//! An "interner" is a data structure that associates values with usize tags and
//! allows bidirectional lookup; i.e., given a value, one can easily find the
//! type, and vice versa.

use std::hash::{Hash, Hasher};
use std::{fmt, str};

use rustc_arena::DroplessArena;
use rustc_data_structures::fx::{FxHashSet, FxIndexSet};
use rustc_data_structures::stable_hasher::{
    HashStable, StableCompare, StableHasher, ToStableHashKey,
};
use rustc_data_structures::sync::Lock;
use rustc_macros::{Decodable, Encodable, HashStable_Generic, symbols};

use crate::edit_distance::find_best_match_for_name;
use crate::{DUMMY_SP, Edition, Span, with_session_globals};

#[cfg(test)]
mod tests;

// The proc macro code for this is in `compiler/rustc_macros/src/symbols.rs`.
symbols! {
    // This list includes things that are definitely keywords (e.g. `if`), a
    // few things that are definitely not keywords (e.g. `{{root}}`) and things
    // where there is disagreement between people and/or documents (such as the
    // Rust Reference) about whether it is a keyword (e.g. `_`).
    //
    // If you modify this list, adjust any relevant `Symbol::{is,can_be}_*`
    // predicates and `used_keywords`. Also consider adding new keywords to the
    // `ui/parser/raw/raw-idents.rs` test.
    Keywords {
        // Special reserved identifiers used internally for unnamed method
        // parameters, crate root module, etc.
        // Matching predicates: `is_special`/`is_reserved`
        //
        // tidy-alphabetical-start
        DollarCrate:        "$crate",
        PathRoot:           "{{root}}",
        Underscore:         "_",
        // tidy-alphabetical-end

        // Keywords that are used in stable Rust.
        // Matching predicates: `is_used_keyword_always`/`is_reserved`
        // tidy-alphabetical-start
        As:                 "as",
        Break:              "break",
        Const:              "const",
        Continue:           "continue",
        Crate:              "crate",
        Else:               "else",
        Enum:               "enum",
        Extern:             "extern",
        False:              "false",
        Fn:                 "fn",
        For:                "for",
        If:                 "if",
        Impl:               "impl",
        In:                 "in",
        Let:                "let",
        Loop:               "loop",
        Match:              "match",
        Mod:                "mod",
        Move:               "move",
        Mut:                "mut",
        Pub:                "pub",
        Ref:                "ref",
        Return:             "return",
        SelfLower:          "self",
        SelfUpper:          "Self",
        Static:             "static",
        Struct:             "struct",
        Super:              "super",
        Trait:              "trait",
        True:               "true",
        Type:               "type",
        Unsafe:             "unsafe",
        Use:                "use",
        Where:              "where",
        While:              "while",
        // tidy-alphabetical-end

        // Keywords that are used in unstable Rust or reserved for future use.
        // Matching predicates: `is_unused_keyword_always`/`is_reserved`
        // tidy-alphabetical-start
        Abstract:           "abstract",
        Become:             "become",
        Box:                "box",
        Do:                 "do",
        Final:              "final",
        Macro:              "macro",
        Override:           "override",
        Priv:               "priv",
        Typeof:             "typeof",
        Unsized:            "unsized",
        Virtual:            "virtual",
        Yield:              "yield",
        // tidy-alphabetical-end

        // Edition-specific keywords that are used in stable Rust.
        // Matching predicates: `is_used_keyword_conditional`/`is_reserved` (if
        // the edition suffices)
        // tidy-alphabetical-start
        Async:              "async", // >= 2018 Edition only
        Await:              "await", // >= 2018 Edition only
        Dyn:                "dyn", // >= 2018 Edition only
        // tidy-alphabetical-end

        // Edition-specific keywords that are used in unstable Rust or reserved for future use.
        // Matching predicates: `is_unused_keyword_conditional`/`is_reserved` (if
        // the edition suffices)
        // tidy-alphabetical-start
        Gen:                "gen", // >= 2024 Edition only
        Try:                "try", // >= 2018 Edition only
        // tidy-alphabetical-end

        // "Lifetime keywords": regular keywords with a leading `'`.
        // Matching predicates: none
        // tidy-alphabetical-start
        StaticLifetime:     "'static",
        UnderscoreLifetime: "'_",
        // tidy-alphabetical-end

        // Weak keywords, have special meaning only in specific contexts.
        // Matching predicates: `is_weak`
        // tidy-alphabetical-start
        Auto:               "auto",
        Builtin:            "builtin",
        Catch:              "catch",
        ContractEnsures:    "contract_ensures",
        ContractRequires:   "contract_requires",
        Default:            "default",
        MacroRules:         "macro_rules",
        Raw:                "raw",
        Reuse:              "reuse",
        Safe:               "safe",
        Union:              "union",
        Yeet:               "yeet",
        // tidy-alphabetical-end
    }

    // Pre-interned symbols that can be referred to with `rustc_span::sym::*`.
    //
    // The symbol is the stringified identifier unless otherwise specified, in
    // which case the name should mention the non-identifier punctuation.
    // E.g. `sym::proc_dash_macro` represents "proc-macro", and it shouldn't be
    // called `sym::proc_macro` because then it's easy to mistakenly think it
    // represents "proc_macro".
    //
    // As well as the symbols listed, there are symbols for the strings
    // "0", "1", ..., "9", which are accessible via `sym::integer`.
    //
    // There is currently no checking that all symbols are used; that would be
    // nice to have.
    Symbols {
        // tidy-alphabetical-start
        Abi,
        AcqRel,
        Acquire,
        Active,
        ActiveOnly,
        Alignment,
        Arc,
        ArcWeak,
        Array,
        AsMut,
        AsRef,
        AssertParamIsClone,
        AssertParamIsCopy,
        AssertParamIsEq,
        AsyncGenFinished,
        AsyncGenPending,
        AsyncGenReady,
        AtomicBool,
        AtomicI8,
        AtomicI16,
        AtomicI32,
        AtomicI64,
        AtomicI128,
        AtomicIsize,
        AtomicPtr,
        AtomicU8,
        AtomicU16,
        AtomicU32,
        AtomicU64,
        AtomicU128,
        AtomicUsize,
        BTreeMap,
        Bool,
        Borrow,
        BorrowMut,
        Break,
        BuildHasher,
        C,
        CStr,
        CallOnceFuture,
        CallRefFuture,
        Capture,
        Cell,
        Char,
        Cleanup,
        Clone,
        CoercePointee,
        CoercePointeeValidated,
        CoerceUnsized,
        Const,
        ConstParamTy,
        ConstParamTy_,
        Context,
        Continue,
        ControlFlow,
        Copy,
        Debug,
        Default,
        Deref,
        DispatchFromDyn,
        Display,
        Dual,
        DualOnly,
        Dualv,
        DualvOnly,
        Duplicated,
        DuplicatedOnly,
        DynTrait,
        Enum,
        Eq,
        Equal,
        Err,
        ExternC,
        ExternRust,
        Float,
        FmtArgumentsNew,
        Fn,
        FnMut,
        FnOnce,
        FnPtr,
        Formatter,
        Forward,
        From,
        FromIterator,
        FromResidual,
        GlobalAlloc,
        Hash,
        HashMap,
        HashSet,
        Hasher,
        InCleanup,
        IndexOutput,
        Input,
        Int,
        Into,
        IntoFuture,
        IntoIterator,
        IntoIteratorItem,
        IrTyKind,
        Item,
        ItemContext,
        Iterator,
        IteratorItem,
        IteratorMap,
        Layout,
        Lifetime,
        LintPass,
        LocalKey,
        Mutex,
        MutexGuard,
        Named,
        NonNull,
        NonZero,
        None,
        Normal,
        Ok,
        Option,
        Ord,
        Ordering,
        Other,
        Output,
        ParamSet,
        PartialEq,
        PartialOrd,
        Pending,
        PinDerefMutHelper,
        Pointer,
        Poll,
        ProcMacro,
        Range,
        RangeCopy,
        RangeFrom,
        RangeFromCopy,
        RangeFull,
        RangeInclusive,
        RangeInclusiveCopy,
        RangeMax,
        RangeMin,
        RangeSub,
        RangeTo,
        RangeToInclusive,
        RangeToInclusiveCopy,
        Rc,
        RcWeak,
        Ready,
        RefCell,
        Reference,
        Relaxed,
        Release,
        Result,
        ResumeTy,
        Reverse,
        Rust,
        RustaceansAreAwesome,
        RwLock,
        RwLockReadGuard,
        RwLockWriteGuard,
        SelfTy,
        Send,
        SeqCst,
        Sized,
        Slice,
        SliceIndex,
        Some,
        Source,
        SpanCtxt,
        Str,
        String,
        Struct,
        StructuralPartialEq,
        SymbolIntern,
        Sync,
        SyncUnsafeCell,
        Target,
        This,
        TokenStream,
        Trait,
        TrivialClone,
        Try,
        TryCaptureGeneric,
        TryCapturePrintable,
        TryFrom,
        TryInto,
        Tuple,
        Ty,
        TyCtxt,
        TyKind,
        Type,
        Union,
        Unsize,
        Vec,
        Wrapper,
        _DECLS,
        __H,
        __S,
        __awaitee,
        __try_var,
        _t,
        _task_context,
        a32,
        aarch64,
        aarch64_target_feature,
        aarch64_unstable_target_feature,
        aarch64_ver_target_feature,
        abi,
        abi_amdgpu_kernel,
        abi_avr_interrupt,
        abi_c_cmse_nonsecure_call,
        abi_cmse_nonsecure_call,
        abi_custom,
        abi_efiapi,
        abi_gpu_kernel,
        abi_msp430_interrupt,
        abi_ptx,
        abi_riscv_interrupt,
        abi_sysv64,
        abi_thiscall,
        abi_unadjusted,
        abi_vectorcall,
        abi_x86_interrupt,
        abort,
        add,
        add_assign,
        add_with_overflow,
        address,
        adt_const_params,
        advanced_slice_patterns,
        adx_target_feature,
        aes,
        aggregate_raw_ptr,
        alias,
        align,
        align_of,
        align_of_val,
        alignment,
        all,
        alloc,
        alloc_error_handler,
        alloc_layout,
        alloc_zeroed,
        allocator,
        allocator_api,
        allocator_internals,
        allow,
        allow_fail,
        allow_internal_unsafe,
        allow_internal_unstable,
        altivec,
        alu32,
        always,
        amdgpu,
        amdgpu_dispatch_ptr,
        analysis,
        and,
        and_then,
        anon,
        anon_assoc,
        anonymous_lifetime_in_impl_trait,
        any,
        append_const_msg,
        apx_target_feature,
        arbitrary_enum_discriminant,
        arbitrary_self_types,
        arbitrary_self_types_pointers,
        areg,
        args,
        arith_offset,
        arm,
        arm64ec,
        arm_a32: "arm::a32",
        arm_t32: "arm::t32",
        arm_target_feature,
        array,
        as_dash_needed: "as-needed",
        as_ref,
        asm,
        asm_cfg,
        asm_const,
        asm_experimental_arch,
        asm_experimental_reg,
        asm_goto,
        asm_goto_with_outputs,
        asm_sym,
        asm_unwind,
        assert,
        assert_eq,
        assert_eq_macro,
        assert_fields_are_eq,
        assert_inhabited,
        assert_macro,
        assert_mem_uninitialized_valid,
        assert_ne_macro,
        assert_receiver_is_total_eq,
        assert_zero_valid,
        asserting,
        associated_const_equality,
        associated_consts,
        associated_type_bounds,
        associated_type_defaults,
        associated_types,
        assume,
        assume_init,
        asterisk: "*",
        async_await,
        async_call,
        async_call_mut,
        async_call_once,
        async_closure,
        async_drop,
        async_drop_in_place,
        async_fn,
        async_fn_in_dyn_trait,
        async_fn_in_trait,
        async_fn_kind_helper,
        async_fn_kind_upvars,
        async_fn_mut,
        async_fn_once,
        async_fn_once_output,
        async_fn_track_caller,
        async_fn_traits,
        async_for_loop,
        async_gen_internals,
        async_iterator,
        async_iterator_poll_next,
        async_trait_bounds,
        atomic_and,
        atomic_cxchg,
        atomic_cxchgweak,
        atomic_fence,
        atomic_load,
        atomic_max,
        atomic_min,
        atomic_mod,
        atomic_nand,
        atomic_or,
        atomic_singlethreadfence,
        atomic_store,
        atomic_umax,
        atomic_umin,
        atomic_xadd,
        atomic_xchg,
        atomic_xor,
        atomic_xsub,
        atomics,
        att_syntax,
        attr,
        attr_literals,
        attribute,
        attributes,
        audit_that,
        augmented_assignments,
        auto_cfg,
        auto_traits,
        autodiff,
        autodiff_forward,
        autodiff_reverse,
        automatically_derived,
        available_externally,
        avr,
        avr_target_feature,
        avx,
        avx10_target_feature,
        avx512_target_feature,
        avx512bw,
        avx512f,
        await_macro,
        bang,
        begin_panic,
        bench,
        bevy_ecs,
        bikeshed,
        bikeshed_guaranteed_no_drop,
        bin,
        bind_by_move_pattern_guards,
        bindings_after_at,
        bitand,
        bitand_assign,
        bitor,
        bitor_assign,
        bitreverse,
        bits,
        bitxor,
        bitxor_assign,
        black_box,
        block,
        blocking,
        bool,
        borrowck_graphviz_format,
        borrowck_graphviz_postflow,
        box_new,
        box_patterns,
        box_syntax,
        boxed_slice,
        bpf,
        bpf_target_feature,
        braced_empty_structs,
        branch,
        breakpoint,
        bridge,
        bswap,
        built,
        builtin_syntax,
        bundle,
        c,
        c_dash_variadic,
        c_str_literals,
        c_unwind,
        c_variadic,
        c_variadic_naked_functions,
        c_void,
        call,
        call_mut,
        call_once,
        call_once_future,
        call_ref_future,
        caller,
        caller_location,
        capture_disjoint_fields,
        carrying_mul_add,
        carryless_mul,
        catch_unwind,
        cause,
        cdylib,
        ceilf16,
        ceilf32,
        ceilf64,
        ceilf128,
        cfg,
        cfg_accessible,
        cfg_attr,
        cfg_attr_multi,
        cfg_attr_trace: "<cfg_attr_trace>", // must not be a valid identifier
        cfg_boolean_literals,
        cfg_contract_checks,
        cfg_doctest,
        cfg_emscripten_wasm_eh,
        cfg_eval,
        cfg_overflow_checks,
        cfg_panic,
        cfg_relocation_model,
        cfg_sanitize,
        cfg_sanitizer_cfi,
        cfg_select,
        cfg_target_abi,
        cfg_target_compact,
        cfg_target_feature,
        cfg_target_has_atomic,
        cfg_target_has_atomic_equal_alignment,
        cfg_target_has_reliable_f16_f128,
        cfg_target_thread_local,
        cfg_target_vendor,
        cfg_trace: "<cfg_trace>", // must not be a valid identifier
        cfg_ub_checks,
        cfg_version,
        cfi,
        cfi_encoding,
        char,
        client,
        clippy,
        clobber_abi,
        clone,
        clone_closures,
        clone_fn,
        clone_from,
        closure,
        closure_lifetime_binder,
        closure_to_fn_coercion,
        closure_track_caller,
        cmp,
        cmp_ord_max,
        cmp_ord_min,
        cmp_partialeq_eq,
        cmp_partialeq_ne,
        cmp_partialord_cmp,
        cmp_partialord_ge,
        cmp_partialord_gt,
        cmp_partialord_le,
        cmp_partialord_lt,
        cmpxchg16b_target_feature,
        cmse_nonsecure_entry,
        coerce_pointee_validated,
        coerce_shared,
        coerce_unsized,
        cold,
        cold_path,
        collapse_debuginfo,
        column,
        common,
        compare_bytes,
        compare_exchange,
        compare_exchange_weak,
        compile_error,
        compiler,
        compiler_builtins,
        compiler_copy,
        compiler_fence,
        compiler_move,
        concat,
        concat_bytes,
        concat_idents,
        conservative_impl_trait,
        console,
        const_allocate,
        const_async_blocks,
        const_block_items,
        const_c_variadic,
        const_closures,
        const_compare_raw_pointers,
        const_constructor,
        const_continue,
        const_deallocate,
        const_destruct,
        const_eval_limit,
        const_eval_select,
        const_evaluatable_checked,
        const_extern_fn,
        const_fn,
        const_fn_floating_point_arithmetic,
        const_fn_fn_ptr_basics,
        const_fn_trait_bound,
        const_fn_transmute,
        const_fn_union,
        const_fn_unsize,
        const_for,
        const_format_args,
        const_generics,
        const_generics_defaults,
        const_if_match,
        const_impl_trait,
        const_in_array_repeat_expressions,
        const_indexing,
        const_let,
        const_loop,
        const_make_global,
        const_mut_refs,
        const_panic,
        const_panic_fmt,
        const_param_ty,
        const_precise_live_drops,
        const_ptr_cast,
        const_raw_ptr_deref,
        const_raw_ptr_to_usize_cast,
        const_refs_to_cell,
        const_refs_to_static,
        const_trait_bound_opt_out,
        const_trait_impl,
        const_try,
        const_ty_placeholder: "<const_ty>",
        constant,
        constructor,
        contract_build_check_ensures,
        contract_check_ensures,
        contract_check_requires,
        contract_checks,
        contracts,
        contracts_ensures,
        contracts_internals,
        contracts_requires,
        convert,
        copy,
        copy_closures,
        copy_nonoverlapping,
        copysignf16,
        copysignf32,
        copysignf64,
        copysignf128,
        core,
        core_panic,
        core_panic_2015_macro,
        core_panic_macro,
        coroutine,
        coroutine_clone,
        coroutine_resume,
        coroutine_return,
        coroutine_state,
        coroutine_yield,
        coroutines,
        cosf16,
        cosf32,
        cosf64,
        cosf128,
        count,
        coverage,
        coverage_attribute,
        cr,
        crate_in_paths,
        crate_local,
        crate_name,
        crate_type,
        crate_visibility_modifier,
        crt_dash_static: "crt-static",
        csky,
        csky_target_feature,
        cstr_type,
        cstring_type,
        ctlz,
        ctlz_nonzero,
        ctpop,
        ctr,
        cttz,
        cttz_nonzero,
        custom_attribute,
        custom_code_classes_in_docs,
        custom_derive,
        custom_inner_attributes,
        custom_mir,
        custom_test_frameworks,
        d,
        d32,
        dead_code,
        dealloc,
        debug,
        debug_assert_eq_macro,
        debug_assert_macro,
        debug_assert_ne_macro,
        debug_assertions,
        debug_struct_fields_finish,
        debug_tuple_fields_finish,
        debugger_visualizer,
        decl_macro,
        declare_lint_pass,
        decorated,
        default_alloc_error_handler,
        default_field_values,
        default_fn,
        default_lib_allocator,
        default_method_body_is_const,
        // --------------------------
        // Lang items which are used only for experiments with auto traits with default bounds.
        // These lang items are not actually defined in core/std. Experiment is a part of
        // `MCP: Low level components for async drop`(https://github.com/rust-lang/compiler-team/issues/727)
        default_trait1,
        default_trait2,
        default_trait3,
        default_trait4,
        // --------------------------
        default_type_parameter_fallback,
        default_type_params,
        define_opaque,
        deny,
        deprecated,
        deprecated_safe,
        deprecated_suggestion,
        deref,
        deref_method,
        deref_mut,
        deref_patterns,
        deref_pure,
        deref_target,
        derive,
        derive_const,
        derive_const_issue: "118304",
        derive_default_enum,
        derive_from,
        derive_smart_pointer,
        destruct,
        destructuring_assignment,
        diagnostic,
        diagnostic_namespace,
        diagnostic_on_const,
        dialect,
        direct,
        discriminant_kind,
        discriminant_type,
        discriminant_value,
        disjoint_bitor,
        dispatch_from_dyn,
        div,
        div_assign,
        diverging_block_default,
        dl,
        do_not_recommend,
        doc,
        doc_alias,
        doc_auto_cfg,
        doc_cfg,
        doc_cfg_hide,
        doc_keyword,
        doc_masked,
        doc_notable_trait,
        doc_primitive,
        doc_spotlight,
        doctest,
        dotdot_in_tuple_patterns,
        dotdoteq_in_patterns,
        dreg,
        dreg_low8,
        dreg_low16,
        drop,
        drop_in_place,
        drop_types_in_const,
        dropck_eyepatch,
        dropck_parametricity,
        dummy: "<!dummy!>", // use this instead of `sym::empty` for symbols that won't be used
        dummy_cgu_name,
        dylib,
        dyn_compatible_for_dispatch,
        dyn_metadata,
        dyn_star,
        dyn_trait,
        dynamic_no_pic: "dynamic-no-pic",
        e,
        edition_panic,
        effective_target_features,
        effects,
        eh_catch_typeinfo,
        eh_personality,
        eii,
        eii_declaration,
        eii_internals,
        eii_shared_macro,
        element_ty,
        // Notes about `sym::empty`:
        // - It should only be used when it genuinely means "empty symbol". Use
        //   `Option<Symbol>` when "no symbol" is a possibility.
        // - For dummy symbols that are never used and absolutely must be
        //   present, it's better to use `sym::dummy` than `sym::empty`, because
        //   it's clearer that it's intended as a dummy value, and more likely
        //   to be detected if it accidentally does get used.
        empty: "",
        empty_braces: "{}",
        emscripten_wasm_eh,
        enable,
        end,
        entry_nops,
        env,
        env_CFG_RELEASE: env!("CFG_RELEASE"),
        eq,
        ergonomic_clones,
        ermsb_target_feature,
        exact_div,
        except,
        exception_handling: "exception-handling",
        exclusive_range_pattern,
        exhaustive_integer_patterns,
        exhaustive_patterns,
        existential_type,
        exp2f16,
        exp2f32,
        exp2f64,
        exp2f128,
        expect,
        expected,
        expf16,
        expf32,
        expf64,
        expf128,
        explicit_extern_abis,
        explicit_generic_args_with_impl_trait,
        explicit_tail_calls,
        export_name,
        export_stable,
        export_symbols: "export-symbols",
        expr,
        expr_2021,
        expr_fragment_specifier_2024,
        extended_key_value_attributes,
        extended_varargs_abi_support,
        extern_absolute_paths,
        extern_crate_item_prelude,
        extern_crate_self,
        extern_in_paths,
        extern_item_impls,
        extern_prelude,
        extern_system_varargs,
        extern_types,
        extern_weak,
        external,
        external_doc,
        f,
        f16,
        f16_nan,
        f16c_target_feature,
        f32,
        f32_nan,
        f64,
        f64_nan,
        f128,
        f128_nan,
        fabsf16,
        fabsf32,
        fabsf64,
        fabsf128,
        fadd_algebraic,
        fadd_fast,
        fake_variadic,
        fallback,
        fdiv_algebraic,
        fdiv_fast,
        feature,
        fence,
        ferris: "🦀",
        fetch_update,
        ffi_const,
        ffi_pure,
        ffi_returns_twice,
        field_init_shorthand,
        fields,
        file,
        final_associated_functions,
        float_to_int_unchecked,
        floorf16,
        floorf32,
        floorf64,
        floorf128,
        fmaf16,
        fmaf32,
        fmaf64,
        fmaf128,
        fmt,
        fmt_debug,
        fmul_algebraic,
        fmul_fast,
        fmuladdf16,
        fmuladdf32,
        fmuladdf64,
        fmuladdf128,
        fn_align,
        fn_body,
        fn_delegation,
        fn_must_use,
        fn_mut,
        fn_once,
        fn_once_output,
        fn_ptr_addr,
        fn_ptr_trait,
        forbid,
        force_target_feature,
        forget,
        format_args,
        format_args_capture,
        format_args_nl,
        format_argument,
        format_arguments,
        format_macro,
        framework,
        freeze,
        freeze_impls,
        freg,
        frem_algebraic,
        frem_fast,
        from,
        from_desugaring,
        from_iter,
        from_output,
        from_residual,
        from_size_align_unchecked,
        from_size_alignment_unchecked,
        from_str,
        from_str_nonconst,
        from_usize,
        from_yeet,
        frontmatter,
        fsub_algebraic,
        fsub_fast,
        full,
        fundamental,
        fused_iterator,
        future_output,
        future_trait,
        fxsr,
        gdb_script_file,
        ge,
        gen_blocks,
        gen_future,
        generator_clone,
        generators,
        generic_arg_infer,
        generic_assert,
        generic_associated_types,
        generic_associated_types_extended,
        generic_const_exprs,
        generic_const_items,
        generic_const_parameter_types,
        generic_param_attrs,
        generic_pattern_types,
        generics,
        get_context,
        global_alloc_ty,
        global_allocator,
        global_asm,
        global_registration,
        globs,
        gt,
        guard_patterns,
        half_open_range_patterns,
        half_open_range_patterns_in_slices,
        hash,
        hexagon,
        hexagon_target_feature,
        hidden,
        hide,
        homogeneous_aggregate,
        html_favicon_url,
        html_logo_url,
        html_no_source,
        html_playground_url,
        html_root_url,
        hwaddress,
        i8,
        i16,
        i32,
        i64,
        i128,
        i128_type,
        ident,
        if_let,
        if_let_guard,
        if_let_rescope,
        if_while_or_patterns,
        ignore,
        immediate_abort: "immediate-abort",
        impl_header_lifetime_elision,
        impl_lint_pass,
        impl_trait_in_assoc_type,
        impl_trait_in_bindings,
        impl_trait_in_fn_trait_return,
        impl_trait_projections,
        implied_by,
        import,
        import_name_type,
        import_shadowing,
        import_trait_associated_functions,
        imported_main,
        in_band_lifetimes,
        include,
        include_bytes,
        include_str,
        inclusive_range_syntax,
        index,
        index_mut,
        infer_outlives_requirements,
        infer_static_outlives_requirements,
        inherent_associated_types,
        initial,
        inlateout,
        inline,
        inline_const,
        inline_const_pat,
        inout,
        inputs,
        instruction_set,
        integer_: "integer", // underscore to avoid clashing with the function `sym::integer` below
        integral,
        internal,
        internal_eq_trait_method_impls,
        internal_features,
        into_async_iter_into_iter,
        into_future,
        into_iter,
        into_try_type,
        intra_doc_pointers,
        intrinsics,
        irrefutable_let_patterns,
        is,
        is_auto,
        is_val_statically_known,
        isa_attribute,
        isize,
        issue,
        issue_5723_bootstrap,
        issue_tracker_base_url,
        item,
        item_like_imports,
        iter,
        iter_mut,
        iterator,
        iterator_collect_fn,
        kcfi,
        kernel_address,
        keylocker_x86,
        keyword,
        kind,
        kreg,
        kreg0,
        label,
        label_break_value,
        lahfsahf_target_feature,
        lang,
        lang_items,
        large_assignments,
        last,
        lateout,
        lazy_normalization_consts,
        lazy_type_alias,
        le,
        legacy_receiver,
        len,
        let_chains,
        let_else,
        lhs,
        lib,
        libc,
        lifetime,
        lifetime_capture_rules_2024,
        lifetimes,
        line,
        link,
        link_arg_attribute,
        link_args,
        link_cfg,
        link_dash_arg: "link-arg",
        link_llvm_intrinsics,
        link_name,
        link_ordinal,
        link_section,
        linkage,
        linker,
        linker_messages,
        linkonce,
        linkonce_odr,
        lint_reasons,
        literal,
        load,
        loaded_from_disk,
        local,
        local_inner_macros,
        log2f16,
        log2f32,
        log2f64,
        log2f128,
        log10f16,
        log10f32,
        log10f64,
        log10f128,
        log_syntax,
        logf16,
        logf32,
        logf64,
        logf128,
        loongarch32,
        loongarch64,
        loongarch_target_feature,
        loop_break_value,
        loop_match,
        lr,
        lt,
        m68k,
        m68k_target_feature,
        macro_at_most_once_rep,
        macro_attr,
        macro_attributes_in_derive_output,
        macro_derive,
        macro_escape,
        macro_export,
        macro_lifetime_matcher,
        macro_literal_matcher,
        macro_metavar_expr,
        macro_metavar_expr_concat,
        macro_reexport,
        macro_use,
        macro_vis_matcher,
        macros_in_extern,
        main,
        managed_boxes,
        manually_drop,
        map,
        map_err,
        marker,
        marker_trait_attr,
        masked,
        match_beginning_vert,
        match_default_bindings,
        maximumf16,
        maximumf32,
        maximumf64,
        maximumf128,
        maxnumf16,
        maxnumf32,
        maxnumf64,
        maxnumf128,
        may_dangle,
        may_unwind,
        maybe_uninit,
        maybe_uninit_uninit,
        maybe_uninit_zeroed,
        mem_align_const,
        mem_discriminant,
        mem_drop,
        mem_forget,
        mem_size_const,
        mem_swap,
        mem_uninitialized,
        mem_variant_count,
        mem_zeroed,
        member_constraints,
        memory,
        memtag,
        message,
        meta,
        meta_sized,
        metadata_type,
        mgca_type_const_syntax,
        min_const_fn,
        min_const_generics,
        min_const_unsafe_fn,
        min_exhaustive_patterns,
        min_generic_const_args,
        min_specialization,
        min_type_alias_impl_trait,
        minimumf16,
        minimumf32,
        minimumf64,
        minimumf128,
        minnumf16,
        minnumf32,
        minnumf64,
        minnumf128,
        mips,
        mips32r6,
        mips64,
        mips64r6,
        mips_target_feature,
        mir_assume,
        mir_basic_block,
        mir_call,
        mir_cast_ptr_to_ptr,
        mir_cast_transmute,
        mir_cast_unsize,
        mir_checked,
        mir_debuginfo,
        mir_discriminant,
        mir_drop,
        mir_field,
        mir_goto,
        mir_make_place,
        mir_move,
        mir_offset,
        mir_ptr_metadata,
        mir_retag,
        mir_return,
        mir_return_to,
        mir_set_discriminant,
        mir_static,
        mir_static_mut,
        mir_storage_dead,
        mir_storage_live,
        mir_tail_call,
        mir_unreachable,
        mir_unwind_cleanup,
        mir_unwind_continue,
        mir_unwind_resume,
        mir_unwind_terminate,
        mir_unwind_terminate_reason,
        mir_unwind_unreachable,
        mir_variant,
        miri,
        mmx_reg,
        modifiers,
        module,
        module_path,
        more_maybe_bounds,
        more_qualified_paths,
        more_struct_aliases,
        movbe_target_feature,
        move_ref_pattern,
        move_size_limit,
        movrs_target_feature,
        msp430,
        mul,
        mul_assign,
        mul_with_overflow,
        multiple_supertrait_upcastable,
        must_not_suspend,
        must_use,
        mut_preserve_binding_mode_2024,
        mut_ref,
        mutable,
        naked,
        naked_asm,
        naked_functions,
        naked_functions_rustic_abi,
        naked_functions_target_feature,
        name,
        names,
        native_link_modifiers,
        native_link_modifiers_as_needed,
        native_link_modifiers_bundle,
        native_link_modifiers_verbatim,
        native_link_modifiers_whole_archive,
        natvis_file,
        ne,
        needs_allocator,
        needs_drop,
        needs_panic_runtime,
        neg,
        negate_unsigned,
        negative_bounds,
        negative_impls,
        neon,
        nested,
        never,
        never_patterns,
        never_type,
        never_type_fallback,
        new,
        new_binary,
        new_debug,
        new_debug_noop,
        new_display,
        new_lower_exp,
        new_lower_hex,
        new_octal,
        new_pointer,
        new_range,
        new_unchecked,
        new_upper_exp,
        new_upper_hex,
        next,
        nll,
        no,
        no_builtins,
        no_core,
        no_coverage,
        no_crate_inject,
        no_debug,
        no_default_passes,
        no_implicit_prelude,
        no_inline,
        no_link,
        no_main,
        no_mangle,
        no_sanitize,
        no_stack_check,
        no_std,
        nomem,
        non_ascii_idents,
        non_exhaustive,
        non_exhaustive_omitted_patterns_lint,
        non_lifetime_binders,
        non_modrs_mods,
        nonblocking,
        none,
        nontemporal_store,
        noop_method_borrow,
        noop_method_clone,
        noop_method_deref,
        noprefix,
        noreturn,
        nostack,
        not,
        notable_trait,
        note,
        null,
        nvptx64,
        nvptx_target_feature,
        object_safe_for_dispatch,
        of,
        off,
        offload,
        offset,
        offset_of,
        offset_of_enum,
        offset_of_nested,
        offset_of_slice,
        ok_or_else,
        old_name,
        omit_gdb_pretty_printer_section,
        on,
        on_const,
        on_unimplemented,
        opaque,
        opaque_generic_const_args,
        opaque_module_name_placeholder: "<opaque>",
        ops,
        opt_out_copy,
        optimize,
        optimize_attribute,
        optimized,
        optin_builtin_traits,
        option,
        option_env,
        options,
        or,
        or_patterns,
        ord_cmp_method,
        other,
        out,
        output,
        overflow_checks,
        overlapping_marker_traits,
        owned_box,
        packed,
        packed_bundled_libs,
        panic,
        panic_2015,
        panic_2021,
        panic_abort,
        panic_bounds_check,
        panic_cannot_unwind,
        panic_const_add_overflow,
        panic_const_async_fn_resumed,
        panic_const_async_fn_resumed_drop,
        panic_const_async_fn_resumed_panic,
        panic_const_async_gen_fn_resumed,
        panic_const_async_gen_fn_resumed_drop,
        panic_const_async_gen_fn_resumed_panic,
        panic_const_coroutine_resumed,
        panic_const_coroutine_resumed_drop,
        panic_const_coroutine_resumed_panic,
        panic_const_div_by_zero,
        panic_const_div_overflow,
        panic_const_gen_fn_none,
        panic_const_gen_fn_none_drop,
        panic_const_gen_fn_none_panic,
        panic_const_mul_overflow,
        panic_const_neg_overflow,
        panic_const_rem_by_zero,
        panic_const_rem_overflow,
        panic_const_shl_overflow,
        panic_const_shr_overflow,
        panic_const_sub_overflow,
        panic_display,
        panic_fmt,
        panic_handler,
        panic_impl,
        panic_implementation,
        panic_in_cleanup,
        panic_info,
        panic_invalid_enum_construction,
        panic_location,
        panic_misaligned_pointer_dereference,
        panic_nounwind,
        panic_null_pointer_dereference,
        panic_runtime,
        panic_str_2015,
        panic_unwind,
        panicking,
        param_attrs,
        parent_label,
        partial_cmp,
        partial_ord,
        passes,
        pat,
        pat_param,
        patchable_function_entry,
        path,
        pattern_complexity_limit,
        pattern_parentheses,
        pattern_type,
        pattern_type_range_trait,
        pattern_types,
        phantom_data,
        phase,
        pic,
        pie,
        pin,
        pin_ergonomics,
        pin_v2,
        platform_intrinsics,
        plugin,
        plugin_registrar,
        plugins,
        pointee,
        pointee_sized,
        pointee_trait,
        pointer,
        poll,
        post_cleanup: "post-cleanup",
        post_dash_lto: "post-lto",
        postfix_match,
        powerpc,
        powerpc64,
        powerpc_target_feature,
        powf16,
        powf32,
        powf64,
        powf128,
        powif16,
        powif32,
        powif64,
        powif128,
        pre_dash_lto: "pre-lto",
        precise_capturing,
        precise_capturing_in_traits,
        precise_pointer_size_matching,
        predicates,
        pref_align_of,
        prefetch_read_data,
        prefetch_read_instruction,
        prefetch_write_data,
        prefetch_write_instruction,
        prefix_nops,
        preg,
        prelude,
        prelude_import,
        preserves_flags,
        prfchw_target_feature,
        proc_dash_macro: "proc-macro",
        proc_macro,
        proc_macro_attribute,
        proc_macro_derive,
        proc_macro_expr,
        proc_macro_gen,
        proc_macro_hygiene,
        proc_macro_internals,
        proc_macro_mod,
        proc_macro_non_items,
        proc_macro_path_invoc,
        profiler_runtime,
        ptr,
        ptr_cast,
        ptr_cast_const,
        ptr_cast_mut,
        ptr_const_is_null,
        ptr_copy,
        ptr_copy_nonoverlapping,
        ptr_from_ref,
        ptr_guaranteed_cmp,
        ptr_is_null,
        ptr_mask,
        ptr_metadata,
        ptr_null,
        ptr_null_mut,
        ptr_offset_from,
        ptr_offset_from_unsigned,
        ptr_read,
        ptr_read_unaligned,
        ptr_replace,
        ptr_swap,
        ptr_swap_nonoverlapping,
        ptr_write,
        ptr_write_bytes,
        ptr_write_unaligned,
        ptr_write_volatile,
        pub_macro_rules,
        pub_restricted,
        public,
        pure,
        pushpop_unsafe,
        qreg,
        qreg_low4,
        qreg_low8,
        quad_precision_float,
        question_mark,
        quote,
        range_inclusive_new,
        raw_dash_dylib: "raw-dylib",
        raw_dylib,
        raw_dylib_elf,
        raw_eq,
        raw_identifiers,
        raw_ref_op,
        re_rebalance_coherence,
        read_via_copy,
        readonly,
        realloc,
        realtime,
        reason,
        reborrow,
        receiver,
        receiver_target,
        recursion_limit,
        reexport_test_harness_main,
        ref_pat_eat_one_layer_2024,
        ref_pat_eat_one_layer_2024_structural,
        ref_pat_everywhere,
        ref_unwind_safe_trait,
        reference,
        reflect,
        reg,
        reg16,
        reg32,
        reg64,
        reg_abcd,
        reg_addr,
        reg_byte,
        reg_data,
        reg_iw,
        reg_nonzero,
        reg_pair,
        reg_ptr,
        reg_upper,
        register_attr,
        register_tool,
        relaxed_adts,
        relaxed_struct_unsize,
        relocation_model,
        rem,
        rem_assign,
        repr,
        repr128,
        repr_align,
        repr_align_enum,
        repr_packed,
        repr_simd,
        repr_transparent,
        require,
        reserve_x18: "reserve-x18",
        residual,
        result,
        result_ffi_guarantees,
        return_position_impl_trait_in_trait,
        return_type_notation,
        riscv32,
        riscv64,
        riscv_target_feature,
        rlib,
        ropi,
        ropi_rwpi: "ropi-rwpi",
        rotate_left,
        rotate_right,
        round_ties_even_f16,
        round_ties_even_f32,
        round_ties_even_f64,
        round_ties_even_f128,
        roundf16,
        roundf32,
        roundf64,
        roundf128,
        rtm_target_feature,
        runtime,
        rust,
        rust_2015,
        rust_2018,
        rust_2018_preview,
        rust_2021,
        rust_2024,
        rust_analyzer,
        rust_begin_unwind,
        rust_cold_cc,
        rust_eh_catch_typeinfo,
        rust_eh_personality,
        rust_future,
        rust_logo,
        rust_out,
        rust_preserve_none_cc,
        rustc,
        rustc_abi,
        // FIXME(#82232, #143834): temporary name to mitigate `#[align]` nameres ambiguity
        rustc_align,
        rustc_align_static,
        rustc_allocator,
        rustc_allocator_zeroed,
        rustc_allocator_zeroed_variant,
        rustc_allow_const_fn_unstable,
        rustc_allow_incoherent_impl,
        rustc_allowed_through_unstable_modules,
        rustc_as_ptr,
        rustc_attrs,
        rustc_autodiff,
        rustc_builtin_macro,
        rustc_capture_analysis,
        rustc_clean,
        rustc_coherence_is_core,
        rustc_coinductive,
        rustc_confusables,
        rustc_const_stable,
        rustc_const_stable_indirect,
        rustc_const_unstable,
        rustc_conversion_suggestion,
        rustc_deallocator,
        rustc_def_path,
        rustc_default_body_unstable,
        rustc_delayed_bug_from_inside_query,
        rustc_deny_explicit_impl,
        rustc_deprecated_safe_2024,
        rustc_diagnostic_item,
        rustc_diagnostic_macros,
        rustc_do_not_const_check,
        rustc_doc_primitive,
        rustc_driver,
        rustc_dummy,
        rustc_dump_def_parents,
        rustc_dump_item_bounds,
        rustc_dump_predicates,
        rustc_dump_user_args,
        rustc_dump_vtable,
        rustc_dyn_incompatible_trait,
        rustc_effective_visibility,
        rustc_eii_foreign_item,
        rustc_evaluate_where_clauses,
        rustc_expected_cgu_reuse,
        rustc_force_inline,
        rustc_has_incoherent_inherent_impls,
        rustc_hidden_type_of_opaques,
        rustc_if_this_changed,
        rustc_inherit_overflow_checks,
        rustc_insignificant_dtor,
        rustc_intrinsic,
        rustc_intrinsic_const_stable_indirect,
        rustc_layout,
        rustc_layout_scalar_valid_range_end,
        rustc_layout_scalar_valid_range_start,
        rustc_legacy_const_generics,
        rustc_lint_opt_deny_field_access,
        rustc_lint_opt_ty,
        rustc_lint_query_instability,
        rustc_lint_untracked_query_information,
        rustc_macro_transparency,
        rustc_main,
        rustc_mir,
        rustc_must_implement_one_of,
        rustc_never_returns_null_ptr,
        rustc_never_type_options,
        rustc_no_implicit_autorefs,
        rustc_no_implicit_bounds,
        rustc_no_mir_inline,
        rustc_non_const_trait_method,
        rustc_nonnull_optimization_guaranteed,
        rustc_nounwind,
        rustc_objc_class,
        rustc_objc_selector,
        rustc_object_lifetime_default,
        rustc_offload_kernel,
        rustc_on_unimplemented,
        rustc_outlives,
        rustc_paren_sugar,
        rustc_partition_codegened,
        rustc_partition_reused,
        rustc_pass_by_value,
        rustc_pass_indirectly_in_non_rustic_abis,
        rustc_peek,
        rustc_peek_liveness,
        rustc_peek_maybe_init,
        rustc_peek_maybe_uninit,
        rustc_preserve_ub_checks,
        rustc_private,
        rustc_proc_macro_decls,
        rustc_promotable,
        rustc_pub_transparent,
        rustc_reallocator,
        rustc_regions,
        rustc_reservation_impl,
        rustc_scalable_vector,
        rustc_should_not_be_called_on_const_items,
        rustc_simd_monomorphize_lane_limit,
        rustc_skip_during_method_dispatch,
        rustc_specialization_trait,
        rustc_std_internal_symbol,
        rustc_strict_coherence,
        rustc_symbol_name,
        rustc_test_marker,
        rustc_then_this_would_need,
        rustc_trivial_field_reads,
        rustc_unsafe_specialization_marker,
        rustc_variance,
        rustc_variance_of_opaques,
        rustdoc,
        rustdoc_internals,
        rustdoc_missing_doc_code_examples,
        rustfmt,
        rvalue_static_promotion,
        rwpi,
        s390x,
        s390x_target_feature,
        s390x_target_feature_vector,
        safety,
        sanitize,
        sanitizer_cfi_generalize_pointers,
        sanitizer_cfi_normalize_integers,
        sanitizer_runtime,
        saturating_add,
        saturating_sub,
        sdylib,
        search_unbox,
        select_unpredictable,
        self_in_typedefs,
        self_struct_ctor,
        semiopaque,
        sha2,
        sha3,
        sha512_sm_x86,
        shadow_call_stack,
        shallow,
        shl,
        shl_assign,
        shorter_tail_lifetimes,
        should_panic,
        show,
        shr,
        shr_assign,
        signed,
        simd,
        simd_add,
        simd_and,
        simd_arith_offset,
        simd_as,
        simd_bitmask,
        simd_bitreverse,
        simd_bswap,
        simd_carryless_mul,
        simd_cast,
        simd_cast_ptr,
        simd_ceil,
        simd_ctlz,
        simd_ctpop,
        simd_cttz,
        simd_div,
        simd_eq,
        simd_expose_provenance,
        simd_extract,
        simd_extract_dyn,
        simd_fabs,
        simd_fcos,
        simd_fexp,
        simd_fexp2,
        simd_ffi,
        simd_flog,
        simd_flog2,
        simd_flog10,
        simd_floor,
        simd_fma,
        simd_fmax,
        simd_fmin,
        simd_fsin,
        simd_fsqrt,
        simd_funnel_shl,
        simd_funnel_shr,
        simd_gather,
        simd_ge,
        simd_gt,
        simd_insert,
        simd_insert_dyn,
        simd_le,
        simd_lt,
        simd_masked_load,
        simd_masked_store,
        simd_mul,
        simd_ne,
        simd_neg,
        simd_or,
        simd_reduce_add_ordered,
        simd_reduce_add_unordered,
        simd_reduce_all,
        simd_reduce_and,
        simd_reduce_any,
        simd_reduce_max,
        simd_reduce_min,
        simd_reduce_mul_ordered,
        simd_reduce_mul_unordered,
        simd_reduce_or,
        simd_reduce_xor,
        simd_relaxed_fma,
        simd_rem,
        simd_round,
        simd_round_ties_even,
        simd_saturating_add,
        simd_saturating_sub,
        simd_scatter,
        simd_select,
        simd_select_bitmask,
        simd_shl,
        simd_shr,
        simd_shuffle,
        simd_shuffle_const_generic,
        simd_splat,
        simd_sub,
        simd_trunc,
        simd_with_exposed_provenance,
        simd_xor,
        since,
        sinf16,
        sinf32,
        sinf64,
        sinf128,
        size,
        size_of,
        size_of_val,
        sized,
        sized_hierarchy,
        slice,
        slice_from_raw_parts,
        slice_from_raw_parts_mut,
        slice_get_unchecked,
        slice_len_fn,
        slice_patterns,
        slicing_syntax,
        soft,
        sparc,
        sparc64,
        sparc_target_feature,
        spe_acc,
        specialization,
        speed,
        spirv,
        spotlight,
        sqrtf16,
        sqrtf32,
        sqrtf64,
        sqrtf128,
        sreg,
        sreg_low16,
        sse,
        sse2,
        sse4a_target_feature,
        stable,
        staged_api,
        start,
        state,
        static_align,
        static_in_const,
        static_nobundle,
        static_recursion,
        staticlib,
        std,
        std_lib_injection,
        std_panic,
        std_panic_2015_macro,
        std_panic_macro,
        stmt,
        stmt_expr_attributes,
        stop_after_dataflow,
        store,
        str,
        str_from_utf8,
        str_from_utf8_mut,
        str_from_utf8_unchecked,
        str_from_utf8_unchecked_mut,
        str_inherent_from_utf8,
        str_inherent_from_utf8_mut,
        str_inherent_from_utf8_unchecked,
        str_inherent_from_utf8_unchecked_mut,
        strict_provenance_lints,
        string_deref_patterns,
        stringify,
        struct_field_attributes,
        struct_inherit,
        struct_variant,
        structural_match,
        structural_peq,
        sub,
        sub_assign,
        sub_with_overflow,
        suggestion,
        super_let,
        supertrait_item_shadowing,
        sym,
        sync,
        synthetic,
        t32,
        target,
        target_abi,
        target_arch,
        target_endian,
        target_env,
        target_family,
        target_feature,
        target_feature_11,
        target_feature_inline_always,
        target_has_atomic,
        target_has_atomic_equal_alignment,
        target_has_atomic_load_store,
        target_has_reliable_f16,
        target_has_reliable_f16_math,
        target_has_reliable_f128,
        target_has_reliable_f128_math,
        target_os,
        target_pointer_width,
        target_thread_local,
        target_vendor,
        tbm_target_feature,
        termination,
        termination_trait,
        termination_trait_test,
        test,
        test_2018_feature,
        test_accepted_feature,
        test_case,
        test_removed_feature,
        test_runner,
        test_unstable_lint,
        thread,
        thread_local,
        three_way_compare,
        thumb2,
        thumb_mode: "thumb-mode",
        tmm_reg,
        to_string,
        to_vec,
        tool_attributes,
        tool_lints,
        trace_macros,
        track_caller,
        trait_alias,
        trait_ty,
        trait_upcasting,
        transmute,
        transmute_generic_consts,
        transmute_opts,
        transmute_trait,
        transmute_unchecked,
        transparent,
        transparent_enums,
        transparent_unions,
        trivial_bounds,
        trivial_clone,
        truncf16,
        truncf32,
        truncf64,
        truncf128,
        try_blocks,
        try_blocks_heterogeneous,
        try_capture,
        try_from,
        try_into,
        try_trait_v2,
        try_trait_v2_residual,
        try_update,
        tt,
        tuple,
        tuple_indexing,
        tuple_trait,
        two_phase,
        ty,
        type_alias_enum_variants,
        type_alias_impl_trait,
        type_ascribe,
        type_ascription,
        type_changing_struct_update,
        type_id,
        type_id_eq,
        type_id_vtable,
        type_info,
        type_ir,
        type_ir_infer_ctxt_like,
        type_ir_inherent,
        type_ir_interner,
        type_length_limit,
        type_macros,
        type_name,
        type_of,
        type_privacy_lints,
        typed_swap_nonoverlapping,
        u8,
        u8_legacy_const_max,
        u8_legacy_const_min,
        u8_legacy_fn_max_value,
        u8_legacy_fn_min_value,
        u8_legacy_mod,
        u16,
        u16_legacy_const_max,
        u16_legacy_const_min,
        u16_legacy_fn_max_value,
        u16_legacy_fn_min_value,
        u16_legacy_mod,
        u32,
        u32_legacy_const_max,
        u32_legacy_const_min,
        u32_legacy_fn_max_value,
        u32_legacy_fn_min_value,
        u32_legacy_mod,
        u64,
        u64_legacy_const_max,
        u64_legacy_const_min,
        u64_legacy_fn_max_value,
        u64_legacy_fn_min_value,
        u64_legacy_mod,
        u128,
        u128_legacy_const_max,
        u128_legacy_const_min,
        u128_legacy_fn_max_value,
        u128_legacy_fn_min_value,
        u128_legacy_mod,
        ub_checks,
        unaligned_volatile_load,
        unaligned_volatile_store,
        unboxed_closures,
        unchecked_add,
        unchecked_div,
        unchecked_funnel_shl,
        unchecked_funnel_shr,
        unchecked_mul,
        unchecked_rem,
        unchecked_shl,
        unchecked_shr,
        unchecked_sub,
        undecorated,
        underscore_const_names,
        underscore_imports,
        underscore_lifetimes,
        uniform_paths,
        unit,
        universal_impl_trait,
        unix,
        unlikely,
        unmarked_api,
        unnamed_fields,
        unpin,
        unqualified_local_imports,
        unreachable,
        unreachable_2015,
        unreachable_2015_macro,
        unreachable_2021,
        unreachable_code,
        unreachable_display,
        unreachable_macro,
        unrestricted_attribute_tokens,
        unsafe_attributes,
        unsafe_binders,
        unsafe_block_in_unsafe_fn,
        unsafe_cell,
        unsafe_cell_raw_get,
        unsafe_eii,
        unsafe_extern_blocks,
        unsafe_fields,
        unsafe_no_drop_flag,
        unsafe_pinned,
        unsafe_unpin,
        unsafety,
        unsize,
        unsized_const_param_ty,
        unsized_const_params,
        unsized_fn_params,
        unsized_locals,
        unsized_tuple_coercion,
        unstable,
        unstable_feature_bound,
        unstable_location_reason_default: "this crate is being loaded from the sysroot, an \
                          unstable location; did you mean to load this crate \
                          from crates.io via `Cargo.toml` instead?",
        untagged_unions,
        unused_imports,
        unwind,
        unwind_attributes,
        unwind_safe_trait,
        unwrap,
        unwrap_binder,
        unwrap_or,
        update,
        use_cloned,
        use_extern_macros,
        use_nested_groups,
        used,
        used_with_arg,
        using,
        usize,
        usize_legacy_const_max,
        usize_legacy_const_min,
        usize_legacy_fn_max_value,
        usize_legacy_fn_min_value,
        usize_legacy_mod,
        v1,
        v8plus,
        va_arg,
        va_copy,
        va_end,
        va_list,
        va_start,
        val,
        validity,
        value,
        values,
        var,
        variadic,
        variant_count,
        variants,
        vec,
        vector,
        verbatim,
        version,
        vfp2,
        vis,
        visible_private_types,
        volatile,
        volatile_copy_memory,
        volatile_copy_nonoverlapping_memory,
        volatile_load,
        volatile_set_memory,
        volatile_store,
        vreg,
        vreg_low16,
        vsreg,
        vsx,
        vtable_align,
        vtable_size,
        warn,
        wasip2,
        wasm32,
        wasm64,
        wasm_abi,
        wasm_import_module,
        wasm_target_feature,
        weak,
        weak_odr,
        where_clause_attrs,
        while_let,
        whole_dash_archive: "whole-archive",
        width,
        windows,
        windows_subsystem,
        with_negative_coherence,
        wrap_binder,
        wrapping_add,
        wrapping_div,
        wrapping_mul,
        wrapping_rem,
        wrapping_rem_euclid,
        wrapping_sub,
        wreg,
        write_box_via_move,
        write_bytes,
        write_fmt,
        write_macro,
        write_str,
        write_via_move,
        writeln_macro,
        x86,
        x86_64,
        x86_amx_intrinsics,
        x87_reg,
        x87_target_feature,
        xer,
        xmm_reg,
        xop_target_feature,
        xtensa,
        yeet_desugar_details,
        yeet_expr,
        yes,
        yield_expr,
        ymm_reg,
        yreg,
        zca,
        zfh,
        zfhmin,
        zmm_reg,
        ztso,
        // tidy-alphabetical-end
    }
}

/// Symbols for crates that are part of the stable standard library: `std`, `core`, `alloc`, and
/// `proc_macro`.
pub const STDLIB_STABLE_CRATES: &[Symbol] = &[sym::std, sym::core, sym::alloc, sym::proc_macro];

#[derive(Copy, Clone, Eq, HashStable_Generic, Encodable, Decodable)]
pub struct Ident {
    /// `name` should never be the empty symbol. If you are considering that,
    /// you are probably conflating "empty identifier with "no identifier" and
    /// you should use `Option<Ident>` instead.
    /// Trying to construct an `Ident` with an empty name will trigger debug assertions.
    pub name: Symbol,
    pub span: Span,
}

impl Ident {
    #[inline]
    /// Constructs a new identifier from a symbol and a span.
    pub fn new(name: Symbol, span: Span) -> Ident {
        debug_assert_ne!(name, sym::empty);
        Ident { name, span }
    }

    /// Constructs a new identifier with a dummy span.
    #[inline]
    pub fn with_dummy_span(name: Symbol) -> Ident {
        Ident::new(name, DUMMY_SP)
    }

    // For dummy identifiers that are never used and absolutely must be
    // present. Note that this does *not* use the empty symbol; `sym::dummy`
    // makes it clear that it's intended as a dummy value, and is more likely
    // to be detected if it accidentally does get used.
    #[inline]
    pub fn dummy() -> Ident {
        Ident::with_dummy_span(sym::dummy)
    }

    /// Maps a string to an identifier with a dummy span.
    pub fn from_str(string: &str) -> Ident {
        Ident::with_dummy_span(Symbol::intern(string))
    }

    /// Maps a string and a span to an identifier.
    pub fn from_str_and_span(string: &str, span: Span) -> Ident {
        Ident::new(Symbol::intern(string), span)
    }

    /// Replaces `lo` and `hi` with those from `span`, but keep hygiene context.
    pub fn with_span_pos(self, span: Span) -> Ident {
        Ident::new(self.name, span.with_ctxt(self.span.ctxt()))
    }

    /// Creates a new ident with the same span and name with leading quote removed, if any.
    /// Calling it on a `'` ident will return an empty ident, which triggers debug assertions.
    pub fn without_first_quote(self) -> Ident {
        self.as_str()
            .strip_prefix('\'')
            .map_or(self, |name| Ident::new(Symbol::intern(name), self.span))
    }

    /// "Normalize" ident for use in comparisons using "item hygiene".
    /// Identifiers with same string value become same if they came from the same macro 2.0 macro
    /// (e.g., `macro` item, but not `macro_rules` item) and stay different if they came from
    /// different macro 2.0 macros.
    /// Technically, this operation strips all non-opaque marks from ident's syntactic context.
    pub fn normalize_to_macros_2_0(self) -> Ident {
        Ident::new(self.name, self.span.normalize_to_macros_2_0())
    }

    /// "Normalize" ident for use in comparisons using "local variable hygiene".
    /// Identifiers with same string value become same if they came from the same non-transparent
    /// macro (e.g., `macro` or `macro_rules!` items) and stay different if they came from different
    /// non-transparent macros.
    /// Technically, this operation strips all transparent marks from ident's syntactic context.
    #[inline]
    pub fn normalize_to_macro_rules(self) -> Ident {
        Ident::new(self.name, self.span.normalize_to_macro_rules())
    }

    /// Access the underlying string. This is a slowish operation because it
    /// requires locking the symbol interner.
    ///
    /// Note that the lifetime of the return value is a lie. See
    /// `Symbol::as_str()` for details.
    pub fn as_str(&self) -> &str {
        self.name.as_str()
    }
}

impl PartialEq for Ident {
    #[inline]
    fn eq(&self, rhs: &Self) -> bool {
        self.name == rhs.name && self.span.eq_ctxt(rhs.span)
    }
}

impl Hash for Ident {
    fn hash<H: Hasher>(&self, state: &mut H) {
        self.name.hash(state);
        self.span.ctxt().hash(state);
    }
}

impl fmt::Debug for Ident {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        fmt::Display::fmt(self, f)?;
        fmt::Debug::fmt(&self.span.ctxt(), f)
    }
}

/// This implementation is supposed to be used in error messages, so it's expected to be identical
/// to printing the original identifier token written in source code (`token_to_string`),
/// except that AST identifiers don't keep the rawness flag, so we have to guess it.
impl fmt::Display for Ident {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        fmt::Display::fmt(&IdentPrinter::new(self.name, self.guess_print_mode(), None), f)
    }
}

pub enum IdentPrintMode {
    Normal,
    RawIdent,
    RawLifetime,
}

/// The most general type to print identifiers.
///
/// AST pretty-printer is used as a fallback for turning AST structures into token streams for
/// proc macros. Additionally, proc macros may stringify their input and expect it survive the
/// stringification (especially true for proc macro derives written between Rust 1.15 and 1.30).
/// So we need to somehow pretty-print `$crate` in a way preserving at least some of its
/// hygiene data, most importantly name of the crate it refers to.
/// As a result we print `$crate` as `crate` if it refers to the local crate
/// and as `::other_crate_name` if it refers to some other crate.
/// Note, that this is only done if the ident token is printed from inside of AST pretty-printing,
/// but not otherwise. Pretty-printing is the only way for proc macros to discover token contents,
/// so we should not perform this lossy conversion if the top level call to the pretty-printer was
/// done for a token stream or a single token.
pub struct IdentPrinter {
    symbol: Symbol,
    mode: IdentPrintMode,
    /// Span used for retrieving the crate name to which `$crate` refers to,
    /// if this field is `None` then the `$crate` conversion doesn't happen.
    convert_dollar_crate: Option<Span>,
}

impl IdentPrinter {
    /// The most general `IdentPrinter` constructor. Do not use this.
    pub fn new(
        symbol: Symbol,
        mode: IdentPrintMode,
        convert_dollar_crate: Option<Span>,
    ) -> IdentPrinter {
        IdentPrinter { symbol, mode, convert_dollar_crate }
    }

    /// This implementation is supposed to be used when printing identifiers
    /// as a part of pretty-printing for larger AST pieces.
    /// Do not use this either.
    pub fn for_ast_ident(ident: Ident, mode: IdentPrintMode) -> IdentPrinter {
        IdentPrinter::new(ident.name, mode, Some(ident.span))
    }
}

impl fmt::Display for IdentPrinter {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        let s = match self.mode {
            IdentPrintMode::Normal
                if self.symbol == kw::DollarCrate
                    && let Some(span) = self.convert_dollar_crate =>
            {
                let converted = span.ctxt().dollar_crate_name();
                if !converted.is_path_segment_keyword() {
                    f.write_str("::")?;
                }
                converted
            }
            IdentPrintMode::Normal => self.symbol,
            IdentPrintMode::RawIdent => {
                f.write_str("r#")?;
                self.symbol
            }
            IdentPrintMode::RawLifetime => {
                f.write_str("'r#")?;
                let s = self
                    .symbol
                    .as_str()
                    .strip_prefix("'")
                    .expect("only lifetime idents should be passed with RawLifetime mode");
                Symbol::intern(s)
            }
        };
        s.fmt(f)
    }
}

/// A newtype around `Ident` that calls [Ident::normalize_to_macro_rules] on
/// construction for "local variable hygiene" comparisons.
///
/// Use this type when you need to compare identifiers according to macro_rules hygiene.
/// This ensures compile-time safety and avoids manual normalization calls.
#[derive(Copy, Clone, Eq, PartialEq, Hash)]
pub struct MacroRulesNormalizedIdent(Ident);

impl MacroRulesNormalizedIdent {
    #[inline]
    pub fn new(ident: Ident) -> Self {
        MacroRulesNormalizedIdent(ident.normalize_to_macro_rules())
    }

    pub fn symbol(&self) -> Symbol {
        self.0.name
    }

    pub fn ident(&self) -> Ident {
        self.0
    }
}

impl fmt::Debug for MacroRulesNormalizedIdent {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        fmt::Debug::fmt(&self.0, f)
    }
}

impl fmt::Display for MacroRulesNormalizedIdent {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        fmt::Display::fmt(&self.0, f)
    }
}

/// An interned UTF-8 string.
///
/// Internally, a `Symbol` is implemented as an index, and all operations
/// (including hashing, equality, and ordering) operate on that index. The use
/// of `rustc_index::newtype_index!` means that `Option<Symbol>` only takes up 4 bytes,
/// because `rustc_index::newtype_index!` reserves the last 256 values for tagging purposes.
///
/// Note that `Symbol` cannot directly be a `rustc_index::newtype_index!` because it
/// implements `fmt::Debug`, `Encodable`, and `Decodable` in special ways.
#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct Symbol(SymbolIndex);

// Used within both `Symbol` and `ByteSymbol`.
rustc_index::newtype_index! {
    #[orderable]
    struct SymbolIndex {}
}

impl Symbol {
    /// Avoid this except for things like deserialization of previously
    /// serialized symbols, and testing. Use `intern` instead.
    pub const fn new(n: u32) -> Self {
        Symbol(SymbolIndex::from_u32(n))
    }

    /// Maps a string to its interned representation.
    #[rustc_diagnostic_item = "SymbolIntern"]
    pub fn intern(str: &str) -> Self {
        with_session_globals(|session_globals| session_globals.symbol_interner.intern_str(str))
    }

    /// Access the underlying string. This is a slowish operation because it
    /// requires locking the symbol interner.
    ///
    /// Note that the lifetime of the return value is a lie. It's not the same
    /// as `&self`, but actually tied to the lifetime of the underlying
    /// interner. Interners are long-lived, and there are very few of them, and
    /// this function is typically used for short-lived things, so in practice
    /// it works out ok.
    pub fn as_str(&self) -> &str {
        with_session_globals(|session_globals| unsafe {
            std::mem::transmute::<&str, &str>(session_globals.symbol_interner.get_str(*self))
        })
    }

    pub fn as_u32(self) -> u32 {
        self.0.as_u32()
    }

    pub fn is_empty(self) -> bool {
        self == sym::empty
    }

    /// This method is supposed to be used in error messages, so it's expected to be
    /// identical to printing the original identifier token written in source code
    /// (`token_to_string`, `Ident::to_string`), except that symbols don't keep the rawness flag
    /// or edition, so we have to guess the rawness using the global edition.
    pub fn to_ident_string(self) -> String {
        // Avoid creating an empty identifier, because that asserts in debug builds.
        if self == sym::empty { String::new() } else { Ident::with_dummy_span(self).to_string() }
    }

    /// Checks if `self` is similar to any symbol in `candidates`.
    ///
    /// The returned boolean represents whether the candidate is the same symbol with a different
    /// casing.
    ///
    /// All the candidates are assumed to be lowercase.
    pub fn find_similar(
        self,
        candidates: &[Symbol],
    ) -> Option<(Symbol, /* is incorrect case */ bool)> {
        let lowercase = self.as_str().to_lowercase();
        let lowercase_sym = Symbol::intern(&lowercase);
        if candidates.contains(&lowercase_sym) {
            Some((lowercase_sym, true))
        } else if let Some(similar_sym) = find_best_match_for_name(candidates, self, None) {
            Some((similar_sym, false))
        } else {
            None
        }
    }
}

impl fmt::Debug for Symbol {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        fmt::Debug::fmt(self.as_str(), f)
    }
}

impl fmt::Display for Symbol {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        fmt::Display::fmt(self.as_str(), f)
    }
}

impl<CTX> HashStable<CTX> for Symbol {
    #[inline]
    fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
        self.as_str().hash_stable(hcx, hasher);
    }
}

impl<CTX> ToStableHashKey<CTX> for Symbol {
    type KeyType = String;
    #[inline]
    fn to_stable_hash_key(&self, _: &CTX) -> String {
        self.as_str().to_string()
    }
}

impl StableCompare for Symbol {
    const CAN_USE_UNSTABLE_SORT: bool = true;

    fn stable_cmp(&self, other: &Self) -> std::cmp::Ordering {
        self.as_str().cmp(other.as_str())
    }
}

/// Like `Symbol`, but for byte strings. `ByteSymbol` is used less widely, so
/// it has fewer operations defined than `Symbol`.
#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct ByteSymbol(SymbolIndex);

impl ByteSymbol {
    /// Avoid this except for things like deserialization of previously
    /// serialized symbols, and testing. Use `intern` instead.
    pub const fn new(n: u32) -> Self {
        ByteSymbol(SymbolIndex::from_u32(n))
    }

    /// Maps a string to its interned representation.
    pub fn intern(byte_str: &[u8]) -> Self {
        with_session_globals(|session_globals| {
            session_globals.symbol_interner.intern_byte_str(byte_str)
        })
    }

    /// Like `Symbol::as_str`.
    pub fn as_byte_str(&self) -> &[u8] {
        with_session_globals(|session_globals| unsafe {
            std::mem::transmute::<&[u8], &[u8]>(session_globals.symbol_interner.get_byte_str(*self))
        })
    }

    pub fn as_u32(self) -> u32 {
        self.0.as_u32()
    }
}

impl fmt::Debug for ByteSymbol {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        fmt::Debug::fmt(self.as_byte_str(), f)
    }
}

impl<CTX> HashStable<CTX> for ByteSymbol {
    #[inline]
    fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
        self.as_byte_str().hash_stable(hcx, hasher);
    }
}

// Interner used for both `Symbol`s and `ByteSymbol`s. If a string and a byte
// string with identical contents (e.g. "foo" and b"foo") are both interned,
// only one copy will be stored and the resulting `Symbol` and `ByteSymbol`
// will have the same index.
pub(crate) struct Interner(Lock<InternerInner>);

// The `&'static [u8]`s in this type actually point into the arena.
//
// This type is private to prevent accidentally constructing more than one
// `Interner` on the same thread, which makes it easy to mix up `Symbol`s
// between `Interner`s.
struct InternerInner {
    arena: DroplessArena,
    byte_strs: FxIndexSet<&'static [u8]>,
}

impl Interner {
    // These arguments are `&str`, but because of the sharing, we are
    // effectively pre-interning all these strings for both `Symbol` and
    // `ByteSymbol`.
    fn prefill(init: &[&'static str], extra: &[&'static str]) -> Self {
        let byte_strs = FxIndexSet::from_iter(
            init.iter().copied().chain(extra.iter().copied()).map(|str| str.as_bytes()),
        );

        // The order in which duplicates are reported is irrelevant.
        #[expect(rustc::potential_query_instability)]
        if byte_strs.len() != init.len() + extra.len() {
            panic!(
                "duplicate symbols in the rustc symbol list and the extra symbols added by the driver: {:?}",
                FxHashSet::intersection(
                    &init.iter().copied().collect(),
                    &extra.iter().copied().collect(),
                )
                .collect::<Vec<_>>()
            )
        }

        Interner(Lock::new(InternerInner { arena: Default::default(), byte_strs }))
    }

    fn intern_str(&self, str: &str) -> Symbol {
        Symbol::new(self.intern_inner(str.as_bytes()))
    }

    fn intern_byte_str(&self, byte_str: &[u8]) -> ByteSymbol {
        ByteSymbol::new(self.intern_inner(byte_str))
    }

    #[inline]
    fn intern_inner(&self, byte_str: &[u8]) -> u32 {
        let mut inner = self.0.lock();
        if let Some(idx) = inner.byte_strs.get_index_of(byte_str) {
            return idx as u32;
        }

        let byte_str: &[u8] = inner.arena.alloc_slice(byte_str);

        // SAFETY: we can extend the arena allocation to `'static` because we
        // only access these while the arena is still alive.
        let byte_str: &'static [u8] = unsafe { &*(byte_str as *const [u8]) };

        // This second hash table lookup can be avoided by using `RawEntryMut`,
        // but this code path isn't hot enough for it to be worth it. See
        // #91445 for details.
        let (idx, is_new) = inner.byte_strs.insert_full(byte_str);
        debug_assert!(is_new); // due to the get_index_of check above

        idx as u32
    }

    /// Get the symbol as a string.
    ///
    /// [`Symbol::as_str()`] should be used in preference to this function.
    fn get_str(&self, symbol: Symbol) -> &str {
        let byte_str = self.get_inner(symbol.0.as_usize());
        // SAFETY: known to be a UTF8 string because it's a `Symbol`.
        unsafe { str::from_utf8_unchecked(byte_str) }
    }

    /// Get the symbol as a string.
    ///
    /// [`ByteSymbol::as_byte_str()`] should be used in preference to this function.
    fn get_byte_str(&self, symbol: ByteSymbol) -> &[u8] {
        self.get_inner(symbol.0.as_usize())
    }

    fn get_inner(&self, index: usize) -> &[u8] {
        self.0.lock().byte_strs.get_index(index).unwrap()
    }
}

// This module has a very short name because it's used a lot.
/// This module contains all the defined keyword `Symbol`s.
///
/// Given that `kw` is imported, use them like `kw::keyword_name`.
/// For example `kw::Loop` or `kw::Break`.
pub mod kw {
    pub use super::kw_generated::*;
}

// This module has a very short name because it's used a lot.
/// This module contains all the defined non-keyword `Symbol`s.
///
/// Given that `sym` is imported, use them like `sym::symbol_name`.
/// For example `sym::rustfmt` or `sym::u8`.
pub mod sym {
    // Used from a macro in `librustc_feature/accepted.rs`
    use super::Symbol;
    pub use super::kw::MacroRules as macro_rules;
    #[doc(inline)]
    pub use super::sym_generated::*;

    /// Get the symbol for an integer.
    ///
    /// The first few non-negative integers each have a static symbol and therefore
    /// are fast.
    pub fn integer<N: TryInto<usize> + Copy + itoa::Integer>(n: N) -> Symbol {
        if let Result::Ok(idx) = n.try_into() {
            if idx < 10 {
                return Symbol::new(super::SYMBOL_DIGITS_BASE + idx as u32);
            }
        }
        let mut buffer = itoa::Buffer::new();
        let printed = buffer.format(n);
        Symbol::intern(printed)
    }
}

impl Symbol {
    fn is_special(self) -> bool {
        self <= kw::Underscore
    }

    fn is_used_keyword_always(self) -> bool {
        self >= kw::As && self <= kw::While
    }

    fn is_unused_keyword_always(self) -> bool {
        self >= kw::Abstract && self <= kw::Yield
    }

    fn is_used_keyword_conditional(self, edition: impl FnOnce() -> Edition) -> bool {
        (self >= kw::Async && self <= kw::Dyn) && edition() >= Edition::Edition2018
    }

    fn is_unused_keyword_conditional(self, edition: impl Copy + FnOnce() -> Edition) -> bool {
        self == kw::Gen && edition().at_least_rust_2024()
            || self == kw::Try && edition().at_least_rust_2018()
    }

    pub fn is_reserved(self, edition: impl Copy + FnOnce() -> Edition) -> bool {
        self.is_special()
            || self.is_used_keyword_always()
            || self.is_unused_keyword_always()
            || self.is_used_keyword_conditional(edition)
            || self.is_unused_keyword_conditional(edition)
    }

    pub fn is_weak(self) -> bool {
        self >= kw::Auto && self <= kw::Yeet
    }

    /// A keyword or reserved identifier that can be used as a path segment.
    pub fn is_path_segment_keyword(self) -> bool {
        self == kw::Super
            || self == kw::SelfLower
            || self == kw::SelfUpper
            || self == kw::Crate
            || self == kw::PathRoot
            || self == kw::DollarCrate
    }

    /// Returns `true` if the symbol is `true` or `false`.
    pub fn is_bool_lit(self) -> bool {
        self == kw::True || self == kw::False
    }

    /// Returns `true` if this symbol can be a raw identifier.
    pub fn can_be_raw(self) -> bool {
        self != sym::empty && self != kw::Underscore && !self.is_path_segment_keyword()
    }

    /// Was this symbol index predefined in the compiler's `symbols!` macro?
    /// Note: this applies to both `Symbol`s and `ByteSymbol`s, which is why it
    /// takes a `u32` argument instead of a `&self` argument. Use with care.
    pub fn is_predefined(index: u32) -> bool {
        index < PREDEFINED_SYMBOLS_COUNT
    }
}

impl Ident {
    /// Returns `true` for reserved identifiers used internally for elided lifetimes,
    /// unnamed method parameters, crate root module, error recovery etc.
    pub fn is_special(self) -> bool {
        self.name.is_special()
    }

    /// Returns `true` if the token is a keyword used in the language.
    pub fn is_used_keyword(self) -> bool {
        // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
        self.name.is_used_keyword_always()
            || self.name.is_used_keyword_conditional(|| self.span.edition())
    }

    /// Returns `true` if the token is a keyword reserved for possible future use.
    pub fn is_unused_keyword(self) -> bool {
        // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
        self.name.is_unused_keyword_always()
            || self.name.is_unused_keyword_conditional(|| self.span.edition())
    }

    /// Returns `true` if the token is either a special identifier or a keyword.
    pub fn is_reserved(self) -> bool {
        // Note: `span.edition()` is relatively expensive, don't call it unless necessary.
        self.name.is_reserved(|| self.span.edition())
    }

    /// A keyword or reserved identifier that can be used as a path segment.
    pub fn is_path_segment_keyword(self) -> bool {
        self.name.is_path_segment_keyword()
    }

    /// We see this identifier in a normal identifier position, like variable name or a type.
    /// How was it written originally? Did it use the raw form? Let's try to guess.
    pub fn is_raw_guess(self) -> bool {
        self.name.can_be_raw() && self.is_reserved()
    }

    /// Given the name of a lifetime without the first quote (`'`),
    /// returns whether the lifetime name is reserved (therefore invalid)
    pub fn is_reserved_lifetime(self) -> bool {
        self.is_reserved() && ![kw::Underscore, kw::Static].contains(&self.name)
    }

    pub fn is_raw_lifetime_guess(self) -> bool {
        // Check that the name isn't just a single quote.
        // `self.without_first_quote()` would return empty ident, which triggers debug assert.
        if self.name.as_str() == "'" {
            return false;
        }
        let ident_without_apostrophe = self.without_first_quote();
        ident_without_apostrophe.name != self.name
            && ident_without_apostrophe.name.can_be_raw()
            && ident_without_apostrophe.is_reserved_lifetime()
    }

    pub fn guess_print_mode(self) -> IdentPrintMode {
        if self.is_raw_lifetime_guess() {
            IdentPrintMode::RawLifetime
        } else if self.is_raw_guess() {
            IdentPrintMode::RawIdent
        } else {
            IdentPrintMode::Normal
        }
    }

    /// Whether this would be the identifier for a tuple field like `self.0`, as
    /// opposed to a named field like `self.thing`.
    pub fn is_numeric(self) -> bool {
        self.as_str().bytes().all(|b| b.is_ascii_digit())
    }
}

/// Collect all the keywords in a given edition into a vector.
///
/// *Note:* Please update this if a new keyword is added beyond the current
/// range.
pub fn used_keywords(edition: impl Copy + FnOnce() -> Edition) -> Vec<Symbol> {
    (kw::DollarCrate.as_u32()..kw::Yeet.as_u32())
        .filter_map(|kw| {
            let kw = Symbol::new(kw);
            if kw.is_used_keyword_always() || kw.is_used_keyword_conditional(edition) {
                Some(kw)
            } else {
                None
            }
        })
        .collect()
}
