rustdoc: Unify external_paths and paths cache map

The `formats::cache::Cache` fields `paths` and `external_paths` are now
unified to a single `paths` map, which makes it easier to manage the
paths and avoids using local paths as extern and vice versa.

The `paths` map maps a `DefId` to an enum which can be either `Local` or
`Extern` so there can't be any misusing.

Author: Stupremee

Diff for: src/librustdoc/clean/inline.rs

@@ -18,7 +18,7 @@ use crate::clean::{
     self, utils, Attributes, AttributesExt, GetDefId, ItemId, NestedAttributesExt, Type,
 };
 use crate::core::DocContext;
-use crate::formats::item_type::ItemType;
+use crate::formats::{cache::CachedPath, item_type::ItemType};
 
 use super::{Clean, Visibility};
 
@@ -189,7 +189,7 @@ crate fn record_extern_fqn(cx: &mut DocContext<'_>, did: DefId, kind: ItemType)
     if did.is_local() {
         cx.cache.exact_paths.insert(did, fqn);
     } else {
-        cx.cache.external_paths.insert(did, (fqn, kind));
+        cx.cache.paths.insert(did, CachedPath::Extern(fqn, kind));
     }
 }
 

Diff for: src/librustdoc/formats/cache.rs

@@ -16,6 +16,24 @@ use crate::html::markdown::short_markdown_summary;
 use crate::html::render::cache::{get_index_search_type, ExternalLocation};
 use crate::html::render::IndexItem;
 
+/// A path that is either local, or external. It consists of a fully qualified name,
+/// and a type description.
+#[derive(Debug, Clone)]
+crate enum CachedPath {
+    Local(Vec<String>, ItemType),
+    Extern(Vec<String>, ItemType),
+}
+
+impl CachedPath {
+    crate fn is_local(&self) -> bool {
+        matches!(self, CachedPath::Local(..))
+    }
+
+    crate fn is_extern(&self) -> bool {
+        matches!(self, CachedPath::Extern(..))
+    }
+}
+
 /// This cache is used to store information about the [`clean::Crate`] being
 /// rendered in order to provide more useful documentation. This contains
 /// information like all implementors of a trait, all traits a type implements,
@@ -35,16 +53,12 @@ crate struct Cache {
     /// found on that implementation.
     crate impls: FxHashMap<DefId, Vec<Impl>>,
 
-    /// Maintains a mapping of local crate `DefId`s to the fully qualified name
-    /// and "short type description" of that node. This is used when generating
-    /// URLs when a type is being linked to. External paths are not located in
-    /// this map because the `External` type itself has all the information
-    /// necessary.
-    crate paths: FxHashMap<DefId, (Vec<String>, ItemType)>,
-
-    /// Similar to `paths`, but only holds external paths. This is only used for
-    /// generating explicit hyperlinks to other crates.
-    crate external_paths: FxHashMap<DefId, (Vec<String>, ItemType)>,
+    /// Maintain a mapping of `DefId`s to the fully qualified name and "shorty type description" of
+    /// that node. This map contains local and external cached paths that are differentiated using
+    /// the [`CachedPath`] enum.
+    ///
+    /// This was previously known as `extern_paths` and `paths`.
+    crate paths: FxHashMap<DefId, CachedPath>,
 
     /// Maps local `DefId`s of exported types to fully qualified paths.
     /// Unlike 'paths', this mapping ignores any renames that occur
@@ -156,7 +170,7 @@ impl Cache {
             let extern_url = extern_html_root_urls.get(&*name.as_str()).map(|u| &**u);
             let did = DefId { krate: n, index: CRATE_DEF_INDEX };
             self.extern_locations.insert(n, e.location(extern_url, &dst, tcx));
-            self.external_paths.insert(did, (vec![name.to_string()], ItemType::Module));
+            self.paths.insert(did, CachedPath::Extern(vec![name.to_string()], ItemType::Module));
         }
 
         // Cache where all known primitives have their documentation located.
@@ -267,15 +281,15 @@ impl<'a, 'tcx> DocFolder for CacheBuilder<'a, 'tcx> {
                             // for where the type was defined. On the other
                             // hand, `paths` always has the right
                             // information if present.
-                            Some(&(
+                            Some(CachedPath::Local(
                                 ref fqp,
                                 ItemType::Trait
                                 | ItemType::Struct
                                 | ItemType::Union
                                 | ItemType::Enum,
                             )) => Some(&fqp[..fqp.len() - 1]),
-                            Some(..) => Some(&*self.cache.stack),
-                            None => None,
+                            Some(CachedPath::Local(..)) => Some(&*self.cache.stack),
+                            _ => None,
                         };
                         ((Some(*last), path), true)
                     }
@@ -353,15 +367,16 @@ impl<'a, 'tcx> DocFolder for CacheBuilder<'a, 'tcx> {
                     {
                         self.cache.paths.insert(
                             item.def_id.expect_def_id(),
-                            (self.cache.stack.clone(), item.type_()),
+                            CachedPath::Local(self.cache.stack.clone(), item.type_()),
                         );
                     }
                 }
             }
             clean::PrimitiveItem(..) => {
-                self.cache
-                    .paths
-                    .insert(item.def_id.expect_def_id(), (self.cache.stack.clone(), item.type_()));
+                self.cache.paths.insert(
+                    item.def_id.expect_def_id(),
+                    CachedPath::Local(self.cache.stack.clone(), item.type_()),
+                );
             }
 
             clean::ExternCrateItem { .. }

Diff for: src/librustdoc/html/format.rs

@@ -21,7 +21,7 @@ use rustc_target::spec::abi::Abi;
 use crate::clean::{
     self, utils::find_nearest_parent_module, ExternalCrate, GetDefId, ItemId, PrimitiveType,
 };
-use crate::formats::item_type::ItemType;
+use crate::formats::{cache::CachedPath, item_type::ItemType};
 use crate::html::escape::Escape;
 use crate::html::render::cache::ExternalLocation;
 use crate::html::render::Context;
@@ -483,13 +483,12 @@ crate fn href(did: DefId, cx: &Context<'_>) -> Option<(String, ItemType, Vec<Str
         return None;
     }
 
-    let (fqp, shortty, mut url_parts) = match cache.paths.get(&did) {
-        Some(&(ref fqp, shortty)) => (fqp, shortty, {
+    let (fqp, shortty, mut url_parts) = match *cache.paths.get(&did)? {
+        CachedPath::Local(ref fqp, shortty) => (fqp, shortty, {
             let module_fqp = to_module_fqp(shortty, fqp);
             href_relative_parts(module_fqp, relative_to)
         }),
-        None => {
-            let &(ref fqp, shortty) = cache.external_paths.get(&did)?;
+        CachedPath::Extern(ref fqp, shortty) => {
             let module_fqp = to_module_fqp(shortty, fqp);
             (
                 fqp,

Diff for: src/librustdoc/html/render/cache.rs

@@ -9,7 +9,7 @@ use crate::clean;
 use crate::clean::types::{
     FnDecl, FnRetTy, GenericBound, Generics, GetDefId, Type, WherePredicate,
 };
-use crate::formats::cache::Cache;
+use crate::formats::cache::{Cache, CachedPath};
 use crate::formats::item_type::ItemType;
 use crate::html::markdown::short_markdown_summary;
 use crate::html::render::{IndexItem, IndexItemFunctionType, RenderType, TypeWithKind};
@@ -33,7 +33,7 @@ crate fn build_index<'tcx>(krate: &clean::Crate, cache: &mut Cache, tcx: TyCtxt<
     // Attach all orphan items to the type's definition if the type
     // has since been learned.
     for &(did, ref item) in &cache.orphan_impl_items {
-        if let Some(&(ref fqp, _)) = cache.paths.get(&did) {
+        if let Some(CachedPath::Local(fqp, _)) = cache.paths.get(&did) {
             let desc = item
                 .doc_value()
                 .map_or_else(String::new, |s| short_markdown_summary(&s, &item.link_names(&cache)));
@@ -90,7 +90,7 @@ crate fn build_index<'tcx>(krate: &clean::Crate, cache: &mut Cache, tcx: TyCtxt<
                 defid_to_pathid.insert(defid, pathid);
                 lastpathid += 1;
 
-                if let Some(&(ref fqp, short)) = paths.get(&defid) {
+                if let Some(&CachedPath::Local(ref fqp, short)) = paths.get(&defid) {
                     crate_paths.push((short, fqp.last().unwrap().clone()));
                     Some(pathid)
                 } else {

Diff for: src/librustdoc/html/render/context.rs

@@ -24,7 +24,7 @@ use crate::clean::ExternalCrate;
 use crate::config::RenderOptions;
 use crate::docfs::{DocFS, PathError};
 use crate::error::Error;
-use crate::formats::cache::Cache;
+use crate::formats::cache::{Cache, CachedPath};
 use crate::formats::item_type::ItemType;
 use crate::formats::FormatRenderer;
 use crate::html::escape::Escape;
@@ -230,7 +230,9 @@ impl<'tcx> Context<'tcx> {
                 &self.shared.style_files,
             )
         } else {
-            if let Some(&(ref names, ty)) = self.cache.paths.get(&it.def_id.expect_def_id()) {
+            if let Some(&CachedPath::Local(ref names, ty)) =
+                self.cache.paths.get(&it.def_id.expect_def_id())
+            {
                 let mut path = String::new();
                 for name in &names[..names.len() - 1] {
                     path.push_str(name);

Diff for: src/librustdoc/html/render/mod.rs

@@ -56,7 +56,7 @@ use serde::{Serialize, Serializer};
 use crate::clean::{self, GetDefId, ItemId, RenderedLink, SelfTy};
 use crate::docfs::PathError;
 use crate::error::Error;
-use crate::formats::cache::Cache;
+use crate::formats::cache::{Cache, CachedPath};
 use crate::formats::item_type::ItemType;
 use crate::formats::{AssocItemRender, Impl, RenderMode};
 use crate::html::escape::Escape;
@@ -2339,7 +2339,12 @@ fn collect_paths_for_type(first_ty: clean::Type, cache: &Cache) -> Vec<String> {
 
         match ty {
             clean::Type::ResolvedPath { did, .. } => {
-                let get_extern = || cache.external_paths.get(&did).map(|s| s.0.clone());
+                let get_extern = || {
+                    cache.paths.get(&did).and_then(|p| match p {
+                        CachedPath::Extern(a, _) => Some(a.clone()),
+                        CachedPath::Local(..) => None,
+                    })
+                };
                 let fqp = cache.exact_paths.get(&did).cloned().or_else(get_extern);
 
                 if let Some(path) = fqp {

Diff for: src/librustdoc/html/render/print_item.rs

@@ -19,7 +19,7 @@ use super::{
     Context,
 };
 use crate::clean::{self, GetDefId};
-use crate::formats::item_type::ItemType;
+use crate::formats::{cache::CachedPath, item_type::ItemType};
 use crate::formats::{AssocItemRender, Impl, RenderMode};
 use crate::html::escape::Escape;
 use crate::html::format::{
@@ -696,7 +696,7 @@ fn item_trait(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, t: &clean::Tra
             i.inner_impl()
                 .for_
                 .def_id_full(cx.cache())
-                .map_or(true, |d| cx.cache.paths.contains_key(&d))
+                .map_or(true, |d| cx.cache.paths.get(&d).map_or(false, CachedPath::is_local))
         });
 
         let (mut synthetic, mut concrete): (Vec<&&Impl>, Vec<&&Impl>) =
@@ -784,11 +784,9 @@ fn item_trait(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, t: &clean::Tra
                  src=\"{root_path}/implementors/{path}/{ty}.{name}.js\" async>\
          </script>",
         root_path = vec![".."; cx.current.len()].join("/"),
-        path = if it.def_id.is_local() {
-            cx.current.join("/")
-        } else {
-            let (ref path, _) = cx.cache.external_paths[&it.def_id.expect_def_id()];
-            path[..path.len() - 1].join("/")
+        path = match cx.cache.paths[&it.def_id.expect_def_id()] {
+            CachedPath::Extern(_, _) => cx.current.join("/"),
+            CachedPath::Local(ref path, _) => path[..path.len() - 1].join("/"),
         },
         ty = it.type_(),
         name = *it.name.as_ref().unwrap()

Diff for: src/librustdoc/html/render/write_shared.rs

@@ -16,6 +16,7 @@ use crate::clean::Crate;
 use crate::config::{EmitType, RenderOptions};
 use crate::docfs::PathError;
 use crate::error::Error;
+use crate::formats::cache::CachedPath;
 use crate::html::{layout, static_files};
 
 static FILES_UNVERSIONED: Lazy<FxHashMap<&str, &[u8]>> = Lazy::new(|| {
@@ -488,12 +489,9 @@ pub(super) fn write_shared(
         //
         // FIXME: this is a vague explanation for why this can't be a `get`, in
         //        theory it should be...
-        let &(ref remote_path, remote_item_type) = match cx.cache.paths.get(&did) {
-            Some(p) => p,
-            None => match cx.cache.external_paths.get(&did) {
-                Some(p) => p,
-                None => continue,
-            },
+        let (remote_path, remote_item_type) = match cx.cache.paths.get(&did) {
+            Some(&CachedPath::Local(ref a, b) | &CachedPath::Extern(ref a, b)) => (a, b),
+            None => continue,
         };
 
         #[derive(Serialize)]
@@ -528,7 +526,8 @@ pub(super) fn write_shared(
         // Only create a js file if we have impls to add to it. If the trait is
         // documented locally though we always create the file to avoid dead
         // links.
-        if implementors.is_empty() && !cx.cache.paths.contains_key(&did) {
+        if implementors.is_empty() && cx.cache.paths.get(&did).map_or(false, CachedPath::is_extern)
+        {
             continue;
         }
 

Diff for: src/librustdoc/json/mod.rs

@@ -22,7 +22,7 @@ use crate::clean;
 use crate::clean::ExternalCrate;
 use crate::config::RenderOptions;
 use crate::error::Error;
-use crate::formats::cache::Cache;
+use crate::formats::cache::{Cache, CachedPath};
 use crate::formats::FormatRenderer;
 use crate::html::render::cache::ExternalLocation;
 use crate::json::conversions::{from_item_id, IntoWithTcx};
@@ -99,13 +99,10 @@ impl JsonRenderer<'tcx> {
                                 .cache
                                 .paths
                                 .get(&id)
-                                .unwrap_or_else(|| {
-                                    self.cache
-                                        .external_paths
-                                        .get(&id)
-                                        .expect("Trait should either be in local or external paths")
+                                .map(|p| match p {
+                                    CachedPath::Local(a, _) | CachedPath::Extern(a, _) => a,
                                 })
-                                .0
+                                .unwrap()
                                 .last()
                                 .map(Clone::clone),
                             visibility: types::Visibility::Public,
@@ -204,8 +201,7 @@ impl<'tcx> FormatRenderer<'tcx> for JsonRenderer<'tcx> {
                 .paths
                 .clone()
                 .into_iter()
-                .chain(self.cache.external_paths.clone().into_iter())
-                .map(|(k, (path, kind))| {
+                .map(|(k, CachedPath::Local(path, kind) | CachedPath::Extern(path, kind))| {
                     (
                         from_item_id(k.into()),
                         types::ItemSummary {