pub mod auto_trait;
mod chalk_fulfill;
-pub mod codegen;
mod coherence;
pub mod const_evaluatable;
mod engine;
mod specialize;
mod structural_match;
mod util;
+mod vtable;
pub mod wf;
-use crate::errors::DumpVTableEntries;
use crate::infer::outlives::env::OutlivesEnvironment;
use crate::infer::{InferCtxt, TyCtxtInferExt};
use crate::traits::error_reporting::TypeErrCtxtExt as _;
use rustc_errors::ErrorGuaranteed;
use rustc_hir as hir;
use rustc_hir::def_id::DefId;
-use rustc_hir::lang_items::LangItem;
use rustc_middle::ty::fold::TypeFoldable;
use rustc_middle::ty::visit::TypeVisitable;
-use rustc_middle::ty::{
- self, DefIdTree, GenericParamDefKind, ToPredicate, Ty, TyCtxt, TypeSuperVisitable, VtblEntry,
-};
+use rustc_middle::ty::{self, DefIdTree, ToPredicate, Ty, TyCtxt, TypeSuperVisitable};
use rustc_middle::ty::{InternalSubsts, SubstsRef};
-use rustc_span::{sym, Span};
-use smallvec::SmallVec;
+use rustc_span::Span;
use std::fmt::Debug;
use std::ops::ControlFlow;
bound: DefId,
) -> Vec<FulfillmentError<'tcx>> {
let tcx = infcx.tcx;
- let trait_ref = ty::TraitRef { def_id: bound, substs: tcx.mk_substs_trait(ty, []) };
- let obligation = Obligation {
- cause,
- recursion_depth: 0,
- param_env,
- predicate: ty::Binder::dummy(trait_ref).without_const().to_predicate(tcx),
- };
+ let trait_ref = tcx.mk_trait_ref(bound, [ty]);
+ let obligation = Obligation::new(tcx, cause, param_env, ty::Binder::dummy(trait_ref));
fully_solve_obligation(infcx, obligation)
}
false
}
-#[derive(Clone, Debug)]
-enum VtblSegment<'tcx> {
- MetadataDSA,
- TraitOwnEntries { trait_ref: ty::PolyTraitRef<'tcx>, emit_vptr: bool },
-}
-
-/// Prepare the segments for a vtable
-fn prepare_vtable_segments<'tcx, T>(
- tcx: TyCtxt<'tcx>,
- trait_ref: ty::PolyTraitRef<'tcx>,
- mut segment_visitor: impl FnMut(VtblSegment<'tcx>) -> ControlFlow<T>,
-) -> Option<T> {
- // The following constraints holds for the final arrangement.
- // 1. The whole virtual table of the first direct super trait is included as the
- // the prefix. If this trait doesn't have any super traits, then this step
- // consists of the dsa metadata.
- // 2. Then comes the proper pointer metadata(vptr) and all own methods for all
- // other super traits except those already included as part of the first
- // direct super trait virtual table.
- // 3. finally, the own methods of this trait.
-
- // This has the advantage that trait upcasting to the first direct super trait on each level
- // is zero cost, and to another trait includes only replacing the pointer with one level indirection,
- // while not using too much extra memory.
-
- // For a single inheritance relationship like this,
- // D --> C --> B --> A
- // The resulting vtable will consists of these segments:
- // DSA, A, B, C, D
-
- // For a multiple inheritance relationship like this,
- // D --> C --> A
- // \-> B
- // The resulting vtable will consists of these segments:
- // DSA, A, B, B-vptr, C, D
-
- // For a diamond inheritance relationship like this,
- // D --> B --> A
- // \-> C -/
- // The resulting vtable will consists of these segments:
- // DSA, A, B, C, C-vptr, D
-
- // For a more complex inheritance relationship like this:
- // O --> G --> C --> A
- // \ \ \-> B
- // | |-> F --> D
- // | \-> E
- // |-> N --> J --> H
- // \ \-> I
- // |-> M --> K
- // \-> L
- // The resulting vtable will consists of these segments:
- // DSA, A, B, B-vptr, C, D, D-vptr, E, E-vptr, F, F-vptr, G,
- // H, H-vptr, I, I-vptr, J, J-vptr, K, K-vptr, L, L-vptr, M, M-vptr,
- // N, N-vptr, O
-
- // emit dsa segment first.
- if let ControlFlow::Break(v) = (segment_visitor)(VtblSegment::MetadataDSA) {
- return Some(v);
- }
-
- let mut emit_vptr_on_new_entry = false;
- let mut visited = util::PredicateSet::new(tcx);
- let predicate = trait_ref.without_const().to_predicate(tcx);
- let mut stack: SmallVec<[(ty::PolyTraitRef<'tcx>, _, _); 5]> =
- smallvec![(trait_ref, emit_vptr_on_new_entry, None)];
- visited.insert(predicate);
-
- // the main traversal loop:
- // basically we want to cut the inheritance directed graph into a few non-overlapping slices of nodes
- // that each node is emitted after all its descendents have been emitted.
- // so we convert the directed graph into a tree by skipping all previously visited nodes using a visited set.
- // this is done on the fly.
- // Each loop run emits a slice - it starts by find a "childless" unvisited node, backtracking upwards, and it
- // stops after it finds a node that has a next-sibling node.
- // This next-sibling node will used as the starting point of next slice.
-
- // Example:
- // For a diamond inheritance relationship like this,
- // D#1 --> B#0 --> A#0
- // \-> C#1 -/
-
- // Starting point 0 stack [D]
- // Loop run #0: Stack after diving in is [D B A], A is "childless"
- // after this point, all newly visited nodes won't have a vtable that equals to a prefix of this one.
- // Loop run #0: Emitting the slice [B A] (in reverse order), B has a next-sibling node, so this slice stops here.
- // Loop run #0: Stack after exiting out is [D C], C is the next starting point.
- // Loop run #1: Stack after diving in is [D C], C is "childless", since its child A is skipped(already emitted).
- // Loop run #1: Emitting the slice [D C] (in reverse order). No one has a next-sibling node.
- // Loop run #1: Stack after exiting out is []. Now the function exits.
-
- loop {
- // dive deeper into the stack, recording the path
- 'diving_in: loop {
- if let Some((inner_most_trait_ref, _, _)) = stack.last() {
- let inner_most_trait_ref = *inner_most_trait_ref;
- let mut direct_super_traits_iter = tcx
- .super_predicates_of(inner_most_trait_ref.def_id())
- .predicates
- .into_iter()
- .filter_map(move |(pred, _)| {
- pred.subst_supertrait(tcx, &inner_most_trait_ref).to_opt_poly_trait_pred()
- });
-
- 'diving_in_skip_visited_traits: loop {
- if let Some(next_super_trait) = direct_super_traits_iter.next() {
- if visited.insert(next_super_trait.to_predicate(tcx)) {
- // We're throwing away potential constness of super traits here.
- // FIXME: handle ~const super traits
- let next_super_trait = next_super_trait.map_bound(|t| t.trait_ref);
- stack.push((
- next_super_trait,
- emit_vptr_on_new_entry,
- Some(direct_super_traits_iter),
- ));
- break 'diving_in_skip_visited_traits;
- } else {
- continue 'diving_in_skip_visited_traits;
- }
- } else {
- break 'diving_in;
- }
- }
- }
- }
-
- // Other than the left-most path, vptr should be emitted for each trait.
- emit_vptr_on_new_entry = true;
-
- // emit innermost item, move to next sibling and stop there if possible, otherwise jump to outer level.
- 'exiting_out: loop {
- if let Some((inner_most_trait_ref, emit_vptr, siblings_opt)) = stack.last_mut() {
- if let ControlFlow::Break(v) = (segment_visitor)(VtblSegment::TraitOwnEntries {
- trait_ref: *inner_most_trait_ref,
- emit_vptr: *emit_vptr,
- }) {
- return Some(v);
- }
-
- 'exiting_out_skip_visited_traits: loop {
- if let Some(siblings) = siblings_opt {
- if let Some(next_inner_most_trait_ref) = siblings.next() {
- if visited.insert(next_inner_most_trait_ref.to_predicate(tcx)) {
- // We're throwing away potential constness of super traits here.
- // FIXME: handle ~const super traits
- let next_inner_most_trait_ref =
- next_inner_most_trait_ref.map_bound(|t| t.trait_ref);
- *inner_most_trait_ref = next_inner_most_trait_ref;
- *emit_vptr = emit_vptr_on_new_entry;
- break 'exiting_out;
- } else {
- continue 'exiting_out_skip_visited_traits;
- }
- }
- }
- stack.pop();
- continue 'exiting_out;
- }
- }
- // all done
- return None;
- }
- }
-}
-
-fn dump_vtable_entries<'tcx>(
- tcx: TyCtxt<'tcx>,
- sp: Span,
- trait_ref: ty::PolyTraitRef<'tcx>,
- entries: &[VtblEntry<'tcx>],
-) {
- tcx.sess.emit_err(DumpVTableEntries {
- span: sp,
- trait_ref,
- entries: format!("{:#?}", entries),
- });
-}
-
-fn own_existential_vtable_entries<'tcx>(tcx: TyCtxt<'tcx>, trait_def_id: DefId) -> &'tcx [DefId] {
- let trait_methods = tcx
- .associated_items(trait_def_id)
- .in_definition_order()
- .filter(|item| item.kind == ty::AssocKind::Fn);
- // Now list each method's DefId (for within its trait).
- let own_entries = trait_methods.filter_map(move |trait_method| {
- debug!("own_existential_vtable_entry: trait_method={:?}", trait_method);
- let def_id = trait_method.def_id;
-
- // Some methods cannot be called on an object; skip those.
- if !is_vtable_safe_method(tcx, trait_def_id, &trait_method) {
- debug!("own_existential_vtable_entry: not vtable safe");
- return None;
- }
-
- Some(def_id)
- });
-
- tcx.arena.alloc_from_iter(own_entries.into_iter())
-}
-
-/// Given a trait `trait_ref`, iterates the vtable entries
-/// that come from `trait_ref`, including its supertraits.
-fn vtable_entries<'tcx>(
- tcx: TyCtxt<'tcx>,
- trait_ref: ty::PolyTraitRef<'tcx>,
-) -> &'tcx [VtblEntry<'tcx>] {
- debug!("vtable_entries({:?})", trait_ref);
-
- let mut entries = vec![];
-
- let vtable_segment_callback = |segment| -> ControlFlow<()> {
- match segment {
- VtblSegment::MetadataDSA => {
- entries.extend(TyCtxt::COMMON_VTABLE_ENTRIES);
- }
- VtblSegment::TraitOwnEntries { trait_ref, emit_vptr } => {
- let existential_trait_ref = trait_ref
- .map_bound(|trait_ref| ty::ExistentialTraitRef::erase_self_ty(tcx, trait_ref));
-
- // Lookup the shape of vtable for the trait.
- let own_existential_entries =
- tcx.own_existential_vtable_entries(existential_trait_ref.def_id());
-
- let own_entries = own_existential_entries.iter().copied().map(|def_id| {
- debug!("vtable_entries: trait_method={:?}", def_id);
-
- // The method may have some early-bound lifetimes; add regions for those.
- let substs = trait_ref.map_bound(|trait_ref| {
- InternalSubsts::for_item(tcx, def_id, |param, _| match param.kind {
- GenericParamDefKind::Lifetime => tcx.lifetimes.re_erased.into(),
- GenericParamDefKind::Type { .. }
- | GenericParamDefKind::Const { .. } => {
- trait_ref.substs[param.index as usize]
- }
- })
- });
-
- // The trait type may have higher-ranked lifetimes in it;
- // erase them if they appear, so that we get the type
- // at some particular call site.
- let substs = tcx
- .normalize_erasing_late_bound_regions(ty::ParamEnv::reveal_all(), substs);
-
- // It's possible that the method relies on where-clauses that
- // do not hold for this particular set of type parameters.
- // Note that this method could then never be called, so we
- // do not want to try and codegen it, in that case (see #23435).
- let predicates = tcx.predicates_of(def_id).instantiate_own(tcx, substs);
- if impossible_predicates(tcx, predicates.predicates) {
- debug!("vtable_entries: predicates do not hold");
- return VtblEntry::Vacant;
- }
-
- let instance = ty::Instance::resolve_for_vtable(
- tcx,
- ty::ParamEnv::reveal_all(),
- def_id,
- substs,
- )
- .expect("resolution failed during building vtable representation");
- VtblEntry::Method(instance)
- });
-
- entries.extend(own_entries);
-
- if emit_vptr {
- entries.push(VtblEntry::TraitVPtr(trait_ref));
- }
- }
- }
-
- ControlFlow::Continue(())
- };
-
- let _ = prepare_vtable_segments(tcx, trait_ref, vtable_segment_callback);
-
- if tcx.has_attr(trait_ref.def_id(), sym::rustc_dump_vtable) {
- let sp = tcx.def_span(trait_ref.def_id());
- dump_vtable_entries(tcx, sp, trait_ref, &entries);
- }
-
- tcx.arena.alloc_from_iter(entries.into_iter())
-}
-
-/// Find slot base for trait methods within vtable entries of another trait
-fn vtable_trait_first_method_offset<'tcx>(
- tcx: TyCtxt<'tcx>,
- key: (
- ty::PolyTraitRef<'tcx>, // trait_to_be_found
- ty::PolyTraitRef<'tcx>, // trait_owning_vtable
- ),
-) -> usize {
- let (trait_to_be_found, trait_owning_vtable) = key;
-
- // #90177
- let trait_to_be_found_erased = tcx.erase_regions(trait_to_be_found);
-
- let vtable_segment_callback = {
- let mut vtable_base = 0;
-
- move |segment| {
- match segment {
- VtblSegment::MetadataDSA => {
- vtable_base += TyCtxt::COMMON_VTABLE_ENTRIES.len();
- }
- VtblSegment::TraitOwnEntries { trait_ref, emit_vptr } => {
- if tcx.erase_regions(trait_ref) == trait_to_be_found_erased {
- return ControlFlow::Break(vtable_base);
- }
- vtable_base += util::count_own_vtable_entries(tcx, trait_ref);
- if emit_vptr {
- vtable_base += 1;
- }
- }
- }
- ControlFlow::Continue(())
- }
- };
-
- if let Some(vtable_base) =
- prepare_vtable_segments(tcx, trait_owning_vtable, vtable_segment_callback)
- {
- vtable_base
- } else {
- bug!("Failed to find info for expected trait in vtable");
- }
-}
-
-/// Find slot offset for trait vptr within vtable entries of another trait
-pub fn vtable_trait_upcasting_coercion_new_vptr_slot<'tcx>(
- tcx: TyCtxt<'tcx>,
- key: (
- Ty<'tcx>, // trait object type whose trait owning vtable
- Ty<'tcx>, // trait object for supertrait
- ),
-) -> Option<usize> {
- let (source, target) = key;
- assert!(matches!(&source.kind(), &ty::Dynamic(..)) && !source.needs_infer());
- assert!(matches!(&target.kind(), &ty::Dynamic(..)) && !target.needs_infer());
-
- // this has been typecked-before, so diagnostics is not really needed.
- let unsize_trait_did = tcx.require_lang_item(LangItem::Unsize, None);
-
- let trait_ref = tcx.mk_trait_ref(unsize_trait_did, [source, target]);
-
- match tcx.codegen_select_candidate((ty::ParamEnv::reveal_all(), ty::Binder::dummy(trait_ref))) {
- Ok(ImplSource::TraitUpcasting(implsrc_traitcasting)) => {
- implsrc_traitcasting.vtable_vptr_slot
- }
- otherwise => bug!("expected TraitUpcasting candidate, got {otherwise:?}"),
- }
-}
-
pub fn provide(providers: &mut ty::query::Providers) {
object_safety::provide(providers);
- structural_match::provide(providers);
+ vtable::provide(providers);
*providers = ty::query::Providers {
specialization_graph_of: specialize::specialization_graph_provider,
specializes: specialize::specializes,
- codegen_select_candidate: codegen::codegen_select_candidate,
- own_existential_vtable_entries,
- vtable_entries,
- vtable_trait_upcasting_coercion_new_vptr_slot,
subst_and_check_impossible_predicates,
is_impossible_method,
..*providers
projects / rust.git / blobdiff