Only compute the trait map once

compiler/rustc_ast_lowering/src/lib.rs

@@ -43,7 +43,7 @@ use rustc_ast::walk_list;
 use rustc_ast::{self as ast, *};
 use rustc_ast_pretty::pprust;
 use rustc_data_structures::captures::Captures;
-use rustc_data_structures::fx::FxHashSet;
+use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_data_structures::sync::Lrc;
 use rustc_errors::{struct_span_err, Applicability};
 use rustc_hir as hir;
@@ -198,7 +198,7 @@ pub trait ResolverAstLowering {
 
     fn next_node_id(&mut self) -> NodeId;
 
-    fn trait_map(&self) -> &NodeMap<Vec<hir::TraitCandidate>>;
+    fn take_trait_map(&mut self) -> NodeMap<Vec<hir::TraitCandidate>>;
 
     fn opt_local_def_id(&self, node: NodeId) -> Option<LocalDefId>;
 
@@ -501,14 +501,13 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         let proc_macros =
             c.proc_macros.iter().map(|id| self.node_id_to_hir_id[*id].unwrap()).collect();
 
-        let trait_map = self
-            .resolver
-            .trait_map()
-            .iter()
-            .filter_map(|(&k, v)| {
-                self.node_id_to_hir_id.get(k).and_then(|id| id.as_ref()).map(|id| (*id, v.clone()))
-            })
-            .collect();
+        let mut trait_map: FxHashMap<_, FxHashMap<_, _>> = FxHashMap::default();
+        for (k, v) in self.resolver.take_trait_map().into_iter() {
+            if let Some(Some(hir_id)) = self.node_id_to_hir_id.get(k) {
+                let map = trait_map.entry(hir_id.owner).or_default();
+                map.insert(hir_id.local_id, v.into_boxed_slice());
+            }
+        }
 
         let mut def_id_to_hir_id = IndexVec::default();
 

compiler/rustc_data_structures/src/stable_hasher.rs

@@ -550,35 +550,3 @@ pub fn hash_stable_hashmap<HCX, K, V, R, SK, F>(
     entries.sort_unstable_by(|&(ref sk1, _), &(ref sk2, _)| sk1.cmp(sk2));
     entries.hash_stable(hcx, hasher);
 }
-
-/// A vector container that makes sure that its items are hashed in a stable
-/// order.
-#[derive(Debug)]
-pub struct StableVec<T>(Vec<T>);
-
-impl<T> StableVec<T> {
-    pub fn new(v: Vec<T>) -> Self {
-        StableVec(v)
-    }
-}
-
-impl<T> ::std::ops::Deref for StableVec<T> {
-    type Target = Vec<T>;
-
-    fn deref(&self) -> &Vec<T> {
-        &self.0
-    }
-}
-
-impl<T, HCX> HashStable<HCX> for StableVec<T>
-where
-    T: HashStable<HCX> + ToStableHashKey<HCX>,
-{
-    fn hash_stable(&self, hcx: &mut HCX, hasher: &mut StableHasher) {
-        let StableVec(ref v) = *self;
-
-        let mut sorted: Vec<_> = v.iter().map(|x| x.to_stable_hash_key(hcx)).collect();
-        sorted.sort_unstable();
-        sorted.hash_stable(hcx, hasher);
-    }
-}

compiler/rustc_hir/src/hir.rs

@@ -1,7 +1,7 @@
 // ignore-tidy-filelength
 use crate::def::{CtorKind, DefKind, Res};
 use crate::def_id::DefId;
-crate use crate::hir_id::HirId;
+crate use crate::hir_id::{HirId, ItemLocalId};
 use crate::{itemlikevisit, LangItem};
 
 use rustc_ast::util::parser::ExprPrecedence;
@@ -10,6 +10,7 @@ use rustc_ast::{Attribute, FloatTy, IntTy, Label, LitKind, StrStyle, TraitObject
 pub use rustc_ast::{BorrowKind, ImplPolarity, IsAuto};
 pub use rustc_ast::{CaptureBy, Movability, Mutability};
 use rustc_ast::{InlineAsmOptions, InlineAsmTemplatePiece};
+use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::sync::{par_for_each_in, Send, Sync};
 use rustc_macros::HashStable_Generic;
 use rustc_span::source_map::Spanned;
@@ -658,7 +659,9 @@ pub struct Crate<'hir> {
     /// they are declared in the static array generated by proc_macro_harness.
     pub proc_macros: Vec<HirId>,
 
-    pub trait_map: BTreeMap<HirId, Vec<TraitCandidate>>,
+    /// Map indicating what traits are in scope for places where this
+    /// is relevant; generated by resolve.
+    pub trait_map: FxHashMap<LocalDefId, FxHashMap<ItemLocalId, Box<[TraitCandidate]>>>,
 
     /// Collected attributes from HIR nodes.
     pub attrs: BTreeMap<HirId, &'hir [Attribute]>,

compiler/rustc_middle/src/query/mod.rs

@@ -1127,8 +1127,7 @@ rustc_queries! {
         desc { "computing whether impls specialize one another" }
     }
     query in_scope_traits_map(_: LocalDefId)
-        -> Option<&'tcx FxHashMap<ItemLocalId, StableVec<TraitCandidate>>> {
-        eval_always
+        -> Option<&'tcx FxHashMap<ItemLocalId, Box<[TraitCandidate]>>> {
         desc { "traits in scope at a block" }
     }
 

compiler/rustc_middle/src/ty/context.rs

@@ -31,7 +31,7 @@ use rustc_attr as attr;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_data_structures::profiling::SelfProfilerRef;
 use rustc_data_structures::sharded::{IntoPointer, ShardedHashMap};
-use rustc_data_structures::stable_hasher::{HashStable, StableHasher, StableVec};
+use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_data_structures::steal::Steal;
 use rustc_data_structures::sync::{self, Lock, Lrc, WorkerLocal};
 use rustc_errors::ErrorReported;
@@ -966,10 +966,6 @@ pub struct GlobalCtxt<'tcx> {
     /// Resolutions of `extern crate` items produced by resolver.
     extern_crate_map: FxHashMap<LocalDefId, CrateNum>,
 
-    /// Map indicating what traits are in scope for places where this
-    /// is relevant; generated by resolve.
-    trait_map: FxHashMap<LocalDefId, FxHashMap<ItemLocalId, StableVec<TraitCandidate>>>,
-
     /// Export map produced by name resolution.
     export_map: ExportMap<LocalDefId>,
 
@@ -1150,12 +1146,6 @@ impl<'tcx> TyCtxt<'tcx> {
         let common_consts = CommonConsts::new(&interners, &common_types);
         let cstore = resolutions.cstore;
 
-        let mut trait_map: FxHashMap<_, FxHashMap<_, _>> = FxHashMap::default();
-        for (hir_id, v) in krate.trait_map.iter() {
-            let map = trait_map.entry(hir_id.owner).or_default();
-            map.insert(hir_id.local_id, StableVec::new(v.to_vec()));
-        }
-
         GlobalCtxt {
             sess: s,
             lint_store,
@@ -1169,7 +1159,6 @@ impl<'tcx> TyCtxt<'tcx> {
             consts: common_consts,
             visibilities: resolutions.visibilities,
             extern_crate_map: resolutions.extern_crate_map,
-            trait_map,
             export_map: resolutions.export_map,
             maybe_unused_trait_imports: resolutions.maybe_unused_trait_imports,
             maybe_unused_extern_crates: resolutions.maybe_unused_extern_crates,
@@ -2662,8 +2651,10 @@ impl<'tcx> TyCtxt<'tcx> {
         struct_lint_level(self.sess, lint, level, src, None, decorate);
     }
 
-    pub fn in_scope_traits(self, id: HirId) -> Option<&'tcx StableVec<TraitCandidate>> {
-        self.in_scope_traits_map(id.owner).and_then(|map| map.get(&id.local_id))
+    pub fn in_scope_traits(self, id: HirId) -> Option<&'tcx [TraitCandidate]> {
+        let map = self.in_scope_traits_map(id.owner)?;
+        let candidates = map.get(&id.local_id)?;
+        Some(&*candidates)
     }
 
     pub fn named_region(self, id: HirId) -> Option<resolve_lifetime::Region> {
@@ -2793,7 +2784,7 @@ fn ptr_eq<T, U>(t: *const T, u: *const U) -> bool {
 }
 
 pub fn provide(providers: &mut ty::query::Providers) {
-    providers.in_scope_traits_map = |tcx, id| tcx.gcx.trait_map.get(&id);
+    providers.in_scope_traits_map = |tcx, id| tcx.hir_crate(()).trait_map.get(&id);
     providers.module_exports = |tcx, id| tcx.gcx.export_map.get(&id).map(|v| &v[..]);
     providers.crate_name = |tcx, id| {
         assert_eq!(id, LOCAL_CRATE);

compiler/rustc_middle/src/ty/query/mod.rs

@@ -34,7 +34,6 @@ use crate::ty::subst::{GenericArg, SubstsRef};
 use crate::ty::util::AlwaysRequiresDrop;
 use crate::ty::{self, AdtSizedConstraint, CrateInherentImpls, ParamEnvAnd, Ty, TyCtxt};
 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap};
-use rustc_data_structures::stable_hasher::StableVec;
 use rustc_data_structures::steal::Steal;
 use rustc_data_structures::svh::Svh;
 use rustc_data_structures::sync::Lrc;

compiler/rustc_resolve/src/lib.rs

@@ -910,6 +910,8 @@ pub struct Resolver<'a> {
     extern_crate_map: FxHashMap<LocalDefId, CrateNum>,
     export_map: ExportMap<LocalDefId>,
     trait_map: NodeMap<Vec<TraitCandidate>>,
+    #[cfg(debug_assertions)]
+    took_trait_map: bool,
 
     /// A map from nodes to anonymous modules.
     /// Anonymous modules are pseudo-modules that are implicitly created around items
@@ -1138,8 +1140,13 @@ impl ResolverAstLowering for Resolver<'_> {
         self.next_node_id()
     }
 
-    fn trait_map(&self) -> &NodeMap<Vec<TraitCandidate>> {
-        &self.trait_map
+    fn take_trait_map(&mut self) -> NodeMap<Vec<TraitCandidate>> {
+        #[cfg(debug_assertions)]
+        {
+            debug_assert!(!self.took_trait_map);
+            self.took_trait_map = true;
+        }
+        std::mem::take(&mut self.trait_map)
     }
 
     fn opt_local_def_id(&self, node: NodeId) -> Option<LocalDefId> {
@@ -1287,6 +1294,8 @@ impl<'a> Resolver<'a> {
             extern_crate_map: Default::default(),
             export_map: FxHashMap::default(),
             trait_map: Default::default(),
+            #[cfg(debug_assertions)]
+            took_trait_map: false,
             underscore_disambiguator: 0,
             empty_module,
             module_map,