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,
573 from_size_align_unchecked,
586 generic_associated_types,
593 half_open_range_patterns,
595 hexagon_target_feature,
597 homogeneous_aggregate,
614 if_while_or_patterns,
616 impl_header_lifetime_elision,
619 impl_trait_in_bindings,
625 inclusive_range_syntax,
628 infer_outlives_requirements,
629 infer_static_outlives_requirements,
641 irrefutable_let_patterns,
645 issue_5723_bootstrap,
646 issue_tracker_base_url,
658 lazy_normalization_consts,
670 link_llvm_intrinsics,
689 macro_at_most_once_rep,
690 macro_attributes_in_derive_output,
693 macro_lifetime_matcher,
694 macro_literal_matcher,
706 match_beginning_vert,
707 match_default_bindings,
734 movbe_target_feature,
783 nontrapping_dash_fptoint: "nontrapping-fptoint",
788 object_safe_for_dispatch,
791 omit_gdb_pretty_printer_section,
800 optin_builtin_traits,
809 overlapping_marker_traits,
819 panic_implementation,
849 post_dash_lto: "post-lto",
850 powerpc_target_feature,
855 pre_dash_lto: "pre-lto",
856 precise_pointer_size_matching,
860 prefetch_read_instruction,
862 prefetch_write_instruction,
867 proc_dash_macro: "proc-macro",
869 proc_macro_attribute,
875 proc_macro_internals,
877 proc_macro_non_items,
878 proc_macro_path_invoc,
891 quad_precision_float,
898 re_rebalance_coherence,
901 read_enum_variant_arg,
909 reexport_test_harness_main,
922 relaxed_struct_unsize,
938 riscv_target_feature,
951 rust_eh_catch_typeinfo,
953 rust_eh_register_frames,
954 rust_eh_unregister_frames,
958 rustc_allocator_nounwind,
959 rustc_allow_const_fn_unstable,
960 rustc_args_required_const,
963 rustc_capture_analysis,
966 rustc_const_unstable,
967 rustc_conversion_suggestion,
970 rustc_diagnostic_item,
971 rustc_diagnostic_macros,
974 rustc_dump_env_program_clauses,
975 rustc_dump_program_clauses,
976 rustc_dump_user_substs,
978 rustc_expected_cgu_reuse,
979 rustc_if_this_changed,
980 rustc_inherit_overflow_checks,
982 rustc_layout_scalar_valid_range_end,
983 rustc_layout_scalar_valid_range_start,
984 rustc_legacy_const_generics,
985 rustc_macro_transparency,
987 rustc_nonnull_optimization_guaranteed,
988 rustc_object_lifetime_default,
989 rustc_on_unimplemented,
992 rustc_partition_codegened,
993 rustc_partition_reused,
995 rustc_peek_definite_init,
996 rustc_peek_indirectly_mutable,
998 rustc_peek_maybe_init,
999 rustc_peek_maybe_uninit,
1000 rustc_polymorphize_error,
1002 rustc_proc_macro_decls,
1005 rustc_reservation_impl,
1007 rustc_specialization_trait,
1009 rustc_std_internal_symbol,
1013 rustc_then_this_would_need,
1014 rustc_unsafe_specialization_marker,
1017 rvalue_static_promotion,
1065 simd_reduce_add_ordered,
1066 simd_reduce_add_unordered,
1071 simd_reduce_max_nanless,
1073 simd_reduce_min_nanless,
1074 simd_reduce_mul_ordered,
1075 simd_reduce_mul_unordered,
1079 simd_saturating_add,
1080 simd_saturating_sub,
1083 simd_select_bitmask,
1109 sse4a_target_feature,
1121 std_panic_2015_macro,
1124 stmt_expr_attributes,
1125 stop_after_dataflow,
1130 struct_field_attributes,
1152 target_has_atomic_equal_alignment,
1153 target_has_atomic_load_store,
1155 target_pointer_width,
1156 target_target_vendor,
1157 target_thread_local,
1163 termination_trait_test,
1166 test_accepted_feature,
1168 test_removed_feature,
1195 type_alias_enum_variants,
1196 type_alias_impl_trait,
1207 unaligned_volatile_load,
1208 unaligned_volatile_store,
1217 underscore_const_names,
1219 underscore_lifetimes,
1222 universal_impl_trait,
1229 unrestricted_attribute_tokens,
1230 unsafe_block_in_unsafe_fn,
1232 unsafe_no_drop_flag,
1236 unsized_tuple_coercion,
1239 unused_qualifications,
1261 visible_private_types,
1263 volatile_copy_memory,
1264 volatile_copy_nonoverlapping_memory,
1266 volatile_set_memory,
1272 wasm_target_feature,
1287 #[derive(Copy, Clone, Eq, HashStable_Generic, Encodable, Decodable)]
1295 /// Constructs a new identifier from a symbol and a span.
1296 pub const fn new(name: Symbol, span: Span) -> Ident {
1297 Ident { name, span }
1300 /// Constructs a new identifier with a dummy span.
1302 pub const fn with_dummy_span(name: Symbol) -> Ident {
1303 Ident::new(name, DUMMY_SP)
1307 pub fn invalid() -> Ident {
1308 Ident::with_dummy_span(kw::Empty)
1311 /// Maps a string to an identifier with a dummy span.
1312 pub fn from_str(string: &str) -> Ident {
1313 Ident::with_dummy_span(Symbol::intern(string))
1316 /// Maps a string and a span to an identifier.
1317 pub fn from_str_and_span(string: &str, span: Span) -> Ident {
1318 Ident::new(Symbol::intern(string), span)
1321 /// Replaces `lo` and `hi` with those from `span`, but keep hygiene context.
1322 pub fn with_span_pos(self, span: Span) -> Ident {
1323 Ident::new(self.name, span.with_ctxt(self.span.ctxt()))
1326 pub fn without_first_quote(self) -> Ident {
1327 Ident::new(Symbol::intern(self.as_str().trim_start_matches('\'')), self.span)
1330 /// "Normalize" ident for use in comparisons using "item hygiene".
1331 /// Identifiers with same string value become same if they came from the same macro 2.0 macro
1332 /// (e.g., `macro` item, but not `macro_rules` item) and stay different if they came from
1333 /// different macro 2.0 macros.
1334 /// Technically, this operation strips all non-opaque marks from ident's syntactic context.
1335 pub fn normalize_to_macros_2_0(self) -> Ident {
1336 Ident::new(self.name, self.span.normalize_to_macros_2_0())
1339 /// "Normalize" ident for use in comparisons using "local variable hygiene".
1340 /// Identifiers with same string value become same if they came from the same non-transparent
1341 /// macro (e.g., `macro` or `macro_rules!` items) and stay different if they came from different
1342 /// non-transparent macros.
1343 /// Technically, this operation strips all transparent marks from ident's syntactic context.
1344 pub fn normalize_to_macro_rules(self) -> Ident {
1345 Ident::new(self.name, self.span.normalize_to_macro_rules())
1348 /// Convert the name to a `SymbolStr`. This is a slowish operation because
1349 /// it requires locking the symbol interner.
1350 pub fn as_str(self) -> SymbolStr {
1355 impl PartialEq for Ident {
1356 fn eq(&self, rhs: &Self) -> bool {
1357 self.name == rhs.name && self.span.ctxt() == rhs.span.ctxt()
1361 impl Hash for Ident {
1362 fn hash<H: Hasher>(&self, state: &mut H) {
1363 self.name.hash(state);
1364 self.span.ctxt().hash(state);
1368 impl fmt::Debug for Ident {
1369 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1370 fmt::Display::fmt(self, f)?;
1371 fmt::Debug::fmt(&self.span.ctxt(), f)
1375 /// This implementation is supposed to be used in error messages, so it's expected to be identical
1376 /// to printing the original identifier token written in source code (`token_to_string`),
1377 /// except that AST identifiers don't keep the rawness flag, so we have to guess it.
1378 impl fmt::Display for Ident {
1379 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1380 fmt::Display::fmt(&IdentPrinter::new(self.name, self.is_raw_guess(), None), f)
1384 /// This is the most general way to print identifiers.
1385 /// AST pretty-printer is used as a fallback for turning AST structures into token streams for
1386 /// proc macros. Additionally, proc macros may stringify their input and expect it survive the
1387 /// stringification (especially true for proc macro derives written between Rust 1.15 and 1.30).
1388 /// So we need to somehow pretty-print `$crate` in a way preserving at least some of its
1389 /// hygiene data, most importantly name of the crate it refers to.
1390 /// As a result we print `$crate` as `crate` if it refers to the local crate
1391 /// and as `::other_crate_name` if it refers to some other crate.
1392 /// Note, that this is only done if the ident token is printed from inside of AST pretty-pringing,
1393 /// but not otherwise. Pretty-printing is the only way for proc macros to discover token contents,
1394 /// so we should not perform this lossy conversion if the top level call to the pretty-printer was
1395 /// done for a token stream or a single token.
1396 pub struct IdentPrinter {
1399 /// Span used for retrieving the crate name to which `$crate` refers to,
1400 /// if this field is `None` then the `$crate` conversion doesn't happen.
1401 convert_dollar_crate: Option<Span>,
1405 /// The most general `IdentPrinter` constructor. Do not use this.
1406 pub fn new(symbol: Symbol, is_raw: bool, convert_dollar_crate: Option<Span>) -> IdentPrinter {
1407 IdentPrinter { symbol, is_raw, convert_dollar_crate }
1410 /// This implementation is supposed to be used when printing identifiers
1411 /// as a part of pretty-printing for larger AST pieces.
1412 /// Do not use this either.
1413 pub fn for_ast_ident(ident: Ident, is_raw: bool) -> IdentPrinter {
1414 IdentPrinter::new(ident.name, is_raw, Some(ident.span))
1418 impl fmt::Display for IdentPrinter {
1419 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1422 } else if self.symbol == kw::DollarCrate {
1423 if let Some(span) = self.convert_dollar_crate {
1424 let converted = span.ctxt().dollar_crate_name();
1425 if !converted.is_path_segment_keyword() {
1428 return fmt::Display::fmt(&converted, f);
1431 fmt::Display::fmt(&self.symbol, f)
1435 /// An newtype around `Ident` that calls [Ident::normalize_to_macro_rules] on
1437 // FIXME(matthewj, petrochenkov) Use this more often, add a similar
1438 // `ModernIdent` struct and use that as well.
1439 #[derive(Copy, Clone, Eq, PartialEq, Hash)]
1440 pub struct MacroRulesNormalizedIdent(Ident);
1442 impl MacroRulesNormalizedIdent {
1443 pub fn new(ident: Ident) -> Self {
1444 Self(ident.normalize_to_macro_rules())
1448 impl fmt::Debug for MacroRulesNormalizedIdent {
1449 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1450 fmt::Debug::fmt(&self.0, f)
1454 impl fmt::Display for MacroRulesNormalizedIdent {
1455 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1456 fmt::Display::fmt(&self.0, f)
1460 /// An interned string.
1462 /// Internally, a `Symbol` is implemented as an index, and all operations
1463 /// (including hashing, equality, and ordering) operate on that index. The use
1464 /// of `rustc_index::newtype_index!` means that `Option<Symbol>` only takes up 4 bytes,
1465 /// because `rustc_index::newtype_index!` reserves the last 256 values for tagging purposes.
1467 /// Note that `Symbol` cannot directly be a `rustc_index::newtype_index!` because it
1468 /// implements `fmt::Debug`, `Encodable`, and `Decodable` in special ways.
1469 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
1470 pub struct Symbol(SymbolIndex);
1472 rustc_index::newtype_index! {
1473 pub struct SymbolIndex { .. }
1477 const fn new(n: u32) -> Self {
1478 Symbol(SymbolIndex::from_u32(n))
1481 /// Maps a string to its interned representation.
1482 pub fn intern(string: &str) -> Self {
1483 with_interner(|interner| interner.intern(string))
1486 /// Convert to a `SymbolStr`. This is a slowish operation because it
1487 /// requires locking the symbol interner.
1488 pub fn as_str(self) -> SymbolStr {
1489 with_interner(|interner| unsafe {
1490 SymbolStr { string: std::mem::transmute::<&str, &str>(interner.get(self)) }
1494 pub fn as_u32(self) -> u32 {
1498 pub fn is_empty(self) -> bool {
1502 /// This method is supposed to be used in error messages, so it's expected to be
1503 /// identical to printing the original identifier token written in source code
1504 /// (`token_to_string`, `Ident::to_string`), except that symbols don't keep the rawness flag
1505 /// or edition, so we have to guess the rawness using the global edition.
1506 pub fn to_ident_string(self) -> String {
1507 Ident::with_dummy_span(self).to_string()
1511 impl fmt::Debug for Symbol {
1512 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1513 fmt::Debug::fmt(&self.as_str(), f)
1517 impl fmt::Display for Symbol {
1518 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1519 fmt::Display::fmt(&self.as_str(), f)
1523 impl<S: Encoder> Encodable<S> for Symbol {
1524 fn encode(&self, s: &mut S) -> Result<(), S::Error> {
1525 s.emit_str(&self.as_str())
1529 impl<D: Decoder> Decodable<D> for Symbol {
1531 fn decode(d: &mut D) -> Result<Symbol, D::Error> {
1532 Ok(Symbol::intern(&d.read_str()?))
1536 impl<CTX> HashStable<CTX> for Symbol {
1538 fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
1539 self.as_str().hash_stable(hcx, hasher);
1543 impl<CTX> ToStableHashKey<CTX> for Symbol {
1544 type KeyType = SymbolStr;
1547 fn to_stable_hash_key(&self, _: &CTX) -> SymbolStr {
1552 // The `&'static str`s in this type actually point into the arena.
1554 // The `FxHashMap`+`Vec` pair could be replaced by `FxIndexSet`, but #75278
1555 // found that to regress performance up to 2% in some cases. This might be
1556 // revisited after further improvements to `indexmap`.
1558 pub struct Interner {
1559 arena: DroplessArena,
1560 names: FxHashMap<&'static str, Symbol>,
1561 strings: Vec<&'static str>,
1565 fn prefill(init: &[&'static str]) -> Self {
1567 strings: init.into(),
1568 names: init.iter().copied().zip((0..).map(Symbol::new)).collect(),
1569 ..Default::default()
1574 pub fn intern(&mut self, string: &str) -> Symbol {
1575 if let Some(&name) = self.names.get(string) {
1579 let name = Symbol::new(self.strings.len() as u32);
1581 // `from_utf8_unchecked` is safe since we just allocated a `&str` which is known to be
1584 unsafe { str::from_utf8_unchecked(self.arena.alloc_slice(string.as_bytes())) };
1585 // It is safe to extend the arena allocation to `'static` because we only access
1586 // these while the arena is still alive.
1587 let string: &'static str = unsafe { &*(string as *const str) };
1588 self.strings.push(string);
1589 self.names.insert(string, name);
1593 // Get the symbol as a string. `Symbol::as_str()` should be used in
1594 // preference to this function.
1595 pub fn get(&self, symbol: Symbol) -> &str {
1596 self.strings[symbol.0.as_usize()]
1600 // This module has a very short name because it's used a lot.
1601 /// This module contains all the defined keyword `Symbol`s.
1603 /// Given that `kw` is imported, use them like `kw::keyword_name`.
1604 /// For example `kw::Loop` or `kw::Break`.
1606 pub use super::kw_generated::*;
1609 // This module has a very short name because it's used a lot.
1610 /// This module contains all the defined non-keyword `Symbol`s.
1612 /// Given that `sym` is imported, use them like `sym::symbol_name`.
1613 /// For example `sym::rustfmt` or `sym::u8`.
1616 use std::convert::TryInto;
1619 pub use super::sym_generated::*;
1621 // Used from a macro in `librustc_feature/accepted.rs`
1622 pub use super::kw::MacroRules as macro_rules;
1624 /// Get the symbol for an integer.
1626 /// The first few non-negative integers each have a static symbol and therefore
1628 pub fn integer<N: TryInto<usize> + Copy + ToString>(n: N) -> Symbol {
1629 if let Result::Ok(idx) = n.try_into() {
1631 return Symbol::new(super::SYMBOL_DIGITS_BASE + idx as u32);
1634 Symbol::intern(&n.to_string())
1639 fn is_special(self) -> bool {
1640 self <= kw::Underscore
1643 fn is_used_keyword_always(self) -> bool {
1644 self >= kw::As && self <= kw::While
1647 fn is_used_keyword_conditional(self, edition: impl FnOnce() -> Edition) -> bool {
1648 (self >= kw::Async && self <= kw::Dyn) && edition() >= Edition::Edition2018
1651 fn is_unused_keyword_always(self) -> bool {
1652 self >= kw::Abstract && self <= kw::Yield
1655 fn is_unused_keyword_conditional(self, edition: impl FnOnce() -> Edition) -> bool {
1656 self == kw::Try && edition() >= Edition::Edition2018
1659 pub fn is_reserved(self, edition: impl Copy + FnOnce() -> Edition) -> bool {
1661 || self.is_used_keyword_always()
1662 || self.is_unused_keyword_always()
1663 || self.is_used_keyword_conditional(edition)
1664 || self.is_unused_keyword_conditional(edition)
1667 /// A keyword or reserved identifier that can be used as a path segment.
1668 pub fn is_path_segment_keyword(self) -> bool {
1670 || self == kw::SelfLower
1671 || self == kw::SelfUpper
1672 || self == kw::Crate
1673 || self == kw::PathRoot
1674 || self == kw::DollarCrate
1677 /// Returns `true` if the symbol is `true` or `false`.
1678 pub fn is_bool_lit(self) -> bool {
1679 self == kw::True || self == kw::False
1682 /// Returns `true` if this symbol can be a raw identifier.
1683 pub fn can_be_raw(self) -> bool {
1684 self != kw::Empty && self != kw::Underscore && !self.is_path_segment_keyword()
1689 // Returns `true` for reserved identifiers used internally for elided lifetimes,
1690 // unnamed method parameters, crate root module, error recovery etc.
1691 pub fn is_special(self) -> bool {
1692 self.name.is_special()
1695 /// Returns `true` if the token is a keyword used in the language.
1696 pub fn is_used_keyword(self) -> bool {
1697 // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
1698 self.name.is_used_keyword_always()
1699 || self.name.is_used_keyword_conditional(|| self.span.edition())
1702 /// Returns `true` if the token is a keyword reserved for possible future use.
1703 pub fn is_unused_keyword(self) -> bool {
1704 // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
1705 self.name.is_unused_keyword_always()
1706 || self.name.is_unused_keyword_conditional(|| self.span.edition())
1709 /// Returns `true` if the token is either a special identifier or a keyword.
1710 pub fn is_reserved(self) -> bool {
1711 // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
1712 self.name.is_reserved(|| self.span.edition())
1715 /// A keyword or reserved identifier that can be used as a path segment.
1716 pub fn is_path_segment_keyword(self) -> bool {
1717 self.name.is_path_segment_keyword()
1720 /// We see this identifier in a normal identifier position, like variable name or a type.
1721 /// How was it written originally? Did it use the raw form? Let's try to guess.
1722 pub fn is_raw_guess(self) -> bool {
1723 self.name.can_be_raw() && self.is_reserved()
1728 fn with_interner<T, F: FnOnce(&mut Interner) -> T>(f: F) -> T {
1729 SESSION_GLOBALS.with(|session_globals| f(&mut *session_globals.symbol_interner.lock()))
1732 /// An alternative to [`Symbol`], useful when the chars within the symbol need to
1733 /// be accessed. It deliberately has limited functionality and should only be
1734 /// used for temporary values.
1736 /// Because the interner outlives any thread which uses this type, we can
1737 /// safely treat `string` which points to interner data, as an immortal string,
1738 /// as long as this type never crosses between threads.
1740 // FIXME: ensure that the interner outlives any thread which uses `SymbolStr`,
1741 // by creating a new thread right after constructing the interner.
1742 #[derive(Clone, Eq, PartialOrd, Ord)]
1743 pub struct SymbolStr {
1744 string: &'static str,
1747 // This impl allows a `SymbolStr` to be directly equated with a `String` or
1749 impl<T: std::ops::Deref<Target = str>> std::cmp::PartialEq<T> for SymbolStr {
1750 fn eq(&self, other: &T) -> bool {
1751 self.string == other.deref()
1755 impl !Send for SymbolStr {}
1756 impl !Sync for SymbolStr {}
1758 /// This impl means that if `ss` is a `SymbolStr`:
1759 /// - `*ss` is a `str`;
1760 /// - `&*ss` is a `&str` (and `match &*ss { ... }` is a common pattern).
1761 /// - `&ss as &str` is a `&str`, which means that `&ss` can be passed to a
1762 /// function expecting a `&str`.
1763 impl std::ops::Deref for SymbolStr {
1766 fn deref(&self) -> &str {
1771 impl fmt::Debug for SymbolStr {
1772 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1773 fmt::Debug::fmt(self.string, f)
1777 impl fmt::Display for SymbolStr {
1778 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1779 fmt::Display::fmt(self.string, f)
1783 impl<CTX> HashStable<CTX> for SymbolStr {
1785 fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
1786 self.string.hash_stable(hcx, hasher)
1790 impl<CTX> ToStableHashKey<CTX> for SymbolStr {
1791 type KeyType = SymbolStr;
1794 fn to_stable_hash_key(&self, _: &CTX) -> SymbolStr {