src/libsyntax_pos/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_index::vec::Idx;
   8 use rustc_macros::{symbols, HashStable_Generic};
   9 use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
  10 use rustc_serialize::{UseSpecializedDecodable, UseSpecializedEncodable};
  11 use rustc_data_structures::stable_hasher::{HashStable, ToStableHashKey, StableHasher};
  12
  13 use std::cmp::{PartialEq, PartialOrd, Ord};
  14 use std::fmt;
  15 use std::hash::{Hash, Hasher};
  16 use std::str;
  17
  18 use crate::{Span, DUMMY_SP, GLOBALS};
  19
  20 #[cfg(test)]
  21 mod tests;
  22
  23 symbols! {
  24     // After modifying this list adjust `is_special`, `is_used_keyword`/`is_unused_keyword`,
  25     // this should be rarely necessary though if the keywords are kept in alphabetic order.
  26     Keywords {
  27         // Special reserved identifiers used internally for elided lifetimes,
  28         // unnamed method parameters, crate root module, error recovery etc.
  29         Invalid:            "",
  30         PathRoot:           "{{root}}",
  31         DollarCrate:        "$crate",
  32         Underscore:         "_",
  33
  34         // Keywords that are used in stable Rust.
  35         As:                 "as",
  36         Break:              "break",
  37         Const:              "const",
  38         Continue:           "continue",
  39         Crate:              "crate",
  40         Else:               "else",
  41         Enum:               "enum",
  42         Extern:             "extern",
  43         False:              "false",
  44         Fn:                 "fn",
  45         For:                "for",
  46         If:                 "if",
  47         Impl:               "impl",
  48         In:                 "in",
  49         Let:                "let",
  50         Loop:               "loop",
  51         Match:              "match",
  52         Mod:                "mod",
  53         Move:               "move",
  54         Mut:                "mut",
  55         Pub:                "pub",
  56         Ref:                "ref",
  57         Return:             "return",
  58         SelfLower:          "self",
  59         SelfUpper:          "Self",
  60         Static:             "static",
  61         Struct:             "struct",
  62         Super:              "super",
  63         Trait:              "trait",
  64         True:               "true",
  65         Type:               "type",
  66         Unsafe:             "unsafe",
  67         Use:                "use",
  68         Where:              "where",
  69         While:              "while",
  70
  71         // Keywords that are used in unstable Rust or reserved for future use.
  72         Abstract:           "abstract",
  73         Become:             "become",
  74         Box:                "box",
  75         Do:                 "do",
  76         Final:              "final",
  77         Macro:              "macro",
  78         Override:           "override",
  79         Priv:               "priv",
  80         Typeof:             "typeof",
  81         Unsized:            "unsized",
  82         Virtual:            "virtual",
  83         Yield:              "yield",
  84
  85         // Edition-specific keywords that are used in stable Rust.
  86         Async:              "async", // >= 2018 Edition only
  87         Await:              "await", // >= 2018 Edition only
  88         Dyn:                "dyn", // >= 2018 Edition only
  89
  90         // Edition-specific keywords that are used in unstable Rust or reserved for future use.
  91         Try:                "try", // >= 2018 Edition only
  92
  93         // Special lifetime names
  94         UnderscoreLifetime: "'_",
  95         StaticLifetime:     "'static",
  96
  97         // Weak keywords, have special meaning only in specific contexts.
  98         Auto:               "auto",
  99         Catch:              "catch",
 100         Default:            "default",
 101         Raw:                "raw",
 102         Union:              "union",
 103     }
 104
 105     // Symbols that can be referred to with syntax_pos::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         add_with_overflow,
 125         advanced_slice_patterns,
 126         adx_target_feature,
 127         alias,
 128         align,
 129         alignstack,
 130         all,
 131         allocator,
 132         allocator_internals,
 133         alloc_error_handler,
 134         allow,
 135         allowed,
 136         allow_fail,
 137         allow_internal_unsafe,
 138         allow_internal_unstable,
 139         allow_internal_unstable_backcompat_hack,
 140         always,
 141         and,
 142         any,
 143         arbitrary_enum_discriminant,
 144         arbitrary_self_types,
 145         Arguments,
 146         ArgumentV1,
 147         arm_target_feature,
 148         asm,
 149         assert,
 150         associated_consts,
 151         associated_type_bounds,
 152         associated_type_defaults,
 153         associated_types,
 154         assume_init,
 155         async_await,
 156         async_closure,
 157         attr,
 158         attributes,
 159         attr_literals,
 160         augmented_assignments,
 161         automatically_derived,
 162         avx512_target_feature,
 163         await_macro,
 164         begin_panic,
 165         bench,
 166         bin,
 167         bind_by_move_pattern_guards,
 168         block,
 169         bool,
 170         borrowck_graphviz_postflow,
 171         borrowck_graphviz_preflow,
 172         box_patterns,
 173         box_syntax,
 174         braced_empty_structs,
 175         bswap,
 176         bitreverse,
 177         C,
 178         caller_location,
 179         cdylib,
 180         cfg,
 181         cfg_attr,
 182         cfg_attr_multi,
 183         cfg_doctest,
 184         cfg_sanitize,
 185         cfg_target_feature,
 186         cfg_target_has_atomic,
 187         cfg_target_thread_local,
 188         cfg_target_vendor,
 189         char,
 190         clippy,
 191         clone,
 192         Clone,
 193         clone_closures,
 194         clone_from,
 195         closure_to_fn_coercion,
 196         cmp,
 197         cmpxchg16b_target_feature,
 198         cold,
 199         column,
 200         compile_error,
 201         compiler_builtins,
 202         concat,
 203         concat_idents,
 204         conservative_impl_trait,
 205         console,
 206         const_compare_raw_pointers,
 207         const_constructor,
 208         const_extern_fn,
 209         const_fn,
 210         const_fn_union,
 211         const_generics,
 212         const_if_match,
 213         const_indexing,
 214         const_in_array_repeat_expressions,
 215         const_let,
 216         const_panic,
 217         const_raw_ptr_deref,
 218         const_raw_ptr_to_usize_cast,
 219         const_transmute,
 220         contents,
 221         context,
 222         convert,
 223         Copy,
 224         copy_closures,
 225         core,
 226         core_intrinsics,
 227         crate_id,
 228         crate_in_paths,
 229         crate_local,
 230         crate_name,
 231         crate_type,
 232         crate_visibility_modifier,
 233         ctpop,
 234         cttz,
 235         cttz_nonzero,
 236         ctlz,
 237         ctlz_nonzero,
 238         custom_attribute,
 239         custom_derive,
 240         custom_inner_attributes,
 241         custom_test_frameworks,
 242         c_variadic,
 243         debug_trait,
 244         declare_lint_pass,
 245         decl_macro,
 246         Debug,
 247         Decodable,
 248         Default,
 249         default_lib_allocator,
 250         default_type_parameter_fallback,
 251         default_type_params,
 252         delay_span_bug_from_inside_query,
 253         deny,
 254         deprecated,
 255         deref,
 256         deref_mut,
 257         derive,
 258         diagnostic,
 259         direct,
 260         doc,
 261         doc_alias,
 262         doc_cfg,
 263         doc_keyword,
 264         doc_masked,
 265         doc_spotlight,
 266         doctest,
 267         document_private_items,
 268         dotdoteq_in_patterns,
 269         dotdot_in_tuple_patterns,
 270         double_braced_crate: "{{crate}}",
 271         double_braced_impl: "{{impl}}",
 272         double_braced_misc: "{{misc}}",
 273         double_braced_closure: "{{closure}}",
 274         double_braced_constructor: "{{constructor}}",
 275         double_braced_constant: "{{constant}}",
 276         double_braced_opaque: "{{opaque}}",
 277         dropck_eyepatch,
 278         dropck_parametricity,
 279         drop_types_in_const,
 280         dylib,
 281         dyn_trait,
 282         eh_personality,
 283         eh_unwind_resume,
 284         enable,
 285         Encodable,
 286         env,
 287         eq,
 288         err,
 289         Err,
 290         Eq,
 291         Equal,
 292         enclosing_scope,
 293         except,
 294         exclusive_range_pattern,
 295         exhaustive_integer_patterns,
 296         exhaustive_patterns,
 297         existential_type,
 298         expected,
 299         export_name,
 300         expr,
 301         extern_absolute_paths,
 302         external_doc,
 303         extern_crate_item_prelude,
 304         extern_crate_self,
 305         extern_in_paths,
 306         extern_prelude,
 307         extern_types,
 308         f16c_target_feature,
 309         f32,
 310         f64,
 311         feature,
 312         ffi_returns_twice,
 313         field,
 314         field_init_shorthand,
 315         file,
 316         fmt,
 317         fmt_internals,
 318         fn_must_use,
 319         forbid,
 320         format_args,
 321         format_args_nl,
 322         from,
 323         From,
 324         from_desugaring,
 325         from_error,
 326         from_generator,
 327         from_method,
 328         from_ok,
 329         from_usize,
 330         fundamental,
 331         future,
 332         Future,
 333         FxHashSet,
 334         FxHashMap,
 335         gen_future,
 336         generators,
 337         generic_associated_types,
 338         generic_param_attrs,
 339         global_allocator,
 340         global_asm,
 341         globs,
 342         hash,
 343         Hash,
 344         HashSet,
 345         HashMap,
 346         hexagon_target_feature,
 347         hidden,
 348         homogeneous_aggregate,
 349         html_favicon_url,
 350         html_logo_url,
 351         html_no_source,
 352         html_playground_url,
 353         html_root_url,
 354         i128,
 355         i128_type,
 356         i16,
 357         i32,
 358         i64,
 359         i8,
 360         ident,
 361         if_let,
 362         if_while_or_patterns,
 363         ignore,
 364         impl_header_lifetime_elision,
 365         impl_lint_pass,
 366         impl_trait_in_bindings,
 367         import_shadowing,
 368         index,
 369         index_mut,
 370         in_band_lifetimes,
 371         include,
 372         include_bytes,
 373         include_str,
 374         inclusive_range_syntax,
 375         infer_outlives_requirements,
 376         infer_static_outlives_requirements,
 377         inline,
 378         intel,
 379         into_iter,
 380         IntoIterator,
 381         into_result,
 382         intrinsics,
 383         irrefutable_let_patterns,
 384         isize,
 385         issue,
 386         issue_5723_bootstrap,
 387         issue_tracker_base_url,
 388         item,
 389         item_context: "ItemContext",
 390         item_like_imports,
 391         iter,
 392         Iterator,
 393         keyword,
 394         kind,
 395         label,
 396         label_break_value,
 397         lang,
 398         lang_items,
 399         let_chains,
 400         lhs,
 401         lib,
 402         lifetime,
 403         line,
 404         link,
 405         linkage,
 406         link_args,
 407         link_cfg,
 408         link_llvm_intrinsics,
 409         link_name,
 410         link_ordinal,
 411         link_section,
 412         LintPass,
 413         lint_reasons,
 414         literal,
 415         local_inner_macros,
 416         log_syntax,
 417         loop_break_value,
 418         macro_at_most_once_rep,
 419         macro_escape,
 420         macro_export,
 421         macro_lifetime_matcher,
 422         macro_literal_matcher,
 423         macro_reexport,
 424         macro_rules,
 425         macros_in_extern,
 426         macro_use,
 427         macro_vis_matcher,
 428         main,
 429         managed_boxes,
 430         marker,
 431         marker_trait_attr,
 432         masked,
 433         match_beginning_vert,
 434         match_default_bindings,
 435         may_dangle,
 436         maybe_uninit_uninit,
 437         maybe_uninit_zeroed,
 438         mem_uninitialized,
 439         mem_zeroed,
 440         member_constraints,
 441         message,
 442         meta,
 443         min_align_of,
 444         min_const_fn,
 445         min_const_unsafe_fn,
 446         mips_target_feature,
 447         mmx_target_feature,
 448         module,
 449         module_path,
 450         more_struct_aliases,
 451         move_val_init,
 452         movbe_target_feature,
 453         mul_with_overflow,
 454         must_use,
 455         naked,
 456         naked_functions,
 457         name,
 458         needs_allocator,
 459         needs_drop,
 460         needs_panic_runtime,
 461         negate_unsigned,
 462         never,
 463         never_type,
 464         never_type_fallback,
 465         new,
 466         next,
 467         __next,
 468         nll,
 469         no_builtins,
 470         no_core,
 471         no_crate_inject,
 472         no_debug,
 473         no_default_passes,
 474         no_implicit_prelude,
 475         no_inline,
 476         no_link,
 477         no_main,
 478         no_mangle,
 479         non_ascii_idents,
 480         None,
 481         non_exhaustive,
 482         non_modrs_mods,
 483         no_stack_check,
 484         no_start,
 485         no_std,
 486         not,
 487         note,
 488         object_safe_for_dispatch,
 489         Ok,
 490         omit_gdb_pretty_printer_section,
 491         on,
 492         on_unimplemented,
 493         oom,
 494         ops,
 495         optimize,
 496         optimize_attribute,
 497         optin_builtin_traits,
 498         option,
 499         Option,
 500         option_env,
 501         opt_out_copy,
 502         or,
 503         or_patterns,
 504         Ord,
 505         Ordering,
 506         Output,
 507         overlapping_marker_traits,
 508         packed,
 509         panic,
 510         panic_handler,
 511         panic_impl,
 512         panic_implementation,
 513         panic_runtime,
 514         parent_trait,
 515         partial_cmp,
 516         param_attrs,
 517         PartialEq,
 518         PartialOrd,
 519         passes,
 520         pat,
 521         path,
 522         pattern_parentheses,
 523         Pending,
 524         pin,
 525         Pin,
 526         pinned,
 527         platform_intrinsics,
 528         plugin,
 529         plugin_registrar,
 530         plugins,
 531         Poll,
 532         poll_with_tls_context,
 533         powerpc_target_feature,
 534         precise_pointer_size_matching,
 535         pref_align_of,
 536         prelude,
 537         prelude_import,
 538         primitive,
 539         proc_dash_macro: "proc-macro",
 540         proc_macro,
 541         proc_macro_attribute,
 542         proc_macro_def_site,
 543         proc_macro_derive,
 544         proc_macro_expr,
 545         proc_macro_gen,
 546         proc_macro_hygiene,
 547         proc_macro_internals,
 548         proc_macro_mod,
 549         proc_macro_non_items,
 550         proc_macro_path_invoc,
 551         profiler_runtime,
 552         ptr_offset_from,
 553         pub_restricted,
 554         pushpop_unsafe,
 555         quad_precision_float,
 556         question_mark,
 557         quote,
 558         Range,
 559         RangeFrom,
 560         RangeFull,
 561         RangeInclusive,
 562         RangeTo,
 563         RangeToInclusive,
 564         raw_dylib,
 565         raw_identifiers,
 566         raw_ref_op,
 567         Ready,
 568         reason,
 569         recursion_limit,
 570         reexport_test_harness_main,
 571         reflect,
 572         register_attr,
 573         register_tool,
 574         relaxed_adts,
 575         repr,
 576         repr128,
 577         repr_align,
 578         repr_align_enum,
 579         repr_packed,
 580         repr_simd,
 581         repr_transparent,
 582         re_rebalance_coherence,
 583         result,
 584         Result,
 585         Return,
 586         rhs,
 587         rlib,
 588         rotate_left,
 589         rotate_right,
 590         rt,
 591         rtm_target_feature,
 592         rust,
 593         rust_2015_preview,
 594         rust_2018_preview,
 595         rust_begin_unwind,
 596         rustc,
 597         RustcDecodable,
 598         RustcEncodable,
 599         rustc_allocator,
 600         rustc_allocator_nounwind,
 601         rustc_allow_const_fn_ptr,
 602         rustc_args_required_const,
 603         rustc_attrs,
 604         rustc_builtin_macro,
 605         rustc_clean,
 606         rustc_const_unstable,
 607         rustc_conversion_suggestion,
 608         rustc_def_path,
 609         rustc_deprecated,
 610         rustc_diagnostic_item,
 611         rustc_diagnostic_macros,
 612         rustc_dirty,
 613         rustc_dummy,
 614         rustc_dump_env_program_clauses,
 615         rustc_dump_program_clauses,
 616         rustc_dump_user_substs,
 617         rustc_error,
 618         rustc_expected_cgu_reuse,
 619         rustc_if_this_changed,
 620         rustc_inherit_overflow_checks,
 621         rustc_layout,
 622         rustc_layout_scalar_valid_range_end,
 623         rustc_layout_scalar_valid_range_start,
 624         rustc_macro_transparency,
 625         rustc_mir,
 626         rustc_nonnull_optimization_guaranteed,
 627         rustc_object_lifetime_default,
 628         rustc_on_unimplemented,
 629         rustc_outlives,
 630         rustc_paren_sugar,
 631         rustc_partition_codegened,
 632         rustc_partition_reused,
 633         rustc_peek,
 634         rustc_peek_definite_init,
 635         rustc_peek_maybe_init,
 636         rustc_peek_maybe_uninit,
 637         rustc_peek_indirectly_mutable,
 638         rustc_private,
 639         rustc_proc_macro_decls,
 640         rustc_promotable,
 641         rustc_regions,
 642         rustc_stable,
 643         rustc_std_internal_symbol,
 644         rustc_symbol_name,
 645         rustc_synthetic,
 646         rustc_reservation_impl,
 647         rustc_test_marker,
 648         rustc_then_this_would_need,
 649         rustc_variance,
 650         rustfmt,
 651         rust_eh_personality,
 652         rust_eh_unwind_resume,
 653         rust_oom,
 654         rvalue_static_promotion,
 655         sanitize,
 656         sanitizer_runtime,
 657         saturating_add,
 658         saturating_sub,
 659         _Self,
 660         self_in_typedefs,
 661         self_struct_ctor,
 662         should_panic,
 663         simd,
 664         simd_extract,
 665         simd_ffi,
 666         simd_insert,
 667         since,
 668         size,
 669         size_of,
 670         slice_patterns,
 671         slicing_syntax,
 672         soft,
 673         Some,
 674         specialization,
 675         speed,
 676         spotlight,
 677         sse4a_target_feature,
 678         stable,
 679         staged_api,
 680         start,
 681         static_in_const,
 682         staticlib,
 683         static_nobundle,
 684         static_recursion,
 685         std,
 686         std_inject,
 687         str,
 688         stringify,
 689         stmt,
 690         stmt_expr_attributes,
 691         stop_after_dataflow,
 692         struct_field_attributes,
 693         struct_inherit,
 694         structural_match,
 695         struct_variant,
 696         sty,
 697         sub_with_overflow,
 698         suggestion,
 699         target_feature,
 700         target_has_atomic,
 701         target_has_atomic_load_store,
 702         target_thread_local,
 703         task,
 704         tbm_target_feature,
 705         termination_trait,
 706         termination_trait_test,
 707         test,
 708         test_2018_feature,
 709         test_accepted_feature,
 710         test_case,
 711         test_removed_feature,
 712         test_runner,
 713         then_with,
 714         thread_local,
 715         tool_attributes,
 716         tool_lints,
 717         trace_macros,
 718         track_caller,
 719         trait_alias,
 720         transmute,
 721         transparent,
 722         transparent_enums,
 723         transparent_unions,
 724         trivial_bounds,
 725         Try,
 726         try_blocks,
 727         try_trait,
 728         tt,
 729         tuple_indexing,
 730         Ty,
 731         ty,
 732         type_alias_impl_trait,
 733         type_id,
 734         type_name,
 735         TyCtxt,
 736         TyKind,
 737         type_alias_enum_variants,
 738         type_ascription,
 739         type_length_limit,
 740         type_macros,
 741         u128,
 742         u16,
 743         u32,
 744         u64,
 745         u8,
 746         unboxed_closures,
 747         unchecked_shl,
 748         unchecked_shr,
 749         underscore_const_names,
 750         underscore_imports,
 751         underscore_lifetimes,
 752         uniform_paths,
 753         universal_impl_trait,
 754         unmarked_api,
 755         unreachable_code,
 756         unrestricted_attribute_tokens,
 757         unsafe_no_drop_flag,
 758         unsized_locals,
 759         unsized_tuple_coercion,
 760         unstable,
 761         untagged_unions,
 762         unwind,
 763         unwind_attributes,
 764         unwrap_or,
 765         used,
 766         use_extern_macros,
 767         use_nested_groups,
 768         usize,
 769         v1,
 770         val,
 771         vec,
 772         Vec,
 773         vis,
 774         visible_private_types,
 775         volatile,
 776         warn,
 777         wasm_import_module,
 778         wasm_target_feature,
 779         while_let,
 780         windows,
 781         windows_subsystem,
 782         wrapping_add,
 783         wrapping_sub,
 784         wrapping_mul,
 785         Yield,
 786     }
 787 }
 788
 789 #[derive(Copy, Clone, Eq, HashStable_Generic)]
 790 pub struct Ident {
 791     pub name: Symbol,
 792     pub span: Span,
 793 }
 794
 795 impl Ident {
 796     #[inline]
 797     /// Constructs a new identifier from a symbol and a span.
 798     pub const fn new(name: Symbol, span: Span) -> Ident {
 799         Ident { name, span }
 800     }
 801
 802     /// Constructs a new identifier with a dummy span.
 803     #[inline]
 804     pub const fn with_dummy_span(name: Symbol) -> Ident {
 805         Ident::new(name, DUMMY_SP)
 806     }
 807
 808     #[inline]
 809     pub fn invalid() -> Ident {
 810         Ident::with_dummy_span(kw::Invalid)
 811     }
 812
 813     /// Maps a string to an identifier with a dummy span.
 814     pub fn from_str(string: &str) -> Ident {
 815         Ident::with_dummy_span(Symbol::intern(string))
 816     }
 817
 818     /// Maps a string and a span to an identifier.
 819     pub fn from_str_and_span(string: &str, span: Span) -> Ident {
 820         Ident::new(Symbol::intern(string), span)
 821     }
 822
 823     /// Replaces `lo` and `hi` with those from `span`, but keep hygiene context.
 824     pub fn with_span_pos(self, span: Span) -> Ident {
 825         Ident::new(self.name, span.with_ctxt(self.span.ctxt()))
 826     }
 827
 828     pub fn without_first_quote(self) -> Ident {
 829         Ident::new(Symbol::intern(self.as_str().trim_start_matches('\'')), self.span)
 830     }
 831
 832     /// "Normalize" ident for use in comparisons using "item hygiene".
 833     /// Identifiers with same string value become same if they came from the same "modern" macro
 834     /// (e.g., `macro` item, but not `macro_rules` item) and stay different if they came from
 835     /// different "modern" macros.
 836     /// Technically, this operation strips all non-opaque marks from ident's syntactic context.
 837     pub fn modern(self) -> Ident {
 838         Ident::new(self.name, self.span.modern())
 839     }
 840
 841     /// "Normalize" ident for use in comparisons using "local variable hygiene".
 842     /// Identifiers with same string value become same if they came from the same non-transparent
 843     /// macro (e.g., `macro` or `macro_rules!` items) and stay different if they came from different
 844     /// non-transparent macros.
 845     /// Technically, this operation strips all transparent marks from ident's syntactic context.
 846     pub fn modern_and_legacy(self) -> Ident {
 847         Ident::new(self.name, self.span.modern_and_legacy())
 848     }
 849
 850     /// Convert the name to a `SymbolStr`. This is a slowish operation because
 851     /// it requires locking the symbol interner.
 852     pub fn as_str(self) -> SymbolStr {
 853         self.name.as_str()
 854     }
 855 }
 856
 857 impl PartialEq for Ident {
 858     fn eq(&self, rhs: &Self) -> bool {
 859         self.name == rhs.name && self.span.ctxt() == rhs.span.ctxt()
 860     }
 861 }
 862
 863 impl Hash for Ident {
 864     fn hash<H: Hasher>(&self, state: &mut H) {
 865         self.name.hash(state);
 866         self.span.ctxt().hash(state);
 867     }
 868 }
 869
 870 impl fmt::Debug for Ident {
 871     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 872         if self.is_raw_guess() {
 873             write!(f, "r#")?;
 874         }
 875         write!(f, "{}{:?}", self.name, self.span.ctxt())
 876     }
 877 }
 878
 879 impl fmt::Display for Ident {
 880     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 881         if self.is_raw_guess() {
 882             write!(f, "r#")?;
 883         }
 884         fmt::Display::fmt(&self.name, f)
 885     }
 886 }
 887
 888 impl UseSpecializedEncodable for Ident {
 889     fn default_encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
 890         s.emit_struct("Ident", 2, |s| {
 891             s.emit_struct_field("name", 0, |s| {
 892                 self.name.encode(s)
 893             })?;
 894             s.emit_struct_field("span", 1, |s| {
 895                 self.span.encode(s)
 896             })
 897         })
 898     }
 899 }
 900
 901 impl UseSpecializedDecodable for Ident {
 902     fn default_decode<D: Decoder>(d: &mut D) -> Result<Self, D::Error> {
 903         d.read_struct("Ident", 2, |d| {
 904             Ok(Ident {
 905                 name: d.read_struct_field("name", 0, Decodable::decode)?,
 906                 span: d.read_struct_field("span", 1, Decodable::decode)?,
 907             })
 908         })
 909     }
 910 }
 911
 912 /// An interned string.
 913 ///
 914 /// Internally, a `Symbol` is implemented as an index, and all operations
 915 /// (including hashing, equality, and ordering) operate on that index. The use
 916 /// of `rustc_index::newtype_index!` means that `Option<Symbol>` only takes up 4 bytes,
 917 /// because `rustc_index::newtype_index!` reserves the last 256 values for tagging purposes.
 918 ///
 919 /// Note that `Symbol` cannot directly be a `rustc_index::newtype_index!` because it
 920 /// implements `fmt::Debug`, `Encodable`, and `Decodable` in special ways.
 921 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
 922 pub struct Symbol(SymbolIndex);
 923
 924 rustc_index::newtype_index! {
 925     pub struct SymbolIndex { .. }
 926 }
 927
 928 impl Symbol {
 929     const fn new(n: u32) -> Self {
 930         Symbol(SymbolIndex::from_u32_const(n))
 931     }
 932
 933     /// Maps a string to its interned representation.
 934     pub fn intern(string: &str) -> Self {
 935         with_interner(|interner| interner.intern(string))
 936     }
 937
 938     /// Access the symbol's chars. This is a slowish operation because it
 939     /// requires locking the symbol interner.
 940     pub fn with<F: FnOnce(&str) -> R, R>(self, f: F) -> R {
 941         with_interner(|interner| {
 942             f(interner.get(self))
 943         })
 944     }
 945
 946     /// Convert to a `SymbolStr`. This is a slowish operation because it
 947     /// requires locking the symbol interner.
 948     pub fn as_str(self) -> SymbolStr {
 949         with_interner(|interner| unsafe {
 950             SymbolStr {
 951                 string: std::mem::transmute::<&str, &str>(interner.get(self))
 952             }
 953         })
 954     }
 955
 956     pub fn as_u32(self) -> u32 {
 957         self.0.as_u32()
 958     }
 959 }
 960
 961 impl fmt::Debug for Symbol {
 962     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 963         self.with(|str| fmt::Debug::fmt(&str, f))
 964     }
 965 }
 966
 967 impl fmt::Display for Symbol {
 968     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 969         self.with(|str| fmt::Display::fmt(&str, f))
 970     }
 971 }
 972
 973 impl Encodable for Symbol {
 974     fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
 975         self.with(|string| s.emit_str(string))
 976     }
 977 }
 978
 979 impl Decodable for Symbol {
 980     fn decode<D: Decoder>(d: &mut D) -> Result<Symbol, D::Error> {
 981         Ok(Symbol::intern(&d.read_str()?))
 982     }
 983 }
 984
 985 impl<CTX> HashStable<CTX> for Symbol {
 986     #[inline]
 987     fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
 988         self.as_str().hash_stable(hcx, hasher);
 989     }
 990 }
 991
 992 impl<CTX> ToStableHashKey<CTX> for Symbol {
 993     type KeyType = SymbolStr;
 994
 995     #[inline]
 996     fn to_stable_hash_key(&self, _: &CTX) -> SymbolStr {
 997         self.as_str()
 998     }
 999 }
1000
1001 // The `&'static str`s in this type actually point into the arena.
1002 #[derive(Default)]
1003 pub struct Interner {
1004     arena: DroplessArena,
1005     names: FxHashMap<&'static str, Symbol>,
1006     strings: Vec<&'static str>,
1007 }
1008
1009 impl Interner {
1010     fn prefill(init: &[&'static str]) -> Self {
1011         Interner {
1012             strings: init.into(),
1013             names: init.iter().copied().zip((0..).map(Symbol::new)).collect(),
1014             ..Default::default()
1015         }
1016     }
1017
1018     pub fn intern(&mut self, string: &str) -> Symbol {
1019         if let Some(&name) = self.names.get(string) {
1020             return name;
1021         }
1022
1023         let name = Symbol::new(self.strings.len() as u32);
1024
1025         // `from_utf8_unchecked` is safe since we just allocated a `&str` which is known to be
1026         // UTF-8.
1027         let string: &str = unsafe {
1028             str::from_utf8_unchecked(self.arena.alloc_slice(string.as_bytes()))
1029         };
1030         // It is safe to extend the arena allocation to `'static` because we only access
1031         // these while the arena is still alive.
1032         let string: &'static str =  unsafe {
1033             &*(string as *const str)
1034         };
1035         self.strings.push(string);
1036         self.names.insert(string, name);
1037         name
1038     }
1039
1040     // Get the symbol as a string. `Symbol::as_str()` should be used in
1041     // preference to this function.
1042     pub fn get(&self, symbol: Symbol) -> &str {
1043         self.strings[symbol.0.as_usize()]
1044     }
1045 }
1046
1047 // This module has a very short name because it's used a lot.
1048 pub mod kw {
1049     use super::Symbol;
1050     keywords!();
1051 }
1052
1053 // This module has a very short name because it's used a lot.
1054 pub mod sym {
1055     use std::convert::TryInto;
1056     use super::Symbol;
1057
1058     symbols!();
1059
1060     // Get the symbol for an integer. The first few non-negative integers each
1061     // have a static symbol and therefore are fast.
1062     pub fn integer<N: TryInto<usize> + Copy + ToString>(n: N) -> Symbol {
1063         if let Result::Ok(idx) = n.try_into() {
1064             if let Option::Some(&sym) = digits_array.get(idx) {
1065                 return sym;
1066             }
1067         }
1068         Symbol::intern(&n.to_string())
1069     }
1070 }
1071
1072 impl Symbol {
1073     fn is_used_keyword_2018(self) -> bool {
1074         self >= kw::Async && self <= kw::Dyn
1075     }
1076
1077     fn is_unused_keyword_2018(self) -> bool {
1078         self == kw::Try
1079     }
1080
1081     /// Used for sanity checking rustdoc keyword sections.
1082     pub fn is_doc_keyword(self) -> bool {
1083         self <= kw::Union
1084     }
1085
1086     /// A keyword or reserved identifier that can be used as a path segment.
1087     pub fn is_path_segment_keyword(self) -> bool {
1088         self == kw::Super ||
1089         self == kw::SelfLower ||
1090         self == kw::SelfUpper ||
1091         self == kw::Crate ||
1092         self == kw::PathRoot ||
1093         self == kw::DollarCrate
1094     }
1095
1096     /// Returns `true` if the symbol is `true` or `false`.
1097     pub fn is_bool_lit(self) -> bool {
1098         self == kw::True || self == kw::False
1099     }
1100
1101     /// This symbol can be a raw identifier.
1102     pub fn can_be_raw(self) -> bool {
1103         self != kw::Invalid && self != kw::Underscore && !self.is_path_segment_keyword()
1104     }
1105 }
1106
1107 impl Ident {
1108     // Returns `true` for reserved identifiers used internally for elided lifetimes,
1109     // unnamed method parameters, crate root module, error recovery etc.
1110     pub fn is_special(self) -> bool {
1111         self.name <= kw::Underscore
1112     }
1113
1114     /// Returns `true` if the token is a keyword used in the language.
1115     pub fn is_used_keyword(self) -> bool {
1116         // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
1117         self.name >= kw::As && self.name <= kw::While ||
1118         self.name.is_used_keyword_2018() && self.span.rust_2018()
1119     }
1120
1121     /// Returns `true` if the token is a keyword reserved for possible future use.
1122     pub fn is_unused_keyword(self) -> bool {
1123         // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
1124         self.name >= kw::Abstract && self.name <= kw::Yield ||
1125         self.name.is_unused_keyword_2018() && self.span.rust_2018()
1126     }
1127
1128     /// Returns `true` if the token is either a special identifier or a keyword.
1129     pub fn is_reserved(self) -> bool {
1130         self.is_special() || self.is_used_keyword() || self.is_unused_keyword()
1131     }
1132
1133     /// A keyword or reserved identifier that can be used as a path segment.
1134     pub fn is_path_segment_keyword(self) -> bool {
1135         self.name.is_path_segment_keyword()
1136     }
1137
1138     /// We see this identifier in a normal identifier position, like variable name or a type.
1139     /// How was it written originally? Did it use the raw form? Let's try to guess.
1140     pub fn is_raw_guess(self) -> bool {
1141         self.name.can_be_raw() && self.is_reserved()
1142     }
1143 }
1144
1145 #[inline]
1146 fn with_interner<T, F: FnOnce(&mut Interner) -> T>(f: F) -> T {
1147     GLOBALS.with(|globals| f(&mut *globals.symbol_interner.lock()))
1148 }
1149
1150 /// An alternative to `Symbol`, useful when the chars within the symbol need to
1151 /// be accessed. It deliberately has limited functionality and should only be
1152 /// used for temporary values.
1153 ///
1154 /// Because the interner outlives any thread which uses this type, we can
1155 /// safely treat `string` which points to interner data, as an immortal string,
1156 /// as long as this type never crosses between threads.
1157 //
1158 // FIXME: ensure that the interner outlives any thread which uses `SymbolStr`,
1159 // by creating a new thread right after constructing the interner.
1160 #[derive(Clone, Eq, PartialOrd, Ord)]
1161 pub struct SymbolStr {
1162     string: &'static str,
1163 }
1164
1165 // This impl allows a `SymbolStr` to be directly equated with a `String` or
1166 // `&str`.
1167 impl<T: std::ops::Deref<Target = str>> std::cmp::PartialEq<T> for SymbolStr {
1168     fn eq(&self, other: &T) -> bool {
1169         self.string == other.deref()
1170     }
1171 }
1172
1173 impl !Send for SymbolStr {}
1174 impl !Sync for SymbolStr {}
1175
1176 /// This impl means that if `ss` is a `SymbolStr`:
1177 /// - `*ss` is a `str`;
1178 /// - `&*ss` is a `&str`;
1179 /// - `&ss as &str` is a `&str`, which means that `&ss` can be passed to a
1180 ///   function expecting a `&str`.
1181 impl std::ops::Deref for SymbolStr {
1182     type Target = str;
1183     #[inline]
1184     fn deref(&self) -> &str { self.string }
1185 }
1186
1187 impl fmt::Debug for SymbolStr {
1188     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1189         fmt::Debug::fmt(self.string, f)
1190     }
1191 }
1192
1193 impl fmt::Display for SymbolStr {
1194     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1195         fmt::Display::fmt(self.string, f)
1196     }
1197 }
1198
1199 impl<CTX> HashStable<CTX> for SymbolStr {
1200     #[inline]
1201     fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
1202         self.string.hash_stable(hcx, hasher)
1203     }
1204 }
1205
1206 impl<CTX> ToStableHashKey<CTX> for SymbolStr {
1207     type KeyType = SymbolStr;
1208
1209     #[inline]
1210     fn to_stable_hash_key(&self, _: &CTX) -> SymbolStr {
1211         self.clone()
1212     }
1213 }