Reduce queries/map lookups done by coherence
This has negligible perf impact, but it does improve the code a bit. * Only query the specialization graph of any trait once instead of once per impl * Loop over impls only once, precomputing impl DefId and TraitRef
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71c7e149e4
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@ -18,14 +18,12 @@ use rustc_hir::def_id::DefId;
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use rustc_hir::ItemKind;
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pub fn check_trait(tcx: TyCtxt<'_>, trait_def_id: DefId) {
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let lang_items = tcx.lang_items();
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Checker { tcx, trait_def_id }
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.check(tcx.lang_items().drop_trait(), visit_implementation_of_drop)
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.check(tcx.lang_items().copy_trait(), visit_implementation_of_copy)
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.check(tcx.lang_items().coerce_unsized_trait(), visit_implementation_of_coerce_unsized)
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.check(
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tcx.lang_items().dispatch_from_dyn_trait(),
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visit_implementation_of_dispatch_from_dyn,
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);
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.check(lang_items.drop_trait(), visit_implementation_of_drop)
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.check(lang_items.copy_trait(), visit_implementation_of_copy)
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.check(lang_items.coerce_unsized_trait(), visit_implementation_of_coerce_unsized)
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.check(lang_items.dispatch_from_dyn_trait(), visit_implementation_of_dispatch_from_dyn);
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}
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struct Checker<'tcx> {
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@ -10,7 +10,6 @@ use rustc::ty::query::Providers;
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use rustc::ty::{self, TyCtxt, TypeFoldable};
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use rustc_errors::struct_span_err;
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use rustc_hir::def_id::{DefId, LOCAL_CRATE};
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use rustc_hir::HirId;
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mod builtin;
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mod inherent_impls;
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@ -18,28 +17,21 @@ mod inherent_impls_overlap;
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mod orphan;
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mod unsafety;
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fn check_impl(tcx: TyCtxt<'_>, hir_id: HirId) {
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let impl_def_id = tcx.hir().local_def_id(hir_id);
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fn check_impl(tcx: TyCtxt<'_>, impl_def_id: DefId, trait_ref: ty::TraitRef<'_>) {
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debug!(
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"(checking implementation) adding impl for trait '{:?}', item '{}'",
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trait_ref,
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tcx.def_path_str(impl_def_id)
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);
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// If there are no traits, then this implementation must have a
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// base type.
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if let Some(trait_ref) = tcx.impl_trait_ref(impl_def_id) {
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debug!(
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"(checking implementation) adding impl for trait '{:?}', item '{}'",
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trait_ref,
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tcx.def_path_str(impl_def_id)
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);
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// Skip impls where one of the self type is an error type.
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// This occurs with e.g., resolve failures (#30589).
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if trait_ref.references_error() {
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return;
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}
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enforce_trait_manually_implementable(tcx, impl_def_id, trait_ref.def_id);
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enforce_empty_impls_for_marker_traits(tcx, impl_def_id, trait_ref.def_id);
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// Skip impls where one of the self type is an error type.
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// This occurs with e.g., resolve failures (#30589).
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if trait_ref.references_error() {
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return;
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}
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enforce_trait_manually_implementable(tcx, impl_def_id, trait_ref.def_id);
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enforce_empty_impls_for_marker_traits(tcx, impl_def_id, trait_ref.def_id);
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}
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fn enforce_trait_manually_implementable(tcx: TyCtxt<'_>, impl_def_id: DefId, trait_def_id: DefId) {
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@ -129,12 +121,17 @@ pub fn provide(providers: &mut Providers<'_>) {
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}
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fn coherent_trait(tcx: TyCtxt<'_>, def_id: DefId) {
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// Trigger building the specialization graph for the trait. This will detect and report any
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// overlap errors.
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tcx.specialization_graph_of(def_id);
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let impls = tcx.hir().trait_impls(def_id);
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for &impl_id in impls {
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check_impl(tcx, impl_id);
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}
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for &impl_id in impls {
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check_impl_overlap(tcx, impl_id);
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for &hir_id in impls {
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let impl_def_id = tcx.hir().local_def_id(hir_id);
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let trait_ref = tcx.impl_trait_ref(impl_def_id).unwrap();
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check_impl(tcx, impl_def_id, trait_ref);
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check_object_overlap(tcx, impl_def_id, trait_ref);
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}
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builtin::check_trait(tcx, def_id);
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}
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@ -152,12 +149,12 @@ pub fn check_coherence(tcx: TyCtxt<'_>) {
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tcx.ensure().crate_inherent_impls_overlap_check(LOCAL_CRATE);
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}
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/// Overlap: no two impls for the same trait are implemented for the
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/// same type. Likewise, no two inherent impls for a given type
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/// constructor provide a method with the same name.
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fn check_impl_overlap<'tcx>(tcx: TyCtxt<'tcx>, hir_id: HirId) {
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let impl_def_id = tcx.hir().local_def_id(hir_id);
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let trait_ref = tcx.impl_trait_ref(impl_def_id).unwrap();
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/// Checks whether an impl overlaps with the automatic `impl Trait for dyn Trait`.
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fn check_object_overlap<'tcx>(
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tcx: TyCtxt<'tcx>,
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impl_def_id: DefId,
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trait_ref: ty::TraitRef<'tcx>,
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) {
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let trait_def_id = trait_ref.def_id;
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if trait_ref.references_error() {
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@ -165,11 +162,7 @@ fn check_impl_overlap<'tcx>(tcx: TyCtxt<'tcx>, hir_id: HirId) {
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return;
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}
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// Trigger building the specialization graph for the trait of this impl.
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// This will detect any overlap errors.
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tcx.specialization_graph_of(trait_def_id);
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// check for overlap with the automatic `impl Trait for Trait`
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// check for overlap with the automatic `impl Trait for dyn Trait`
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if let ty::Dynamic(ref data, ..) = trait_ref.self_ty().kind {
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// This is something like impl Trait1 for Trait2. Illegal
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// if Trait1 is a supertrait of Trait2 or Trait2 is not object safe.
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@ -1,10 +1,10 @@
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error[E0391]: cycle detected when processing `Trait`
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error[E0391]: cycle detected when building specialization graph of trait `Trait`
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--> $DIR/coherence-inherited-assoc-ty-cycle-err.rs:8:1
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LL | trait Trait<T> { type Assoc; }
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| ^^^^^^^^^^^^^^
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= note: ...which again requires processing `Trait`, completing the cycle
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= note: ...which again requires building specialization graph of trait `Trait`, completing the cycle
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note: cycle used when coherence checking all impls of trait `Trait`
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--> $DIR/coherence-inherited-assoc-ty-cycle-err.rs:8:1
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