resolve: Pre-compute non-reexport module children

Instead of repeating the same logic by walking HIR during metadata encoding.

The only difference is that we are no longer encoding `macro_rules` items, but we never currently need them as a part of this list.
They can be encoded separately if this need ever arises.

`module_reexports` is also un-querified, because I don't see any reasons to make it a query, only overhead.

compiler/rustc_middle/src/metadata.rs

@@ -43,8 +43,6 @@ pub struct ModChild {
     pub vis: ty::Visibility<DefId>,
     /// Span of the item.
     pub span: Span,
-    /// A proper `macro_rules` item (not a reexport).
-    pub macro_rules: bool,
     /// Reexport chain linking this module child to its original reexported item.
     /// Empty if the module child is a proper item.
     pub reexport_chain: SmallVec<[Reexport; 2]>,

compiler/rustc_middle/src/query/mod.rs

@@ -1516,10 +1516,6 @@ rustc_queries! {
         desc { "getting traits in scope at a block" }
     }
 
-    query module_reexports(def_id: LocalDefId) -> &'tcx [ModChild] {
-        desc { |tcx| "looking up reexports of module `{}`", tcx.def_path_str(def_id.to_def_id()) }
-    }
-
     query impl_defaultness(def_id: DefId) -> hir::Defaultness {
         desc { |tcx| "looking up whether `{}` is a default impl", tcx.def_path_str(def_id) }
         cache_on_disk_if { def_id.is_local() }

compiler/rustc_middle/src/ty/context.rs

@@ -8,6 +8,7 @@ use crate::arena::Arena;
 use crate::dep_graph::{DepGraph, DepKindStruct};
 use crate::infer::canonical::CanonicalVarInfo;
 use crate::lint::struct_lint_level;
+use crate::metadata::ModChild;
 use crate::middle::codegen_fn_attrs::CodegenFnAttrs;
 use crate::middle::resolve_bound_vars;
 use crate::middle::stability;
@@ -2459,6 +2460,28 @@ impl<'tcx> TyCtxt<'tcx> {
             self.def_kind(def_id) == DefKind::ImplTraitPlaceholder
         }
     }
+
+    /// Named module children from all items except `use` and `extern crate` imports.
+    ///
+    /// In addition to regular items this list also includes struct or variant constructors, and
+    /// items inside `extern {}` blocks because all of them introduce names into parent module.
+    /// For non-reexported children every such name is associated with a separate `DefId`.
+    ///
+    /// Module here is understood in name resolution sense - it can be a `mod` item,
+    /// or a crate root, or an enum, or a trait.
+    pub fn module_children_non_reexports(self, def_id: LocalDefId) -> &'tcx [LocalDefId] {
+        self.resolutions(()).module_children_non_reexports.get(&def_id).map_or(&[], |v| &v[..])
+    }
+
+    /// Named module children from `use` and `extern crate` imports.
+    ///
+    /// Reexported names are not associated with individual `DefId`s,
+    /// e.g. a glob import can introduce a lot of names, all with the same `DefId`.
+    /// That's why the list needs to contain `ModChild` structures describing all the names
+    /// individually instead of `DefId`s.
+    pub fn module_children_reexports(self, def_id: LocalDefId) -> &'tcx [ModChild] {
+        self.resolutions(()).module_children_reexports.get(&def_id).map_or(&[], |v| &v[..])
+    }
 }
 
 impl<'tcx> TyCtxtAt<'tcx> {
@@ -2501,8 +2524,6 @@ pub struct DeducedParamAttrs {
 }
 
 pub fn provide(providers: &mut ty::query::Providers) {
-    providers.module_reexports =
-        |tcx, id| tcx.resolutions(()).reexport_map.get(&id).map_or(&[], |v| &v[..]);
     providers.maybe_unused_trait_imports =
         |tcx, ()| &tcx.resolutions(()).maybe_unused_trait_imports;
     providers.names_imported_by_glob_use = |tcx, id| {

compiler/rustc_middle/src/ty/mod.rs

@@ -166,7 +166,8 @@ pub struct ResolverGlobalCtxt {
     pub effective_visibilities: EffectiveVisibilities,
     pub extern_crate_map: FxHashMap<LocalDefId, CrateNum>,
     pub maybe_unused_trait_imports: FxIndexSet<LocalDefId>,
-    pub reexport_map: FxHashMap<LocalDefId, Vec<ModChild>>,
+    pub module_children_non_reexports: LocalDefIdMap<Vec<LocalDefId>>,
+    pub module_children_reexports: LocalDefIdMap<Vec<ModChild>>,
     pub glob_map: FxHashMap<LocalDefId, FxHashSet<Symbol>>,
     pub main_def: Option<MainDefinition>,
     pub trait_impls: FxIndexMap<DefId, Vec<LocalDefId>>,