rustc_metadata/rmeta/decoder/
cstore_impl.rs

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
use std::any::Any;
use std::mem;

use rustc_attr_parsing::Deprecation;
use rustc_data_structures::sync::Lrc;
use rustc_hir::def::{CtorKind, DefKind, Res};
use rustc_hir::def_id::{CrateNum, DefId, DefIdMap, LOCAL_CRATE};
use rustc_hir::definitions::{DefKey, DefPath, DefPathHash};
use rustc_middle::arena::ArenaAllocatable;
use rustc_middle::bug;
use rustc_middle::metadata::ModChild;
use rustc_middle::middle::exported_symbols::ExportedSymbol;
use rustc_middle::middle::stability::DeprecationEntry;
use rustc_middle::query::{ExternProviders, LocalCrate};
use rustc_middle::ty::fast_reject::SimplifiedType;
use rustc_middle::ty::{self, TyCtxt};
use rustc_middle::util::Providers;
use rustc_session::cstore::{CrateStore, ExternCrate};
use rustc_session::{Session, StableCrateId};
use rustc_span::hygiene::ExpnId;
use rustc_span::{Span, Symbol, kw};

use super::{Decodable, DecodeContext, DecodeIterator};
use crate::creader::{CStore, LoadedMacro};
use crate::rmeta::AttrFlags;
use crate::rmeta::table::IsDefault;
use crate::{foreign_modules, native_libs};

trait ProcessQueryValue<'tcx, T> {
    fn process_decoded(self, _tcx: TyCtxt<'tcx>, _err: impl Fn() -> !) -> T;
}

impl<T> ProcessQueryValue<'_, T> for T {
    #[inline(always)]
    fn process_decoded(self, _tcx: TyCtxt<'_>, _err: impl Fn() -> !) -> T {
        self
    }
}

impl<'tcx, T> ProcessQueryValue<'tcx, ty::EarlyBinder<'tcx, T>> for T {
    #[inline(always)]
    fn process_decoded(self, _tcx: TyCtxt<'_>, _err: impl Fn() -> !) -> ty::EarlyBinder<'tcx, T> {
        ty::EarlyBinder::bind(self)
    }
}

impl<T> ProcessQueryValue<'_, T> for Option<T> {
    #[inline(always)]
    fn process_decoded(self, _tcx: TyCtxt<'_>, err: impl Fn() -> !) -> T {
        if let Some(value) = self { value } else { err() }
    }
}

impl<'tcx, T: ArenaAllocatable<'tcx>> ProcessQueryValue<'tcx, &'tcx T> for Option<T> {
    #[inline(always)]
    fn process_decoded(self, tcx: TyCtxt<'tcx>, err: impl Fn() -> !) -> &'tcx T {
        if let Some(value) = self { tcx.arena.alloc(value) } else { err() }
    }
}

impl<T, E> ProcessQueryValue<'_, Result<Option<T>, E>> for Option<T> {
    #[inline(always)]
    fn process_decoded(self, _tcx: TyCtxt<'_>, _err: impl Fn() -> !) -> Result<Option<T>, E> {
        Ok(self)
    }
}

impl<'a, 'tcx, T: Copy + Decodable<DecodeContext<'a, 'tcx>>> ProcessQueryValue<'tcx, &'tcx [T]>
    for Option<DecodeIterator<'a, 'tcx, T>>
{
    #[inline(always)]
    fn process_decoded(self, tcx: TyCtxt<'tcx>, err: impl Fn() -> !) -> &'tcx [T] {
        if let Some(iter) = self { tcx.arena.alloc_from_iter(iter) } else { err() }
    }
}

impl<'a, 'tcx, T: Copy + Decodable<DecodeContext<'a, 'tcx>>>
    ProcessQueryValue<'tcx, ty::EarlyBinder<'tcx, &'tcx [T]>>
    for Option<DecodeIterator<'a, 'tcx, T>>
{
    #[inline(always)]
    fn process_decoded(
        self,
        tcx: TyCtxt<'tcx>,
        err: impl Fn() -> !,
    ) -> ty::EarlyBinder<'tcx, &'tcx [T]> {
        ty::EarlyBinder::bind(if let Some(iter) = self {
            tcx.arena.alloc_from_iter(iter)
        } else {
            err()
        })
    }
}

impl<'a, 'tcx, T: Copy + Decodable<DecodeContext<'a, 'tcx>>>
    ProcessQueryValue<'tcx, Option<&'tcx [T]>> for Option<DecodeIterator<'a, 'tcx, T>>
{
    #[inline(always)]
    fn process_decoded(self, tcx: TyCtxt<'tcx>, _err: impl Fn() -> !) -> Option<&'tcx [T]> {
        if let Some(iter) = self { Some(&*tcx.arena.alloc_from_iter(iter)) } else { None }
    }
}

impl ProcessQueryValue<'_, Option<DeprecationEntry>> for Option<Deprecation> {
    #[inline(always)]
    fn process_decoded(self, _tcx: TyCtxt<'_>, _err: impl Fn() -> !) -> Option<DeprecationEntry> {
        self.map(DeprecationEntry::external)
    }
}

macro_rules! provide_one {
    ($tcx:ident, $def_id:ident, $other:ident, $cdata:ident, $name:ident => { table }) => {
        provide_one! {
            $tcx, $def_id, $other, $cdata, $name => {
                $cdata
                    .root
                    .tables
                    .$name
                    .get($cdata, $def_id.index)
                    .map(|lazy| lazy.decode(($cdata, $tcx)))
                    .process_decoded($tcx, || panic!("{:?} does not have a {:?}", $def_id, stringify!($name)))
            }
        }
    };
    ($tcx:ident, $def_id:ident, $other:ident, $cdata:ident, $name:ident => { table_defaulted_array }) => {
        provide_one! {
            $tcx, $def_id, $other, $cdata, $name => {
                let lazy = $cdata.root.tables.$name.get($cdata, $def_id.index);
                let value = if lazy.is_default() {
                    &[] as &[_]
                } else {
                    $tcx.arena.alloc_from_iter(lazy.decode(($cdata, $tcx)))
                };
                value.process_decoded($tcx, || panic!("{:?} does not have a {:?}", $def_id, stringify!($name)))
            }
        }
    };
    ($tcx:ident, $def_id:ident, $other:ident, $cdata:ident, $name:ident => { table_direct }) => {
        provide_one! {
            $tcx, $def_id, $other, $cdata, $name => {
                // We don't decode `table_direct`, since it's not a Lazy, but an actual value
                $cdata
                    .root
                    .tables
                    .$name
                    .get($cdata, $def_id.index)
                    .process_decoded($tcx, || panic!("{:?} does not have a {:?}", $def_id, stringify!($name)))
            }
        }
    };
    ($tcx:ident, $def_id:ident, $other:ident, $cdata:ident, $name:ident => $compute:block) => {
        fn $name<'tcx>(
            $tcx: TyCtxt<'tcx>,
            def_id_arg: rustc_middle::query::queries::$name::Key<'tcx>,
        ) -> rustc_middle::query::queries::$name::ProvidedValue<'tcx> {
            let _prof_timer =
                $tcx.prof.generic_activity(concat!("metadata_decode_entry_", stringify!($name)));

            #[allow(unused_variables)]
            let ($def_id, $other) = def_id_arg.into_args();
            assert!(!$def_id.is_local());

            // External query providers call `crate_hash` in order to register a dependency
            // on the crate metadata. The exception is `crate_hash` itself, which obviously
            // doesn't need to do this (and can't, as it would cause a query cycle).
            use rustc_middle::dep_graph::dep_kinds;
            if dep_kinds::$name != dep_kinds::crate_hash && $tcx.dep_graph.is_fully_enabled() {
                $tcx.ensure().crate_hash($def_id.krate);
            }

            let cdata = rustc_data_structures::sync::FreezeReadGuard::map(CStore::from_tcx($tcx), |c| {
                c.get_crate_data($def_id.krate).cdata
            });
            let $cdata = crate::creader::CrateMetadataRef {
                cdata: &cdata,
                cstore: &CStore::from_tcx($tcx),
            };

            $compute
        }
    };
}

macro_rules! provide {
    ($tcx:ident, $def_id:ident, $other:ident, $cdata:ident,
      $($name:ident => { $($compute:tt)* })*) => {
        fn provide_extern(providers: &mut ExternProviders) {
            $(provide_one! {
                $tcx, $def_id, $other, $cdata, $name => { $($compute)* }
            })*

            *providers = ExternProviders {
                $($name,)*
                ..*providers
            };
        }
    }
}

// small trait to work around different signature queries all being defined via
// the macro above.
trait IntoArgs {
    type Other;
    fn into_args(self) -> (DefId, Self::Other);
}

impl IntoArgs for DefId {
    type Other = ();
    fn into_args(self) -> (DefId, ()) {
        (self, ())
    }
}

impl IntoArgs for CrateNum {
    type Other = ();
    fn into_args(self) -> (DefId, ()) {
        (self.as_def_id(), ())
    }
}

impl IntoArgs for (CrateNum, DefId) {
    type Other = DefId;
    fn into_args(self) -> (DefId, DefId) {
        (self.0.as_def_id(), self.1)
    }
}

impl<'tcx> IntoArgs for ty::InstanceKind<'tcx> {
    type Other = ();
    fn into_args(self) -> (DefId, ()) {
        (self.def_id(), ())
    }
}

impl IntoArgs for (CrateNum, SimplifiedType) {
    type Other = SimplifiedType;
    fn into_args(self) -> (DefId, SimplifiedType) {
        (self.0.as_def_id(), self.1)
    }
}

provide! { tcx, def_id, other, cdata,
    explicit_item_bounds => { table_defaulted_array }
    explicit_item_super_predicates => { table_defaulted_array }
    explicit_predicates_of => { table }
    generics_of => { table }
    inferred_outlives_of => { table_defaulted_array }
    explicit_super_predicates_of => { table_defaulted_array }
    explicit_implied_predicates_of => { table_defaulted_array }
    type_of => { table }
    type_alias_is_lazy => { table_direct }
    variances_of => { table }
    fn_sig => { table }
    codegen_fn_attrs => { table }
    impl_trait_header => { table }
    const_param_default => { table }
    object_lifetime_default => { table }
    thir_abstract_const => { table }
    optimized_mir => { table }
    mir_for_ctfe => { table }
    closure_saved_names_of_captured_variables => { table }
    mir_coroutine_witnesses => { table }
    promoted_mir => { table }
    def_span => { table }
    def_ident_span => { table }
    lookup_stability => { table }
    lookup_const_stability => { table }
    lookup_default_body_stability => { table }
    lookup_deprecation_entry => { table }
    params_in_repr => { table }
    def_kind => { cdata.def_kind(def_id.index) }
    impl_parent => { table }
    defaultness => { table_direct }
    constness => { table_direct }
    const_conditions => { table }
    explicit_implied_const_bounds => { table_defaulted_array }
    coerce_unsized_info => {
        Ok(cdata
            .root
            .tables
            .coerce_unsized_info
            .get(cdata, def_id.index)
            .map(|lazy| lazy.decode((cdata, tcx)))
            .process_decoded(tcx, || panic!("{def_id:?} does not have coerce_unsized_info"))) }
    mir_const_qualif => { table }
    rendered_const => { table }
    rendered_precise_capturing_args => { table }
    asyncness => { table_direct }
    fn_arg_names => { table }
    coroutine_kind => { table_direct }
    coroutine_for_closure => { table }
    coroutine_by_move_body_def_id => { table }
    eval_static_initializer => {
        Ok(cdata
            .root
            .tables
            .eval_static_initializer
            .get(cdata, def_id.index)
            .map(|lazy| lazy.decode((cdata, tcx)))
            .unwrap_or_else(|| panic!("{def_id:?} does not have eval_static_initializer")))
    }
    trait_def => { table }
    deduced_param_attrs => {
        // FIXME: `deduced_param_attrs` has some sketchy encoding settings,
        // where we don't encode unless we're optimizing, doing codegen,
        // and not incremental (see `encoder.rs`). I don't think this is right!
        cdata
            .root
            .tables
            .deduced_param_attrs
            .get(cdata, def_id.index)
            .map(|lazy| {
                &*tcx.arena.alloc_from_iter(lazy.decode((cdata, tcx)))
            })
            .unwrap_or_default()
    }
    opaque_ty_origin => { table }
    assumed_wf_types_for_rpitit => { table }
    collect_return_position_impl_trait_in_trait_tys => {
        Ok(cdata
            .root
            .tables
            .trait_impl_trait_tys
            .get(cdata, def_id.index)
            .map(|lazy| lazy.decode((cdata, tcx)))
            .process_decoded(tcx, || panic!("{def_id:?} does not have trait_impl_trait_tys")))
    }

    associated_types_for_impl_traits_in_associated_fn => { table_defaulted_array }

    visibility => { cdata.get_visibility(def_id.index) }
    adt_def => { cdata.get_adt_def(def_id.index, tcx) }
    adt_destructor => {
        let _ = cdata;
        tcx.calculate_dtor(def_id, |_,_| Ok(()))
    }
    adt_async_destructor => {
        let _ = cdata;
        tcx.calculate_async_dtor(def_id, |_,_| Ok(()))
    }
    associated_item_def_ids => {
        tcx.arena.alloc_from_iter(cdata.get_associated_item_or_field_def_ids(def_id.index))
    }
    associated_item => { cdata.get_associated_item(def_id.index, tcx.sess) }
    inherent_impls => { cdata.get_inherent_implementations_for_type(tcx, def_id.index) }
    attrs_for_def => { tcx.arena.alloc_from_iter(cdata.get_item_attrs(def_id.index, tcx.sess)) }
    is_mir_available => { cdata.is_item_mir_available(def_id.index) }
    is_ctfe_mir_available => { cdata.is_ctfe_mir_available(def_id.index) }
    cross_crate_inlinable => { table_direct }

    dylib_dependency_formats => { cdata.get_dylib_dependency_formats(tcx) }
    is_private_dep => { cdata.private_dep }
    is_panic_runtime => { cdata.root.panic_runtime }
    is_compiler_builtins => { cdata.root.compiler_builtins }
    has_global_allocator => { cdata.root.has_global_allocator }
    has_alloc_error_handler => { cdata.root.has_alloc_error_handler }
    has_panic_handler => { cdata.root.has_panic_handler }
    is_profiler_runtime => { cdata.root.profiler_runtime }
    required_panic_strategy => { cdata.root.required_panic_strategy }
    panic_in_drop_strategy => { cdata.root.panic_in_drop_strategy }
    extern_crate => { cdata.extern_crate.map(|c| &*tcx.arena.alloc(c)) }
    is_no_builtins => { cdata.root.no_builtins }
    symbol_mangling_version => { cdata.root.symbol_mangling_version }
    specialization_enabled_in => { cdata.root.specialization_enabled_in }
    reachable_non_generics => {
        let reachable_non_generics = tcx
            .exported_symbols(cdata.cnum)
            .iter()
            .filter_map(|&(exported_symbol, export_info)| {
                if let ExportedSymbol::NonGeneric(def_id) = exported_symbol {
                    Some((def_id, export_info))
                } else {
                    None
                }
            })
            .collect();

        reachable_non_generics
    }
    native_libraries => { cdata.get_native_libraries(tcx.sess).collect() }
    foreign_modules => { cdata.get_foreign_modules(tcx.sess).map(|m| (m.def_id, m)).collect() }
    crate_hash => { cdata.root.header.hash }
    crate_host_hash => { cdata.host_hash }
    crate_name => { cdata.root.header.name }
    num_extern_def_ids => { cdata.num_def_ids() }

    extra_filename => { cdata.root.extra_filename.clone() }

    traits => { tcx.arena.alloc_from_iter(cdata.get_traits()) }
    trait_impls_in_crate => { tcx.arena.alloc_from_iter(cdata.get_trait_impls()) }
    implementations_of_trait => { cdata.get_implementations_of_trait(tcx, other) }
    crate_incoherent_impls => { cdata.get_incoherent_impls(tcx, other) }

    dep_kind => { cdata.dep_kind }
    module_children => {
        tcx.arena.alloc_from_iter(cdata.get_module_children(def_id.index, tcx.sess))
    }
    lib_features => { cdata.get_lib_features() }
    stability_implications => {
        cdata.get_stability_implications(tcx).iter().copied().collect()
    }
    stripped_cfg_items => { cdata.get_stripped_cfg_items(cdata.cnum, tcx) }
    intrinsic_raw => { cdata.get_intrinsic(def_id.index) }
    defined_lang_items => { cdata.get_lang_items(tcx) }
    diagnostic_items => { cdata.get_diagnostic_items() }
    missing_lang_items => { cdata.get_missing_lang_items(tcx) }

    missing_extern_crate_item => {
        matches!(cdata.extern_crate, Some(extern_crate) if !extern_crate.is_direct())
    }

    used_crate_source => { Lrc::clone(&cdata.source) }
    debugger_visualizers => { cdata.get_debugger_visualizers() }

    exported_symbols => {
        let syms = cdata.exported_symbols(tcx);

        // FIXME rust-lang/rust#64319, rust-lang/rust#64872: We want
        // to block export of generics from dylibs, but we must fix
        // rust-lang/rust#65890 before we can do that robustly.

        syms
    }

    crate_extern_paths => { cdata.source().paths().cloned().collect() }
    expn_that_defined => { cdata.get_expn_that_defined(def_id.index, tcx.sess) }
    is_doc_hidden => { cdata.get_attr_flags(def_id.index).contains(AttrFlags::IS_DOC_HIDDEN) }
    doc_link_resolutions => { tcx.arena.alloc(cdata.get_doc_link_resolutions(def_id.index)) }
    doc_link_traits_in_scope => {
        tcx.arena.alloc_from_iter(cdata.get_doc_link_traits_in_scope(def_id.index))
    }
}

pub(in crate::rmeta) fn provide(providers: &mut Providers) {
    provide_cstore_hooks(providers);
    providers.queries = rustc_middle::query::Providers {
        allocator_kind: |tcx, ()| CStore::from_tcx(tcx).allocator_kind(),
        alloc_error_handler_kind: |tcx, ()| CStore::from_tcx(tcx).alloc_error_handler_kind(),
        is_private_dep: |_tcx, LocalCrate| false,
        native_library: |tcx, id| {
            tcx.native_libraries(id.krate)
                .iter()
                .filter(|lib| native_libs::relevant_lib(tcx.sess, lib))
                .find(|lib| {
                    let Some(fm_id) = lib.foreign_module else {
                        return false;
                    };
                    let map = tcx.foreign_modules(id.krate);
                    map.get(&fm_id)
                        .expect("failed to find foreign module")
                        .foreign_items
                        .contains(&id)
                })
        },
        native_libraries: native_libs::collect,
        foreign_modules: foreign_modules::collect,

        // Returns a map from a sufficiently visible external item (i.e., an
        // external item that is visible from at least one local module) to a
        // sufficiently visible parent (considering modules that re-export the
        // external item to be parents).
        visible_parent_map: |tcx, ()| {
            use std::collections::hash_map::Entry;
            use std::collections::vec_deque::VecDeque;

            let mut visible_parent_map: DefIdMap<DefId> = Default::default();
            // This is a secondary visible_parent_map, storing the DefId of
            // parents that re-export the child as `_` or module parents
            // which are `#[doc(hidden)]`. Since we prefer paths that don't
            // do this, merge this map at the end, only if we're missing
            // keys from the former.
            // This is a rudimentary check that does not catch all cases,
            // just the easiest.
            let mut fallback_map: Vec<(DefId, DefId)> = Default::default();

            // Issue 46112: We want the map to prefer the shortest
            // paths when reporting the path to an item. Therefore we
            // build up the map via a breadth-first search (BFS),
            // which naturally yields minimal-length paths.
            //
            // Note that it needs to be a BFS over the whole forest of
            // crates, not just each individual crate; otherwise you
            // only get paths that are locally minimal with respect to
            // whatever crate we happened to encounter first in this
            // traversal, but not globally minimal across all crates.
            let bfs_queue = &mut VecDeque::new();

            for &cnum in tcx.crates(()) {
                // Ignore crates without a corresponding local `extern crate` item.
                if tcx.missing_extern_crate_item(cnum) {
                    continue;
                }

                bfs_queue.push_back(cnum.as_def_id());
            }

            let mut add_child = |bfs_queue: &mut VecDeque<_>, child: &ModChild, parent: DefId| {
                if !child.vis.is_public() {
                    return;
                }

                if let Some(def_id) = child.res.opt_def_id() {
                    if child.ident.name == kw::Underscore {
                        fallback_map.push((def_id, parent));
                        return;
                    }

                    if tcx.is_doc_hidden(parent) {
                        fallback_map.push((def_id, parent));
                        return;
                    }

                    match visible_parent_map.entry(def_id) {
                        Entry::Occupied(mut entry) => {
                            // If `child` is defined in crate `cnum`, ensure
                            // that it is mapped to a parent in `cnum`.
                            if def_id.is_local() && entry.get().is_local() {
                                entry.insert(parent);
                            }
                        }
                        Entry::Vacant(entry) => {
                            entry.insert(parent);
                            if matches!(
                                child.res,
                                Res::Def(DefKind::Mod | DefKind::Enum | DefKind::Trait, _)
                            ) {
                                bfs_queue.push_back(def_id);
                            }
                        }
                    }
                }
            };

            while let Some(def) = bfs_queue.pop_front() {
                for child in tcx.module_children(def).iter() {
                    add_child(bfs_queue, child, def);
                }
            }

            // Fill in any missing entries with the less preferable path.
            // If this path re-exports the child as `_`, we still use this
            // path in a diagnostic that suggests importing `::*`.

            for (child, parent) in fallback_map {
                visible_parent_map.entry(child).or_insert(parent);
            }

            visible_parent_map
        },

        dependency_formats: |tcx, ()| Lrc::new(crate::dependency_format::calculate(tcx)),
        has_global_allocator: |tcx, LocalCrate| CStore::from_tcx(tcx).has_global_allocator(),
        has_alloc_error_handler: |tcx, LocalCrate| CStore::from_tcx(tcx).has_alloc_error_handler(),
        postorder_cnums: |tcx, ()| {
            tcx.arena
                .alloc_slice(&CStore::from_tcx(tcx).crate_dependencies_in_postorder(LOCAL_CRATE))
        },
        crates: |tcx, ()| {
            // The list of loaded crates is now frozen in query cache,
            // so make sure cstore is not mutably accessed from here on.
            tcx.untracked().cstore.freeze();
            tcx.arena.alloc_from_iter(CStore::from_tcx(tcx).iter_crate_data().map(|(cnum, _)| cnum))
        },
        used_crates: |tcx, ()| {
            // The list of loaded crates is now frozen in query cache,
            // so make sure cstore is not mutably accessed from here on.
            tcx.untracked().cstore.freeze();
            tcx.arena.alloc_from_iter(
                CStore::from_tcx(tcx)
                    .iter_crate_data()
                    .filter_map(|(cnum, data)| data.used().then_some(cnum)),
            )
        },
        ..providers.queries
    };
    provide_extern(&mut providers.extern_queries);
}

impl CStore {
    pub fn ctor_untracked(&self, def: DefId) -> Option<(CtorKind, DefId)> {
        self.get_crate_data(def.krate).get_ctor(def.index)
    }

    pub fn load_macro_untracked(&self, id: DefId, tcx: TyCtxt<'_>) -> LoadedMacro {
        let sess = tcx.sess;
        let _prof_timer = sess.prof.generic_activity("metadata_load_macro");

        let data = self.get_crate_data(id.krate);
        if data.root.is_proc_macro_crate() {
            LoadedMacro::ProcMacro(data.load_proc_macro(id.index, tcx))
        } else {
            LoadedMacro::MacroDef {
                def: data.get_macro(id.index, sess),
                ident: data.item_ident(id.index, sess),
                attrs: data.get_item_attrs(id.index, sess).collect(),
                span: data.get_span(id.index, sess),
                edition: data.root.edition,
            }
        }
    }

    pub fn def_span_untracked(&self, def_id: DefId, sess: &Session) -> Span {
        self.get_crate_data(def_id.krate).get_span(def_id.index, sess)
    }

    pub fn def_kind_untracked(&self, def: DefId) -> DefKind {
        self.get_crate_data(def.krate).def_kind(def.index)
    }

    pub fn expn_that_defined_untracked(&self, def_id: DefId, sess: &Session) -> ExpnId {
        self.get_crate_data(def_id.krate).get_expn_that_defined(def_id.index, sess)
    }

    /// Only public-facing way to traverse all the definitions in a non-local crate.
    /// Critically useful for this third-party project: <https://github.com/hacspec/hacspec>.
    /// See <https://github.com/rust-lang/rust/pull/85889> for context.
    pub fn num_def_ids_untracked(&self, cnum: CrateNum) -> usize {
        self.get_crate_data(cnum).num_def_ids()
    }

    pub fn get_proc_macro_quoted_span_untracked(
        &self,
        cnum: CrateNum,
        id: usize,
        sess: &Session,
    ) -> Span {
        self.get_crate_data(cnum).get_proc_macro_quoted_span(id, sess)
    }

    pub fn set_used_recursively(&mut self, cnum: CrateNum) {
        let cmeta = self.get_crate_data_mut(cnum);
        if !cmeta.used {
            cmeta.used = true;
            let dependencies = mem::take(&mut cmeta.dependencies);
            for &dep_cnum in &dependencies {
                self.set_used_recursively(dep_cnum);
            }
            self.get_crate_data_mut(cnum).dependencies = dependencies;
        }
    }

    pub(crate) fn update_extern_crate(&mut self, cnum: CrateNum, extern_crate: ExternCrate) {
        let cmeta = self.get_crate_data_mut(cnum);
        if cmeta.update_extern_crate(extern_crate) {
            // Propagate the extern crate info to dependencies if it was updated.
            let extern_crate = ExternCrate { dependency_of: cnum, ..extern_crate };
            let dependencies = mem::take(&mut cmeta.dependencies);
            for &dep_cnum in &dependencies {
                self.update_extern_crate(dep_cnum, extern_crate);
            }
            self.get_crate_data_mut(cnum).dependencies = dependencies;
        }
    }
}

impl CrateStore for CStore {
    fn as_any(&self) -> &dyn Any {
        self
    }
    fn untracked_as_any(&mut self) -> &mut dyn Any {
        self
    }

    fn crate_name(&self, cnum: CrateNum) -> Symbol {
        self.get_crate_data(cnum).root.header.name
    }

    fn stable_crate_id(&self, cnum: CrateNum) -> StableCrateId {
        self.get_crate_data(cnum).root.stable_crate_id
    }

    /// Returns the `DefKey` for a given `DefId`. This indicates the
    /// parent `DefId` as well as some idea of what kind of data the
    /// `DefId` refers to.
    fn def_key(&self, def: DefId) -> DefKey {
        self.get_crate_data(def.krate).def_key(def.index)
    }

    fn def_path(&self, def: DefId) -> DefPath {
        self.get_crate_data(def.krate).def_path(def.index)
    }

    fn def_path_hash(&self, def: DefId) -> DefPathHash {
        self.get_crate_data(def.krate).def_path_hash(def.index)
    }
}

fn provide_cstore_hooks(providers: &mut Providers) {
    providers.hooks.def_path_hash_to_def_id_extern = |tcx, hash, stable_crate_id| {
        // If this is a DefPathHash from an upstream crate, let the CrateStore map
        // it to a DefId.
        let cstore = CStore::from_tcx(tcx.tcx);
        let cnum = *tcx
            .untracked()
            .stable_crate_ids
            .read()
            .get(&stable_crate_id)
            .unwrap_or_else(|| bug!("uninterned StableCrateId: {stable_crate_id:?}"));
        assert_ne!(cnum, LOCAL_CRATE);
        let def_index = cstore.get_crate_data(cnum).def_path_hash_to_def_index(hash);
        DefId { krate: cnum, index: def_index }
    };

    providers.hooks.expn_hash_to_expn_id = |tcx, cnum, index_guess, hash| {
        let cstore = CStore::from_tcx(tcx.tcx);
        cstore.get_crate_data(cnum).expn_hash_to_expn_id(tcx.sess, index_guess, hash)
    };
    providers.hooks.import_source_files = |tcx, cnum| {
        let cstore = CStore::from_tcx(tcx.tcx);
        let cdata = cstore.get_crate_data(cnum);
        for file_index in 0..cdata.root.source_map.size() {
            cdata.imported_source_file(file_index as u32, tcx.sess);
        }
    };
}