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::{symbols, HashStable_Generic};
9 use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
10 use rustc_serialize::{UseSpecializedDecodable, UseSpecializedEncodable};
12 use std::cmp::{Ord, PartialEq, PartialOrd};
14 use std::hash::{Hash, Hasher};
17 use crate::{Span, DUMMY_SP, SESSION_GLOBALS};
22 // The proc macro code for this is in `src/librustc_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 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
179 ProceduralMasqueradeDummyType,
216 aarch64_target_feature,
221 abi_msp430_interrupt,
234 advanced_slice_patterns,
249 allow_internal_unsafe,
250 allow_internal_unstable,
251 allow_internal_unstable_backcompat_hack,
257 arbitrary_enum_discriminant,
258 arbitrary_self_types,
266 assert_receiver_is_total_eq,
270 associated_type_bounds,
271 associated_type_defaults,
282 augmented_assignments,
283 automatically_derived,
284 avx512_target_feature,
290 bind_by_move_pattern_guards,
301 borrowck_graphviz_format,
302 borrowck_graphviz_postflow,
303 borrowck_graphviz_preflow,
307 braced_empty_structs,
326 cfg_target_has_atomic,
327 cfg_target_thread_local,
336 closure_to_fn_coercion,
338 cmpxchg16b_target_feature,
346 conservative_impl_trait,
348 const_compare_raw_pointers,
357 const_in_array_repeat_expressions,
363 const_precise_live_drops,
366 const_raw_ptr_to_usize_cast,
368 const_trait_bound_opt_out,
384 coverage_counter_add,
385 coverage_counter_subtract,
386 coverage_unreachable,
392 crate_visibility_modifier,
393 crt_dash_static: "crt-static",
401 custom_inner_attributes,
402 custom_test_frameworks,
415 default_lib_allocator,
416 default_type_parameter_fallback,
418 delay_span_bug_from_inside_query,
439 document_private_items,
440 dotdot_in_tuple_patterns,
441 dotdoteq_in_patterns,
442 double_braced_closure: "{{closure}}",
443 double_braced_constant: "{{constant}}",
444 double_braced_constructor: "{{constructor}}",
445 double_braced_crate: "{{crate}}",
446 double_braced_impl: "{{impl}}",
447 double_braced_misc: "{{misc}}",
448 double_braced_opaque: "{{opaque}}",
453 dropck_parametricity,
460 emit_enum_variant_arg,
472 exclusive_range_pattern,
473 exhaustive_integer_patterns,
483 extern_absolute_paths,
484 extern_crate_item_prelude,
505 field_init_shorthand,
510 float_to_int_unchecked,
536 from_size_align_unchecked,
549 generic_associated_types,
556 half_open_range_patterns,
558 hexagon_target_feature,
560 homogeneous_aggregate,
575 if_while_or_patterns,
577 impl_header_lifetime_elision,
579 impl_trait_in_bindings,
585 inclusive_range_syntax,
588 infer_outlives_requirements,
589 infer_static_outlives_requirements,
597 irrefutable_let_patterns,
600 issue_5723_bootstrap,
601 issue_tracker_base_url,
612 lazy_normalization_consts,
624 link_llvm_intrinsics,
642 macro_at_most_once_rep,
645 macro_lifetime_matcher,
646 macro_literal_matcher,
658 match_beginning_vert,
659 match_default_bindings,
685 movbe_target_feature,
734 nontrapping_dash_fptoint: "nontrapping-fptoint",
739 object_safe_for_dispatch,
742 omit_gdb_pretty_printer_section,
751 optin_builtin_traits,
760 overlapping_marker_traits,
768 panic_implementation,
791 post_dash_lto: "post-lto",
792 powerpc_target_feature,
797 pre_dash_lto: "pre-lto",
798 precise_pointer_size_matching,
802 prefetch_read_instruction,
804 prefetch_write_instruction,
809 proc_dash_macro: "proc-macro",
811 proc_macro_attribute,
817 proc_macro_internals,
819 proc_macro_non_items,
820 proc_macro_path_invoc,
829 quad_precision_float,
835 re_rebalance_coherence,
838 read_enum_variant_arg,
846 reexport_test_harness_main,
867 riscv_target_feature,
880 rust_eh_register_frames,
881 rust_eh_unregister_frames,
885 rustc_allocator_nounwind,
886 rustc_allow_const_fn_ptr,
887 rustc_args_required_const,
892 rustc_const_unstable,
893 rustc_conversion_suggestion,
896 rustc_diagnostic_item,
897 rustc_diagnostic_macros,
900 rustc_dump_env_program_clauses,
901 rustc_dump_program_clauses,
902 rustc_dump_user_substs,
904 rustc_expected_cgu_reuse,
905 rustc_if_this_changed,
906 rustc_inherit_overflow_checks,
908 rustc_layout_scalar_valid_range_end,
909 rustc_layout_scalar_valid_range_start,
910 rustc_macro_transparency,
912 rustc_nonnull_optimization_guaranteed,
913 rustc_object_lifetime_default,
914 rustc_on_unimplemented,
917 rustc_partition_codegened,
918 rustc_partition_reused,
920 rustc_peek_definite_init,
921 rustc_peek_indirectly_mutable,
923 rustc_peek_maybe_init,
924 rustc_peek_maybe_uninit,
925 rustc_polymorphize_error,
927 rustc_proc_macro_decls,
930 rustc_reservation_impl,
932 rustc_specialization_trait,
934 rustc_std_internal_symbol,
938 rustc_then_this_would_need,
939 rustc_unsafe_specialization_marker,
942 rvalue_static_promotion,
990 simd_reduce_add_ordered,
991 simd_reduce_add_unordered,
996 simd_reduce_max_nanless,
998 simd_reduce_min_nanless,
999 simd_reduce_mul_ordered,
1000 simd_reduce_mul_unordered,
1004 simd_saturating_add,
1005 simd_saturating_sub,
1008 simd_select_bitmask,
1032 sse4a_target_feature,
1044 stmt_expr_attributes,
1045 stop_after_dataflow,
1050 struct_field_attributes,
1071 target_has_atomic_load_store,
1073 target_pointer_width,
1074 target_target_vendor,
1075 target_thread_local,
1081 termination_trait_test,
1084 test_accepted_feature,
1086 test_removed_feature,
1110 type_alias_enum_variants,
1111 type_alias_impl_trait,
1122 unaligned_volatile_load,
1123 unaligned_volatile_store,
1132 underscore_const_names,
1134 underscore_lifetimes,
1137 universal_impl_trait,
1144 unrestricted_attribute_tokens,
1145 unsafe_block_in_unsafe_fn,
1147 unsafe_no_drop_flag,
1150 unsized_tuple_coercion,
1153 unused_qualifications,
1174 visible_private_types,
1176 volatile_copy_memory,
1177 volatile_copy_nonoverlapping_memory,
1179 volatile_set_memory,
1183 wasm_target_feature,
1195 #[derive(Copy, Clone, Eq, HashStable_Generic)]
1203 /// Constructs a new identifier from a symbol and a span.
1204 pub const fn new(name: Symbol, span: Span) -> Ident {
1205 Ident { name, span }
1208 /// Constructs a new identifier with a dummy span.
1210 pub const fn with_dummy_span(name: Symbol) -> Ident {
1211 Ident::new(name, DUMMY_SP)
1215 pub fn invalid() -> Ident {
1216 Ident::with_dummy_span(kw::Invalid)
1219 /// Maps a string to an identifier with a dummy span.
1220 pub fn from_str(string: &str) -> Ident {
1221 Ident::with_dummy_span(Symbol::intern(string))
1224 /// Maps a string and a span to an identifier.
1225 pub fn from_str_and_span(string: &str, span: Span) -> Ident {
1226 Ident::new(Symbol::intern(string), span)
1229 /// Replaces `lo` and `hi` with those from `span`, but keep hygiene context.
1230 pub fn with_span_pos(self, span: Span) -> Ident {
1231 Ident::new(self.name, span.with_ctxt(self.span.ctxt()))
1234 pub fn without_first_quote(self) -> Ident {
1235 Ident::new(Symbol::intern(self.as_str().trim_start_matches('\'')), self.span)
1238 /// "Normalize" ident for use in comparisons using "item hygiene".
1239 /// Identifiers with same string value become same if they came from the same macro 2.0 macro
1240 /// (e.g., `macro` item, but not `macro_rules` item) and stay different if they came from
1241 /// different macro 2.0 macros.
1242 /// Technically, this operation strips all non-opaque marks from ident's syntactic context.
1243 pub fn normalize_to_macros_2_0(self) -> Ident {
1244 Ident::new(self.name, self.span.normalize_to_macros_2_0())
1247 /// "Normalize" ident for use in comparisons using "local variable hygiene".
1248 /// Identifiers with same string value become same if they came from the same non-transparent
1249 /// macro (e.g., `macro` or `macro_rules!` items) and stay different if they came from different
1250 /// non-transparent macros.
1251 /// Technically, this operation strips all transparent marks from ident's syntactic context.
1252 pub fn normalize_to_macro_rules(self) -> Ident {
1253 Ident::new(self.name, self.span.normalize_to_macro_rules())
1256 /// Convert the name to a `SymbolStr`. This is a slowish operation because
1257 /// it requires locking the symbol interner.
1258 pub fn as_str(self) -> SymbolStr {
1263 impl PartialEq for Ident {
1264 fn eq(&self, rhs: &Self) -> bool {
1265 self.name == rhs.name && self.span.ctxt() == rhs.span.ctxt()
1269 impl Hash for Ident {
1270 fn hash<H: Hasher>(&self, state: &mut H) {
1271 self.name.hash(state);
1272 self.span.ctxt().hash(state);
1276 impl fmt::Debug for Ident {
1277 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1278 fmt::Display::fmt(self, f)?;
1279 fmt::Debug::fmt(&self.span.ctxt(), f)
1283 /// This implementation is supposed to be used in error messages, so it's expected to be identical
1284 /// to printing the original identifier token written in source code (`token_to_string`),
1285 /// except that AST identifiers don't keep the rawness flag, so we have to guess it.
1286 impl fmt::Display for Ident {
1287 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1288 fmt::Display::fmt(&IdentPrinter::new(self.name, self.is_raw_guess(), None), f)
1292 impl UseSpecializedEncodable for Ident {
1293 fn default_encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
1294 s.emit_struct("Ident", 2, |s| {
1295 s.emit_struct_field("name", 0, |s| self.name.encode(s))?;
1296 s.emit_struct_field("span", 1, |s| self.span.encode(s))
1301 impl UseSpecializedDecodable for Ident {
1302 fn default_decode<D: Decoder>(d: &mut D) -> Result<Self, D::Error> {
1303 d.read_struct("Ident", 2, |d| {
1305 name: d.read_struct_field("name", 0, Decodable::decode)?,
1306 span: d.read_struct_field("span", 1, Decodable::decode)?,
1312 /// This is the most general way to print identifiers.
1313 /// AST pretty-printer is used as a fallback for turning AST structures into token streams for
1314 /// proc macros. Additionally, proc macros may stringify their input and expect it survive the
1315 /// stringification (especially true for proc macro derives written between Rust 1.15 and 1.30).
1316 /// So we need to somehow pretty-print `$crate` in a way preserving at least some of its
1317 /// hygiene data, most importantly name of the crate it refers to.
1318 /// As a result we print `$crate` as `crate` if it refers to the local crate
1319 /// and as `::other_crate_name` if it refers to some other crate.
1320 /// Note, that this is only done if the ident token is printed from inside of AST pretty-pringing,
1321 /// but not otherwise. Pretty-printing is the only way for proc macros to discover token contents,
1322 /// so we should not perform this lossy conversion if the top level call to the pretty-printer was
1323 /// done for a token stream or a single token.
1324 pub struct IdentPrinter {
1327 /// Span used for retrieving the crate name to which `$crate` refers to,
1328 /// if this field is `None` then the `$crate` conversion doesn't happen.
1329 convert_dollar_crate: Option<Span>,
1333 /// The most general `IdentPrinter` constructor. Do not use this.
1334 pub fn new(symbol: Symbol, is_raw: bool, convert_dollar_crate: Option<Span>) -> IdentPrinter {
1335 IdentPrinter { symbol, is_raw, convert_dollar_crate }
1338 /// This implementation is supposed to be used when printing identifiers
1339 /// as a part of pretty-printing for larger AST pieces.
1340 /// Do not use this either.
1341 pub fn for_ast_ident(ident: Ident, is_raw: bool) -> IdentPrinter {
1342 IdentPrinter::new(ident.name, is_raw, Some(ident.span))
1346 impl fmt::Display for IdentPrinter {
1347 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1351 if self.symbol == kw::DollarCrate {
1352 if let Some(span) = self.convert_dollar_crate {
1353 let converted = span.ctxt().dollar_crate_name();
1354 if !converted.is_path_segment_keyword() {
1357 return fmt::Display::fmt(&converted, f);
1361 fmt::Display::fmt(&self.symbol, f)
1365 /// An newtype around `Ident` that calls [Ident::normalize_to_macro_rules] on
1367 // FIXME(matthewj, petrochenkov) Use this more often, add a similar
1368 // `ModernIdent` struct and use that as well.
1369 #[derive(Copy, Clone, Eq, PartialEq, Hash)]
1370 pub struct MacroRulesNormalizedIdent(Ident);
1372 impl MacroRulesNormalizedIdent {
1373 pub fn new(ident: Ident) -> Self {
1374 Self(ident.normalize_to_macro_rules())
1378 impl fmt::Debug for MacroRulesNormalizedIdent {
1379 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1380 fmt::Debug::fmt(&self.0, f)
1384 impl fmt::Display for MacroRulesNormalizedIdent {
1385 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1386 fmt::Display::fmt(&self.0, f)
1390 /// An interned string.
1392 /// Internally, a `Symbol` is implemented as an index, and all operations
1393 /// (including hashing, equality, and ordering) operate on that index. The use
1394 /// of `rustc_index::newtype_index!` means that `Option<Symbol>` only takes up 4 bytes,
1395 /// because `rustc_index::newtype_index!` reserves the last 256 values for tagging purposes.
1397 /// Note that `Symbol` cannot directly be a `rustc_index::newtype_index!` because it
1398 /// implements `fmt::Debug`, `Encodable`, and `Decodable` in special ways.
1399 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
1400 pub struct Symbol(SymbolIndex);
1402 rustc_index::newtype_index! {
1403 pub struct SymbolIndex { .. }
1407 const fn new(n: u32) -> Self {
1408 Symbol(SymbolIndex::from_u32(n))
1411 /// Maps a string to its interned representation.
1412 pub fn intern(string: &str) -> Self {
1413 with_interner(|interner| interner.intern(string))
1416 /// Access the symbol's chars. This is a slowish operation because it
1417 /// requires locking the symbol interner.
1418 pub fn with<F: FnOnce(&str) -> R, R>(self, f: F) -> R {
1419 with_interner(|interner| f(interner.get(self)))
1422 /// Convert to a `SymbolStr`. This is a slowish operation because it
1423 /// requires locking the symbol interner.
1424 pub fn as_str(self) -> SymbolStr {
1425 with_interner(|interner| unsafe {
1426 SymbolStr { string: std::mem::transmute::<&str, &str>(interner.get(self)) }
1430 pub fn as_u32(self) -> u32 {
1434 /// This method is supposed to be used in error messages, so it's expected to be
1435 /// identical to printing the original identifier token written in source code
1436 /// (`token_to_string`, `Ident::to_string`), except that symbols don't keep the rawness flag
1437 /// or edition, so we have to guess the rawness using the global edition.
1438 pub fn to_ident_string(self) -> String {
1439 Ident::with_dummy_span(self).to_string()
1443 impl fmt::Debug for Symbol {
1444 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1445 self.with(|str| fmt::Debug::fmt(&str, f))
1449 impl fmt::Display for Symbol {
1450 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1451 self.with(|str| fmt::Display::fmt(&str, f))
1455 impl Encodable for Symbol {
1456 fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
1457 self.with(|string| s.emit_str(string))
1461 impl Decodable for Symbol {
1463 fn decode<D: Decoder>(d: &mut D) -> Result<Symbol, D::Error> {
1464 Ok(Symbol::intern(&d.read_str()?))
1468 impl<CTX> HashStable<CTX> for Symbol {
1470 fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
1471 self.as_str().hash_stable(hcx, hasher);
1475 impl<CTX> ToStableHashKey<CTX> for Symbol {
1476 type KeyType = SymbolStr;
1479 fn to_stable_hash_key(&self, _: &CTX) -> SymbolStr {
1484 // The `&'static str`s in this type actually point into the arena.
1486 // The `FxHashMap`+`Vec` pair could be replaced by `FxIndexSet`, but #75278
1487 // found that to regress performance up to 2% in some cases. This might be
1488 // revisited after further improvements to `indexmap`.
1490 pub struct Interner {
1491 arena: DroplessArena,
1492 names: FxHashMap<&'static str, Symbol>,
1493 strings: Vec<&'static str>,
1497 fn prefill(init: &[&'static str]) -> Self {
1499 strings: init.into(),
1500 names: init.iter().copied().zip((0..).map(Symbol::new)).collect(),
1501 ..Default::default()
1506 pub fn intern(&mut self, string: &str) -> Symbol {
1507 if let Some(&name) = self.names.get(string) {
1511 let name = Symbol::new(self.strings.len() as u32);
1513 // `from_utf8_unchecked` is safe since we just allocated a `&str` which is known to be
1516 unsafe { str::from_utf8_unchecked(self.arena.alloc_slice(string.as_bytes())) };
1517 // It is safe to extend the arena allocation to `'static` because we only access
1518 // these while the arena is still alive.
1519 let string: &'static str = unsafe { &*(string as *const str) };
1520 self.strings.push(string);
1521 self.names.insert(string, name);
1525 // Get the symbol as a string. `Symbol::as_str()` should be used in
1526 // preference to this function.
1527 pub fn get(&self, symbol: Symbol) -> &str {
1528 self.strings[symbol.0.as_usize()]
1532 // This module has a very short name because it's used a lot.
1533 /// This module contains all the defined keyword `Symbol`s.
1535 /// Given that `kw` is imported, use them like `kw::keyword_name`.
1536 /// For example `kw::Loop` or `kw::Break`.
1542 // This module has a very short name because it's used a lot.
1543 /// This module contains all the defined non-keyword `Symbol`s.
1545 /// Given that `sym` is imported, use them like `sym::symbol_name`.
1546 /// For example `sym::rustfmt` or `sym::u8`.
1547 #[allow(rustc::default_hash_types)]
1550 use std::convert::TryInto;
1554 // Used from a macro in `librustc_feature/accepted.rs`
1555 pub use super::kw::MacroRules as macro_rules;
1557 // Get the symbol for an integer. The first few non-negative integers each
1558 // have a static symbol and therefore are fast.
1559 pub fn integer<N: TryInto<usize> + Copy + ToString>(n: N) -> Symbol {
1560 if let Result::Ok(idx) = n.try_into() {
1561 if let Option::Some(&sym_) = digits_array.get(idx) {
1565 Symbol::intern(&n.to_string())
1570 fn is_used_keyword_2018(self) -> bool {
1571 self >= kw::Async && self <= kw::Dyn
1574 fn is_unused_keyword_2018(self) -> bool {
1578 /// Used for sanity checking rustdoc keyword sections.
1579 pub fn is_doc_keyword(self) -> bool {
1583 /// A keyword or reserved identifier that can be used as a path segment.
1584 pub fn is_path_segment_keyword(self) -> bool {
1586 || self == kw::SelfLower
1587 || self == kw::SelfUpper
1588 || self == kw::Crate
1589 || self == kw::PathRoot
1590 || self == kw::DollarCrate
1593 /// Returns `true` if the symbol is `true` or `false`.
1594 pub fn is_bool_lit(self) -> bool {
1595 self == kw::True || self == kw::False
1598 /// This symbol can be a raw identifier.
1599 pub fn can_be_raw(self) -> bool {
1600 self != kw::Invalid && self != kw::Underscore && !self.is_path_segment_keyword()
1605 // Returns `true` for reserved identifiers used internally for elided lifetimes,
1606 // unnamed method parameters, crate root module, error recovery etc.
1607 pub fn is_special(self) -> bool {
1608 self.name <= kw::Underscore
1611 /// Returns `true` if the token is a keyword used in the language.
1612 pub fn is_used_keyword(self) -> bool {
1613 // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
1614 self.name >= kw::As && self.name <= kw::While
1615 || self.name.is_used_keyword_2018() && self.span.rust_2018()
1618 /// Returns `true` if the token is a keyword reserved for possible future use.
1619 pub fn is_unused_keyword(self) -> bool {
1620 // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
1621 self.name >= kw::Abstract && self.name <= kw::Yield
1622 || self.name.is_unused_keyword_2018() && self.span.rust_2018()
1625 /// Returns `true` if the token is either a special identifier or a keyword.
1626 pub fn is_reserved(self) -> bool {
1627 self.is_special() || self.is_used_keyword() || self.is_unused_keyword()
1630 /// A keyword or reserved identifier that can be used as a path segment.
1631 pub fn is_path_segment_keyword(self) -> bool {
1632 self.name.is_path_segment_keyword()
1635 /// We see this identifier in a normal identifier position, like variable name or a type.
1636 /// How was it written originally? Did it use the raw form? Let's try to guess.
1637 pub fn is_raw_guess(self) -> bool {
1638 self.name.can_be_raw() && self.is_reserved()
1643 fn with_interner<T, F: FnOnce(&mut Interner) -> T>(f: F) -> T {
1644 SESSION_GLOBALS.with(|session_globals| f(&mut *session_globals.symbol_interner.lock()))
1647 /// An alternative to `Symbol`, useful when the chars within the symbol need to
1648 /// be accessed. It deliberately has limited functionality and should only be
1649 /// used for temporary values.
1651 /// Because the interner outlives any thread which uses this type, we can
1652 /// safely treat `string` which points to interner data, as an immortal string,
1653 /// as long as this type never crosses between threads.
1655 // FIXME: ensure that the interner outlives any thread which uses `SymbolStr`,
1656 // by creating a new thread right after constructing the interner.
1657 #[derive(Clone, Eq, PartialOrd, Ord)]
1658 pub struct SymbolStr {
1659 string: &'static str,
1662 // This impl allows a `SymbolStr` to be directly equated with a `String` or
1664 impl<T: std::ops::Deref<Target = str>> std::cmp::PartialEq<T> for SymbolStr {
1665 fn eq(&self, other: &T) -> bool {
1666 self.string == other.deref()
1670 impl !Send for SymbolStr {}
1671 impl !Sync for SymbolStr {}
1673 /// This impl means that if `ss` is a `SymbolStr`:
1674 /// - `*ss` is a `str`;
1675 /// - `&*ss` is a `&str` (and `match &*ss { ... }` is a common pattern).
1676 /// - `&ss as &str` is a `&str`, which means that `&ss` can be passed to a
1677 /// function expecting a `&str`.
1678 impl std::ops::Deref for SymbolStr {
1681 fn deref(&self) -> &str {
1686 impl fmt::Debug for SymbolStr {
1687 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1688 fmt::Debug::fmt(self.string, f)
1692 impl fmt::Display for SymbolStr {
1693 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1694 fmt::Display::fmt(self.string, f)
1698 impl<CTX> HashStable<CTX> for SymbolStr {
1700 fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
1701 self.string.hash_stable(hcx, hasher)
1705 impl<CTX> ToStableHashKey<CTX> for SymbolStr {
1706 type KeyType = SymbolStr;
1709 fn to_stable_hash_key(&self, _: &CTX) -> SymbolStr {