Only compute the trait_map once.

compiler/rustc_ast_lowering/src/lib.rs

@@ -43,7 +43,8 @@
 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::stable_hasher::StableVec;
 use rustc_data_structures::sync::Lrc;
 use rustc_errors::{struct_span_err, Applicability};
 use rustc_hir as hir;
@@ -198,7 +199,7 @@ pub trait ResolverAstLowering {
 
     fn next_node_id(&mut self) -> NodeId;
 
-    fn trait_map(&self) -> &NodeMap<Vec<hir::TraitCandidate>>;
+    fn trait_map(&mut self) -> NodeMap<Vec<hir::TraitCandidate>>;
 
     fn opt_local_def_id(&self, node: NodeId) -> Option<LocalDefId>;
 
@@ -501,14 +502,13 @@ fn visit_ty(&mut self, t: &'tcx Ty) {
         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.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, StableVec::new(v.to_vec()));
+            }
+        }
 
         let mut def_id_to_hir_id = IndexVec::default();
 

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 +10,8 @@
 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::stable_hasher::StableVec;
 use rustc_data_structures::sync::{par_for_each_in, Send, Sync};
 use rustc_macros::HashStable_Generic;
 use rustc_span::source_map::Spanned;
@@ -658,7 +660,9 @@ 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, StableVec<TraitCandidate>>>,
 
     /// Collected attributes from HIR nodes.
     pub attrs: BTreeMap<HirId, &'hir [Attribute]>,

compiler/rustc_middle/src/query/mod.rs

@@ -1128,7 +1128,6 @@
     }
     query in_scope_traits_map(_: LocalDefId)
         -> Option<&'tcx FxHashMap<ItemLocalId, StableVec<TraitCandidate>>> {
-        eval_always
         desc { "traits in scope at a block" }
     }
 

compiler/rustc_middle/src/ty/context.rs

@@ -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 @@ pub fn create_global_ctxt(
         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 @@ pub fn create_global_ctxt(
             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,
@@ -2793,7 +2782,7 @@ 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_resolve/src/lib.rs

@@ -1138,8 +1138,8 @@ fn next_node_id(&mut self) -> NodeId {
         self.next_node_id()
     }
 
-    fn trait_map(&self) -> &NodeMap<Vec<TraitCandidate>> {
-        &self.trait_map
+    fn trait_map(&mut self) -> NodeMap<Vec<TraitCandidate>> {
+        std::mem::take(&mut self.trait_map)
     }
 
     fn opt_local_def_id(&self, node: NodeId) -> Option<LocalDefId> {