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 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, GLOBALS};
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.
104 // Symbols that can be referred to with rustc_span::sym::*. The symbol is
105 // the stringified identifier unless otherwise specified (e.g.
106 // `proc_dash_macro` represents "proc-macro").
108 // As well as the symbols listed, there are symbols for the the strings
109 // "0", "1", ..., "9", which are accessible via `sym::integer`.
111 aarch64_target_feature,
115 abi_msp430_interrupt,
125 advanced_slice_patterns,
137 allow_internal_unsafe,
138 allow_internal_unstable,
139 allow_internal_unstable_backcompat_hack,
143 arbitrary_enum_discriminant,
144 arbitrary_self_types,
151 associated_type_bounds,
152 associated_type_defaults,
160 augmented_assignments,
161 automatically_derived,
162 avx512_target_feature,
167 bind_by_move_pattern_guards,
171 borrowck_graphviz_format,
172 borrowck_graphviz_postflow,
173 borrowck_graphviz_preflow,
176 braced_empty_structs,
188 cfg_target_has_atomic,
189 cfg_target_thread_local,
197 closure_to_fn_coercion,
199 cmpxchg16b_target_feature,
206 conservative_impl_trait,
208 const_compare_raw_pointers,
216 const_in_array_repeat_expressions,
222 const_raw_ptr_to_usize_cast,
224 const_trait_bound_opt_out,
238 crate_visibility_modifier,
246 custom_inner_attributes,
247 custom_test_frameworks,
255 default_lib_allocator,
256 default_type_parameter_fallback,
258 delay_span_bug_from_inside_query,
273 document_private_items,
274 dotdoteq_in_patterns,
275 dotdot_in_tuple_patterns,
276 double_braced_crate: "{{crate}}",
277 double_braced_impl: "{{impl}}",
278 double_braced_misc: "{{misc}}",
279 double_braced_closure: "{{closure}}",
280 double_braced_constructor: "{{constructor}}",
281 double_braced_constant: "{{constant}}",
282 double_braced_opaque: "{{opaque}}",
284 dropck_parametricity,
300 exclusive_range_pattern,
301 exhaustive_integer_patterns,
307 extern_absolute_paths,
309 extern_crate_item_prelude,
320 field_init_shorthand,
344 generic_associated_types,
349 half_open_range_patterns,
354 hexagon_target_feature,
356 homogeneous_aggregate,
370 if_while_or_patterns,
372 impl_header_lifetime_elision,
374 impl_trait_in_bindings,
382 inclusive_range_syntax,
383 infer_outlives_requirements,
384 infer_static_outlives_requirements,
391 irrefutable_let_patterns,
394 issue_5723_bootstrap,
395 issue_tracker_base_url,
397 item_context: "ItemContext",
416 link_llvm_intrinsics,
426 macro_at_most_once_rep,
429 macro_lifetime_matcher,
430 macro_literal_matcher,
441 match_beginning_vert,
442 match_default_bindings,
461 movbe_target_feature,
498 object_safe_for_dispatch,
500 omit_gdb_pretty_printer_section,
507 optin_builtin_traits,
517 overlapping_marker_traits,
522 panic_implementation,
542 poll_with_tls_context,
543 powerpc_target_feature,
544 precise_pointer_size_matching,
549 proc_dash_macro: "proc-macro",
551 proc_macro_attribute,
557 proc_macro_internals,
559 proc_macro_non_items,
560 proc_macro_path_invoc,
565 quad_precision_float,
580 reexport_test_harness_main,
592 re_rebalance_coherence,
610 rustc_allocator_nounwind,
611 rustc_allow_const_fn_ptr,
612 rustc_args_required_const,
616 rustc_const_unstable,
618 rustc_conversion_suggestion,
621 rustc_diagnostic_item,
622 rustc_diagnostic_macros,
625 rustc_dump_env_program_clauses,
626 rustc_dump_program_clauses,
627 rustc_dump_user_substs,
629 rustc_expected_cgu_reuse,
630 rustc_if_this_changed,
631 rustc_inherit_overflow_checks,
633 rustc_layout_scalar_valid_range_end,
634 rustc_layout_scalar_valid_range_start,
635 rustc_macro_transparency,
637 rustc_nonnull_optimization_guaranteed,
638 rustc_object_lifetime_default,
639 rustc_on_unimplemented,
642 rustc_partition_codegened,
643 rustc_partition_reused,
645 rustc_peek_definite_init,
646 rustc_peek_maybe_init,
647 rustc_peek_maybe_uninit,
648 rustc_peek_indirectly_mutable,
650 rustc_proc_macro_decls,
654 rustc_std_internal_symbol,
657 rustc_reservation_impl,
659 rustc_then_this_would_need,
663 rust_eh_unwind_resume,
665 rvalue_static_promotion,
689 sse4a_target_feature,
702 stmt_expr_attributes,
704 struct_field_attributes,
714 target_has_atomic_load_store,
719 termination_trait_test,
722 test_accepted_feature,
724 test_removed_feature,
747 type_alias_impl_trait,
752 type_alias_enum_variants,
764 underscore_const_names,
766 underscore_lifetimes,
768 universal_impl_trait,
771 unrestricted_attribute_tokens,
774 unsized_tuple_coercion,
790 visible_private_types,
805 #[derive(Copy, Clone, Eq, HashStable_Generic)]
813 /// Constructs a new identifier from a symbol and a span.
814 pub const fn new(name: Symbol, span: Span) -> Ident {
818 /// Constructs a new identifier with a dummy span.
820 pub const fn with_dummy_span(name: Symbol) -> Ident {
821 Ident::new(name, DUMMY_SP)
825 pub fn invalid() -> Ident {
826 Ident::with_dummy_span(kw::Invalid)
829 /// Maps a string to an identifier with a dummy span.
830 pub fn from_str(string: &str) -> Ident {
831 Ident::with_dummy_span(Symbol::intern(string))
834 /// Maps a string and a span to an identifier.
835 pub fn from_str_and_span(string: &str, span: Span) -> Ident {
836 Ident::new(Symbol::intern(string), span)
839 /// Replaces `lo` and `hi` with those from `span`, but keep hygiene context.
840 pub fn with_span_pos(self, span: Span) -> Ident {
841 Ident::new(self.name, span.with_ctxt(self.span.ctxt()))
844 pub fn without_first_quote(self) -> Ident {
845 Ident::new(Symbol::intern(self.as_str().trim_start_matches('\'')), self.span)
848 /// "Normalize" ident for use in comparisons using "item hygiene".
849 /// Identifiers with same string value become same if they came from the same "modern" macro
850 /// (e.g., `macro` item, but not `macro_rules` item) and stay different if they came from
851 /// different "modern" macros.
852 /// Technically, this operation strips all non-opaque marks from ident's syntactic context.
853 pub fn modern(self) -> Ident {
854 Ident::new(self.name, self.span.modern())
857 /// "Normalize" ident for use in comparisons using "local variable hygiene".
858 /// Identifiers with same string value become same if they came from the same non-transparent
859 /// macro (e.g., `macro` or `macro_rules!` items) and stay different if they came from different
860 /// non-transparent macros.
861 /// Technically, this operation strips all transparent marks from ident's syntactic context.
862 pub fn modern_and_legacy(self) -> Ident {
863 Ident::new(self.name, self.span.modern_and_legacy())
866 /// Convert the name to a `SymbolStr`. This is a slowish operation because
867 /// it requires locking the symbol interner.
868 pub fn as_str(self) -> SymbolStr {
873 impl PartialEq for Ident {
874 fn eq(&self, rhs: &Self) -> bool {
875 self.name == rhs.name && self.span.ctxt() == rhs.span.ctxt()
879 impl Hash for Ident {
880 fn hash<H: Hasher>(&self, state: &mut H) {
881 self.name.hash(state);
882 self.span.ctxt().hash(state);
886 impl fmt::Debug for Ident {
887 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
888 if self.is_raw_guess() {
891 write!(f, "{}{:?}", self.name, self.span.ctxt())
895 impl fmt::Display for Ident {
896 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
897 if self.is_raw_guess() {
900 fmt::Display::fmt(&self.name, f)
904 impl UseSpecializedEncodable for Ident {
905 fn default_encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
906 s.emit_struct("Ident", 2, |s| {
907 s.emit_struct_field("name", 0, |s| self.name.encode(s))?;
908 s.emit_struct_field("span", 1, |s| self.span.encode(s))
913 impl UseSpecializedDecodable for Ident {
914 fn default_decode<D: Decoder>(d: &mut D) -> Result<Self, D::Error> {
915 d.read_struct("Ident", 2, |d| {
917 name: d.read_struct_field("name", 0, Decodable::decode)?,
918 span: d.read_struct_field("span", 1, Decodable::decode)?,
924 /// An interned string.
926 /// Internally, a `Symbol` is implemented as an index, and all operations
927 /// (including hashing, equality, and ordering) operate on that index. The use
928 /// of `rustc_index::newtype_index!` means that `Option<Symbol>` only takes up 4 bytes,
929 /// because `rustc_index::newtype_index!` reserves the last 256 values for tagging purposes.
931 /// Note that `Symbol` cannot directly be a `rustc_index::newtype_index!` because it
932 /// implements `fmt::Debug`, `Encodable`, and `Decodable` in special ways.
933 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
934 pub struct Symbol(SymbolIndex);
936 rustc_index::newtype_index! {
937 pub struct SymbolIndex { .. }
941 const fn new(n: u32) -> Self {
942 Symbol(SymbolIndex::from_u32_const(n))
945 /// Maps a string to its interned representation.
946 pub fn intern(string: &str) -> Self {
947 with_interner(|interner| interner.intern(string))
950 /// Access the symbol's chars. This is a slowish operation because it
951 /// requires locking the symbol interner.
952 pub fn with<F: FnOnce(&str) -> R, R>(self, f: F) -> R {
953 with_interner(|interner| f(interner.get(self)))
956 /// Convert to a `SymbolStr`. This is a slowish operation because it
957 /// requires locking the symbol interner.
958 pub fn as_str(self) -> SymbolStr {
959 with_interner(|interner| unsafe {
960 SymbolStr { string: std::mem::transmute::<&str, &str>(interner.get(self)) }
964 pub fn as_u32(self) -> u32 {
969 impl fmt::Debug for Symbol {
970 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
971 self.with(|str| fmt::Debug::fmt(&str, f))
975 impl fmt::Display for Symbol {
976 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
977 self.with(|str| fmt::Display::fmt(&str, f))
981 impl Encodable for Symbol {
982 fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
983 self.with(|string| s.emit_str(string))
987 impl Decodable for Symbol {
988 fn decode<D: Decoder>(d: &mut D) -> Result<Symbol, D::Error> {
989 Ok(Symbol::intern(&d.read_str()?))
993 impl<CTX> HashStable<CTX> for Symbol {
995 fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
996 self.as_str().hash_stable(hcx, hasher);
1000 impl<CTX> ToStableHashKey<CTX> for Symbol {
1001 type KeyType = SymbolStr;
1004 fn to_stable_hash_key(&self, _: &CTX) -> SymbolStr {
1009 // The `&'static str`s in this type actually point into the arena.
1011 pub struct Interner {
1012 arena: DroplessArena,
1013 names: FxHashMap<&'static str, Symbol>,
1014 strings: Vec<&'static str>,
1018 fn prefill(init: &[&'static str]) -> Self {
1020 strings: init.into(),
1021 names: init.iter().copied().zip((0..).map(Symbol::new)).collect(),
1022 ..Default::default()
1026 pub fn intern(&mut self, string: &str) -> Symbol {
1027 if let Some(&name) = self.names.get(string) {
1031 let name = Symbol::new(self.strings.len() as u32);
1033 // `from_utf8_unchecked` is safe since we just allocated a `&str` which is known to be
1036 unsafe { str::from_utf8_unchecked(self.arena.alloc_slice(string.as_bytes())) };
1037 // It is safe to extend the arena allocation to `'static` because we only access
1038 // these while the arena is still alive.
1039 let string: &'static str = unsafe { &*(string as *const str) };
1040 self.strings.push(string);
1041 self.names.insert(string, name);
1045 // Get the symbol as a string. `Symbol::as_str()` should be used in
1046 // preference to this function.
1047 pub fn get(&self, symbol: Symbol) -> &str {
1048 self.strings[symbol.0.as_usize()]
1052 // This module has a very short name because it's used a lot.
1058 // This module has a very short name because it's used a lot.
1059 #[allow(rustc::default_hash_types)]
1062 use std::convert::TryInto;
1066 // Get the symbol for an integer. The first few non-negative integers each
1067 // have a static symbol and therefore are fast.
1068 pub fn integer<N: TryInto<usize> + Copy + ToString>(n: N) -> Symbol {
1069 if let Result::Ok(idx) = n.try_into() {
1070 if let Option::Some(&sym) = digits_array.get(idx) {
1074 Symbol::intern(&n.to_string())
1079 fn is_used_keyword_2018(self) -> bool {
1080 self >= kw::Async && self <= kw::Dyn
1083 fn is_unused_keyword_2018(self) -> bool {
1087 /// Used for sanity checking rustdoc keyword sections.
1088 pub fn is_doc_keyword(self) -> bool {
1092 /// A keyword or reserved identifier that can be used as a path segment.
1093 pub fn is_path_segment_keyword(self) -> bool {
1095 || self == kw::SelfLower
1096 || self == kw::SelfUpper
1097 || self == kw::Crate
1098 || self == kw::PathRoot
1099 || self == kw::DollarCrate
1102 /// Returns `true` if the symbol is `true` or `false`.
1103 pub fn is_bool_lit(self) -> bool {
1104 self == kw::True || self == kw::False
1107 /// This symbol can be a raw identifier.
1108 pub fn can_be_raw(self) -> bool {
1109 self != kw::Invalid && self != kw::Underscore && !self.is_path_segment_keyword()
1114 // Returns `true` for reserved identifiers used internally for elided lifetimes,
1115 // unnamed method parameters, crate root module, error recovery etc.
1116 pub fn is_special(self) -> bool {
1117 self.name <= kw::Underscore
1120 /// Returns `true` if the token is a keyword used in the language.
1121 pub fn is_used_keyword(self) -> bool {
1122 // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
1123 self.name >= kw::As && self.name <= kw::While
1124 || self.name.is_used_keyword_2018() && self.span.rust_2018()
1127 /// Returns `true` if the token is a keyword reserved for possible future use.
1128 pub fn is_unused_keyword(self) -> bool {
1129 // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
1130 self.name >= kw::Abstract && self.name <= kw::Yield
1131 || self.name.is_unused_keyword_2018() && self.span.rust_2018()
1134 /// Returns `true` if the token is either a special identifier or a keyword.
1135 pub fn is_reserved(self) -> bool {
1136 self.is_special() || self.is_used_keyword() || self.is_unused_keyword()
1139 /// A keyword or reserved identifier that can be used as a path segment.
1140 pub fn is_path_segment_keyword(self) -> bool {
1141 self.name.is_path_segment_keyword()
1144 /// We see this identifier in a normal identifier position, like variable name or a type.
1145 /// How was it written originally? Did it use the raw form? Let's try to guess.
1146 pub fn is_raw_guess(self) -> bool {
1147 self.name.can_be_raw() && self.is_reserved()
1152 fn with_interner<T, F: FnOnce(&mut Interner) -> T>(f: F) -> T {
1153 GLOBALS.with(|globals| f(&mut *globals.symbol_interner.lock()))
1156 /// An alternative to `Symbol`, useful when the chars within the symbol need to
1157 /// be accessed. It deliberately has limited functionality and should only be
1158 /// used for temporary values.
1160 /// Because the interner outlives any thread which uses this type, we can
1161 /// safely treat `string` which points to interner data, as an immortal string,
1162 /// as long as this type never crosses between threads.
1164 // FIXME: ensure that the interner outlives any thread which uses `SymbolStr`,
1165 // by creating a new thread right after constructing the interner.
1166 #[derive(Clone, Eq, PartialOrd, Ord)]
1167 pub struct SymbolStr {
1168 string: &'static str,
1171 // This impl allows a `SymbolStr` to be directly equated with a `String` or
1173 impl<T: std::ops::Deref<Target = str>> std::cmp::PartialEq<T> for SymbolStr {
1174 fn eq(&self, other: &T) -> bool {
1175 self.string == other.deref()
1179 impl !Send for SymbolStr {}
1180 impl !Sync for SymbolStr {}
1182 /// This impl means that if `ss` is a `SymbolStr`:
1183 /// - `*ss` is a `str`;
1184 /// - `&*ss` is a `&str`;
1185 /// - `&ss as &str` is a `&str`, which means that `&ss` can be passed to a
1186 /// function expecting a `&str`.
1187 impl std::ops::Deref for SymbolStr {
1190 fn deref(&self) -> &str {
1195 impl fmt::Debug for SymbolStr {
1196 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1197 fmt::Debug::fmt(self.string, f)
1201 impl fmt::Display for SymbolStr {
1202 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1203 fmt::Display::fmt(self.string, f)
1207 impl<CTX> HashStable<CTX> for SymbolStr {
1209 fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
1210 self.string.hash_stable(hcx, hasher)
1214 impl<CTX> ToStableHashKey<CTX> for SymbolStr {
1215 type KeyType = SymbolStr;
1218 fn to_stable_hash_key(&self, _: &CTX) -> SymbolStr {