rustc_metadata: Encode list of all crate's traits into metadata

compiler/rustc_metadata/src/rmeta/decoder.rs

@@ -1406,6 +1406,10 @@ impl<'a, 'tcx> CrateMetadataRef<'a> {
         )
     }
 
+    fn get_traits(&'a self) -> impl Iterator<Item = DefId> + 'a {
+        self.root.traits.decode(self).map(|index| self.local_def_id(index))
+    }
+
     fn get_implementations_for_trait(
         &self,
         tcx: TyCtxt<'tcx>,

compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs

@@ -4,9 +4,11 @@ use crate::native_libs;
 
 use rustc_ast as ast;
 use rustc_data_structures::stable_map::FxHashMap;
+use rustc_hir as hir;
 use rustc_hir::def::{CtorKind, DefKind};
 use rustc_hir::def_id::{CrateNum, DefId, DefIdMap, CRATE_DEF_INDEX, LOCAL_CRATE};
 use rustc_hir::definitions::{DefKey, DefPath, DefPathHash};
+use rustc_hir::itemlikevisit::ItemLikeVisitor;
 use rustc_middle::hir::exports::Export;
 use rustc_middle::middle::exported_symbols::ExportedSymbol;
 use rustc_middle::middle::stability::DeprecationEntry;
@@ -195,6 +197,8 @@ provide! { <'tcx> tcx, def_id, other, cdata,
 
     extra_filename => { cdata.root.extra_filename.clone() }
 
+    traits_in_crate => { tcx.arena.alloc_from_iter(cdata.get_traits()) }
+
     implementations_of_trait => {
         cdata.get_implementations_for_trait(tcx, Some(other))
     }
@@ -285,6 +289,28 @@ pub fn provide(providers: &mut Providers) {
                 foreign_modules::collect(tcx).into_iter().map(|m| (m.def_id, m)).collect();
             Lrc::new(modules)
         },
+        traits_in_crate: |tcx, cnum| {
+            assert_eq!(cnum, LOCAL_CRATE);
+
+            #[derive(Default)]
+            struct TraitsVisitor {
+                traits: Vec<DefId>,
+            }
+            impl ItemLikeVisitor<'_> for TraitsVisitor {
+                fn visit_item(&mut self, item: &hir::Item<'_>) {
+                    if let hir::ItemKind::Trait(..) | hir::ItemKind::TraitAlias(..) = item.kind {
+                        self.traits.push(item.def_id.to_def_id());
+                    }
+                }
+                fn visit_trait_item(&mut self, _trait_item: &hir::TraitItem<'_>) {}
+                fn visit_impl_item(&mut self, _impl_item: &hir::ImplItem<'_>) {}
+                fn visit_foreign_item(&mut self, _foreign_item: &hir::ForeignItem<'_>) {}
+            }
+
+            let mut visitor = TraitsVisitor::default();
+            tcx.hir().visit_all_item_likes(&mut visitor);
+            tcx.arena.alloc_slice(&visitor.traits)
+        },
 
         // 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

compiler/rustc_metadata/src/rmeta/encoder.rs

@@ -614,8 +614,8 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
 
         // Encode the def IDs of impls, for coherence checking.
         i = self.position();
-        let impls = self.encode_impls();
-        let impl_bytes = self.position() - i;
+        let (traits, impls) = self.encode_traits_and_impls();
+        let traits_and_impls_bytes = self.position() - i;
 
         let tcx = self.tcx;
 
@@ -727,6 +727,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
             foreign_modules,
             source_map,
             impls,
+            traits,
             exported_symbols,
             interpret_alloc_index,
             tables,
@@ -753,7 +754,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
             eprintln!(" diagnostic item bytes: {}", diagnostic_item_bytes);
             eprintln!("          native bytes: {}", native_lib_bytes);
             eprintln!("      source_map bytes: {}", source_map_bytes);
-            eprintln!("            impl bytes: {}", impl_bytes);
+            eprintln!("traits and impls bytes: {}", traits_and_impls_bytes);
             eprintln!("    exp. symbols bytes: {}", exported_symbols_bytes);
             eprintln!("  def-path table bytes: {}", def_path_table_bytes);
             eprintln!(" def-path hashes bytes: {}", def_path_hash_map_bytes);
@@ -1784,16 +1785,23 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
     }
 
     /// Encodes an index, mapping each trait to its (local) implementations.
-    fn encode_impls(&mut self) -> Lazy<[TraitImpls]> {
-        empty_proc_macro!(self);
-        debug!("EncodeContext::encode_impls()");
+    fn encode_traits_and_impls(&mut self) -> (Lazy<[DefIndex]>, Lazy<[TraitImpls]>) {
+        if self.is_proc_macro {
+            return (Lazy::empty(), Lazy::empty());
+        }
+        debug!("EncodeContext::encode_traits_and_impls()");
         let tcx = self.tcx;
-        let mut visitor = ImplVisitor { tcx, impls: FxHashMap::default() };
+        let mut visitor =
+            TraitsAndImplsVisitor { tcx, impls: FxHashMap::default(), traits: Default::default() };
         tcx.hir().visit_all_item_likes(&mut visitor);
 
+        let mut all_traits = visitor.traits;
         let mut all_impls: Vec<_> = visitor.impls.into_iter().collect();
 
         // Bring everything into deterministic order for hashing
+        all_traits.sort_by_cached_key(|&local_def_index| {
+            tcx.hir().def_path_hash(LocalDefId { local_def_index })
+        });
         all_impls.sort_by_cached_key(|&(trait_def_id, _)| tcx.def_path_hash(trait_def_id));
 
         let all_impls: Vec<_> = all_impls
@@ -1811,7 +1819,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
             })
             .collect();
 
-        self.lazy(&all_impls)
+        (self.lazy(&all_traits), self.lazy(&all_impls))
     }
 
     // Encodes all symbols exported from this crate into the metadata.
@@ -2033,27 +2041,34 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
     }
 }
 
-struct ImplVisitor<'tcx> {
+struct TraitsAndImplsVisitor<'tcx> {
     tcx: TyCtxt<'tcx>,
+    traits: Vec<DefIndex>,
     impls: FxHashMap<DefId, Vec<(DefIndex, Option<fast_reject::SimplifiedType>)>>,
 }
 
-impl<'tcx, 'v> ItemLikeVisitor<'v> for ImplVisitor<'tcx> {
+impl<'tcx, 'v> ItemLikeVisitor<'v> for TraitsAndImplsVisitor<'tcx> {
     fn visit_item(&mut self, item: &hir::Item<'_>) {
-        if let hir::ItemKind::Impl { .. } = item.kind {
-            if let Some(trait_ref) = self.tcx.impl_trait_ref(item.def_id.to_def_id()) {
-                let simplified_self_ty = fast_reject::simplify_type(
-                    self.tcx,
-                    trait_ref.self_ty(),
-                    SimplifyParams::No,
-                    StripReferences::No,
-                );
+        match item.kind {
+            hir::ItemKind::Trait(..) | hir::ItemKind::TraitAlias(..) => {
+                self.traits.push(item.def_id.local_def_index);
+            }
+            hir::ItemKind::Impl(..) => {
+                if let Some(trait_ref) = self.tcx.impl_trait_ref(item.def_id.to_def_id()) {
+                    let simplified_self_ty = fast_reject::simplify_type(
+                        self.tcx,
+                        trait_ref.self_ty(),
+                        SimplifyParams::No,
+                        StripReferences::No,
+                    );
 
-                self.impls
-                    .entry(trait_ref.def_id)
-                    .or_default()
-                    .push((item.def_id.local_def_index, simplified_self_ty));
+                    self.impls
+                        .entry(trait_ref.def_id)
+                        .or_default()
+                        .push((item.def_id.local_def_index, simplified_self_ty));
+                }
             }
+            _ => {}
         }
     }
 

compiler/rustc_metadata/src/rmeta/mod.rs

@@ -222,6 +222,7 @@ crate struct CrateRoot<'tcx> {
     diagnostic_items: Lazy<[(Symbol, DefIndex)]>,
     native_libraries: Lazy<[NativeLib]>,
     foreign_modules: Lazy<[ForeignModule]>,
+    traits: Lazy<[DefIndex]>,
     impls: Lazy<[TraitImpls]>,
     interpret_alloc_index: Lazy<[u32]>,
     proc_macro_data: Option<ProcMacroData>,

compiler/rustc_middle/src/query/mod.rs

@@ -1609,11 +1609,11 @@ rustc_queries! {
         desc { "fetching all foreign CrateNum instances" }
     }
 
-    /// A vector of every trait accessible in the whole crate
-    /// (i.e., including those from subcrates). This is used only for
-    /// error reporting.
-    query all_traits(_: ()) -> &'tcx [DefId] {
-        desc { "fetching all foreign and local traits" }
+    /// A list of all traits in a crate, used by rustdoc and error reporting.
+    /// NOTE: Not named just `traits` due to a naming conflict.
+    query traits_in_crate(_: CrateNum) -> &'tcx [DefId] {
+        desc { "fetching all traits in a crate" }
+        separate_provide_extern
     }
 
     /// The list of symbols exported from the given crate.

compiler/rustc_middle/src/ty/context.rs

@@ -1577,6 +1577,12 @@ impl<'tcx> TyCtxt<'tcx> {
     pub fn const_eval_limit(self) -> Limit {
         self.limits(()).const_eval_limit
     }
+
+    pub fn all_traits(self) -> impl Iterator<Item = DefId> + 'tcx {
+        iter::once(LOCAL_CRATE)
+            .chain(self.crates(()).iter().copied())
+            .flat_map(move |cnum| self.traits_in_crate(cnum).iter().copied())
+    }
 }
 
 /// A trait implemented for all `X<'a>` types that can be safely and

compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs

@@ -1567,14 +1567,14 @@ impl<'a, 'tcx> InferCtxtPrivExt<'a, 'tcx> for InferCtxt<'a, 'tcx> {
             self.tcx.find_map_relevant_impl(trait_def_id, trait_ref.skip_binder().self_ty(), Some)
         };
         let required_trait_path = self.tcx.def_path_str(trait_ref.def_id());
-        let all_traits = self.tcx.all_traits(());
-        let traits_with_same_path: std::collections::BTreeSet<_> = all_traits
-            .iter()
-            .filter(|trait_def_id| **trait_def_id != trait_ref.def_id())
-            .filter(|trait_def_id| self.tcx.def_path_str(**trait_def_id) == required_trait_path)
+        let traits_with_same_path: std::collections::BTreeSet<_> = self
+            .tcx
+            .all_traits()
+            .filter(|trait_def_id| *trait_def_id != trait_ref.def_id())
+            .filter(|trait_def_id| self.tcx.def_path_str(*trait_def_id) == required_trait_path)
             .collect();
         for trait_with_same_path in traits_with_same_path {
-            if let Some(impl_def_id) = get_trait_impl(*trait_with_same_path) {
+            if let Some(impl_def_id) = get_trait_impl(trait_with_same_path) {
                 let impl_span = self.tcx.def_span(impl_def_id);
                 err.span_help(impl_span, "trait impl with same name found");
                 let trait_crate = self.tcx.crate_name(trait_with_same_path.krate);

compiler/rustc_typeck/src/check/method/mod.rs

@@ -7,7 +7,7 @@ mod prelude2021;
 pub mod probe;
 mod suggest;
 
-pub use self::suggest::{SelfSource, TraitInfo};
+pub use self::suggest::SelfSource;
 pub use self::CandidateSource::*;
 pub use self::MethodError::*;
 
@@ -31,7 +31,6 @@ use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt;
 use self::probe::{IsSuggestion, ProbeScope};
 
 pub fn provide(providers: &mut ty::query::Providers) {
-    suggest::provide(providers);
     probe::provide(providers);
 }
 

compiler/rustc_typeck/src/check/method/suggest.rs

@@ -5,8 +5,8 @@ use crate::check::FnCtxt;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_errors::{pluralize, struct_span_err, Applicability, DiagnosticBuilder};
 use rustc_hir as hir;
-use rustc_hir::def::{DefKind, Namespace, Res};
-use rustc_hir::def_id::{DefId, LocalDefId, CRATE_DEF_INDEX};
+use rustc_hir::def::Namespace;
+use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_hir::lang_items::LangItem;
 use rustc_hir::{ExprKind, Node, QPath};
 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
@@ -1922,76 +1922,10 @@ impl Ord for TraitInfo {
     }
 }
 
-/// Retrieves all traits in this crate and any dependent crates.
+/// Retrieves all traits in this crate and any dependent crates,
+/// and wraps them into `TraitInfo` for custom sorting.
 pub fn all_traits(tcx: TyCtxt<'_>) -> Vec<TraitInfo> {
-    tcx.all_traits(()).iter().map(|&def_id| TraitInfo { def_id }).collect()
-}
-
-/// Computes all traits in this crate and any dependent crates.
-fn compute_all_traits(tcx: TyCtxt<'_>, (): ()) -> &[DefId] {
-    use hir::itemlikevisit;
-
-    let mut traits = vec![];
-
-    // Crate-local:
-
-    struct Visitor<'a> {
-        traits: &'a mut Vec<DefId>,
-    }
-
-    impl<'v, 'a> itemlikevisit::ItemLikeVisitor<'v> for Visitor<'a> {
-        fn visit_item(&mut self, i: &'v hir::Item<'v>) {
-            match i.kind {
-                hir::ItemKind::Trait(..) | hir::ItemKind::TraitAlias(..) => {
-                    self.traits.push(i.def_id.to_def_id());
-                }
-                _ => (),
-            }
-        }
-
-        fn visit_trait_item(&mut self, _trait_item: &hir::TraitItem<'_>) {}
-
-        fn visit_impl_item(&mut self, _impl_item: &hir::ImplItem<'_>) {}
-
-        fn visit_foreign_item(&mut self, _foreign_item: &hir::ForeignItem<'_>) {}
-    }
-
-    tcx.hir().visit_all_item_likes(&mut Visitor { traits: &mut traits });
-
-    // Cross-crate:
-
-    let mut external_mods = FxHashSet::default();
-    fn handle_external_res(
-        tcx: TyCtxt<'_>,
-        traits: &mut Vec<DefId>,
-        external_mods: &mut FxHashSet<DefId>,
-        res: Res<!>,
-    ) {
-        match res {
-            Res::Def(DefKind::Trait | DefKind::TraitAlias, def_id) => {
-                traits.push(def_id);
-            }
-            Res::Def(DefKind::Mod, def_id) => {
-                if !external_mods.insert(def_id) {
-                    return;
-                }
-                for child in tcx.item_children(def_id).iter() {
-                    handle_external_res(tcx, traits, external_mods, child.res)
-                }
-            }
-            _ => {}
-        }
-    }
-    for &cnum in tcx.crates(()).iter() {
-        let def_id = DefId { krate: cnum, index: CRATE_DEF_INDEX };
-        handle_external_res(tcx, &mut traits, &mut external_mods, Res::Def(DefKind::Mod, def_id));
-    }
-
-    tcx.arena.alloc_from_iter(traits)
-}
-
-pub fn provide(providers: &mut ty::query::Providers) {
-    providers.all_traits = compute_all_traits;
+    tcx.all_traits().map(|def_id| TraitInfo { def_id }).collect()
 }
 
 fn find_use_placement<'tcx>(tcx: TyCtxt<'tcx>, target_module: LocalDefId) -> (Option<Span>, bool) {

src/librustdoc/clean/blanket_impl.rs

@@ -19,7 +19,7 @@ impl<'a, 'tcx> BlanketImplFinder<'a, 'tcx> {
 
         trace!("get_blanket_impls({:?})", ty);
         let mut impls = Vec::new();
-        for &trait_def_id in self.cx.tcx.all_traits(()).iter() {
+        for trait_def_id in self.cx.tcx.all_traits() {
             if !self.cx.cache.access_levels.is_public(trait_def_id)
                 || self.cx.generated_synthetics.get(&(ty, trait_def_id)).is_some()
             {

src/librustdoc/core.rs

@@ -369,10 +369,8 @@ crate fn run_global_ctxt(
         impl_trait_bounds: Default::default(),
         generated_synthetics: Default::default(),
         auto_traits: tcx
-            .all_traits(())
-            .iter()
-            .cloned()
-            .filter(|trait_def_id| tcx.trait_is_auto(*trait_def_id))
+            .all_traits()
+            .filter(|&trait_def_id| tcx.trait_is_auto(trait_def_id))
             .collect(),
         module_trait_cache: FxHashMap::default(),
         cache: Cache::new(access_levels, render_options.document_private),

src/librustdoc/passes/collect_trait_impls.rs

@@ -129,7 +129,7 @@ crate fn collect_trait_impls(mut krate: Crate, cx: &mut DocContext<'_>) -> Crate
     // `tcx.crates(())` doesn't include the local crate, and `tcx.all_trait_implementations`
     // doesn't work with it anyway, so pull them from the HIR map instead
     let mut extra_attrs = Vec::new();
-    for &trait_did in cx.tcx.all_traits(()).iter() {
+    for trait_did in cx.tcx.all_traits() {
         for &impl_did in cx.tcx.hir().trait_impls(trait_did) {
             let impl_did = impl_did.to_def_id();
             cx.tcx.sess.prof.generic_activity("build_local_trait_impl").run(|| {