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_macros::HashStable_Generic;
9 use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
11 use std::cmp::{Ord, PartialEq, PartialOrd};
13 use std::hash::{Hash, Hasher};
16 use crate::{Edition, Span, DUMMY_SP, SESSION_GLOBALS};
21 // The proc macro code for this is in `src/librustc_macros/src/symbols.rs`.
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.
26 // Special reserved identifiers used internally for elided lifetimes,
27 // unnamed method parameters, crate root module, error recovery etc.
30 DollarCrate: "$crate",
33 // Keywords that are used in stable Rust.
70 // Keywords that are used in unstable Rust or reserved for future use.
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
89 // Edition-specific keywords that are used in unstable Rust or reserved for future use.
90 Try: "try", // >= 2018 Edition only
92 // Special lifetime names
93 UnderscoreLifetime: "'_",
94 StaticLifetime: "'static",
96 // Weak keywords, have special meaning only in specific contexts.
100 MacroRules: "macro_rules",
105 // Pre-interned symbols that can be referred to with `rustc_span::sym::*`.
107 // The symbol is the stringified identifier unless otherwise specified, in
108 // which case the name should mention the non-identifier punctuation.
109 // E.g. `sym::proc_dash_macro` represents "proc-macro", and it shouldn't be
110 // called `sym::proc_macro` because then it's easy to mistakenly think it
111 // represents "proc_macro".
113 // As well as the symbols listed, there are symbols for the strings
114 // "0", "1", ..., "9", which are accessible via `sym::integer`.
116 // The proc macro will abort if symbols are not in alphabetical order (as
117 // defined by `impl Ord for str`) or if any symbols are duplicated. Vim
118 // users can sort the list by selecting it and executing the command
119 // `:'<,'>!LC_ALL=C sort`.
121 // There is currently no checking that all symbols are used; that would be
185 ProceduralMasqueradeDummyType,
225 aarch64_target_feature,
229 abi_c_cmse_nonsecure_call,
231 abi_msp430_interrupt,
244 advanced_slice_patterns,
259 allow_internal_unsafe,
260 allow_internal_unstable,
266 arbitrary_enum_discriminant,
267 arbitrary_self_types,
279 assert_receiver_is_total_eq,
283 associated_type_bounds,
284 associated_type_defaults,
295 augmented_assignments,
297 automatically_derived,
298 avx512_target_feature,
304 bind_by_move_pattern_guards,
315 borrowck_graphviz_format,
316 borrowck_graphviz_postflow,
317 borrowck_graphviz_preflow,
321 braced_empty_structs,
331 capture_disjoint_fields,
343 cfg_target_has_atomic,
344 cfg_target_thread_local,
354 closure_to_fn_coercion,
356 cmpxchg16b_target_feature,
357 cmse_nonsecure_entry,
365 conservative_impl_trait,
368 const_compare_raw_pointers,
371 const_evaluatable_checked,
374 const_fn_floating_point_arithmetic,
375 const_fn_fn_ptr_basics,
379 const_generics_defaults,
382 const_in_array_repeat_expressions,
388 const_precise_live_drops,
391 const_raw_ptr_to_usize_cast,
394 const_trait_bound_opt_out,
410 core_panic_2015_macro,
419 crate_visibility_modifier,
420 crt_dash_static: "crt-static",
429 custom_inner_attributes,
430 custom_test_frameworks,
444 default_alloc_error_handler,
445 default_lib_allocator,
446 default_type_parameter_fallback,
448 delay_span_bug_from_inside_query,
456 destructuring_assignment,
472 document_private_items,
473 dotdot_in_tuple_patterns,
474 dotdoteq_in_patterns,
482 dropck_parametricity,
491 emit_enum_variant_arg,
499 ermsb_target_feature,
504 exclusive_range_pattern,
505 exhaustive_integer_patterns,
516 extended_key_value_attributes,
517 extern_absolute_paths,
518 extern_crate_item_prelude,
540 field_init_shorthand,
545 float_to_int_unchecked,
572 from_size_align_unchecked,
585 generic_associated_types,
592 half_open_range_patterns,
594 hexagon_target_feature,
596 homogeneous_aggregate,
613 if_while_or_patterns,
615 impl_header_lifetime_elision,
618 impl_trait_in_bindings,
624 inclusive_range_syntax,
627 infer_outlives_requirements,
628 infer_static_outlives_requirements,
640 irrefutable_let_patterns,
644 issue_5723_bootstrap,
645 issue_tracker_base_url,
657 lazy_normalization_consts,
669 link_llvm_intrinsics,
688 macro_at_most_once_rep,
689 macro_attributes_in_derive_output,
692 macro_lifetime_matcher,
693 macro_literal_matcher,
705 match_beginning_vert,
706 match_default_bindings,
733 movbe_target_feature,
782 nontrapping_dash_fptoint: "nontrapping-fptoint",
787 object_safe_for_dispatch,
790 omit_gdb_pretty_printer_section,
799 optin_builtin_traits,
808 overlapping_marker_traits,
818 panic_implementation,
848 post_dash_lto: "post-lto",
849 powerpc_target_feature,
854 pre_dash_lto: "pre-lto",
855 precise_pointer_size_matching,
859 prefetch_read_instruction,
861 prefetch_write_instruction,
866 proc_dash_macro: "proc-macro",
868 proc_macro_attribute,
874 proc_macro_internals,
876 proc_macro_non_items,
877 proc_macro_path_invoc,
889 quad_precision_float,
896 re_rebalance_coherence,
899 read_enum_variant_arg,
907 reexport_test_harness_main,
920 relaxed_struct_unsize,
936 riscv_target_feature,
949 rust_eh_catch_typeinfo,
951 rust_eh_register_frames,
952 rust_eh_unregister_frames,
956 rustc_allocator_nounwind,
957 rustc_allow_const_fn_unstable,
958 rustc_args_required_const,
961 rustc_capture_analysis,
964 rustc_const_unstable,
965 rustc_conversion_suggestion,
968 rustc_diagnostic_item,
969 rustc_diagnostic_macros,
972 rustc_dump_env_program_clauses,
973 rustc_dump_program_clauses,
974 rustc_dump_user_substs,
976 rustc_expected_cgu_reuse,
977 rustc_if_this_changed,
978 rustc_inherit_overflow_checks,
980 rustc_layout_scalar_valid_range_end,
981 rustc_layout_scalar_valid_range_start,
982 rustc_macro_transparency,
984 rustc_nonnull_optimization_guaranteed,
985 rustc_object_lifetime_default,
986 rustc_on_unimplemented,
989 rustc_partition_codegened,
990 rustc_partition_reused,
992 rustc_peek_definite_init,
993 rustc_peek_indirectly_mutable,
995 rustc_peek_maybe_init,
996 rustc_peek_maybe_uninit,
997 rustc_polymorphize_error,
999 rustc_proc_macro_decls,
1002 rustc_reservation_impl,
1004 rustc_specialization_trait,
1006 rustc_std_internal_symbol,
1010 rustc_then_this_would_need,
1011 rustc_unsafe_specialization_marker,
1014 rvalue_static_promotion,
1062 simd_reduce_add_ordered,
1063 simd_reduce_add_unordered,
1068 simd_reduce_max_nanless,
1070 simd_reduce_min_nanless,
1071 simd_reduce_mul_ordered,
1072 simd_reduce_mul_unordered,
1076 simd_saturating_add,
1077 simd_saturating_sub,
1080 simd_select_bitmask,
1106 sse4a_target_feature,
1118 std_panic_2015_macro,
1121 stmt_expr_attributes,
1122 stop_after_dataflow,
1127 struct_field_attributes,
1149 target_has_atomic_equal_alignment,
1150 target_has_atomic_load_store,
1152 target_pointer_width,
1153 target_target_vendor,
1154 target_thread_local,
1160 termination_trait_test,
1163 test_accepted_feature,
1165 test_removed_feature,
1192 type_alias_enum_variants,
1193 type_alias_impl_trait,
1204 unaligned_volatile_load,
1205 unaligned_volatile_store,
1214 underscore_const_names,
1216 underscore_lifetimes,
1219 universal_impl_trait,
1226 unrestricted_attribute_tokens,
1227 unsafe_block_in_unsafe_fn,
1229 unsafe_no_drop_flag,
1233 unsized_tuple_coercion,
1236 unused_qualifications,
1258 visible_private_types,
1260 volatile_copy_memory,
1261 volatile_copy_nonoverlapping_memory,
1263 volatile_set_memory,
1269 wasm_target_feature,
1284 #[derive(Copy, Clone, Eq, HashStable_Generic, Encodable, Decodable)]
1292 /// Constructs a new identifier from a symbol and a span.
1293 pub const fn new(name: Symbol, span: Span) -> Ident {
1294 Ident { name, span }
1297 /// Constructs a new identifier with a dummy span.
1299 pub const fn with_dummy_span(name: Symbol) -> Ident {
1300 Ident::new(name, DUMMY_SP)
1304 pub fn invalid() -> Ident {
1305 Ident::with_dummy_span(kw::Empty)
1308 /// Maps a string to an identifier with a dummy span.
1309 pub fn from_str(string: &str) -> Ident {
1310 Ident::with_dummy_span(Symbol::intern(string))
1313 /// Maps a string and a span to an identifier.
1314 pub fn from_str_and_span(string: &str, span: Span) -> Ident {
1315 Ident::new(Symbol::intern(string), span)
1318 /// Replaces `lo` and `hi` with those from `span`, but keep hygiene context.
1319 pub fn with_span_pos(self, span: Span) -> Ident {
1320 Ident::new(self.name, span.with_ctxt(self.span.ctxt()))
1323 pub fn without_first_quote(self) -> Ident {
1324 Ident::new(Symbol::intern(self.as_str().trim_start_matches('\'')), self.span)
1327 /// "Normalize" ident for use in comparisons using "item hygiene".
1328 /// Identifiers with same string value become same if they came from the same macro 2.0 macro
1329 /// (e.g., `macro` item, but not `macro_rules` item) and stay different if they came from
1330 /// different macro 2.0 macros.
1331 /// Technically, this operation strips all non-opaque marks from ident's syntactic context.
1332 pub fn normalize_to_macros_2_0(self) -> Ident {
1333 Ident::new(self.name, self.span.normalize_to_macros_2_0())
1336 /// "Normalize" ident for use in comparisons using "local variable hygiene".
1337 /// Identifiers with same string value become same if they came from the same non-transparent
1338 /// macro (e.g., `macro` or `macro_rules!` items) and stay different if they came from different
1339 /// non-transparent macros.
1340 /// Technically, this operation strips all transparent marks from ident's syntactic context.
1341 pub fn normalize_to_macro_rules(self) -> Ident {
1342 Ident::new(self.name, self.span.normalize_to_macro_rules())
1345 /// Convert the name to a `SymbolStr`. This is a slowish operation because
1346 /// it requires locking the symbol interner.
1347 pub fn as_str(self) -> SymbolStr {
1352 impl PartialEq for Ident {
1353 fn eq(&self, rhs: &Self) -> bool {
1354 self.name == rhs.name && self.span.ctxt() == rhs.span.ctxt()
1358 impl Hash for Ident {
1359 fn hash<H: Hasher>(&self, state: &mut H) {
1360 self.name.hash(state);
1361 self.span.ctxt().hash(state);
1365 impl fmt::Debug for Ident {
1366 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1367 fmt::Display::fmt(self, f)?;
1368 fmt::Debug::fmt(&self.span.ctxt(), f)
1372 /// This implementation is supposed to be used in error messages, so it's expected to be identical
1373 /// to printing the original identifier token written in source code (`token_to_string`),
1374 /// except that AST identifiers don't keep the rawness flag, so we have to guess it.
1375 impl fmt::Display for Ident {
1376 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1377 fmt::Display::fmt(&IdentPrinter::new(self.name, self.is_raw_guess(), None), f)
1381 /// This is the most general way to print identifiers.
1382 /// AST pretty-printer is used as a fallback for turning AST structures into token streams for
1383 /// proc macros. Additionally, proc macros may stringify their input and expect it survive the
1384 /// stringification (especially true for proc macro derives written between Rust 1.15 and 1.30).
1385 /// So we need to somehow pretty-print `$crate` in a way preserving at least some of its
1386 /// hygiene data, most importantly name of the crate it refers to.
1387 /// As a result we print `$crate` as `crate` if it refers to the local crate
1388 /// and as `::other_crate_name` if it refers to some other crate.
1389 /// Note, that this is only done if the ident token is printed from inside of AST pretty-pringing,
1390 /// but not otherwise. Pretty-printing is the only way for proc macros to discover token contents,
1391 /// so we should not perform this lossy conversion if the top level call to the pretty-printer was
1392 /// done for a token stream or a single token.
1393 pub struct IdentPrinter {
1396 /// Span used for retrieving the crate name to which `$crate` refers to,
1397 /// if this field is `None` then the `$crate` conversion doesn't happen.
1398 convert_dollar_crate: Option<Span>,
1402 /// The most general `IdentPrinter` constructor. Do not use this.
1403 pub fn new(symbol: Symbol, is_raw: bool, convert_dollar_crate: Option<Span>) -> IdentPrinter {
1404 IdentPrinter { symbol, is_raw, convert_dollar_crate }
1407 /// This implementation is supposed to be used when printing identifiers
1408 /// as a part of pretty-printing for larger AST pieces.
1409 /// Do not use this either.
1410 pub fn for_ast_ident(ident: Ident, is_raw: bool) -> IdentPrinter {
1411 IdentPrinter::new(ident.name, is_raw, Some(ident.span))
1415 impl fmt::Display for IdentPrinter {
1416 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1419 } else if self.symbol == kw::DollarCrate {
1420 if let Some(span) = self.convert_dollar_crate {
1421 let converted = span.ctxt().dollar_crate_name();
1422 if !converted.is_path_segment_keyword() {
1425 return fmt::Display::fmt(&converted, f);
1428 fmt::Display::fmt(&self.symbol, f)
1432 /// An newtype around `Ident` that calls [Ident::normalize_to_macro_rules] on
1434 // FIXME(matthewj, petrochenkov) Use this more often, add a similar
1435 // `ModernIdent` struct and use that as well.
1436 #[derive(Copy, Clone, Eq, PartialEq, Hash)]
1437 pub struct MacroRulesNormalizedIdent(Ident);
1439 impl MacroRulesNormalizedIdent {
1440 pub fn new(ident: Ident) -> Self {
1441 Self(ident.normalize_to_macro_rules())
1445 impl fmt::Debug for MacroRulesNormalizedIdent {
1446 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1447 fmt::Debug::fmt(&self.0, f)
1451 impl fmt::Display for MacroRulesNormalizedIdent {
1452 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1453 fmt::Display::fmt(&self.0, f)
1457 /// An interned string.
1459 /// Internally, a `Symbol` is implemented as an index, and all operations
1460 /// (including hashing, equality, and ordering) operate on that index. The use
1461 /// of `rustc_index::newtype_index!` means that `Option<Symbol>` only takes up 4 bytes,
1462 /// because `rustc_index::newtype_index!` reserves the last 256 values for tagging purposes.
1464 /// Note that `Symbol` cannot directly be a `rustc_index::newtype_index!` because it
1465 /// implements `fmt::Debug`, `Encodable`, and `Decodable` in special ways.
1466 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
1467 pub struct Symbol(SymbolIndex);
1469 rustc_index::newtype_index! {
1470 pub struct SymbolIndex { .. }
1474 const fn new(n: u32) -> Self {
1475 Symbol(SymbolIndex::from_u32(n))
1478 /// Maps a string to its interned representation.
1479 pub fn intern(string: &str) -> Self {
1480 with_interner(|interner| interner.intern(string))
1483 /// Convert to a `SymbolStr`. This is a slowish operation because it
1484 /// requires locking the symbol interner.
1485 pub fn as_str(self) -> SymbolStr {
1486 with_interner(|interner| unsafe {
1487 SymbolStr { string: std::mem::transmute::<&str, &str>(interner.get(self)) }
1491 pub fn as_u32(self) -> u32 {
1495 pub fn is_empty(self) -> bool {
1499 /// This method is supposed to be used in error messages, so it's expected to be
1500 /// identical to printing the original identifier token written in source code
1501 /// (`token_to_string`, `Ident::to_string`), except that symbols don't keep the rawness flag
1502 /// or edition, so we have to guess the rawness using the global edition.
1503 pub fn to_ident_string(self) -> String {
1504 Ident::with_dummy_span(self).to_string()
1508 impl fmt::Debug for Symbol {
1509 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1510 fmt::Debug::fmt(&self.as_str(), f)
1514 impl fmt::Display for Symbol {
1515 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1516 fmt::Display::fmt(&self.as_str(), f)
1520 impl<S: Encoder> Encodable<S> for Symbol {
1521 fn encode(&self, s: &mut S) -> Result<(), S::Error> {
1522 s.emit_str(&self.as_str())
1526 impl<D: Decoder> Decodable<D> for Symbol {
1528 fn decode(d: &mut D) -> Result<Symbol, D::Error> {
1529 Ok(Symbol::intern(&d.read_str()?))
1533 impl<CTX> HashStable<CTX> for Symbol {
1535 fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
1536 self.as_str().hash_stable(hcx, hasher);
1540 impl<CTX> ToStableHashKey<CTX> for Symbol {
1541 type KeyType = SymbolStr;
1544 fn to_stable_hash_key(&self, _: &CTX) -> SymbolStr {
1549 // The `&'static str`s in this type actually point into the arena.
1551 // The `FxHashMap`+`Vec` pair could be replaced by `FxIndexSet`, but #75278
1552 // found that to regress performance up to 2% in some cases. This might be
1553 // revisited after further improvements to `indexmap`.
1555 pub struct Interner {
1556 arena: DroplessArena,
1557 names: FxHashMap<&'static str, Symbol>,
1558 strings: Vec<&'static str>,
1562 fn prefill(init: &[&'static str]) -> Self {
1564 strings: init.into(),
1565 names: init.iter().copied().zip((0..).map(Symbol::new)).collect(),
1566 ..Default::default()
1571 pub fn intern(&mut self, string: &str) -> Symbol {
1572 if let Some(&name) = self.names.get(string) {
1576 let name = Symbol::new(self.strings.len() as u32);
1578 // `from_utf8_unchecked` is safe since we just allocated a `&str` which is known to be
1581 unsafe { str::from_utf8_unchecked(self.arena.alloc_slice(string.as_bytes())) };
1582 // It is safe to extend the arena allocation to `'static` because we only access
1583 // these while the arena is still alive.
1584 let string: &'static str = unsafe { &*(string as *const str) };
1585 self.strings.push(string);
1586 self.names.insert(string, name);
1590 // Get the symbol as a string. `Symbol::as_str()` should be used in
1591 // preference to this function.
1592 pub fn get(&self, symbol: Symbol) -> &str {
1593 self.strings[symbol.0.as_usize()]
1597 // This module has a very short name because it's used a lot.
1598 /// This module contains all the defined keyword `Symbol`s.
1600 /// Given that `kw` is imported, use them like `kw::keyword_name`.
1601 /// For example `kw::Loop` or `kw::Break`.
1603 pub use super::kw_generated::*;
1606 // This module has a very short name because it's used a lot.
1607 /// This module contains all the defined non-keyword `Symbol`s.
1609 /// Given that `sym` is imported, use them like `sym::symbol_name`.
1610 /// For example `sym::rustfmt` or `sym::u8`.
1613 use std::convert::TryInto;
1616 pub use super::sym_generated::*;
1618 // Used from a macro in `librustc_feature/accepted.rs`
1619 pub use super::kw::MacroRules as macro_rules;
1621 /// Get the symbol for an integer.
1623 /// The first few non-negative integers each have a static symbol and therefore
1625 pub fn integer<N: TryInto<usize> + Copy + ToString>(n: N) -> Symbol {
1626 if let Result::Ok(idx) = n.try_into() {
1628 return Symbol::new(super::SYMBOL_DIGITS_BASE + idx as u32);
1631 Symbol::intern(&n.to_string())
1636 fn is_special(self) -> bool {
1637 self <= kw::Underscore
1640 fn is_used_keyword_always(self) -> bool {
1641 self >= kw::As && self <= kw::While
1644 fn is_used_keyword_conditional(self, edition: impl FnOnce() -> Edition) -> bool {
1645 (self >= kw::Async && self <= kw::Dyn) && edition() >= Edition::Edition2018
1648 fn is_unused_keyword_always(self) -> bool {
1649 self >= kw::Abstract && self <= kw::Yield
1652 fn is_unused_keyword_conditional(self, edition: impl FnOnce() -> Edition) -> bool {
1653 self == kw::Try && edition() >= Edition::Edition2018
1656 pub fn is_reserved(self, edition: impl Copy + FnOnce() -> Edition) -> bool {
1658 || self.is_used_keyword_always()
1659 || self.is_unused_keyword_always()
1660 || self.is_used_keyword_conditional(edition)
1661 || self.is_unused_keyword_conditional(edition)
1664 /// A keyword or reserved identifier that can be used as a path segment.
1665 pub fn is_path_segment_keyword(self) -> bool {
1667 || self == kw::SelfLower
1668 || self == kw::SelfUpper
1669 || self == kw::Crate
1670 || self == kw::PathRoot
1671 || self == kw::DollarCrate
1674 /// Returns `true` if the symbol is `true` or `false`.
1675 pub fn is_bool_lit(self) -> bool {
1676 self == kw::True || self == kw::False
1679 /// Returns `true` if this symbol can be a raw identifier.
1680 pub fn can_be_raw(self) -> bool {
1681 self != kw::Empty && self != kw::Underscore && !self.is_path_segment_keyword()
1686 // Returns `true` for reserved identifiers used internally for elided lifetimes,
1687 // unnamed method parameters, crate root module, error recovery etc.
1688 pub fn is_special(self) -> bool {
1689 self.name.is_special()
1692 /// Returns `true` if the token is a keyword used in the language.
1693 pub fn is_used_keyword(self) -> bool {
1694 // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
1695 self.name.is_used_keyword_always()
1696 || self.name.is_used_keyword_conditional(|| self.span.edition())
1699 /// Returns `true` if the token is a keyword reserved for possible future use.
1700 pub fn is_unused_keyword(self) -> bool {
1701 // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
1702 self.name.is_unused_keyword_always()
1703 || self.name.is_unused_keyword_conditional(|| self.span.edition())
1706 /// Returns `true` if the token is either a special identifier or a keyword.
1707 pub fn is_reserved(self) -> bool {
1708 // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
1709 self.name.is_reserved(|| self.span.edition())
1712 /// A keyword or reserved identifier that can be used as a path segment.
1713 pub fn is_path_segment_keyword(self) -> bool {
1714 self.name.is_path_segment_keyword()
1717 /// We see this identifier in a normal identifier position, like variable name or a type.
1718 /// How was it written originally? Did it use the raw form? Let's try to guess.
1719 pub fn is_raw_guess(self) -> bool {
1720 self.name.can_be_raw() && self.is_reserved()
1725 fn with_interner<T, F: FnOnce(&mut Interner) -> T>(f: F) -> T {
1726 SESSION_GLOBALS.with(|session_globals| f(&mut *session_globals.symbol_interner.lock()))
1729 /// An alternative to [`Symbol`], useful when the chars within the symbol need to
1730 /// be accessed. It deliberately has limited functionality and should only be
1731 /// used for temporary values.
1733 /// Because the interner outlives any thread which uses this type, we can
1734 /// safely treat `string` which points to interner data, as an immortal string,
1735 /// as long as this type never crosses between threads.
1737 // FIXME: ensure that the interner outlives any thread which uses `SymbolStr`,
1738 // by creating a new thread right after constructing the interner.
1739 #[derive(Clone, Eq, PartialOrd, Ord)]
1740 pub struct SymbolStr {
1741 string: &'static str,
1744 // This impl allows a `SymbolStr` to be directly equated with a `String` or
1746 impl<T: std::ops::Deref<Target = str>> std::cmp::PartialEq<T> for SymbolStr {
1747 fn eq(&self, other: &T) -> bool {
1748 self.string == other.deref()
1752 impl !Send for SymbolStr {}
1753 impl !Sync for SymbolStr {}
1755 /// This impl means that if `ss` is a `SymbolStr`:
1756 /// - `*ss` is a `str`;
1757 /// - `&*ss` is a `&str` (and `match &*ss { ... }` is a common pattern).
1758 /// - `&ss as &str` is a `&str`, which means that `&ss` can be passed to a
1759 /// function expecting a `&str`.
1760 impl std::ops::Deref for SymbolStr {
1763 fn deref(&self) -> &str {
1768 impl fmt::Debug for SymbolStr {
1769 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1770 fmt::Debug::fmt(self.string, f)
1774 impl fmt::Display for SymbolStr {
1775 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1776 fmt::Display::fmt(self.string, f)
1780 impl<CTX> HashStable<CTX> for SymbolStr {
1782 fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
1783 self.string.hash_stable(hcx, hasher)
1787 impl<CTX> ToStableHashKey<CTX> for SymbolStr {
1788 type KeyType = SymbolStr;
1791 fn to_stable_hash_key(&self, _: &CTX) -> SymbolStr {