From 294510e1bb7e03bd462f6a6db2fab5f56fae1c8c Mon Sep 17 00:00:00 2001
From: Vadim Petrochenkov <vadim.petrochenkov@gmail.com>
Date: Sun, 5 Sep 2021 23:37:15 +0300
Subject: [PATCH] rustc: Remove local variable IDs from `Export`s

Local variables can never be exported.
---
 compiler/rustc_data_structures/src/lib.rs     |  1 +
 .../src/stable_hasher.rs                      |  6 +++
 compiler/rustc_hir/src/def.rs                 |  5 +++
 compiler/rustc_metadata/src/rmeta/decoder.rs  |  5 +--
 .../src/rmeta/decoder/cstore_impl.rs          | 40 ++++++++-----------
 compiler/rustc_metadata/src/rmeta/encoder.rs  |  9 +----
 compiler/rustc_metadata/src/rmeta/mod.rs      |  2 +-
 compiler/rustc_middle/src/hir/exports.rs      | 13 ++----
 compiler/rustc_middle/src/query/mod.rs        |  4 +-
 compiler/rustc_middle/src/ty/mod.rs           |  2 +-
 .../rustc_resolve/src/build_reduced_graph.rs  |  4 +-
 compiler/rustc_resolve/src/imports.rs         |  5 +--
 compiler/rustc_resolve/src/lib.rs             |  3 +-
 compiler/rustc_serialize/src/serialize.rs     | 12 ++++++
 .../rustc_typeck/src/check/method/suggest.rs  |  2 +-
 src/librustdoc/clean/inline.rs                | 11 +++--
 src/librustdoc/clean/types.rs                 |  9 +++--
 src/librustdoc/visit_lib.rs                   |  2 +-
 src/tools/clippy/clippy_utils/src/lib.rs      |  4 +-
 19 files changed, 71 insertions(+), 68 deletions(-)

diff --git a/compiler/rustc_data_structures/src/lib.rs b/compiler/rustc_data_structures/src/lib.rs
index d128a688e75..dd6a17b92ae 100644
--- a/compiler/rustc_data_structures/src/lib.rs
+++ b/compiler/rustc_data_structures/src/lib.rs
@@ -21,6 +21,7 @@
 #![feature(iter_map_while)]
 #![feature(maybe_uninit_uninit_array)]
 #![feature(min_specialization)]
+#![feature(never_type)]
 #![feature(type_alias_impl_trait)]
 #![feature(new_uninit)]
 #![feature(nll)]
diff --git a/compiler/rustc_data_structures/src/stable_hasher.rs b/compiler/rustc_data_structures/src/stable_hasher.rs
index 18b352cf3b0..354f9dd93cc 100644
--- a/compiler/rustc_data_structures/src/stable_hasher.rs
+++ b/compiler/rustc_data_structures/src/stable_hasher.rs
@@ -209,6 +209,12 @@ impl_stable_hash_via_hash!(i128);
 impl_stable_hash_via_hash!(char);
 impl_stable_hash_via_hash!(());
 
+impl<CTX> HashStable<CTX> for ! {
+    fn hash_stable(&self, _ctx: &mut CTX, _hasher: &mut StableHasher) {
+        unreachable!()
+    }
+}
+
 impl<CTX> HashStable<CTX> for ::std::num::NonZeroU32 {
     fn hash_stable(&self, ctx: &mut CTX, hasher: &mut StableHasher) {
         self.get().hash_stable(ctx, hasher)
diff --git a/compiler/rustc_hir/src/def.rs b/compiler/rustc_hir/src/def.rs
index 853415c4173..cb668eb35e0 100644
--- a/compiler/rustc_hir/src/def.rs
+++ b/compiler/rustc_hir/src/def.rs
@@ -598,6 +598,11 @@ impl<Id> Res<Id> {
         }
     }
 
+    #[track_caller]
+    pub fn expect_non_local<OtherId>(self) -> Res<OtherId> {
+        self.map_id(|_| panic!("unexpected `Res::Local`"))
+    }
+
     pub fn macro_kind(self) -> Option<MacroKind> {
         match self {
             Res::Def(DefKind::Macro(kind), _) => Some(kind),
diff --git a/compiler/rustc_metadata/src/rmeta/decoder.rs b/compiler/rustc_metadata/src/rmeta/decoder.rs
index dd44e0cb1fa..0c284269c2f 100644
--- a/compiler/rustc_metadata/src/rmeta/decoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/decoder.rs
@@ -1019,10 +1019,7 @@ impl<'a, 'tcx> CrateMetadataRef<'a> {
     }
 
     /// Iterates over each child of the given item.
-    fn each_child_of_item<F>(&self, id: DefIndex, mut callback: F, sess: &Session)
-    where
-        F: FnMut(Export<hir::HirId>),
-    {
+    fn each_child_of_item(&self, id: DefIndex, mut callback: impl FnMut(Export), sess: &Session) {
         if let Some(data) = &self.root.proc_macro_data {
             /* If we are loading as a proc macro, we want to return the view of this crate
              * as a proc macro crate.
diff --git a/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs b/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
index 41839c58021..80341b16e14 100644
--- a/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
+++ b/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
@@ -5,7 +5,6 @@ use crate::rmeta::encoder;
 
 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};
@@ -326,28 +325,27 @@ pub fn provide(providers: &mut Providers) {
             // (restrict scope of mutable-borrow of `visible_parent_map`)
             {
                 let visible_parent_map = &mut visible_parent_map;
-                let mut add_child =
-                    |bfs_queue: &mut VecDeque<_>, child: &Export<hir::HirId>, parent: DefId| {
-                        if child.vis != ty::Visibility::Public {
-                            return;
-                        }
+                let mut add_child = |bfs_queue: &mut VecDeque<_>, child: &Export, parent: DefId| {
+                    if child.vis != ty::Visibility::Public {
+                        return;
+                    }
 
-                        if let Some(child) = child.res.opt_def_id() {
-                            match visible_parent_map.entry(child) {
-                                Entry::Occupied(mut entry) => {
-                                    // If `child` is defined in crate `cnum`, ensure
-                                    // that it is mapped to a parent in `cnum`.
-                                    if child.is_local() && entry.get().is_local() {
-                                        entry.insert(parent);
-                                    }
-                                }
-                                Entry::Vacant(entry) => {
+                    if let Some(child) = child.res.opt_def_id() {
+                        match visible_parent_map.entry(child) {
+                            Entry::Occupied(mut entry) => {
+                                // If `child` is defined in crate `cnum`, ensure
+                                // that it is mapped to a parent in `cnum`.
+                                if child.is_local() && entry.get().is_local() {
                                     entry.insert(parent);
-                                    bfs_queue.push_back(child);
                                 }
                             }
+                            Entry::Vacant(entry) => {
+                                entry.insert(parent);
+                                bfs_queue.push_back(child);
+                            }
                         }
-                    };
+                    }
+                };
 
                 while let Some(def) = bfs_queue.pop_front() {
                     for child in tcx.item_children(def).iter() {
@@ -393,11 +391,7 @@ impl CStore {
         self.get_crate_data(def.krate).get_visibility(def.index)
     }
 
-    pub fn item_children_untracked(
-        &self,
-        def_id: DefId,
-        sess: &Session,
-    ) -> Vec<Export<hir::HirId>> {
+    pub fn item_children_untracked(&self, def_id: DefId, sess: &Session) -> Vec<Export> {
         let mut result = vec![];
         self.get_crate_data(def_id.krate).each_child_of_item(
             def_id.index,
diff --git a/compiler/rustc_metadata/src/rmeta/encoder.rs b/compiler/rustc_metadata/src/rmeta/encoder.rs
index d8b9a479976..52c6193940d 100644
--- a/compiler/rustc_metadata/src/rmeta/encoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/encoder.rs
@@ -1065,14 +1065,7 @@ impl EncodeContext<'a, 'tcx> {
         // items - we encode information about proc-macros later on.
         let reexports = if !self.is_proc_macro {
             match tcx.module_exports(local_def_id) {
-                Some(exports) => {
-                    let hir = self.tcx.hir();
-                    self.lazy(
-                        exports
-                            .iter()
-                            .map(|export| export.map_id(|id| hir.local_def_id_to_hir_id(id))),
-                    )
-                }
+                Some(exports) => self.lazy(exports),
                 _ => Lazy::empty(),
             }
         } else {
diff --git a/compiler/rustc_metadata/src/rmeta/mod.rs b/compiler/rustc_metadata/src/rmeta/mod.rs
index a487753f462..fe0bf5b64ba 100644
--- a/compiler/rustc_metadata/src/rmeta/mod.rs
+++ b/compiler/rustc_metadata/src/rmeta/mod.rs
@@ -359,7 +359,7 @@ struct RenderedConst(String);
 
 #[derive(MetadataEncodable, MetadataDecodable)]
 struct ModData {
-    reexports: Lazy<[Export<hir::HirId>]>,
+    reexports: Lazy<[Export]>,
     expansion: ExpnId,
 }
 
diff --git a/compiler/rustc_middle/src/hir/exports.rs b/compiler/rustc_middle/src/hir/exports.rs
index be9e38aca65..f37b976fba6 100644
--- a/compiler/rustc_middle/src/hir/exports.rs
+++ b/compiler/rustc_middle/src/hir/exports.rs
@@ -11,23 +11,18 @@ use std::fmt::Debug;
 
 /// This is the replacement export map. It maps a module to all of the exports
 /// within.
-pub type ExportMap<Id> = FxHashMap<LocalDefId, Vec<Export<Id>>>;
+pub type ExportMap = FxHashMap<LocalDefId, Vec<Export>>;
 
 #[derive(Copy, Clone, Debug, TyEncodable, TyDecodable, HashStable)]
-pub struct Export<Id> {
+pub struct Export {
     /// The name of the target.
     pub ident: Ident,
     /// The resolution of the target.
-    pub res: Res<Id>,
+    /// Local variables cannot be exported, so this `Res` doesn't need the ID parameter.
+    pub res: Res<!>,
     /// The span of the target.
     pub span: Span,
     /// The visibility of the export.
     /// We include non-`pub` exports for hygienic macros that get used from extern crates.
     pub vis: ty::Visibility,
 }
-
-impl<Id> Export<Id> {
-    pub fn map_id<R>(self, map: impl FnMut(Id) -> R) -> Export<R> {
-        Export { ident: self.ident, res: self.res.map_id(map), span: self.span, vis: self.vis }
-    }
-}
diff --git a/compiler/rustc_middle/src/query/mod.rs b/compiler/rustc_middle/src/query/mod.rs
index c93996162e3..3b07be460db 100644
--- a/compiler/rustc_middle/src/query/mod.rs
+++ b/compiler/rustc_middle/src/query/mod.rs
@@ -1181,7 +1181,7 @@ rustc_queries! {
         desc { "traits in scope at a block" }
     }
 
-    query module_exports(def_id: LocalDefId) -> Option<&'tcx [Export<LocalDefId>]> {
+    query module_exports(def_id: LocalDefId) -> Option<&'tcx [Export]> {
         desc { |tcx| "looking up items exported by `{}`", tcx.def_path_str(def_id.to_def_id()) }
     }
 
@@ -1393,7 +1393,7 @@ rustc_queries! {
         eval_always
         desc { "fetching what a crate is named" }
     }
-    query item_children(def_id: DefId) -> &'tcx [Export<hir::HirId>] {
+    query item_children(def_id: DefId) -> &'tcx [Export] {
         desc { |tcx| "collecting child items of `{}`", tcx.def_path_str(def_id) }
     }
     query extern_mod_stmt_cnum(def_id: LocalDefId) -> Option<CrateNum> {
diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index fddfd6e435c..cd1e38445ae 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -127,7 +127,7 @@ pub struct ResolverOutputs {
     pub extern_crate_map: FxHashMap<LocalDefId, CrateNum>,
     pub maybe_unused_trait_imports: FxHashSet<LocalDefId>,
     pub maybe_unused_extern_crates: Vec<(LocalDefId, Span)>,
-    pub export_map: ExportMap<LocalDefId>,
+    pub export_map: ExportMap,
     pub glob_map: FxHashMap<LocalDefId, FxHashSet<Symbol>>,
     /// Extern prelude entries. The value is `true` if the entry was introduced
     /// via `extern crate` item and not `--extern` option or compiler built-in.
diff --git a/compiler/rustc_resolve/src/build_reduced_graph.rs b/compiler/rustc_resolve/src/build_reduced_graph.rs
index 2ee483d850e..55f2b04c4f1 100644
--- a/compiler/rustc_resolve/src/build_reduced_graph.rs
+++ b/compiler/rustc_resolve/src/build_reduced_graph.rs
@@ -228,7 +228,6 @@ impl<'a> Resolver<'a> {
     crate fn build_reduced_graph_external(&mut self, module: Module<'a>) {
         let def_id = module.def_id().expect("unpopulated module without a def-id");
         for child in self.cstore().item_children_untracked(def_id, self.session) {
-            let child = child.map_id(|_| panic!("unexpected id"));
             let parent_scope = ParentScope::module(module, self);
             BuildReducedGraphVisitor { r: self, parent_scope }
                 .build_reduced_graph_for_external_crate_res(child);
@@ -946,9 +945,10 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
     }
 
     /// Builds the reduced graph for a single item in an external crate.
-    fn build_reduced_graph_for_external_crate_res(&mut self, child: Export<NodeId>) {
+    fn build_reduced_graph_for_external_crate_res(&mut self, child: Export) {
         let parent = self.parent_scope.module;
         let Export { ident, res, vis, span } = child;
+        let res = res.expect_non_local();
         let expansion = self.parent_scope.expansion;
         // Record primary definitions.
         match res {
diff --git a/compiler/rustc_resolve/src/imports.rs b/compiler/rustc_resolve/src/imports.rs
index dfb6d89a0d1..d4782edbc13 100644
--- a/compiler/rustc_resolve/src/imports.rs
+++ b/compiler/rustc_resolve/src/imports.rs
@@ -11,7 +11,6 @@ use crate::{NameBinding, NameBindingKind, PathResult, PrivacyError, ToNameBindin
 
 use rustc_ast::unwrap_or;
 use rustc_ast::NodeId;
-use rustc_ast_lowering::ResolverAstLowering;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_data_structures::ptr_key::PtrKey;
 use rustc_errors::{pluralize, struct_span_err, Applicability};
@@ -1387,13 +1386,13 @@ impl<'a, 'b> ImportResolver<'a, 'b> {
 
         let mut reexports = Vec::new();
 
-        module.for_each_child(self.r, |this, ident, _, binding| {
+        module.for_each_child(self.r, |_, ident, _, binding| {
             // Filter away ambiguous imports and anything that has def-site hygiene.
             // FIXME: Implement actual cross-crate hygiene.
             let is_good_import =
                 binding.is_import() && !binding.is_ambiguity() && !ident.span.from_expansion();
             if is_good_import || binding.is_macro_def() {
-                let res = binding.res().map_id(|id| this.local_def_id(id));
+                let res = binding.res().expect_non_local();
                 if res != def::Res::Err {
                     reexports.push(Export { ident, res, span: binding.span, vis: binding.vis });
                 }
diff --git a/compiler/rustc_resolve/src/lib.rs b/compiler/rustc_resolve/src/lib.rs
index 6d2961db9e3..912f0bf13fe 100644
--- a/compiler/rustc_resolve/src/lib.rs
+++ b/compiler/rustc_resolve/src/lib.rs
@@ -14,6 +14,7 @@
 #![feature(crate_visibility_modifier)]
 #![feature(format_args_capture)]
 #![feature(iter_zip)]
+#![feature(never_type)]
 #![feature(nll)]
 #![recursion_limit = "256"]
 #![allow(rustdoc::private_intra_doc_links)]
@@ -911,7 +912,7 @@ pub struct Resolver<'a> {
 
     /// `CrateNum` resolutions of `extern crate` items.
     extern_crate_map: FxHashMap<LocalDefId, CrateNum>,
-    export_map: ExportMap<LocalDefId>,
+    export_map: ExportMap,
     trait_map: Option<NodeMap<Vec<TraitCandidate>>>,
 
     /// A map from nodes to anonymous modules.
diff --git a/compiler/rustc_serialize/src/serialize.rs b/compiler/rustc_serialize/src/serialize.rs
index ecc8dae0480..e32e4493726 100644
--- a/compiler/rustc_serialize/src/serialize.rs
+++ b/compiler/rustc_serialize/src/serialize.rs
@@ -366,6 +366,18 @@ direct_serialize_impls! {
     char emit_char read_char
 }
 
+impl<S: Encoder> Encodable<S> for ! {
+    fn encode(&self, _s: &mut S) -> Result<(), S::Error> {
+        unreachable!()
+    }
+}
+
+impl<D: Decoder> Decodable<D> for ! {
+    fn decode(_d: &mut D) -> Result<!, D::Error> {
+        unreachable!()
+    }
+}
+
 impl<S: Encoder> Encodable<S> for ::std::num::NonZeroU32 {
     fn encode(&self, s: &mut S) -> Result<(), S::Error> {
         s.emit_u32(self.get())
diff --git a/compiler/rustc_typeck/src/check/method/suggest.rs b/compiler/rustc_typeck/src/check/method/suggest.rs
index a746ad7ad4b..9744f4f6483 100644
--- a/compiler/rustc_typeck/src/check/method/suggest.rs
+++ b/compiler/rustc_typeck/src/check/method/suggest.rs
@@ -1655,7 +1655,7 @@ fn compute_all_traits(tcx: TyCtxt<'_>, (): ()) -> &[DefId] {
         tcx: TyCtxt<'_>,
         traits: &mut Vec<DefId>,
         external_mods: &mut FxHashSet<DefId>,
-        res: Res,
+        res: Res<!>,
     ) {
         match res {
             Res::Def(DefKind::Trait | DefKind::TraitAlias, def_id) => {
diff --git a/src/librustdoc/clean/inline.rs b/src/librustdoc/clean/inline.rs
index 0c81a558430..b8633f0dcfd 100644
--- a/src/librustdoc/clean/inline.rs
+++ b/src/librustdoc/clean/inline.rs
@@ -482,12 +482,13 @@ fn build_module(
     // visit each node at most once.
     for &item in cx.tcx.item_children(did).iter() {
         if item.vis == ty::Visibility::Public {
-            if let Some(def_id) = item.res.mod_def_id() {
+            let res = item.res.expect_non_local();
+            if let Some(def_id) = res.mod_def_id() {
                 if did == def_id || !visited.insert(def_id) {
                     continue;
                 }
             }
-            if let Res::PrimTy(p) = item.res {
+            if let Res::PrimTy(p) = res {
                 // Primitive types can't be inlined so generate an import instead.
                 let prim_ty = clean::PrimitiveType::from(p);
                 items.push(clean::Item {
@@ -500,7 +501,7 @@ fn build_module(
                         clean::ImportSource {
                             path: clean::Path {
                                 global: false,
-                                res: item.res,
+                                res,
                                 segments: vec![clean::PathSegment {
                                     name: prim_ty.as_sym(),
                                     args: clean::GenericArgs::AngleBracketed {
@@ -515,9 +516,7 @@ fn build_module(
                     ))),
                     cfg: None,
                 });
-            } else if let Some(i) =
-                try_inline(cx, did, None, item.res, item.ident.name, None, visited)
-            {
+            } else if let Some(i) = try_inline(cx, did, None, res, item.ident.name, None, visited) {
                 items.extend(i)
             }
         }
diff --git a/src/librustdoc/clean/types.rs b/src/librustdoc/clean/types.rs
index 5eff56a2200..8f31a42e1a2 100644
--- a/src/librustdoc/clean/types.rs
+++ b/src/librustdoc/clean/types.rs
@@ -212,7 +212,7 @@ impl ExternalCrate {
     crate fn keywords(&self, tcx: TyCtxt<'_>) -> ThinVec<(DefId, Symbol)> {
         let root = self.def_id();
 
-        let as_keyword = |res: Res| {
+        let as_keyword = |res: Res<!>| {
             if let Res::Def(DefKind::Mod, def_id) = res {
                 let attrs = tcx.get_attrs(def_id);
                 let mut keyword = None;
@@ -243,7 +243,8 @@ impl ExternalCrate {
                         hir::ItemKind::Use(ref path, hir::UseKind::Single)
                             if item.vis.node.is_pub() =>
                         {
-                            as_keyword(path.res).map(|(_, prim)| (id.def_id.to_def_id(), prim))
+                            as_keyword(path.res.expect_non_local())
+                                .map(|(_, prim)| (id.def_id.to_def_id(), prim))
                         }
                         _ => None,
                     }
@@ -274,7 +275,7 @@ impl ExternalCrate {
         // Also note that this does not attempt to deal with modules tagged
         // duplicately for the same primitive. This is handled later on when
         // rendering by delegating everything to a hash map.
-        let as_primitive = |res: Res| {
+        let as_primitive = |res: Res<!>| {
             if let Res::Def(DefKind::Mod, def_id) = res {
                 let attrs = tcx.get_attrs(def_id);
                 let mut prim = None;
@@ -309,7 +310,7 @@ impl ExternalCrate {
                         hir::ItemKind::Use(ref path, hir::UseKind::Single)
                             if item.vis.node.is_pub() =>
                         {
-                            as_primitive(path.res).map(|(_, prim)| {
+                            as_primitive(path.res.expect_non_local()).map(|(_, prim)| {
                                 // Pretend the primitive is local.
                                 (id.def_id.to_def_id(), prim)
                             })
diff --git a/src/librustdoc/visit_lib.rs b/src/librustdoc/visit_lib.rs
index 3e06b417314..3e98ba08fb9 100644
--- a/src/librustdoc/visit_lib.rs
+++ b/src/librustdoc/visit_lib.rs
@@ -67,7 +67,7 @@ impl<'a, 'tcx> LibEmbargoVisitor<'a, 'tcx> {
         }
     }
 
-    fn visit_item(&mut self, res: Res) {
+    fn visit_item(&mut self, res: Res<!>) {
         let def_id = res.def_id();
         let vis = self.tcx.visibility(def_id);
         let inherited_item_level = if vis == Visibility::Public { self.prev_level } else { None };
diff --git a/src/tools/clippy/clippy_utils/src/lib.rs b/src/tools/clippy/clippy_utils/src/lib.rs
index da259511fe0..3a94f472983 100644
--- a/src/tools/clippy/clippy_utils/src/lib.rs
+++ b/src/tools/clippy/clippy_utils/src/lib.rs
@@ -520,7 +520,7 @@ pub fn path_to_res(cx: &LateContext<'_>, path: &[&str]) -> Res {
             }
         };
     }
-    fn item_child_by_name<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId, name: &str) -> Option<&'tcx Export<HirId>> {
+    fn item_child_by_name<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId, name: &str) -> Option<&'tcx Export> {
         tcx.item_children(def_id)
             .iter()
             .find(|item| item.ident.name.as_str() == name)
@@ -557,7 +557,7 @@ pub fn path_to_res(cx: &LateContext<'_>, path: &[&str]) -> Res {
                 None
             }
         });
-    try_res!(last).res
+    try_res!(last).res.expect_non_local()
 }
 
 /// Convenience function to get the `DefId` of a trait by path.