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.
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_data_structures::sync::Lock;
9 use rustc_macros::HashStable_Generic;
10 use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
12 use std::cmp::{Ord, PartialEq, PartialOrd};
14 use std::hash::{Hash, Hasher};
17 use crate::{with_session_globals, Edition, Span, DUMMY_SP};
22 // The proc macro code for this is in `compiler/rustc_macros/src/symbols.rs`.
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.
27 // Special reserved identifiers used internally for elided lifetimes,
28 // unnamed method parameters, crate root module, error recovery etc.
31 DollarCrate: "$crate",
34 // Keywords that are used in stable Rust.
71 // Keywords that are used in unstable Rust or reserved for future use.
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
90 // Edition-specific keywords that are used in unstable Rust or reserved for future use.
91 Try: "try", // >= 2018 Edition only
93 // Special lifetime names
94 UnderscoreLifetime: "'_",
95 StaticLifetime: "'static",
97 // Weak keywords, have special meaning only in specific contexts.
101 MacroRules: "macro_rules",
106 // Pre-interned symbols that can be referred to with `rustc_span::sym::*`.
108 // The symbol is the stringified identifier unless otherwise specified, in
109 // which case the name should mention the non-identifier punctuation.
110 // E.g. `sym::proc_dash_macro` represents "proc-macro", and it shouldn't be
111 // called `sym::proc_macro` because then it's easy to mistakenly think it
112 // represents "proc_macro".
114 // As well as the symbols listed, there are symbols for the strings
115 // "0", "1", ..., "9", which are accessible via `sym::integer`.
117 // The proc macro will abort if symbols are not in alphabetical order (as
118 // defined by `impl Ord for str`) or if any symbols are duplicated. Vim
119 // users can sort the list by selecting it and executing the command
120 // `:'<,'>!LC_ALL=C sort`.
122 // There is currently no checking that all symbols are used; that would be
229 ProceduralMasqueradeDummyType,
278 aarch64_target_feature,
282 abi_c_cmse_nonsecure_call,
284 abi_msp430_interrupt,
298 advanced_slice_patterns,
313 allow_internal_unsafe,
314 allow_internal_unstable,
320 arbitrary_enum_discriminant,
321 arbitrary_self_types,
333 assert_receiver_is_total_eq,
337 associated_type_bounds,
338 associated_type_defaults,
351 augmented_assignments,
353 automatically_derived,
354 avx512_target_feature,
360 bind_by_move_pattern_guards,
372 borrowck_graphviz_format,
373 borrowck_graphviz_postflow,
374 borrowck_graphviz_preflow,
379 braced_empty_structs,
391 capture_disjoint_fields,
406 cfg_target_has_atomic,
407 cfg_target_thread_local,
419 closure_to_fn_coercion,
420 closure_track_caller,
424 cmpxchg16b_target_feature,
425 cmse_nonsecure_entry,
431 compare_exchange_weak,
437 conservative_impl_trait,
441 const_compare_raw_pointers,
445 const_eval_select_ct,
446 const_evaluatable_checked,
449 const_fn_floating_point_arithmetic,
450 const_fn_fn_ptr_basics,
451 const_fn_trait_bound,
457 const_generic_defaults,
459 const_generics_defaults,
462 const_in_array_repeat_expressions,
469 const_precise_live_drops,
472 const_raw_ptr_to_usize_cast,
475 const_trait_bound_opt_out,
492 core_panic_2015_macro,
502 crate_visibility_modifier,
503 crt_dash_static: "crt-static",
512 custom_inner_attributes,
513 custom_test_frameworks,
526 default_alloc_error_handler,
527 default_lib_allocator,
528 default_method_body_is_const,
529 default_type_parameter_fallback,
531 delay_span_bug_from_inside_query,
540 destructuring_assignment,
560 document_private_items,
561 dotdot_in_tuple_patterns,
562 dotdoteq_in_patterns,
570 dropck_parametricity,
580 emit_enum_variant_arg,
588 ermsb_target_feature,
592 exclusive_range_pattern,
593 exhaustive_integer_patterns,
602 explicit_generic_args_with_impl_trait,
605 extended_key_value_attributes,
606 extern_absolute_paths,
607 extern_crate_item_prelude,
631 field_init_shorthand,
636 float_to_int_unchecked,
667 from_size_align_unchecked,
680 generic_associated_types,
688 half_open_range_patterns,
690 hexagon_target_feature,
692 homogeneous_aggregate,
709 if_while_or_patterns,
711 impl_header_lifetime_elision,
714 impl_trait_in_bindings,
721 inclusive_range_syntax,
724 infer_outlives_requirements,
725 infer_static_outlives_requirements,
726 inherent_associated_types,
736 irrefutable_let_patterns,
740 issue_5723_bootstrap,
741 issue_tracker_base_url,
755 lazy_normalization_consts,
769 link_llvm_intrinsics,
789 macro_at_most_once_rep,
790 macro_attributes_in_derive_output,
793 macro_lifetime_matcher,
794 macro_literal_matcher,
806 match_beginning_vert,
807 match_default_bindings,
834 min_type_alias_impl_trait,
843 more_qualified_paths,
845 movbe_target_feature,
858 native_link_modifiers,
859 native_link_modifiers_as_needed,
860 native_link_modifiers_bundle,
861 native_link_modifiers_verbatim,
862 native_link_modifiers_whole_archive,
899 non_exhaustive_omitted_patterns_lint,
911 object_safe_for_dispatch,
914 omit_gdb_pretty_printer_section,
923 optin_builtin_traits,
931 overlapping_marker_traits,
943 panic_implementation,
970 post_dash_lto: "post-lto",
971 powerpc_target_feature,
976 pre_dash_lto: "pre-lto",
977 precise_pointer_size_matching,
981 prefetch_read_instruction,
983 prefetch_write_instruction,
989 proc_dash_macro: "proc-macro",
991 proc_macro_attribute,
997 proc_macro_internals,
999 proc_macro_non_items,
1000 proc_macro_path_invoc,
1015 quad_precision_float,
1018 range_inclusive_new,
1023 re_rebalance_coherence,
1026 read_enum_variant_arg,
1034 reexport_test_harness_main,
1035 ref_unwind_safe_trait,
1049 relaxed_struct_unsize,
1065 riscv_target_feature,
1081 rust_eh_catch_typeinfo,
1082 rust_eh_personality,
1083 rust_eh_register_frames,
1084 rust_eh_unregister_frames,
1088 rustc_allocator_nounwind,
1089 rustc_allow_const_fn_unstable,
1091 rustc_builtin_macro,
1092 rustc_capture_analysis,
1095 rustc_const_unstable,
1096 rustc_conversion_suggestion,
1099 rustc_diagnostic_item,
1100 rustc_diagnostic_macros,
1102 rustc_do_not_const_check,
1104 rustc_dump_env_program_clauses,
1105 rustc_dump_program_clauses,
1106 rustc_dump_user_substs,
1109 rustc_evaluate_where_clauses,
1110 rustc_expected_cgu_reuse,
1111 rustc_if_this_changed,
1112 rustc_inherit_overflow_checks,
1113 rustc_insignificant_dtor,
1115 rustc_layout_scalar_valid_range_end,
1116 rustc_layout_scalar_valid_range_start,
1117 rustc_legacy_const_generics,
1118 rustc_lint_query_instability,
1119 rustc_macro_transparency,
1122 rustc_nonnull_optimization_guaranteed,
1123 rustc_object_lifetime_default,
1124 rustc_on_unimplemented,
1127 rustc_partition_codegened,
1128 rustc_partition_reused,
1130 rustc_peek_definite_init,
1131 rustc_peek_indirectly_mutable,
1132 rustc_peek_liveness,
1133 rustc_peek_maybe_init,
1134 rustc_peek_maybe_uninit,
1135 rustc_polymorphize_error,
1137 rustc_proc_macro_decls,
1140 rustc_reservation_impl,
1142 rustc_skip_array_during_method_dispatch,
1143 rustc_specialization_trait,
1145 rustc_std_internal_symbol,
1146 rustc_strict_coherence,
1150 rustc_then_this_would_need,
1151 rustc_trivial_field_reads,
1152 rustc_unsafe_specialization_marker,
1156 rvalue_static_promotion,
1205 simd_reduce_add_ordered,
1206 simd_reduce_add_unordered,
1211 simd_reduce_max_nanless,
1213 simd_reduce_min_nanless,
1214 simd_reduce_mul_ordered,
1215 simd_reduce_mul_unordered,
1220 simd_saturating_add,
1221 simd_saturating_sub,
1224 simd_select_bitmask,
1254 sse4a_target_feature,
1266 std_panic_2015_macro,
1269 stmt_expr_attributes,
1270 stop_after_dataflow,
1275 struct_field_attributes,
1297 target_has_atomic_equal_alignment,
1298 target_has_atomic_load_store,
1300 target_pointer_width,
1301 target_target_vendor,
1302 target_thread_local,
1308 termination_trait_test,
1311 test_accepted_feature,
1313 test_removed_feature,
1341 type_alias_enum_variants,
1342 type_alias_impl_trait,
1344 type_changing_struct_update,
1354 unaligned_volatile_load,
1355 unaligned_volatile_store,
1364 underscore_const_names,
1366 underscore_lifetimes,
1369 universal_impl_trait,
1376 unrestricted_attribute_tokens,
1377 unsafe_block_in_unsafe_fn,
1379 unsafe_no_drop_flag,
1383 unsized_tuple_coercion,
1386 unused_qualifications,
1408 visible_private_types,
1410 volatile_copy_memory,
1411 volatile_copy_nonoverlapping_memory,
1413 volatile_set_memory,
1420 wasm_target_feature,
1439 #[derive(Copy, Clone, Eq, HashStable_Generic, Encodable, Decodable)]
1447 /// Constructs a new identifier from a symbol and a span.
1448 pub const fn new(name: Symbol, span: Span) -> Ident {
1449 Ident { name, span }
1452 /// Constructs a new identifier with a dummy span.
1454 pub const fn with_dummy_span(name: Symbol) -> Ident {
1455 Ident::new(name, DUMMY_SP)
1459 pub fn empty() -> Ident {
1460 Ident::with_dummy_span(kw::Empty)
1463 /// Maps a string to an identifier with a dummy span.
1464 pub fn from_str(string: &str) -> Ident {
1465 Ident::with_dummy_span(Symbol::intern(string))
1468 /// Maps a string and a span to an identifier.
1469 pub fn from_str_and_span(string: &str, span: Span) -> Ident {
1470 Ident::new(Symbol::intern(string), span)
1473 /// Replaces `lo` and `hi` with those from `span`, but keep hygiene context.
1474 pub fn with_span_pos(self, span: Span) -> Ident {
1475 Ident::new(self.name, span.with_ctxt(self.span.ctxt()))
1478 pub fn without_first_quote(self) -> Ident {
1479 Ident::new(Symbol::intern(self.as_str().trim_start_matches('\'')), self.span)
1482 /// "Normalize" ident for use in comparisons using "item hygiene".
1483 /// Identifiers with same string value become same if they came from the same macro 2.0 macro
1484 /// (e.g., `macro` item, but not `macro_rules` item) and stay different if they came from
1485 /// different macro 2.0 macros.
1486 /// Technically, this operation strips all non-opaque marks from ident's syntactic context.
1487 pub fn normalize_to_macros_2_0(self) -> Ident {
1488 Ident::new(self.name, self.span.normalize_to_macros_2_0())
1491 /// "Normalize" ident for use in comparisons using "local variable hygiene".
1492 /// Identifiers with same string value become same if they came from the same non-transparent
1493 /// macro (e.g., `macro` or `macro_rules!` items) and stay different if they came from different
1494 /// non-transparent macros.
1495 /// Technically, this operation strips all transparent marks from ident's syntactic context.
1496 pub fn normalize_to_macro_rules(self) -> Ident {
1497 Ident::new(self.name, self.span.normalize_to_macro_rules())
1500 /// Convert the name to a `SymbolStr`. This is a slowish operation because
1501 /// it requires locking the symbol interner.
1502 pub fn as_str(self) -> SymbolStr {
1507 impl PartialEq for Ident {
1508 fn eq(&self, rhs: &Self) -> bool {
1509 self.name == rhs.name && self.span.ctxt() == rhs.span.ctxt()
1513 impl Hash for Ident {
1514 fn hash<H: Hasher>(&self, state: &mut H) {
1515 self.name.hash(state);
1516 self.span.ctxt().hash(state);
1520 impl fmt::Debug for Ident {
1521 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1522 fmt::Display::fmt(self, f)?;
1523 fmt::Debug::fmt(&self.span.ctxt(), f)
1527 /// This implementation is supposed to be used in error messages, so it's expected to be identical
1528 /// to printing the original identifier token written in source code (`token_to_string`),
1529 /// except that AST identifiers don't keep the rawness flag, so we have to guess it.
1530 impl fmt::Display for Ident {
1531 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1532 fmt::Display::fmt(&IdentPrinter::new(self.name, self.is_raw_guess(), None), f)
1536 /// This is the most general way to print identifiers.
1537 /// AST pretty-printer is used as a fallback for turning AST structures into token streams for
1538 /// proc macros. Additionally, proc macros may stringify their input and expect it survive the
1539 /// stringification (especially true for proc macro derives written between Rust 1.15 and 1.30).
1540 /// So we need to somehow pretty-print `$crate` in a way preserving at least some of its
1541 /// hygiene data, most importantly name of the crate it refers to.
1542 /// As a result we print `$crate` as `crate` if it refers to the local crate
1543 /// and as `::other_crate_name` if it refers to some other crate.
1544 /// Note, that this is only done if the ident token is printed from inside of AST pretty-pringing,
1545 /// but not otherwise. Pretty-printing is the only way for proc macros to discover token contents,
1546 /// so we should not perform this lossy conversion if the top level call to the pretty-printer was
1547 /// done for a token stream or a single token.
1548 pub struct IdentPrinter {
1551 /// Span used for retrieving the crate name to which `$crate` refers to,
1552 /// if this field is `None` then the `$crate` conversion doesn't happen.
1553 convert_dollar_crate: Option<Span>,
1557 /// The most general `IdentPrinter` constructor. Do not use this.
1558 pub fn new(symbol: Symbol, is_raw: bool, convert_dollar_crate: Option<Span>) -> IdentPrinter {
1559 IdentPrinter { symbol, is_raw, convert_dollar_crate }
1562 /// This implementation is supposed to be used when printing identifiers
1563 /// as a part of pretty-printing for larger AST pieces.
1564 /// Do not use this either.
1565 pub fn for_ast_ident(ident: Ident, is_raw: bool) -> IdentPrinter {
1566 IdentPrinter::new(ident.name, is_raw, Some(ident.span))
1570 impl fmt::Display for IdentPrinter {
1571 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1574 } else if self.symbol == kw::DollarCrate {
1575 if let Some(span) = self.convert_dollar_crate {
1576 let converted = span.ctxt().dollar_crate_name();
1577 if !converted.is_path_segment_keyword() {
1580 return fmt::Display::fmt(&converted, f);
1583 fmt::Display::fmt(&self.symbol, f)
1587 /// An newtype around `Ident` that calls [Ident::normalize_to_macro_rules] on
1589 // FIXME(matthewj, petrochenkov) Use this more often, add a similar
1590 // `ModernIdent` struct and use that as well.
1591 #[derive(Copy, Clone, Eq, PartialEq, Hash)]
1592 pub struct MacroRulesNormalizedIdent(Ident);
1594 impl MacroRulesNormalizedIdent {
1595 pub fn new(ident: Ident) -> Self {
1596 Self(ident.normalize_to_macro_rules())
1600 impl fmt::Debug for MacroRulesNormalizedIdent {
1601 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1602 fmt::Debug::fmt(&self.0, f)
1606 impl fmt::Display for MacroRulesNormalizedIdent {
1607 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1608 fmt::Display::fmt(&self.0, f)
1612 /// An interned string.
1614 /// Internally, a `Symbol` is implemented as an index, and all operations
1615 /// (including hashing, equality, and ordering) operate on that index. The use
1616 /// of `rustc_index::newtype_index!` means that `Option<Symbol>` only takes up 4 bytes,
1617 /// because `rustc_index::newtype_index!` reserves the last 256 values for tagging purposes.
1619 /// Note that `Symbol` cannot directly be a `rustc_index::newtype_index!` because it
1620 /// implements `fmt::Debug`, `Encodable`, and `Decodable` in special ways.
1621 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
1622 pub struct Symbol(SymbolIndex);
1624 rustc_index::newtype_index! {
1625 struct SymbolIndex { .. }
1629 const fn new(n: u32) -> Self {
1630 Symbol(SymbolIndex::from_u32(n))
1633 /// Maps a string to its interned representation.
1634 pub fn intern(string: &str) -> Self {
1635 with_session_globals(|session_globals| session_globals.symbol_interner.intern(string))
1638 /// Convert to a `SymbolStr`. This is a slowish operation because it
1639 /// requires locking the symbol interner.
1640 pub fn as_str(self) -> SymbolStr {
1641 with_session_globals(|session_globals| {
1642 let symbol_str = session_globals.symbol_interner.get(self);
1643 unsafe { SymbolStr { string: std::mem::transmute::<&str, &str>(symbol_str) } }
1647 pub fn as_u32(self) -> u32 {
1651 pub fn is_empty(self) -> bool {
1655 /// This method is supposed to be used in error messages, so it's expected to be
1656 /// identical to printing the original identifier token written in source code
1657 /// (`token_to_string`, `Ident::to_string`), except that symbols don't keep the rawness flag
1658 /// or edition, so we have to guess the rawness using the global edition.
1659 pub fn to_ident_string(self) -> String {
1660 Ident::with_dummy_span(self).to_string()
1664 impl fmt::Debug for Symbol {
1665 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1666 fmt::Debug::fmt(&self.as_str(), f)
1670 impl fmt::Display for Symbol {
1671 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1672 fmt::Display::fmt(&self.as_str(), f)
1676 impl<S: Encoder> Encodable<S> for Symbol {
1677 fn encode(&self, s: &mut S) -> Result<(), S::Error> {
1678 s.emit_str(&self.as_str())
1682 impl<D: Decoder> Decodable<D> for Symbol {
1684 fn decode(d: &mut D) -> Result<Symbol, D::Error> {
1685 Ok(Symbol::intern(&d.read_str()?))
1689 impl<CTX> HashStable<CTX> for Symbol {
1691 fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
1692 self.as_str().hash_stable(hcx, hasher);
1696 impl<CTX> ToStableHashKey<CTX> for Symbol {
1697 type KeyType = SymbolStr;
1700 fn to_stable_hash_key(&self, _: &CTX) -> SymbolStr {
1706 pub(crate) struct Interner(Lock<InternerInner>);
1708 // The `&'static str`s in this type actually point into the arena.
1710 // The `FxHashMap`+`Vec` pair could be replaced by `FxIndexSet`, but #75278
1711 // found that to regress performance up to 2% in some cases. This might be
1712 // revisited after further improvements to `indexmap`.
1714 // This type is private to prevent accidentally constructing more than one `Interner` on the same
1715 // thread, which makes it easy to mixup `Symbol`s between `Interner`s.
1717 struct InternerInner {
1718 arena: DroplessArena,
1719 names: FxHashMap<&'static str, Symbol>,
1720 strings: Vec<&'static str>,
1724 fn prefill(init: &[&'static str]) -> Self {
1725 Interner(Lock::new(InternerInner {
1726 strings: init.into(),
1727 names: init.iter().copied().zip((0..).map(Symbol::new)).collect(),
1728 ..Default::default()
1733 fn intern(&self, string: &str) -> Symbol {
1734 let mut inner = self.0.lock();
1735 if let Some(&name) = inner.names.get(string) {
1739 let name = Symbol::new(inner.strings.len() as u32);
1741 // `from_utf8_unchecked` is safe since we just allocated a `&str` which is known to be
1744 unsafe { str::from_utf8_unchecked(inner.arena.alloc_slice(string.as_bytes())) };
1745 // It is safe to extend the arena allocation to `'static` because we only access
1746 // these while the arena is still alive.
1747 let string: &'static str = unsafe { &*(string as *const str) };
1748 inner.strings.push(string);
1749 inner.names.insert(string, name);
1753 // Get the symbol as a string. `Symbol::as_str()` should be used in
1754 // preference to this function.
1755 fn get(&self, symbol: Symbol) -> &str {
1756 self.0.lock().strings[symbol.0.as_usize()]
1760 // This module has a very short name because it's used a lot.
1761 /// This module contains all the defined keyword `Symbol`s.
1763 /// Given that `kw` is imported, use them like `kw::keyword_name`.
1764 /// For example `kw::Loop` or `kw::Break`.
1766 pub use super::kw_generated::*;
1769 // This module has a very short name because it's used a lot.
1770 /// This module contains all the defined non-keyword `Symbol`s.
1772 /// Given that `sym` is imported, use them like `sym::symbol_name`.
1773 /// For example `sym::rustfmt` or `sym::u8`.
1776 use std::convert::TryInto;
1779 pub use super::sym_generated::*;
1781 // Used from a macro in `librustc_feature/accepted.rs`
1782 pub use super::kw::MacroRules as macro_rules;
1784 /// Get the symbol for an integer.
1786 /// The first few non-negative integers each have a static symbol and therefore
1788 pub fn integer<N: TryInto<usize> + Copy + ToString>(n: N) -> Symbol {
1789 if let Result::Ok(idx) = n.try_into() {
1791 return Symbol::new(super::SYMBOL_DIGITS_BASE + idx as u32);
1794 Symbol::intern(&n.to_string())
1799 fn is_special(self) -> bool {
1800 self <= kw::Underscore
1803 fn is_used_keyword_always(self) -> bool {
1804 self >= kw::As && self <= kw::While
1807 fn is_used_keyword_conditional(self, edition: impl FnOnce() -> Edition) -> bool {
1808 (self >= kw::Async && self <= kw::Dyn) && edition() >= Edition::Edition2018
1811 fn is_unused_keyword_always(self) -> bool {
1812 self >= kw::Abstract && self <= kw::Yield
1815 fn is_unused_keyword_conditional(self, edition: impl FnOnce() -> Edition) -> bool {
1816 self == kw::Try && edition() >= Edition::Edition2018
1819 pub fn is_reserved(self, edition: impl Copy + FnOnce() -> Edition) -> bool {
1821 || self.is_used_keyword_always()
1822 || self.is_unused_keyword_always()
1823 || self.is_used_keyword_conditional(edition)
1824 || self.is_unused_keyword_conditional(edition)
1827 /// A keyword or reserved identifier that can be used as a path segment.
1828 pub fn is_path_segment_keyword(self) -> bool {
1830 || self == kw::SelfLower
1831 || self == kw::SelfUpper
1832 || self == kw::Crate
1833 || self == kw::PathRoot
1834 || self == kw::DollarCrate
1837 /// Returns `true` if the symbol is `true` or `false`.
1838 pub fn is_bool_lit(self) -> bool {
1839 self == kw::True || self == kw::False
1842 /// Returns `true` if this symbol can be a raw identifier.
1843 pub fn can_be_raw(self) -> bool {
1844 self != kw::Empty && self != kw::Underscore && !self.is_path_segment_keyword()
1849 // Returns `true` for reserved identifiers used internally for elided lifetimes,
1850 // unnamed method parameters, crate root module, error recovery etc.
1851 pub fn is_special(self) -> bool {
1852 self.name.is_special()
1855 /// Returns `true` if the token is a keyword used in the language.
1856 pub fn is_used_keyword(self) -> bool {
1857 // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
1858 self.name.is_used_keyword_always()
1859 || self.name.is_used_keyword_conditional(|| self.span.edition())
1862 /// Returns `true` if the token is a keyword reserved for possible future use.
1863 pub fn is_unused_keyword(self) -> bool {
1864 // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
1865 self.name.is_unused_keyword_always()
1866 || self.name.is_unused_keyword_conditional(|| self.span.edition())
1869 /// Returns `true` if the token is either a special identifier or a keyword.
1870 pub fn is_reserved(self) -> bool {
1871 // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
1872 self.name.is_reserved(|| self.span.edition())
1875 /// A keyword or reserved identifier that can be used as a path segment.
1876 pub fn is_path_segment_keyword(self) -> bool {
1877 self.name.is_path_segment_keyword()
1880 /// We see this identifier in a normal identifier position, like variable name or a type.
1881 /// How was it written originally? Did it use the raw form? Let's try to guess.
1882 pub fn is_raw_guess(self) -> bool {
1883 self.name.can_be_raw() && self.is_reserved()
1887 /// An alternative to [`Symbol`], useful when the chars within the symbol need to
1888 /// be accessed. It deliberately has limited functionality and should only be
1889 /// used for temporary values.
1891 /// Because the interner outlives any thread which uses this type, we can
1892 /// safely treat `string` which points to interner data, as an immortal string,
1893 /// as long as this type never crosses between threads.
1895 // FIXME: ensure that the interner outlives any thread which uses `SymbolStr`,
1896 // by creating a new thread right after constructing the interner.
1897 #[derive(Clone, Eq, PartialOrd, Ord)]
1898 pub struct SymbolStr {
1899 string: &'static str,
1902 // This impl allows a `SymbolStr` to be directly equated with a `String` or
1904 impl<T: std::ops::Deref<Target = str>> std::cmp::PartialEq<T> for SymbolStr {
1905 fn eq(&self, other: &T) -> bool {
1906 self.string == other.deref()
1910 impl !Send for SymbolStr {}
1911 impl !Sync for SymbolStr {}
1913 /// This impl means that if `ss` is a `SymbolStr`:
1914 /// - `*ss` is a `str`;
1915 /// - `&*ss` is a `&str` (and `match &*ss { ... }` is a common pattern).
1916 /// - `&ss as &str` is a `&str`, which means that `&ss` can be passed to a
1917 /// function expecting a `&str`.
1918 impl std::ops::Deref for SymbolStr {
1921 fn deref(&self) -> &str {
1926 impl fmt::Debug for SymbolStr {
1927 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1928 fmt::Debug::fmt(self.string, f)
1932 impl fmt::Display for SymbolStr {
1933 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1934 fmt::Display::fmt(self.string, f)
1938 impl<CTX> HashStable<CTX> for SymbolStr {
1940 fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
1941 self.string.hash_stable(hcx, hasher)
1945 impl<CTX> ToStableHashKey<CTX> for SymbolStr {
1946 type KeyType = SymbolStr;
1949 fn to_stable_hash_key(&self, _: &CTX) -> SymbolStr {