Create new types.rs file

1 files changed, 4551 insertions, 0 deletions

diff --git a/src/librustdoc/clean/types.rs b/src/librustdoc/clean/types.rs
new file mode 100644
index 00000000000..4d8d0040cdc
--- /dev/null
+++ b/src/librustdoc/clean/types.rs
@@ -0,0 +1,4551 @@
+// ignore-tidy-filelength
+
+//! This module contains the "cleaned" pieces of the AST, and the functions
+//! that clean them.
+
+pub mod inline;
+pub mod cfg;
+mod simplify;
+mod auto_trait;
+mod blanket_impl;
+
+use rustc_index::vec::{IndexVec, Idx};
+use rustc_target::spec::abi::Abi;
+use rustc_typeck::hir_ty_to_ty;
+use rustc::infer::region_constraints::{RegionConstraintData, Constraint};
+use rustc::middle::resolve_lifetime as rl;
+use rustc::middle::lang_items;
+use rustc::middle::stability;
+use rustc::mir::interpret::GlobalId;
+use rustc::hir;
+use rustc::hir::def::{CtorKind, DefKind, Res};
+use rustc::hir::def_id::{CrateNum, DefId, CRATE_DEF_INDEX, LOCAL_CRATE};
+use rustc::hir::ptr::P;
+use rustc::ty::subst::{InternalSubsts, SubstsRef, GenericArgKind};
+use rustc::ty::{self, DefIdTree, TyCtxt, Region, RegionVid, Ty, AdtKind};
+use rustc::ty::fold::TypeFolder;
+use rustc::ty::layout::VariantIdx;
+use rustc::util::nodemap::{FxHashMap, FxHashSet};
+use syntax::ast::{self, Attribute, AttrStyle, AttrKind, Ident};
+use syntax::attr;
+use syntax::util::comments;
+use syntax::source_map::DUMMY_SP;
+use syntax_pos::symbol::{Symbol, kw, sym};
+use syntax_pos::hygiene::MacroKind;
+use syntax_pos::{self, Pos, FileName};
+
+use std::collections::hash_map::Entry;
+use std::fmt;
+use std::hash::{Hash, Hasher};
+use std::default::Default;
+use std::{mem, slice, vec};
+use std::num::NonZeroU32;
+use std::iter::FromIterator;
+use std::rc::Rc;
+use std::cell::RefCell;
+use std::sync::Arc;
+use std::u32;
+
+use crate::core::{self, DocContext, ImplTraitParam};
+use crate::doctree;
+use crate::html::render::{cache, ExternalLocation};
+use crate::html::item_type::ItemType;
+
+
+use self::cfg::Cfg;
+use self::auto_trait::AutoTraitFinder;
+use self::blanket_impl::BlanketImplFinder;
+
+pub use self::Type::*;
+pub use self::Mutability::*;
+pub use self::ItemEnum::*;
+pub use self::SelfTy::*;
+pub use self::FunctionRetTy::*;
+pub use self::Visibility::{Public, Inherited};
+
+thread_local!(pub static MAX_DEF_ID: RefCell<FxHashMap<CrateNum, DefId>> = Default::default());
+
+const FN_OUTPUT_NAME: &'static str = "Output";
+
+// extract the stability index for a node from tcx, if possible
+fn get_stability(cx: &DocContext<'_>, def_id: DefId) -> Option<Stability> {
+    cx.tcx.lookup_stability(def_id).clean(cx)
+}
+
+fn get_deprecation(cx: &DocContext<'_>, def_id: DefId) -> Option<Deprecation> {
+    cx.tcx.lookup_deprecation(def_id).clean(cx)
+}
+
+pub trait Clean<T> {
+    fn clean(&self, cx: &DocContext<'_>) -> T;
+}
+
+impl<T: Clean<U>, U> Clean<Vec<U>> for [T] {
+    fn clean(&self, cx: &DocContext<'_>) -> Vec<U> {
+        self.iter().map(|x| x.clean(cx)).collect()
+    }
+}
+
+impl<T: Clean<U>, U, V: Idx> Clean<IndexVec<V, U>> for IndexVec<V, T> {
+    fn clean(&self, cx: &DocContext<'_>) -> IndexVec<V, U> {
+        self.iter().map(|x| x.clean(cx)).collect()
+    }
+}
+
+impl<T: Clean<U>, U> Clean<U> for P<T> {
+    fn clean(&self, cx: &DocContext<'_>) -> U {
+        (**self).clean(cx)
+    }
+}
+
+impl<T: Clean<U>, U> Clean<U> for Rc<T> {
+    fn clean(&self, cx: &DocContext<'_>) -> U {
+        (**self).clean(cx)
+    }
+}
+
+impl<T: Clean<U>, U> Clean<Option<U>> for Option<T> {
+    fn clean(&self, cx: &DocContext<'_>) -> Option<U> {
+        self.as_ref().map(|v| v.clean(cx))
+    }
+}
+
+impl<T, U> Clean<U> for ty::Binder<T> where T: Clean<U> {
+    fn clean(&self, cx: &DocContext<'_>) -> U {
+        self.skip_binder().clean(cx)
+    }
+}
+
+impl<T: Clean<U>, U> Clean<Vec<U>> for P<[T]> {
+    fn clean(&self, cx: &DocContext<'_>) -> Vec<U> {
+        self.iter().map(|x| x.clean(cx)).collect()
+    }
+}
+
+#[derive(Clone, Debug)]
+pub struct Crate {
+    pub name: String,
+    pub version: Option<String>,
+    pub src: FileName,
+    pub module: Option<Item>,
+    pub externs: Vec<(CrateNum, ExternalCrate)>,
+    pub primitives: Vec<(DefId, PrimitiveType, Attributes)>,
+    // These are later on moved into `CACHEKEY`, leaving the map empty.
+    // Only here so that they can be filtered through the rustdoc passes.
+    pub external_traits: Rc<RefCell<FxHashMap<DefId, Trait>>>,
+    pub masked_crates: FxHashSet<CrateNum>,
+    pub collapsed: bool,
+}
+
+pub fn krate(mut cx: &mut DocContext<'_>) -> Crate {
+    use crate::visit_lib::LibEmbargoVisitor;
+
+    let krate = cx.tcx.hir().krate();
+    let module = crate::visit_ast::RustdocVisitor::new(&mut cx).visit(krate);
+
+    let mut r = cx.renderinfo.get_mut();
+    r.deref_trait_did = cx.tcx.lang_items().deref_trait();
+    r.deref_mut_trait_did = cx.tcx.lang_items().deref_mut_trait();
+    r.owned_box_did = cx.tcx.lang_items().owned_box();
+
+    let mut externs = Vec::new();
+    for &cnum in cx.tcx.crates().iter() {
+        externs.push((cnum, cnum.clean(cx)));
+        // Analyze doc-reachability for extern items
+        LibEmbargoVisitor::new(&mut cx).visit_lib(cnum);
+    }
+    externs.sort_by(|&(a, _), &(b, _)| a.cmp(&b));
+
+    // Clean the crate, translating the entire libsyntax AST to one that is
+    // understood by rustdoc.
+    let mut module = module.clean(cx);
+    let mut masked_crates = FxHashSet::default();
+
+    match module.inner {
+        ModuleItem(ref module) => {
+            for it in &module.items {
+                // `compiler_builtins` should be masked too, but we can't apply
+                // `#[doc(masked)]` to the injected `extern crate` because it's unstable.
+                if it.is_extern_crate()
+                    && (it.attrs.has_doc_flag(sym::masked)
+                        || cx.tcx.is_compiler_builtins(it.def_id.krate))
+                {
+                    masked_crates.insert(it.def_id.krate);
+                }
+            }
+        }
+        _ => unreachable!(),
+    }
+
+    let ExternalCrate { name, src, primitives, keywords, .. } = LOCAL_CRATE.clean(cx);
+    {
+        let m = match module.inner {
+            ModuleItem(ref mut m) => m,
+            _ => unreachable!(),
+        };
+        m.items.extend(primitives.iter().map(|&(def_id, prim, ref attrs)| {
+            Item {
+                source: Span::empty(),
+                name: Some(prim.to_url_str().to_string()),
+                attrs: attrs.clone(),
+                visibility: Public,
+                stability: get_stability(cx, def_id),
+                deprecation: get_deprecation(cx, def_id),
+                def_id,
+                inner: PrimitiveItem(prim),
+            }
+        }));
+        m.items.extend(keywords.into_iter().map(|(def_id, kw, attrs)| {
+            Item {
+                source: Span::empty(),
+                name: Some(kw.clone()),
+                attrs,
+                visibility: Public,
+                stability: get_stability(cx, def_id),
+                deprecation: get_deprecation(cx, def_id),
+                def_id,
+                inner: KeywordItem(kw),
+            }
+        }));
+    }
+
+    Crate {
+        name,
+        version: None,
+        src,
+        module: Some(module),
+        externs,
+        primitives,
+        external_traits: cx.external_traits.clone(),
+        masked_crates,
+        collapsed: false,
+    }
+}
+
+#[derive(Clone, Debug)]
+pub struct ExternalCrate {
+    pub name: String,
+    pub src: FileName,
+    pub attrs: Attributes,
+    pub primitives: Vec<(DefId, PrimitiveType, Attributes)>,
+    pub keywords: Vec<(DefId, String, Attributes)>,
+}
+
+impl Clean<ExternalCrate> for CrateNum {
+    fn clean(&self, cx: &DocContext<'_>) -> ExternalCrate {
+        let root = DefId { krate: *self, index: CRATE_DEF_INDEX };
+        let krate_span = cx.tcx.def_span(root);
+        let krate_src = cx.sess().source_map().span_to_filename(krate_span);
+
+        // Collect all inner modules which are tagged as implementations of
+        // primitives.
+        //
+        // Note that this loop only searches the top-level items of the crate,
+        // and this is intentional. If we were to search the entire crate for an
+        // item tagged with `#[doc(primitive)]` then we would also have to
+        // search the entirety of external modules for items tagged
+        // `#[doc(primitive)]`, which is a pretty inefficient process (decoding
+        // all that metadata unconditionally).
+        //
+        // In order to keep the metadata load under control, the
+        // `#[doc(primitive)]` feature is explicitly designed to only allow the
+        // primitive tags to show up as the top level items in a crate.
+        //
+        // Also note that this does not attempt to deal with modules tagged
+        // duplicately for the same primitive. This is handled later on when
+        // rendering by delegating everything to a hash map.
+        let as_primitive = |res: Res| {
+            if let Res::Def(DefKind::Mod, def_id) = res {
+                let attrs = cx.tcx.get_attrs(def_id).clean(cx);
+                let mut prim = None;
+                for attr in attrs.lists(sym::doc) {
+                    if let Some(v) = attr.value_str() {
+                        if attr.check_name(sym::primitive) {
+                            prim = PrimitiveType::from_str(&v.as_str());
+                            if prim.is_some() {
+                                break;
+                            }
+                            // FIXME: should warn on unknown primitives?
+                        }
+                    }
+                }
+                return prim.map(|p| (def_id, p, attrs));
+            }
+            None
+        };
+        let primitives = if root.is_local() {
+            cx.tcx.hir().krate().module.item_ids.iter().filter_map(|&id| {
+                let item = cx.tcx.hir().expect_item(id.id);
+                match item.kind {
+                    hir::ItemKind::Mod(_) => {
+                        as_primitive(Res::Def(
+                            DefKind::Mod,
+                            cx.tcx.hir().local_def_id(id.id),
+                        ))
+                    }
+                    hir::ItemKind::Use(ref path, hir::UseKind::Single)
+                    if item.vis.node.is_pub() => {
+                        as_primitive(path.res).map(|(_, prim, attrs)| {
+                            // Pretend the primitive is local.
+                            (cx.tcx.hir().local_def_id(id.id), prim, attrs)
+                        })
+                    }
+                    _ => None
+                }
+            }).collect()
+        } else {
+            cx.tcx.item_children(root).iter().map(|item| item.res)
+              .filter_map(as_primitive).collect()
+        };
+
+        let as_keyword = |res: Res| {
+            if let Res::Def(DefKind::Mod, def_id) = res {
+                let attrs = cx.tcx.get_attrs(def_id).clean(cx);
+                let mut keyword = None;
+                for attr in attrs.lists(sym::doc) {
+                    if let Some(v) = attr.value_str() {
+                        if attr.check_name(sym::keyword) {
+                            if v.is_doc_keyword() {
+                                keyword = Some(v.to_string());
+                                break;
+                            }
+                            // FIXME: should warn on unknown keywords?
+                        }
+                    }
+                }
+                return keyword.map(|p| (def_id, p, attrs));
+            }
+            None
+        };
+        let keywords = if root.is_local() {
+            cx.tcx.hir().krate().module.item_ids.iter().filter_map(|&id| {
+                let item = cx.tcx.hir().expect_item(id.id);
+                match item.kind {
+                    hir::ItemKind::Mod(_) => {
+                        as_keyword(Res::Def(
+                            DefKind::Mod,
+                            cx.tcx.hir().local_def_id(id.id),
+                        ))
+                    }
+                    hir::ItemKind::Use(ref path, hir::UseKind::Single)
+                    if item.vis.node.is_pub() => {
+                        as_keyword(path.res).map(|(_, prim, attrs)| {
+                            (cx.tcx.hir().local_def_id(id.id), prim, attrs)
+                        })
+                    }
+                    _ => None
+                }
+            }).collect()
+        } else {
+            cx.tcx.item_children(root).iter().map(|item| item.res)
+              .filter_map(as_keyword).collect()
+        };
+
+        ExternalCrate {
+            name: cx.tcx.crate_name(*self).to_string(),
+            src: krate_src,
+            attrs: cx.tcx.get_attrs(root).clean(cx),
+            primitives,
+            keywords,
+        }
+    }
+}
+
+/// Anything with a source location and set of attributes and, optionally, a
+/// name. That is, anything that can be documented. This doesn't correspond
+/// directly to the AST's concept of an item; it's a strict superset.
+#[derive(Clone)]
+pub struct Item {
+    /// Stringified span
+    pub source: Span,
+    /// Not everything has a name. E.g., impls
+    pub name: Option<String>,
+    pub attrs: Attributes,
+    pub inner: ItemEnum,
+    pub visibility: Visibility,
+    pub def_id: DefId,
+    pub stability: Option<Stability>,
+    pub deprecation: Option<Deprecation>,
+}
+
+impl fmt::Debug for Item {
+    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+
+        let fake = MAX_DEF_ID.with(|m| m.borrow().get(&self.def_id.krate)
+                                   .map(|id| self.def_id >= *id).unwrap_or(false));
+        let def_id: &dyn fmt::Debug = if fake { &"**FAKE**" } else { &self.def_id };
+
+        fmt.debug_struct("Item")
+            .field("source", &self.source)
+            .field("name", &self.name)
+            .field("attrs", &self.attrs)
+            .field("inner", &self.inner)
+            .field("visibility", &self.visibility)
+            .field("def_id", def_id)
+            .field("stability", &self.stability)
+            .field("deprecation", &self.deprecation)
+            .finish()
+    }
+}
+
+impl Item {
+    /// Finds the `doc` attribute as a NameValue and returns the corresponding
+    /// value found.
+    pub fn doc_value(&self) -> Option<&str> {
+        self.attrs.doc_value()
+    }
+    /// Finds all `doc` attributes as NameValues and returns their corresponding values, joined
+    /// with newlines.
+    pub fn collapsed_doc_value(&self) -> Option<String> {
+        self.attrs.collapsed_doc_value()
+    }
+
+    pub fn links(&self) -> Vec<(String, String)> {
+        self.attrs.links(&self.def_id.krate)
+    }
+
+    pub fn is_crate(&self) -> bool {
+        match self.inner {
+            StrippedItem(box ModuleItem(Module { is_crate: true, ..})) |
+            ModuleItem(Module { is_crate: true, ..}) => true,
+            _ => false,
+        }
+    }
+    pub fn is_mod(&self) -> bool {
+        self.type_() == ItemType::Module
+    }
+    pub fn is_trait(&self) -> bool {
+        self.type_() == ItemType::Trait
+    }
+    pub fn is_struct(&self) -> bool {
+        self.type_() == ItemType::Struct
+    }
+    pub fn is_enum(&self) -> bool {
+        self.type_() == ItemType::Enum
+    }
+    pub fn is_variant(&self) -> bool {
+        self.type_() == ItemType::Variant
+    }
+    pub fn is_associated_type(&self) -> bool {
+        self.type_() == ItemType::AssocType
+    }
+    pub fn is_associated_const(&self) -> bool {
+        self.type_() == ItemType::AssocConst
+    }
+    pub fn is_method(&self) -> bool {
+        self.type_() == ItemType::Method
+    }
+    pub fn is_ty_method(&self) -> bool {
+        self.type_() == ItemType::TyMethod
+    }
+    pub fn is_typedef(&self) -> bool {
+        self.type_() == ItemType::Typedef
+    }
+    pub fn is_primitive(&self) -> bool {
+        self.type_() == ItemType::Primitive
+    }
+    pub fn is_union(&self) -> bool {
+        self.type_() == ItemType::Union
+    }
+    pub fn is_import(&self) -> bool {
+        self.type_() == ItemType::Import
+    }
+    pub fn is_extern_crate(&self) -> bool {
+        self.type_() == ItemType::ExternCrate
+    }
+    pub fn is_keyword(&self) -> bool {
+        self.type_() == ItemType::Keyword
+    }
+
+    pub fn is_stripped(&self) -> bool {
+        match self.inner { StrippedItem(..) => true, _ => false }
+    }
+    pub fn has_stripped_fields(&self) -> Option<bool> {
+        match self.inner {
+            StructItem(ref _struct) => Some(_struct.fields_stripped),
+            UnionItem(ref union) => Some(union.fields_stripped),
+            VariantItem(Variant { kind: VariantKind::Struct(ref vstruct)} ) => {
+                Some(vstruct.fields_stripped)
+            },
+            _ => None,
+        }
+    }
+
+    pub fn stability_class(&self) -> Option<String> {
+        self.stability.as_ref().and_then(|ref s| {
+            let mut classes = Vec::with_capacity(2);
+
+            if s.level == stability::Unstable {
+                classes.push("unstable");
+            }
+
+            if s.deprecation.is_some() {
+                classes.push("deprecated");
+            }
+
+            if classes.len() != 0 {
+                Some(classes.join(" "))
+            } else {
+                None
+            }
+        })
+    }
+
+    pub fn stable_since(&self) -> Option<&str> {
+        self.stability.as_ref().map(|s| &s.since[..])
+    }
+
+    pub fn is_non_exhaustive(&self) -> bool {
+        self.attrs.other_attrs.iter()
+            .any(|a| a.check_name(sym::non_exhaustive))
+    }
+
+    /// Returns a documentation-level item type from the item.
+    pub fn type_(&self) -> ItemType {
+        ItemType::from(self)
+    }
+
+    /// Returns the info in the item's `#[deprecated]` or `#[rustc_deprecated]` attributes.
+    ///
+    /// If the item is not deprecated, returns `None`.
+    pub fn deprecation(&self) -> Option<&Deprecation> {
+        self.deprecation
+            .as_ref()
+            .or_else(|| self.stability.as_ref().and_then(|s| s.deprecation.as_ref()))
+    }
+    pub fn is_default(&self) -> bool {
+        match self.inner {
+            ItemEnum::MethodItem(ref meth) => {
+                if let Some(defaultness) = meth.defaultness {
+                    defaultness.has_value() && !defaultness.is_final()
+                } else {
+                    false
+                }
+            }
+            _ => false,
+        }
+    }
+}
+
+#[derive(Clone, Debug)]
+pub enum ItemEnum {
+    ExternCrateItem(String, Option<String>),
+    ImportItem(Import),
+    StructItem(Struct),
+    UnionItem(Union),
+    EnumItem(Enum),
+    FunctionItem(Function),
+    ModuleItem(Module),
+    TypedefItem(Typedef, bool /* is associated type */),
+    OpaqueTyItem(OpaqueTy, bool /* is associated type */),
+    StaticItem(Static),
+    ConstantItem(Constant),
+    TraitItem(Trait),
+    TraitAliasItem(TraitAlias),
+    ImplItem(Impl),
+    /// A method signature only. Used for required methods in traits (ie,
+    /// non-default-methods).
+    TyMethodItem(TyMethod),
+    /// A method with a body.
+    MethodItem(Method),
+    StructFieldItem(Type),
+    VariantItem(Variant),
+    /// `fn`s from an extern block
+    ForeignFunctionItem(Function),
+    /// `static`s from an extern block
+    ForeignStaticItem(Static),
+    /// `type`s from an extern block
+    ForeignTypeItem,
+    MacroItem(Macro),
+    ProcMacroItem(ProcMacro),
+    PrimitiveItem(PrimitiveType),
+    AssocConstItem(Type, Option<String>),
+    AssocTypeItem(Vec<GenericBound>, Option<Type>),
+    /// An item that has been stripped by a rustdoc pass
+    StrippedItem(Box<ItemEnum>),
+    KeywordItem(String),
+}
+
+impl ItemEnum {
+    pub fn is_associated(&self) -> bool {
+        match *self {
+            ItemEnum::TypedefItem(_, _) |
+            ItemEnum::AssocTypeItem(_, _) => true,
+            _ => false,
+        }
+    }
+}
+
+#[derive(Clone, Debug)]
+pub struct Module {
+    pub items: Vec<Item>,
+    pub is_crate: bool,
+}
+
+impl Clean<Item> for doctree::Module<'_> {
+    fn clean(&self, cx: &DocContext<'_>) -> Item {
+        let name = if self.name.is_some() {
+            self.name.expect("No name provided").clean(cx)
+        } else {
+            String::new()
+        };
+
+        // maintain a stack of mod ids, for doc comment path resolution
+        // but we also need to resolve the module's own docs based on whether its docs were written
+        // inside or outside the module, so check for that
+        let attrs = self.attrs.clean(cx);
+
+        let mut items: Vec<Item> = vec![];
+        items.extend(self.extern_crates.iter().flat_map(|x| x.clean(cx)));
+        items.extend(self.imports.iter().flat_map(|x| x.clean(cx)));
+        items.extend(self.structs.iter().map(|x| x.clean(cx)));
+        items.extend(self.unions.iter().map(|x| x.clean(cx)));
+        items.extend(self.enums.iter().map(|x| x.clean(cx)));
+        items.extend(self.fns.iter().map(|x| x.clean(cx)));
+        items.extend(self.foreigns.iter().map(|x| x.clean(cx)));
+        items.extend(self.mods.iter().map(|x| x.clean(cx)));
+        items.extend(self.typedefs.iter().map(|x| x.clean(cx)));
+        items.extend(self.opaque_tys.iter().map(|x| x.clean(cx)));
+        items.extend(self.statics.iter().map(|x| x.clean(cx)));
+        items.extend(self.constants.iter().map(|x| x.clean(cx)));
+        items.extend(self.traits.iter().map(|x| x.clean(cx)));
+        items.extend(self.impls.iter().flat_map(|x| x.clean(cx)));
+        items.extend(self.macros.iter().map(|x| x.clean(cx)));
+        items.extend(self.proc_macros.iter().map(|x| x.clean(cx)));
+        items.extend(self.trait_aliases.iter().map(|x| x.clean(cx)));
+
+        // determine if we should display the inner contents or
+        // the outer `mod` item for the source code.
+        let whence = {
+            let cm = cx.sess().source_map();
+            let outer = cm.lookup_char_pos(self.where_outer.lo());
+            let inner = cm.lookup_char_pos(self.where_inner.lo());
+            if outer.file.start_pos == inner.file.start_pos {
+                // mod foo { ... }
+                self.where_outer
+            } else {
+                // mod foo; (and a separate SourceFile for the contents)
+                self.where_inner
+            }
+        };
+
+        Item {
+            name: Some(name),
+            attrs,
+            source: whence.clean(cx),
+            visibility: self.vis.clean(cx),
+            stability: cx.stability(self.id).clean(cx),
+            deprecation: cx.deprecation(self.id).clean(cx),
+            def_id: cx.tcx.hir().local_def_id(self.id),
+            inner: ModuleItem(Module {
+               is_crate: self.is_crate,
+               items,
+            })
+        }
+    }
+}
+
+pub struct ListAttributesIter<'a> {
+    attrs: slice::Iter<'a, ast::Attribute>,
+    current_list: vec::IntoIter<ast::NestedMetaItem>,
+    name: Symbol,
+}
+
+impl<'a> Iterator for ListAttributesIter<'a> {
+    type Item = ast::NestedMetaItem;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if let Some(nested) = self.current_list.next() {
+            return Some(nested);
+        }
+
+        for attr in &mut self.attrs {
+            if let Some(list) = attr.meta_item_list() {
+                if attr.check_name(self.name) {
+                    self.current_list = list.into_iter();
+                    if let Some(nested) = self.current_list.next() {
+                        return Some(nested);
+                    }
+                }
+            }
+        }
+
+        None
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        let lower = self.current_list.len();
+        (lower, None)
+    }
+}
+
+pub trait AttributesExt {
+    /// Finds an attribute as List and returns the list of attributes nested inside.
+    fn lists(&self, name: Symbol) -> ListAttributesIter<'_>;
+}
+
+impl AttributesExt for [ast::Attribute] {
+    fn lists(&self, name: Symbol) -> ListAttributesIter<'_> {
+        ListAttributesIter {
+            attrs: self.iter(),
+            current_list: Vec::new().into_iter(),
+            name,
+        }
+    }
+}
+
+pub trait NestedAttributesExt {
+    /// Returns `true` if the attribute list contains a specific `Word`
+    fn has_word(self, word: Symbol) -> bool;
+}
+
+impl<I: IntoIterator<Item=ast::NestedMetaItem>> NestedAttributesExt for I {
+    fn has_word(self, word: Symbol) -> bool {
+        self.into_iter().any(|attr| attr.is_word() && attr.check_name(word))
+    }
+}
+
+/// A portion of documentation, extracted from a `#[doc]` attribute.
+///
+/// Each variant contains the line number within the complete doc-comment where the fragment
+/// starts, as well as the Span where the corresponding doc comment or attribute is located.
+///
+/// Included files are kept separate from inline doc comments so that proper line-number
+/// information can be given when a doctest fails. Sugared doc comments and "raw" doc comments are
+/// kept separate because of issue #42760.
+#[derive(Clone, PartialEq, Eq, Debug, Hash)]
+pub enum DocFragment {
+    /// A doc fragment created from a `///` or `//!` doc comment.
+    SugaredDoc(usize, syntax_pos::Span, String),
+    /// A doc fragment created from a "raw" `#[doc=""]` attribute.
+    RawDoc(usize, syntax_pos::Span, String),
+    /// A doc fragment created from a `#[doc(include="filename")]` attribute. Contains both the
+    /// given filename and the file contents.
+    Include(usize, syntax_pos::Span, String, String),
+}
+
+impl DocFragment {
+    pub fn as_str(&self) -> &str {
+        match *self {
+            DocFragment::SugaredDoc(_, _, ref s) => &s[..],
+            DocFragment::RawDoc(_, _, ref s) => &s[..],
+            DocFragment::Include(_, _, _, ref s) => &s[..],
+        }
+    }
+
+    pub fn span(&self) -> syntax_pos::Span {
+        match *self {
+            DocFragment::SugaredDoc(_, span, _) |
+                DocFragment::RawDoc(_, span, _) |
+                DocFragment::Include(_, span, _, _) => span,
+        }
+    }
+}
+
+impl<'a> FromIterator<&'a DocFragment> for String {
+    fn from_iter<T>(iter: T) -> Self
+    where
+        T: IntoIterator<Item = &'a DocFragment>
+    {
+        iter.into_iter().fold(String::new(), |mut acc, frag| {
+            if !acc.is_empty() {
+                acc.push('\n');
+            }
+            match *frag {
+                DocFragment::SugaredDoc(_, _, ref docs)
+                    | DocFragment::RawDoc(_, _, ref docs)
+                    | DocFragment::Include(_, _, _, ref docs) =>
+                    acc.push_str(docs),
+            }
+
+            acc
+        })
+    }
+}
+
+#[derive(Clone, Debug, Default)]
+pub struct Attributes {
+    pub doc_strings: Vec<DocFragment>,
+    pub other_attrs: Vec<ast::Attribute>,
+    pub cfg: Option<Arc<Cfg>>,
+    pub span: Option<syntax_pos::Span>,
+    /// map from Rust paths to resolved defs and potential URL fragments
+    pub links: Vec<(String, Option<DefId>, Option<String>)>,
+    pub inner_docs: bool,
+}
+
+impl Attributes {
+    /// Extracts the content from an attribute `#[doc(cfg(content))]`.
+    fn extract_cfg(mi: &ast::MetaItem) -> Option<&ast::MetaItem> {
+        use syntax::ast::NestedMetaItem::MetaItem;
+
+        if let ast::MetaItemKind::List(ref nmis) = mi.kind {
+            if nmis.len() == 1 {
+                if let MetaItem(ref cfg_mi) = nmis[0] {
+                    if cfg_mi.check_name(sym::cfg) {
+                        if let ast::MetaItemKind::List(ref cfg_nmis) = cfg_mi.kind {
+                            if cfg_nmis.len() == 1 {
+                                if let MetaItem(ref content_mi) = cfg_nmis[0] {
+                                    return Some(content_mi);
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        }
+
+        None
+    }
+
+    /// Reads a `MetaItem` from within an attribute, looks for whether it is a
+    /// `#[doc(include="file")]`, and returns the filename and contents of the file as loaded from
+    /// its expansion.
+    fn extract_include(mi: &ast::MetaItem)
+        -> Option<(String, String)>
+    {
+        mi.meta_item_list().and_then(|list| {
+            for meta in list {
+                if meta.check_name(sym::include) {
+                    // the actual compiled `#[doc(include="filename")]` gets expanded to
+                    // `#[doc(include(file="filename", contents="file contents")]` so we need to
+                    // look for that instead
+                    return meta.meta_item_list().and_then(|list| {
+                        let mut filename: Option<String> = None;
+                        let mut contents: Option<String> = None;
+
+                        for it in list {
+                            if it.check_name(sym::file) {
+                                if let Some(name) = it.value_str() {
+                                    filename = Some(name.to_string());
+                                }
+                            } else if it.check_name(sym::contents) {
+                                if let Some(docs) = it.value_str() {
+                                    contents = Some(docs.to_string());
+                                }
+                            }
+                        }
+
+                        if let (Some(filename), Some(contents)) = (filename, contents) {
+                            Some((filename, contents))
+                        } else {
+                            None
+                        }
+                    });
+                }
+            }
+
+            None
+        })
+    }
+
+    pub fn has_doc_flag(&self, flag: Symbol) -> bool {
+        for attr in &self.other_attrs {
+            if !attr.check_name(sym::doc) { continue; }
+
+            if let Some(items) = attr.meta_item_list() {
+                if items.iter().filter_map(|i| i.meta_item()).any(|it| it.check_name(flag)) {
+                    return true;
+                }
+            }
+        }
+
+        false
+    }
+
+    pub fn from_ast(diagnostic: &::errors::Handler,
+                    attrs: &[ast::Attribute]) -> Attributes {
+        let mut doc_strings = vec![];
+        let mut sp = None;
+        let mut cfg = Cfg::True;
+        let mut doc_line = 0;
+
+        /// If `attr` is a doc comment, strips the leading and (if present)
+        /// trailing comments symbols, e.g. `///`, `/**`, and `*/`. Otherwise,
+        /// returns `attr` unchanged.
+        pub fn with_doc_comment_markers_stripped<T>(
+            attr: &Attribute,
+            f: impl FnOnce(&Attribute) -> T
+        ) -> T {
+            match attr.kind {
+                AttrKind::Normal(_) => {
+                    f(attr)
+                }
+                AttrKind::DocComment(comment) => {
+                    let comment =
+                        Symbol::intern(&comments::strip_doc_comment_decoration(&comment.as_str()));
+                    f(&Attribute {
+                        kind: AttrKind::DocComment(comment),
+                        id: attr.id,
+                        style: attr.style,
+                        span: attr.span,
+                    })
+                }
+            }
+        }
+
+        let other_attrs = attrs.iter().filter_map(|attr| {
+            with_doc_comment_markers_stripped(attr, |attr| {
+                if attr.check_name(sym::doc) {
+                    if let Some(mi) = attr.meta() {
+                        if let Some(value) = mi.value_str() {
+                            // Extracted #[doc = "..."]
+                            let value = value.to_string();
+                            let line = doc_line;
+                            doc_line += value.lines().count();
+
+                            if attr.is_doc_comment() {
+                                doc_strings.push(DocFragment::SugaredDoc(line, attr.span, value));
+                            } else {
+                                doc_strings.push(DocFragment::RawDoc(line, attr.span, value));
+                            }
+
+                            if sp.is_none() {
+                                sp = Some(attr.span);
+                            }
+                            return None;
+                        } else if let Some(cfg_mi) = Attributes::extract_cfg(&mi) {
+                            // Extracted #[doc(cfg(...))]
+                            match Cfg::parse(cfg_mi) {
+                                Ok(new_cfg) => cfg &= new_cfg,
+                                Err(e) => diagnostic.span_err(e.span, e.msg),
+                            }
+                            return None;
+                        } else if let Some((filename, contents)) = Attributes::extract_include(&mi)
+                        {
+                            let line = doc_line;
+                            doc_line += contents.lines().count();
+                            doc_strings.push(DocFragment::Include(line,
+                                                                  attr.span,
+                                                                  filename,
+                                                                  contents));
+                        }
+                    }
+                }
+                Some(attr.clone())
+            })
+        }).collect();
+
+        // treat #[target_feature(enable = "feat")] attributes as if they were
+        // #[doc(cfg(target_feature = "feat"))] attributes as well
+        for attr in attrs.lists(sym::target_feature) {
+            if attr.check_name(sym::enable) {
+                if let Some(feat) = attr.value_str() {
+                    let meta = attr::mk_name_value_item_str(
+                        Ident::with_dummy_span(sym::target_feature), feat, DUMMY_SP
+                    );
+                    if let Ok(feat_cfg) = Cfg::parse(&meta) {
+                        cfg &= feat_cfg;
+                    }
+                }
+            }
+        }
+
+        let inner_docs = attrs.iter()
+                              .filter(|a| a.check_name(sym::doc))
+                              .next()
+                              .map_or(true, |a| a.style == AttrStyle::Inner);
+
+        Attributes {
+            doc_strings,
+            other_attrs,
+            cfg: if cfg == Cfg::True { None } else { Some(Arc::new(cfg)) },
+            span: sp,
+            links: vec![],
+            inner_docs,
+        }
+    }
+
+    /// Finds the `doc` attribute as a NameValue and returns the corresponding
+    /// value found.
+    pub fn doc_value(&self) -> Option<&str> {
+        self.doc_strings.first().map(|s| s.as_str())
+    }
+
+    /// Finds all `doc` attributes as NameValues and returns their corresponding values, joined
+    /// with newlines.
+    pub fn collapsed_doc_value(&self) -> Option<String> {
+        if !self.doc_strings.is_empty() {
+            Some(self.doc_strings.iter().collect())
+        } else {
+            None
+        }
+    }
+
+    /// Gets links as a vector
+    ///
+    /// Cache must be populated before call
+    pub fn links(&self, krate: &CrateNum) -> Vec<(String, String)> {
+        use crate::html::format::href;
+
+        self.links.iter().filter_map(|&(ref s, did, ref fragment)| {
+            match did {
+                Some(did) => {
+                    if let Some((mut href, ..)) = href(did) {
+                        if let Some(ref fragment) = *fragment {
+                            href.push_str("#");
+                            href.push_str(fragment);
+                        }
+                        Some((s.clone(), href))
+                    } else {
+                        None
+                    }
+                }
+                None => {
+                    if let Some(ref fragment) = *fragment {
+                        let cache = cache();
+                        let url = match cache.extern_locations.get(krate) {
+                            Some(&(_, ref src, ExternalLocation::Local)) =>
+                                src.to_str().expect("invalid file path"),
+                            Some(&(_, _, ExternalLocation::Remote(ref s))) => s,
+                            Some(&(_, _, ExternalLocation::Unknown)) | None =>
+                                "https://doc.rust-lang.org/nightly",
+                        };
+                        // This is a primitive so the url is done "by hand".
+                        let tail = fragment.find('#').unwrap_or_else(|| fragment.len());
+                        Some((s.clone(),
+                              format!("{}{}std/primitive.{}.html{}",
+                                      url,
+                                      if !url.ends_with('/') { "/" } else { "" },
+                                      &fragment[..tail],
+                                      &fragment[tail..])))
+                    } else {
+                        panic!("This isn't a primitive?!");
+                    }
+                }
+            }
+        }).collect()
+    }
+}
+
+impl PartialEq for Attributes {
+    fn eq(&self, rhs: &Self) -> bool {
+        self.doc_strings == rhs.doc_strings &&
+        self.cfg == rhs.cfg &&
+        self.span == rhs.span &&
+        self.links == rhs.links &&
+        self.other_attrs.iter().map(|attr| attr.id).eq(rhs.other_attrs.iter().map(|attr| attr.id))
+    }
+}
+
+impl Eq for Attributes {}
+
+impl Hash for Attributes {
+    fn hash<H: Hasher>(&self, hasher: &mut H) {
+        self.doc_strings.hash(hasher);
+        self.cfg.hash(hasher);
+        self.span.hash(hasher);
+        self.links.hash(hasher);
+        for attr in &self.other_attrs {
+            attr.id.hash(hasher);
+        }
+    }
+}
+
+impl AttributesExt for Attributes {
+    fn lists(&self, name: Symbol) -> ListAttributesIter<'_> {
+        self.other_attrs.lists(name)
+    }
+}
+
+impl Clean<Attributes> for [ast::Attribute] {
+    fn clean(&self, cx: &DocContext<'_>) -> Attributes {
+        Attributes::from_ast(cx.sess().diagnostic(), self)
+    }
+}
+
+#[derive(Clone, PartialEq, Eq, Debug, Hash)]
+pub enum GenericBound {
+    TraitBound(PolyTrait, hir::TraitBoundModifier),
+    Outlives(Lifetime),
+}
+
+impl GenericBound {
+    fn maybe_sized(cx: &DocContext<'_>) -> GenericBound {
+        let did = cx.tcx.require_lang_item(lang_items::SizedTraitLangItem, None);
+        let empty = cx.tcx.intern_substs(&[]);
+        let path = external_path(cx, cx.tcx.item_name(did),
+            Some(did), false, vec![], empty);
+        inline::record_extern_fqn(cx, did, TypeKind::Trait);
+        GenericBound::TraitBound(PolyTrait {
+            trait_: ResolvedPath {
+                path,
+                param_names: None,
+                did,
+                is_generic: false,
+            },
+            generic_params: Vec::new(),
+        }, hir::TraitBoundModifier::Maybe)
+    }
+
+    fn is_sized_bound(&self, cx: &DocContext<'_>) -> bool {
+        use rustc::hir::TraitBoundModifier as TBM;
+        if let GenericBound::TraitBound(PolyTrait { ref trait_, .. }, TBM::None) = *self {
+            if trait_.def_id() == cx.tcx.lang_items().sized_trait() {
+                return true;
+            }
+        }
+        false
+    }
+
+    fn get_poly_trait(&self) -> Option<PolyTrait> {
+        if let GenericBound::TraitBound(ref p, _) = *self {
+            return Some(p.clone())
+        }
+        None
+    }
+
+    fn get_trait_type(&self) -> Option<Type> {
+        if let GenericBound::TraitBound(PolyTrait { ref trait_, .. }, _) = *self {
+            Some(trait_.clone())
+        } else {
+            None
+        }
+    }
+}
+
+impl Clean<GenericBound> for hir::GenericBound {
+    fn clean(&self, cx: &DocContext<'_>) -> GenericBound {
+        match *self {
+            hir::GenericBound::Outlives(lt) => GenericBound::Outlives(lt.clean(cx)),
+            hir::GenericBound::Trait(ref t, modifier) => {
+                GenericBound::TraitBound(t.clean(cx), modifier)
+            }
+        }
+    }
+}
+
+fn external_generic_args(
+    cx: &DocContext<'_>,
+    trait_did: Option<DefId>,
+    has_self: bool,
+    bindings: Vec<TypeBinding>,
+    substs: SubstsRef<'_>,
+) -> GenericArgs {
+    let mut skip_self = has_self;
+    let mut ty_kind = None;
+    let args: Vec<_> = substs.iter().filter_map(|kind| match kind.unpack() {
+        GenericArgKind::Lifetime(lt) => {
+            lt.clean(cx).and_then(|lt| Some(GenericArg::Lifetime(lt)))
+        }
+        GenericArgKind::Type(_) if skip_self => {
+            skip_self = false;
+            None
+        }
+        GenericArgKind::Type(ty) => {
+            ty_kind = Some(&ty.kind);
+            Some(GenericArg::Type(ty.clean(cx)))
+        }
+        GenericArgKind::Const(ct) => Some(GenericArg::Const(ct.clean(cx))),
+    }).collect();
+
+    match trait_did {
+        // Attempt to sugar an external path like Fn<(A, B,), C> to Fn(A, B) -> C
+        Some(did) if cx.tcx.lang_items().fn_trait_kind(did).is_some() => {
+            assert!(ty_kind.is_some());
+            let inputs = match ty_kind {
+                Some(ty::Tuple(ref tys)) => tys.iter().map(|t| t.expect_ty().clean(cx)).collect(),
+                _ => return GenericArgs::AngleBracketed { args, bindings },
+            };
+            let output = None;
+            // FIXME(#20299) return type comes from a projection now
+            // match types[1].kind {
+            //     ty::Tuple(ref v) if v.is_empty() => None, // -> ()
+            //     _ => Some(types[1].clean(cx))
+            // };
+            GenericArgs::Parenthesized { inputs, output }
+        },
+        _ => {
+            GenericArgs::AngleBracketed { args, bindings }
+        }
+    }
+}
+
+// trait_did should be set to a trait's DefId if called on a TraitRef, in order to sugar
+// from Fn<(A, B,), C> to Fn(A, B) -> C
+fn external_path(cx: &DocContext<'_>, name: Symbol, trait_did: Option<DefId>, has_self: bool,
+                 bindings: Vec<TypeBinding>, substs: SubstsRef<'_>) -> Path {
+    Path {
+        global: false,
+        res: Res::Err,
+        segments: vec![PathSegment {
+            name: name.to_string(),
+            args: external_generic_args(cx, trait_did, has_self, bindings, substs)
+        }],
+    }
+}
+
+impl<'a, 'tcx> Clean<GenericBound> for (&'a ty::TraitRef<'tcx>, Vec<TypeBinding>) {
+    fn clean(&self, cx: &DocContext<'_>) -> GenericBound {
+        let (trait_ref, ref bounds) = *self;
+        inline::record_extern_fqn(cx, trait_ref.def_id, TypeKind::Trait);
+        let path = external_path(cx, cx.tcx.item_name(trait_ref.def_id),
+                                 Some(trait_ref.def_id), true, bounds.clone(), trait_ref.substs);
+
+        debug!("ty::TraitRef\n  subst: {:?}\n", trait_ref.substs);
+
+        // collect any late bound regions
+        let mut late_bounds = vec![];
+        for ty_s in trait_ref.input_types().skip(1) {
+            if let ty::Tuple(ts) = ty_s.kind {
+                for &ty_s in ts {
+                    if let ty::Ref(ref reg, _, _) = ty_s.expect_ty().kind {
+                        if let &ty::RegionKind::ReLateBound(..) = *reg {
+                            debug!("  hit an ReLateBound {:?}", reg);
+                            if let Some(Lifetime(name)) = reg.clean(cx) {
+                                late_bounds.push(GenericParamDef {
+                                    name,
+                                    kind: GenericParamDefKind::Lifetime,
+                                });
+                            }
+                        }
+                    }
+                }
+            }
+        }
+
+        GenericBound::TraitBound(
+            PolyTrait {
+                trait_: ResolvedPath {
+                    path,
+                    param_names: None,
+                    did: trait_ref.def_id,
+                    is_generic: false,
+                },
+                generic_params: late_bounds,
+            },
+            hir::TraitBoundModifier::None
+        )
+    }
+}
+
+impl<'tcx> Clean<GenericBound> for ty::TraitRef<'tcx> {
+    fn clean(&self, cx: &DocContext<'_>) -> GenericBound {
+        (self, vec![]).clean(cx)
+    }
+}
+
+impl<'tcx> Clean<Option<Vec<GenericBound>>> for InternalSubsts<'tcx> {
+    fn clean(&self, cx: &DocContext<'_>) -> Option<Vec<GenericBound>> {
+        let mut v = Vec::new();
+        v.extend(self.regions().filter_map(|r| r.clean(cx)).map(GenericBound::Outlives));
+        v.extend(self.types().map(|t| GenericBound::TraitBound(PolyTrait {
+            trait_: t.clean(cx),
+            generic_params: Vec::new(),
+        }, hir::TraitBoundModifier::None)));
+        if !v.is_empty() {Some(v)} else {None}
+    }
+}
+
+#[derive(Clone, PartialEq, Eq, Debug, Hash)]
+pub struct Lifetime(String);
+
+impl Lifetime {
+    pub fn get_ref<'a>(&'a self) -> &'a str {
+        let Lifetime(ref s) = *self;
+        let s: &'a str = s;
+        s
+    }
+
+    pub fn statik() -> Lifetime {
+        Lifetime("'static".to_string())
+    }
+}
+
+impl Clean<Lifetime> for hir::Lifetime {
+    fn clean(&self, cx: &DocContext<'_>) -> Lifetime {
+        if self.hir_id != hir::DUMMY_HIR_ID {
+            let def = cx.tcx.named_region(self.hir_id);
+            match def {
+                Some(rl::Region::EarlyBound(_, node_id, _)) |
+                Some(rl::Region::LateBound(_, node_id, _)) |
+                Some(rl::Region::Free(_, node_id)) => {
+                    if let Some(lt) = cx.lt_substs.borrow().get(&node_id).cloned() {
+                        return lt;
+                    }
+                }
+                _ => {}
+            }
+        }
+        Lifetime(self.name.ident().to_string())
+    }
+}
+
+impl Clean<Lifetime> for hir::GenericParam {
+    fn clean(&self, _: &DocContext<'_>) -> Lifetime {
+        match self.kind {
+            hir::GenericParamKind::Lifetime { .. } => {
+                if self.bounds.len() > 0 {
+                    let mut bounds = self.bounds.iter().map(|bound| match bound {
+                        hir::GenericBound::Outlives(lt) => lt,
+                        _ => panic!(),
+                    });
+                    let name = bounds.next().expect("no more bounds").name.ident();
+                    let mut s = format!("{}: {}", self.name.ident(), name);
+                    for bound in bounds {
+                        s.push_str(&format!(" + {}", bound.name.ident()));
+                    }
+                    Lifetime(s)
+                } else {
+                    Lifetime(self.name.ident().to_string())
+                }
+            }
+            _ => panic!(),
+        }
+    }
+}
+
+impl Clean<Constant> for hir::ConstArg {
+    fn clean(&self, cx: &DocContext<'_>) -> Constant {
+        Constant {
+            type_: cx.tcx.type_of(cx.tcx.hir().body_owner_def_id(self.value.body)).clean(cx),
+            expr: print_const_expr(cx, self.value.body),
+        }
+    }
+}
+
+impl Clean<Lifetime> for ty::GenericParamDef {
+    fn clean(&self, _cx: &DocContext<'_>) -> Lifetime {
+        Lifetime(self.name.to_string())
+    }
+}
+
+impl Clean<Option<Lifetime>> for ty::RegionKind {
+    fn clean(&self, cx: &DocContext<'_>) -> Option<Lifetime> {
+        match *self {
+            ty::ReStatic => Some(Lifetime::statik()),
+            ty::ReLateBound(_, ty::BrNamed(_, name)) => Some(Lifetime(name.to_string())),
+            ty::ReEarlyBound(ref data) => Some(Lifetime(data.name.clean(cx))),
+
+            ty::ReLateBound(..) |
+            ty::ReFree(..) |
+            ty::ReScope(..) |
+            ty::ReVar(..) |
+            ty::RePlaceholder(..) |
+            ty::ReEmpty |
+            ty::ReClosureBound(_) |
+            ty::ReErased => {
+                debug!("cannot clean region {:?}", self);
+                None
+            }
+        }
+    }
+}
+
+#[derive(Clone, Debug)]
+pub enum WherePredicate {
+    BoundPredicate { ty: Type, bounds: Vec<GenericBound> },
+    RegionPredicate { lifetime: Lifetime, bounds: Vec<GenericBound> },
+    EqPredicate { lhs: Type, rhs: Type },
+}
+
+impl WherePredicate {
+    pub fn get_bounds(&self) -> Option<&[GenericBound]> {
+        match *self {
+            WherePredicate::BoundPredicate { ref bounds, .. } => Some(bounds),
+            WherePredicate::RegionPredicate { ref bounds, .. } => Some(bounds),
+            _ => None,
+        }
+    }
+}
+
+impl Clean<WherePredicate> for hir::WherePredicate {
+    fn clean(&self, cx: &DocContext<'_>) -> WherePredicate {
+        match *self {
+            hir::WherePredicate::BoundPredicate(ref wbp) => {
+                WherePredicate::BoundPredicate {
+                    ty: wbp.bounded_ty.clean(cx),
+                    bounds: wbp.bounds.clean(cx)
+                }
+            }
+
+            hir::WherePredicate::RegionPredicate(ref wrp) => {
+                WherePredicate::RegionPredicate {
+                    lifetime: wrp.lifetime.clean(cx),
+                    bounds: wrp.bounds.clean(cx)
+                }
+            }
+
+            hir::WherePredicate::EqPredicate(ref wrp) => {
+                WherePredicate::EqPredicate {
+                    lhs: wrp.lhs_ty.clean(cx),
+                    rhs: wrp.rhs_ty.clean(cx)
+                }
+            }
+        }
+    }
+}
+
+impl<'a> Clean<Option<WherePredicate>> for ty::Predicate<'a> {
+    fn clean(&self, cx: &DocContext<'_>) -> Option<WherePredicate> {
+        use rustc::ty::Predicate;
+
+        match *self {
+            Predicate::Trait(ref pred) => Some(pred.clean(cx)),
+            Predicate::Subtype(ref pred) => Some(pred.clean(cx)),
+            Predicate::RegionOutlives(ref pred) => pred.clean(cx),
+            Predicate::TypeOutlives(ref pred) => pred.clean(cx),
+            Predicate::Projection(ref pred) => Some(pred.clean(cx)),
+
+            Predicate::WellFormed(..) |
+            Predicate::ObjectSafe(..) |
+            Predicate::ClosureKind(..) |
+            Predicate::ConstEvaluatable(..) => panic!("not user writable"),
+        }
+    }
+}
+
+impl<'a> Clean<WherePredicate> for ty::TraitPredicate<'a> {
+    fn clean(&self, cx: &DocContext<'_>) -> WherePredicate {
+        WherePredicate::BoundPredicate {
+            ty: self.trait_ref.self_ty().clean(cx),
+            bounds: vec![self.trait_ref.clean(cx)]
+        }
+    }
+}
+
+impl<'tcx> Clean<WherePredicate> for ty::SubtypePredicate<'tcx> {
+    fn clean(&self, _cx: &DocContext<'_>) -> WherePredicate {
+        panic!("subtype predicates are an internal rustc artifact \
+                and should not be seen by rustdoc")
+    }
+}
+
+impl<'tcx> Clean<Option<WherePredicate>> for
+    ty::OutlivesPredicate<ty::Region<'tcx>,ty::Region<'tcx>> {
+
+    fn clean(&self, cx: &DocContext<'_>) -> Option<WherePredicate> {
+        let ty::OutlivesPredicate(ref a, ref b) = *self;
+
+        match (a, b) {
+            (ty::ReEmpty, ty::ReEmpty) => {
+                return None;
+            },
+            _ => {}
+        }
+
+        Some(WherePredicate::RegionPredicate {
+            lifetime: a.clean(cx).expect("failed to clean lifetime"),
+            bounds: vec![GenericBound::Outlives(b.clean(cx).expect("failed to clean bounds"))]
+        })
+    }
+}
+
+impl<'tcx> Clean<Option<WherePredicate>> for ty::OutlivesPredicate<Ty<'tcx>, ty::Region<'tcx>> {
+    fn clean(&self, cx: &DocContext<'_>) -> Option<WherePredicate> {
+        let ty::OutlivesPredicate(ref ty, ref lt) = *self;
+
+        match lt {
+            ty::ReEmpty => return None,
+            _ => {}
+        }
+
+        Some(WherePredicate::BoundPredicate {
+            ty: ty.clean(cx),
+            bounds: vec![GenericBound::Outlives(lt.clean(cx).expect("failed to clean lifetimes"))]
+        })
+    }
+}
+
+impl<'tcx> Clean<WherePredicate> for ty::ProjectionPredicate<'tcx> {
+    fn clean(&self, cx: &DocContext<'_>) -> WherePredicate {
+        WherePredicate::EqPredicate {
+            lhs: self.projection_ty.clean(cx),
+            rhs: self.ty.clean(cx)
+        }
+    }
+}
+
+impl<'tcx> Clean<Type> for ty::ProjectionTy<'tcx> {
+    fn clean(&self, cx: &DocContext<'_>) -> Type {
+        let trait_ = match self.trait_ref(cx.tcx).clean(cx) {
+            GenericBound::TraitBound(t, _) => t.trait_,
+            GenericBound::Outlives(_) => panic!("cleaning a trait got a lifetime"),
+        };
+        Type::QPath {
+            name: cx.tcx.associated_item(self.item_def_id).ident.name.clean(cx),
+            self_type: box self.self_ty().clean(cx),
+            trait_: box trait_
+        }
+    }
+}
+
+#[derive(Clone, PartialEq, Eq, Debug, Hash)]
+pub enum GenericParamDefKind {
+    Lifetime,
+    Type {
+        did: DefId,
+        bounds: Vec<GenericBound>,
+        default: Option<Type>,
+        synthetic: Option<hir::SyntheticTyParamKind>,
+    },
+    Const {
+        did: DefId,
+        ty: Type,
+    },
+}
+
+impl GenericParamDefKind {
+    pub fn is_type(&self) -> bool {
+        match *self {
+            GenericParamDefKind::Type { .. } => true,
+            _ => false,
+        }
+    }
+
+    // FIXME(eddyb) this either returns the default of a type parameter, or the
+    // type of a `const` parameter. It seems that the intention is to *visit*
+    // any embedded types, but `get_type` seems to be the wrong name for that.
+    pub fn get_type(&self) -> Option<Type> {
+        match self {
+            GenericParamDefKind::Type { default, .. } => default.clone(),
+            GenericParamDefKind::Const { ty, .. } => Some(ty.clone()),
+            GenericParamDefKind::Lifetime => None,
+        }
+    }
+}
+
+#[derive(Clone, PartialEq, Eq, Debug, Hash)]
+pub struct GenericParamDef {
+    pub name: String,
+
+    pub kind: GenericParamDefKind,
+}
+
+impl GenericParamDef {
+    pub fn is_synthetic_type_param(&self) -> bool {
+        match self.kind {
+            GenericParamDefKind::Lifetime |
+            GenericParamDefKind::Const { .. } => false,
+            GenericParamDefKind::Type { ref synthetic, .. } => synthetic.is_some(),
+        }
+    }
+
+    pub fn is_type(&self) -> bool {
+        self.kind.is_type()
+    }
+
+    pub fn get_type(&self) -> Option<Type> {
+        self.kind.get_type()
+    }
+
+    pub fn get_bounds(&self) -> Option<&[GenericBound]> {
+        match self.kind {
+            GenericParamDefKind::Type { ref bounds, .. } => Some(bounds),
+            _ => None,
+        }
+    }
+}
+
+impl Clean<GenericParamDef> for ty::GenericParamDef {
+    fn clean(&self, cx: &DocContext<'_>) -> GenericParamDef {
+        let (name, kind) = match self.kind {
+            ty::GenericParamDefKind::Lifetime => {
+                (self.name.to_string(), GenericParamDefKind::Lifetime)
+            }
+            ty::GenericParamDefKind::Type { has_default, synthetic, .. } => {
+                let default = if has_default {
+                    Some(cx.tcx.type_of(self.def_id).clean(cx))
+                } else {
+                    None
+                };
+                (self.name.clean(cx), GenericParamDefKind::Type {
+                    did: self.def_id,
+                    bounds: vec![], // These are filled in from the where-clauses.
+                    default,
+                    synthetic,
+                })
+            }
+            ty::GenericParamDefKind::Const { .. } => {
+                (self.name.clean(cx), GenericParamDefKind::Const {
+                    did: self.def_id,
+                    ty: cx.tcx.type_of(self.def_id).clean(cx),
+                })
+            }
+        };
+
+        GenericParamDef {
+            name,
+            kind,
+        }
+    }
+}
+
+impl Clean<GenericParamDef> for hir::GenericParam {
+    fn clean(&self, cx: &DocContext<'_>) -> GenericParamDef {
+        let (name, kind) = match self.kind {
+            hir::GenericParamKind::Lifetime { .. } => {
+                let name = if self.bounds.len() > 0 {
+                    let mut bounds = self.bounds.iter().map(|bound| match bound {
+                        hir::GenericBound::Outlives(lt) => lt,
+                        _ => panic!(),
+                    });
+                    let name = bounds.next().expect("no more bounds").name.ident();
+                    let mut s = format!("{}: {}", self.name.ident(), name);
+                    for bound in bounds {
+                        s.push_str(&format!(" + {}", bound.name.ident()));
+                    }
+                    s
+                } else {
+                    self.name.ident().to_string()
+                };
+                (name, GenericParamDefKind::Lifetime)
+            }
+            hir::GenericParamKind::Type { ref default, synthetic } => {
+                (self.name.ident().name.clean(cx), GenericParamDefKind::Type {
+                    did: cx.tcx.hir().local_def_id(self.hir_id),
+                    bounds: self.bounds.clean(cx),
+                    default: default.clean(cx),
+                    synthetic,
+                })
+            }
+            hir::GenericParamKind::Const { ref ty } => {
+                (self.name.ident().name.clean(cx), GenericParamDefKind::Const {
+                    did: cx.tcx.hir().local_def_id(self.hir_id),
+                    ty: ty.clean(cx),
+                })
+            }
+        };
+
+        GenericParamDef {
+            name,
+            kind,
+        }
+    }
+}
+
+// maybe use a Generic enum and use Vec<Generic>?
+#[derive(Clone, Debug, Default)]
+pub struct Generics {
+    pub params: Vec<GenericParamDef>,
+    pub where_predicates: Vec<WherePredicate>,
+}
+
+impl Clean<Generics> for hir::Generics {
+    fn clean(&self, cx: &DocContext<'_>) -> Generics {
+        // Synthetic type-parameters are inserted after normal ones.
+        // In order for normal parameters to be able to refer to synthetic ones,
+        // scans them first.
+        fn is_impl_trait(param: &hir::GenericParam) -> bool {
+            match param.kind {
+                hir::GenericParamKind::Type { synthetic, .. } => {
+                    synthetic == Some(hir::SyntheticTyParamKind::ImplTrait)
+                }
+                _ => false,
+            }
+        }
+        let impl_trait_params = self.params
+            .iter()
+            .filter(|param| is_impl_trait(param))
+            .map(|param| {
+                let param: GenericParamDef = param.clean(cx);
+                match param.kind {
+                    GenericParamDefKind::Lifetime => unreachable!(),
+                    GenericParamDefKind::Type { did, ref bounds, .. } => {
+                        cx.impl_trait_bounds.borrow_mut().insert(did.into(), bounds.clone());
+                    }
+                    GenericParamDefKind::Const { .. } => unreachable!(),
+                }
+                param
+            })
+            .collect::<Vec<_>>();
+
+        let mut params = Vec::with_capacity(self.params.len());
+        for p in self.params.iter().filter(|p| !is_impl_trait(p)) {
+            let p = p.clean(cx);
+            params.push(p);
+        }
+        params.extend(impl_trait_params);
+
+        let mut generics = Generics {
+            params,
+            where_predicates: self.where_clause.predicates.clean(cx),
+        };
+
+        // Some duplicates are generated for ?Sized bounds between type params and where
+        // predicates. The point in here is to move the bounds definitions from type params
+        // to where predicates when such cases occur.
+        for where_pred in &mut generics.where_predicates {
+            match *where_pred {
+                WherePredicate::BoundPredicate { ty: Generic(ref name), ref mut bounds } => {
+                    if bounds.is_empty() {
+                        for param in &mut generics.params {
+                            match param.kind {
+                                GenericParamDefKind::Lifetime => {}
+                                GenericParamDefKind::Type { bounds: ref mut ty_bounds, .. } => {
+                                    if &param.name == name {
+                                        mem::swap(bounds, ty_bounds);
+                                        break
+                                    }
+                                }
+                                GenericParamDefKind::Const { .. } => {}
+                            }
+                        }
+                    }
+                }
+                _ => continue,
+            }
+        }
+        generics
+    }
+}
+
+impl<'a, 'tcx> Clean<Generics> for (&'a ty::Generics, ty::GenericPredicates<'tcx>) {
+    fn clean(&self, cx: &DocContext<'_>) -> Generics {
+        use self::WherePredicate as WP;
+        use std::collections::BTreeMap;
+
+        let (gens, preds) = *self;
+
+        // Don't populate `cx.impl_trait_bounds` before `clean`ning `where` clauses,
+        // since `Clean for ty::Predicate` would consume them.
+        let mut impl_trait = BTreeMap::<ImplTraitParam, Vec<GenericBound>>::default();
+
+        // Bounds in the type_params and lifetimes fields are repeated in the
+        // predicates field (see rustc_typeck::collect::ty_generics), so remove
+        // them.
+        let stripped_typarams = gens.params.iter()
+            .filter_map(|param| match param.kind {
+                ty::GenericParamDefKind::Lifetime => None,
+                ty::GenericParamDefKind::Type { synthetic, .. } => {
+                    if param.name == kw::SelfUpper {
+                        assert_eq!(param.index, 0);
+                        return None;
+                    }
+                    if synthetic == Some(hir::SyntheticTyParamKind::ImplTrait) {
+                        impl_trait.insert(param.index.into(), vec![]);
+                        return None;
+                    }
+                    Some(param.clean(cx))
+                }
+                ty::GenericParamDefKind::Const { .. } => None,
+            }).collect::<Vec<GenericParamDef>>();
+
+        // param index -> [(DefId of trait, associated type name, type)]
+        let mut impl_trait_proj =
+            FxHashMap::<u32, Vec<(DefId, String, Ty<'tcx>)>>::default();
+
+        let where_predicates = preds.predicates.iter()
+            .flat_map(|(p, _)| {
+                let mut projection = None;
+                let param_idx = (|| {
+                    if let Some(trait_ref) = p.to_opt_poly_trait_ref() {
+                        if let ty::Param(param) = trait_ref.self_ty().kind {
+                            return Some(param.index);
+                        }
+                    } else if let Some(outlives) = p.to_opt_type_outlives() {
+                        if let ty::Param(param) = outlives.skip_binder().0.kind {
+                            return Some(param.index);
+                        }
+                    } else if let ty::Predicate::Projection(p) = p {
+                        if let ty::Param(param) = p.skip_binder().projection_ty.self_ty().kind {
+                            projection = Some(p);
+                            return Some(param.index);
+                        }
+                    }
+
+                    None
+                })();
+
+                if let Some(param_idx) = param_idx {
+                    if let Some(b) = impl_trait.get_mut(&param_idx.into()) {
+                        let p = p.clean(cx)?;
+
+                        b.extend(
+                            p.get_bounds()
+                                .into_iter()
+                                .flatten()
+                                .cloned()
+                                .filter(|b| !b.is_sized_bound(cx))
+                        );
+
+                        let proj = projection
+                            .map(|p| (p.skip_binder().projection_ty.clean(cx), p.skip_binder().ty));
+                        if let Some(((_, trait_did, name), rhs)) =
+                            proj.as_ref().and_then(|(lhs, rhs)| Some((lhs.projection()?, rhs)))
+                        {
+                            impl_trait_proj
+                                .entry(param_idx)
+                                .or_default()
+                                .push((trait_did, name.to_string(), rhs));
+                        }
+
+                        return None;
+                    }
+                }
+
+                Some(p)
+            })
+            .collect::<Vec<_>>();
+
+        for (param, mut bounds) in impl_trait {
+            // Move trait bounds to the front.
+            bounds.sort_by_key(|b| if let GenericBound::TraitBound(..) = b {
+                false
+            } else {
+                true
+            });
+
+            if let crate::core::ImplTraitParam::ParamIndex(idx) = param {
+                if let Some(proj) = impl_trait_proj.remove(&idx) {
+                    for (trait_did, name, rhs) in proj {
+                        simplify::merge_bounds(
+                            cx,
+                            &mut bounds,
+                            trait_did,
+                            &name,
+                            &rhs.clean(cx),
+                        );
+                    }
+                }
+            } else {
+                unreachable!();
+            }
+
+            cx.impl_trait_bounds.borrow_mut().insert(param, bounds);
+        }
+
+        // Now that `cx.impl_trait_bounds` is populated, we can process
+        // remaining predicates which could contain `impl Trait`.
+        let mut where_predicates = where_predicates
+            .into_iter()
+            .flat_map(|p| p.clean(cx))
+            .collect::<Vec<_>>();
+
+        // Type parameters and have a Sized bound by default unless removed with
+        // ?Sized. Scan through the predicates and mark any type parameter with
+        // a Sized bound, removing the bounds as we find them.
+        //
+        // Note that associated types also have a sized bound by default, but we
+        // don't actually know the set of associated types right here so that's
+        // handled in cleaning associated types
+        let mut sized_params = FxHashSet::default();
+        where_predicates.retain(|pred| {
+            match *pred {
+                WP::BoundPredicate { ty: Generic(ref g), ref bounds } => {
+                    if bounds.iter().any(|b| b.is_sized_bound(cx)) {
+                        sized_params.insert(g.clone());
+                        false
+                    } else {
+                        true
+                    }
+                }
+                _ => true,
+            }
+        });
+
+        // Run through the type parameters again and insert a ?Sized
+        // unbound for any we didn't find to be Sized.
+        for tp in &stripped_typarams {
+            if !sized_params.contains(&tp.name) {
+                where_predicates.push(WP::BoundPredicate {
+                    ty: Type::Generic(tp.name.clone()),
+                    bounds: vec![GenericBound::maybe_sized(cx)],
+                })
+            }
+        }
+
+        // It would be nice to collect all of the bounds on a type and recombine
+        // them if possible, to avoid e.g., `where T: Foo, T: Bar, T: Sized, T: 'a`
+        // and instead see `where T: Foo + Bar + Sized + 'a`
+
+        Generics {
+            params: gens.params
+                        .iter()
+                        .flat_map(|param| match param.kind {
+                            ty::GenericParamDefKind::Lifetime => Some(param.clean(cx)),
+                            ty::GenericParamDefKind::Type { .. } => None,
+                            ty::GenericParamDefKind::Const { .. } => Some(param.clean(cx)),
+                        }).chain(simplify::ty_params(stripped_typarams).into_iter())
+                        .collect(),
+            where_predicates: simplify::where_clauses(cx, where_predicates),
+        }
+    }
+}
+
+/// The point of this function is to replace bounds with types.
+///
+/// i.e. `[T, U]` when you have the following bounds: `T: Display, U: Option<T>` will return
+/// `[Display, Option]` (we just returns the list of the types, we don't care about the
+/// wrapped types in here).
+fn get_real_types(
+    generics: &Generics,
+    arg: &Type,
+    cx: &DocContext<'_>,
+    recurse: i32,
+) -> FxHashSet<Type> {
+    let arg_s = arg.print().to_string();
+    let mut res = FxHashSet::default();
+    if recurse >= 10 { // FIXME: remove this whole recurse thing when the recursion bug is fixed
+        return res;
+    }
+    if arg.is_full_generic() {
+        if let Some(where_pred) = generics.where_predicates.iter().find(|g| {
+            match g {
+                &WherePredicate::BoundPredicate { ref ty, .. } => ty.def_id() == arg.def_id(),
+                _ => false,
+            }
+        }) {
+            let bounds = where_pred.get_bounds().unwrap_or_else(|| &[]);
+            for bound in bounds.iter() {
+                match *bound {
+                    GenericBound::TraitBound(ref poly_trait, _) => {
+                        for x in poly_trait.generic_params.iter() {
+                            if !x.is_type() {
+                                continue
+                            }
+                            if let Some(ty) = x.get_type() {
+                                let adds = get_real_types(generics, &ty, cx, recurse + 1);
+                                if !adds.is_empty() {
+                                    res.extend(adds);
+                                } else if !ty.is_full_generic() {
+                                    res.insert(ty);
+                                }
+                            }
+                        }
+                    }
+                    _ => {}
+                }
+            }
+        }
+        if let Some(bound) = generics.params.iter().find(|g| {
+            g.is_type() && g.name == arg_s
+        }) {
+            for bound in bound.get_bounds().unwrap_or_else(|| &[]) {
+                if let Some(ty) = bound.get_trait_type() {
+                    let adds = get_real_types(generics, &ty, cx, recurse + 1);
+                    if !adds.is_empty() {
+                        res.extend(adds);
+                    } else if !ty.is_full_generic() {
+                        res.insert(ty.clone());
+                    }
+                }
+            }
+        }
+    } else {
+        res.insert(arg.clone());
+        if let Some(gens) = arg.generics() {
+            for gen in gens.iter() {
+                if gen.is_full_generic() {
+                    let adds = get_real_types(generics, gen, cx, recurse + 1);
+                    if !adds.is_empty() {
+                        res.extend(adds);
+                    }
+                } else {
+                    res.insert(gen.clone());
+                }
+            }
+        }
+    }
+    res
+}
+
+/// Return the full list of types when bounds have been resolved.
+///
+/// i.e. `fn foo<A: Display, B: Option<A>>(x: u32, y: B)` will return
+/// `[u32, Display, Option]`.
+pub fn get_all_types(
+    generics: &Generics,
+    decl: &FnDecl,
+    cx: &DocContext<'_>,
+) -> (Vec<Type>, Vec<Type>) {
+    let mut all_types = FxHashSet::default();
+    for arg in decl.inputs.values.iter() {
+        if arg.type_.is_self_type() {
+            continue;
+        }
+        let args = get_real_types(generics, &arg.type_, cx, 0);
+        if !args.is_empty() {
+            all_types.extend(args);
+        } else {
+            all_types.insert(arg.type_.clone());
+        }
+    }
+
+    let ret_types = match decl.output {
+        FunctionRetTy::Return(ref return_type) => {
+            let mut ret = get_real_types(generics, &return_type, cx, 0);
+            if ret.is_empty() {
+                ret.insert(return_type.clone());
+            }
+            ret.into_iter().collect()
+        }
+        _ => Vec::new(),
+    };
+    (all_types.into_iter().collect(), ret_types)
+}
+
+#[derive(Clone, Debug)]
+pub struct Method {
+    pub generics: Generics,
+    pub decl: FnDecl,
+    pub header: hir::FnHeader,
+    pub defaultness: Option<hir::Defaultness>,
+    pub all_types: Vec<Type>,
+    pub ret_types: Vec<Type>,
+}
+
+impl<'a> Clean<Method> for (&'a hir::FnSig, &'a hir::Generics, hir::BodyId,
+                            Option<hir::Defaultness>) {
+    fn clean(&self, cx: &DocContext<'_>) -> Method {
+        let (generics, decl) = enter_impl_trait(cx, || {
+            (self.1.clean(cx), (&*self.0.decl, self.2).clean(cx))
+        });
+        let (all_types, ret_types) = get_all_types(&generics, &decl, cx);
+        Method {
+            decl,
+            generics,
+            header: self.0.header,
+            defaultness: self.3,
+            all_types,
+            ret_types,
+        }
+    }
+}
+
+#[derive(Clone, Debug)]
+pub struct TyMethod {
+    pub header: hir::FnHeader,
+    pub decl: FnDecl,
+    pub generics: Generics,
+    pub all_types: Vec<Type>,
+    pub ret_types: Vec<Type>,
+}
+
+#[derive(Clone, Debug)]
+pub struct Function {
+    pub decl: FnDecl,
+    pub generics: Generics,
+    pub header: hir::FnHeader,
+    pub all_types: Vec<Type>,
+    pub ret_types: Vec<Type>,
+}
+
+impl Clean<Item> for doctree::Function<'_> {
+    fn clean(&self, cx: &DocContext<'_>) -> Item {
+        let (generics, decl) = enter_impl_trait(cx, || {
+            (self.generics.clean(cx), (self.decl, self.body).clean(cx))
+        });
+
+        let did = cx.tcx.hir().local_def_id(self.id);
+        let constness = if cx.tcx.is_min_const_fn(did) {
+            hir::Constness::Const
+        } else {
+            hir::Constness::NotConst
+        };
+        let (all_types, ret_types) = get_all_types(&generics, &decl, cx);
+        Item {
+            name: Some(self.name.clean(cx)),
+            attrs: self.attrs.clean(cx),
+            source: self.whence.clean(cx),
+            visibility: self.vis.clean(cx),
+            stability: cx.stability(self.id).clean(cx),
+            deprecation: cx.deprecation(self.id).clean(cx),
+            def_id: did,
+            inner: FunctionItem(Function {
+                decl,
+                generics,
+                header: hir::FnHeader { constness, ..self.header },
+                all_types,
+                ret_types,
+            }),
+        }
+    }
+}
+
+#[derive(Clone, PartialEq, Eq, Debug, Hash)]
+pub struct FnDecl {
+    pub inputs: Arguments,
+    pub output: FunctionRetTy,
+    pub c_variadic: bool,
+    pub attrs: Attributes,
+}
+
+impl FnDecl {
+    pub fn self_type(&self) -> Option<SelfTy> {
+        self.inputs.values.get(0).and_then(|v| v.to_self())
+    }
+
+    /// Returns the sugared return type for an async function.
+    ///
+    /// For example, if the return type is `impl std::future::Future<Output = i32>`, this function
+    /// will return `i32`.
+    ///
+    /// # Panics
+    ///
+    /// This function will panic if the return type does not match the expected sugaring for async
+    /// functions.
+    pub fn sugared_async_return_type(&self) -> FunctionRetTy {
+        match &self.output {
+            FunctionRetTy::Return(Type::ImplTrait(bounds)) => {
+                match &bounds[0] {
+                    GenericBound::TraitBound(PolyTrait { trait_, .. }, ..) => {
+                        let bindings = trait_.bindings().unwrap();
+                        FunctionRetTy::Return(bindings[0].ty().clone())
+                    }
+                    _ => panic!("unexpected desugaring of async function"),
+                }
+            }
+            _ => panic!("unexpected desugaring of async function"),
+        }
+    }
+}
+
+#[derive(Clone, PartialEq, Eq, Debug, Hash)]
+pub struct Arguments {
+    pub values: Vec<Argument>,
+}
+
+impl<'a> Clean<Arguments> for (&'a [hir::Ty], &'a [ast::Ident]) {
+    fn clean(&self, cx: &DocContext<'_>) -> Arguments {
+        Arguments {
+            values: self.0.iter().enumerate().map(|(i, ty)| {
+                let mut name = self.1.get(i).map(|ident| ident.to_string())
+                                            .unwrap_or(String::new());
+                if name.is_empty() {
+                    name = "_".to_string();
+                }
+                Argument {
+                    name,
+                    type_: ty.clean(cx),
+                }
+            }).collect()
+        }
+    }
+}
+
+impl<'a> Clean<Arguments> for (&'a [hir::Ty], hir::BodyId) {
+    fn clean(&self, cx: &DocContext<'_>) -> Arguments {
+        let body = cx.tcx.hir().body(self.1);
+
+        Arguments {
+            values: self.0.iter().enumerate().map(|(i, ty)| {
+                Argument {
+                    name: name_from_pat(&body.params[i].pat),
+                    type_: ty.clean(cx),
+                }
+            }).collect()
+        }
+    }
+}
+
+impl<'a, A: Copy> Clean<FnDecl> for (&'a hir::FnDecl, A)
+    where (&'a [hir::Ty], A): Clean<Arguments>
+{
+    fn clean(&self, cx: &DocContext<'_>) -> FnDecl {
+        FnDecl {
+            inputs: (&self.0.inputs[..], self.1).clean(cx),
+            output: self.0.output.clean(cx),
+            c_variadic: self.0.c_variadic,
+            attrs: Attributes::default(),
+        }
+    }
+}
+
+impl<'tcx> Clean<FnDecl> for (DefId, ty::PolyFnSig<'tcx>) {
+    fn clean(&self, cx: &DocContext<'_>) -> FnDecl {
+        let (did, sig) = *self;
+        let mut names = if cx.tcx.hir().as_local_hir_id(did).is_some() {
+            vec![].into_iter()
+        } else {
+            cx.tcx.fn_arg_names(did).into_iter()
+        };
+
+        FnDecl {
+            output: Return(sig.skip_binder().output().clean(cx)),
+            attrs: Attributes::default(),
+            c_variadic: sig.skip_binder().c_variadic,
+            inputs: Arguments {
+                values: sig.skip_binder().inputs().iter().map(|t| {
+                    Argument {
+                        type_: t.clean(cx),
+                        name: names.next().map_or(String::new(), |name| name.to_string()),
+                    }
+                }).collect(),
+            },
+        }
+    }
+}
+
+#[derive(Clone, PartialEq, Eq, Debug, Hash)]
+pub struct Argument {
+    pub type_: Type,
+    pub name: String,
+}
+
+#[derive(Clone, PartialEq, Debug)]
+pub enum SelfTy {
+    SelfValue,
+    SelfBorrowed(Option<Lifetime>, Mutability),
+    SelfExplicit(Type),
+}
+
+impl Argument {
+    pub fn to_self(&self) -> Option<SelfTy> {
+        if self.name != "self" {
+            return None;
+        }
+        if self.type_.is_self_type() {
+            return Some(SelfValue);
+        }
+        match self.type_ {
+            BorrowedRef{ref lifetime, mutability, ref type_} if type_.is_self_type() => {
+                Some(SelfBorrowed(lifetime.clone(), mutability))
+            }
+            _ => Some(SelfExplicit(self.type_.clone()))
+        }
+    }
+}
+
+#[derive(Clone, PartialEq, Eq, Debug, Hash)]
+pub enum FunctionRetTy {
+    Return(Type),
+    DefaultReturn,
+}
+
+impl Clean<FunctionRetTy> for hir::FunctionRetTy {
+    fn clean(&self, cx: &DocContext<'_>) -> FunctionRetTy {
+        match *self {
+            hir::Return(ref typ) => Return(typ.clean(cx)),
+            hir::DefaultReturn(..) => DefaultReturn,
+        }
+    }
+}
+
+impl GetDefId for FunctionRetTy {
+    fn def_id(&self) -> Option<DefId> {
+        match *self {
+            Return(ref ty) => ty.def_id(),
+            DefaultReturn => None,
+        }
+    }
+}
+
+#[derive(Clone, Debug)]
+pub struct Trait {
+    pub auto: bool,
+    pub unsafety: hir::Unsafety,
+    pub items: Vec<Item>,
+    pub generics: Generics,
+    pub bounds: Vec<GenericBound>,
+    pub is_spotlight: bool,
+    pub is_auto: bool,
+}
+
+impl Clean<Item> for doctree::Trait<'_> {
+    fn clean(&self, cx: &DocContext<'_>) -> Item {
+        let attrs = self.attrs.clean(cx);
+        let is_spotlight = attrs.has_doc_flag(sym::spotlight);
+        Item {
+            name: Some(self.name.clean(cx)),
+            attrs,
+            source: self.whence.clean(cx),
+            def_id: cx.tcx.hir().local_def_id(self.id),
+            visibility: self.vis.clean(cx),
+            stability: cx.stability(self.id).clean(cx),
+            deprecation: cx.deprecation(self.id).clean(cx),
+            inner: TraitItem(Trait {
+                auto: self.is_auto.clean(cx),
+                unsafety: self.unsafety,
+                items: self.items.iter().map(|ti| ti.clean(cx)).collect(),
+                generics: self.generics.clean(cx),
+                bounds: self.bounds.clean(cx),
+                is_spotlight,
+                is_auto: self.is_auto.clean(cx),
+            }),
+        }
+    }
+}
+
+#[derive(Clone, Debug)]
+pub struct TraitAlias {
+    pub generics: Generics,
+    pub bounds: Vec<GenericBound>,
+}
+
+impl Clean<Item> for doctree::TraitAlias<'_> {
+    fn clean(&self, cx: &DocContext<'_>) -> Item {
+        let attrs = self.attrs.clean(cx);
+        Item {
+            name: Some(self.name.clean(cx)),
+            attrs,
+            source: self.whence.clean(cx),
+            def_id: cx.tcx.hir().local_def_id(self.id),
+            visibility: self.vis.clean(cx),
+            stability: cx.stability(self.id).clean(cx),
+            deprecation: cx.deprecation(self.id).clean(cx),
+            inner: TraitAliasItem(TraitAlias {
+                generics: self.generics.clean(cx),
+                bounds: self.bounds.clean(cx),
+            }),
+        }
+    }
+}
+
+impl Clean<bool> for hir::IsAuto {
+    fn clean(&self, _: &DocContext<'_>) -> bool {
+        match *self {
+            hir::IsAuto::Yes => true,
+            hir::IsAuto::No => false,
+        }
+    }
+}
+
+impl Clean<Type> for hir::TraitRef {
+    fn clean(&self, cx: &DocContext<'_>) -> Type {
+        resolve_type(cx, self.path.clean(cx), self.hir_ref_id)
+    }
+}
+
+impl Clean<PolyTrait> for hir::PolyTraitRef {
+    fn clean(&self, cx: &DocContext<'_>) -> PolyTrait {
+        PolyTrait {
+            trait_: self.trait_ref.clean(cx),
+            generic_params: self.bound_generic_params.clean(cx)
+        }
+    }
+}
+
+impl Clean<Item> for hir::TraitItem {
+    fn clean(&self, cx: &DocContext<'_>) -> Item {
+        let inner = match self.kind {
+            hir::TraitItemKind::Const(ref ty, default) => {
+                AssocConstItem(ty.clean(cx),
+                                    default.map(|e| print_const_expr(cx, e)))
+            }
+            hir::TraitItemKind::Method(ref sig, hir::TraitMethod::Provided(body)) => {
+                MethodItem((sig, &self.generics, body, None).clean(cx))
+            }
+            hir::TraitItemKind::Method(ref sig, hir::TraitMethod::Required(ref names)) => {
+                let (generics, decl) = enter_impl_trait(cx, || {
+                    (self.generics.clean(cx), (&*sig.decl, &names[..]).clean(cx))
+                });
+                let (all_types, ret_types) = get_all_types(&generics, &decl, cx);
+                TyMethodItem(TyMethod {
+                    header: sig.header,
+                    decl,
+                    generics,
+                    all_types,
+                    ret_types,
+                })
+            }
+            hir::TraitItemKind::Type(ref bounds, ref default) => {
+                AssocTypeItem(bounds.clean(cx), default.clean(cx))
+            }
+        };
+        let local_did = cx.tcx.hir().local_def_id(self.hir_id);
+        Item {
+            name: Some(self.ident.name.clean(cx)),
+            attrs: self.attrs.clean(cx),
+            source: self.span.clean(cx),
+            def_id: local_did,
+            visibility: Visibility::Inherited,
+            stability: get_stability(cx, local_did),
+            deprecation: get_deprecation(cx, local_did),
+            inner,
+        }
+    }
+}
+
+impl Clean<Item> for hir::ImplItem {
+    fn clean(&self, cx: &DocContext<'_>) -> Item {
+        let inner = match self.kind {
+            hir::ImplItemKind::Const(ref ty, expr) => {
+                AssocConstItem(ty.clean(cx),
+                                    Some(print_const_expr(cx, expr)))
+            }
+            hir::ImplItemKind::Method(ref sig, body) => {
+                MethodItem((sig, &self.generics, body, Some(self.defaultness)).clean(cx))
+            }
+            hir::ImplItemKind::TyAlias(ref ty) => TypedefItem(Typedef {
+                type_: ty.clean(cx),
+                generics: Generics::default(),
+            }, true),
+            hir::ImplItemKind::OpaqueTy(ref bounds) => OpaqueTyItem(OpaqueTy {
+                bounds: bounds.clean(cx),
+                generics: Generics::default(),
+            }, true),
+        };
+        let local_did = cx.tcx.hir().local_def_id(self.hir_id);
+        Item {
+            name: Some(self.ident.name.clean(cx)),
+            source: self.span.clean(cx),
+            attrs: self.attrs.clean(cx),
+            def_id: local_did,
+            visibility: self.vis.clean(cx),
+            stability: get_stability(cx, local_did),
+            deprecation: get_deprecation(cx, local_did),
+            inner,
+        }
+    }
+}
+
+impl Clean<Item> for ty::AssocItem {
+    fn clean(&self, cx: &DocContext<'_>) -> Item {
+        let inner = match self.kind {
+            ty::AssocKind::Const => {
+                let ty = cx.tcx.type_of(self.def_id);
+                let default = if self.defaultness.has_value() {
+                    Some(inline::print_inlined_const(cx, self.def_id))
+                } else {
+                    None
+                };
+                AssocConstItem(ty.clean(cx), default)
+            }
+            ty::AssocKind::Method => {
+                let generics = (cx.tcx.generics_of(self.def_id),
+                                cx.tcx.explicit_predicates_of(self.def_id)).clean(cx);
+                let sig = cx.tcx.fn_sig(self.def_id);
+                let mut decl = (self.def_id, sig).clean(cx);
+
+                if self.method_has_self_argument {
+                    let self_ty = match self.container {
+                        ty::ImplContainer(def_id) => {
+                            cx.tcx.type_of(def_id)
+                        }
+                        ty::TraitContainer(_) => cx.tcx.types.self_param,
+                    };
+                    let self_arg_ty = *sig.input(0).skip_binder();
+                    if self_arg_ty == self_ty {
+                        decl.inputs.values[0].type_ = Generic(String::from("Self"));
+                    } else if let ty::Ref(_, ty, _) = self_arg_ty.kind {
+                        if ty == self_ty {
+                            match decl.inputs.values[0].type_ {
+                                BorrowedRef{ref mut type_, ..} => {
+                                    **type_ = Generic(String::from("Self"))
+                                }
+                                _ => unreachable!(),
+                            }
+                        }
+                    }
+                }
+
+                let provided = match self.container {
+                    ty::ImplContainer(_) => true,
+                    ty::TraitContainer(_) => self.defaultness.has_value()
+                };
+                let (all_types, ret_types) = get_all_types(&generics, &decl, cx);
+                if provided {
+                    let constness = if cx.tcx.is_min_const_fn(self.def_id) {
+                        hir::Constness::Const
+                    } else {
+                        hir::Constness::NotConst
+                    };
+                    let asyncness = cx.tcx.asyncness(self.def_id);
+                    let defaultness = match self.container {
+                        ty::ImplContainer(_) => Some(self.defaultness),
+                        ty::TraitContainer(_) => None,
+                    };
+                    MethodItem(Method {
+                        generics,
+                        decl,
+                        header: hir::FnHeader {
+                            unsafety: sig.unsafety(),
+                            abi: sig.abi(),
+                            constness,
+                            asyncness,
+                        },
+                        defaultness,
+                        all_types,
+                        ret_types,
+                    })
+                } else {
+                    TyMethodItem(TyMethod {
+                        generics,
+                        decl,
+                        header: hir::FnHeader {
+                            unsafety: sig.unsafety(),
+                            abi: sig.abi(),
+                            constness: hir::Constness::NotConst,
+                            asyncness: hir::IsAsync::NotAsync,
+                        },
+                        all_types,
+                        ret_types,
+                    })
+                }
+            }
+            ty::AssocKind::Type => {
+                let my_name = self.ident.name.clean(cx);
+
+                if let ty::TraitContainer(did) = self.container {
+                    // When loading a cross-crate associated type, the bounds for this type
+                    // are actually located on the trait/impl itself, so we need to load
+                    // all of the generics from there and then look for bounds that are
+                    // applied to this associated type in question.
+                    let predicates = cx.tcx.explicit_predicates_of(did);
+                    let generics = (cx.tcx.generics_of(did), predicates).clean(cx);
+                    let mut bounds = generics.where_predicates.iter().filter_map(|pred| {
+                        let (name, self_type, trait_, bounds) = match *pred {
+                            WherePredicate::BoundPredicate {
+                                ty: QPath { ref name, ref self_type, ref trait_ },
+                                ref bounds
+                            } => (name, self_type, trait_, bounds),
+                            _ => return None,
+                        };
+                        if *name != my_name { return None }
+                        match **trait_ {
+                            ResolvedPath { did, .. } if did == self.container.id() => {}
+                            _ => return None,
+                        }
+                        match **self_type {
+                            Generic(ref s) if *s == "Self" => {}
+                            _ => return None,
+                        }
+                        Some(bounds)
+                    }).flat_map(|i| i.iter().cloned()).collect::<Vec<_>>();
+                    // Our Sized/?Sized bound didn't get handled when creating the generics
+                    // because we didn't actually get our whole set of bounds until just now
+                    // (some of them may have come from the trait). If we do have a sized
+                    // bound, we remove it, and if we don't then we add the `?Sized` bound
+                    // at the end.
+                    match bounds.iter().position(|b| b.is_sized_bound(cx)) {
+                        Some(i) => { bounds.remove(i); }
+                        None => bounds.push(GenericBound::maybe_sized(cx)),
+                    }
+
+                    let ty = if self.defaultness.has_value() {
+                        Some(cx.tcx.type_of(self.def_id))
+                    } else {
+                        None
+                    };
+
+                    AssocTypeItem(bounds, ty.clean(cx))
+                } else {
+                    TypedefItem(Typedef {
+                        type_: cx.tcx.type_of(self.def_id).clean(cx),
+                        generics: Generics {
+                            params: Vec::new(),
+                            where_predicates: Vec::new(),
+                        },
+                    }, true)
+                }
+            }
+            ty::AssocKind::OpaqueTy => unimplemented!(),
+        };
+
+        let visibility = match self.container {
+            ty::ImplContainer(_) => self.vis.clean(cx),
+            ty::TraitContainer(_) => Inherited,
+        };
+
+        Item {
+            name: Some(self.ident.name.clean(cx)),
+            visibility,
+            stability: get_stability(cx, self.def_id),
+            deprecation: get_deprecation(cx, self.def_id),
+            def_id: self.def_id,
+            attrs: inline::load_attrs(cx, self.def_id).clean(cx),
+            source: cx.tcx.def_span(self.def_id).clean(cx),
+            inner,
+        }
+    }
+}
+
+/// A trait reference, which may have higher ranked lifetimes.
+#[derive(Clone, PartialEq, Eq, Debug, Hash)]
+pub struct PolyTrait {
+    pub trait_: Type,
+    pub generic_params: Vec<GenericParamDef>,
+}
+
+/// A representation of a type suitable for hyperlinking purposes. Ideally, one can get the original
+/// type out of the AST/`TyCtxt` given one of these, if more information is needed. Most
+/// importantly, it does not preserve mutability or boxes.
+#[derive(Clone, PartialEq, Eq, Debug, Hash)]
+pub enum Type {
+    /// Structs/enums/traits (most that would be an `hir::TyKind::Path`).
+    ResolvedPath {
+        path: Path,
+        param_names: Option<Vec<GenericBound>>,
+        did: DefId,
+        /// `true` if is a `T::Name` path for associated types.
+        is_generic: bool,
+    },
+    /// For parameterized types, so the consumer of the JSON don't go
+    /// looking for types which don't exist anywhere.
+    Generic(String),
+    /// Primitives are the fixed-size numeric types (plus int/usize/float), char,
+    /// arrays, slices, and tuples.
+    Primitive(PrimitiveType),
+    /// `extern "ABI" fn`
+    BareFunction(Box<BareFunctionDecl>),
+    Tuple(Vec<Type>),
+    Slice(Box<Type>),
+    Array(Box<Type>, String),
+    Never,
+    RawPointer(Mutability, Box<Type>),
+    BorrowedRef {
+        lifetime: Option<Lifetime>,
+        mutability: Mutability,
+        type_: Box<Type>,
+    },
+
+    // `<Type as Trait>::Name`
+    QPath {
+        name: String,
+        self_type: Box<Type>,
+        trait_: Box<Type>
+    },
+
+    // `_`
+    Infer,
+
+    // `impl TraitA + TraitB + ...`
+    ImplTrait(Vec<GenericBound>),
+}
+
+#[derive(Clone, PartialEq, Eq, Hash, Copy, Debug)]
+pub enum PrimitiveType {
+    Isize, I8, I16, I32, I64, I128,
+    Usize, U8, U16, U32, U64, U128,
+    F32, F64,
+    Char,
+    Bool,
+    Str,
+    Slice,
+    Array,
+    Tuple,
+    Unit,
+    RawPointer,
+    Reference,
+    Fn,
+    Never,
+}
+
+#[derive(Clone, Copy, Debug)]
+pub enum TypeKind {
+    Enum,
+    Function,
+    Module,
+    Const,
+    Static,
+    Struct,
+    Union,
+    Trait,
+    Typedef,
+    Foreign,
+    Macro,
+    Attr,
+    Derive,
+    TraitAlias,
+}
+
+pub trait GetDefId {
+    fn def_id(&self) -> Option<DefId>;
+}
+
+impl<T: GetDefId> GetDefId for Option<T> {
+    fn def_id(&self) -> Option<DefId> {
+        self.as_ref().and_then(|d| d.def_id())
+    }
+}
+
+impl Type {
+    pub fn primitive_type(&self) -> Option<PrimitiveType> {
+        match *self {
+            Primitive(p) | BorrowedRef { type_: box Primitive(p), ..} => Some(p),
+            Slice(..) | BorrowedRef { type_: box Slice(..), .. } => Some(PrimitiveType::Slice),
+            Array(..) | BorrowedRef { type_: box Array(..), .. } => Some(PrimitiveType::Array),
+            Tuple(ref tys) => if tys.is_empty() {
+                Some(PrimitiveType::Unit)
+            } else {
+                Some(PrimitiveType::Tuple)
+            },
+            RawPointer(..) => Some(PrimitiveType::RawPointer),
+            BorrowedRef { type_: box Generic(..), .. } => Some(PrimitiveType::Reference),
+            BareFunction(..) => Some(PrimitiveType::Fn),
+            Never => Some(PrimitiveType::Never),
+            _ => None,
+        }
+    }
+
+    pub fn is_generic(&self) -> bool {
+        match *self {
+            ResolvedPath { is_generic, .. } => is_generic,
+            _ => false,
+        }
+    }
+
+    pub fn is_self_type(&self) -> bool {
+        match *self {
+            Generic(ref name) => name == "Self",
+            _ => false
+        }
+    }
+
+    pub fn generics(&self) -> Option<Vec<Type>> {
+        match *self {
+            ResolvedPath { ref path, .. } => {
+                path.segments.last().and_then(|seg| {
+                    if let GenericArgs::AngleBracketed { ref args, .. } = seg.args {
+                        Some(args.iter().filter_map(|arg| match arg {
+                            GenericArg::Type(ty) => Some(ty.clone()),
+                            _ => None,
+                        }).collect())
+                    } else {
+                        None
+                    }
+                })
+            }
+            _ => None,
+        }
+    }
+
+    pub fn bindings(&self) -> Option<&[TypeBinding]> {
+        match *self {
+            ResolvedPath { ref path, .. } => {
+                path.segments.last().and_then(|seg| {
+                    if let GenericArgs::AngleBracketed { ref bindings, .. } = seg.args {
+                        Some(&**bindings)
+                    } else {
+                        None
+                    }
+                })
+            }
+            _ => None
+        }
+    }
+
+    pub fn is_full_generic(&self) -> bool {
+        match *self {
+            Type::Generic(_) => true,
+            _ => false,
+        }
+    }
+
+    pub fn projection(&self) -> Option<(&Type, DefId, &str)> {
+        let (self_, trait_, name) = match self {
+            QPath { ref self_type, ref trait_, ref name } => {
+                (self_type, trait_, name)
+            }
+            _ => return None,
+        };
+        let trait_did = match **trait_ {
+            ResolvedPath { did, .. } => did,
+            _ => return None,
+        };
+        Some((&self_, trait_did, name))
+    }
+
+}
+
+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(),
+            BorrowedRef { type_: box Generic(..), .. } =>
+                Primitive(PrimitiveType::Reference).def_id(),
+            BorrowedRef { ref type_, .. } => type_.def_id(),
+            Tuple(ref tys) => if tys.is_empty() {
+                Primitive(PrimitiveType::Unit).def_id()
+            } else {
+                Primitive(PrimitiveType::Tuple).def_id()
+            },
+            BareFunction(..) => Primitive(PrimitiveType::Fn).def_id(),
+            Never => Primitive(PrimitiveType::Never).def_id(),
+            Slice(..) => Primitive(PrimitiveType::Slice).def_id(),
+            Array(..) => Primitive(PrimitiveType::Array).def_id(),
+            RawPointer(..) => Primitive(PrimitiveType::RawPointer).def_id(),
+            QPath { ref self_type, .. } => self_type.def_id(),
+            _ => None,
+        }
+    }
+}
+
+impl PrimitiveType {
+    fn from_str(s: &str) -> Option<PrimitiveType> {
+        match s {
+            "isize" => Some(PrimitiveType::Isize),
+            "i8" => Some(PrimitiveType::I8),
+            "i16" => Some(PrimitiveType::I16),
+            "i32" => Some(PrimitiveType::I32),
+            "i64" => Some(PrimitiveType::I64),
+            "i128" => Some(PrimitiveType::I128),
+            "usize" => Some(PrimitiveType::Usize),
+            "u8" => Some(PrimitiveType::U8),
+            "u16" => Some(PrimitiveType::U16),
+            "u32" => Some(PrimitiveType::U32),
+            "u64" => Some(PrimitiveType::U64),
+            "u128" => Some(PrimitiveType::U128),
+            "bool" => Some(PrimitiveType::Bool),
+            "char" => Some(PrimitiveType::Char),
+            "str" => Some(PrimitiveType::Str),
+            "f32" => Some(PrimitiveType::F32),
+            "f64" => Some(PrimitiveType::F64),
+            "array" => Some(PrimitiveType::Array),
+            "slice" => Some(PrimitiveType::Slice),
+            "tuple" => Some(PrimitiveType::Tuple),
+            "unit" => Some(PrimitiveType::Unit),
+            "pointer" => Some(PrimitiveType::RawPointer),
+            "reference" => Some(PrimitiveType::Reference),
+            "fn" => Some(PrimitiveType::Fn),
+            "never" => Some(PrimitiveType::Never),
+            _ => None,
+        }
+    }
+
+    pub fn as_str(&self) -> &'static str {
+        use self::PrimitiveType::*;
+        match *self {
+            Isize => "isize",
+            I8 => "i8",
+            I16 => "i16",
+            I32 => "i32",
+            I64 => "i64",
+            I128 => "i128",
+            Usize => "usize",
+            U8 => "u8",
+            U16 => "u16",
+            U32 => "u32",
+            U64 => "u64",
+            U128 => "u128",
+            F32 => "f32",
+            F64 => "f64",
+            Str => "str",
+            Bool => "bool",
+            Char => "char",
+            Array => "array",
+            Slice => "slice",
+            Tuple => "tuple",
+            Unit => "unit",
+            RawPointer => "pointer",
+            Reference => "reference",
+            Fn => "fn",
+            Never => "never",
+        }
+    }
+
+    pub fn to_url_str(&self) -> &'static str {
+        self.as_str()
+    }
+}
+
+impl From<ast::IntTy> for PrimitiveType {
+    fn from(int_ty: ast::IntTy) -> PrimitiveType {
+        match int_ty {
+            ast::IntTy::Isize => PrimitiveType::Isize,
+            ast::IntTy::I8 => PrimitiveType::I8,
+            ast::IntTy::I16 => PrimitiveType::I16,
+            ast::IntTy::I32 => PrimitiveType::I32,
+            ast::IntTy::I64 => PrimitiveType::I64,
+            ast::IntTy::I128 => PrimitiveType::I128,
+        }
+    }
+}
+
+impl From<ast::UintTy> for PrimitiveType {
+    fn from(uint_ty: ast::UintTy) -> PrimitiveType {
+        match uint_ty {
+            ast::UintTy::Usize => PrimitiveType::Usize,
+            ast::UintTy::U8 => PrimitiveType::U8,
+            ast::UintTy::U16 => PrimitiveType::U16,
+            ast::UintTy::U32 => PrimitiveType::U32,
+            ast::UintTy::U64 => PrimitiveType::U64,
+            ast::UintTy::U128 => PrimitiveType::U128,
+        }
+    }
+}
+
+impl From<ast::FloatTy> for PrimitiveType {
+    fn from(float_ty: ast::FloatTy) -> PrimitiveType {
+        match float_ty {
+            ast::FloatTy::F32 => PrimitiveType::F32,
+            ast::FloatTy::F64 => PrimitiveType::F64,
+        }
+    }
+}
+
+impl Clean<Type> for hir::Ty {
+    fn clean(&self, cx: &DocContext<'_>) -> Type {
+        use rustc::hir::*;
+
+        match self.kind {
+            TyKind::Never => Never,
+            TyKind::Ptr(ref m) => RawPointer(m.mutbl.clean(cx), box m.ty.clean(cx)),
+            TyKind::Rptr(ref l, ref m) => {
+                let lifetime = if l.is_elided() {
+                    None
+                } else {
+                    Some(l.clean(cx))
+                };
+                BorrowedRef {lifetime, mutability: m.mutbl.clean(cx),
+                             type_: box m.ty.clean(cx)}
+            }
+            TyKind::Slice(ref ty) => Slice(box ty.clean(cx)),
+            TyKind::Array(ref ty, ref length) => {
+                let def_id = cx.tcx.hir().local_def_id(length.hir_id);
+                let param_env = cx.tcx.param_env(def_id);
+                let substs = InternalSubsts::identity_for_item(cx.tcx, def_id);
+                let cid = GlobalId {
+                    instance: ty::Instance::new(def_id, substs),
+                    promoted: None
+                };
+                let length = match cx.tcx.const_eval(param_env.and(cid)) {
+                    Ok(length) => print_const(cx, length),
+                    Err(_) => cx.sess()
+                                .source_map()
+                                .span_to_snippet(cx.tcx.def_span(def_id))
+                                .unwrap_or_else(|_| "_".to_string()),
+                };
+                Array(box ty.clean(cx), length)
+            },
+            TyKind::Tup(ref tys) => Tuple(tys.clean(cx)),
+            TyKind::Def(item_id, _) => {
+                let item = cx.tcx.hir().expect_item(item_id.id);
+                if let hir::ItemKind::OpaqueTy(ref ty) = item.kind {
+                    ImplTrait(ty.bounds.clean(cx))
+                } else {
+                    unreachable!()
+                }
+            }
+            TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
+                if let Res::Def(DefKind::TyParam, did) = path.res {
+                    if let Some(new_ty) = cx.ty_substs.borrow().get(&did).cloned() {
+                        return new_ty;
+                    }
+                    if let Some(bounds) = cx.impl_trait_bounds.borrow_mut().remove(&did.into()) {
+                        return ImplTrait(bounds);
+                    }
+                }
+
+                let mut alias = None;
+                if let Res::Def(DefKind::TyAlias, def_id) = path.res {
+                    // Substitute private type aliases
+                    if let Some(hir_id) = cx.tcx.hir().as_local_hir_id(def_id) {
+                        if !cx.renderinfo.borrow().access_levels.is_exported(def_id) {
+                            alias = Some(&cx.tcx.hir().expect_item(hir_id).kind);
+                        }
+                    }
+                };
+
+                if let Some(&hir::ItemKind::TyAlias(ref ty, ref generics)) = alias {
+                    let provided_params = &path.segments.last().expect("segments were empty");
+                    let mut ty_substs = FxHashMap::default();
+                    let mut lt_substs = FxHashMap::default();
+                    let mut ct_substs = FxHashMap::default();
+                    let generic_args = provided_params.generic_args();
+                    {
+                        let mut indices: GenericParamCount = Default::default();
+                        for param in generics.params.iter() {
+                            match param.kind {
+                                hir::GenericParamKind::Lifetime { .. } => {
+                                    let mut j = 0;
+                                    let lifetime = generic_args.args.iter().find_map(|arg| {
+                                        match arg {
+                                            hir::GenericArg::Lifetime(lt) => {
+                                                if indices.lifetimes == j {
+                                                    return Some(lt);
+                                                }
+                                                j += 1;
+                                                None
+                                            }
+                                            _ => None,
+                                        }
+                                    });
+                                    if let Some(lt) = lifetime.cloned() {
+                                        if !lt.is_elided() {
+                                            let lt_def_id =
+                                                cx.tcx.hir().local_def_id(param.hir_id);
+                                            lt_substs.insert(lt_def_id, lt.clean(cx));
+                                        }
+                                    }
+                                    indices.lifetimes += 1;
+                                }
+                                hir::GenericParamKind::Type { ref default, .. } => {
+                                    let ty_param_def_id =
+                                        cx.tcx.hir().local_def_id(param.hir_id);
+                                    let mut j = 0;
+                                    let type_ = generic_args.args.iter().find_map(|arg| {
+                                        match arg {
+                                            hir::GenericArg::Type(ty) => {
+                                                if indices.types == j {
+                                                    return Some(ty);
+                                                }
+                                                j += 1;
+                                                None
+                                            }
+                                            _ => None,
+                                        }
+                                    });
+                                    if let Some(ty) = type_ {
+                                        ty_substs.insert(ty_param_def_id, ty.clean(cx));
+                                    } else if let Some(default) = default.clone() {
+                                        ty_substs.insert(ty_param_def_id,
+                                                         default.clean(cx));
+                                    }
+                                    indices.types += 1;
+                                }
+                                hir::GenericParamKind::Const { .. } => {
+                                    let const_param_def_id =
+                                        cx.tcx.hir().local_def_id(param.hir_id);
+                                    let mut j = 0;
+                                    let const_ = generic_args.args.iter().find_map(|arg| {
+                                        match arg {
+                                            hir::GenericArg::Const(ct) => {
+                                                if indices.consts == j {
+                                                    return Some(ct);
+                                                }
+                                                j += 1;
+                                                None
+                                            }
+                                            _ => None,
+                                        }
+                                    });
+                                    if let Some(ct) = const_ {
+                                        ct_substs.insert(const_param_def_id, ct.clean(cx));
+                                    }
+                                    // FIXME(const_generics:defaults)
+                                    indices.consts += 1;
+                                }
+                            }
+                        }
+                    }
+                    return cx.enter_alias(ty_substs, lt_substs, ct_substs, || ty.clean(cx));
+                }
+                resolve_type(cx, path.clean(cx), self.hir_id)
+            }
+            TyKind::Path(hir::QPath::Resolved(Some(ref qself), ref p)) => {
+                let segments = if p.is_global() { &p.segments[1..] } else { &p.segments };
+                let trait_segments = &segments[..segments.len() - 1];
+                let trait_path = self::Path {
+                    global: p.is_global(),
+                    res: Res::Def(
+                        DefKind::Trait,
+                        cx.tcx.associated_item(p.res.def_id()).container.id(),
+                    ),
+                    segments: trait_segments.clean(cx),
+                };
+                Type::QPath {
+                    name: p.segments.last().expect("segments were empty").ident.name.clean(cx),
+                    self_type: box qself.clean(cx),
+                    trait_: box resolve_type(cx, trait_path, self.hir_id)
+                }
+            }
+            TyKind::Path(hir::QPath::TypeRelative(ref qself, ref segment)) => {
+                let mut res = Res::Err;
+                let ty = hir_ty_to_ty(cx.tcx, self);
+                if let ty::Projection(proj) = ty.kind {
+                    res = Res::Def(DefKind::Trait, proj.trait_ref(cx.tcx).def_id);
+                }
+                let trait_path = hir::Path {
+                    span: self.span,
+                    res,
+                    segments: vec![].into(),
+                };
+                Type::QPath {
+                    name: segment.ident.name.clean(cx),
+                    self_type: box qself.clean(cx),
+                    trait_: box resolve_type(cx, trait_path.clean(cx), self.hir_id)
+                }
+            }
+            TyKind::TraitObject(ref bounds, ref lifetime) => {
+                match bounds[0].clean(cx).trait_ {
+                    ResolvedPath { path, param_names: None, did, is_generic } => {
+                        let mut bounds: Vec<self::GenericBound> = bounds[1..].iter().map(|bound| {
+                            self::GenericBound::TraitBound(bound.clean(cx),
+                                                           hir::TraitBoundModifier::None)
+                        }).collect();
+                        if !lifetime.is_elided() {
+                            bounds.push(self::GenericBound::Outlives(lifetime.clean(cx)));
+                        }
+                        ResolvedPath { path, param_names: Some(bounds), did, is_generic, }
+                    }
+                    _ => Infer, // shouldn't happen
+                }
+            }
+            TyKind::BareFn(ref barefn) => BareFunction(box barefn.clean(cx)),
+            TyKind::Infer | TyKind::Err => Infer,
+            TyKind::Typeof(..) => panic!("unimplemented type {:?}", self.kind),
+        }
+    }
+}
+
+impl<'tcx> Clean<Type> for Ty<'tcx> {
+    fn clean(&self, cx: &DocContext<'_>) -> Type {
+        debug!("cleaning type: {:?}", self);
+        match self.kind {
+            ty::Never => Never,
+            ty::Bool => Primitive(PrimitiveType::Bool),
+            ty::Char => Primitive(PrimitiveType::Char),
+            ty::Int(int_ty) => Primitive(int_ty.into()),
+            ty::Uint(uint_ty) => Primitive(uint_ty.into()),
+            ty::Float(float_ty) => Primitive(float_ty.into()),
+            ty::Str => Primitive(PrimitiveType::Str),
+            ty::Slice(ty) => Slice(box ty.clean(cx)),
+            ty::Array(ty, n) => {
+                let mut n = cx.tcx.lift(&n).expect("array lift failed");
+                if let ty::ConstKind::Unevaluated(def_id, substs) = n.val {
+                    let param_env = cx.tcx.param_env(def_id);
+                    let cid = GlobalId {
+                        instance: ty::Instance::new(def_id, substs),
+                        promoted: None
+                    };
+                    if let Ok(new_n) = cx.tcx.const_eval(param_env.and(cid)) {
+                        n = new_n;
+                    }
+                };
+                let n = print_const(cx, n);
+                Array(box ty.clean(cx), n)
+            }
+            ty::RawPtr(mt) => RawPointer(mt.mutbl.clean(cx), box mt.ty.clean(cx)),
+            ty::Ref(r, ty, mutbl) => BorrowedRef {
+                lifetime: r.clean(cx),
+                mutability: mutbl.clean(cx),
+                type_: box ty.clean(cx),
+            },
+            ty::FnDef(..) |
+            ty::FnPtr(_) => {
+                let ty = cx.tcx.lift(self).expect("FnPtr lift failed");
+                let sig = ty.fn_sig(cx.tcx);
+                let local_def_id = cx.tcx.hir().local_def_id_from_node_id(ast::CRATE_NODE_ID);
+                BareFunction(box BareFunctionDecl {
+                    unsafety: sig.unsafety(),
+                    generic_params: Vec::new(),
+                    decl: (local_def_id, sig).clean(cx),
+                    abi: sig.abi(),
+                })
+            }
+            ty::Adt(def, substs) => {
+                let did = def.did;
+                let kind = match def.adt_kind() {
+                    AdtKind::Struct => TypeKind::Struct,
+                    AdtKind::Union => TypeKind::Union,
+                    AdtKind::Enum => TypeKind::Enum,
+                };
+                inline::record_extern_fqn(cx, did, kind);
+                let path = external_path(cx, cx.tcx.item_name(did), None, false, vec![], substs);
+                ResolvedPath {
+                    path,
+                    param_names: None,
+                    did,
+                    is_generic: false,
+                }
+            }
+            ty::Foreign(did) => {
+                inline::record_extern_fqn(cx, did, TypeKind::Foreign);
+                let path = external_path(cx, cx.tcx.item_name(did),
+                                         None, false, vec![], InternalSubsts::empty());
+                ResolvedPath {
+                    path,
+                    param_names: None,
+                    did,
+                    is_generic: false,
+                }
+            }
+            ty::Dynamic(ref obj, ref reg) => {
+                // HACK: pick the first `did` as the `did` of the trait object. Someone
+                // might want to implement "native" support for marker-trait-only
+                // trait objects.
+                let mut dids = obj.principal_def_id().into_iter().chain(obj.auto_traits());
+                let did = dids.next().unwrap_or_else(|| {
+                    panic!("found trait object `{:?}` with no traits?", self)
+                });
+                let substs = match obj.principal() {
+                    Some(principal) => principal.skip_binder().substs,
+                    // marker traits have no substs.
+                    _ => cx.tcx.intern_substs(&[])
+                };
+
+                inline::record_extern_fqn(cx, did, TypeKind::Trait);
+
+                let mut param_names = vec![];
+                reg.clean(cx).map(|b| param_names.push(GenericBound::Outlives(b)));
+                for did in dids {
+                    let empty = cx.tcx.intern_substs(&[]);
+                    let path = external_path(cx, cx.tcx.item_name(did),
+                        Some(did), false, vec![], empty);
+                    inline::record_extern_fqn(cx, did, TypeKind::Trait);
+                    let bound = GenericBound::TraitBound(PolyTrait {
+                        trait_: ResolvedPath {
+                            path,
+                            param_names: None,
+                            did,
+                            is_generic: false,
+                        },
+                        generic_params: Vec::new(),
+                    }, hir::TraitBoundModifier::None);
+                    param_names.push(bound);
+                }
+
+                let mut bindings = vec![];
+                for pb in obj.projection_bounds() {
+                    bindings.push(TypeBinding {
+                        name: cx.tcx.associated_item(pb.item_def_id()).ident.name.clean(cx),
+                        kind: TypeBindingKind::Equality {
+                            ty: pb.skip_binder().ty.clean(cx)
+                        },
+                    });
+                }
+
+                let path = external_path(cx, cx.tcx.item_name(did), Some(did),
+                    false, bindings, substs);
+                ResolvedPath {
+                    path,
+                    param_names: Some(param_names),
+                    did,
+                    is_generic: false,
+                }
+            }
+            ty::Tuple(ref t) => {
+                Tuple(t.iter().map(|t| t.expect_ty()).collect::<Vec<_>>().clean(cx))
+            }
+
+            ty::Projection(ref data) => data.clean(cx),
+
+            ty::Param(ref p) => {
+                if let Some(bounds) = cx.impl_trait_bounds.borrow_mut().remove(&p.index.into()) {
+                    ImplTrait(bounds)
+                } else {
+                    Generic(p.name.to_string())
+                }
+            }
+
+            ty::Opaque(def_id, substs) => {
+                // Grab the "TraitA + TraitB" from `impl TraitA + TraitB`,
+                // by looking up the projections associated with the def_id.
+                let predicates_of = cx.tcx.explicit_predicates_of(def_id);
+                let substs = cx.tcx.lift(&substs).expect("Opaque lift failed");
+                let bounds = predicates_of.instantiate(cx.tcx, substs);
+                let mut regions = vec![];
+                let mut has_sized = false;
+                let mut bounds = bounds.predicates.iter().filter_map(|predicate| {
+                    let trait_ref = if let Some(tr) = predicate.to_opt_poly_trait_ref() {
+                        tr
+                    } else if let ty::Predicate::TypeOutlives(pred) = *predicate {
+                        // these should turn up at the end
+                        pred.skip_binder().1.clean(cx).map(|r| {
+                            regions.push(GenericBound::Outlives(r))
+                        });
+                        return None;
+                    } else {
+                        return None;
+                    };
+
+                    if let Some(sized) = cx.tcx.lang_items().sized_trait() {
+                        if trait_ref.def_id() == sized {
+                            has_sized = true;
+                            return None;
+                        }
+                    }
+
+                    let bounds = bounds.predicates.iter().filter_map(|pred|
+                        if let ty::Predicate::Projection(proj) = *pred {
+                            let proj = proj.skip_binder();
+                            if proj.projection_ty.trait_ref(cx.tcx) == *trait_ref.skip_binder() {
+                                Some(TypeBinding {
+                                    name: cx.tcx.associated_item(proj.projection_ty.item_def_id)
+                                                .ident.name.clean(cx),
+                                    kind: TypeBindingKind::Equality {
+                                        ty: proj.ty.clean(cx),
+                                    },
+                                })
+                            } else {
+                                None
+                            }
+                        } else {
+                            None
+                        }
+                    ).collect();
+
+                    Some((trait_ref.skip_binder(), bounds).clean(cx))
+                }).collect::<Vec<_>>();
+                bounds.extend(regions);
+                if !has_sized && !bounds.is_empty() {
+                    bounds.insert(0, GenericBound::maybe_sized(cx));
+                }
+                ImplTrait(bounds)
+            }
+
+            ty::Closure(..) | ty::Generator(..) => Tuple(vec![]), // FIXME(pcwalton)
+
+            ty::Bound(..) => panic!("Bound"),
+            ty::Placeholder(..) => panic!("Placeholder"),
+            ty::UnnormalizedProjection(..) => panic!("UnnormalizedProjection"),
+            ty::GeneratorWitness(..) => panic!("GeneratorWitness"),
+            ty::Infer(..) => panic!("Infer"),
+            ty::Error => panic!("Error"),
+        }
+    }
+}
+
+impl<'tcx> Clean<Constant> for ty::Const<'tcx> {
+    fn clean(&self, cx: &DocContext<'_>) -> Constant {
+        Constant {
+            type_: self.ty.clean(cx),
+            expr: format!("{}", self),
+        }
+    }
+}
+
+impl Clean<Item> for hir::StructField {
+    fn clean(&self, cx: &DocContext<'_>) -> Item {
+        let local_did = cx.tcx.hir().local_def_id(self.hir_id);
+
+        Item {
+            name: Some(self.ident.name).clean(cx),
+            attrs: self.attrs.clean(cx),
+            source: self.span.clean(cx),
+            visibility: self.vis.clean(cx),
+            stability: get_stability(cx, local_did),
+            deprecation: get_deprecation(cx, local_did),
+            def_id: local_did,
+            inner: StructFieldItem(self.ty.clean(cx)),
+        }
+    }
+}
+
+impl Clean<Item> for ty::FieldDef {
+    fn clean(&self, cx: &DocContext<'_>) -> Item {
+        Item {
+            name: Some(self.ident.name).clean(cx),
+            attrs: cx.tcx.get_attrs(self.did).clean(cx),
+            source: cx.tcx.def_span(self.did).clean(cx),
+            visibility: self.vis.clean(cx),
+            stability: get_stability(cx, self.did),
+            deprecation: get_deprecation(cx, self.did),
+            def_id: self.did,
+            inner: StructFieldItem(cx.tcx.type_of(self.did).clean(cx)),
+        }
+    }
+}
+
+#[derive(Clone, PartialEq, Eq, Debug)]
+pub enum Visibility {
+    Public,
+    Inherited,
+    Crate,
+    Restricted(DefId, Path),
+}
+
+impl Clean<Visibility> for hir::Visibility {
+    fn clean(&self, cx: &DocContext<'_>) -> Visibility {
+        match self.node {
+            hir::VisibilityKind::Public => Visibility::Public,
+            hir::VisibilityKind::Inherited => Visibility::Inherited,
+            hir::VisibilityKind::Crate(_) => Visibility::Crate,
+            hir::VisibilityKind::Restricted { ref path, .. } => {
+                let path = path.clean(cx);
+                let did = register_res(cx, path.res);
+                Visibility::Restricted(did, path)
+            }
+        }
+    }
+}
+
+impl Clean<Visibility> for ty::Visibility {
+    fn clean(&self, _: &DocContext<'_>) -> Visibility {
+        if *self == ty::Visibility::Public { Public } else { Inherited }
+    }
+}
+
+#[derive(Clone, Debug)]
+pub struct Struct {
+    pub struct_type: doctree::StructType,
+    pub generics: Generics,
+    pub fields: Vec<Item>,
+    pub fields_stripped: bool,
+}
+
+#[derive(Clone, Debug)]
+pub struct Union {
+    pub struct_type: doctree::StructType,
+    pub generics: Generics,
+    pub fields: Vec<Item>,
+    pub fields_stripped: bool,
+}
+
+impl Clean<Item> for doctree::Struct<'_> {
+    fn clean(&self, cx: &DocContext<'_>) -> Item {
+        Item {
+            name: Some(self.name.clean(cx)),
+            attrs: self.attrs.clean(cx),
+            source: self.whence.clean(cx),
+            def_id: cx.tcx.hir().local_def_id(self.id),
+            visibility: self.vis.clean(cx),
+            stability: cx.stability(self.id).clean(cx),
+            deprecation: cx.deprecation(self.id).clean(cx),
+            inner: StructItem(Struct {
+                struct_type: self.struct_type,
+                generics: self.generics.clean(cx),
+                fields: self.fields.clean(cx),
+                fields_stripped: false,
+            }),
+        }
+    }
+}
+
+impl Clean<Item> for doctree::Union<'_> {
+    fn clean(&self, cx: &DocContext<'_>) -> Item {
+        Item {
+            name: Some(self.name.clean(cx)),
+            attrs: self.attrs.clean(cx),
+            source: self.whence.clean(cx),
+            def_id: cx.tcx.hir().local_def_id(self.id),
+            visibility: self.vis.clean(cx),
+            stability: cx.stability(self.id).clean(cx),
+            deprecation: cx.deprecation(self.id).clean(cx),
+            inner: UnionItem(Union {
+                struct_type: self.struct_type,
+                generics: self.generics.clean(cx),
+                fields: self.fields.clean(cx),
+                fields_stripped: false,
+            }),
+        }
+    }
+}
+
+/// This is a more limited form of the standard Struct, different in that
+/// it lacks the things most items have (name, id, parameterization). Found
+/// only as a variant in an enum.
+#[derive(Clone, Debug)]
+pub struct VariantStruct {
+    pub struct_type: doctree::StructType,
+    pub fields: Vec<Item>,
+    pub fields_stripped: bool,
+}
+
+impl Clean<VariantStruct> for ::rustc::hir::VariantData {
+    fn clean(&self, cx: &DocContext<'_>) -> VariantStruct {
+        VariantStruct {
+            struct_type: doctree::struct_type_from_def(self),
+            fields: self.fields().iter().map(|x| x.clean(cx)).collect(),
+            fields_stripped: false,
+        }
+    }
+}
+
+#[derive(Clone, Debug)]
+pub struct Enum {
+    pub variants: IndexVec<VariantIdx, Item>,
+    pub generics: Generics,
+    pub variants_stripped: bool,
+}
+
+impl Clean<Item> for doctree::Enum<'_> {
+    fn clean(&self, cx: &DocContext<'_>) -> Item {
+        Item {
+            name: Some(self.name.clean(cx)),
+            attrs: self.attrs.clean(cx),
+            source: self.whence.clean(cx),
+            def_id: cx.tcx.hir().local_def_id(self.id),
+            visibility: self.vis.clean(cx),
+            stability: cx.stability(self.id).clean(cx),
+            deprecation: cx.deprecation(self.id).clean(cx),
+            inner: EnumItem(Enum {
+                variants: self.variants.iter().map(|v| v.clean(cx)).collect(),
+                generics: self.generics.clean(cx),
+                variants_stripped: false,
+            }),
+        }
+    }
+}
+
+#[derive(Clone, Debug)]
+pub struct Variant {
+    pub kind: VariantKind,
+}
+
+impl Clean<Item> for doctree::Variant<'_> {
+    fn clean(&self, cx: &DocContext<'_>) -> Item {
+        Item {
+            name: Some(self.name.clean(cx)),
+            attrs: self.attrs.clean(cx),
+            source: self.whence.clean(cx),
+            visibility: Inherited,
+            stability: cx.stability(self.id).clean(cx),
+            deprecation: cx.deprecation(self.id).clean(cx),
+            def_id: cx.tcx.hir().local_def_id(self.id),
+            inner: VariantItem(Variant {
+                kind: self.def.clean(cx),
+            }),
+        }
+    }
+}
+
+impl Clean<Item> for ty::VariantDef {
+    fn clean(&self, cx: &DocContext<'_>) -> Item {
+        let kind = match self.ctor_kind {
+            CtorKind::Const => VariantKind::CLike,
+            CtorKind::Fn => {
+                VariantKind::Tuple(
+                    self.fields.iter().map(|f| cx.tcx.type_of(f.did).clean(cx)).collect()
+                )
+            }
+            CtorKind::Fictive => {
+                VariantKind::Struct(VariantStruct {
+                    struct_type: doctree::Plain,
+                    fields_stripped: false,
+                    fields: self.fields.iter().map(|field| {
+                        Item {
+                            source: cx.tcx.def_span(field.did).clean(cx),
+                            name: Some(field.ident.name.clean(cx)),
+                            attrs: cx.tcx.get_attrs(field.did).clean(cx),
+                            visibility: field.vis.clean(cx),
+                            def_id: field.did,
+                            stability: get_stability(cx, field.did),
+                            deprecation: get_deprecation(cx, field.did),
+                            inner: StructFieldItem(cx.tcx.type_of(field.did).clean(cx))
+                        }
+                    }).collect()
+                })
+            }
+        };
+        Item {
+            name: Some(self.ident.clean(cx)),
+            attrs: inline::load_attrs(cx, self.def_id).clean(cx),
+            source: cx.tcx.def_span(self.def_id).clean(cx),
+            visibility: Inherited,
+            def_id: self.def_id,
+            inner: VariantItem(Variant { kind }),
+            stability: get_stability(cx, self.def_id),
+            deprecation: get_deprecation(cx, self.def_id),
+        }
+    }
+}
+
+#[derive(Clone, Debug)]
+pub enum VariantKind {
+    CLike,
+    Tuple(Vec<Type>),
+    Struct(VariantStruct),
+}
+
+impl Clean<VariantKind> for hir::VariantData {
+    fn clean(&self, cx: &DocContext<'_>) -> VariantKind {
+        match self {
+            hir::VariantData::Struct(..) => VariantKind::Struct(self.clean(cx)),
+            hir::VariantData::Tuple(..) =>
+                VariantKind::Tuple(self.fields().iter().map(|x| x.ty.clean(cx)).collect()),
+            hir::VariantData::Unit(..) => VariantKind::CLike,
+        }
+    }
+}
+
+#[derive(Clone, Debug)]
+pub struct Span {
+    pub filename: FileName,
+    pub loline: usize,
+    pub locol: usize,
+    pub hiline: usize,
+    pub hicol: usize,
+    pub original: syntax_pos::Span,
+}
+
+impl Span {
+    pub fn empty() -> Span {
+        Span {
+            filename: FileName::Anon(0),
+            loline: 0, locol: 0,
+            hiline: 0, hicol: 0,
+            original: syntax_pos::DUMMY_SP,
+        }
+    }
+
+    pub fn span(&self) -> syntax_pos::Span {
+        self.original
+    }
+}
+
+impl Clean<Span> for syntax_pos::Span {
+    fn clean(&self, cx: &DocContext<'_>) -> Span {
+        if self.is_dummy() {
+            return Span::empty();
+        }
+
+        let cm = cx.sess().source_map();
+        let filename = cm.span_to_filename(*self);
+        let lo = cm.lookup_char_pos(self.lo());
+        let hi = cm.lookup_char_pos(self.hi());
+        Span {
+            filename,
+            loline: lo.line,
+            locol: lo.col.to_usize(),
+            hiline: hi.line,
+            hicol: hi.col.to_usize(),
+            original: *self,
+        }
+    }
+}
+
+#[derive(Clone, PartialEq, Eq, Debug, Hash)]
+pub struct Path {
+    pub global: bool,
+    pub res: Res,
+    pub segments: Vec<PathSegment>,
+}
+
+impl Path {
+    pub fn last_name(&self) -> &str {
+        self.segments.last().expect("segments were empty").name.as_str()
+    }
+}
+
+impl Clean<Path> for hir::Path {
+    fn clean(&self, cx: &DocContext<'_>) -> Path {
+        Path {
+            global: self.is_global(),
+            res: self.res,
+            segments: if self.is_global() { &self.segments[1..] } else { &self.segments }.clean(cx),
+        }
+    }
+}
+
+#[derive(Clone, PartialEq, Eq, Debug, Hash)]
+pub enum GenericArg {
+    Lifetime(Lifetime),
+    Type(Type),
+    Const(Constant),
+}
+
+#[derive(Clone, PartialEq, Eq, Debug, Hash)]
+pub enum GenericArgs {
+    AngleBracketed {
+        args: Vec<GenericArg>,
+        bindings: Vec<TypeBinding>,
+    },
+    Parenthesized {
+        inputs: Vec<Type>,
+        output: Option<Type>,
+    }
+}
+
+impl Clean<GenericArgs> for hir::GenericArgs {
+    fn clean(&self, cx: &DocContext<'_>) -> GenericArgs {
+        if self.parenthesized {
+            let output = self.bindings[0].ty().clean(cx);
+            GenericArgs::Parenthesized {
+                inputs: self.inputs().clean(cx),
+                output: if output != Type::Tuple(Vec::new()) { Some(output) } else { None }
+            }
+        } else {
+            let elide_lifetimes = self.args.iter().all(|arg| match arg {
+                hir::GenericArg::Lifetime(lt) => lt.is_elided(),
+                _ => true,
+            });
+            GenericArgs::AngleBracketed {
+                args: self.args.iter().filter_map(|arg| match arg {
+                    hir::GenericArg::Lifetime(lt) if !elide_lifetimes => {
+                        Some(GenericArg::Lifetime(lt.clean(cx)))
+                    }
+                    hir::GenericArg::Lifetime(_) => None,
+                    hir::GenericArg::Type(ty) => Some(GenericArg::Type(ty.clean(cx))),
+                    hir::GenericArg::Const(ct) => Some(GenericArg::Const(ct.clean(cx))),
+                }).collect(),
+                bindings: self.bindings.clean(cx),
+            }
+        }
+    }
+}
+
+#[derive(Clone, PartialEq, Eq, Debug, Hash)]
+pub struct PathSegment {
+    pub name: String,
+    pub args: GenericArgs,
+}
+
+impl Clean<PathSegment> for hir::PathSegment {
+    fn clean(&self, cx: &DocContext<'_>) -> PathSegment {
+        PathSegment {
+            name: self.ident.name.clean(cx),
+            args: self.generic_args().clean(cx),
+        }
+    }
+}
+
+fn strip_type(ty: Type) -> Type {
+    match ty {
+        Type::ResolvedPath { path, param_names, did, is_generic } => {
+            Type::ResolvedPath { path: strip_path(&path), param_names, did, is_generic }
+        }
+        Type::Tuple(inner_tys) => {
+            Type::Tuple(inner_tys.iter().map(|t| strip_type(t.clone())).collect())
+        }
+        Type::Slice(inner_ty) => Type::Slice(Box::new(strip_type(*inner_ty))),
+        Type::Array(inner_ty, s) => Type::Array(Box::new(strip_type(*inner_ty)), s),
+        Type::RawPointer(m, inner_ty) => Type::RawPointer(m, Box::new(strip_type(*inner_ty))),
+        Type::BorrowedRef { lifetime, mutability, type_ } => {
+            Type::BorrowedRef { lifetime, mutability, type_: Box::new(strip_type(*type_)) }
+        }
+        Type::QPath { name, self_type, trait_ } => {
+            Type::QPath {
+                name,
+                self_type: Box::new(strip_type(*self_type)), trait_: Box::new(strip_type(*trait_))
+            }
+        }
+        _ => ty
+    }
+}
+
+fn strip_path(path: &Path) -> Path {
+    let segments = path.segments.iter().map(|s| {
+        PathSegment {
+            name: s.name.clone(),
+            args: GenericArgs::AngleBracketed {
+                args: vec![],
+                bindings: vec![],
+            }
+        }
+    }).collect();
+
+    Path {
+        global: path.global,
+        res: path.res.clone(),
+        segments,
+    }
+}
+
+fn qpath_to_string(p: &hir::QPath) -> String {
+    let segments = match *p {
+        hir::QPath::Resolved(_, ref path) => &path.segments,
+        hir::QPath::TypeRelative(_, ref segment) => return segment.ident.to_string(),
+    };
+
+    let mut s = String::new();
+    for (i, seg) in segments.iter().enumerate() {
+        if i > 0 {
+            s.push_str("::");
+        }
+        if seg.ident.name != kw::PathRoot {
+            s.push_str(&seg.ident.as_str());
+        }
+    }
+    s
+}
+
+impl Clean<String> for Ident {
+    #[inline]
+    fn clean(&self, cx: &DocContext<'_>) -> String {
+        self.name.clean(cx)
+    }
+}
+
+impl Clean<String> for ast::Name {
+    #[inline]
+    fn clean(&self, _: &DocContext<'_>) -> String {
+        self.to_string()
+    }
+}
+
+#[derive(Clone, Debug)]
+pub struct Typedef {
+    pub type_: Type,
+    pub generics: Generics,
+}
+
+impl Clean<Item> for doctree::Typedef<'_> {
+    fn clean(&self, cx: &DocContext<'_>) -> Item {
+        Item {
+            name: Some(self.name.clean(cx)),
+            attrs: self.attrs.clean(cx),
+            source: self.whence.clean(cx),
+            def_id: cx.tcx.hir().local_def_id(self.id),
+            visibility: self.vis.clean(cx),
+            stability: cx.stability(self.id).clean(cx),
+            deprecation: cx.deprecation(self.id).clean(cx),
+            inner: TypedefItem(Typedef {
+                type_: self.ty.clean(cx),
+                generics: self.gen.clean(cx),
+            }, false),
+        }
+    }
+}
+
+#[derive(Clone, Debug)]
+pub struct OpaqueTy {
+    pub bounds: Vec<GenericBound>,
+    pub generics: Generics,
+}
+
+impl Clean<Item> for doctree::OpaqueTy<'_> {
+    fn clean(&self, cx: &DocContext<'_>) -> Item {
+        Item {
+            name: Some(self.name.clean(cx)),
+            attrs: self.attrs.clean(cx),
+            source: self.whence.clean(cx),
+            def_id: cx.tcx.hir().local_def_id(self.id),
+            visibility: self.vis.clean(cx),
+            stability: cx.stability(self.id).clean(cx),
+            deprecation: cx.deprecation(self.id).clean(cx),
+            inner: OpaqueTyItem(OpaqueTy {
+                bounds: self.opaque_ty.bounds.clean(cx),
+                generics: self.opaque_ty.generics.clean(cx),
+            }, false),
+        }
+    }
+}
+
+#[derive(Clone, PartialEq, Eq, Debug, Hash)]
+pub struct BareFunctionDecl {
+    pub unsafety: hir::Unsafety,
+    pub generic_params: Vec<GenericParamDef>,
+    pub decl: FnDecl,
+    pub abi: Abi,
+}
+
+impl Clean<BareFunctionDecl> for hir::BareFnTy {
+    fn clean(&self, cx: &DocContext<'_>) -> BareFunctionDecl {
+        let (generic_params, decl) = enter_impl_trait(cx, || {
+            (self.generic_params.clean(cx), (&*self.decl, &self.param_names[..]).clean(cx))
+        });
+        BareFunctionDecl {
+            unsafety: self.unsafety,
+            abi: self.abi,
+            decl,
+            generic_params,
+        }
+    }
+}
+
+#[derive(Clone, Debug)]
+pub struct Static {
+    pub type_: Type,
+    pub mutability: Mutability,
+    /// It's useful to have the value of a static documented, but I have no
+    /// desire to represent expressions (that'd basically be all of the AST,
+    /// which is huge!). So, have a string.
+    pub expr: String,
+}
+
+impl Clean<Item> for doctree::Static<'_> {
+    fn clean(&self, cx: &DocContext<'_>) -> Item {
+        debug!("cleaning static {}: {:?}", self.name.clean(cx), self);
+        Item {
+            name: Some(self.name.clean(cx)),
+            attrs: self.attrs.clean(cx),
+            source: self.whence.clean(cx),
+            def_id: cx.tcx.hir().local_def_id(self.id),
+            visibility: self.vis.clean(cx),
+            stability: cx.stability(self.id).clean(cx),
+            deprecation: cx.deprecation(self.id).clean(cx),
+            inner: StaticItem(Static {
+                type_: self.type_.clean(cx),
+                mutability: self.mutability.clean(cx),
+                expr: print_const_expr(cx, self.expr),
+            }),
+        }
+    }
+}
+
+#[derive(Clone, PartialEq, Eq, Hash, Debug)]
+pub struct Constant {
+    pub type_: Type,
+    pub expr: String,
+}
+
+impl Clean<Item> for doctree::Constant<'_> {
+    fn clean(&self, cx: &DocContext<'_>) -> Item {
+        Item {
+            name: Some(self.name.clean(cx)),
+            attrs: self.attrs.clean(cx),
+            source: self.whence.clean(cx),
+            def_id: cx.tcx.hir().local_def_id(self.id),
+            visibility: self.vis.clean(cx),
+            stability: cx.stability(self.id).clean(cx),
+            deprecation: cx.deprecation(self.id).clean(cx),
+            inner: ConstantItem(Constant {
+                type_: self.type_.clean(cx),
+                expr: print_const_expr(cx, self.expr),
+            }),
+        }
+    }
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Copy, Hash)]
+pub enum Mutability {
+    Mutable,
+    Immutable,
+}
+
+impl Clean<Mutability> for hir::Mutability {
+    fn clean(&self, _: &DocContext<'_>) -> Mutability {
+        match self {
+            &hir::Mutability::Mutable => Mutable,
+            &hir::Mutability::Immutable => Immutable,
+        }
+    }
+}
+
+#[derive(Clone, PartialEq, Debug)]
+pub enum ImplPolarity {
+    Positive,
+    Negative,
+}
+
+impl Clean<ImplPolarity> for ty::ImplPolarity {
+    fn clean(&self, _: &DocContext<'_>) -> ImplPolarity {
+        match self {
+            &ty::ImplPolarity::Positive |
+            // FIXME: do we want to do something else here?
+            &ty::ImplPolarity::Reservation => ImplPolarity::Positive,
+            &ty::ImplPolarity::Negative => ImplPolarity::Negative,
+        }
+    }
+}
+
+#[derive(Clone, Debug)]
+pub struct Impl {
+    pub unsafety: hir::Unsafety,
+    pub generics: Generics,
+    pub provided_trait_methods: FxHashSet<String>,
+    pub trait_: Option<Type>,
+    pub for_: Type,
+    pub items: Vec<Item>,
+    pub polarity: Option<ImplPolarity>,
+    pub synthetic: bool,
+    pub blanket_impl: Option<Type>,
+}
+
+pub fn get_auto_trait_and_blanket_impls(
+    cx: &DocContext<'tcx>,
+    ty: Ty<'tcx>,
+    param_env_def_id: DefId,
+) -> impl Iterator<Item = Item> {
+    AutoTraitFinder::new(cx).get_auto_trait_impls(ty, param_env_def_id).into_iter()
+        .chain(BlanketImplFinder::new(cx).get_blanket_impls(ty, param_env_def_id))
+}
+
+impl Clean<Vec<Item>> for doctree::Impl<'_> {
+    fn clean(&self, cx: &DocContext<'_>) -> Vec<Item> {
+        let mut ret = Vec::new();
+        let trait_ = self.trait_.clean(cx);
+        let items = self.items.iter().map(|ii| ii.clean(cx)).collect::<Vec<_>>();
+        let def_id = cx.tcx.hir().local_def_id(self.id);
+
+        // If this impl block is an implementation of the Deref trait, then we
+        // need to try inlining the target's inherent impl blocks as well.
+        if trait_.def_id() == cx.tcx.lang_items().deref_trait() {
+            build_deref_target_impls(cx, &items, &mut ret);
+        }
+
+        let provided = trait_.def_id().map(|did| {
+            cx.tcx.provided_trait_methods(did)
+                  .into_iter()
+                  .map(|meth| meth.ident.to_string())
+                  .collect()
+        }).unwrap_or_default();
+
+        ret.push(Item {
+            name: None,
+            attrs: self.attrs.clean(cx),
+            source: self.whence.clean(cx),
+            def_id,
+            visibility: self.vis.clean(cx),
+            stability: cx.stability(self.id).clean(cx),
+            deprecation: cx.deprecation(self.id).clean(cx),
+            inner: ImplItem(Impl {
+                unsafety: self.unsafety,
+                generics: self.generics.clean(cx),
+                provided_trait_methods: provided,
+                trait_,
+                for_: self.for_.clean(cx),
+                items,
+                polarity: Some(cx.tcx.impl_polarity(def_id).clean(cx)),
+                synthetic: false,
+                blanket_impl: None,
+            })
+        });
+        ret
+    }
+}
+
+fn build_deref_target_impls(cx: &DocContext<'_>,
+                            items: &[Item],
+                            ret: &mut Vec<Item>) {
+    use self::PrimitiveType::*;
+    let tcx = cx.tcx;
+
+    for item in items {
+        let target = match item.inner {
+            TypedefItem(ref t, true) => &t.type_,
+            _ => continue,
+        };
+        let primitive = match *target {
+            ResolvedPath { did, .. } if did.is_local() => continue,
+            ResolvedPath { did, .. } => {
+                ret.extend(inline::build_impls(cx, did, None));
+                continue
+            }
+            _ => match target.primitive_type() {
+                Some(prim) => prim,
+                None => continue,
+            }
+        };
+        let did = match primitive {
+            Isize => tcx.lang_items().isize_impl(),
+            I8 => tcx.lang_items().i8_impl(),
+            I16 => tcx.lang_items().i16_impl(),
+            I32 => tcx.lang_items().i32_impl(),
+            I64 => tcx.lang_items().i64_impl(),
+            I128 => tcx.lang_items().i128_impl(),
+            Usize => tcx.lang_items().usize_impl(),
+            U8 => tcx.lang_items().u8_impl(),
+            U16 => tcx.lang_items().u16_impl(),
+            U32 => tcx.lang_items().u32_impl(),
+            U64 => tcx.lang_items().u64_impl(),
+            U128 => tcx.lang_items().u128_impl(),
+            F32 => tcx.lang_items().f32_impl(),
+            F64 => tcx.lang_items().f64_impl(),
+            Char => tcx.lang_items().char_impl(),
+            Bool => tcx.lang_items().bool_impl(),
+            Str => tcx.lang_items().str_impl(),
+            Slice => tcx.lang_items().slice_impl(),
+            Array => tcx.lang_items().slice_impl(),
+            Tuple => None,
+            Unit => None,
+            RawPointer => tcx.lang_items().const_ptr_impl(),
+            Reference => None,
+            Fn => None,
+            Never => None,
+        };
+        if let Some(did) = did {
+            if !did.is_local() {
+                inline::build_impl(cx, did, None, ret);
+            }
+        }
+    }
+}
+
+impl Clean<Vec<Item>> for doctree::ExternCrate<'_> {
+    fn clean(&self, cx: &DocContext<'_>) -> Vec<Item> {
+
+        let please_inline = self.vis.node.is_pub() && self.attrs.iter().any(|a| {
+            a.check_name(sym::doc) && match a.meta_item_list() {
+                Some(l) => attr::list_contains_name(&l, sym::inline),
+                None => false,
+            }
+        });
+
+        if please_inline {
+            let mut visited = FxHashSet::default();
+
+            let res = Res::Def(
+                DefKind::Mod,
+                DefId {
+                    krate: self.cnum,
+                    index: CRATE_DEF_INDEX,
+                },
+            );
+
+            if let Some(items) = inline::try_inline(
+                cx, res, self.name,
+                Some(rustc::ty::Attributes::Borrowed(self.attrs)),
+                &mut visited
+            ) {
+                return items;
+            }
+        }
+
+        vec![Item {
+            name: None,
+            attrs: self.attrs.clean(cx),
+            source: self.whence.clean(cx),
+            def_id: DefId { krate: self.cnum, index: CRATE_DEF_INDEX },
+            visibility: self.vis.clean(cx),
+            stability: None,
+            deprecation: None,
+            inner: ExternCrateItem(self.name.clean(cx), self.path.clone())
+        }]
+    }
+}
+
+impl Clean<Vec<Item>> for doctree::Import<'_> {
+    fn clean(&self, cx: &DocContext<'_>) -> Vec<Item> {
+        // We consider inlining the documentation of `pub use` statements, but we
+        // forcefully don't inline if this is not public or if the
+        // #[doc(no_inline)] attribute is present.
+        // Don't inline doc(hidden) imports so they can be stripped at a later stage.
+        let mut denied = !self.vis.node.is_pub() || self.attrs.iter().any(|a| {
+            a.check_name(sym::doc) && match a.meta_item_list() {
+                Some(l) => attr::list_contains_name(&l, sym::no_inline) ||
+                           attr::list_contains_name(&l, sym::hidden),
+                None => false,
+            }
+        });
+        // Also check whether imports were asked to be inlined, in case we're trying to re-export a
+        // crate in Rust 2018+
+        let please_inline = self.attrs.lists(sym::doc).has_word(sym::inline);
+        let path = self.path.clean(cx);
+        let inner = if self.glob {
+            if !denied {
+                let mut visited = FxHashSet::default();
+                if let Some(items) = inline::try_inline_glob(cx, path.res, &mut visited) {
+                    return items;
+                }
+            }
+
+            Import::Glob(resolve_use_source(cx, path))
+        } else {
+            let name = self.name;
+            if !please_inline {
+                match path.res {
+                    Res::Def(DefKind::Mod, did) => {
+                        if !did.is_local() && did.index == CRATE_DEF_INDEX {
+                            // if we're `pub use`ing an extern crate root, don't inline it unless we
+                            // were specifically asked for it
+                            denied = true;
+                        }
+                    }
+                    _ => {}
+                }
+            }
+            if !denied {
+                let mut visited = FxHashSet::default();
+                if let Some(items) = inline::try_inline(
+                    cx, path.res, name,
+                    Some(rustc::ty::Attributes::Borrowed(self.attrs)),
+                    &mut visited
+                ) {
+                    return items;
+                }
+            }
+            Import::Simple(name.clean(cx), resolve_use_source(cx, path))
+        };
+
+        vec![Item {
+            name: None,
+            attrs: self.attrs.clean(cx),
+            source: self.whence.clean(cx),
+            def_id: cx.tcx.hir().local_def_id_from_node_id(ast::CRATE_NODE_ID),
+            visibility: self.vis.clean(cx),
+            stability: None,
+            deprecation: None,
+            inner: ImportItem(inner)
+        }]
+    }
+}
+
+#[derive(Clone, Debug)]
+pub enum Import {
+    // use source as str;
+    Simple(String, ImportSource),
+    // use source::*;
+    Glob(ImportSource)
+}
+
+#[derive(Clone, Debug)]
+pub struct ImportSource {
+    pub path: Path,
+    pub did: Option<DefId>,
+}
+
+impl Clean<Item> for doctree::ForeignItem<'_> {
+    fn clean(&self, cx: &DocContext<'_>) -> Item {
+        let inner = match self.kind {
+            hir::ForeignItemKind::Fn(ref decl, ref names, ref generics) => {
+                let abi = cx.tcx.hir().get_foreign_abi(self.id);
+                let (generics, decl) = enter_impl_trait(cx, || {
+                    (generics.clean(cx), (&**decl, &names[..]).clean(cx))
+                });
+                let (all_types, ret_types) = get_all_types(&generics, &decl, cx);
+                ForeignFunctionItem(Function {
+                    decl,
+                    generics,
+                    header: hir::FnHeader {
+                        unsafety: hir::Unsafety::Unsafe,
+                        abi,
+                        constness: hir::Constness::NotConst,
+                        asyncness: hir::IsAsync::NotAsync,
+                    },
+                    all_types,
+                    ret_types,
+                })
+            }
+            hir::ForeignItemKind::Static(ref ty, mutbl) => {
+                ForeignStaticItem(Static {
+                    type_: ty.clean(cx),
+                    mutability: mutbl.clean(cx),
+                    expr: String::new(),
+                })
+            }
+            hir::ForeignItemKind::Type => {
+                ForeignTypeItem
+            }
+        };
+
+        Item {
+            name: Some(self.name.clean(cx)),
+            attrs: self.attrs.clean(cx),
+            source: self.whence.clean(cx),
+            def_id: cx.tcx.hir().local_def_id(self.id),
+            visibility: self.vis.clean(cx),
+            stability: cx.stability(self.id).clean(cx),
+            deprecation: cx.deprecation(self.id).clean(cx),
+            inner,
+        }
+    }
+}
+
+// Utilities
+
+pub trait ToSource {
+    fn to_src(&self, cx: &DocContext<'_>) -> String;
+}
+
+impl ToSource for syntax_pos::Span {
+    fn to_src(&self, cx: &DocContext<'_>) -> String {
+        debug!("converting span {:?} to snippet", self.clean(cx));
+        let sn = match cx.sess().source_map().span_to_snippet(*self) {
+            Ok(x) => x,
+            Err(_) => String::new()
+        };
+        debug!("got snippet {}", sn);
+        sn
+    }
+}
+
+fn name_from_pat(p: &hir::Pat) -> String {
+    use rustc::hir::*;
+    debug!("trying to get a name from pattern: {:?}", p);
+
+    match p.kind {
+        PatKind::Wild => "_".to_string(),
+        PatKind::Binding(_, _, ident, _) => ident.to_string(),
+        PatKind::TupleStruct(ref p, ..) | PatKind::Path(ref p) => qpath_to_string(p),
+        PatKind::Struct(ref name, ref fields, etc) => {
+            format!("{} {{ {}{} }}", qpath_to_string(name),
+                fields.iter().map(|fp| format!("{}: {}", fp.ident, name_from_pat(&fp.pat)))
+                             .collect::<Vec<String>>().join(", "),
+                if etc { ", .." } else { "" }
+            )
+        }
+        PatKind::Or(ref pats) => {
+            pats.iter().map(|p| name_from_pat(&**p)).collect::<Vec<String>>().join(" | ")
+        }
+        PatKind::Tuple(ref elts, _) => format!("({})", elts.iter().map(|p| name_from_pat(&**p))
+                                            .collect::<Vec<String>>().join(", ")),
+        PatKind::Box(ref p) => name_from_pat(&**p),
+        PatKind::Ref(ref p, _) => name_from_pat(&**p),
+        PatKind::Lit(..) => {
+            warn!("tried to get argument name from PatKind::Lit, \
+                  which is silly in function arguments");
+            "()".to_string()
+        },
+        PatKind::Range(..) => panic!("tried to get argument name from PatKind::Range, \
+                              which is not allowed in function arguments"),
+        PatKind::Slice(ref begin, ref mid, ref end) => {
+            let begin = begin.iter().map(|p| name_from_pat(&**p));
+            let mid = mid.as_ref().map(|p| format!("..{}", name_from_pat(&**p))).into_iter();
+            let end = end.iter().map(|p| name_from_pat(&**p));
+            format!("[{}]", begin.chain(mid).chain(end).collect::<Vec<_>>().join(", "))
+        },
+    }
+}
+
+fn print_const(cx: &DocContext<'_>, n: &ty::Const<'_>) -> String {
+    match n.val {
+        ty::ConstKind::Unevaluated(def_id, _) => {
+            if let Some(hir_id) = cx.tcx.hir().as_local_hir_id(def_id) {
+                print_const_expr(cx, cx.tcx.hir().body_owned_by(hir_id))
+            } else {
+                inline::print_inlined_const(cx, def_id)
+            }
+        },
+        _ => {
+            let mut s = n.to_string();
+            // array lengths are obviously usize
+            if s.ends_with("usize") {
+                let n = s.len() - "usize".len();
+                s.truncate(n);
+                if s.ends_with(": ") {
+                    let n = s.len() - ": ".len();
+                    s.truncate(n);
+                }
+            }
+            s
+        },
+    }
+}
+
+fn print_const_expr(cx: &DocContext<'_>, body: hir::BodyId) -> String {
+    cx.tcx.hir().hir_to_pretty_string(body.hir_id)
+}
+
+/// Given a type Path, resolve it to a Type using the TyCtxt
+fn resolve_type(cx: &DocContext<'_>,
+                path: Path,
+                id: hir::HirId) -> Type {
+    if id == hir::DUMMY_HIR_ID {
+        debug!("resolve_type({:?})", path);
+    } else {
+        debug!("resolve_type({:?},{:?})", path, id);
+    }
+
+    let is_generic = match path.res {
+        Res::PrimTy(p) => match p {
+            hir::Str => return Primitive(PrimitiveType::Str),
+            hir::Bool => return Primitive(PrimitiveType::Bool),
+            hir::Char => return Primitive(PrimitiveType::Char),
+            hir::Int(int_ty) => return Primitive(int_ty.into()),
+            hir::Uint(uint_ty) => return Primitive(uint_ty.into()),
+            hir::Float(float_ty) => return Primitive(float_ty.into()),
+        },
+        Res::SelfTy(..) if path.segments.len() == 1 => {
+            return Generic(kw::SelfUpper.to_string());
+        }
+        Res::Def(DefKind::TyParam, _) if path.segments.len() == 1 => {
+            return Generic(format!("{:#}", path.print()));
+        }
+        Res::SelfTy(..)
+        | Res::Def(DefKind::TyParam, _)
+        | Res::Def(DefKind::AssocTy, _) => true,
+        _ => false,
+    };
+    let did = register_res(&*cx, path.res);
+    ResolvedPath { path, param_names: None, did, is_generic }
+}
+
+pub fn register_res(cx: &DocContext<'_>, res: Res) -> DefId {
+    debug!("register_res({:?})", res);
+
+    let (did, kind) = match res {
+        Res::Def(DefKind::Fn, i) => (i, TypeKind::Function),
+        Res::Def(DefKind::TyAlias, i) => (i, TypeKind::Typedef),
+        Res::Def(DefKind::Enum, i) => (i, TypeKind::Enum),
+        Res::Def(DefKind::Trait, i) => (i, TypeKind::Trait),
+        Res::Def(DefKind::Struct, i) => (i, TypeKind::Struct),
+        Res::Def(DefKind::Union, i) => (i, TypeKind::Union),
+        Res::Def(DefKind::Mod, i) => (i, TypeKind::Module),
+        Res::Def(DefKind::ForeignTy, i) => (i, TypeKind::Foreign),
+        Res::Def(DefKind::Const, i) => (i, TypeKind::Const),
+        Res::Def(DefKind::Static, i) => (i, TypeKind::Static),
+        Res::Def(DefKind::Variant, i) => (cx.tcx.parent(i).expect("cannot get parent def id"),
+                            TypeKind::Enum),
+        Res::Def(DefKind::Macro(mac_kind), i) => match mac_kind {
+            MacroKind::Bang => (i, TypeKind::Macro),
+            MacroKind::Attr => (i, TypeKind::Attr),
+            MacroKind::Derive => (i, TypeKind::Derive),
+        },
+        Res::Def(DefKind::TraitAlias, i) => (i, TypeKind::TraitAlias),
+        Res::SelfTy(Some(def_id), _) => (def_id, TypeKind::Trait),
+        Res::SelfTy(_, Some(impl_def_id)) => return impl_def_id,
+        _ => return res.def_id()
+    };
+    if did.is_local() { return did }
+    inline::record_extern_fqn(cx, did, kind);
+    if let TypeKind::Trait = kind {
+        inline::record_extern_trait(cx, did);
+    }
+    did
+}
+
+fn resolve_use_source(cx: &DocContext<'_>, path: Path) -> ImportSource {
+    ImportSource {
+        did: if path.res.opt_def_id().is_none() {
+            None
+        } else {
+            Some(register_res(cx, path.res))
+        },
+        path,
+    }
+}
+
+#[derive(Clone, Debug)]
+pub struct Macro {
+    pub source: String,
+    pub imported_from: Option<String>,
+}
+
+impl Clean<Item> for doctree::Macro<'_> {
+    fn clean(&self, cx: &DocContext<'_>) -> Item {
+        let name = self.name.clean(cx);
+        Item {
+            name: Some(name.clone()),
+            attrs: self.attrs.clean(cx),
+            source: self.whence.clean(cx),
+            visibility: Public,
+            stability: cx.stability(self.hid).clean(cx),
+            deprecation: cx.deprecation(self.hid).clean(cx),
+            def_id: self.def_id,
+            inner: MacroItem(Macro {
+                source: format!("macro_rules! {} {{\n{}}}",
+                                name,
+                                self.matchers.iter().map(|span| {
+                                    format!("    {} => {{ ... }};\n", span.to_src(cx))
+                                }).collect::<String>()),
+                imported_from: self.imported_from.clean(cx),
+            }),
+        }
+    }
+}
+
+#[derive(Clone, Debug)]
+pub struct ProcMacro {
+    pub kind: MacroKind,
+    pub helpers: Vec<String>,
+}
+
+impl Clean<Item> for doctree::ProcMacro<'_> {
+    fn clean(&self, cx: &DocContext<'_>) -> Item {
+        Item {
+            name: Some(self.name.clean(cx)),
+            attrs: self.attrs.clean(cx),
+            source: self.whence.clean(cx),
+            visibility: Public,
+            stability: cx.stability(self.id).clean(cx),
+            deprecation: cx.deprecation(self.id).clean(cx),
+            def_id: cx.tcx.hir().local_def_id(self.id),
+            inner: ProcMacroItem(ProcMacro {
+                kind: self.kind,
+                helpers: self.helpers.clean(cx),
+            }),
+        }
+    }
+}
+
+#[derive(Clone, Debug)]
+pub struct Stability {
+    pub level: stability::StabilityLevel,
+    pub feature: Option<String>,
+    pub since: String,
+    pub deprecation: Option<Deprecation>,
+    pub unstable_reason: Option<String>,
+    pub issue: Option<NonZeroU32>,
+}
+
+#[derive(Clone, Debug)]
+pub struct Deprecation {
+    pub since: Option<String>,
+    pub note: Option<String>,
+}
+
+impl Clean<Stability> for attr::Stability {
+    fn clean(&self, _: &DocContext<'_>) -> Stability {
+        Stability {
+            level: stability::StabilityLevel::from_attr_level(&self.level),
+            feature: Some(self.feature.to_string()).filter(|f| !f.is_empty()),
+            since: match self.level {
+                attr::Stable {ref since} => since.to_string(),
+                _ => String::new(),
+            },
+            deprecation: self.rustc_depr.as_ref().map(|d| {
+                Deprecation {
+                    note: Some(d.reason.to_string()).filter(|r| !r.is_empty()),
+                    since: Some(d.since.to_string()).filter(|d| !d.is_empty()),
+                }
+            }),
+            unstable_reason: match self.level {
+                attr::Unstable { reason: Some(ref reason), .. } => Some(reason.to_string()),
+                _ => None,
+            },
+            issue: match self.level {
+                attr::Unstable {issue, ..} => issue,
+                _ => None,
+            }
+        }
+    }
+}
+
+impl<'a> Clean<Stability> for &'a attr::Stability {
+    fn clean(&self, dc: &DocContext<'_>) -> Stability {
+        (**self).clean(dc)
+    }
+}
+
+impl Clean<Deprecation> for attr::Deprecation {
+    fn clean(&self, _: &DocContext<'_>) -> Deprecation {
+        Deprecation {
+            since: self.since.map(|s| s.to_string()).filter(|s| !s.is_empty()),
+            note: self.note.map(|n| n.to_string()).filter(|n| !n.is_empty()),
+        }
+    }
+}
+
+/// An type binding on an associated type (e.g., `A = Bar` in `Foo<A = Bar>` or
+/// `A: Send + Sync` in `Foo<A: Send + Sync>`).
+#[derive(Clone, PartialEq, Eq, Debug, Hash)]
+pub struct TypeBinding {
+    pub name: String,
+    pub kind: TypeBindingKind,
+}
+
+#[derive(Clone, PartialEq, Eq, Debug, Hash)]
+pub enum TypeBindingKind {
+    Equality {
+        ty: Type,
+    },
+    Constraint {
+        bounds: Vec<GenericBound>,
+    },
+}
+
+impl TypeBinding {
+    pub fn ty(&self) -> &Type {
+        match self.kind {
+            TypeBindingKind::Equality { ref ty } => ty,
+            _ => panic!("expected equality type binding for parenthesized generic args"),
+        }
+    }
+}
+
+impl Clean<TypeBinding> for hir::TypeBinding {
+    fn clean(&self, cx: &DocContext<'_>) -> TypeBinding {
+        TypeBinding {
+            name: self.ident.name.clean(cx),
+            kind: self.kind.clean(cx),
+        }
+    }
+}
+
+impl Clean<TypeBindingKind> for hir::TypeBindingKind {
+    fn clean(&self, cx: &DocContext<'_>) -> TypeBindingKind {
+        match *self {
+            hir::TypeBindingKind::Equality { ref ty } =>
+                TypeBindingKind::Equality {
+                    ty: ty.clean(cx),
+                },
+            hir::TypeBindingKind::Constraint { ref bounds } =>
+                TypeBindingKind::Constraint {
+                    bounds: bounds.into_iter().map(|b| b.clean(cx)).collect(),
+                },
+        }
+    }
+}
+
+pub fn enter_impl_trait<F, R>(cx: &DocContext<'_>, f: F) -> R
+where
+    F: FnOnce() -> R,
+{
+    let old_bounds = mem::take(&mut *cx.impl_trait_bounds.borrow_mut());
+    let r = f();
+    assert!(cx.impl_trait_bounds.borrow().is_empty());
+    *cx.impl_trait_bounds.borrow_mut() = old_bounds;
+    r
+}
+
+#[derive(Eq, PartialEq, Hash, Copy, Clone, Debug)]
+enum RegionTarget<'tcx> {
+    Region(Region<'tcx>),
+    RegionVid(RegionVid)
+}
+
+#[derive(Default, Debug, Clone)]
+struct RegionDeps<'tcx> {
+    larger: FxHashSet<RegionTarget<'tcx>>,
+    smaller: FxHashSet<RegionTarget<'tcx>>
+}
+
+enum SimpleBound {
+    TraitBound(Vec<PathSegment>, Vec<SimpleBound>, Vec<GenericParamDef>, hir::TraitBoundModifier),
+    Outlives(Lifetime),
+}
+
+impl From<GenericBound> for SimpleBound {
+    fn from(bound: GenericBound) -> Self {
+        match bound.clone() {
+            GenericBound::Outlives(l) => SimpleBound::Outlives(l),
+            GenericBound::TraitBound(t, mod_) => match t.trait_ {
+                Type::ResolvedPath { path, param_names, .. } => {
+                    SimpleBound::TraitBound(path.segments,
+                                            param_names
+                                                .map_or_else(|| Vec::new(), |v| v.iter()
+                                                        .map(|p| SimpleBound::from(p.clone()))
+                                                        .collect()),
+                                            t.generic_params,
+                                            mod_)
+                }
+                _ => panic!("Unexpected bound {:?}", bound),
+            }
+        }
+    }
+}