::Debug::fmt(self.string, f)
1345     }
1346 }
1347
1348 impl fmt::Display for SymbolStr {
1349     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1350         fmt::Display::fmt(self.string, f)
1351     }
1352 }
1353
1354 impl<CTX> HashStable<CTX> for SymbolStr {
1355     #[inline]
1356     fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
1357         self.string.hash_stable(hcx, hasher)
1358     }
1359 }
1360
1361 impl<CTX> ToStableHashKey<CTX> for SymbolStr {
1362     type KeyType = SymbolStr;
1363
1364     #[inline]
1365     fn to_stable_hash_key(&self, _: &CTX) -> SymbolStr {
1366         self.clone()
1367     }
1368 }