1 //! Trait Resolution. See the [rustc dev guide] for more information on how this works.
3 //! [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/traits/resolution.html
9 pub mod const_evaluatable;
11 pub mod error_reporting;
24 use crate::infer::outlives::env::OutlivesEnvironment;
25 use crate::infer::{InferCtxt, RegionckMode, TyCtxtInferExt};
26 use crate::traits::error_reporting::InferCtxtExt as _;
27 use crate::traits::query::evaluate_obligation::InferCtxtExt as _;
28 use rustc_errors::ErrorReported;
30 use rustc_hir::def_id::DefId;
31 use rustc_middle::ty::fold::TypeFoldable;
32 use rustc_middle::ty::subst::{InternalSubsts, SubstsRef};
33 use rustc_middle::ty::{
34 self, GenericParamDefKind, ToPredicate, Ty, TyCtxt, VtblEntry, WithConstness,
35 COMMON_VTABLE_ENTRIES,
37 use rustc_span::{sym, Span};
38 use smallvec::SmallVec;
41 use std::ops::ControlFlow;
43 pub use self::FulfillmentErrorCode::*;
44 pub use self::ImplSource::*;
45 pub use self::ObligationCauseCode::*;
46 pub use self::SelectionError::*;
48 pub use self::coherence::{add_placeholder_note, orphan_check, overlapping_impls};
49 pub use self::coherence::{OrphanCheckErr, OverlapResult};
50 pub use self::engine::TraitEngineExt;
51 pub use self::fulfill::{FulfillmentContext, PendingPredicateObligation};
52 pub use self::object_safety::astconv_object_safety_violations;
53 pub use self::object_safety::is_vtable_safe_method;
54 pub use self::object_safety::MethodViolationCode;
55 pub use self::object_safety::ObjectSafetyViolation;
56 pub use self::on_unimplemented::{OnUnimplementedDirective, OnUnimplementedNote};
57 pub use self::project::{normalize, normalize_projection_type, normalize_to};
58 pub use self::select::{EvaluationCache, SelectionCache, SelectionContext};
59 pub use self::select::{EvaluationResult, IntercrateAmbiguityCause, OverflowError};
60 pub use self::specialize::specialization_graph::FutureCompatOverlapError;
61 pub use self::specialize::specialization_graph::FutureCompatOverlapErrorKind;
62 pub use self::specialize::{specialization_graph, translate_substs, OverlapError};
63 pub use self::structural_match::search_for_structural_match_violation;
64 pub use self::structural_match::NonStructuralMatchTy;
65 pub use self::util::{elaborate_predicates, elaborate_trait_ref, elaborate_trait_refs};
66 pub use self::util::{expand_trait_aliases, TraitAliasExpander};
68 get_vtable_index_of_object_method, impl_item_is_final, predicate_for_trait_def, upcast_choices,
71 supertrait_def_ids, supertraits, transitive_bounds, transitive_bounds_that_define_assoc_type,
72 SupertraitDefIds, Supertraits,
75 pub use self::chalk_fulfill::FulfillmentContext as ChalkFulfillmentContext;
77 pub use rustc_infer::traits::*;
79 /// Whether to skip the leak check, as part of a future compatibility warning step.
80 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
81 pub enum SkipLeakCheck {
87 fn is_yes(self) -> bool {
88 self == SkipLeakCheck::Yes
92 /// The "default" for skip-leak-check corresponds to the current
93 /// behavior (do not skip the leak check) -- not the behavior we are
94 /// transitioning into.
95 impl Default for SkipLeakCheck {
96 fn default() -> Self {
101 /// The mode that trait queries run in.
102 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
103 pub enum TraitQueryMode {
104 /// Standard/un-canonicalized queries get accurate
105 /// spans etc. passed in and hence can do reasonable
106 /// error reporting on their own.
108 /// Canonicalized queries get dummy spans and hence
109 /// must generally propagate errors to
110 /// pre-canonicalization callsites.
114 /// Creates predicate obligations from the generic bounds.
115 pub fn predicates_for_generics<'tcx>(
116 cause: ObligationCause<'tcx>,
117 param_env: ty::ParamEnv<'tcx>,
118 generic_bounds: ty::InstantiatedPredicates<'tcx>,
119 ) -> impl Iterator<Item = PredicateObligation<'tcx>> {
120 util::predicates_for_generics(cause, 0, param_env, generic_bounds)
123 /// Determines whether the type `ty` is known to meet `bound` and
124 /// returns true if so. Returns false if `ty` either does not meet
125 /// `bound` or is not known to meet bound (note that this is
126 /// conservative towards *no impl*, which is the opposite of the
127 /// `evaluate` methods).
128 pub fn type_known_to_meet_bound_modulo_regions<'a, 'tcx>(
129 infcx: &InferCtxt<'a, 'tcx>,
130 param_env: ty::ParamEnv<'tcx>,
136 "type_known_to_meet_bound_modulo_regions(ty={:?}, bound={:?})",
138 infcx.tcx.def_path_str(def_id)
141 let trait_ref = ty::TraitRef { def_id, substs: infcx.tcx.mk_substs_trait(ty, &[]) };
142 let obligation = Obligation {
144 cause: ObligationCause::misc(span, hir::CRATE_HIR_ID),
146 predicate: trait_ref.without_const().to_predicate(infcx.tcx),
149 let result = infcx.predicate_must_hold_modulo_regions(&obligation);
151 "type_known_to_meet_ty={:?} bound={} => {:?}",
153 infcx.tcx.def_path_str(def_id),
157 if result && ty.has_infer_types_or_consts() {
158 // Because of inference "guessing", selection can sometimes claim
159 // to succeed while the success requires a guess. To ensure
160 // this function's result remains infallible, we must confirm
161 // that guess. While imperfect, I believe this is sound.
163 // The handling of regions in this area of the code is terrible,
164 // see issue #29149. We should be able to improve on this with
166 let mut fulfill_cx = FulfillmentContext::new_ignoring_regions();
168 // We can use a dummy node-id here because we won't pay any mind
169 // to region obligations that arise (there shouldn't really be any
171 let cause = ObligationCause::misc(span, hir::CRATE_HIR_ID);
173 fulfill_cx.register_bound(infcx, param_env, ty, def_id, cause);
175 // Note: we only assume something is `Copy` if we can
176 // *definitively* show that it implements `Copy`. Otherwise,
177 // assume it is move; linear is always ok.
178 match fulfill_cx.select_all_or_error(infcx) {
181 "type_known_to_meet_bound_modulo_regions: ty={:?} bound={} success",
183 infcx.tcx.def_path_str(def_id)
189 "type_known_to_meet_bound_modulo_regions: ty={:?} bound={} errors={:?}",
191 infcx.tcx.def_path_str(def_id),
202 fn do_normalize_predicates<'tcx>(
204 region_context: DefId,
205 cause: ObligationCause<'tcx>,
206 elaborated_env: ty::ParamEnv<'tcx>,
207 predicates: Vec<ty::Predicate<'tcx>>,
208 ) -> Result<Vec<ty::Predicate<'tcx>>, ErrorReported> {
210 "do_normalize_predicates(predicates={:?}, region_context={:?}, cause={:?})",
211 predicates, region_context, cause,
213 let span = cause.span;
214 tcx.infer_ctxt().enter(|infcx| {
215 // FIXME. We should really... do something with these region
216 // obligations. But this call just continues the older
217 // behavior (i.e., doesn't cause any new bugs), and it would
218 // take some further refactoring to actually solve them. In
219 // particular, we would have to handle implied bounds
220 // properly, and that code is currently largely confined to
221 // regionck (though I made some efforts to extract it
224 // @arielby: In any case, these obligations are checked
225 // by wfcheck anyway, so I'm not sure we have to check
226 // them here too, and we will remove this function when
227 // we move over to lazy normalization *anyway*.
228 let fulfill_cx = FulfillmentContext::new_ignoring_regions();
230 match fully_normalize(&infcx, fulfill_cx, cause, elaborated_env, predicates) {
231 Ok(predicates) => predicates,
233 infcx.report_fulfillment_errors(&errors, None, false);
234 return Err(ErrorReported);
238 debug!("do_normalize_predictes: normalized predicates = {:?}", predicates);
240 // We can use the `elaborated_env` here; the region code only
241 // cares about declarations like `'a: 'b`.
242 let outlives_env = OutlivesEnvironment::new(elaborated_env);
244 infcx.resolve_regions_and_report_errors(
247 RegionckMode::default(),
250 let predicates = match infcx.fully_resolve(predicates) {
251 Ok(predicates) => predicates,
253 // If we encounter a fixup error, it means that some type
254 // variable wound up unconstrained. I actually don't know
255 // if this can happen, and I certainly don't expect it to
256 // happen often, but if it did happen it probably
257 // represents a legitimate failure due to some kind of
258 // unconstrained variable, and it seems better not to ICE,
259 // all things considered.
260 tcx.sess.span_err(span, &fixup_err.to_string());
261 return Err(ErrorReported);
264 if predicates.needs_infer() {
265 tcx.sess.delay_span_bug(span, "encountered inference variables after `fully_resolve`");
273 // FIXME: this is gonna need to be removed ...
274 /// Normalizes the parameter environment, reporting errors if they occur.
275 pub fn normalize_param_env_or_error<'tcx>(
277 region_context: DefId,
278 unnormalized_env: ty::ParamEnv<'tcx>,
279 cause: ObligationCause<'tcx>,
280 ) -> ty::ParamEnv<'tcx> {
281 // I'm not wild about reporting errors here; I'd prefer to
282 // have the errors get reported at a defined place (e.g.,
283 // during typeck). Instead I have all parameter
284 // environments, in effect, going through this function
285 // and hence potentially reporting errors. This ensures of
286 // course that we never forget to normalize (the
287 // alternative seemed like it would involve a lot of
288 // manual invocations of this fn -- and then we'd have to
289 // deal with the errors at each of those sites).
291 // In any case, in practice, typeck constructs all the
292 // parameter environments once for every fn as it goes,
293 // and errors will get reported then; so after typeck we
294 // can be sure that no errors should occur.
297 "normalize_param_env_or_error(region_context={:?}, unnormalized_env={:?}, cause={:?})",
298 region_context, unnormalized_env, cause
301 let mut predicates: Vec<_> =
302 util::elaborate_predicates(tcx, unnormalized_env.caller_bounds().into_iter())
303 .map(|obligation| obligation.predicate)
306 debug!("normalize_param_env_or_error: elaborated-predicates={:?}", predicates);
309 ty::ParamEnv::new(tcx.intern_predicates(&predicates), unnormalized_env.reveal());
311 // HACK: we are trying to normalize the param-env inside *itself*. The problem is that
312 // normalization expects its param-env to be already normalized, which means we have
315 // The way we handle this is by normalizing the param-env inside an unnormalized version
316 // of the param-env, which means that if the param-env contains unnormalized projections,
317 // we'll have some normalization failures. This is unfortunate.
319 // Lazy normalization would basically handle this by treating just the
320 // normalizing-a-trait-ref-requires-itself cycles as evaluation failures.
322 // Inferred outlives bounds can create a lot of `TypeOutlives` predicates for associated
323 // types, so to make the situation less bad, we normalize all the predicates *but*
324 // the `TypeOutlives` predicates first inside the unnormalized parameter environment, and
325 // then we normalize the `TypeOutlives` bounds inside the normalized parameter environment.
327 // This works fairly well because trait matching does not actually care about param-env
328 // TypeOutlives predicates - these are normally used by regionck.
329 let outlives_predicates: Vec<_> = predicates
330 .drain_filter(|predicate| {
331 matches!(predicate.kind().skip_binder(), ty::PredicateKind::TypeOutlives(..))
336 "normalize_param_env_or_error: predicates=(non-outlives={:?}, outlives={:?})",
337 predicates, outlives_predicates
339 let non_outlives_predicates = match do_normalize_predicates(
346 Ok(predicates) => predicates,
347 // An unnormalized env is better than nothing.
348 Err(ErrorReported) => {
349 debug!("normalize_param_env_or_error: errored resolving non-outlives predicates");
350 return elaborated_env;
354 debug!("normalize_param_env_or_error: non-outlives predicates={:?}", non_outlives_predicates);
356 // Not sure whether it is better to include the unnormalized TypeOutlives predicates
357 // here. I believe they should not matter, because we are ignoring TypeOutlives param-env
358 // predicates here anyway. Keeping them here anyway because it seems safer.
359 let outlives_env: Vec<_> =
360 non_outlives_predicates.iter().chain(&outlives_predicates).cloned().collect();
362 ty::ParamEnv::new(tcx.intern_predicates(&outlives_env), unnormalized_env.reveal());
363 let outlives_predicates = match do_normalize_predicates(
370 Ok(predicates) => predicates,
371 // An unnormalized env is better than nothing.
372 Err(ErrorReported) => {
373 debug!("normalize_param_env_or_error: errored resolving outlives predicates");
374 return elaborated_env;
377 debug!("normalize_param_env_or_error: outlives predicates={:?}", outlives_predicates);
379 let mut predicates = non_outlives_predicates;
380 predicates.extend(outlives_predicates);
381 debug!("normalize_param_env_or_error: final predicates={:?}", predicates);
382 ty::ParamEnv::new(tcx.intern_predicates(&predicates), unnormalized_env.reveal())
385 pub fn fully_normalize<'a, 'tcx, T>(
386 infcx: &InferCtxt<'a, 'tcx>,
387 mut fulfill_cx: FulfillmentContext<'tcx>,
388 cause: ObligationCause<'tcx>,
389 param_env: ty::ParamEnv<'tcx>,
391 ) -> Result<T, Vec<FulfillmentError<'tcx>>>
393 T: TypeFoldable<'tcx>,
395 debug!("fully_normalize_with_fulfillcx(value={:?})", value);
396 let selcx = &mut SelectionContext::new(infcx);
397 let Normalized { value: normalized_value, obligations } =
398 project::normalize(selcx, param_env, cause, value);
400 "fully_normalize: normalized_value={:?} obligations={:?}",
401 normalized_value, obligations
403 for obligation in obligations {
404 fulfill_cx.register_predicate_obligation(selcx.infcx(), obligation);
407 debug!("fully_normalize: select_all_or_error start");
408 fulfill_cx.select_all_or_error(infcx)?;
409 debug!("fully_normalize: select_all_or_error complete");
410 let resolved_value = infcx.resolve_vars_if_possible(normalized_value);
411 debug!("fully_normalize: resolved_value={:?}", resolved_value);
415 /// Normalizes the predicates and checks whether they hold in an empty environment. If this
416 /// returns true, then either normalize encountered an error or one of the predicates did not
417 /// hold. Used when creating vtables to check for unsatisfiable methods.
418 pub fn impossible_predicates<'tcx>(
420 predicates: Vec<ty::Predicate<'tcx>>,
422 debug!("impossible_predicates(predicates={:?})", predicates);
424 let result = tcx.infer_ctxt().enter(|infcx| {
425 let param_env = ty::ParamEnv::reveal_all();
426 let mut selcx = SelectionContext::new(&infcx);
427 let mut fulfill_cx = FulfillmentContext::new();
428 let cause = ObligationCause::dummy();
429 let Normalized { value: predicates, obligations } =
430 normalize(&mut selcx, param_env, cause.clone(), predicates);
431 for obligation in obligations {
432 fulfill_cx.register_predicate_obligation(&infcx, obligation);
434 for predicate in predicates {
435 let obligation = Obligation::new(cause.clone(), param_env, predicate);
436 fulfill_cx.register_predicate_obligation(&infcx, obligation);
439 fulfill_cx.select_all_or_error(&infcx).is_err()
441 debug!("impossible_predicates = {:?}", result);
445 fn subst_and_check_impossible_predicates<'tcx>(
447 key: (DefId, SubstsRef<'tcx>),
449 debug!("subst_and_check_impossible_predicates(key={:?})", key);
451 let mut predicates = tcx.predicates_of(key.0).instantiate(tcx, key.1).predicates;
452 predicates.retain(|predicate| !predicate.needs_subst());
453 let result = impossible_predicates(tcx, predicates);
455 debug!("subst_and_check_impossible_predicates(key={:?}) = {:?}", key, result);
459 #[derive(Clone, Debug)]
460 enum VtblSegment<'tcx> {
462 TraitOwnEntries { trait_ref: ty::PolyTraitRef<'tcx>, emit_vptr: bool },
465 /// Prepare the segments for a vtable
466 fn prepare_vtable_segments<'tcx, T>(
468 trait_ref: ty::PolyTraitRef<'tcx>,
469 mut segment_visitor: impl FnMut(VtblSegment<'tcx>) -> ControlFlow<T>,
471 // The following constraints holds for the final arrangement.
472 // 1. The whole virtual table of the first direct super trait is included as the
473 // the prefix. If this trait doesn't have any super traits, then this step
474 // consists of the dsa metadata.
475 // 2. Then comes the proper pointer metadata(vptr) and all own methods for all
476 // other super traits except those already included as part of the first
477 // direct super trait virtual table.
478 // 3. finally, the own methods of this trait.
480 // This has the advantage that trait upcasting to the first direct super trait on each level
481 // is zero cost, and to another trait includes only replacing the pointer with one level indirection,
482 // while not using too much extra memory.
484 // For a single inheritance relationship like this,
485 // D --> C --> B --> A
486 // The resulting vtable will consists of these segments:
489 // For a multiple inheritance relationship like this,
492 // The resulting vtable will consists of these segments:
493 // DSA, A, B, B-vptr, C, D
495 // For a diamond inheritance relationship like this,
498 // The resulting vtable will consists of these segments:
499 // DSA, A, B, C, C-vptr, D
501 // For a more complex inheritance relationship like this:
502 // O --> G --> C --> A
510 // The resulting vtable will consists of these segments:
511 // DSA, A, B, B-vptr, C, D, D-vptr, E, E-vptr, F, F-vptr, G,
512 // H, H-vptr, I, I-vptr, J, J-vptr, K, K-vptr, L, L-vptr, M, M-vptr,
515 // emit dsa segment first.
516 if let ControlFlow::Break(v) = (segment_visitor)(VtblSegment::MetadataDSA) {
520 let mut emit_vptr_on_new_entry = false;
521 let mut visited = util::PredicateSet::new(tcx);
522 let predicate = trait_ref.without_const().to_predicate(tcx);
523 let mut stack: SmallVec<[(ty::PolyTraitRef<'tcx>, _, _); 5]> =
524 smallvec![(trait_ref, emit_vptr_on_new_entry, None)];
525 visited.insert(predicate);
527 // the main traversal loop:
528 // basically we want to cut the inheritance directed graph into a few non-overlapping slices of nodes
529 // that each node is emited after all its descendents have been emitted.
530 // so we convert the directed graph into a tree by skipping all previously visted nodes using a visited set.
531 // this is done on the fly.
532 // Each loop run emits a slice - it starts by find a "childless" unvisited node, backtracking upwards, and it
533 // stops after it finds a node that has a next-sibling node.
534 // This next-sibling node will used as the starting point of next slice.
537 // For a diamond inheritance relationship like this,
538 // D#1 --> B#0 --> A#0
541 // Starting point 0 stack [D]
542 // Loop run #0: Stack after diving in is [D B A], A is "childless"
543 // after this point, all newly visited nodes won't have a vtable that equals to a prefix of this one.
544 // Loop run #0: Emiting the slice [B A] (in reverse order), B has a next-sibling node, so this slice stops here.
545 // Loop run #0: Stack after exiting out is [D C], C is the next starting point.
546 // Loop run #1: Stack after diving in is [D C], C is "childless", since its child A is skipped(already emitted).
547 // Loop run #1: Emiting the slice [D C] (in reverse order). No one has a next-sibling node.
548 // Loop run #1: Stack after exiting out is []. Now the function exits.
551 // dive deeper into the stack, recording the path
553 if let Some((inner_most_trait_ref, _, _)) = stack.last() {
554 let inner_most_trait_ref = *inner_most_trait_ref;
555 let mut direct_super_traits_iter = tcx
556 .super_predicates_of(inner_most_trait_ref.def_id())
559 .filter_map(move |(pred, _)| {
560 pred.subst_supertrait(tcx, &inner_most_trait_ref).to_opt_poly_trait_ref()
563 'diving_in_skip_visited_traits: loop {
564 if let Some(next_super_trait) = direct_super_traits_iter.next() {
565 if visited.insert(next_super_trait.to_predicate(tcx)) {
567 next_super_trait.value,
568 emit_vptr_on_new_entry,
569 Some(direct_super_traits_iter),
571 break 'diving_in_skip_visited_traits;
573 continue 'diving_in_skip_visited_traits;
582 // Other than the left-most path, vptr should be emitted for each trait.
583 emit_vptr_on_new_entry = true;
585 // emit innermost item, move to next sibling and stop there if possible, otherwise jump to outer level.
587 if let Some((inner_most_trait_ref, emit_vptr, siblings_opt)) = stack.last_mut() {
588 if let ControlFlow::Break(v) = (segment_visitor)(VtblSegment::TraitOwnEntries {
589 trait_ref: *inner_most_trait_ref,
590 emit_vptr: *emit_vptr,
595 'exiting_out_skip_visited_traits: loop {
596 if let Some(siblings) = siblings_opt {
597 if let Some(next_inner_most_trait_ref) = siblings.next() {
598 if visited.insert(next_inner_most_trait_ref.to_predicate(tcx)) {
599 *inner_most_trait_ref = next_inner_most_trait_ref.value;
600 *emit_vptr = emit_vptr_on_new_entry;
603 continue 'exiting_out_skip_visited_traits;
608 continue 'exiting_out;
617 fn dump_vtable_entries<'tcx>(
620 trait_ref: ty::PolyTraitRef<'tcx>,
621 entries: &[VtblEntry<'tcx>],
623 let msg = format!("Vtable entries for `{}`: {:#?}", trait_ref, entries);
624 tcx.sess.struct_span_err(sp, &msg).emit();
627 /// Given a trait `trait_ref`, iterates the vtable entries
628 /// that come from `trait_ref`, including its supertraits.
629 fn vtable_entries<'tcx>(
631 trait_ref: ty::PolyTraitRef<'tcx>,
632 ) -> &'tcx [VtblEntry<'tcx>] {
633 debug!("vtable_entries({:?})", trait_ref);
635 let mut entries = vec![];
637 let vtable_segment_callback = |segment| -> ControlFlow<()> {
639 VtblSegment::MetadataDSA => {
640 entries.extend(COMMON_VTABLE_ENTRIES);
642 VtblSegment::TraitOwnEntries { trait_ref, emit_vptr } => {
643 let trait_methods = tcx
644 .associated_items(trait_ref.def_id())
645 .in_definition_order()
646 .filter(|item| item.kind == ty::AssocKind::Fn);
647 // Now list each method's DefId and InternalSubsts (for within its trait).
648 // If the method can never be called from this object, produce `Vacant`.
649 let own_entries = trait_methods.map(move |trait_method| {
650 debug!("vtable_entries: trait_method={:?}", trait_method);
651 let def_id = trait_method.def_id;
653 // Some methods cannot be called on an object; skip those.
654 if !is_vtable_safe_method(tcx, trait_ref.def_id(), &trait_method) {
655 debug!("vtable_entries: not vtable safe");
656 return VtblEntry::Vacant;
659 // The method may have some early-bound lifetimes; add regions for those.
660 let substs = trait_ref.map_bound(|trait_ref| {
661 InternalSubsts::for_item(tcx, def_id, |param, _| match param.kind {
662 GenericParamDefKind::Lifetime => tcx.lifetimes.re_erased.into(),
663 GenericParamDefKind::Type { .. }
664 | GenericParamDefKind::Const { .. } => {
665 trait_ref.substs[param.index as usize]
670 // The trait type may have higher-ranked lifetimes in it;
671 // erase them if they appear, so that we get the type
672 // at some particular call site.
674 .normalize_erasing_late_bound_regions(ty::ParamEnv::reveal_all(), substs);
676 // It's possible that the method relies on where-clauses that
677 // do not hold for this particular set of type parameters.
678 // Note that this method could then never be called, so we
679 // do not want to try and codegen it, in that case (see #23435).
680 let predicates = tcx.predicates_of(def_id).instantiate_own(tcx, substs);
681 if impossible_predicates(tcx, predicates.predicates) {
682 debug!("vtable_entries: predicates do not hold");
683 return VtblEntry::Vacant;
686 let instance = ty::Instance::resolve_for_vtable(
688 ty::ParamEnv::reveal_all(),
692 .expect("resolution failed during building vtable representation");
693 VtblEntry::Method(instance)
696 entries.extend(own_entries);
699 entries.push(VtblEntry::TraitVPtr(trait_ref));
704 ControlFlow::Continue(())
707 let _ = prepare_vtable_segments(tcx, trait_ref, vtable_segment_callback);
709 if tcx.has_attr(trait_ref.def_id(), sym::rustc_dump_vtable) {
710 let sp = tcx.def_span(trait_ref.def_id());
711 dump_vtable_entries(tcx, sp, trait_ref, &entries);
714 tcx.arena.alloc_from_iter(entries.into_iter())
717 /// Find slot base for trait methods within vtable entries of another trait
718 fn vtable_trait_first_method_offset<'tcx>(
721 ty::PolyTraitRef<'tcx>, // trait_to_be_found
722 ty::PolyTraitRef<'tcx>, // trait_owning_vtable
725 let (trait_to_be_found, trait_owning_vtable) = key;
727 let vtable_segment_callback = {
728 let mut vtable_base = 0;
732 VtblSegment::MetadataDSA => {
733 vtable_base += COMMON_VTABLE_ENTRIES.len();
735 VtblSegment::TraitOwnEntries { trait_ref, emit_vptr } => {
736 if trait_ref == trait_to_be_found {
737 return ControlFlow::Break(vtable_base);
739 vtable_base += util::count_own_vtable_entries(tcx, trait_ref);
745 ControlFlow::Continue(())
749 if let Some(vtable_base) =
750 prepare_vtable_segments(tcx, trait_owning_vtable, vtable_segment_callback)
754 bug!("Failed to find info for expected trait in vtable");
758 /// Find slot offset for trait vptr within vtable entries of another trait
759 /// FIXME: This function is not yet used. Remove `#[allow(dead_code)]` when it's used in upcoming pr.
761 fn vtable_trait_vptr_slot_offset<'tcx>(
764 ty::PolyTraitRef<'tcx>, // trait_to_be_found
765 ty::PolyTraitRef<'tcx>, // trait_owning_vtable
768 let (trait_to_be_found, trait_owning_vtable) = key;
770 let vtable_segment_callback = {
771 let mut vptr_offset = 0;
774 VtblSegment::MetadataDSA => {
775 vptr_offset += COMMON_VTABLE_ENTRIES.len();
777 VtblSegment::TraitOwnEntries { trait_ref, emit_vptr } => {
778 vptr_offset += util::count_own_vtable_entries(tcx, trait_ref);
779 if trait_ref == trait_to_be_found {
781 return ControlFlow::Break(Some(vptr_offset));
783 return ControlFlow::Break(None);
792 ControlFlow::Continue(())
796 if let Some(vptr_offset) =
797 prepare_vtable_segments(tcx, trait_owning_vtable, vtable_segment_callback)
801 bug!("Failed to find info for expected trait in vtable");
805 pub fn provide(providers: &mut ty::query::Providers) {
806 object_safety::provide(providers);
807 structural_match::provide(providers);
808 *providers = ty::query::Providers {
809 specialization_graph_of: specialize::specialization_graph_provider,
810 specializes: specialize::specializes,
811 codegen_fulfill_obligation: codegen::codegen_fulfill_obligation,
813 subst_and_check_impossible_predicates,
814 mir_abstract_const: |tcx, def_id| {
815 let def_id = def_id.expect_local();
816 if let Some(def) = ty::WithOptConstParam::try_lookup(def_id, tcx) {
817 tcx.mir_abstract_const_of_const_arg(def)
819 const_evaluatable::mir_abstract_const(tcx, ty::WithOptConstParam::unknown(def_id))
822 mir_abstract_const_of_const_arg: |tcx, (did, param_did)| {
823 const_evaluatable::mir_abstract_const(
825 ty::WithOptConstParam { did, const_param_did: Some(param_did) },
828 try_unify_abstract_consts: const_evaluatable::try_unify_abstract_consts,