Extract `Cache` and other types from `html` module

12 files changed, 808 insertions, 752 deletions

diff --git a/src/librustdoc/clean/types.rs b/src/librustdoc/clean/types.rs
index 071834c59d6..89549eae2cb 100644
--- a/src/librustdoc/clean/types.rs
+++ b/src/librustdoc/clean/types.rs
@@ -32,8 +32,9 @@ use crate::clean::inline;
 use crate::clean::types::Type::{QPath, ResolvedPath};
 use crate::core::DocContext;
 use crate::doctree;
-use crate::html::item_type::ItemType;
-use crate::html::render::{cache, ExternalLocation};
+use crate::formats::cache::cache;
+use crate::formats::item_type::ItemType;
+use crate::html::render::cache::ExternalLocation;
 
 use self::FnRetTy::*;
 use self::ItemEnum::*;
@@ -1172,7 +1173,7 @@ impl GetDefId for Type {
     fn def_id(&self) -> Option<DefId> {
         match *self {
             ResolvedPath { did, .. } => Some(did),
-            Primitive(p) => crate::html::render::cache().primitive_locations.get(&p).cloned(),
+            Primitive(p) => cache().primitive_locations.get(&p).cloned(),
             BorrowedRef { type_: box Generic(..), .. } => {
                 Primitive(PrimitiveType::Reference).def_id()
             }
diff --git a/src/librustdoc/config.rs b/src/librustdoc/config.rs
index 1ea9e28ae42..3547b45dfa7 100644
--- a/src/librustdoc/config.rs
+++ b/src/librustdoc/config.rs
@@ -254,7 +254,7 @@ pub struct RenderOptions {
 
 /// Temporary storage for data obtained during `RustdocVisitor::clean()`.
 /// Later on moved into `CACHE_KEY`.
-#[derive(Default)]
+#[derive(Default, Clone)]
 pub struct RenderInfo {
     pub inlined: FxHashSet<DefId>,
     pub external_paths: crate::core::ExternalPaths,
diff --git a/src/librustdoc/core.rs b/src/librustdoc/core.rs
index 85bb7ca4cd6..7635453d56f 100644
--- a/src/librustdoc/core.rs
+++ b/src/librustdoc/core.rs
@@ -44,9 +44,9 @@ pub type ExternalPaths = FxHashMap<DefId, (Vec<String>, clean::TypeKind)>;
 pub struct DocContext<'tcx> {
     pub tcx: TyCtxt<'tcx>,
     pub resolver: Rc<RefCell<interface::BoxedResolver>>,
-    /// Later on moved into `html::render::CACHE_KEY`
+    /// Later on moved into `formats::cache::CACHE_KEY`
     pub renderinfo: RefCell<RenderInfo>,
-    /// Later on moved through `clean::Crate` into `html::render::CACHE_KEY`
+    /// Later on moved through `clean::Crate` into `formats::cache::CACHE_KEY`
     pub external_traits: Rc<RefCell<FxHashMap<DefId, clean::Trait>>>,
     /// Used while populating `external_traits` to ensure we don't process the same trait twice at
     /// the same time.
diff --git a/src/librustdoc/formats/cache.rs b/src/librustdoc/formats/cache.rs
new file mode 100644
index 00000000000..4bdeafa1ec7
--- /dev/null
+++ b/src/librustdoc/formats/cache.rs
@@ -0,0 +1,498 @@
+use std::cell::RefCell;
+use std::collections::BTreeMap;
+use std::mem;
+use std::path::{Path, PathBuf};
+use std::sync::Arc;
+
+use rustc_data_structures::fx::{FxHashMap, FxHashSet};
+use rustc_hir::def_id::{CrateNum, DefId, CRATE_DEF_INDEX};
+use rustc_middle::middle::privacy::AccessLevels;
+use rustc_span::source_map::FileName;
+
+use crate::clean::{self, GetDefId};
+use crate::config::RenderInfo;
+use crate::fold::DocFolder;
+use crate::formats::item_type::ItemType;
+use crate::formats::Impl;
+use crate::html::render::cache::{extern_location, get_index_search_type, ExternalLocation};
+use crate::html::render::IndexItem;
+use crate::html::render::{plain_summary_line, shorten};
+
+thread_local!(crate static CACHE_KEY: RefCell<Arc<Cache>> = Default::default());
+
+/// 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,
+/// documentation for all known traits, etc.
+///
+/// This structure purposefully does not implement `Clone` because it's intended
+/// to be a fairly large and expensive structure to clone. Instead this adheres
+/// to `Send` so it may be stored in a `Arc` instance and shared among the various
+/// rendering threads.
+#[derive(Default)]
+pub struct Cache {
+    /// Maps a type ID to all known implementations for that type. This is only
+    /// recognized for intra-crate `ResolvedPath` types, and is used to print
+    /// out extra documentation on the page of an enum/struct.
+    ///
+    /// The values of the map are a list of implementations and documentation
+    /// found on that implementation.
+    pub 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.
+    pub 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.
+    pub external_paths: FxHashMap<DefId, (Vec<String>, ItemType)>,
+
+    /// Maps local `DefId`s of exported types to fully qualified paths.
+    /// Unlike 'paths', this mapping ignores any renames that occur
+    /// due to 'use' statements.
+    ///
+    /// This map is used when writing out the special 'implementors'
+    /// javascript file. By using the exact path that the type
+    /// is declared with, we ensure that each path will be identical
+    /// to the path used if the corresponding type is inlined. By
+    /// doing this, we can detect duplicate impls on a trait page, and only display
+    /// the impl for the inlined type.
+    pub exact_paths: FxHashMap<DefId, Vec<String>>,
+
+    /// This map contains information about all known traits of this crate.
+    /// Implementations of a crate should inherit the documentation of the
+    /// parent trait if no extra documentation is specified, and default methods
+    /// should show up in documentation about trait implementations.
+    pub traits: FxHashMap<DefId, clean::Trait>,
+
+    /// When rendering traits, it's often useful to be able to list all
+    /// implementors of the trait, and this mapping is exactly, that: a mapping
+    /// of trait ids to the list of known implementors of the trait
+    pub implementors: FxHashMap<DefId, Vec<Impl>>,
+
+    /// Cache of where external crate documentation can be found.
+    pub extern_locations: FxHashMap<CrateNum, (String, PathBuf, ExternalLocation)>,
+
+    /// Cache of where documentation for primitives can be found.
+    pub primitive_locations: FxHashMap<clean::PrimitiveType, DefId>,
+
+    // Note that external items for which `doc(hidden)` applies to are shown as
+    // non-reachable while local items aren't. This is because we're reusing
+    // the access levels from the privacy check pass.
+    pub access_levels: AccessLevels<DefId>,
+
+    /// The version of the crate being documented, if given from the `--crate-version` flag.
+    pub crate_version: Option<String>,
+
+    /// Whether to document private items.
+    /// This is stored in `Cache` so it doesn't need to be passed through all rustdoc functions.
+    pub document_private: bool,
+
+    // Private fields only used when initially crawling a crate to build a cache
+    stack: Vec<String>,
+    parent_stack: Vec<DefId>,
+    parent_is_trait_impl: bool,
+    stripped_mod: bool,
+    masked_crates: FxHashSet<CrateNum>,
+
+    pub search_index: Vec<IndexItem>,
+    pub deref_trait_did: Option<DefId>,
+    pub deref_mut_trait_did: Option<DefId>,
+    pub owned_box_did: Option<DefId>,
+
+    // In rare case where a structure is defined in one module but implemented
+    // in another, if the implementing module is parsed before defining module,
+    // then the fully qualified name of the structure isn't presented in `paths`
+    // yet when its implementation methods are being indexed. Caches such methods
+    // and their parent id here and indexes them at the end of crate parsing.
+    pub orphan_impl_items: Vec<(DefId, clean::Item)>,
+
+    // Similarly to `orphan_impl_items`, sometimes trait impls are picked up
+    // even though the trait itself is not exported. This can happen if a trait
+    // was defined in function/expression scope, since the impl will be picked
+    // up by `collect-trait-impls` but the trait won't be scraped out in the HIR
+    // crawl. In order to prevent crashes when looking for spotlight traits or
+    // when gathering trait documentation on a type, hold impls here while
+    // folding and add them to the cache later on if we find the trait.
+    orphan_trait_impls: Vec<(DefId, FxHashSet<DefId>, Impl)>,
+
+    /// Aliases added through `#[doc(alias = "...")]`. Since a few items can have the same alias,
+    /// we need the alias element to have an array of items.
+    pub aliases: BTreeMap<String, Vec<usize>>,
+}
+
+impl Cache {
+    pub fn from_krate(
+        renderinfo: RenderInfo,
+        document_private: bool,
+        extern_html_root_urls: &BTreeMap<String, String>,
+        dst: &Path,
+        mut krate: clean::Crate,
+    ) -> (clean::Crate, Cache) {
+        // Crawl the crate to build various caches used for the output
+        let RenderInfo {
+            inlined: _,
+            external_paths,
+            exact_paths,
+            access_levels,
+            deref_trait_did,
+            deref_mut_trait_did,
+            owned_box_did,
+            ..
+        } = renderinfo;
+
+        let external_paths =
+            external_paths.into_iter().map(|(k, (v, t))| (k, (v, ItemType::from(t)))).collect();
+
+        let mut cache = Cache {
+            impls: Default::default(),
+            external_paths,
+            exact_paths,
+            paths: Default::default(),
+            implementors: Default::default(),
+            stack: Vec::new(),
+            parent_stack: Vec::new(),
+            search_index: Vec::new(),
+            parent_is_trait_impl: false,
+            extern_locations: Default::default(),
+            primitive_locations: Default::default(),
+            stripped_mod: false,
+            access_levels,
+            crate_version: krate.version.take(),
+            document_private,
+            orphan_impl_items: Vec::new(),
+            orphan_trait_impls: Vec::new(),
+            traits: krate.external_traits.replace(Default::default()),
+            deref_trait_did,
+            deref_mut_trait_did,
+            owned_box_did,
+            masked_crates: mem::take(&mut krate.masked_crates),
+            aliases: Default::default(),
+        };
+
+        // Cache where all our extern crates are located
+        // TODO: this part is specific to HTML so it'd be nice to remove it from the common code
+        for &(n, ref e) in &krate.externs {
+            let src_root = match e.src {
+                FileName::Real(ref p) => match p.local_path().parent() {
+                    Some(p) => p.to_path_buf(),
+                    None => PathBuf::new(),
+                },
+                _ => PathBuf::new(),
+            };
+            let extern_url = extern_html_root_urls.get(&e.name).map(|u| &**u);
+            cache
+                .extern_locations
+                .insert(n, (e.name.clone(), src_root, extern_location(e, extern_url, &dst)));
+
+            let did = DefId { krate: n, index: CRATE_DEF_INDEX };
+            cache.external_paths.insert(did, (vec![e.name.to_string()], ItemType::Module));
+        }
+
+        // Cache where all known primitives have their documentation located.
+        //
+        // Favor linking to as local extern as possible, so iterate all crates in
+        // reverse topological order.
+        for &(_, ref e) in krate.externs.iter().rev() {
+            for &(def_id, prim, _) in &e.primitives {
+                cache.primitive_locations.insert(prim, def_id);
+            }
+        }
+        for &(def_id, prim, _) in &krate.primitives {
+            cache.primitive_locations.insert(prim, def_id);
+        }
+
+        cache.stack.push(krate.name.clone());
+        krate = cache.fold_crate(krate);
+
+        for (trait_did, dids, impl_) in cache.orphan_trait_impls.drain(..) {
+            if cache.traits.contains_key(&trait_did) {
+                for did in dids {
+                    cache.impls.entry(did).or_insert(vec![]).push(impl_.clone());
+                }
+            }
+        }
+
+        (krate, cache)
+    }
+}
+
+impl DocFolder for Cache {
+    fn fold_item(&mut self, item: clean::Item) -> Option<clean::Item> {
+        if item.def_id.is_local() {
+            debug!("folding {} \"{:?}\", id {:?}", item.type_(), item.name, item.def_id);
+        }
+
+        // If this is a stripped module,
+        // we don't want it or its children in the search index.
+        let orig_stripped_mod = match item.inner {
+            clean::StrippedItem(box clean::ModuleItem(..)) => {
+                mem::replace(&mut self.stripped_mod, true)
+            }
+            _ => self.stripped_mod,
+        };
+
+        // If the impl is from a masked crate or references something from a
+        // masked crate then remove it completely.
+        if let clean::ImplItem(ref i) = item.inner {
+            if self.masked_crates.contains(&item.def_id.krate)
+                || i.trait_.def_id().map_or(false, |d| self.masked_crates.contains(&d.krate))
+                || i.for_.def_id().map_or(false, |d| self.masked_crates.contains(&d.krate))
+            {
+                return None;
+            }
+        }
+
+        // Propagate a trait method's documentation to all implementors of the
+        // trait.
+        if let clean::TraitItem(ref t) = item.inner {
+            self.traits.entry(item.def_id).or_insert_with(|| t.clone());
+        }
+
+        // Collect all the implementors of traits.
+        if let clean::ImplItem(ref i) = item.inner {
+            if let Some(did) = i.trait_.def_id() {
+                if i.blanket_impl.is_none() {
+                    self.implementors
+                        .entry(did)
+                        .or_default()
+                        .push(Impl { impl_item: item.clone() });
+                }
+            }
+        }
+
+        // Index this method for searching later on.
+        if let Some(ref s) = item.name {
+            let (parent, is_inherent_impl_item) = match item.inner {
+                clean::StrippedItem(..) => ((None, None), false),
+                clean::AssocConstItem(..) | clean::TypedefItem(_, true)
+                    if self.parent_is_trait_impl =>
+                {
+                    // skip associated items in trait impls
+                    ((None, None), false)
+                }
+                clean::AssocTypeItem(..)
+                | clean::TyMethodItem(..)
+                | clean::StructFieldItem(..)
+                | clean::VariantItem(..) => (
+                    (
+                        Some(*self.parent_stack.last().expect("parent_stack is empty")),
+                        Some(&self.stack[..self.stack.len() - 1]),
+                    ),
+                    false,
+                ),
+                clean::MethodItem(..) | clean::AssocConstItem(..) => {
+                    if self.parent_stack.is_empty() {
+                        ((None, None), false)
+                    } else {
+                        let last = self.parent_stack.last().expect("parent_stack is empty 2");
+                        let did = *last;
+                        let path = match self.paths.get(&did) {
+                            // The current stack not necessarily has correlation
+                            // for where the type was defined. On the other
+                            // hand, `paths` always has the right
+                            // information if present.
+                            Some(&(
+                                ref fqp,
+                                ItemType::Trait
+                                | ItemType::Struct
+                                | ItemType::Union
+                                | ItemType::Enum,
+                            )) => Some(&fqp[..fqp.len() - 1]),
+                            Some(..) => Some(&*self.stack),
+                            None => None,
+                        };
+                        ((Some(*last), path), true)
+                    }
+                }
+                _ => ((None, Some(&*self.stack)), false),
+            };
+
+            match parent {
+                (parent, Some(path)) if is_inherent_impl_item || !self.stripped_mod => {
+                    debug_assert!(!item.is_stripped());
+
+                    // A crate has a module at its root, containing all items,
+                    // which should not be indexed. The crate-item itself is
+                    // inserted later on when serializing the search-index.
+                    if item.def_id.index != CRATE_DEF_INDEX {
+                        self.search_index.push(IndexItem {
+                            ty: item.type_(),
+                            name: s.to_string(),
+                            path: path.join("::"),
+                            desc: shorten(plain_summary_line(item.doc_value())),
+                            parent,
+                            parent_idx: None,
+                            search_type: get_index_search_type(&item),
+                        });
+
+                        for alias in item.attrs.get_doc_aliases() {
+                            self.aliases
+                                .entry(alias.to_lowercase())
+                                .or_insert(Vec::new())
+                                .push(self.search_index.len() - 1);
+                        }
+                    }
+                }
+                (Some(parent), None) if is_inherent_impl_item => {
+                    // We have a parent, but we don't know where they're
+                    // defined yet. Wait for later to index this item.
+                    self.orphan_impl_items.push((parent, item.clone()));
+                }
+                _ => {}
+            }
+        }
+
+        // Keep track of the fully qualified path for this item.
+        let pushed = match item.name {
+            Some(ref n) if !n.is_empty() => {
+                self.stack.push(n.to_string());
+                true
+            }
+            _ => false,
+        };
+
+        match item.inner {
+            clean::StructItem(..)
+            | clean::EnumItem(..)
+            | clean::TypedefItem(..)
+            | clean::TraitItem(..)
+            | clean::FunctionItem(..)
+            | clean::ModuleItem(..)
+            | clean::ForeignFunctionItem(..)
+            | clean::ForeignStaticItem(..)
+            | clean::ConstantItem(..)
+            | clean::StaticItem(..)
+            | clean::UnionItem(..)
+            | clean::ForeignTypeItem
+            | clean::MacroItem(..)
+            | clean::ProcMacroItem(..)
+            | clean::VariantItem(..)
+                if !self.stripped_mod =>
+            {
+                // Re-exported items mean that the same id can show up twice
+                // in the rustdoc ast that we're looking at. We know,
+                // however, that a re-exported item doesn't show up in the
+                // `public_items` map, so we can skip inserting into the
+                // paths map if there was already an entry present and we're
+                // not a public item.
+                if !self.paths.contains_key(&item.def_id)
+                    || self.access_levels.is_public(item.def_id)
+                {
+                    self.paths.insert(item.def_id, (self.stack.clone(), item.type_()));
+                }
+            }
+            clean::PrimitiveItem(..) => {
+                self.paths.insert(item.def_id, (self.stack.clone(), item.type_()));
+            }
+
+            _ => {}
+        }
+
+        // Maintain the parent stack
+        let orig_parent_is_trait_impl = self.parent_is_trait_impl;
+        let parent_pushed = match item.inner {
+            clean::TraitItem(..)
+            | clean::EnumItem(..)
+            | clean::ForeignTypeItem
+            | clean::StructItem(..)
+            | clean::UnionItem(..)
+            | clean::VariantItem(..) => {
+                self.parent_stack.push(item.def_id);
+                self.parent_is_trait_impl = false;
+                true
+            }
+            clean::ImplItem(ref i) => {
+                self.parent_is_trait_impl = i.trait_.is_some();
+                match i.for_ {
+                    clean::ResolvedPath { did, .. } => {
+                        self.parent_stack.push(did);
+                        true
+                    }
+                    ref t => {
+                        let prim_did = t
+                            .primitive_type()
+                            .and_then(|t| self.primitive_locations.get(&t).cloned());
+                        match prim_did {
+                            Some(did) => {
+                                self.parent_stack.push(did);
+                                true
+                            }
+                            None => false,
+                        }
+                    }
+                }
+            }
+            _ => false,
+        };
+
+        // Once we've recursively found all the generics, hoard off all the
+        // implementations elsewhere.
+        let ret = self.fold_item_recur(item).and_then(|item| {
+            if let clean::Item { inner: clean::ImplItem(_), .. } = item {
+                // Figure out the id of this impl. This may map to a
+                // primitive rather than always to a struct/enum.
+                // Note: matching twice to restrict the lifetime of the `i` borrow.
+                let mut dids = FxHashSet::default();
+                if let clean::Item { inner: clean::ImplItem(ref i), .. } = item {
+                    match i.for_ {
+                        clean::ResolvedPath { did, .. }
+                        | clean::BorrowedRef {
+                            type_: box clean::ResolvedPath { did, .. }, ..
+                        } => {
+                            dids.insert(did);
+                        }
+                        ref t => {
+                            let did = t
+                                .primitive_type()
+                                .and_then(|t| self.primitive_locations.get(&t).cloned());
+
+                            if let Some(did) = did {
+                                dids.insert(did);
+                            }
+                        }
+                    }
+
+                    if let Some(generics) = i.trait_.as_ref().and_then(|t| t.generics()) {
+                        for bound in generics {
+                            if let Some(did) = bound.def_id() {
+                                dids.insert(did);
+                            }
+                        }
+                    }
+                } else {
+                    unreachable!()
+                };
+                let impl_item = Impl { impl_item: item };
+                if impl_item.trait_did().map_or(true, |d| self.traits.contains_key(&d)) {
+                    for did in dids {
+                        self.impls.entry(did).or_insert(vec![]).push(impl_item.clone());
+                    }
+                } else {
+                    let trait_did = impl_item.trait_did().expect("no trait did");
+                    self.orphan_trait_impls.push((trait_did, dids, impl_item));
+                }
+                None
+            } else {
+                Some(item)
+            }
+        });
+
+        if pushed {
+            self.stack.pop().expect("stack already empty");
+        }
+        if parent_pushed {
+            self.parent_stack.pop().expect("parent stack already empty");
+        }
+        self.stripped_mod = orig_stripped_mod;
+        self.parent_is_trait_impl = orig_parent_is_trait_impl;
+        ret
+    }
+}
+
+crate fn cache() -> Arc<Cache> {
+    CACHE_KEY.with(|c| c.borrow().clone())
+}
diff --git a/src/librustdoc/html/item_type.rs b/src/librustdoc/formats/item_type.rs
index cc78b4682d2..696bdae94fc 100644
--- a/src/librustdoc/html/item_type.rs
+++ b/src/librustdoc/formats/item_type.rs
@@ -13,7 +13,7 @@ use crate::clean;
 /// The search index uses item types encoded as smaller numbers which equal to
 /// discriminants. JavaScript then is used to decode them into the original value.
 /// Consequently, every change to this type should be synchronized to
-/// the `itemTypes` mapping table in `static/main.js`.
+/// the `itemTypes` mapping table in `html/static/main.js`.
 ///
 /// In addition, code in `html::render` uses this enum to generate CSS classes, page prefixes, and
 /// module headings. If you are adding to this enum and want to ensure that the sidebar also prints
diff --git a/src/librustdoc/formats/mod.rs b/src/librustdoc/formats/mod.rs
index 55827f47385..2473f7758d2 100644
--- a/src/librustdoc/formats/mod.rs
+++ b/src/librustdoc/formats/mod.rs
@@ -1,107 +1,29 @@
-use std::cell::RefCell;
-use std::rc::Rc;
+pub mod cache;
+pub mod item_type;
+pub mod renderer;
 
-use rustc_span::edition::Edition;
+pub use renderer::{FormatRenderer, Renderer};
 
-use crate::clean;
-use crate::config::{RenderInfo, RenderOptions};
-use crate::error::Error;
-
-pub trait FormatRenderer: Clone {
-    type Output: FormatRenderer;
-
-    fn init(
-        krate: clean::Crate,
-        options: RenderOptions,
-        renderinfo: RenderInfo,
-        diag: &rustc_errors::Handler,
-        edition: Edition,
-        parent: Rc<RefCell<Renderer>>,
-    ) -> Result<(Self::Output, clean::Crate), Error>;
-
-    /// Renders a single non-module item. This means no recursive sub-item rendering is required.
-    fn item(&mut self, item: clean::Item) -> Result<(), Error>;
+use rustc_span::def_id::DefId;
 
-    /// Renders a module. Doesn't need to handle recursing into children, the driver does that
-    /// automatically.
-    fn mod_item_in(
-        &mut self,
-        item: &clean::Item,
-        item_name: &str,
-        module: &clean::Module,
-    ) -> Result<(), Error>;
-
-    /// Runs after recursively rendering all sub-items of a module.
-    fn mod_item_out(&mut self) -> Result<(), Error>;
-
-    /// Post processing hook for cleanup and dumping output to files.
-    fn after_krate(&mut self, krate: &clean::Crate) -> Result<(), Error>;
+use crate::clean;
+use crate::clean::types::GetDefId;
 
-    /// Called after everything else to write out errors.
-    fn after_run(&mut self, diag: &rustc_errors::Handler) -> Result<(), Error>;
+/// Metadata about implementations for a type or trait.
+#[derive(Clone, Debug)]
+pub struct Impl {
+    pub impl_item: clean::Item,
 }
 
-#[derive(Clone)]
-pub struct Renderer;
-
-impl Renderer {
-    pub fn new() -> Renderer {
-        Renderer
-    }
-
-    /// Main method for rendering a crate.
-    pub fn run<T: FormatRenderer + Clone>(
-        self,
-        krate: clean::Crate,
-        options: RenderOptions,
-        renderinfo: RenderInfo,
-        diag: &rustc_errors::Handler,
-        edition: Edition,
-    ) -> Result<(), Error> {
-        let rself = Rc::new(RefCell::new(self));
-        let (mut renderer, mut krate) =
-            T::init(krate, options, renderinfo, diag, edition, rself.clone())?;
-        let mut item = match krate.module.take() {
-            Some(i) => i,
-            None => return Ok(()),
-        };
-
-        item.name = Some(krate.name.clone());
-
-        // Render the crate documentation
-        let mut work = vec![(renderer.clone(), item)];
-
-        while let Some((mut cx, item)) = work.pop() {
-            if item.is_mod() {
-                // modules are special because they add a namespace. We also need to
-                // recurse into the items of the module as well.
-                let name = item.name.as_ref().unwrap().to_string();
-                if name.is_empty() {
-                    panic!("Unexpected module with empty name");
-                }
-
-                let module = match item.inner {
-                    clean::StrippedItem(box clean::ModuleItem(ref m))
-                    | clean::ModuleItem(ref m) => m,
-                    _ => unreachable!(),
-                };
-                cx.mod_item_in(&item, &name, module)?;
-                let module = match item.inner {
-                    clean::StrippedItem(box clean::ModuleItem(m)) | clean::ModuleItem(m) => m,
-                    _ => unreachable!(),
-                };
-                for it in module.items {
-                    info!("Adding {:?} to worklist", it.name);
-                    work.push((cx.clone(), it));
-                }
-
-                cx.mod_item_out()?;
-            } else if item.name.is_some() {
-                cx.item(item)?;
-            }
+impl Impl {
+    pub fn inner_impl(&self) -> &clean::Impl {
+        match self.impl_item.inner {
+            clean::ImplItem(ref impl_) => impl_,
+            _ => panic!("non-impl item found in impl"),
         }
+    }
 
-        renderer.after_krate(&krate)?;
-        renderer.after_run(diag)
+    pub fn trait_did(&self) -> Option<DefId> {
+        self.inner_impl().trait_.def_id()
     }
 }
diff --git a/src/librustdoc/formats/renderer.rs b/src/librustdoc/formats/renderer.rs
new file mode 100644
index 00000000000..f1862337ba1
--- /dev/null
+++ b/src/librustdoc/formats/renderer.rs
@@ -0,0 +1,112 @@
+use std::sync::Arc;
+
+use rustc_span::edition::Edition;
+
+use crate::clean;
+use crate::config::{RenderInfo, RenderOptions};
+use crate::error::Error;
+use crate::formats::cache::{Cache, CACHE_KEY};
+
+pub trait FormatRenderer: Clone {
+    type Output: FormatRenderer;
+
+    fn init(
+        krate: clean::Crate,
+        options: RenderOptions,
+        renderinfo: RenderInfo,
+        edition: Edition,
+        cache: &mut Cache,
+    ) -> Result<(Self::Output, clean::Crate), Error>;
+
+    /// Renders a single non-module item. This means no recursive sub-item rendering is required.
+    fn item(&mut self, item: clean::Item, cache: &Cache) -> Result<(), Error>;
+
+    /// Renders a module (doesn't need to handle recursing into children).
+    fn mod_item_in(
+        &mut self,
+        item: &clean::Item,
+        item_name: &str,
+        cache: &Cache,
+    ) -> Result<(), Error>;
+
+    /// Runs after recursively rendering all sub-items of a module.
+    fn mod_item_out(&mut self, name: &str) -> Result<(), Error>;
+
+    /// Post processing hook for cleanup and dumping output to files.
+    fn after_krate(&mut self, krate: &clean::Crate, cache: &Cache) -> Result<(), Error>;
+
+    /// Called after everything else to write out errors.
+    fn after_run(&mut self, diag: &rustc_errors::Handler) -> Result<(), Error>;
+}
+
+#[derive(Clone)]
+pub struct Renderer;
+
+impl Renderer {
+    pub fn new() -> Renderer {
+        Renderer
+    }
+
+    /// Main method for rendering a crate.
+    pub fn run<T: FormatRenderer + Clone>(
+        self,
+        krate: clean::Crate,
+        options: RenderOptions,
+        renderinfo: RenderInfo,
+        diag: &rustc_errors::Handler,
+        edition: Edition,
+    ) -> Result<(), Error> {
+        let (krate, mut cache) = Cache::from_krate(
+            renderinfo.clone(),
+            options.document_private,
+            &options.extern_html_root_urls,
+            &options.output,
+            krate,
+        );
+
+        let (mut renderer, mut krate) = T::init(krate, options, renderinfo, edition, &mut cache)?;
+
+        let cache = Arc::new(cache);
+        // Freeze the cache now that the index has been built. Put an Arc into TLS for future
+        // parallelization opportunities
+        CACHE_KEY.with(|v| *v.borrow_mut() = cache.clone());
+
+        let mut item = match krate.module.take() {
+            Some(i) => i,
+            None => return Ok(()),
+        };
+
+        item.name = Some(krate.name.clone());
+
+        // Render the crate documentation
+        let mut work = vec![(renderer.clone(), item)];
+
+        while let Some((mut cx, item)) = work.pop() {
+            if item.is_mod() {
+                // modules are special because they add a namespace. We also need to
+                // recurse into the items of the module as well.
+                let name = item.name.as_ref().unwrap().to_string();
+                if name.is_empty() {
+                    panic!("Unexpected module with empty name");
+                }
+
+                cx.mod_item_in(&item, &name, &cache)?;
+                let module = match item.inner {
+                    clean::StrippedItem(box clean::ModuleItem(m)) | clean::ModuleItem(m) => m,
+                    _ => unreachable!(),
+                };
+                for it in module.items {
+                    info!("Adding {:?} to worklist", it.name);
+                    work.push((cx.clone(), it));
+                }
+
+                cx.mod_item_out(&name)?;
+            } else if item.name.is_some() {
+                cx.item(item, &cache)?;
+            }
+        }
+
+        renderer.after_krate(&krate, &cache)?;
+        renderer.after_run(diag)
+    }
+}
diff --git a/src/librustdoc/html/format.rs b/src/librustdoc/html/format.rs
index 0d8284029af..699f8c36cba 100644
--- a/src/librustdoc/html/format.rs
+++ b/src/librustdoc/html/format.rs
@@ -11,13 +11,15 @@ use std::fmt;
 
 use rustc_data_structures::fx::FxHashSet;
 use rustc_hir as hir;
-use rustc_hir::def_id::DefId;
+use rustc_span::def_id::DefId;
 use rustc_target::spec::abi::Abi;
 
 use crate::clean::{self, PrimitiveType};
+use crate::formats::cache::cache;
+use crate::formats::item_type::ItemType;
 use crate::html::escape::Escape;
-use crate::html::item_type::ItemType;
-use crate::html::render::{self, cache, CURRENT_DEPTH};
+use crate::html::render::cache::ExternalLocation;
+use crate::html::render::CURRENT_DEPTH;
 
 pub trait Print {
     fn print(self, buffer: &mut Buffer);
@@ -493,9 +495,9 @@ pub fn href(did: DefId) -> Option<(String, ItemType, Vec<String>)> {
                 fqp,
                 shortty,
                 match cache.extern_locations[&did.krate] {
-                    (.., render::Remote(ref s)) => s.to_string(),
-                    (.., render::Local) => "../".repeat(depth),
-                    (.., render::Unknown) => return None,
+                    (.., ExternalLocation::Remote(ref s)) => s.to_string(),
+                    (.., ExternalLocation::Local) => "../".repeat(depth),
+                    (.., ExternalLocation::Unknown) => return None,
                 },
             )
         }
@@ -574,12 +576,12 @@ fn primitive_link(
             }
             Some(&def_id) => {
                 let loc = match m.extern_locations[&def_id.krate] {
-                    (ref cname, _, render::Remote(ref s)) => Some((cname, s.to_string())),
-                    (ref cname, _, render::Local) => {
+                    (ref cname, _, ExternalLocation::Remote(ref s)) => Some((cname, s.to_string())),
+                    (ref cname, _, ExternalLocation::Local) => {
                         let len = CURRENT_DEPTH.with(|s| s.get());
                         Some((cname, "../".repeat(len)))
                     }
-                    (.., render::Unknown) => None,
+                    (.., ExternalLocation::Unknown) => None,
                 };
                 if let Some((cname, root)) = loc {
                     write!(
diff --git a/src/librustdoc/html/mod.rs b/src/librustdoc/html/mod.rs
new file mode 100644
index 00000000000..367538d440e
--- /dev/null
+++ b/src/librustdoc/html/mod.rs
@@ -0,0 +1,9 @@
+crate mod escape;
+crate mod format;
+crate mod highlight;
+crate mod layout;
+pub mod markdown;
+pub mod render;
+crate mod sources;
+crate mod static_files;
+crate mod toc;
diff --git a/src/librustdoc/html/render/cache.rs b/src/librustdoc/html/render/cache.rs
index 6da4a4628e8..378efa1a1be 100644
--- a/src/librustdoc/html/render/cache.rs
+++ b/src/librustdoc/html/render/cache.rs
@@ -1,19 +1,16 @@
-use crate::clean::{self, AttributesExt, GetDefId};
-use crate::fold::DocFolder;
-use rustc_data_structures::fx::{FxHashMap, FxHashSet};
-use rustc_hir::def_id::{CrateNum, DefId, CRATE_DEF_INDEX};
-use rustc_middle::middle::privacy::AccessLevels;
-use rustc_span::source_map::FileName;
-use rustc_span::symbol::sym;
 use std::collections::BTreeMap;
-use std::mem;
-use std::path::{Path, PathBuf};
+use std::path::Path;
 
+use rustc_data_structures::fx::FxHashMap;
+use rustc_span::symbol::sym;
 use serde::Serialize;
 
-use super::{plain_summary_line, shorten, Impl, IndexItem, IndexItemFunctionType, ItemType};
-use super::{Generic, RenderType, TypeWithKind};
-use crate::config::RenderInfo;
+use crate::clean::types::GetDefId;
+use crate::clean::{self, AttributesExt};
+use crate::formats::cache::Cache;
+use crate::formats::item_type::ItemType;
+use crate::html::render::{plain_summary_line, shorten};
+use crate::html::render::{Generic, IndexItem, IndexItemFunctionType, RenderType, TypeWithKind};
 
 /// Indicates where an external crate can be found.
 pub enum ExternalLocation {
@@ -25,483 +22,9 @@ pub enum ExternalLocation {
     Unknown,
 }
 
-/// 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,
-/// documentation for all known traits, etc.
-///
-/// This structure purposefully does not implement `Clone` because it's intended
-/// to be a fairly large and expensive structure to clone. Instead this adheres
-/// to `Send` so it may be stored in a `Arc` instance and shared among the various
-/// rendering threads.
-#[derive(Default)]
-crate struct Cache {
-    /// Maps a type ID to all known implementations for that type. This is only
-    /// recognized for intra-crate `ResolvedPath` types, and is used to print
-    /// out extra documentation on the page of an enum/struct.
-    ///
-    /// The values of the map are a list of implementations and documentation
-    /// found on that implementation.
-    pub 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.
-    pub 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.
-    pub external_paths: FxHashMap<DefId, (Vec<String>, ItemType)>,
-
-    /// Maps local `DefId`s of exported types to fully qualified paths.
-    /// Unlike 'paths', this mapping ignores any renames that occur
-    /// due to 'use' statements.
-    ///
-    /// This map is used when writing out the special 'implementors'
-    /// javascript file. By using the exact path that the type
-    /// is declared with, we ensure that each path will be identical
-    /// to the path used if the corresponding type is inlined. By
-    /// doing this, we can detect duplicate impls on a trait page, and only display
-    /// the impl for the inlined type.
-    pub exact_paths: FxHashMap<DefId, Vec<String>>,
-
-    /// This map contains information about all known traits of this crate.
-    /// Implementations of a crate should inherit the documentation of the
-    /// parent trait if no extra documentation is specified, and default methods
-    /// should show up in documentation about trait implementations.
-    pub traits: FxHashMap<DefId, clean::Trait>,
-
-    /// When rendering traits, it's often useful to be able to list all
-    /// implementors of the trait, and this mapping is exactly, that: a mapping
-    /// of trait ids to the list of known implementors of the trait
-    pub implementors: FxHashMap<DefId, Vec<Impl>>,
-
-    /// Cache of where external crate documentation can be found.
-    pub extern_locations: FxHashMap<CrateNum, (String, PathBuf, ExternalLocation)>,
-
-    /// Cache of where documentation for primitives can be found.
-    pub primitive_locations: FxHashMap<clean::PrimitiveType, DefId>,
-
-    // Note that external items for which `doc(hidden)` applies to are shown as
-    // non-reachable while local items aren't. This is because we're reusing
-    // the access levels from the privacy check pass.
-    pub access_levels: AccessLevels<DefId>,
-
-    /// The version of the crate being documented, if given from the `--crate-version` flag.
-    pub crate_version: Option<String>,
-
-    /// Whether to document private items.
-    /// This is stored in `Cache` so it doesn't need to be passed through all rustdoc functions.
-    pub document_private: bool,
-
-    // Private fields only used when initially crawling a crate to build a cache
-    stack: Vec<String>,
-    parent_stack: Vec<DefId>,
-    parent_is_trait_impl: bool,
-    search_index: Vec<IndexItem>,
-    stripped_mod: bool,
-    pub deref_trait_did: Option<DefId>,
-    pub deref_mut_trait_did: Option<DefId>,
-    pub owned_box_did: Option<DefId>,
-    masked_crates: FxHashSet<CrateNum>,
-
-    // In rare case where a structure is defined in one module but implemented
-    // in another, if the implementing module is parsed before defining module,
-    // then the fully qualified name of the structure isn't presented in `paths`
-    // yet when its implementation methods are being indexed. Caches such methods
-    // and their parent id here and indexes them at the end of crate parsing.
-    orphan_impl_items: Vec<(DefId, clean::Item)>,
-
-    // Similarly to `orphan_impl_items`, sometimes trait impls are picked up
-    // even though the trait itself is not exported. This can happen if a trait
-    // was defined in function/expression scope, since the impl will be picked
-    // up by `collect-trait-impls` but the trait won't be scraped out in the HIR
-    // crawl. In order to prevent crashes when looking for spotlight traits or
-    // when gathering trait documentation on a type, hold impls here while
-    // folding and add them to the cache later on if we find the trait.
-    orphan_trait_impls: Vec<(DefId, FxHashSet<DefId>, Impl)>,
-
-    /// Aliases added through `#[doc(alias = "...")]`. Since a few items can have the same alias,
-    /// we need the alias element to have an array of items.
-    pub(super) aliases: BTreeMap<String, Vec<usize>>,
-}
-
-impl Cache {
-    pub fn from_krate(
-        renderinfo: RenderInfo,
-        document_private: bool,
-        extern_html_root_urls: &BTreeMap<String, String>,
-        dst: &Path,
-        mut krate: clean::Crate,
-    ) -> (clean::Crate, String, Cache) {
-        // Crawl the crate to build various caches used for the output
-        let RenderInfo {
-            inlined: _,
-            external_paths,
-            exact_paths,
-            access_levels,
-            deref_trait_did,
-            deref_mut_trait_did,
-            owned_box_did,
-            ..
-        } = renderinfo;
-
-        let external_paths =
-            external_paths.into_iter().map(|(k, (v, t))| (k, (v, ItemType::from(t)))).collect();
-
-        let mut cache = Cache {
-            impls: Default::default(),
-            external_paths,
-            exact_paths,
-            paths: Default::default(),
-            implementors: Default::default(),
-            stack: Vec::new(),
-            parent_stack: Vec::new(),
-            search_index: Vec::new(),
-            parent_is_trait_impl: false,
-            extern_locations: Default::default(),
-            primitive_locations: Default::default(),
-            stripped_mod: false,
-            access_levels,
-            crate_version: krate.version.take(),
-            document_private,
-            orphan_impl_items: Vec::new(),
-            orphan_trait_impls: Vec::new(),
-            traits: krate.external_traits.replace(Default::default()),
-            deref_trait_did,
-            deref_mut_trait_did,
-            owned_box_did,
-            masked_crates: mem::take(&mut krate.masked_crates),
-            aliases: Default::default(),
-        };
-
-        // Cache where all our extern crates are located
-        for &(n, ref e) in &krate.externs {
-            let src_root = match e.src {
-                FileName::Real(ref p) => match p.local_path().parent() {
-                    Some(p) => p.to_path_buf(),
-                    None => PathBuf::new(),
-                },
-                _ => PathBuf::new(),
-            };
-            let extern_url = extern_html_root_urls.get(&e.name).map(|u| &**u);
-            cache
-                .extern_locations
-                .insert(n, (e.name.clone(), src_root, extern_location(e, extern_url, &dst)));
-
-            let did = DefId { krate: n, index: CRATE_DEF_INDEX };
-            cache.external_paths.insert(did, (vec![e.name.to_string()], ItemType::Module));
-        }
-
-        // Cache where all known primitives have their documentation located.
-        //
-        // Favor linking to as local extern as possible, so iterate all crates in
-        // reverse topological order.
-        for &(_, ref e) in krate.externs.iter().rev() {
-            for &(def_id, prim, _) in &e.primitives {
-                cache.primitive_locations.insert(prim, def_id);
-            }
-        }
-        for &(def_id, prim, _) in &krate.primitives {
-            cache.primitive_locations.insert(prim, def_id);
-        }
-
-        cache.stack.push(krate.name.clone());
-        krate = cache.fold_crate(krate);
-
-        for (trait_did, dids, impl_) in cache.orphan_trait_impls.drain(..) {
-            if cache.traits.contains_key(&trait_did) {
-                for did in dids {
-                    cache.impls.entry(did).or_insert(vec![]).push(impl_.clone());
-                }
-            }
-        }
-
-        // Build our search index
-        let index = build_index(&krate, &mut cache);
-
-        (krate, index, cache)
-    }
-}
-
-impl DocFolder for Cache {
-    fn fold_item(&mut self, item: clean::Item) -> Option<clean::Item> {
-        if item.def_id.is_local() {
-            debug!("folding {} \"{:?}\", id {:?}", item.type_(), item.name, item.def_id);
-        }
-
-        // If this is a stripped module,
-        // we don't want it or its children in the search index.
-        let orig_stripped_mod = match item.inner {
-            clean::StrippedItem(box clean::ModuleItem(..)) => {
-                mem::replace(&mut self.stripped_mod, true)
-            }
-            _ => self.stripped_mod,
-        };
-
-        // If the impl is from a masked crate or references something from a
-        // masked crate then remove it completely.
-        if let clean::ImplItem(ref i) = item.inner {
-            if self.masked_crates.contains(&item.def_id.krate)
-                || i.trait_.def_id().map_or(false, |d| self.masked_crates.contains(&d.krate))
-                || i.for_.def_id().map_or(false, |d| self.masked_crates.contains(&d.krate))
-            {
-                return None;
-            }
-        }
-
-        // Propagate a trait method's documentation to all implementors of the
-        // trait.
-        if let clean::TraitItem(ref t) = item.inner {
-            self.traits.entry(item.def_id).or_insert_with(|| t.clone());
-        }
-
-        // Collect all the implementors of traits.
-        if let clean::ImplItem(ref i) = item.inner {
-            if let Some(did) = i.trait_.def_id() {
-                if i.blanket_impl.is_none() {
-                    self.implementors
-                        .entry(did)
-                        .or_default()
-                        .push(Impl { impl_item: item.clone() });
-                }
-            }
-        }
-
-        // Index this method for searching later on.
-        if let Some(ref s) = item.name {
-            let (parent, is_inherent_impl_item) = match item.inner {
-                clean::StrippedItem(..) => ((None, None), false),
-                clean::AssocConstItem(..) | clean::TypedefItem(_, true)
-                    if self.parent_is_trait_impl =>
-                {
-                    // skip associated items in trait impls
-                    ((None, None), false)
-                }
-                clean::AssocTypeItem(..)
-                | clean::TyMethodItem(..)
-                | clean::StructFieldItem(..)
-                | clean::VariantItem(..) => (
-                    (
-                        Some(*self.parent_stack.last().expect("parent_stack is empty")),
-                        Some(&self.stack[..self.stack.len() - 1]),
-                    ),
-                    false,
-                ),
-                clean::MethodItem(..) | clean::AssocConstItem(..) => {
-                    if self.parent_stack.is_empty() {
-                        ((None, None), false)
-                    } else {
-                        let last = self.parent_stack.last().expect("parent_stack is empty 2");
-                        let did = *last;
-                        let path = match self.paths.get(&did) {
-                            // The current stack not necessarily has correlation
-                            // for where the type was defined. On the other
-                            // hand, `paths` always has the right
-                            // information if present.
-                            Some(&(
-                                ref fqp,
-                                ItemType::Trait
-                                | ItemType::Struct
-                                | ItemType::Union
-                                | ItemType::Enum,
-                            )) => Some(&fqp[..fqp.len() - 1]),
-                            Some(..) => Some(&*self.stack),
-                            None => None,
-                        };
-                        ((Some(*last), path), true)
-                    }
-                }
-                _ => ((None, Some(&*self.stack)), false),
-            };
-
-            match parent {
-                (parent, Some(path)) if is_inherent_impl_item || !self.stripped_mod => {
-                    debug_assert!(!item.is_stripped());
-
-                    // A crate has a module at its root, containing all items,
-                    // which should not be indexed. The crate-item itself is
-                    // inserted later on when serializing the search-index.
-                    if item.def_id.index != CRATE_DEF_INDEX {
-                        self.search_index.push(IndexItem {
-                            ty: item.type_(),
-                            name: s.to_string(),
-                            path: path.join("::"),
-                            desc: shorten(plain_summary_line(item.doc_value())),
-                            parent,
-                            parent_idx: None,
-                            search_type: get_index_search_type(&item),
-                        });
-
-                        for alias in item.attrs.get_doc_aliases() {
-                            self.aliases
-                                .entry(alias.to_lowercase())
-                                .or_insert(Vec::new())
-                                .push(self.search_index.len() - 1);
-                        }
-                    }
-                }
-                (Some(parent), None) if is_inherent_impl_item => {
-                    // We have a parent, but we don't know where they're
-                    // defined yet. Wait for later to index this item.
-                    self.orphan_impl_items.push((parent, item.clone()));
-                }
-                _ => {}
-            }
-        }
-
-        // Keep track of the fully qualified path for this item.
-        let pushed = match item.name {
-            Some(ref n) if !n.is_empty() => {
-                self.stack.push(n.to_string());
-                true
-            }
-            _ => false,
-        };
-
-        match item.inner {
-            clean::StructItem(..)
-            | clean::EnumItem(..)
-            | clean::TypedefItem(..)
-            | clean::TraitItem(..)
-            | clean::FunctionItem(..)
-            | clean::ModuleItem(..)
-            | clean::ForeignFunctionItem(..)
-            | clean::ForeignStaticItem(..)
-            | clean::ConstantItem(..)
-            | clean::StaticItem(..)
-            | clean::UnionItem(..)
-            | clean::ForeignTypeItem
-            | clean::MacroItem(..)
-            | clean::ProcMacroItem(..)
-            | clean::VariantItem(..)
-                if !self.stripped_mod =>
-            {
-                // Re-exported items mean that the same id can show up twice
-                // in the rustdoc ast that we're looking at. We know,
-                // however, that a re-exported item doesn't show up in the
-                // `public_items` map, so we can skip inserting into the
-                // paths map if there was already an entry present and we're
-                // not a public item.
-                if !self.paths.contains_key(&item.def_id)
-                    || self.access_levels.is_public(item.def_id)
-                {
-                    self.paths.insert(item.def_id, (self.stack.clone(), item.type_()));
-                }
-            }
-            clean::PrimitiveItem(..) => {
-                self.paths.insert(item.def_id, (self.stack.clone(), item.type_()));
-            }
-
-            _ => {}
-        }
-
-        // Maintain the parent stack
-        let orig_parent_is_trait_impl = self.parent_is_trait_impl;
-        let parent_pushed = match item.inner {
-            clean::TraitItem(..)
-            | clean::EnumItem(..)
-            | clean::ForeignTypeItem
-            | clean::StructItem(..)
-            | clean::UnionItem(..)
-            | clean::VariantItem(..) => {
-                self.parent_stack.push(item.def_id);
-                self.parent_is_trait_impl = false;
-                true
-            }
-            clean::ImplItem(ref i) => {
-                self.parent_is_trait_impl = i.trait_.is_some();
-                match i.for_ {
-                    clean::ResolvedPath { did, .. } => {
-                        self.parent_stack.push(did);
-                        true
-                    }
-                    ref t => {
-                        let prim_did = t
-                            .primitive_type()
-                            .and_then(|t| self.primitive_locations.get(&t).cloned());
-                        match prim_did {
-                            Some(did) => {
-                                self.parent_stack.push(did);
-                                true
-                            }
-                            None => false,
-                        }
-                    }
-                }
-            }
-            _ => false,
-        };
-
-        // Once we've recursively found all the generics, hoard off all the
-        // implementations elsewhere.
-        let ret = self.fold_item_recur(item).and_then(|item| {
-            if let clean::Item { inner: clean::ImplItem(_), .. } = item {
-                // Figure out the id of this impl. This may map to a
-                // primitive rather than always to a struct/enum.
-                // Note: matching twice to restrict the lifetime of the `i` borrow.
-                let mut dids = FxHashSet::default();
-                if let clean::Item { inner: clean::ImplItem(ref i), .. } = item {
-                    match i.for_ {
-                        clean::ResolvedPath { did, .. }
-                        | clean::BorrowedRef {
-                            type_: box clean::ResolvedPath { did, .. }, ..
-                        } => {
-                            dids.insert(did);
-                        }
-                        ref t => {
-                            let did = t
-                                .primitive_type()
-                                .and_then(|t| self.primitive_locations.get(&t).cloned());
-
-                            if let Some(did) = did {
-                                dids.insert(did);
-                            }
-                        }
-                    }
-
-                    if let Some(generics) = i.trait_.as_ref().and_then(|t| t.generics()) {
-                        for bound in generics {
-                            if let Some(did) = bound.def_id() {
-                                dids.insert(did);
-                            }
-                        }
-                    }
-                } else {
-                    unreachable!()
-                };
-                let impl_item = Impl { impl_item: item };
-                if impl_item.trait_did().map_or(true, |d| self.traits.contains_key(&d)) {
-                    for did in dids {
-                        self.impls.entry(did).or_insert(vec![]).push(impl_item.clone());
-                    }
-                } else {
-                    let trait_did = impl_item.trait_did().expect("no trait did");
-                    self.orphan_trait_impls.push((trait_did, dids, impl_item));
-                }
-                None
-            } else {
-                Some(item)
-            }
-        });
-
-        if pushed {
-            self.stack.pop().expect("stack already empty");
-        }
-        if parent_pushed {
-            self.parent_stack.pop().expect("parent stack already empty");
-        }
-        self.stripped_mod = orig_stripped_mod;
-        self.parent_is_trait_impl = orig_parent_is_trait_impl;
-        ret
-    }
-}
-
 /// Attempts to find where an external crate is located, given that we're
 /// rendering in to the specified source destination.
-fn extern_location(
+pub fn extern_location(
     e: &clean::ExternalCrate,
     extern_url: Option<&str>,
     dst: &Path,
@@ -539,7 +62,7 @@ fn extern_location(
 }
 
 /// Builds the search index from the collected metadata
-fn build_index(krate: &clean::Crate, cache: &mut Cache) -> String {
+pub fn build_index(krate: &clean::Crate, cache: &mut Cache) -> String {
     let mut defid_to_pathid = FxHashMap::default();
     let mut crate_items = Vec::with_capacity(cache.search_index.len());
     let mut crate_paths = vec![];
@@ -641,7 +164,7 @@ fn build_index(krate: &clean::Crate, cache: &mut Cache) -> String {
     )
 }
 
-fn get_index_search_type(item: &clean::Item) -> Option<IndexItemFunctionType> {
+crate fn get_index_search_type(item: &clean::Item) -> Option<IndexItemFunctionType> {
     let (all_types, ret_types) = match item.inner {
         clean::FunctionItem(ref f) => (&f.all_types, &f.ret_types),
         clean::MethodItem(ref m) => (&m.all_types, &m.ret_types),
diff --git a/src/librustdoc/html/render.rs b/src/librustdoc/html/render/mod.rs
index fd32ba66d91..1678cff16a9 100644
--- a/src/librustdoc/html/render.rs
+++ b/src/librustdoc/html/render/mod.rs
@@ -25,6 +25,11 @@
 //! These threads are not parallelized (they haven't been a bottleneck yet), and
 //! both occur before the crate is rendered.
 
+pub mod cache;
+
+#[cfg(test)]
+mod tests;
+
 use std::borrow::Cow;
 use std::cell::{Cell, RefCell};
 use std::cmp::Ordering;
@@ -63,24 +68,18 @@ use crate::config::RenderOptions;
 use crate::docfs::{DocFS, ErrorStorage, PathError};
 use crate::doctree;
 use crate::error::Error;
-use crate::formats::{FormatRenderer, Renderer};
+use crate::formats::cache::{cache, Cache};
+use crate::formats::item_type::ItemType;
+use crate::formats::{FormatRenderer, Impl};
 use crate::html::escape::Escape;
 use crate::html::format::fmt_impl_for_trait_page;
 use crate::html::format::Function;
 use crate::html::format::{href, print_default_space, print_generic_bounds, WhereClause};
 use crate::html::format::{print_abi_with_space, Buffer, PrintWithSpace};
-use crate::html::item_type::ItemType;
 use crate::html::markdown::{self, ErrorCodes, IdMap, Markdown, MarkdownHtml, MarkdownSummaryLine};
 use crate::html::sources;
 use crate::html::{highlight, layout, static_files};
-
-#[cfg(test)]
-mod tests;
-
-mod cache;
-
-use cache::Cache;
-crate use cache::ExternalLocation::{self, *};
+use cache::{build_index, ExternalLocation};
 
 /// A pair of name and its optional document.
 pub type NameDoc = (String, Option<String>);
@@ -113,8 +112,6 @@ crate struct Context {
     /// The map used to ensure all generated 'id=' attributes are unique.
     id_map: Rc<RefCell<IdMap>>,
     pub shared: Arc<SharedContext>,
-    pub cache: Arc<Cache>,
-    pub parent: Rc<RefCell<Renderer>>,
     all: Rc<RefCell<AllTypes>>,
     pub errors: Arc<ErrorStorage>,
 }
@@ -196,39 +193,20 @@ impl SharedContext {
     }
 }
 
-/// Metadata about implementations for a type or trait.
-#[derive(Clone, Debug)]
-pub struct Impl {
-    pub impl_item: clean::Item,
-}
-
-impl Impl {
-    fn inner_impl(&self) -> &clean::Impl {
-        match self.impl_item.inner {
-            clean::ImplItem(ref impl_) => impl_,
-            _ => panic!("non-impl item found in impl"),
-        }
-    }
-
-    fn trait_did(&self) -> Option<DefId> {
-        self.inner_impl().trait_.def_id()
-    }
-}
-
 // Helper structs for rendering items/sidebars and carrying along contextual
 // information
 
 /// Struct representing one entry in the JS search index. These are all emitted
 /// by hand to a large JS file at the end of cache-creation.
 #[derive(Debug)]
-struct IndexItem {
-    ty: ItemType,
-    name: String,
-    path: String,
-    desc: String,
-    parent: Option<DefId>,
-    parent_idx: Option<usize>,
-    search_type: Option<IndexItemFunctionType>,
+pub struct IndexItem {
+    pub ty: ItemType,
+    pub name: String,
+    pub path: String,
+    pub desc: String,
+    pub parent: Option<DefId>,
+    pub parent_idx: Option<usize>,
+    pub search_type: Option<IndexItemFunctionType>,
 }
 
 impl Serialize for IndexItem {
@@ -250,7 +228,7 @@ impl Serialize for IndexItem {
 
 /// A type used for the search index.
 #[derive(Debug)]
-struct RenderType {
+pub struct RenderType {
     ty: Option<DefId>,
     idx: Option<usize>,
     name: Option<String>,
@@ -281,7 +259,7 @@ impl Serialize for RenderType {
 
 /// A type used for the search index.
 #[derive(Debug)]
-struct Generic {
+pub struct Generic {
     name: String,
     defid: Option<DefId>,
     idx: Option<usize>,
@@ -302,7 +280,7 @@ impl Serialize for Generic {
 
 /// Full type of functions/methods in the search index.
 #[derive(Debug)]
-struct IndexItemFunctionType {
+pub struct IndexItemFunctionType {
     inputs: Vec<TypeWithKind>,
     output: Option<Vec<TypeWithKind>>,
 }
@@ -367,7 +345,6 @@ pub struct StylePath {
     pub disabled: bool,
 }
 
-thread_local!(static CACHE_KEY: RefCell<Arc<Cache>> = Default::default());
 thread_local!(pub static CURRENT_DEPTH: Cell<usize> = Cell::new(0));
 
 pub fn initial_ids() -> Vec<String> {
@@ -401,10 +378,9 @@ impl FormatRenderer for Context {
     fn init(
         mut krate: clean::Crate,
         options: RenderOptions,
-        renderinfo: RenderInfo,
-        _diag: &rustc_errors::Handler,
+        _renderinfo: RenderInfo,
         edition: Edition,
-        parent: Rc<RefCell<Renderer>>,
+        cache: &mut Cache,
     ) -> Result<(Context, clean::Crate), Error> {
         // need to save a copy of the options for rendering the index page
         let md_opts = options.clone();
@@ -416,11 +392,9 @@ impl FormatRenderer for Context {
             sort_modules_alphabetically,
             themes: style_files,
             extension_css,
-            extern_html_root_urls,
             resource_suffix,
             static_root_path,
             generate_search_filter,
-            document_private,
             ..
         } = options;
 
@@ -509,9 +483,10 @@ impl FormatRenderer for Context {
         let dst = output;
         scx.ensure_dir(&dst)?;
         krate = sources::render(&dst, &mut scx, krate)?;
-        let (new_crate, index, cache) =
-            Cache::from_krate(renderinfo, document_private, &extern_html_root_urls, &dst, krate);
-        krate = new_crate;
+
+        // Build our search index
+        let index = build_index(&krate, cache);
+
         let cache = Arc::new(cache);
         let mut cx = Context {
             current: Vec::new(),
@@ -519,20 +494,15 @@ impl FormatRenderer for Context {
             render_redirect_pages: false,
             id_map: Rc::new(RefCell::new(id_map)),
             shared: Arc::new(scx),
-            cache: cache.clone(),
-            parent,
             all: Rc::new(RefCell::new(AllTypes::new())),
             errors,
         };
 
-        // Freeze the cache now that the index has been built. Put an Arc into TLS
-        // for future parallelization opportunities
-        CACHE_KEY.with(|v| *v.borrow_mut() = cache.clone());
         CURRENT_DEPTH.with(|s| s.set(0));
 
         // Write shared runs within a flock; disable thread dispatching of IO temporarily.
         Arc::get_mut(&mut cx.shared).unwrap().fs.set_sync_only(true);
-        write_shared(&cx, &krate, index, &md_opts)?;
+        write_shared(&cx, &krate, index, &md_opts, &cache)?;
         Arc::get_mut(&mut cx.shared).unwrap().fs.set_sync_only(false);
         Ok((cx, krate))
     }
@@ -547,7 +517,7 @@ impl FormatRenderer for Context {
         }
     }
 
-    fn after_krate(&mut self, krate: &clean::Crate) -> Result<(), Error> {
+    fn after_krate(&mut self, krate: &clean::Crate, cache: &Cache) -> Result<(), Error> {
         let final_file = self.dst.join(&krate.name).join("all.html");
         let settings_file = self.dst.join("settings.html");
         let crate_name = krate.name.clone();
@@ -567,7 +537,7 @@ impl FormatRenderer for Context {
             extra_scripts: &[],
             static_extra_scripts: &[],
         };
-        let sidebar = if let Some(ref version) = self.cache.crate_version {
+        let sidebar = if let Some(ref version) = cache.crate_version {
             format!(
                 "<p class='location'>Crate {}</p>\
                      <div class='block version'>\
@@ -616,7 +586,7 @@ impl FormatRenderer for Context {
         &mut self,
         item: &clean::Item,
         item_name: &str,
-        module: &clean::Module,
+        cache: &Cache,
     ) -> Result<(), Error> {
         // Stripped modules survive the rustdoc passes (i.e., `strip-private`)
         // if they contain impls for public types. These modules can also
@@ -634,7 +604,7 @@ impl FormatRenderer for Context {
 
         info!("Recursing into {}", self.dst.display());
 
-        let buf = self.render_item(item, false);
+        let buf = self.render_item(item, false, cache);
         // buf will be empty if the module is stripped and there is no redirect for it
         if !buf.is_empty() {
             self.shared.ensure_dir(&self.dst)?;
@@ -644,6 +614,10 @@ impl FormatRenderer for Context {
 
         // Render sidebar-items.js used throughout this module.
         if !self.render_redirect_pages {
+            let module = match item.inner {
+                clean::StrippedItem(box clean::ModuleItem(ref m)) | clean::ModuleItem(ref m) => m,
+                _ => unreachable!(),
+            };
             let items = self.build_sidebar_items(module);
             let js_dst = self.dst.join("sidebar-items.js");
             let v = format!("initSidebarItems({});", serde_json::to_string(&items).unwrap());
@@ -652,7 +626,7 @@ impl FormatRenderer for Context {
         Ok(())
     }
 
-    fn mod_item_out(&mut self) -> Result<(), Error> {
+    fn mod_item_out(&mut self, _name: &str) -> Result<(), Error> {
         info!("Recursed; leaving {}", self.dst.display());
 
         // Go back to where we were at
@@ -661,7 +635,7 @@ impl FormatRenderer for Context {
         Ok(())
     }
 
-    fn item(&mut self, item: clean::Item) -> Result<(), Error> {
+    fn item(&mut self, item: clean::Item, cache: &Cache) -> Result<(), Error> {
         // Stripped modules survive the rustdoc passes (i.e., `strip-private`)
         // if they contain impls for public types. These modules can also
         // contain items such as publicly re-exported structures.
@@ -673,7 +647,7 @@ impl FormatRenderer for Context {
             self.render_redirect_pages = item.is_stripped();
         }
 
-        let buf = self.render_item(&item, true);
+        let buf = self.render_item(&item, true, cache);
         // buf will be empty if the item is stripped and there is no redirect for it
         if !buf.is_empty() {
             let name = item.name.as_ref().unwrap();
@@ -704,6 +678,7 @@ fn write_shared(
     krate: &clean::Crate,
     search_index: String,
     options: &RenderOptions,
+    cache: &Cache,
 ) -> Result<(), Error> {
     // Write out the shared files. Note that these are shared among all rustdoc
     // docs placed in the output directory, so this needs to be a synchronized
@@ -1101,7 +1076,7 @@ themePicker.onblur = handleThemeButtonsBlur;
 
     // Update the list of all implementors for traits
     let dst = cx.dst.join("implementors");
-    for (&did, imps) in &cx.cache.implementors {
+    for (&did, imps) in &cache.implementors {
         // Private modules can leak through to this phase of rustdoc, which
         // could contain implementations for otherwise private types. In some
         // rare cases we could find an implementation for an item which wasn't
@@ -1109,9 +1084,9 @@ themePicker.onblur = handleThemeButtonsBlur;
         //
         // 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) {
+        let &(ref remote_path, remote_item_type) = match cache.paths.get(&did) {
             Some(p) => p,
-            None => match cx.cache.external_paths.get(&did) {
+            None => match cache.external_paths.get(&did) {
                 Some(p) => p,
                 None => continue,
             },
@@ -1149,7 +1124,7 @@ themePicker.onblur = handleThemeButtonsBlur;
         // 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() && !cache.paths.contains_key(&did) {
             continue;
         }
 
@@ -1454,7 +1429,7 @@ impl Context {
         "../".repeat(self.current.len())
     }
 
-    fn render_item(&self, it: &clean::Item, pushname: bool) -> String {
+    fn render_item(&self, it: &clean::Item, pushname: bool, cache: &Cache) -> String {
         // A little unfortunate that this is done like this, but it sure
         // does make formatting *a lot* nicer.
         CURRENT_DEPTH.with(|slot| {
@@ -1507,13 +1482,13 @@ impl Context {
             layout::render(
                 &self.shared.layout,
                 &page,
-                |buf: &mut _| print_sidebar(self, it, buf),
-                |buf: &mut _| print_item(self, it, buf),
+                |buf: &mut _| print_sidebar(self, it, buf, cache),
+                |buf: &mut _| print_item(self, it, buf, cache),
                 &self.shared.style_files,
             )
         } else {
             let mut url = self.root_path();
-            if let Some(&(ref names, ty)) = self.cache.paths.get(&it.def_id) {
+            if let Some(&(ref names, ty)) = cache.paths.get(&it.def_id) {
                 for name in &names[..names.len() - 1] {
                     url.push_str(name);
                     url.push_str("/");
@@ -1552,9 +1527,7 @@ impl Context {
         }
         map
     }
-}
 
-impl Context {
     /// Generates a url appropriate for an `href` attribute back to the source of
     /// this item.
     ///
@@ -1564,7 +1537,7 @@ impl Context {
     /// If `None` is returned, then a source link couldn't be generated. This
     /// may happen, for example, with externally inlined items where the source
     /// of their crate documentation isn't known.
-    fn src_href(&self, item: &clean::Item) -> Option<String> {
+    fn src_href(&self, item: &clean::Item, cache: &Cache) -> Option<String> {
         let mut root = self.root_path();
 
         let mut path = String::new();
@@ -1583,13 +1556,13 @@ impl Context {
                 return None;
             }
         } else {
-            let (krate, src_root) = match *self.cache.extern_locations.get(&item.source.cnum)? {
-                (ref name, ref src, Local) => (name, src),
-                (ref name, ref src, Remote(ref s)) => {
+            let (krate, src_root) = match *cache.extern_locations.get(&item.source.cnum)? {
+                (ref name, ref src, ExternalLocation::Local) => (name, src),
+                (ref name, ref src, ExternalLocation::Remote(ref s)) => {
                     root = s.to_string();
                     (name, src)
                 }
-                (_, _, Unknown) => return None,
+                (_, _, ExternalLocation::Unknown) => return None,
             };
 
             sources::clean_path(&src_root, file, false, |component| {
@@ -1626,7 +1599,7 @@ where
     write!(w, "</div>")
 }
 
-fn print_item(cx: &Context, item: &clean::Item, buf: &mut Buffer) {
+fn print_item(cx: &Context, item: &clean::Item, buf: &mut Buffer, cache: &Cache) {
     debug_assert!(!item.is_stripped());
     // Write the breadcrumb trail header for the top
     write!(buf, "<h1 class='fqn'><span class='out-of-band'>");
@@ -1654,7 +1627,7 @@ fn print_item(cx: &Context, item: &clean::Item, buf: &mut Buffer) {
     // this page, and this link will be auto-clicked. The `id` attribute is
     // used to find the link to auto-click.
     if cx.shared.include_sources && !item.is_primitive() {
-        if let Some(l) = cx.src_href(item) {
+        if let Some(l) = cx.src_href(item, cache) {
             write!(buf, "<a class='srclink' href='{}' title='{}'>[src]</a>", l, "goto source code");
         }
     }
@@ -1715,20 +1688,20 @@ fn print_item(cx: &Context, item: &clean::Item, buf: &mut Buffer) {
         clean::FunctionItem(ref f) | clean::ForeignFunctionItem(ref f) => {
             item_function(buf, cx, item, f)
         }
-        clean::TraitItem(ref t) => item_trait(buf, cx, item, t),
-        clean::StructItem(ref s) => item_struct(buf, cx, item, s),
-        clean::UnionItem(ref s) => item_union(buf, cx, item, s),
-        clean::EnumItem(ref e) => item_enum(buf, cx, item, e),
-        clean::TypedefItem(ref t, _) => item_typedef(buf, cx, item, t),
+        clean::TraitItem(ref t) => item_trait(buf, cx, item, t, cache),
+        clean::StructItem(ref s) => item_struct(buf, cx, item, s, cache),
+        clean::UnionItem(ref s) => item_union(buf, cx, item, s, cache),
+        clean::EnumItem(ref e) => item_enum(buf, cx, item, e, cache),
+        clean::TypedefItem(ref t, _) => item_typedef(buf, cx, item, t, cache),
         clean::MacroItem(ref m) => item_macro(buf, cx, item, m),
         clean::ProcMacroItem(ref m) => item_proc_macro(buf, cx, item, m),
-        clean::PrimitiveItem(_) => item_primitive(buf, cx, item),
+        clean::PrimitiveItem(_) => item_primitive(buf, cx, item, cache),
         clean::StaticItem(ref i) | clean::ForeignStaticItem(ref i) => item_static(buf, cx, item, i),
         clean::ConstantItem(ref c) => item_constant(buf, cx, item, c),
-        clean::ForeignTypeItem => item_foreign_type(buf, cx, item),
+        clean::ForeignTypeItem => item_foreign_type(buf, cx, item, cache),
         clean::KeywordItem(_) => item_keyword(buf, cx, item),
-        clean::OpaqueTyItem(ref e, _) => item_opaque_ty(buf, cx, item, e),
-        clean::TraitAliasItem(ref ta) => item_trait_alias(buf, cx, item, ta),
+        clean::OpaqueTyItem(ref e, _) => item_opaque_ty(buf, cx, item, e, cache),
+        clean::TraitAliasItem(ref ta) => item_trait_alias(buf, cx, item, ta, cache),
         _ => {
             // We don't generate pages for any other type.
             unreachable!();
@@ -1751,7 +1724,7 @@ fn full_path(cx: &Context, item: &clean::Item) -> String {
 }
 
 #[inline]
-fn plain_summary_line(s: Option<&str>) -> String {
+crate fn plain_summary_line(s: Option<&str>) -> String {
     let s = s.unwrap_or("");
     // This essentially gets the first paragraph of text in one line.
     let mut line = s
@@ -1768,7 +1741,7 @@ fn plain_summary_line(s: Option<&str>) -> String {
     markdown::plain_summary_line(&line[..])
 }
 
-fn shorten(s: String) -> String {
+crate fn shorten(s: String) -> String {
     if s.chars().count() > 60 {
         let mut len = 0;
         let mut ret = s
@@ -2338,6 +2311,7 @@ fn render_implementor(
     w: &mut Buffer,
     implementor_dups: &FxHashMap<&str, (DefId, bool)>,
     aliases: &[String],
+    cache: &Cache,
 ) {
     // If there's already another implementor that has the same abbridged name, use the
     // full path, for example in `std::iter::ExactSizeIterator`
@@ -2361,10 +2335,17 @@ fn render_implementor(
         false,
         false,
         aliases,
+        cache,
     );
 }
 
-fn render_impls(cx: &Context, w: &mut Buffer, traits: &[&&Impl], containing_item: &clean::Item) {
+fn render_impls(
+    cx: &Context,
+    w: &mut Buffer,
+    traits: &[&&Impl],
+    containing_item: &clean::Item,
+    cache: &Cache,
+) {
     let mut impls = traits
         .iter()
         .map(|i| {
@@ -2383,6 +2364,7 @@ fn render_impls(cx: &Context, w: &mut Buffer, traits: &[&&Impl], containing_item
                 false,
                 true,
                 &[],
+                cache,
             );
             buffer.into_inner()
         })
@@ -2415,7 +2397,7 @@ fn compare_impl<'a, 'b>(lhs: &'a &&Impl, rhs: &'b &&Impl) -> Ordering {
     name_key(&lhs).cmp(&name_key(&rhs))
 }
 
-fn item_trait(w: &mut Buffer, cx: &Context, it: &clean::Item, t: &clean::Trait) {
+fn item_trait(w: &mut Buffer, cx: &Context, it: &clean::Item, t: &clean::Trait, cache: &Cache) {
     let bounds = bounds(&t.bounds, false);
     let types = t.items.iter().filter(|m| m.is_associated_type()).collect::<Vec<_>>();
     let consts = t.items.iter().filter(|m| m.is_associated_const()).collect::<Vec<_>>();
@@ -2575,9 +2557,9 @@ fn item_trait(w: &mut Buffer, cx: &Context, it: &clean::Item, t: &clean::Trait)
     }
 
     // If there are methods directly on this trait object, render them here.
-    render_assoc_items(w, cx, it, it.def_id, AssocItemRender::All);
+    render_assoc_items(w, cx, it, it.def_id, AssocItemRender::All, cache);
 
-    if let Some(implementors) = cx.cache.implementors.get(&it.def_id) {
+    if let Some(implementors) = cache.implementors.get(&it.def_id) {
         // The DefId is for the first Type found with that name. The bool is
         // if any Types with the same name but different DefId have been found.
         let mut implementor_dups: FxHashMap<&str, (DefId, bool)> = FxHashMap::default();
@@ -2599,7 +2581,7 @@ fn item_trait(w: &mut Buffer, cx: &Context, it: &clean::Item, t: &clean::Trait)
         }
 
         let (local, foreign) = implementors.iter().partition::<Vec<_>, _>(|i| {
-            i.inner_impl().for_.def_id().map_or(true, |d| cx.cache.paths.contains_key(&d))
+            i.inner_impl().for_.def_id().map_or(true, |d| cache.paths.contains_key(&d))
         });
 
         let (mut synthetic, mut concrete): (Vec<&&Impl>, Vec<&&Impl>) =
@@ -2628,6 +2610,7 @@ fn item_trait(w: &mut Buffer, cx: &Context, it: &clean::Item, t: &clean::Trait)
                     true,
                     false,
                     &[],
+                    cache,
                 );
             }
             write_loading_content(w, "");
@@ -2640,7 +2623,7 @@ fn item_trait(w: &mut Buffer, cx: &Context, it: &clean::Item, t: &clean::Trait)
             "<div class='item-list' id='implementors-list'>",
         );
         for implementor in concrete {
-            render_implementor(cx, implementor, w, &implementor_dups, &[]);
+            render_implementor(cx, implementor, w, &implementor_dups, &[], cache);
         }
         write_loading_content(w, "</div>");
 
@@ -2658,6 +2641,7 @@ fn item_trait(w: &mut Buffer, cx: &Context, it: &clean::Item, t: &clean::Trait)
                     w,
                     &implementor_dups,
                     &collect_paths_for_type(implementor.inner_impl().for_.clone()),
+                    cache,
                 );
             }
             write_loading_content(w, "</div>");
@@ -2693,7 +2677,7 @@ fn item_trait(w: &mut Buffer, cx: &Context, it: &clean::Item, t: &clean::Trait)
         path = if it.def_id.is_local() {
             cx.current.join("/")
         } else {
-            let (ref path, _) = cx.cache.external_paths[&it.def_id];
+            let (ref path, _) = cache.external_paths[&it.def_id];
             path[..path.len() - 1].join("/")
         },
         ty = it.type_(),
@@ -2702,7 +2686,7 @@ fn item_trait(w: &mut Buffer, cx: &Context, it: &clean::Item, t: &clean::Trait)
 }
 
 fn naive_assoc_href(it: &clean::Item, link: AssocItemLink<'_>) -> String {
-    use crate::html::item_type::ItemType::*;
+    use crate::formats::item_type::ItemType::*;
 
     let name = it.name.as_ref().unwrap();
     let ty = match it.type_() {
@@ -2868,7 +2852,7 @@ fn render_assoc_item(
     }
 }
 
-fn item_struct(w: &mut Buffer, cx: &Context, it: &clean::Item, s: &clean::Struct) {
+fn item_struct(w: &mut Buffer, cx: &Context, it: &clean::Item, s: &clean::Struct, cache: &Cache) {
     wrap_into_docblock(w, |w| {
         write!(w, "<pre class='rust struct'>");
         render_attributes(w, it, true);
@@ -2915,10 +2899,10 @@ fn item_struct(w: &mut Buffer, cx: &Context, it: &clean::Item, s: &clean::Struct
             }
         }
     }
-    render_assoc_items(w, cx, it, it.def_id, AssocItemRender::All)
+    render_assoc_items(w, cx, it, it.def_id, AssocItemRender::All, cache)
 }
 
-fn item_union(w: &mut Buffer, cx: &Context, it: &clean::Item, s: &clean::Union) {
+fn item_union(w: &mut Buffer, cx: &Context, it: &clean::Item, s: &clean::Union, cache: &Cache) {
     wrap_into_docblock(w, |w| {
         write!(w, "<pre class='rust union'>");
         render_attributes(w, it, true);
@@ -2961,10 +2945,10 @@ fn item_union(w: &mut Buffer, cx: &Context, it: &clean::Item, s: &clean::Union)
             document(w, cx, field);
         }
     }
-    render_assoc_items(w, cx, it, it.def_id, AssocItemRender::All)
+    render_assoc_items(w, cx, it, it.def_id, AssocItemRender::All, cache)
 }
 
-fn item_enum(w: &mut Buffer, cx: &Context, it: &clean::Item, e: &clean::Enum) {
+fn item_enum(w: &mut Buffer, cx: &Context, it: &clean::Item, e: &clean::Enum, cache: &Cache) {
     wrap_into_docblock(w, |w| {
         write!(w, "<pre class='rust enum'>");
         render_attributes(w, it, true);
@@ -3089,7 +3073,7 @@ fn item_enum(w: &mut Buffer, cx: &Context, it: &clean::Item, e: &clean::Enum) {
             render_stability_since(w, variant, it);
         }
     }
-    render_assoc_items(w, cx, it, it.def_id, AssocItemRender::All)
+    render_assoc_items(w, cx, it, it.def_id, AssocItemRender::All, cache)
 }
 
 const ALLOWED_ATTRIBUTES: &[Symbol] = &[
@@ -3288,9 +3272,9 @@ fn render_assoc_items(
     containing_item: &clean::Item,
     it: DefId,
     what: AssocItemRender<'_>,
+    cache: &Cache,
 ) {
-    let c = &cx.cache;
-    let v = match c.impls.get(&it) {
+    let v = match cache.impls.get(&it) {
         Some(v) => v,
         None => return,
     };
@@ -3336,6 +3320,7 @@ fn render_assoc_items(
                 false,
                 true,
                 &[],
+                cache,
             );
         }
     }
@@ -3344,11 +3329,11 @@ fn render_assoc_items(
     }
     if !traits.is_empty() {
         let deref_impl =
-            traits.iter().find(|t| t.inner_impl().trait_.def_id() == c.deref_trait_did);
+            traits.iter().find(|t| t.inner_impl().trait_.def_id() == cache.deref_trait_did);
         if let Some(impl_) = deref_impl {
             let has_deref_mut =
-                traits.iter().any(|t| t.inner_impl().trait_.def_id() == c.deref_mut_trait_did);
-            render_deref_methods(w, cx, impl_, containing_item, has_deref_mut);
+                traits.iter().any(|t| t.inner_impl().trait_.def_id() == cache.deref_mut_trait_did);
+            render_deref_methods(w, cx, impl_, containing_item, has_deref_mut, cache);
         }
 
         let (synthetic, concrete): (Vec<&&Impl>, Vec<&&Impl>) =
@@ -3357,7 +3342,7 @@ fn render_assoc_items(
             concrete.into_iter().partition(|t| t.inner_impl().blanket_impl.is_some());
 
         let mut impls = Buffer::empty_from(&w);
-        render_impls(cx, &mut impls, &concrete, containing_item);
+        render_impls(cx, &mut impls, &concrete, containing_item, cache);
         let impls = impls.into_inner();
         if !impls.is_empty() {
             write!(
@@ -3382,7 +3367,7 @@ fn render_assoc_items(
                 <div id='synthetic-implementations-list'>\
             "
             );
-            render_impls(cx, w, &synthetic, containing_item);
+            render_impls(cx, w, &synthetic, containing_item, cache);
             write!(w, "</div>");
         }
 
@@ -3397,7 +3382,7 @@ fn render_assoc_items(
                 <div id='blanket-implementations-list'>\
             "
             );
-            render_impls(cx, w, &blanket_impl, containing_item);
+            render_impls(cx, w, &blanket_impl, containing_item, cache);
             write!(w, "</div>");
         }
     }
@@ -3409,6 +3394,7 @@ fn render_deref_methods(
     impl_: &Impl,
     container_item: &clean::Item,
     deref_mut: bool,
+    cache: &Cache,
 ) {
     let deref_type = impl_.inner_impl().trait_.as_ref().unwrap();
     let (target, real_target) = impl_
@@ -3426,11 +3412,11 @@ fn render_deref_methods(
     let what =
         AssocItemRender::DerefFor { trait_: deref_type, type_: real_target, deref_mut_: deref_mut };
     if let Some(did) = target.def_id() {
-        render_assoc_items(w, cx, container_item, did, what);
+        render_assoc_items(w, cx, container_item, did, what, cache);
     } else {
         if let Some(prim) = target.primitive_type() {
-            if let Some(&did) = cx.cache.primitive_locations.get(&prim) {
-                render_assoc_items(w, cx, container_item, did, what);
+            if let Some(&did) = cache.primitive_locations.get(&prim) {
+                render_assoc_items(w, cx, container_item, did, what, cache);
             }
         }
     }
@@ -3532,6 +3518,7 @@ fn render_impl(
     // This argument is used to reference same type with different paths to avoid duplication
     // in documentation pages for trait with automatic implementations like "Send" and "Sync".
     aliases: &[String],
+    cache: &Cache,
 ) {
     if render_mode == RenderMode::Normal {
         let id = cx.derive_id(match i.inner_impl().trait_ {
@@ -3574,7 +3561,7 @@ fn render_impl(
         write!(w, "<a href='#{}' class='anchor'></a>", id);
         let since = i.impl_item.stability.as_ref().map(|s| &s.since[..]);
         render_stability_since_raw(w, since, outer_version);
-        if let Some(l) = cx.src_href(&i.impl_item) {
+        if let Some(l) = cx.src_href(&i.impl_item, cache) {
             write!(w, "<a class='srclink' href='{}' title='{}'>[src]</a>", l, "goto source code");
         }
         write!(w, "</h3>");
@@ -3606,6 +3593,7 @@ fn render_impl(
         outer_version: Option<&str>,
         trait_: Option<&clean::Trait>,
         show_def_docs: bool,
+        cache: &Cache,
     ) {
         let item_type = item.type_();
         let name = item.name.as_ref().unwrap();
@@ -3634,7 +3622,7 @@ fn render_impl(
                     render_assoc_item(w, item, link.anchor(&id), ItemType::Impl);
                     write!(w, "</code>");
                     render_stability_since_raw(w, item.stable_since(), outer_version);
-                    if let Some(l) = cx.src_href(item) {
+                    if let Some(l) = cx.src_href(item, cache) {
                         write!(
                             w,
                             "<a class='srclink' href='{}' title='{}'>[src]</a>",
@@ -3656,7 +3644,7 @@ fn render_impl(
                 assoc_const(w, item, ty, default.as_ref(), link.anchor(&id), "");
                 write!(w, "</code>");
                 render_stability_since_raw(w, item.stable_since(), outer_version);
-                if let Some(l) = cx.src_href(item) {
+                if let Some(l) = cx.src_href(item, cache) {
                     write!(
                         w,
                         "<a class='srclink' href='{}' title='{}'>[src]</a>",
@@ -3707,7 +3695,7 @@ fn render_impl(
         }
     }
 
-    let traits = &cx.cache.traits;
+    let traits = &cache.traits;
     let trait_ = i.trait_did().map(|did| &traits[&did]);
 
     write!(w, "<div class='impl-items'>");
@@ -3722,6 +3710,7 @@ fn render_impl(
             outer_version,
             trait_,
             show_def_docs,
+            cache,
         );
     }
 
@@ -3733,6 +3722,7 @@ fn render_impl(
         render_mode: RenderMode,
         outer_version: Option<&str>,
         show_def_docs: bool,
+        cache: &Cache,
     ) {
         for trait_item in &t.items {
             let n = trait_item.name.clone();
@@ -3752,6 +3742,7 @@ fn render_impl(
                 outer_version,
                 None,
                 show_def_docs,
+                cache,
             );
         }
     }
@@ -3770,13 +3761,20 @@ fn render_impl(
                 render_mode,
                 outer_version,
                 show_def_docs,
+                cache,
             );
         }
     }
     write!(w, "</div>");
 }
 
-fn item_opaque_ty(w: &mut Buffer, cx: &Context, it: &clean::Item, t: &clean::OpaqueTy) {
+fn item_opaque_ty(
+    w: &mut Buffer,
+    cx: &Context,
+    it: &clean::Item,
+    t: &clean::OpaqueTy,
+    cache: &Cache,
+) {
     write!(w, "<pre class='rust opaque'>");
     render_attributes(w, it, false);
     write!(
@@ -3794,10 +3792,16 @@ fn item_opaque_ty(w: &mut Buffer, cx: &Context, it: &clean::Item, t: &clean::Opa
     // won't be visible anywhere in the docs. It would be nice to also show
     // associated items from the aliased type (see discussion in #32077), but
     // we need #14072 to make sense of the generics.
-    render_assoc_items(w, cx, it, it.def_id, AssocItemRender::All)
+    render_assoc_items(w, cx, it, it.def_id, AssocItemRender::All, cache)
 }
 
-fn item_trait_alias(w: &mut Buffer, cx: &Context, it: &clean::Item, t: &clean::TraitAlias) {
+fn item_trait_alias(
+    w: &mut Buffer,
+    cx: &Context,
+    it: &clean::Item,
+    t: &clean::TraitAlias,
+    cache: &Cache,
+) {
     write!(w, "<pre class='rust trait-alias'>");
     render_attributes(w, it, false);
     write!(
@@ -3815,10 +3819,10 @@ fn item_trait_alias(w: &mut Buffer, cx: &Context, it: &clean::Item, t: &clean::T
     // won't be visible anywhere in the docs. It would be nice to also show
     // associated items from the aliased type (see discussion in #32077), but
     // we need #14072 to make sense of the generics.
-    render_assoc_items(w, cx, it, it.def_id, AssocItemRender::All)
+    render_assoc_items(w, cx, it, it.def_id, AssocItemRender::All, cache)
 }
 
-fn item_typedef(w: &mut Buffer, cx: &Context, it: &clean::Item, t: &clean::Typedef) {
+fn item_typedef(w: &mut Buffer, cx: &Context, it: &clean::Item, t: &clean::Typedef, cache: &Cache) {
     write!(w, "<pre class='rust typedef'>");
     render_attributes(w, it, false);
     write!(
@@ -3836,10 +3840,10 @@ fn item_typedef(w: &mut Buffer, cx: &Context, it: &clean::Item, t: &clean::Typed
     // won't be visible anywhere in the docs. It would be nice to also show
     // associated items from the aliased type (see discussion in #32077), but
     // we need #14072 to make sense of the generics.
-    render_assoc_items(w, cx, it, it.def_id, AssocItemRender::All)
+    render_assoc_items(w, cx, it, it.def_id, AssocItemRender::All, cache)
 }
 
-fn item_foreign_type(w: &mut Buffer, cx: &Context, it: &clean::Item) {
+fn item_foreign_type(w: &mut Buffer, cx: &Context, it: &clean::Item, cache: &Cache) {
     writeln!(w, "<pre class='rust foreigntype'>extern {{");
     render_attributes(w, it, false);
     write!(
@@ -3851,10 +3855,10 @@ fn item_foreign_type(w: &mut Buffer, cx: &Context, it: &clean::Item) {
 
     document(w, cx, it);
 
-    render_assoc_items(w, cx, it, it.def_id, AssocItemRender::All)
+    render_assoc_items(w, cx, it, it.def_id, AssocItemRender::All, cache)
 }
 
-fn print_sidebar(cx: &Context, it: &clean::Item, buffer: &mut Buffer) {
+fn print_sidebar(cx: &Context, it: &clean::Item, buffer: &mut Buffer, cache: &Cache) {
     let parentlen = cx.current.len() - if it.is_mod() { 1 } else { 0 };
 
     if it.is_struct()
@@ -3889,7 +3893,7 @@ fn print_sidebar(cx: &Context, it: &clean::Item, buffer: &mut Buffer) {
     }
 
     if it.is_crate() {
-        if let Some(ref version) = cx.cache.crate_version {
+        if let Some(ref version) = cache.crate_version {
             write!(
                 buffer,
                 "<div class='block version'>\
@@ -4526,9 +4530,9 @@ fn item_proc_macro(w: &mut Buffer, cx: &Context, it: &clean::Item, m: &clean::Pr
     document(w, cx, it)
 }
 
-fn item_primitive(w: &mut Buffer, cx: &Context, it: &clean::Item) {
+fn item_primitive(w: &mut Buffer, cx: &Context, it: &clean::Item, cache: &Cache) {
     document(w, cx, it);
-    render_assoc_items(w, cx, it, it.def_id, AssocItemRender::All)
+    render_assoc_items(w, cx, it, it.def_id, AssocItemRender::All, cache)
 }
 
 fn item_keyword(w: &mut Buffer, cx: &Context, it: &clean::Item) {
@@ -4593,7 +4597,3 @@ fn collect_paths_for_type(first_ty: clean::Type) -> Vec<String> {
     }
     out
 }
-
-crate fn cache() -> Arc<Cache> {
-    CACHE_KEY.with(|c| c.borrow().clone())
-}
diff --git a/src/librustdoc/lib.rs b/src/librustdoc/lib.rs
index 715956ea172..0de9c6336bb 100644
--- a/src/librustdoc/lib.rs
+++ b/src/librustdoc/lib.rs
@@ -66,19 +66,8 @@ mod doctree;
 #[macro_use]
 mod error;
 mod fold;
-mod formats;
-pub mod html {
-    crate mod escape;
-    crate mod format;
-    crate mod highlight;
-    crate mod item_type;
-    crate mod layout;
-    pub mod markdown;
-    crate mod render;
-    crate mod sources;
-    crate mod static_files;
-    crate mod toc;
-}
+crate mod formats;
+crate mod html;
 mod markdown;
 mod passes;
 mod test;