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 `compiler/rustc_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
191 ProceduralMasqueradeDummyType,
232 aarch64_target_feature,
236 abi_c_cmse_nonsecure_call,
238 abi_msp430_interrupt,
251 advanced_slice_patterns,
266 allow_internal_unsafe,
267 allow_internal_unstable,
273 arbitrary_enum_discriminant,
274 arbitrary_self_types,
286 assert_receiver_is_total_eq,
290 associated_type_bounds,
291 associated_type_defaults,
302 augmented_assignments,
304 automatically_derived,
305 avx512_target_feature,
311 bind_by_move_pattern_guards,
322 borrowck_graphviz_format,
323 borrowck_graphviz_postflow,
324 borrowck_graphviz_preflow,
328 braced_empty_structs,
339 capture_disjoint_fields,
352 cfg_target_has_atomic,
353 cfg_target_thread_local,
363 closure_to_fn_coercion,
365 cmpxchg16b_target_feature,
366 cmse_nonsecure_entry,
374 conservative_impl_trait,
377 const_compare_raw_pointers,
380 const_evaluatable_checked,
383 const_fn_floating_point_arithmetic,
384 const_fn_fn_ptr_basics,
388 const_generics_defaults,
391 const_in_array_repeat_expressions,
397 const_precise_live_drops,
400 const_raw_ptr_to_usize_cast,
403 const_trait_bound_opt_out,
419 core_panic_2015_macro,
428 crate_visibility_modifier,
429 crt_dash_static: "crt-static",
438 custom_inner_attributes,
439 custom_test_frameworks,
453 default_alloc_error_handler,
454 default_lib_allocator,
455 default_type_parameter_fallback,
457 delay_span_bug_from_inside_query,
465 destructuring_assignment,
481 document_private_items,
482 dotdot_in_tuple_patterns,
483 dotdoteq_in_patterns,
491 dropck_parametricity,
500 emit_enum_variant_arg,
508 ermsb_target_feature,
513 exclusive_range_pattern,
514 exhaustive_integer_patterns,
525 extended_key_value_attributes,
526 extern_absolute_paths,
527 extern_crate_item_prelude,
549 field_init_shorthand,
554 float_to_int_unchecked,
582 from_size_align_unchecked,
595 generic_associated_types,
602 half_open_range_patterns,
606 hexagon_target_feature,
608 homogeneous_aggregate,
625 if_while_or_patterns,
627 impl_header_lifetime_elision,
630 impl_trait_in_bindings,
636 inclusive_range_syntax,
639 infer_outlives_requirements,
640 infer_static_outlives_requirements,
641 inherent_associated_types,
653 irrefutable_let_patterns,
657 issue_5723_bootstrap,
658 issue_tracker_base_url,
670 lazy_normalization_consts,
682 link_llvm_intrinsics,
701 macro_at_most_once_rep,
702 macro_attributes_in_derive_output,
705 macro_lifetime_matcher,
706 macro_literal_matcher,
718 match_beginning_vert,
719 match_default_bindings,
739 min_type_alias_impl_trait,
747 movbe_target_feature,
796 nontrapping_dash_fptoint: "nontrapping-fptoint",
804 object_safe_for_dispatch,
807 omit_gdb_pretty_printer_section,
816 optin_builtin_traits,
825 overlapping_marker_traits,
835 panic_implementation,
865 post_dash_lto: "post-lto",
866 powerpc_target_feature,
871 pre_dash_lto: "pre-lto",
872 precise_pointer_size_matching,
876 prefetch_read_instruction,
878 prefetch_write_instruction,
883 proc_dash_macro: "proc-macro",
885 proc_macro_attribute,
891 proc_macro_internals,
893 proc_macro_non_items,
894 proc_macro_path_invoc,
907 quad_precision_float,
914 re_rebalance_coherence,
917 read_enum_variant_arg,
925 reexport_test_harness_main,
938 relaxed_struct_unsize,
954 riscv_target_feature,
970 rust_eh_catch_typeinfo,
972 rust_eh_register_frames,
973 rust_eh_unregister_frames,
977 rustc_allocator_nounwind,
978 rustc_allow_const_fn_unstable,
979 rustc_args_required_const,
982 rustc_capture_analysis,
985 rustc_const_unstable,
986 rustc_conversion_suggestion,
989 rustc_diagnostic_item,
990 rustc_diagnostic_macros,
993 rustc_dump_env_program_clauses,
994 rustc_dump_program_clauses,
995 rustc_dump_user_substs,
997 rustc_expected_cgu_reuse,
998 rustc_if_this_changed,
999 rustc_inherit_overflow_checks,
1001 rustc_layout_scalar_valid_range_end,
1002 rustc_layout_scalar_valid_range_start,
1003 rustc_legacy_const_generics,
1004 rustc_macro_transparency,
1006 rustc_nonnull_optimization_guaranteed,
1007 rustc_object_lifetime_default,
1008 rustc_on_unimplemented,
1011 rustc_partition_codegened,
1012 rustc_partition_reused,
1014 rustc_peek_definite_init,
1015 rustc_peek_indirectly_mutable,
1016 rustc_peek_liveness,
1017 rustc_peek_maybe_init,
1018 rustc_peek_maybe_uninit,
1019 rustc_polymorphize_error,
1021 rustc_proc_macro_decls,
1024 rustc_reservation_impl,
1026 rustc_specialization_trait,
1028 rustc_std_internal_symbol,
1032 rustc_then_this_would_need,
1033 rustc_unsafe_specialization_marker,
1037 rvalue_static_promotion,
1085 simd_reduce_add_ordered,
1086 simd_reduce_add_unordered,
1091 simd_reduce_max_nanless,
1093 simd_reduce_min_nanless,
1094 simd_reduce_mul_ordered,
1095 simd_reduce_mul_unordered,
1099 simd_saturating_add,
1100 simd_saturating_sub,
1103 simd_select_bitmask,
1130 sse4a_target_feature,
1142 std_panic_2015_macro,
1145 stmt_expr_attributes,
1146 stop_after_dataflow,
1151 struct_field_attributes,
1173 target_has_atomic_equal_alignment,
1174 target_has_atomic_load_store,
1176 target_pointer_width,
1177 target_target_vendor,
1178 target_thread_local,
1184 termination_trait_test,
1187 test_accepted_feature,
1189 test_removed_feature,
1216 type_alias_enum_variants,
1217 type_alias_impl_trait,
1228 unaligned_volatile_load,
1229 unaligned_volatile_store,
1238 underscore_const_names,
1240 underscore_lifetimes,
1243 universal_impl_trait,
1250 unrestricted_attribute_tokens,
1251 unsafe_block_in_unsafe_fn,
1253 unsafe_no_drop_flag,
1257 unsized_tuple_coercion,
1260 unused_qualifications,
1283 visible_private_types,
1285 volatile_copy_memory,
1286 volatile_copy_nonoverlapping_memory,
1288 volatile_set_memory,
1294 wasm_target_feature,
1309 #[derive(Copy, Clone, Eq, HashStable_Generic, Encodable, Decodable)]
1317 /// Constructs a new identifier from a symbol and a span.
1318 pub const fn new(name: Symbol, span: Span) -> Ident {
1319 Ident { name, span }
1322 /// Constructs a new identifier with a dummy span.
1324 pub const fn with_dummy_span(name: Symbol) -> Ident {
1325 Ident::new(name, DUMMY_SP)
1329 pub fn invalid() -> Ident {
1330 Ident::with_dummy_span(kw::Empty)
1333 /// Maps a string to an identifier with a dummy span.
1334 pub fn from_str(string: &str) -> Ident {
1335 Ident::with_dummy_span(Symbol::intern(string))
1338 /// Maps a string and a span to an identifier.
1339 pub fn from_str_and_span(string: &str, span: Span) -> Ident {
1340 Ident::new(Symbol::intern(string), span)
1343 /// Replaces `lo` and `hi` with those from `span`, but keep hygiene context.
1344 pub fn with_span_pos(self, span: Span) -> Ident {
1345 Ident::new(self.name, span.with_ctxt(self.span.ctxt()))
1348 pub fn without_first_quote(self) -> Ident {
1349 Ident::new(Symbol::intern(self.as_str().trim_start_matches('\'')), self.span)
1352 /// "Normalize" ident for use in comparisons using "item hygiene".
1353 /// Identifiers with same string value become same if they came from the same macro 2.0 macro
1354 /// (e.g., `macro` item, but not `macro_rules` item) and stay different if they came from
1355 /// different macro 2.0 macros.
1356 /// Technically, this operation strips all non-opaque marks from ident's syntactic context.
1357 pub fn normalize_to_macros_2_0(self) -> Ident {
1358 Ident::new(self.name, self.span.normalize_to_macros_2_0())
1361 /// "Normalize" ident for use in comparisons using "local variable hygiene".
1362 /// Identifiers with same string value become same if they came from the same non-transparent
1363 /// macro (e.g., `macro` or `macro_rules!` items) and stay different if they came from different
1364 /// non-transparent macros.
1365 /// Technically, this operation strips all transparent marks from ident's syntactic context.
1366 pub fn normalize_to_macro_rules(self) -> Ident {
1367 Ident::new(self.name, self.span.normalize_to_macro_rules())
1370 /// Convert the name to a `SymbolStr`. This is a slowish operation because
1371 /// it requires locking the symbol interner.
1372 pub fn as_str(self) -> SymbolStr {
1377 impl PartialEq for Ident {
1378 fn eq(&self, rhs: &Self) -> bool {
1379 self.name == rhs.name && self.span.ctxt() == rhs.span.ctxt()
1383 impl Hash for Ident {
1384 fn hash<H: Hasher>(&self, state: &mut H) {
1385 self.name.hash(state);
1386 self.span.ctxt().hash(state);
1390 impl fmt::Debug for Ident {
1391 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1392 fmt::Display::fmt(self, f)?;
1393 fmt::Debug::fmt(&self.span.ctxt(), f)
1397 /// This implementation is supposed to be used in error messages, so it's expected to be identical
1398 /// to printing the original identifier token written in source code (`token_to_string`),
1399 /// except that AST identifiers don't keep the rawness flag, so we have to guess it.
1400 impl fmt::Display for Ident {
1401 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1402 fmt::Display::fmt(&IdentPrinter::new(self.name, self.is_raw_guess(), None), f)
1406 /// This is the most general way to print identifiers.
1407 /// AST pretty-printer is used as a fallback for turning AST structures into token streams for
1408 /// proc macros. Additionally, proc macros may stringify their input and expect it survive the
1409 /// stringification (especially true for proc macro derives written between Rust 1.15 and 1.30).
1410 /// So we need to somehow pretty-print `$crate` in a way preserving at least some of its
1411 /// hygiene data, most importantly name of the crate it refers to.
1412 /// As a result we print `$crate` as `crate` if it refers to the local crate
1413 /// and as `::other_crate_name` if it refers to some other crate.
1414 /// Note, that this is only done if the ident token is printed from inside of AST pretty-pringing,
1415 /// but not otherwise. Pretty-printing is the only way for proc macros to discover token contents,
1416 /// so we should not perform this lossy conversion if the top level call to the pretty-printer was
1417 /// done for a token stream or a single token.
1418 pub struct IdentPrinter {
1421 /// Span used for retrieving the crate name to which `$crate` refers to,
1422 /// if this field is `None` then the `$crate` conversion doesn't happen.
1423 convert_dollar_crate: Option<Span>,
1427 /// The most general `IdentPrinter` constructor. Do not use this.
1428 pub fn new(symbol: Symbol, is_raw: bool, convert_dollar_crate: Option<Span>) -> IdentPrinter {
1429 IdentPrinter { symbol, is_raw, convert_dollar_crate }
1432 /// This implementation is supposed to be used when printing identifiers
1433 /// as a part of pretty-printing for larger AST pieces.
1434 /// Do not use this either.
1435 pub fn for_ast_ident(ident: Ident, is_raw: bool) -> IdentPrinter {
1436 IdentPrinter::new(ident.name, is_raw, Some(ident.span))
1440 impl fmt::Display for IdentPrinter {
1441 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1444 } else if self.symbol == kw::DollarCrate {
1445 if let Some(span) = self.convert_dollar_crate {
1446 let converted = span.ctxt().dollar_crate_name();
1447 if !converted.is_path_segment_keyword() {
1450 return fmt::Display::fmt(&converted, f);
1453 fmt::Display::fmt(&self.symbol, f)
1457 /// An newtype around `Ident` that calls [Ident::normalize_to_macro_rules] on
1459 // FIXME(matthewj, petrochenkov) Use this more often, add a similar
1460 // `ModernIdent` struct and use that as well.
1461 #[derive(Copy, Clone, Eq, PartialEq, Hash)]
1462 pub struct MacroRulesNormalizedIdent(Ident);
1464 impl MacroRulesNormalizedIdent {
1465 pub fn new(ident: Ident) -> Self {
1466 Self(ident.normalize_to_macro_rules())
1470 impl fmt::Debug for MacroRulesNormalizedIdent {
1471 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1472 fmt::Debug::fmt(&self.0, f)
1476 impl fmt::Display for MacroRulesNormalizedIdent {
1477 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1478 fmt::Display::fmt(&self.0, f)
1482 /// An interned string.
1484 /// Internally, a `Symbol` is implemented as an index, and all operations
1485 /// (including hashing, equality, and ordering) operate on that index. The use
1486 /// of `rustc_index::newtype_index!` means that `Option<Symbol>` only takes up 4 bytes,
1487 /// because `rustc_index::newtype_index!` reserves the last 256 values for tagging purposes.
1489 /// Note that `Symbol` cannot directly be a `rustc_index::newtype_index!` because it
1490 /// implements `fmt::Debug`, `Encodable`, and `Decodable` in special ways.
1491 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
1492 pub struct Symbol(SymbolIndex);
1494 rustc_index::newtype_index! {
1495 pub struct SymbolIndex { .. }
1499 const fn new(n: u32) -> Self {
1500 Symbol(SymbolIndex::from_u32(n))
1503 /// Maps a string to its interned representation.
1504 pub fn intern(string: &str) -> Self {
1505 with_interner(|interner| interner.intern(string))
1508 /// Convert to a `SymbolStr`. This is a slowish operation because it
1509 /// requires locking the symbol interner.
1510 pub fn as_str(self) -> SymbolStr {
1511 with_interner(|interner| unsafe {
1512 SymbolStr { string: std::mem::transmute::<&str, &str>(interner.get(self)) }
1516 pub fn as_u32(self) -> u32 {
1520 pub fn is_empty(self) -> bool {
1524 /// This method is supposed to be used in error messages, so it's expected to be
1525 /// identical to printing the original identifier token written in source code
1526 /// (`token_to_string`, `Ident::to_string`), except that symbols don't keep the rawness flag
1527 /// or edition, so we have to guess the rawness using the global edition.
1528 pub fn to_ident_string(self) -> String {
1529 Ident::with_dummy_span(self).to_string()
1533 impl fmt::Debug for Symbol {
1534 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1535 fmt::Debug::fmt(&self.as_str(), f)
1539 impl fmt::Display for Symbol {
1540 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1541 fmt::Display::fmt(&self.as_str(), f)
1545 impl<S: Encoder> Encodable<S> for Symbol {
1546 fn encode(&self, s: &mut S) -> Result<(), S::Error> {
1547 s.emit_str(&self.as_str())
1551 impl<D: Decoder> Decodable<D> for Symbol {
1553 fn decode(d: &mut D) -> Result<Symbol, D::Error> {
1554 Ok(Symbol::intern(&d.read_str()?))
1558 impl<CTX> HashStable<CTX> for Symbol {
1560 fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
1561 self.as_str().hash_stable(hcx, hasher);
1565 impl<CTX> ToStableHashKey<CTX> for Symbol {
1566 type KeyType = SymbolStr;
1569 fn to_stable_hash_key(&self, _: &CTX) -> SymbolStr {
1574 // The `&'static str`s in this type actually point into the arena.
1576 // The `FxHashMap`+`Vec` pair could be replaced by `FxIndexSet`, but #75278
1577 // found that to regress performance up to 2% in some cases. This might be
1578 // revisited after further improvements to `indexmap`.
1580 pub struct Interner {
1581 arena: DroplessArena,
1582 names: FxHashMap<&'static str, Symbol>,
1583 strings: Vec<&'static str>,
1587 fn prefill(init: &[&'static str]) -> Self {
1589 strings: init.into(),
1590 names: init.iter().copied().zip((0..).map(Symbol::new)).collect(),
1591 ..Default::default()
1596 pub fn intern(&mut self, string: &str) -> Symbol {
1597 if let Some(&name) = self.names.get(string) {
1601 let name = Symbol::new(self.strings.len() as u32);
1603 // `from_utf8_unchecked` is safe since we just allocated a `&str` which is known to be
1606 unsafe { str::from_utf8_unchecked(self.arena.alloc_slice(string.as_bytes())) };
1607 // It is safe to extend the arena allocation to `'static` because we only access
1608 // these while the arena is still alive.
1609 let string: &'static str = unsafe { &*(string as *const str) };
1610 self.strings.push(string);
1611 self.names.insert(string, name);
1615 // Get the symbol as a string. `Symbol::as_str()` should be used in
1616 // preference to this function.
1617 pub fn get(&self, symbol: Symbol) -> &str {
1618 self.strings[symbol.0.as_usize()]
1622 // This module has a very short name because it's used a lot.
1623 /// This module contains all the defined keyword `Symbol`s.
1625 /// Given that `kw` is imported, use them like `kw::keyword_name`.
1626 /// For example `kw::Loop` or `kw::Break`.
1628 pub use super::kw_generated::*;
1631 // This module has a very short name because it's used a lot.
1632 /// This module contains all the defined non-keyword `Symbol`s.
1634 /// Given that `sym` is imported, use them like `sym::symbol_name`.
1635 /// For example `sym::rustfmt` or `sym::u8`.
1638 use std::convert::TryInto;
1641 pub use super::sym_generated::*;
1643 // Used from a macro in `librustc_feature/accepted.rs`
1644 pub use super::kw::MacroRules as macro_rules;
1646 /// Get the symbol for an integer.
1648 /// The first few non-negative integers each have a static symbol and therefore
1650 pub fn integer<N: TryInto<usize> + Copy + ToString>(n: N) -> Symbol {
1651 if let Result::Ok(idx) = n.try_into() {
1653 return Symbol::new(super::SYMBOL_DIGITS_BASE + idx as u32);
1656 Symbol::intern(&n.to_string())
1661 fn is_special(self) -> bool {
1662 self <= kw::Underscore
1665 fn is_used_keyword_always(self) -> bool {
1666 self >= kw::As && self <= kw::While
1669 fn is_used_keyword_conditional(self, edition: impl FnOnce() -> Edition) -> bool {
1670 (self >= kw::Async && self <= kw::Dyn) && edition() >= Edition::Edition2018
1673 fn is_unused_keyword_always(self) -> bool {
1674 self >= kw::Abstract && self <= kw::Yield
1677 fn is_unused_keyword_conditional(self, edition: impl FnOnce() -> Edition) -> bool {
1678 self == kw::Try && edition() >= Edition::Edition2018
1681 pub fn is_reserved(self, edition: impl Copy + FnOnce() -> Edition) -> bool {
1683 || self.is_used_keyword_always()
1684 || self.is_unused_keyword_always()
1685 || self.is_used_keyword_conditional(edition)
1686 || self.is_unused_keyword_conditional(edition)
1689 /// A keyword or reserved identifier that can be used as a path segment.
1690 pub fn is_path_segment_keyword(self) -> bool {
1692 || self == kw::SelfLower
1693 || self == kw::SelfUpper
1694 || self == kw::Crate
1695 || self == kw::PathRoot
1696 || self == kw::DollarCrate
1699 /// Returns `true` if the symbol is `true` or `false`.
1700 pub fn is_bool_lit(self) -> bool {
1701 self == kw::True || self == kw::False
1704 /// Returns `true` if this symbol can be a raw identifier.
1705 pub fn can_be_raw(self) -> bool {
1706 self != kw::Empty && self != kw::Underscore && !self.is_path_segment_keyword()
1711 // Returns `true` for reserved identifiers used internally for elided lifetimes,
1712 // unnamed method parameters, crate root module, error recovery etc.
1713 pub fn is_special(self) -> bool {
1714 self.name.is_special()
1717 /// Returns `true` if the token is a keyword used in the language.
1718 pub fn is_used_keyword(self) -> bool {
1719 // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
1720 self.name.is_used_keyword_always()
1721 || self.name.is_used_keyword_conditional(|| self.span.edition())
1724 /// Returns `true` if the token is a keyword reserved for possible future use.
1725 pub fn is_unused_keyword(self) -> bool {
1726 // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
1727 self.name.is_unused_keyword_always()
1728 || self.name.is_unused_keyword_conditional(|| self.span.edition())
1731 /// Returns `true` if the token is either a special identifier or a keyword.
1732 pub fn is_reserved(self) -> bool {
1733 // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
1734 self.name.is_reserved(|| self.span.edition())
1737 /// A keyword or reserved identifier that can be used as a path segment.
1738 pub fn is_path_segment_keyword(self) -> bool {
1739 self.name.is_path_segment_keyword()
1742 /// We see this identifier in a normal identifier position, like variable name or a type.
1743 /// How was it written originally? Did it use the raw form? Let's try to guess.
1744 pub fn is_raw_guess(self) -> bool {
1745 self.name.can_be_raw() && self.is_reserved()
1750 fn with_interner<T, F: FnOnce(&mut Interner) -> T>(f: F) -> T {
1751 SESSION_GLOBALS.with(|session_globals| f(&mut *session_globals.symbol_interner.lock()))
1754 /// An alternative to [`Symbol`], useful when the chars within the symbol need to
1755 /// be accessed. It deliberately has limited functionality and should only be
1756 /// used for temporary values.
1758 /// Because the interner outlives any thread which uses this type, we can
1759 /// safely treat `string` which points to interner data, as an immortal string,
1760 /// as long as this type never crosses between threads.
1762 // FIXME: ensure that the interner outlives any thread which uses `SymbolStr`,
1763 // by creating a new thread right after constructing the interner.
1764 #[derive(Clone, Eq, PartialOrd, Ord)]
1765 pub struct SymbolStr {
1766 string: &'static str,
1769 // This impl allows a `SymbolStr` to be directly equated with a `String` or
1771 impl<T: std::ops::Deref<Target = str>> std::cmp::PartialEq<T> for SymbolStr {
1772 fn eq(&self, other: &T) -> bool {
1773 self.string == other.deref()
1777 impl !Send for SymbolStr {}
1778 impl !Sync for SymbolStr {}
1780 /// This impl means that if `ss` is a `SymbolStr`:
1781 /// - `*ss` is a `str`;
1782 /// - `&*ss` is a `&str` (and `match &*ss { ... }` is a common pattern).
1783 /// - `&ss as &str` is a `&str`, which means that `&ss` can be passed to a
1784 /// function expecting a `&str`.
1785 impl std::ops::Deref for SymbolStr {
1788 fn deref(&self) -> &str {
1793 impl fmt::Debug for SymbolStr {
1794 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1795 fmt::Debug::fmt(self.string, f)
1799 impl fmt::Display for SymbolStr {
1800 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1801 fmt::Display::fmt(self.string, f)
1805 impl<CTX> HashStable<CTX> for SymbolStr {
1807 fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
1808 self.string.hash_stable(hcx, hasher)
1812 impl<CTX> ToStableHashKey<CTX> for SymbolStr {
1813 type KeyType = SymbolStr;
1816 fn to_stable_hash_key(&self, _: &CTX) -> SymbolStr {