Merge branch 'master' into relnotes-1.42.0

7 files changed, 243 insertions, 250 deletions

diff --git a/src/libsyntax/ast.rs b/src/libsyntax/ast.rs
index b22406124e0..62ff4f5183a 100644
--- a/src/libsyntax/ast.rs
+++ b/src/libsyntax/ast.rs
@@ -34,7 +34,7 @@ use rustc_data_structures::thin_vec::ThinVec;
 use rustc_index::vec::Idx;
 use rustc_macros::HashStable_Generic;
 use rustc_serialize::{self, Decoder, Encoder};
-use rustc_span::source_map::{dummy_spanned, respan, Spanned};
+use rustc_span::source_map::{respan, Spanned};
 use rustc_span::symbol::{kw, sym, Symbol};
 use rustc_span::{Span, DUMMY_SP};
 
@@ -243,7 +243,7 @@ pub struct ParenthesizedArgs {
     pub inputs: Vec<P<Ty>>,
 
     /// `C`
-    pub output: FunctionRetTy,
+    pub output: FnRetTy,
 }
 
 impl ParenthesizedArgs {
@@ -429,6 +429,13 @@ pub struct Crate {
     pub module: Mod,
     pub attrs: Vec<Attribute>,
     pub span: Span,
+    /// The order of items in the HIR is unrelated to the order of
+    /// items in the AST. However, we generate proc macro harnesses
+    /// based on the AST order, and later refer to these harnesses
+    /// from the HIR. This field keeps track of the order in which
+    /// we generated proc macros harnesses, so that we can map
+    /// HIR proc macros items back to their harness items.
+    pub proc_macros: Vec<NodeId>,
 }
 
 /// Possible values inside of compile-time attribute lists.
@@ -1198,14 +1205,14 @@ pub enum ExprKind {
     /// A closure (e.g., `move |a, b, c| a + b + c`).
     ///
     /// The final span is the span of the argument block `|...|`.
-    Closure(CaptureBy, IsAsync, Movability, P<FnDecl>, P<Expr>, Span),
+    Closure(CaptureBy, Async, Movability, P<FnDecl>, P<Expr>, Span),
     /// A block (`'label: { ... }`).
     Block(P<Block>, Option<Label>),
     /// An async block (`async move { ... }`).
     ///
     /// The `NodeId` is the `NodeId` for the closure that results from
     /// desugaring an async block, just like the NodeId field in the
-    /// `IsAsync` enum. This is necessary in order to create a def for the
+    /// `Async::Yes` variant. This is necessary in order to create a def for the
     /// closure which can be used as a parent of any child defs. Defs
     /// created during lowering cannot be made the parent of any other
     /// preexisting defs.
@@ -1605,46 +1612,6 @@ pub struct FnSig {
     pub decl: P<FnDecl>,
 }
 
-/// Represents associated items.
-/// These include items in `impl` and `trait` definitions.
-#[derive(Clone, RustcEncodable, RustcDecodable, Debug)]
-pub struct AssocItem {
-    pub attrs: Vec<Attribute>,
-    pub id: NodeId,
-    pub span: Span,
-    pub vis: Visibility,
-    pub ident: Ident,
-
-    pub defaultness: Defaultness,
-    pub generics: Generics,
-    pub kind: AssocItemKind,
-    /// See `Item::tokens` for what this is.
-    pub tokens: Option<TokenStream>,
-}
-
-/// Represents various kinds of content within an `impl`.
-///
-/// The term "provided" in the variants below refers to the item having a default
-/// definition / body. Meanwhile, a "required" item lacks a definition / body.
-/// In an implementation, all items must be provided.
-/// The `Option`s below denote the bodies, where `Some(_)`
-/// means "provided" and conversely `None` means "required".
-#[derive(Clone, RustcEncodable, RustcDecodable, Debug)]
-pub enum AssocItemKind {
-    /// An associated constant, `const $ident: $ty $def?;` where `def ::= "=" $expr? ;`.
-    /// If `def` is parsed, then the associated constant is provided, and otherwise required.
-    Const(P<Ty>, Option<P<Expr>>),
-
-    /// An associated function.
-    Fn(FnSig, Option<P<Block>>),
-
-    /// An associated type.
-    TyAlias(GenericBounds, Option<P<Ty>>),
-
-    /// A macro expanding to an associated item.
-    Macro(Mac),
-}
-
 #[derive(
     Clone,
     Copy,
@@ -1863,7 +1830,7 @@ pub struct Ty {
 
 #[derive(Clone, RustcEncodable, RustcDecodable, Debug)]
 pub struct BareFnTy {
-    pub unsafety: Unsafety,
+    pub unsafety: Unsafe,
     pub ext: Extern,
     pub generic_params: Vec<GenericParam>,
     pub decl: P<FnDecl>,
@@ -2076,7 +2043,7 @@ impl Param {
 #[derive(Clone, RustcEncodable, RustcDecodable, Debug)]
 pub struct FnDecl {
     pub inputs: Vec<Param>,
-    pub output: FunctionRetTy,
+    pub output: FnRetTy,
 }
 
 impl FnDecl {
@@ -2101,77 +2068,45 @@ pub enum IsAuto {
     No,
 }
 
-#[derive(
-    Copy,
-    Clone,
-    PartialEq,
-    Eq,
-    PartialOrd,
-    Ord,
-    Hash,
-    RustcEncodable,
-    RustcDecodable,
-    Debug,
-    HashStable_Generic
-)]
-pub enum Unsafety {
-    Unsafe,
-    Normal,
-}
-
-impl Unsafety {
-    pub fn prefix_str(&self) -> &'static str {
-        match self {
-            Unsafety::Unsafe => "unsafe ",
-            Unsafety::Normal => "",
-        }
-    }
-}
-
-impl fmt::Display for Unsafety {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        fmt::Display::fmt(
-            match *self {
-                Unsafety::Normal => "normal",
-                Unsafety::Unsafe => "unsafe",
-            },
-            f,
-        )
-    }
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable, Debug)]
+#[derive(HashStable_Generic)]
+pub enum Unsafe {
+    Yes(Span),
+    No,
 }
 
 #[derive(Copy, Clone, RustcEncodable, RustcDecodable, Debug)]
-pub enum IsAsync {
-    Async { closure_id: NodeId, return_impl_trait_id: NodeId },
-    NotAsync,
+pub enum Async {
+    Yes { span: Span, closure_id: NodeId, return_impl_trait_id: NodeId },
+    No,
 }
 
-impl IsAsync {
+impl Async {
     pub fn is_async(self) -> bool {
-        if let IsAsync::Async { .. } = self { true } else { false }
+        if let Async::Yes { .. } = self { true } else { false }
     }
 
     /// In ths case this is an `async` return, the `NodeId` for the generated `impl Trait` item.
     pub fn opt_return_id(self) -> Option<NodeId> {
         match self {
-            IsAsync::Async { return_impl_trait_id, .. } => Some(return_impl_trait_id),
-            IsAsync::NotAsync => None,
+            Async::Yes { return_impl_trait_id, .. } => Some(return_impl_trait_id),
+            Async::No => None,
         }
     }
 }
 
 #[derive(Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable, Debug)]
 #[derive(HashStable_Generic)]
-pub enum Constness {
-    Const,
-    NotConst,
+pub enum Const {
+    Yes(Span),
+    No,
 }
 
 /// Item defaultness.
 /// For details see the [RFC #2532](https://github.com/rust-lang/rfcs/pull/2532).
 #[derive(Copy, Clone, PartialEq, RustcEncodable, RustcDecodable, Debug, HashStable_Generic)]
 pub enum Defaultness {
-    Default,
+    Default(Span),
     Final,
 }
 
@@ -2193,8 +2128,7 @@ impl fmt::Debug for ImplPolarity {
 }
 
 #[derive(Clone, RustcEncodable, RustcDecodable, Debug)]
-pub enum FunctionRetTy {
-    // FIXME(Centril): Rename to `FnRetTy` and in HIR also.
+pub enum FnRetTy {
     /// Returns type is not specified.
     ///
     /// Functions default to `()` and closures default to inference.
@@ -2204,11 +2138,11 @@ pub enum FunctionRetTy {
     Ty(P<Ty>),
 }
 
-impl FunctionRetTy {
+impl FnRetTy {
     pub fn span(&self) -> Span {
         match *self {
-            FunctionRetTy::Default(span) => span,
-            FunctionRetTy::Ty(ref ty) => ty.span,
+            FnRetTy::Default(span) => span,
+            FnRetTy::Ty(ref ty) => ty.span,
         }
     }
 }
@@ -2477,15 +2411,15 @@ impl VariantData {
     }
 }
 
-/// An item.
-///
-/// The name might be a dummy name in case of anonymous items.
+/// An item definition.
 #[derive(Clone, RustcEncodable, RustcDecodable, Debug)]
 pub struct Item<K = ItemKind> {
     pub attrs: Vec<Attribute>,
     pub id: NodeId,
     pub span: Span,
     pub vis: Visibility,
+    /// The name of the item.
+    /// It might be a dummy name in case of anonymous items.
     pub ident: Ident,
 
     pub kind: K,
@@ -2507,6 +2441,13 @@ impl Item {
     }
 }
 
+impl<K: IntoItemKind> Item<K> {
+    pub fn into_item(self) -> Item {
+        let Item { attrs, id, span, vis, ident, kind, tokens } = self;
+        Item { attrs, id, span, vis, ident, kind: kind.into_item_kind(), tokens }
+    }
+}
+
 /// `extern` qualifier on a function item or function type.
 #[derive(Clone, Copy, RustcEncodable, RustcDecodable, Debug)]
 pub enum Extern {
@@ -2527,9 +2468,9 @@ impl Extern {
 /// included in this struct (e.g., `async unsafe fn` or `const extern "C" fn`).
 #[derive(Clone, Copy, RustcEncodable, RustcDecodable, Debug)]
 pub struct FnHeader {
-    pub unsafety: Unsafety,
-    pub asyncness: Spanned<IsAsync>,
-    pub constness: Spanned<Constness>,
+    pub unsafety: Unsafe,
+    pub asyncness: Async,
+    pub constness: Const,
     pub ext: Extern,
 }
 
@@ -2537,9 +2478,9 @@ impl FnHeader {
     /// Does this function header have any qualifiers or is it empty?
     pub fn has_qualifiers(&self) -> bool {
         let Self { unsafety, asyncness, constness, ext } = self;
-        matches!(unsafety, Unsafety::Unsafe)
-            || asyncness.node.is_async()
-            || matches!(constness.node, Constness::Const)
+        matches!(unsafety, Unsafe::Yes(_))
+            || asyncness.is_async()
+            || matches!(constness, Const::Yes(_))
             || !matches!(ext, Extern::None)
     }
 }
@@ -2547,9 +2488,9 @@ impl FnHeader {
 impl Default for FnHeader {
     fn default() -> FnHeader {
         FnHeader {
-            unsafety: Unsafety::Normal,
-            asyncness: dummy_spanned(IsAsync::NotAsync),
-            constness: dummy_spanned(Constness::NotConst),
+            unsafety: Unsafe::No,
+            asyncness: Async::No,
+            constness: Const::No,
             ext: Extern::None,
         }
     }
@@ -2568,15 +2509,15 @@ pub enum ItemKind {
     /// A static item (`static`).
     ///
     /// E.g., `static FOO: i32 = 42;` or `static FOO: &'static str = "bar";`.
-    Static(P<Ty>, Mutability, P<Expr>),
+    Static(P<Ty>, Mutability, Option<P<Expr>>),
     /// A constant item (`const`).
     ///
     /// E.g., `const FOO: i32 = 42;`.
-    Const(P<Ty>, P<Expr>),
+    Const(Defaultness, P<Ty>, Option<P<Expr>>),
     /// A function declaration (`fn`).
     ///
     /// E.g., `fn foo(bar: usize) -> usize { .. }`.
-    Fn(FnSig, Generics, Option<P<Block>>),
+    Fn(Defaultness, FnSig, Generics, Option<P<Block>>),
     /// A module declaration (`mod`).
     ///
     /// E.g., `mod foo;` or `mod foo { .. }`.
@@ -2590,7 +2531,7 @@ pub enum ItemKind {
     /// A type alias (`type`).
     ///
     /// E.g., `type Foo = Bar<u8>;`.
-    TyAlias(P<Ty>, Generics),
+    TyAlias(Defaultness, Generics, GenericBounds, Option<P<Ty>>),
     /// An enum definition (`enum`).
     ///
     /// E.g., `enum Foo<A, B> { C<A>, D<B> }`.
@@ -2606,7 +2547,7 @@ pub enum ItemKind {
     /// A trait declaration (`trait`).
     ///
     /// E.g., `trait Foo { .. }`, `trait Foo<T> { .. }` or `auto trait Foo {}`.
-    Trait(IsAuto, Unsafety, Generics, GenericBounds, Vec<P<AssocItem>>),
+    Trait(IsAuto, Unsafe, Generics, GenericBounds, Vec<P<AssocItem>>),
     /// Trait alias
     ///
     /// E.g., `trait Foo = Bar + Quux;`.
@@ -2615,10 +2556,10 @@ pub enum ItemKind {
     ///
     /// E.g., `impl<A> Foo<A> { .. }` or `impl<A> Trait for Foo<A> { .. }`.
     Impl {
-        unsafety: Unsafety,
+        unsafety: Unsafe,
         polarity: ImplPolarity,
         defaultness: Defaultness,
-        constness: Constness,
+        constness: Const,
         generics: Generics,
 
         /// The trait being implemented, if any.
@@ -2637,30 +2578,41 @@ pub enum ItemKind {
 }
 
 impl ItemKind {
-    pub fn descriptive_variant(&self) -> &str {
-        match *self {
+    pub fn article(&self) -> &str {
+        use ItemKind::*;
+        match self {
+            Use(..) | Static(..) | Const(..) | Fn(..) | Mod(..) | GlobalAsm(..) | TyAlias(..)
+            | Struct(..) | Union(..) | Trait(..) | TraitAlias(..) | MacroDef(..) => "a",
+            ExternCrate(..) | ForeignMod(..) | Mac(..) | Enum(..) | Impl { .. } => "an",
+        }
+    }
+
+    pub fn descr(&self) -> &str {
+        match self {
             ItemKind::ExternCrate(..) => "extern crate",
-            ItemKind::Use(..) => "use",
+            ItemKind::Use(..) => "`use` import",
             ItemKind::Static(..) => "static item",
             ItemKind::Const(..) => "constant item",
             ItemKind::Fn(..) => "function",
             ItemKind::Mod(..) => "module",
-            ItemKind::ForeignMod(..) => "foreign module",
-            ItemKind::GlobalAsm(..) => "global asm",
+            ItemKind::ForeignMod(..) => "extern block",
+            ItemKind::GlobalAsm(..) => "global asm item",
             ItemKind::TyAlias(..) => "type alias",
             ItemKind::Enum(..) => "enum",
             ItemKind::Struct(..) => "struct",
             ItemKind::Union(..) => "union",
             ItemKind::Trait(..) => "trait",
             ItemKind::TraitAlias(..) => "trait alias",
-            ItemKind::Mac(..) | ItemKind::MacroDef(..) | ItemKind::Impl { .. } => "item",
+            ItemKind::Mac(..) => "item macro invocation",
+            ItemKind::MacroDef(..) => "macro definition",
+            ItemKind::Impl { .. } => "implementation",
         }
     }
 
     pub fn generics(&self) -> Option<&Generics> {
         match self {
-            Self::Fn(_, generics, _)
-            | Self::TyAlias(_, generics)
+            Self::Fn(_, _, generics, _)
+            | Self::TyAlias(_, generics, ..)
             | Self::Enum(_, generics)
             | Self::Struct(_, generics)
             | Self::Union(_, generics)
@@ -2672,28 +2624,58 @@ impl ItemKind {
     }
 }
 
-pub type ForeignItem = Item<ForeignItemKind>;
+pub trait IntoItemKind {
+    fn into_item_kind(self) -> ItemKind;
+}
+
+// FIXME(Centril): These definitions should be unmerged;
+// see https://github.com/rust-lang/rust/pull/69194#discussion_r379899975
+pub type ForeignItem = Item<AssocItemKind>;
+pub type ForeignItemKind = AssocItemKind;
 
-/// An item within an `extern` block.
+/// Represents associated items.
+/// These include items in `impl` and `trait` definitions.
+pub type AssocItem = Item<AssocItemKind>;
+
+/// Represents non-free item kinds.
+///
+/// The term "provided" in the variants below refers to the item having a default
+/// definition / body. Meanwhile, a "required" item lacks a definition / body.
+/// In an implementation, all items must be provided.
+/// The `Option`s below denote the bodies, where `Some(_)`
+/// means "provided" and conversely `None` means "required".
 #[derive(Clone, RustcEncodable, RustcDecodable, Debug)]
-pub enum ForeignItemKind {
-    /// A foreign function.
-    Fn(FnSig, Generics, Option<P<Block>>),
-    /// A foreign static item (`static ext: u8`).
-    Static(P<Ty>, Mutability),
-    /// A foreign type.
-    Ty,
-    /// A macro invocation.
+pub enum AssocItemKind {
+    /// A constant, `const $ident: $ty $def?;` where `def ::= "=" $expr? ;`.
+    /// If `def` is parsed, then the constant is provided, and otherwise required.
+    Const(Defaultness, P<Ty>, Option<P<Expr>>),
+    /// A static item (`static FOO: u8`).
+    Static(P<Ty>, Mutability, Option<P<Expr>>),
+    /// A function.
+    Fn(Defaultness, FnSig, Generics, Option<P<Block>>),
+    /// A type.
+    TyAlias(Defaultness, Generics, GenericBounds, Option<P<Ty>>),
+    /// A macro expanding to items.
     Macro(Mac),
 }
 
-impl ForeignItemKind {
-    pub fn descriptive_variant(&self) -> &str {
+impl AssocItemKind {
+    pub fn defaultness(&self) -> Defaultness {
         match *self {
-            ForeignItemKind::Fn(..) => "foreign function",
-            ForeignItemKind::Static(..) => "foreign static item",
-            ForeignItemKind::Ty => "foreign type",
-            ForeignItemKind::Macro(..) => "macro in foreign module",
+            Self::Const(def, ..) | Self::Fn(def, ..) | Self::TyAlias(def, ..) => def,
+            Self::Macro(..) | Self::Static(..) => Defaultness::Final,
+        }
+    }
+}
+
+impl IntoItemKind for AssocItemKind {
+    fn into_item_kind(self) -> ItemKind {
+        match self {
+            AssocItemKind::Const(a, b, c) => ItemKind::Const(a, b, c),
+            AssocItemKind::Static(a, b, c) => ItemKind::Static(a, b, c),
+            AssocItemKind::Fn(a, b, c, d) => ItemKind::Fn(a, b, c, d),
+            AssocItemKind::TyAlias(a, b, c, d) => ItemKind::TyAlias(a, b, c, d),
+            AssocItemKind::Macro(a) => ItemKind::Mac(a),
         }
     }
 }
diff --git a/src/libsyntax/attr/mod.rs b/src/libsyntax/attr/mod.rs
index 313f5269235..cd485e71378 100644
--- a/src/libsyntax/attr/mod.rs
+++ b/src/libsyntax/attr/mod.rs
@@ -722,6 +722,6 @@ macro_rules! derive_has_attrs {
 }
 
 derive_has_attrs! {
-    Item, Expr, Local, ast::ForeignItem, ast::StructField, ast::AssocItem, ast::Arm,
+    Item, Expr, Local, ast::ForeignItem, ast::StructField, ast::Arm,
     ast::Field, ast::FieldPat, ast::Variant, ast::Param, GenericParam
 }
diff --git a/src/libsyntax/mut_visit.rs b/src/libsyntax/mut_visit.rs
index 8517f223f92..b3abd4fc755 100644
--- a/src/libsyntax/mut_visit.rs
+++ b/src/libsyntax/mut_visit.rs
@@ -114,7 +114,7 @@ pub trait MutVisitor: Sized {
         noop_visit_fn_decl(d, self);
     }
 
-    fn visit_asyncness(&mut self, a: &mut IsAsync) {
+    fn visit_asyncness(&mut self, a: &mut Async) {
         noop_visit_asyncness(a, self);
     }
 
@@ -711,30 +711,17 @@ pub fn noop_visit_interpolated<T: MutVisitor>(nt: &mut token::Nonterminal, vis:
         }
         token::NtPath(path) => vis.visit_path(path),
         token::NtTT(tt) => vis.visit_tt(tt),
-        token::NtImplItem(item) => visit_clobber(item, |item| {
-            // See reasoning above.
-            vis.flat_map_impl_item(item).expect_one("expected visitor to produce exactly one item")
-        }),
-        token::NtTraitItem(item) => visit_clobber(item, |item| {
-            // See reasoning above.
-            vis.flat_map_trait_item(item).expect_one("expected visitor to produce exactly one item")
-        }),
         token::NtVis(visib) => vis.visit_vis(visib),
-        token::NtForeignItem(item) => visit_clobber(item, |item| {
-            // See reasoning above.
-            vis.flat_map_foreign_item(item)
-                .expect_one("expected visitor to produce exactly one item")
-        }),
     }
 }
 
-pub fn noop_visit_asyncness<T: MutVisitor>(asyncness: &mut IsAsync, vis: &mut T) {
+pub fn noop_visit_asyncness<T: MutVisitor>(asyncness: &mut Async, vis: &mut T) {
     match asyncness {
-        IsAsync::Async { closure_id, return_impl_trait_id } => {
+        Async::Yes { span: _, closure_id, return_impl_trait_id } => {
             vis.visit_id(closure_id);
             vis.visit_id(return_impl_trait_id);
         }
-        IsAsync::NotAsync => {}
+        Async::No => {}
     }
 }
 
@@ -744,10 +731,10 @@ pub fn noop_visit_fn_decl<T: MutVisitor>(decl: &mut P<FnDecl>, vis: &mut T) {
     noop_visit_fn_ret_ty(output, vis);
 }
 
-pub fn noop_visit_fn_ret_ty<T: MutVisitor>(fn_ret_ty: &mut FunctionRetTy, vis: &mut T) {
+pub fn noop_visit_fn_ret_ty<T: MutVisitor>(fn_ret_ty: &mut FnRetTy, vis: &mut T) {
     match fn_ret_ty {
-        FunctionRetTy::Default(span) => vis.visit_span(span),
-        FunctionRetTy::Ty(ty) => vis.visit_ty(ty),
+        FnRetTy::Default(span) => vis.visit_span(span),
+        FnRetTy::Ty(ty) => vis.visit_ty(ty),
     }
 }
 
@@ -890,15 +877,11 @@ pub fn noop_visit_item_kind<T: MutVisitor>(kind: &mut ItemKind, vis: &mut T) {
     match kind {
         ItemKind::ExternCrate(_orig_name) => {}
         ItemKind::Use(use_tree) => vis.visit_use_tree(use_tree),
-        ItemKind::Static(ty, _mut, expr) => {
-            vis.visit_ty(ty);
-            vis.visit_expr(expr);
-        }
-        ItemKind::Const(ty, expr) => {
+        ItemKind::Static(ty, _, expr) | ItemKind::Const(_, ty, expr) => {
             vis.visit_ty(ty);
-            vis.visit_expr(expr);
+            visit_opt(expr, |expr| vis.visit_expr(expr));
         }
-        ItemKind::Fn(sig, generics, body) => {
+        ItemKind::Fn(_, sig, generics, body) => {
             visit_fn_sig(sig, vis);
             vis.visit_generics(generics);
             visit_opt(body, |body| vis.visit_block(body));
@@ -906,9 +889,10 @@ pub fn noop_visit_item_kind<T: MutVisitor>(kind: &mut ItemKind, vis: &mut T) {
         ItemKind::Mod(m) => vis.visit_mod(m),
         ItemKind::ForeignMod(nm) => vis.visit_foreign_mod(nm),
         ItemKind::GlobalAsm(_ga) => {}
-        ItemKind::TyAlias(ty, generics) => {
-            vis.visit_ty(ty);
+        ItemKind::TyAlias(_, generics, bounds, ty) => {
             vis.visit_generics(generics);
+            visit_bounds(bounds, vis);
+            visit_opt(ty, |ty| vis.visit_ty(ty));
         }
         ItemKind::Enum(EnumDef { variants }, generics) => {
             variants.flat_map_in_place(|variant| vis.flat_map_variant(variant));
@@ -951,36 +935,47 @@ pub fn noop_flat_map_assoc_item<T: MutVisitor>(
     mut item: P<AssocItem>,
     visitor: &mut T,
 ) -> SmallVec<[P<AssocItem>; 1]> {
-    let AssocItem { id, ident, vis, defaultness: _, attrs, generics, kind, span, tokens: _ } =
-        item.deref_mut();
+    let Item { id, ident, vis, attrs, kind, span, tokens: _ } = item.deref_mut();
+    walk_nested_item(visitor, id, span, ident, vis, attrs, kind);
+    smallvec![item]
+}
+
+pub fn walk_nested_item(
+    visitor: &mut impl MutVisitor,
+    id: &mut NodeId,
+    span: &mut Span,
+    ident: &mut Ident,
+    vis: &mut Visibility,
+    attrs: &mut Vec<Attribute>,
+    kind: &mut AssocItemKind,
+) {
     visitor.visit_id(id);
     visitor.visit_ident(ident);
     visitor.visit_vis(vis);
     visit_attrs(attrs, visitor);
-    visitor.visit_generics(generics);
     match kind {
-        AssocItemKind::Const(ty, expr) => {
+        AssocItemKind::Const(_, ty, expr) | AssocItemKind::Static(ty, _, expr) => {
             visitor.visit_ty(ty);
             visit_opt(expr, |expr| visitor.visit_expr(expr));
         }
-        AssocItemKind::Fn(sig, body) => {
+        AssocItemKind::Fn(_, sig, generics, body) => {
+            visitor.visit_generics(generics);
             visit_fn_sig(sig, visitor);
             visit_opt(body, |body| visitor.visit_block(body));
         }
-        AssocItemKind::TyAlias(bounds, ty) => {
+        AssocItemKind::TyAlias(_, generics, bounds, ty) => {
+            visitor.visit_generics(generics);
             visit_bounds(bounds, visitor);
             visit_opt(ty, |ty| visitor.visit_ty(ty));
         }
         AssocItemKind::Macro(mac) => visitor.visit_mac(mac),
     }
     visitor.visit_span(span);
-
-    smallvec![item]
 }
 
 pub fn noop_visit_fn_header<T: MutVisitor>(header: &mut FnHeader, vis: &mut T) {
     let FnHeader { unsafety: _, asyncness, constness: _, ext: _ } = header;
-    vis.visit_asyncness(&mut asyncness.node);
+    vis.visit_asyncness(asyncness);
 }
 
 pub fn noop_visit_mod<T: MutVisitor>(Mod { inner, items, inline: _ }: &mut Mod, vis: &mut T) {
@@ -989,7 +984,7 @@ pub fn noop_visit_mod<T: MutVisitor>(Mod { inner, items, inline: _ }: &mut Mod,
 }
 
 pub fn noop_visit_crate<T: MutVisitor>(krate: &mut Crate, vis: &mut T) {
-    visit_clobber(krate, |Crate { module, attrs, span }| {
+    visit_clobber(krate, |Crate { module, attrs, span, proc_macros }| {
         let item = P(Item {
             ident: Ident::invalid(),
             attrs,
@@ -1004,11 +999,11 @@ pub fn noop_visit_crate<T: MutVisitor>(krate: &mut Crate, vis: &mut T) {
         let len = items.len();
         if len == 0 {
             let module = Mod { inner: span, items: vec![], inline: true };
-            Crate { module, attrs: vec![], span }
+            Crate { module, attrs: vec![], span, proc_macros }
         } else if len == 1 {
             let Item { attrs, span, kind, .. } = items.into_iter().next().unwrap().into_inner();
             match kind {
-                ItemKind::Mod(module) => Crate { module, attrs, span },
+                ItemKind::Mod(module) => Crate { module, attrs, span, proc_macros },
                 _ => panic!("visitor converted a module to not a module"),
             }
         } else {
@@ -1040,23 +1035,8 @@ pub fn noop_flat_map_foreign_item<T: MutVisitor>(
     mut item: P<ForeignItem>,
     visitor: &mut T,
 ) -> SmallVec<[P<ForeignItem>; 1]> {
-    let ForeignItem { ident, attrs, id, kind, vis, span, tokens: _ } = item.deref_mut();
-    visitor.visit_ident(ident);
-    visit_attrs(attrs, visitor);
-    match kind {
-        ForeignItemKind::Fn(sig, generics, body) => {
-            visit_fn_sig(sig, visitor);
-            visitor.visit_generics(generics);
-            visit_opt(body, |body| visitor.visit_block(body));
-        }
-        ForeignItemKind::Static(t, _m) => visitor.visit_ty(t),
-        ForeignItemKind::Ty => {}
-        ForeignItemKind::Macro(mac) => visitor.visit_mac(mac),
-    }
-    visitor.visit_id(id);
-    visitor.visit_span(span);
-    visitor.visit_vis(vis);
-
+    let Item { ident, attrs, id, kind, vis, span, tokens: _ } = item.deref_mut();
+    walk_nested_item(visitor, id, span, ident, vis, attrs, kind);
     smallvec![item]
 }
 
diff --git a/src/libsyntax/token.rs b/src/libsyntax/token.rs
index 3045f147698..52bf50604fb 100644
--- a/src/libsyntax/token.rs
+++ b/src/libsyntax/token.rs
@@ -270,6 +270,39 @@ impl TokenKind {
         Literal(Lit::new(kind, symbol, suffix))
     }
 
+    // An approximation to proc-macro-style single-character operators used by rustc parser.
+    // If the operator token can be broken into two tokens, the first of which is single-character,
+    // then this function performs that operation, otherwise it returns `None`.
+    pub fn break_two_token_op(&self) -> Option<(TokenKind, TokenKind)> {
+        Some(match *self {
+            Le => (Lt, Eq),
+            EqEq => (Eq, Eq),
+            Ne => (Not, Eq),
+            Ge => (Gt, Eq),
+            AndAnd => (BinOp(And), BinOp(And)),
+            OrOr => (BinOp(Or), BinOp(Or)),
+            BinOp(Shl) => (Lt, Lt),
+            BinOp(Shr) => (Gt, Gt),
+            BinOpEq(Plus) => (BinOp(Plus), Eq),
+            BinOpEq(Minus) => (BinOp(Minus), Eq),
+            BinOpEq(Star) => (BinOp(Star), Eq),
+            BinOpEq(Slash) => (BinOp(Slash), Eq),
+            BinOpEq(Percent) => (BinOp(Percent), Eq),
+            BinOpEq(Caret) => (BinOp(Caret), Eq),
+            BinOpEq(And) => (BinOp(And), Eq),
+            BinOpEq(Or) => (BinOp(Or), Eq),
+            BinOpEq(Shl) => (Lt, Le),
+            BinOpEq(Shr) => (Gt, Ge),
+            DotDot => (Dot, Dot),
+            DotDotDot => (Dot, DotDot),
+            ModSep => (Colon, Colon),
+            RArrow => (BinOp(Minus), Gt),
+            LArrow => (Lt, BinOp(Minus)),
+            FatArrow => (Eq, Gt),
+            _ => return None,
+        })
+    }
+
     /// Returns tokens that are likely to be typed accidentally instead of the current token.
     /// Enables better error recovery when the wrong token is found.
     pub fn similar_tokens(&self) -> Option<Vec<TokenKind>> {
@@ -402,12 +435,14 @@ impl Token {
 
     /// Returns `true` if the token is any literal, a minus (which can prefix a literal,
     /// for example a '-42', or one of the boolean idents).
+    ///
+    /// Keep this in sync with `Lit::from_token`.
     pub fn can_begin_literal_or_bool(&self) -> bool {
         match self.kind {
             Literal(..) | BinOp(Minus) => true,
             Ident(name, false) if name.is_bool_lit() => true,
-            Interpolated(ref nt) => match **nt {
-                NtLiteral(..) => true,
+            Interpolated(ref nt) => match &**nt {
+                NtExpr(e) | NtLiteral(e) => matches!(e.kind, ast::ExprKind::Lit(_)),
                 _ => false,
             },
             _ => false,
@@ -530,7 +565,7 @@ impl Token {
     }
 
     /// Returns `true` if the token is a non-raw identifier for which `pred` holds.
-    fn is_non_raw_ident_where(&self, pred: impl FnOnce(ast::Ident) -> bool) -> bool {
+    pub fn is_non_raw_ident_where(&self, pred: impl FnOnce(ast::Ident) -> bool) -> bool {
         match self.ident() {
             Some((id, false)) => pred(id),
             _ => false,
@@ -677,12 +712,6 @@ pub enum Nonterminal {
     NtPath(ast::Path),
     NtVis(ast::Visibility),
     NtTT(TokenTree),
-    // Used only for passing items to proc macro attributes (they are not
-    // strictly necessary for that, `Annotatable` can be converted into
-    // tokens directly, but doing that naively regresses pretty-printing).
-    NtTraitItem(P<ast::AssocItem>),
-    NtImplItem(P<ast::AssocItem>),
-    NtForeignItem(P<ast::ForeignItem>),
 }
 
 // `Nonterminal` is used a lot. Make sure it doesn't unintentionally get bigger.
@@ -720,9 +749,6 @@ impl fmt::Debug for Nonterminal {
             NtMeta(..) => f.pad("NtMeta(..)"),
             NtPath(..) => f.pad("NtPath(..)"),
             NtTT(..) => f.pad("NtTT(..)"),
-            NtImplItem(..) => f.pad("NtImplItem(..)"),
-            NtTraitItem(..) => f.pad("NtTraitItem(..)"),
-            NtForeignItem(..) => f.pad("NtForeignItem(..)"),
             NtVis(..) => f.pad("NtVis(..)"),
             NtLifetime(..) => f.pad("NtLifetime(..)"),
         }
diff --git a/src/libsyntax/util/comments.rs b/src/libsyntax/util/comments.rs
index 5a67531624d..0e42ae11fa2 100644
--- a/src/libsyntax/util/comments.rs
+++ b/src/libsyntax/util/comments.rs
@@ -189,8 +189,8 @@ fn split_block_comment_into_lines(text: &str, col: CharPos) -> Vec<String> {
 // it appears this function is called only from pprust... that's
 // probably not a good thing.
 pub fn gather_comments(sm: &SourceMap, path: FileName, src: String) -> Vec<Comment> {
-    let cm = SourceMap::new(sm.path_mapping().clone());
-    let source_file = cm.new_source_file(path, src);
+    let sm = SourceMap::new(sm.path_mapping().clone());
+    let source_file = sm.new_source_file(path, src);
     let text = (*source_file.src.as_ref().unwrap()).clone();
 
     let text: &str = text.as_str();
diff --git a/src/libsyntax/util/literal.rs b/src/libsyntax/util/literal.rs
index dd06c25b4de..0c611adc06b 100644
--- a/src/libsyntax/util/literal.rs
+++ b/src/libsyntax/util/literal.rs
@@ -188,6 +188,8 @@ impl Lit {
     }
 
     /// Converts arbitrary token into an AST literal.
+    ///
+    /// Keep this in sync with `Token::can_begin_literal_or_bool`.
     pub fn from_token(token: &Token) -> Result<Lit, LitError> {
         let lit = match token.kind {
             token::Ident(name, false) if name.is_bool_lit() => {
diff --git a/src/libsyntax/visit.rs b/src/libsyntax/visit.rs
index 73e731397c3..96149ad7947 100644
--- a/src/libsyntax/visit.rs
+++ b/src/libsyntax/visit.rs
@@ -215,7 +215,7 @@ pub trait Visitor<'ast>: Sized {
     fn visit_vis(&mut self, vis: &'ast Visibility) {
         walk_vis(self, vis)
     }
-    fn visit_fn_ret_ty(&mut self, ret_ty: &'ast FunctionRetTy) {
+    fn visit_fn_ret_ty(&mut self, ret_ty: &'ast FnRetTy) {
         walk_fn_ret_ty(self, ret_ty)
     }
     fn visit_fn_header(&mut self, _header: &'ast FnHeader) {
@@ -298,11 +298,11 @@ pub fn walk_item<'a, V: Visitor<'a>>(visitor: &mut V, item: &'a Item) {
             }
         }
         ItemKind::Use(ref use_tree) => visitor.visit_use_tree(use_tree, item.id, false),
-        ItemKind::Static(ref typ, _, ref expr) | ItemKind::Const(ref typ, ref expr) => {
+        ItemKind::Static(ref typ, _, ref expr) | ItemKind::Const(_, ref typ, ref expr) => {
             visitor.visit_ty(typ);
-            visitor.visit_expr(expr);
+            walk_list!(visitor, visit_expr, expr);
         }
-        ItemKind::Fn(ref sig, ref generics, ref body) => {
+        ItemKind::Fn(_, ref sig, ref generics, ref body) => {
             visitor.visit_generics(generics);
             let kind = FnKind::Fn(FnCtxt::Free, item.ident, sig, &item.vis, body.as_deref());
             visitor.visit_fn(kind, item.span, item.id)
@@ -312,9 +312,10 @@ pub fn walk_item<'a, V: Visitor<'a>>(visitor: &mut V, item: &'a Item) {
             walk_list!(visitor, visit_foreign_item, &foreign_module.items);
         }
         ItemKind::GlobalAsm(ref ga) => visitor.visit_global_asm(ga),
-        ItemKind::TyAlias(ref typ, ref generics) => {
-            visitor.visit_ty(typ);
-            visitor.visit_generics(generics)
+        ItemKind::TyAlias(_, ref generics, ref bounds, ref ty) => {
+            visitor.visit_generics(generics);
+            walk_list!(visitor, visit_param_bound, bounds);
+            walk_list!(visitor, visit_ty, ty);
         }
         ItemKind::Enum(ref enum_definition, ref generics) => {
             visitor.visit_generics(generics);
@@ -525,21 +526,8 @@ pub fn walk_pat<'a, V: Visitor<'a>>(visitor: &mut V, pattern: &'a Pat) {
 }
 
 pub fn walk_foreign_item<'a, V: Visitor<'a>>(visitor: &mut V, item: &'a ForeignItem) {
-    visitor.visit_vis(&item.vis);
-    visitor.visit_ident(item.ident);
-
-    match item.kind {
-        ForeignItemKind::Fn(ref sig, ref generics, ref body) => {
-            visitor.visit_generics(generics);
-            let kind = FnKind::Fn(FnCtxt::Foreign, item.ident, sig, &item.vis, body.as_deref());
-            visitor.visit_fn(kind, item.span, item.id);
-        }
-        ForeignItemKind::Static(ref typ, _) => visitor.visit_ty(typ),
-        ForeignItemKind::Ty => (),
-        ForeignItemKind::Macro(ref mac) => visitor.visit_mac(mac),
-    }
-
-    walk_list!(visitor, visit_attribute, &item.attrs);
+    let Item { id, span, ident, vis, attrs, kind, tokens: _ } = item;
+    walk_nested_item(visitor, *id, *span, *ident, vis, attrs, kind, FnCtxt::Foreign);
 }
 
 pub fn walk_global_asm<'a, V: Visitor<'a>>(_: &mut V, _: &'a GlobalAsm) {
@@ -594,8 +582,8 @@ pub fn walk_where_predicate<'a, V: Visitor<'a>>(visitor: &mut V, predicate: &'a
     }
 }
 
-pub fn walk_fn_ret_ty<'a, V: Visitor<'a>>(visitor: &mut V, ret_ty: &'a FunctionRetTy) {
-    if let FunctionRetTy::Ty(ref output_ty) = *ret_ty {
+pub fn walk_fn_ret_ty<'a, V: Visitor<'a>>(visitor: &mut V, ret_ty: &'a FnRetTy) {
+    if let FnRetTy::Ty(ref output_ty) = *ret_ty {
         visitor.visit_ty(output_ty)
     }
 }
@@ -622,24 +610,39 @@ pub fn walk_fn<'a, V: Visitor<'a>>(visitor: &mut V, kind: FnKind<'a>, _span: Spa
 }
 
 pub fn walk_assoc_item<'a, V: Visitor<'a>>(visitor: &mut V, item: &'a AssocItem, ctxt: AssocCtxt) {
-    visitor.visit_vis(&item.vis);
-    visitor.visit_ident(item.ident);
-    walk_list!(visitor, visit_attribute, &item.attrs);
-    visitor.visit_generics(&item.generics);
-    match item.kind {
-        AssocItemKind::Const(ref ty, ref expr) => {
+    let Item { id, span, ident, vis, attrs, kind, tokens: _ } = item;
+    walk_nested_item(visitor, *id, *span, *ident, vis, attrs, kind, FnCtxt::Assoc(ctxt));
+}
+
+fn walk_nested_item<'a, V: Visitor<'a>>(
+    visitor: &mut V,
+    id: NodeId,
+    span: Span,
+    ident: Ident,
+    vis: &'a Visibility,
+    attrs: &'a [Attribute],
+    kind: &'a AssocItemKind,
+    ctxt: FnCtxt,
+) {
+    visitor.visit_vis(vis);
+    visitor.visit_ident(ident);
+    walk_list!(visitor, visit_attribute, attrs);
+    match kind {
+        AssocItemKind::Const(_, ty, expr) | AssocItemKind::Static(ty, _, expr) => {
             visitor.visit_ty(ty);
             walk_list!(visitor, visit_expr, expr);
         }
-        AssocItemKind::Fn(ref sig, ref body) => {
-            let kind = FnKind::Fn(FnCtxt::Assoc(ctxt), item.ident, sig, &item.vis, body.as_deref());
-            visitor.visit_fn(kind, item.span, item.id);
+        AssocItemKind::Fn(_, sig, generics, body) => {
+            visitor.visit_generics(generics);
+            let kind = FnKind::Fn(ctxt, ident, sig, vis, body.as_deref());
+            visitor.visit_fn(kind, span, id);
         }
-        AssocItemKind::TyAlias(ref bounds, ref ty) => {
+        AssocItemKind::TyAlias(_, generics, bounds, ty) => {
+            visitor.visit_generics(generics);
             walk_list!(visitor, visit_param_bound, bounds);
             walk_list!(visitor, visit_ty, ty);
         }
-        AssocItemKind::Macro(ref mac) => {
+        AssocItemKind::Macro(mac) => {
             visitor.visit_mac(mac);
         }
     }