Merging upstream version 1.67.1+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

30 files changed, 1671 insertions, 1725 deletions

diff --git a/compiler/rustc_ast/Cargo.toml b/compiler/rustc_ast/Cargo.toml
index fcbf96818..9253b7e68 100644
--- a/compiler/rustc_ast/Cargo.toml
+++ b/compiler/rustc_ast/Cargo.toml
@@ -14,5 +14,5 @@ rustc_macros = { path = "../rustc_macros" }
 rustc_serialize = { path = "../rustc_serialize" }
 rustc_span = { path = "../rustc_span" }
 smallvec = { version = "1.8.1", features = ["union", "may_dangle"] }
-thin-vec = "0.2.8"
+thin-vec = "0.2.9"
 tracing = "0.1"
diff --git a/compiler/rustc_ast/src/ast.rs b/compiler/rustc_ast/src/ast.rs
index 4ef43735a..4d80f904a 100644
--- a/compiler/rustc_ast/src/ast.rs
+++ b/compiler/rustc_ast/src/ast.rs
@@ -13,7 +13,7 @@
 //! - [`FnDecl`], [`FnHeader`] and [`Param`]: Metadata associated with a function declaration.
 //! - [`Generics`], [`GenericParam`], [`WhereClause`]: Metadata associated with generic parameters.
 //! - [`EnumDef`] and [`Variant`]: Enum declaration.
-//! - [`Lit`] and [`LitKind`]: Literal expressions.
+//! - [`MetaItemLit`] and [`LitKind`]: Literal expressions.
 //! - [`MacroDef`], [`MacStmtStyle`], [`MacCall`], [`MacDelimiter`]: Macro definition and invocation.
 //! - [`Attribute`]: Metadata associated with item.
 //! - [`UnOp`], [`BinOp`], and [`BinOpKind`]: Unary and binary operators.
@@ -36,7 +36,7 @@ use rustc_span::{Span, DUMMY_SP};
 use std::convert::TryFrom;
 use std::fmt;
 use std::mem;
-use thin_vec::ThinVec;
+use thin_vec::{thin_vec, ThinVec};
 
 /// A "Label" is an identifier of some point in sources,
 /// e.g. in the following code:
@@ -90,7 +90,7 @@ pub struct Path {
     pub span: Span,
     /// The segments in the path: the things separated by `::`.
     /// Global paths begin with `kw::PathRoot`.
-    pub segments: Vec<PathSegment>,
+    pub segments: ThinVec<PathSegment>,
     pub tokens: Option<LazyAttrTokenStream>,
 }
 
@@ -111,10 +111,10 @@ impl<CTX: rustc_span::HashStableContext> HashStable<CTX> for Path {
 }
 
 impl Path {
-    // Convert a span and an identifier to the corresponding
-    // one-segment path.
+    /// Convert a span and an identifier to the corresponding
+    /// one-segment path.
     pub fn from_ident(ident: Ident) -> Path {
-        Path { segments: vec![PathSegment::from_ident(ident)], span: ident.span, tokens: None }
+        Path { segments: thin_vec![PathSegment::from_ident(ident)], span: ident.span, tokens: None }
     }
 
     pub fn is_global(&self) -> bool {
@@ -175,9 +175,9 @@ impl GenericArgs {
     }
 
     pub fn span(&self) -> Span {
-        match *self {
-            AngleBracketed(ref data) => data.span,
-            Parenthesized(ref data) => data.span,
+        match self {
+            AngleBracketed(data) => data.span,
+            Parenthesized(data) => data.span,
         }
     }
 }
@@ -312,8 +312,8 @@ pub enum GenericBound {
 impl GenericBound {
     pub fn span(&self) -> Span {
         match self {
-            GenericBound::Trait(ref t, ..) => t.span,
-            GenericBound::Outlives(ref l) => l.ident.span,
+            GenericBound::Trait(t, ..) => t.span,
+            GenericBound::Outlives(l) => l.ident.span,
         }
     }
 }
@@ -392,15 +392,7 @@ pub struct Generics {
 impl Default for Generics {
     /// Creates an instance of `Generics`.
     fn default() -> Generics {
-        Generics {
-            params: Vec::new(),
-            where_clause: WhereClause {
-                has_where_token: false,
-                predicates: Vec::new(),
-                span: DUMMY_SP,
-            },
-            span: DUMMY_SP,
-        }
+        Generics { params: Vec::new(), where_clause: Default::default(), span: DUMMY_SP }
     }
 }
 
@@ -415,6 +407,12 @@ pub struct WhereClause {
     pub span: Span,
 }
 
+impl Default for WhereClause {
+    fn default() -> WhereClause {
+        WhereClause { has_where_token: false, predicates: Vec::new(), span: DUMMY_SP }
+    }
+}
+
 /// A single predicate in a where-clause.
 #[derive(Clone, Encodable, Decodable, Debug)]
 pub enum WherePredicate {
@@ -481,20 +479,10 @@ pub struct Crate {
     pub is_placeholder: bool,
 }
 
-/// Possible values inside of compile-time attribute lists.
-///
-/// E.g., the '..' in `#[name(..)]`.
-#[derive(Clone, Encodable, Decodable, Debug, HashStable_Generic)]
-pub enum NestedMetaItem {
-    /// A full MetaItem, for recursive meta items.
-    MetaItem(MetaItem),
-    /// A literal.
-    ///
-    /// E.g., `"foo"`, `64`, `true`.
-    Literal(Lit),
-}
-
-/// A spanned compile-time attribute item.
+/// A semantic representation of a meta item. A meta item is a slightly
+/// restricted form of an attribute -- it can only contain expressions in
+/// certain leaf positions, rather than arbitrary token streams -- that is used
+/// for most built-in attributes.
 ///
 /// E.g., `#[test]`, `#[derive(..)]`, `#[rustfmt::skip]` or `#[feature = "foo"]`.
 #[derive(Clone, Encodable, Decodable, Debug, HashStable_Generic)]
@@ -504,23 +492,37 @@ pub struct MetaItem {
     pub span: Span,
 }
 
-/// A compile-time attribute item.
-///
-/// E.g., `#[test]`, `#[derive(..)]` or `#[feature = "foo"]`.
+/// The meta item kind, containing the data after the initial path.
 #[derive(Clone, Encodable, Decodable, Debug, HashStable_Generic)]
 pub enum MetaItemKind {
     /// Word meta item.
     ///
-    /// E.g., `test` as in `#[test]`.
+    /// E.g., `#[test]`, which lacks any arguments after `test`.
     Word,
+
     /// List meta item.
     ///
-    /// E.g., `derive(..)` as in `#[derive(..)]`.
+    /// E.g., `#[derive(..)]`, where the field represents the `..`.
     List(Vec<NestedMetaItem>),
+
     /// Name value meta item.
     ///
-    /// E.g., `feature = "foo"` as in `#[feature = "foo"]`.
-    NameValue(Lit),
+    /// E.g., `#[feature = "foo"]`, where the field represents the `"foo"`.
+    NameValue(MetaItemLit),
+}
+
+/// Values inside meta item lists.
+///
+/// E.g., each of `Clone`, `Copy` in `#[derive(Clone, Copy)]`.
+#[derive(Clone, Encodable, Decodable, Debug, HashStable_Generic)]
+pub enum NestedMetaItem {
+    /// A full MetaItem, for recursive meta items.
+    MetaItem(MetaItem),
+
+    /// A literal.
+    ///
+    /// E.g., `"foo"`, `64`, `true`.
+    Lit(MetaItemLit),
 }
 
 /// A block (`{ .. }`).
@@ -720,10 +722,10 @@ pub enum PatKind {
 
     /// A struct or struct variant pattern (e.g., `Variant {x, y, ..}`).
     /// The `bool` is `true` in the presence of a `..`.
-    Struct(Option<QSelf>, Path, Vec<PatField>, /* recovered */ bool),
+    Struct(Option<P<QSelf>>, Path, Vec<PatField>, /* recovered */ bool),
 
     /// A tuple struct/variant pattern (`Variant(x, y, .., z)`).
-    TupleStruct(Option<QSelf>, Path, Vec<P<Pat>>),
+    TupleStruct(Option<P<QSelf>>, Path, Vec<P<Pat>>),
 
     /// An or-pattern `A | B | C`.
     /// Invariant: `pats.len() >= 2`.
@@ -733,7 +735,7 @@ pub enum PatKind {
     /// Unqualified path patterns `A::B::C` can legally refer to variants, structs, constants
     /// or associated constants. Qualified path patterns `<A>::B::C`/`<A as Trait>::B::C` can
     /// only legally refer to associated constants.
-    Path(Option<QSelf>, Path),
+    Path(Option<P<QSelf>>, Path),
 
     /// A tuple pattern (`(a, b)`).
     Tuple(Vec<P<Pat>>),
@@ -777,8 +779,9 @@ pub enum PatKind {
 #[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, Copy)]
 #[derive(HashStable_Generic, Encodable, Decodable)]
 pub enum Mutability {
-    Mut,
+    // N.B. Order is deliberate, so that Not < Mut
     Not,
+    Mut,
 }
 
 impl Mutability {
@@ -789,12 +792,39 @@ impl Mutability {
         }
     }
 
-    pub fn prefix_str(&self) -> &'static str {
+    /// Returns `""` (empty string) or `"mut "` depending on the mutability.
+    pub fn prefix_str(self) -> &'static str {
         match self {
             Mutability::Mut => "mut ",
             Mutability::Not => "",
         }
     }
+
+    /// Returns `"&"` or `"&mut "` depending on the mutability.
+    pub fn ref_prefix_str(self) -> &'static str {
+        match self {
+            Mutability::Not => "&",
+            Mutability::Mut => "&mut ",
+        }
+    }
+
+    /// Returns `""` (empty string) or `"mutably "` depending on the mutability.
+    pub fn mutably_str(self) -> &'static str {
+        match self {
+            Mutability::Not => "",
+            Mutability::Mut => "mutably ",
+        }
+    }
+
+    /// Return `true` if self is mutable
+    pub fn is_mut(self) -> bool {
+        matches!(self, Self::Mut)
+    }
+
+    /// Return `true` if self is **not** mutable
+    pub fn is_not(self) -> bool {
+        matches!(self, Self::Not)
+    }
 }
 
 /// The kind of borrow in an `AddrOf` expression,
@@ -1117,23 +1147,23 @@ impl Expr {
     /// If this is not the case, name resolution does not resolve `N` when using
     /// `min_const_generics` as more complex expressions are not supported.
     pub fn is_potential_trivial_const_param(&self) -> bool {
-        let this = if let ExprKind::Block(ref block, None) = self.kind {
-            if block.stmts.len() == 1 {
-                if let StmtKind::Expr(ref expr) = block.stmts[0].kind { expr } else { self }
-            } else {
-                self
-            }
+        let this = if let ExprKind::Block(block, None) = &self.kind
+            && block.stmts.len() == 1
+            && let StmtKind::Expr(expr) = &block.stmts[0].kind
+        {
+            expr
         } else {
             self
         };
 
-        if let ExprKind::Path(None, ref path) = this.kind {
-            if path.segments.len() == 1 && path.segments[0].args.is_none() {
-                return true;
-            }
+        if let ExprKind::Path(None, path) = &this.kind
+            && path.segments.len() == 1
+            && path.segments[0].args.is_none()
+        {
+            true
+        } else {
+            false
         }
-
-        false
     }
 
     pub fn to_bound(&self) -> Option<GenericBound> {
@@ -1149,7 +1179,7 @@ impl Expr {
     pub fn peel_parens(&self) -> &Expr {
         let mut expr = self;
         while let ExprKind::Paren(inner) = &expr.kind {
-            expr = &inner;
+            expr = inner;
         }
         expr
     }
@@ -1208,7 +1238,7 @@ impl Expr {
             ExprKind::Tup(_) => ExprPrecedence::Tup,
             ExprKind::Binary(op, ..) => ExprPrecedence::Binary(op.node),
             ExprKind::Unary(..) => ExprPrecedence::Unary,
-            ExprKind::Lit(_) => ExprPrecedence::Lit,
+            ExprKind::Lit(_) | ExprKind::IncludedBytes(..) => ExprPrecedence::Lit,
             ExprKind::Type(..) | ExprKind::Cast(..) => ExprPrecedence::Cast,
             ExprKind::Let(..) => ExprPrecedence::Let,
             ExprKind::If(..) => ExprPrecedence::If,
@@ -1257,7 +1287,7 @@ impl Expr {
         )
     }
 
-    // To a first-order approximation, is this a pattern
+    /// To a first-order approximation, is this a pattern?
     pub fn is_approximately_pattern(&self) -> bool {
         match &self.peel_parens().kind {
             ExprKind::Box(_)
@@ -1274,6 +1304,20 @@ impl Expr {
     }
 }
 
+#[derive(Clone, Encodable, Decodable, Debug)]
+pub struct Closure {
+    pub binder: ClosureBinder,
+    pub capture_clause: CaptureBy,
+    pub asyncness: Async,
+    pub movability: Movability,
+    pub fn_decl: P<FnDecl>,
+    pub body: P<Expr>,
+    /// The span of the declaration block: 'move |...| -> ...'
+    pub fn_decl_span: Span,
+    /// The span of the argument block `|...|`
+    pub fn_arg_span: Span,
+}
+
 /// Limit types of a range (inclusive or exclusive)
 #[derive(Copy, Clone, PartialEq, Encodable, Decodable, Debug)]
 pub enum RangeLimits {
@@ -1283,6 +1327,20 @@ pub enum RangeLimits {
     Closed,
 }
 
+/// A method call (e.g. `x.foo::<Bar, Baz>(a, b, c)`).
+#[derive(Clone, Encodable, Decodable, Debug)]
+pub struct MethodCall {
+    /// The method name and its generic arguments, e.g. `foo::<Bar, Baz>`.
+    pub seg: PathSegment,
+    /// The receiver, e.g. `x`.
+    pub receiver: P<Expr>,
+    /// The arguments, e.g. `a, b, c`.
+    pub args: Vec<P<Expr>>,
+    /// The span of the function, without the dot and receiver e.g. `foo::<Bar,
+    /// Baz>(a, b, c)`.
+    pub span: Span,
+}
+
 #[derive(Clone, Encodable, Decodable, Debug)]
 pub enum StructRest {
     /// `..x`.
@@ -1295,7 +1353,7 @@ pub enum StructRest {
 
 #[derive(Clone, Encodable, Decodable, Debug)]
 pub struct StructExpr {
-    pub qself: Option<QSelf>,
+    pub qself: Option<P<QSelf>>,
     pub path: Path,
     pub fields: Vec<ExprField>,
     pub rest: StructRest,
@@ -1316,17 +1374,8 @@ pub enum ExprKind {
     /// This also represents calling the constructor of
     /// tuple-like ADTs such as tuple structs and enum variants.
     Call(P<Expr>, Vec<P<Expr>>),
-    /// A method call (`x.foo::<'static, Bar, Baz>(a, b, c, d)`)
-    ///
-    /// The `PathSegment` represents the method name and its generic arguments
-    /// (within the angle brackets).
-    /// The standalone `Expr` is the receiver expression.
-    /// The vector of `Expr` is the arguments.
-    /// `x.foo::<Bar, Baz>(a, b, c, d)` is represented as
-    /// `ExprKind::MethodCall(PathSegment { foo, [Bar, Baz] }, x, [a, b, c, d])`.
-    /// This `Span` is the span of the function, without the dot and receiver
-    /// (e.g. `foo(a, b)` in `x.foo(a, b)`
-    MethodCall(PathSegment, P<Expr>, Vec<P<Expr>>, Span),
+    /// A method call (e.g. `x.foo::<Bar, Baz>(a, b, c)`).
+    MethodCall(Box<MethodCall>),
     /// A tuple (e.g., `(a, b, c, d)`).
     Tup(Vec<P<Expr>>),
     /// A binary operation (e.g., `a + b`, `a * b`).
@@ -1334,7 +1383,7 @@ pub enum ExprKind {
     /// A unary operation (e.g., `!x`, `*x`).
     Unary(UnOp, P<Expr>),
     /// A literal (e.g., `1`, `"foo"`).
-    Lit(Lit),
+    Lit(token::Lit),
     /// A cast (e.g., `foo as f64`).
     Cast(P<Expr>, P<Ty>),
     /// A type ascription (e.g., `42: usize`).
@@ -1361,13 +1410,11 @@ pub enum ExprKind {
     /// Conditionless loop (can be exited with `break`, `continue`, or `return`).
     ///
     /// `'label: loop { block }`
-    Loop(P<Block>, Option<Label>),
+    Loop(P<Block>, Option<Label>, Span),
     /// A `match` block.
     Match(P<Expr>, Vec<Arm>),
     /// A closure (e.g., `move |a, b, c| a + b + c`).
-    ///
-    /// The final span is the span of the argument block `|...|`.
-    Closure(ClosureBinder, CaptureBy, Async, Movability, P<FnDecl>, P<Expr>, Span),
+    Closure(Box<Closure>),
     /// A block (`'label: { ... }`).
     Block(P<Block>, Option<Label>),
     /// An async block (`async move { ... }`).
@@ -1405,7 +1452,7 @@ pub enum ExprKind {
     /// parameters (e.g., `foo::bar::<baz>`).
     ///
     /// Optionally "qualified" (e.g., `<Vec<T> as SomeTrait>::SomeType`).
-    Path(Option<QSelf>, Path),
+    Path(Option<P<QSelf>>, Path),
 
     /// A referencing operation (`&a`, `&mut a`, `&raw const a` or `&raw mut a`).
     AddrOf(BorrowKind, Mutability, P<Expr>),
@@ -1446,6 +1493,12 @@ pub enum ExprKind {
     /// with an optional value to be returned.
     Yeet(Option<P<Expr>>),
 
+    /// Bytes included via `include_bytes!`
+    /// Added for optimization purposes to avoid the need to escape
+    /// large binary blobs - should always behave like [`ExprKind::Lit`]
+    /// with a `ByteStr` literal.
+    IncludedBytes(Lrc<[u8]>),
+
     /// Placeholder for an expression that wasn't syntactically well formed in some way.
     Err,
 }
@@ -1525,55 +1578,48 @@ pub enum ClosureBinder {
 #[derive(Clone, Encodable, Decodable, Debug)]
 pub struct MacCall {
     pub path: Path,
-    pub args: P<MacArgs>,
+    pub args: P<DelimArgs>,
     pub prior_type_ascription: Option<(Span, bool)>,
 }
 
 impl MacCall {
     pub fn span(&self) -> Span {
-        self.path.span.to(self.args.span().unwrap_or(self.path.span))
+        self.path.span.to(self.args.dspan.entire())
     }
 }
 
-/// Arguments passed to an attribute or a function-like macro.
+/// Arguments passed to an attribute macro.
 #[derive(Clone, Encodable, Decodable, Debug)]
-pub enum MacArgs {
-    /// No arguments - `#[attr]`.
+pub enum AttrArgs {
+    /// No arguments: `#[attr]`.
     Empty,
-    /// Delimited arguments - `#[attr()/[]/{}]` or `mac!()/[]/{}`.
-    Delimited(DelimSpan, MacDelimiter, TokenStream),
-    /// Arguments of a key-value attribute - `#[attr = "value"]`.
+    /// Delimited arguments: `#[attr()/[]/{}]`.
+    Delimited(DelimArgs),
+    /// Arguments of a key-value attribute: `#[attr = "value"]`.
     Eq(
         /// Span of the `=` token.
         Span,
         /// The "value".
-        MacArgsEq,
+        AttrArgsEq,
     ),
 }
 
-// The RHS of a `MacArgs::Eq` starts out as an expression. Once macro expansion
-// is completed, all cases end up either as a literal, which is the form used
-// after lowering to HIR, or as an error.
+// The RHS of an `AttrArgs::Eq` starts out as an expression. Once macro
+// expansion is completed, all cases end up either as a meta item literal,
+// which is the form used after lowering to HIR, or as an error.
 #[derive(Clone, Encodable, Decodable, Debug)]
-pub enum MacArgsEq {
+pub enum AttrArgsEq {
     Ast(P<Expr>),
-    Hir(Lit),
+    Hir(MetaItemLit),
 }
 
-impl MacArgs {
-    pub fn delim(&self) -> Option<Delimiter> {
-        match self {
-            MacArgs::Delimited(_, delim, _) => Some(delim.to_token()),
-            MacArgs::Empty | MacArgs::Eq(..) => None,
-        }
-    }
-
+impl AttrArgs {
     pub fn span(&self) -> Option<Span> {
         match self {
-            MacArgs::Empty => None,
-            MacArgs::Delimited(dspan, ..) => Some(dspan.entire()),
-            MacArgs::Eq(eq_span, MacArgsEq::Ast(expr)) => Some(eq_span.to(expr.span)),
-            MacArgs::Eq(_, MacArgsEq::Hir(lit)) => {
+            AttrArgs::Empty => None,
+            AttrArgs::Delimited(args) => Some(args.dspan.entire()),
+            AttrArgs::Eq(eq_span, AttrArgsEq::Ast(expr)) => Some(eq_span.to(expr.span)),
+            AttrArgs::Eq(_, AttrArgsEq::Hir(lit)) => {
                 unreachable!("in literal form when getting span: {:?}", lit);
             }
         }
@@ -1583,39 +1629,29 @@ impl MacArgs {
     /// Proc macros see these tokens, for example.
     pub fn inner_tokens(&self) -> TokenStream {
         match self {
-            MacArgs::Empty => TokenStream::default(),
-            MacArgs::Delimited(.., tokens) => tokens.clone(),
-            MacArgs::Eq(_, MacArgsEq::Ast(expr)) => TokenStream::from_ast(expr),
-            MacArgs::Eq(_, MacArgsEq::Hir(lit)) => {
+            AttrArgs::Empty => TokenStream::default(),
+            AttrArgs::Delimited(args) => args.tokens.clone(),
+            AttrArgs::Eq(_, AttrArgsEq::Ast(expr)) => TokenStream::from_ast(expr),
+            AttrArgs::Eq(_, AttrArgsEq::Hir(lit)) => {
                 unreachable!("in literal form when getting inner tokens: {:?}", lit)
             }
         }
     }
-
-    /// Whether a macro with these arguments needs a semicolon
-    /// when used as a standalone item or statement.
-    pub fn need_semicolon(&self) -> bool {
-        !matches!(self, MacArgs::Delimited(_, MacDelimiter::Brace, _))
-    }
 }
 
-impl<CTX> HashStable<CTX> for MacArgs
+impl<CTX> HashStable<CTX> for AttrArgs
 where
     CTX: crate::HashStableContext,
 {
     fn hash_stable(&self, ctx: &mut CTX, hasher: &mut StableHasher) {
         mem::discriminant(self).hash_stable(ctx, hasher);
         match self {
-            MacArgs::Empty => {}
-            MacArgs::Delimited(dspan, delim, tokens) => {
-                dspan.hash_stable(ctx, hasher);
-                delim.hash_stable(ctx, hasher);
-                tokens.hash_stable(ctx, hasher);
-            }
-            MacArgs::Eq(_eq_span, MacArgsEq::Ast(expr)) => {
+            AttrArgs::Empty => {}
+            AttrArgs::Delimited(args) => args.hash_stable(ctx, hasher),
+            AttrArgs::Eq(_eq_span, AttrArgsEq::Ast(expr)) => {
                 unreachable!("hash_stable {:?}", expr);
             }
-            MacArgs::Eq(eq_span, MacArgsEq::Hir(lit)) => {
+            AttrArgs::Eq(eq_span, AttrArgsEq::Hir(lit)) => {
                 eq_span.hash_stable(ctx, hasher);
                 lit.hash_stable(ctx, hasher);
             }
@@ -1623,6 +1659,34 @@ where
     }
 }
 
+/// Delimited arguments, as used in `#[attr()/[]/{}]` or `mac!()/[]/{}`.
+#[derive(Clone, Encodable, Decodable, Debug)]
+pub struct DelimArgs {
+    pub dspan: DelimSpan,
+    pub delim: MacDelimiter,
+    pub tokens: TokenStream,
+}
+
+impl DelimArgs {
+    /// Whether a macro with these arguments needs a semicolon
+    /// when used as a standalone item or statement.
+    pub fn need_semicolon(&self) -> bool {
+        !matches!(self, DelimArgs { delim: MacDelimiter::Brace, .. })
+    }
+}
+
+impl<CTX> HashStable<CTX> for DelimArgs
+where
+    CTX: crate::HashStableContext,
+{
+    fn hash_stable(&self, ctx: &mut CTX, hasher: &mut StableHasher) {
+        let DelimArgs { dspan, delim, tokens } = self;
+        dspan.hash_stable(ctx, hasher);
+        delim.hash_stable(ctx, hasher);
+        tokens.hash_stable(ctx, hasher);
+    }
+}
+
 #[derive(Copy, Clone, PartialEq, Eq, Encodable, Decodable, Debug, HashStable_Generic)]
 pub enum MacDelimiter {
     Parenthesis,
@@ -1652,7 +1716,7 @@ impl MacDelimiter {
 /// Represents a macro definition.
 #[derive(Clone, Encodable, Decodable, Debug, HashStable_Generic)]
 pub struct MacroDef {
-    pub body: P<MacArgs>,
+    pub body: P<DelimArgs>,
     /// `true` if macro was defined with `macro_rules`.
     pub macro_rules: bool,
 }
@@ -1668,19 +1732,18 @@ pub enum StrStyle {
     Raw(u8),
 }
 
-/// An AST literal.
+/// A literal in a meta item.
 #[derive(Clone, Encodable, Decodable, Debug, HashStable_Generic)]
-pub struct Lit {
+pub struct MetaItemLit {
     /// The original literal token as written in source code.
     pub token_lit: token::Lit,
     /// The "semantic" representation of the literal lowered from the original tokens.
     /// Strings are unescaped, hexadecimal forms are eliminated, etc.
-    /// FIXME: Remove this and only create the semantic representation during lowering to HIR.
     pub kind: LitKind,
     pub span: Span,
 }
 
-/// Same as `Lit`, but restricted to string literals.
+/// Similar to `MetaItemLit`, but restricted to string literals.
 #[derive(Clone, Copy, Encodable, Decodable, Debug)]
 pub struct StrLit {
     /// The original literal token as written in source code.
@@ -1689,21 +1752,16 @@ pub struct StrLit {
     pub suffix: Option<Symbol>,
     pub span: Span,
     /// The unescaped "semantic" representation of the literal lowered from the original token.
-    /// FIXME: Remove this and only create the semantic representation during lowering to HIR.
     pub symbol_unescaped: Symbol,
 }
 
 impl StrLit {
-    pub fn as_lit(&self) -> Lit {
+    pub fn as_token_lit(&self) -> token::Lit {
         let token_kind = match self.style {
             StrStyle::Cooked => token::Str,
             StrStyle::Raw(n) => token::StrRaw(n),
         };
-        Lit {
-            token_lit: token::Lit::new(token_kind, self.symbol, self.suffix),
-            span: self.span,
-            kind: LitKind::Str(self.symbol_unescaped, self.style),
-        }
+        token::Lit::new(token_kind, self.symbol, self.suffix)
     }
 }
 
@@ -1729,9 +1787,12 @@ pub enum LitFloatType {
     Unsuffixed,
 }
 
-/// Literal kind.
+/// This type is used within both `ast::MetaItemLit` and `hir::Lit`.
 ///
-/// E.g., `"foo"`, `42`, `12.34`, or `bool`.
+/// Note that the entire literal (including the suffix) is considered when
+/// deciding the `LitKind`. This means that float literals like `1f32` are
+/// classified by this type as `Float`. This is different to `token::LitKind`
+/// which does *not* consider the suffix.
 #[derive(Clone, Encodable, Decodable, Debug, Hash, Eq, PartialEq, HashStable_Generic)]
 pub enum LitKind {
     /// A string literal (`"foo"`). The symbol is unescaped, and so may differ
@@ -1745,10 +1806,11 @@ pub enum LitKind {
     Char(char),
     /// An integer literal (`1`).
     Int(u128, LitIntType),
-    /// A float literal (`1f64` or `1E10f64`). Stored as a symbol rather than
-    /// `f64` so that `LitKind` can impl `Eq` and `Hash`.
+    /// A float literal (`1.0`, `1f64` or `1E10f64`). The pre-suffix part is
+    /// stored as a symbol rather than `f64` so that `LitKind` can impl `Eq`
+    /// and `Hash`.
     Float(Symbol, LitFloatType),
-    /// A boolean literal.
+    /// A boolean literal (`true`, `false`).
     Bool(bool),
     /// Placeholder for a literal that wasn't well-formed in some way.
     Err,
@@ -1967,7 +2029,7 @@ impl Ty {
     pub fn peel_refs(&self) -> &Self {
         let mut final_ty = self;
         while let TyKind::Rptr(_, MutTy { ty, .. }) = &final_ty.kind {
-            final_ty = &ty;
+            final_ty = ty;
         }
         final_ty
     }
@@ -2004,7 +2066,7 @@ pub enum TyKind {
     /// "qualified", e.g., `<Vec<T> as SomeTrait>::SomeType`.
     ///
     /// Type parameters are stored in the `Path` itself.
-    Path(Option<QSelf>, Path),
+    Path(Option<P<QSelf>>, Path),
     /// A trait object type `Bound1 + Bound2 + Bound3`
     /// where `Bound` is a trait or a lifetime.
     TraitObject(GenericBounds, TraitObjectSyntax),
@@ -2136,7 +2198,7 @@ impl InlineAsmTemplatePiece {
 #[derive(Clone, Encodable, Decodable, Debug)]
 pub struct InlineAsmSym {
     pub id: NodeId,
-    pub qself: Option<QSelf>,
+    pub qself: Option<P<QSelf>>,
     pub path: Path,
 }
 
@@ -2376,9 +2438,9 @@ pub enum FnRetTy {
 
 impl FnRetTy {
     pub fn span(&self) -> Span {
-        match *self {
-            FnRetTy::Default(span) => span,
-            FnRetTy::Ty(ref ty) => ty.span,
+        match self {
+            &FnRetTy::Default(span) => span,
+            FnRetTy::Ty(ty) => ty.span,
         }
     }
 }
@@ -2457,10 +2519,7 @@ pub struct Variant {
 #[derive(Clone, Encodable, Decodable, Debug)]
 pub enum UseTreeKind {
     /// `use prefix` or `use prefix as rename`
-    ///
-    /// The extra `NodeId`s are for HIR lowering, when additional statements are created for each
-    /// namespace.
-    Simple(Option<Ident>, NodeId, NodeId),
+    Simple(Option<Ident>),
     /// `use prefix::{...}`
     Nested(Vec<(UseTree, NodeId)>),
     /// `use prefix::*`
@@ -2479,8 +2538,8 @@ pub struct UseTree {
 impl UseTree {
     pub fn ident(&self) -> Ident {
         match self.kind {
-            UseTreeKind::Simple(Some(rename), ..) => rename,
-            UseTreeKind::Simple(None, ..) => {
+            UseTreeKind::Simple(Some(rename)) => rename,
+            UseTreeKind::Simple(None) => {
                 self.prefix.segments.last().expect("empty prefix in a simple import").ident
             }
             _ => panic!("`UseTree::ident` can only be used on a simple import"),
@@ -2514,17 +2573,10 @@ impl<D: Decoder> Decodable<D> for AttrId {
     }
 }
 
-#[derive(Clone, Encodable, Decodable, Debug, HashStable_Generic)]
-pub struct AttrItem {
-    pub path: Path,
-    pub args: MacArgs,
-    pub tokens: Option<LazyAttrTokenStream>,
-}
-
 /// A list of attributes.
 pub type AttrVec = ThinVec<Attribute>;
 
-/// Metadata associated with an item.
+/// A syntax-level representation of an attribute.
 #[derive(Clone, Encodable, Decodable, Debug)]
 pub struct Attribute {
     pub kind: AttrKind,
@@ -2536,12 +2588,6 @@ pub struct Attribute {
 }
 
 #[derive(Clone, Encodable, Decodable, Debug)]
-pub struct NormalAttr {
-    pub item: AttrItem,
-    pub tokens: Option<LazyAttrTokenStream>,
-}
-
-#[derive(Clone, Encodable, Decodable, Debug)]
 pub enum AttrKind {
     /// A normal attribute.
     Normal(P<NormalAttr>),
@@ -2552,6 +2598,19 @@ pub enum AttrKind {
     DocComment(CommentKind, Symbol),
 }
 
+#[derive(Clone, Encodable, Decodable, Debug)]
+pub struct NormalAttr {
+    pub item: AttrItem,
+    pub tokens: Option<LazyAttrTokenStream>,
+}
+
+#[derive(Clone, Encodable, Decodable, Debug, HashStable_Generic)]
+pub struct AttrItem {
+    pub path: Path,
+    pub args: AttrArgs,
+    pub tokens: Option<LazyAttrTokenStream>,
+}
+
 /// `TraitRef`s appear in impls.
 ///
 /// Resolution maps each `TraitRef`'s `ref_id` to its defining trait; that's all
@@ -2640,14 +2699,14 @@ pub enum VariantData {
 impl VariantData {
     /// Return the fields of this variant.
     pub fn fields(&self) -> &[FieldDef] {
-        match *self {
-            VariantData::Struct(ref fields, ..) | VariantData::Tuple(ref fields, _) => fields,
+        match self {
+            VariantData::Struct(fields, ..) | VariantData::Tuple(fields, _) => fields,
             _ => &[],
         }
     }
 
     /// Return the `NodeId` of this variant's constructor, if it has one.
-    pub fn ctor_id(&self) -> Option<NodeId> {
+    pub fn ctor_node_id(&self) -> Option<NodeId> {
         match *self {
             VariantData::Struct(..) => None,
             VariantData::Tuple(_, id) | VariantData::Unit(id) => Some(id),
@@ -3029,28 +3088,28 @@ mod size_asserts {
     static_assert_size!(AssocItemKind, 32);
     static_assert_size!(Attribute, 32);
     static_assert_size!(Block, 48);
-    static_assert_size!(Expr, 104);
-    static_assert_size!(ExprKind, 72);
+    static_assert_size!(Expr, 72);
+    static_assert_size!(ExprKind, 40);
     static_assert_size!(Fn, 184);
     static_assert_size!(ForeignItem, 96);
     static_assert_size!(ForeignItemKind, 24);
     static_assert_size!(GenericArg, 24);
-    static_assert_size!(GenericBound, 88);
+    static_assert_size!(GenericBound, 72);
     static_assert_size!(Generics, 72);
-    static_assert_size!(Impl, 200);
+    static_assert_size!(Impl, 184);
     static_assert_size!(Item, 184);
     static_assert_size!(ItemKind, 112);
-    static_assert_size!(Lit, 48);
     static_assert_size!(LitKind, 24);
     static_assert_size!(Local, 72);
+    static_assert_size!(MetaItemLit, 48);
     static_assert_size!(Param, 40);
-    static_assert_size!(Pat, 120);
-    static_assert_size!(Path, 40);
+    static_assert_size!(Pat, 88);
+    static_assert_size!(Path, 24);
     static_assert_size!(PathSegment, 24);
-    static_assert_size!(PatKind, 96);
+    static_assert_size!(PatKind, 64);
     static_assert_size!(Stmt, 32);
     static_assert_size!(StmtKind, 16);
-    static_assert_size!(Ty, 96);
-    static_assert_size!(TyKind, 72);
+    static_assert_size!(Ty, 64);
+    static_assert_size!(TyKind, 40);
     // tidy-alphabetical-end
 }
diff --git a/compiler/rustc_ast/src/attr/mod.rs b/compiler/rustc_ast/src/attr/mod.rs
index 990f4f8f1..057cc26b5 100644
--- a/compiler/rustc_ast/src/attr/mod.rs
+++ b/compiler/rustc_ast/src/attr/mod.rs
@@ -1,35 +1,33 @@
 //! Functions dealing with attributes and meta items.
 
 use crate::ast;
-use crate::ast::{AttrId, AttrItem, AttrKind, AttrStyle, Attribute};
-use crate::ast::{Lit, LitKind};
-use crate::ast::{MacArgs, MacArgsEq, MacDelimiter, MetaItem, MetaItemKind, NestedMetaItem};
-use crate::ast::{Path, PathSegment};
+use crate::ast::{AttrArgs, AttrArgsEq, AttrId, AttrItem, AttrKind, AttrStyle, AttrVec, Attribute};
+use crate::ast::{DelimArgs, Expr, ExprKind, LitKind, MetaItemLit};
+use crate::ast::{MacDelimiter, MetaItem, MetaItemKind, NestedMetaItem, NormalAttr};
+use crate::ast::{Path, PathSegment, StrStyle, DUMMY_NODE_ID};
 use crate::ptr::P;
 use crate::token::{self, CommentKind, Delimiter, Token};
 use crate::tokenstream::{DelimSpan, Spacing, TokenTree};
 use crate::tokenstream::{LazyAttrTokenStream, TokenStream};
 use crate::util::comments;
-
 use rustc_data_structures::sync::WorkerLocal;
 use rustc_index::bit_set::GrowableBitSet;
-use rustc_span::source_map::BytePos;
 use rustc_span::symbol::{sym, Ident, Symbol};
 use rustc_span::Span;
-
 use std::cell::Cell;
 use std::iter;
 #[cfg(debug_assertions)]
 use std::ops::BitXor;
 #[cfg(debug_assertions)]
 use std::sync::atomic::{AtomicU32, Ordering};
+use thin_vec::thin_vec;
 
 pub struct MarkedAttrs(GrowableBitSet<AttrId>);
 
 impl MarkedAttrs {
-    // We have no idea how many attributes there will be, so just
-    // initiate the vectors with 0 bits. We'll grow them as necessary.
     pub fn new() -> Self {
+        // We have no idea how many attributes there will be, so just
+        // initiate the vectors with 0 bits. We'll grow them as necessary.
         MarkedAttrs(GrowableBitSet::new_empty())
     }
 
@@ -45,16 +43,16 @@ impl MarkedAttrs {
 impl NestedMetaItem {
     /// Returns the `MetaItem` if `self` is a `NestedMetaItem::MetaItem`.
     pub fn meta_item(&self) -> Option<&MetaItem> {
-        match *self {
-            NestedMetaItem::MetaItem(ref item) => Some(item),
+        match self {
+            NestedMetaItem::MetaItem(item) => Some(item),
             _ => None,
         }
     }
 
-    /// Returns the `Lit` if `self` is a `NestedMetaItem::Literal`s.
-    pub fn literal(&self) -> Option<&Lit> {
-        match *self {
-            NestedMetaItem::Literal(ref lit) => Some(lit),
+    /// Returns the `MetaItemLit` if `self` is a `NestedMetaItem::Literal`s.
+    pub fn lit(&self) -> Option<&MetaItemLit> {
+        match self {
+            NestedMetaItem::Lit(lit) => Some(lit),
             _ => None,
         }
     }
@@ -79,12 +77,12 @@ impl NestedMetaItem {
     }
 
     /// Returns a name and single literal value tuple of the `MetaItem`.
-    pub fn name_value_literal(&self) -> Option<(Symbol, &Lit)> {
+    pub fn name_value_literal(&self) -> Option<(Symbol, &MetaItemLit)> {
         self.meta_item().and_then(|meta_item| {
             meta_item.meta_item_list().and_then(|meta_item_list| {
                 if meta_item_list.len() == 1
                     && let Some(ident) = meta_item.ident()
-                    && let Some(lit) = meta_item_list[0].literal()
+                    && let Some(lit) = meta_item_list[0].lit()
                 {
                     return Some((ident.name, lit));
                 }
@@ -117,18 +115,18 @@ impl NestedMetaItem {
 impl Attribute {
     #[inline]
     pub fn has_name(&self, name: Symbol) -> bool {
-        match self.kind {
-            AttrKind::Normal(ref normal) => normal.item.path == name,
+        match &self.kind {
+            AttrKind::Normal(normal) => normal.item.path == name,
             AttrKind::DocComment(..) => false,
         }
     }
 
     /// For a single-segment attribute, returns its name; otherwise, returns `None`.
     pub fn ident(&self) -> Option<Ident> {
-        match self.kind {
-            AttrKind::Normal(ref normal) => {
-                if normal.item.path.segments.len() == 1 {
-                    Some(normal.item.path.segments[0].ident)
+        match &self.kind {
+            AttrKind::Normal(normal) => {
+                if let [ident] = &*normal.item.path.segments {
+                    Some(ident.ident)
                 } else {
                     None
                 }
@@ -141,17 +139,15 @@ impl Attribute {
     }
 
     pub fn value_str(&self) -> Option<Symbol> {
-        match self.kind {
-            AttrKind::Normal(ref normal) => {
-                normal.item.meta_kind().and_then(|kind| kind.value_str())
-            }
+        match &self.kind {
+            AttrKind::Normal(normal) => normal.item.meta_kind().and_then(|kind| kind.value_str()),
             AttrKind::DocComment(..) => None,
         }
     }
 
     pub fn meta_item_list(&self) -> Option<Vec<NestedMetaItem>> {
-        match self.kind {
-            AttrKind::Normal(ref normal) => match normal.item.meta_kind() {
+        match &self.kind {
+            AttrKind::Normal(normal) => match normal.item.meta_kind() {
                 Some(MetaItemKind::List(list)) => Some(list),
                 _ => None,
             },
@@ -161,7 +157,7 @@ impl Attribute {
 
     pub fn is_word(&self) -> bool {
         if let AttrKind::Normal(normal) = &self.kind {
-            matches!(normal.item.args, MacArgs::Empty)
+            matches!(normal.item.args, AttrArgs::Empty)
         } else {
             false
         }
@@ -177,10 +173,12 @@ impl MetaItem {
         self.ident().unwrap_or_else(Ident::empty).name
     }
 
-    // Example:
-    //     #[attribute(name = "value")]
-    //                 ^^^^^^^^^^^^^^
-    pub fn name_value_literal(&self) -> Option<&Lit> {
+    /// ```text
+    /// Example:
+    ///     #[attribute(name = "value")]
+    ///                 ^^^^^^^^^^^^^^
+    /// ```
+    pub fn name_value_literal(&self) -> Option<&MetaItemLit> {
         match &self.kind {
             MetaItemKind::NameValue(v) => Some(v),
             _ => None,
@@ -192,8 +190,8 @@ impl MetaItem {
     }
 
     pub fn meta_item_list(&self) -> Option<&[NestedMetaItem]> {
-        match self.kind {
-            MetaItemKind::List(ref l) => Some(&l[..]),
+        match &self.kind {
+            MetaItemKind::List(l) => Some(&**l),
             _ => None,
         }
     }
@@ -224,15 +222,11 @@ impl AttrItem {
     }
 
     pub fn meta(&self, span: Span) -> Option<MetaItem> {
-        Some(MetaItem {
-            path: self.path.clone(),
-            kind: MetaItemKind::from_mac_args(&self.args)?,
-            span,
-        })
+        Some(MetaItem { path: self.path.clone(), kind: self.meta_kind()?, span })
     }
 
     pub fn meta_kind(&self) -> Option<MetaItemKind> {
-        MetaItemKind::from_mac_args(&self.args)
+        MetaItemKind::from_attr_args(&self.args)
     }
 }
 
@@ -269,9 +263,9 @@ impl Attribute {
     /// * `#[doc = "doc"]` returns `Some("doc")`.
     /// * `#[doc(...)]` returns `None`.
     pub fn doc_str(&self) -> Option<Symbol> {
-        match self.kind {
-            AttrKind::DocComment(.., data) => Some(data),
-            AttrKind::Normal(ref normal) if normal.item.path == sym::doc => {
+        match &self.kind {
+            AttrKind::DocComment(.., data) => Some(*data),
+            AttrKind::Normal(normal) if normal.item.path == sym::doc => {
                 normal.item.meta_kind().and_then(|kind| kind.value_str())
             }
             _ => None,
@@ -283,8 +277,8 @@ impl Attribute {
     }
 
     pub fn get_normal_item(&self) -> &AttrItem {
-        match self.kind {
-            AttrKind::Normal(ref normal) => &normal.item,
+        match &self.kind {
+            AttrKind::Normal(normal) => &normal.item,
             AttrKind::DocComment(..) => panic!("unexpected doc comment"),
         }
     }
@@ -298,28 +292,28 @@ impl Attribute {
 
     /// Extracts the MetaItem from inside this Attribute.
     pub fn meta(&self) -> Option<MetaItem> {
-        match self.kind {
-            AttrKind::Normal(ref normal) => normal.item.meta(self.span),
+        match &self.kind {
+            AttrKind::Normal(normal) => normal.item.meta(self.span),
             AttrKind::DocComment(..) => None,
         }
     }
 
     pub fn meta_kind(&self) -> Option<MetaItemKind> {
-        match self.kind {
-            AttrKind::Normal(ref normal) => normal.item.meta_kind(),
+        match &self.kind {
+            AttrKind::Normal(normal) => normal.item.meta_kind(),
             AttrKind::DocComment(..) => None,
         }
     }
 
     pub fn tokens(&self) -> TokenStream {
-        match self.kind {
-            AttrKind::Normal(ref normal) => normal
+        match &self.kind {
+            AttrKind::Normal(normal) => normal
                 .tokens
                 .as_ref()
                 .unwrap_or_else(|| panic!("attribute is missing tokens: {:?}", self))
                 .to_attr_token_stream()
                 .to_tokenstream(),
-            AttrKind::DocComment(comment_kind, data) => TokenStream::new(vec![TokenTree::Token(
+            &AttrKind::DocComment(comment_kind, data) => TokenStream::new(vec![TokenTree::Token(
                 Token::new(token::DocComment(comment_kind, self.style, data), self.span),
                 Spacing::Alone,
             )]),
@@ -330,26 +324,13 @@ impl Attribute {
 /* Constructors */
 
 pub fn mk_name_value_item_str(ident: Ident, str: Symbol, str_span: Span) -> MetaItem {
-    let lit_kind = LitKind::Str(str, ast::StrStyle::Cooked);
-    mk_name_value_item(ident, lit_kind, str_span)
+    mk_name_value_item(ident, LitKind::Str(str, ast::StrStyle::Cooked), str_span)
 }
 
-pub fn mk_name_value_item(ident: Ident, lit_kind: LitKind, lit_span: Span) -> MetaItem {
-    let lit = Lit::from_lit_kind(lit_kind, lit_span);
+pub fn mk_name_value_item(ident: Ident, kind: LitKind, lit_span: Span) -> MetaItem {
+    let lit = MetaItemLit { token_lit: kind.to_token_lit(), kind, span: lit_span };
     let span = ident.span.to(lit_span);
-    MetaItem { path: Path::from_ident(ident), span, kind: MetaItemKind::NameValue(lit) }
-}
-
-pub fn mk_list_item(ident: Ident, items: Vec<NestedMetaItem>) -> MetaItem {
-    MetaItem { path: Path::from_ident(ident), span: ident.span, kind: MetaItemKind::List(items) }
-}
-
-pub fn mk_word_item(ident: Ident) -> MetaItem {
-    MetaItem { path: Path::from_ident(ident), span: ident.span, kind: MetaItemKind::Word }
-}
-
-pub fn mk_nested_word_item(ident: Ident) -> NestedMetaItem {
-    NestedMetaItem::MetaItem(mk_word_item(ident))
+    MetaItem { path: Path::from_ident(ident), kind: MetaItemKind::NameValue(lit), span }
 }
 
 pub struct AttrIdGenerator(WorkerLocal<Cell<u32>>);
@@ -393,7 +374,7 @@ pub fn mk_attr(
     g: &AttrIdGenerator,
     style: AttrStyle,
     path: Path,
-    args: MacArgs,
+    args: AttrArgs,
     span: Span,
 ) -> Attribute {
     mk_attr_from_item(g, AttrItem { path, args, tokens: None }, None, style, span)
@@ -407,21 +388,58 @@ pub fn mk_attr_from_item(
     span: Span,
 ) -> Attribute {
     Attribute {
-        kind: AttrKind::Normal(P(ast::NormalAttr { item, tokens })),
+        kind: AttrKind::Normal(P(NormalAttr { item, tokens })),
         id: g.mk_attr_id(),
         style,
         span,
     }
 }
 
-/// Returns an inner attribute with the given value and span.
-pub fn mk_attr_inner(g: &AttrIdGenerator, item: MetaItem) -> Attribute {
-    mk_attr(g, AttrStyle::Inner, item.path, item.kind.mac_args(item.span), item.span)
+pub fn mk_attr_word(g: &AttrIdGenerator, style: AttrStyle, name: Symbol, span: Span) -> Attribute {
+    let path = Path::from_ident(Ident::new(name, span));
+    let args = AttrArgs::Empty;
+    mk_attr(g, style, path, args, span)
+}
+
+pub fn mk_attr_name_value_str(
+    g: &AttrIdGenerator,
+    style: AttrStyle,
+    name: Symbol,
+    val: Symbol,
+    span: Span,
+) -> Attribute {
+    let lit = LitKind::Str(val, StrStyle::Cooked).to_token_lit();
+    let expr = P(Expr {
+        id: DUMMY_NODE_ID,
+        kind: ExprKind::Lit(lit),
+        span,
+        attrs: AttrVec::new(),
+        tokens: None,
+    });
+    let path = Path::from_ident(Ident::new(name, span));
+    let args = AttrArgs::Eq(span, AttrArgsEq::Ast(expr));
+    mk_attr(g, style, path, args, span)
 }
 
-/// Returns an outer attribute with the given value and span.
-pub fn mk_attr_outer(g: &AttrIdGenerator, item: MetaItem) -> Attribute {
-    mk_attr(g, AttrStyle::Outer, item.path, item.kind.mac_args(item.span), item.span)
+pub fn mk_attr_nested_word(
+    g: &AttrIdGenerator,
+    style: AttrStyle,
+    outer: Symbol,
+    inner: Symbol,
+    span: Span,
+) -> Attribute {
+    let inner_tokens = TokenStream::new(vec![TokenTree::Token(
+        Token::from_ast_ident(Ident::new(inner, span)),
+        Spacing::Alone,
+    )]);
+    let outer_ident = Ident::new(outer, span);
+    let path = Path::from_ident(outer_ident);
+    let attr_args = AttrArgs::Delimited(DelimArgs {
+        dspan: DelimSpan::from_single(span),
+        delim: MacDelimiter::Parenthesis,
+        tokens: inner_tokens,
+    });
+    mk_attr(g, style, path, attr_args, span)
 }
 
 pub fn mk_doc_comment(
@@ -439,23 +457,6 @@ pub fn list_contains_name(items: &[NestedMetaItem], name: Symbol) -> bool {
 }
 
 impl MetaItem {
-    fn token_trees(&self) -> Vec<TokenTree> {
-        let mut idents = vec![];
-        let mut last_pos = BytePos(0_u32);
-        for (i, segment) in self.path.segments.iter().enumerate() {
-            let is_first = i == 0;
-            if !is_first {
-                let mod_sep_span =
-                    Span::new(last_pos, segment.ident.span.lo(), segment.ident.span.ctxt(), None);
-                idents.push(TokenTree::token_alone(token::ModSep, mod_sep_span));
-            }
-            idents.push(TokenTree::Token(Token::from_ast_ident(segment.ident), Spacing::Alone));
-            last_pos = segment.ident.span.hi();
-        }
-        idents.extend(self.kind.token_trees(self.span));
-        idents
-    }
-
     fn from_tokens<I>(tokens: &mut iter::Peekable<I>) -> Option<MetaItem>
     where
         I: Iterator<Item = TokenTree>,
@@ -471,12 +472,12 @@ impl MetaItem {
                         tokens.peek()
                     {
                         tokens.next();
-                        vec![PathSegment::from_ident(Ident::new(name, span))]
+                        thin_vec![PathSegment::from_ident(Ident::new(name, span))]
                     } else {
                         break 'arm Path::from_ident(Ident::new(name, span));
                     }
                 } else {
-                    vec![PathSegment::path_root(span)]
+                    thin_vec![PathSegment::path_root(span)]
                 };
                 loop {
                     if let Some(TokenTree::Token(Token { kind: token::Ident(name, _), span }, _)) =
@@ -497,17 +498,17 @@ impl MetaItem {
                 let span = span.with_hi(segments.last().unwrap().ident.span.hi());
                 Path { span, segments, tokens: None }
             }
-            Some(TokenTree::Token(Token { kind: token::Interpolated(nt), .. }, _)) => match *nt {
-                token::Nonterminal::NtMeta(ref item) => return item.meta(item.path.span),
-                token::Nonterminal::NtPath(ref path) => (**path).clone(),
+            Some(TokenTree::Token(Token { kind: token::Interpolated(nt), .. }, _)) => match &*nt {
+                token::Nonterminal::NtMeta(item) => return item.meta(item.path.span),
+                token::Nonterminal::NtPath(path) => (**path).clone(),
                 _ => return None,
             },
             _ => return None,
         };
         let list_closing_paren_pos = tokens.peek().map(|tt| tt.span().hi());
         let kind = MetaItemKind::from_tokens(tokens)?;
-        let hi = match kind {
-            MetaItemKind::NameValue(ref lit) => lit.span.hi(),
+        let hi = match &kind {
+            MetaItemKind::NameValue(lit) => lit.span.hi(),
             MetaItemKind::List(..) => list_closing_paren_pos.unwrap_or(path.span.hi()),
             _ => path.span.hi(),
         };
@@ -519,70 +520,14 @@ impl MetaItem {
 impl MetaItemKind {
     pub fn value_str(&self) -> Option<Symbol> {
         match self {
-            MetaItemKind::NameValue(ref v) => match v.kind {
-                LitKind::Str(ref s, _) => Some(*s),
+            MetaItemKind::NameValue(v) => match v.kind {
+                LitKind::Str(s, _) => Some(s),
                 _ => None,
             },
             _ => None,
         }
     }
 
-    pub fn mac_args(&self, span: Span) -> MacArgs {
-        match self {
-            MetaItemKind::Word => MacArgs::Empty,
-            MetaItemKind::NameValue(lit) => {
-                let expr = P(ast::Expr {
-                    id: ast::DUMMY_NODE_ID,
-                    kind: ast::ExprKind::Lit(lit.clone()),
-                    span: lit.span,
-                    attrs: ast::AttrVec::new(),
-                    tokens: None,
-                });
-                MacArgs::Eq(span, MacArgsEq::Ast(expr))
-            }
-            MetaItemKind::List(list) => {
-                let mut tts = Vec::new();
-                for (i, item) in list.iter().enumerate() {
-                    if i > 0 {
-                        tts.push(TokenTree::token_alone(token::Comma, span));
-                    }
-                    tts.extend(item.token_trees())
-                }
-                MacArgs::Delimited(
-                    DelimSpan::from_single(span),
-                    MacDelimiter::Parenthesis,
-                    TokenStream::new(tts),
-                )
-            }
-        }
-    }
-
-    fn token_trees(&self, span: Span) -> Vec<TokenTree> {
-        match *self {
-            MetaItemKind::Word => vec![],
-            MetaItemKind::NameValue(ref lit) => {
-                vec![
-                    TokenTree::token_alone(token::Eq, span),
-                    TokenTree::Token(lit.to_token(), Spacing::Alone),
-                ]
-            }
-            MetaItemKind::List(ref list) => {
-                let mut tokens = Vec::new();
-                for (i, item) in list.iter().enumerate() {
-                    if i > 0 {
-                        tokens.push(TokenTree::token_alone(token::Comma, span));
-                    }
-                    tokens.extend(item.token_trees())
-                }
-                vec![TokenTree::Delimited(
-                    DelimSpan::from_single(span),
-                    Delimiter::Parenthesis,
-                    TokenStream::new(tokens),
-                )]
-            }
-        }
-    }
-
     fn list_from_tokens(tokens: TokenStream) -> Option<MetaItemKind> {
         let mut tokens = tokens.into_trees().peekable();
         let mut result = Vec::new();
@@ -605,24 +550,31 @@ impl MetaItemKind {
                 MetaItemKind::name_value_from_tokens(&mut inner_tokens.into_trees())
             }
             Some(TokenTree::Token(token, _)) => {
-                Lit::from_token(&token).ok().map(MetaItemKind::NameValue)
+                MetaItemLit::from_token(&token).map(MetaItemKind::NameValue)
             }
             _ => None,
         }
     }
 
-    fn from_mac_args(args: &MacArgs) -> Option<MetaItemKind> {
+    fn from_attr_args(args: &AttrArgs) -> Option<MetaItemKind> {
         match args {
-            MacArgs::Empty => Some(MetaItemKind::Word),
-            MacArgs::Delimited(_, MacDelimiter::Parenthesis, tokens) => {
-                MetaItemKind::list_from_tokens(tokens.clone())
-            }
-            MacArgs::Delimited(..) => None,
-            MacArgs::Eq(_, MacArgsEq::Ast(expr)) => match &expr.kind {
-                ast::ExprKind::Lit(lit) => Some(MetaItemKind::NameValue(lit.clone())),
+            AttrArgs::Empty => Some(MetaItemKind::Word),
+            AttrArgs::Delimited(DelimArgs {
+                dspan: _,
+                delim: MacDelimiter::Parenthesis,
+                tokens,
+            }) => MetaItemKind::list_from_tokens(tokens.clone()),
+            AttrArgs::Delimited(..) => None,
+            AttrArgs::Eq(_, AttrArgsEq::Ast(expr)) => match expr.kind {
+                ExprKind::Lit(token_lit) => {
+                    // Turn failures to `None`, we'll get parse errors elsewhere.
+                    MetaItemLit::from_token_lit(token_lit, expr.span)
+                        .ok()
+                        .map(|lit| MetaItemKind::NameValue(lit))
+                }
                 _ => None,
             },
-            MacArgs::Eq(_, MacArgsEq::Hir(lit)) => Some(MetaItemKind::NameValue(lit.clone())),
+            AttrArgs::Eq(_, AttrArgsEq::Hir(lit)) => Some(MetaItemKind::NameValue(lit.clone())),
         }
     }
 
@@ -647,18 +599,9 @@ impl MetaItemKind {
 
 impl NestedMetaItem {
     pub fn span(&self) -> Span {
-        match *self {
-            NestedMetaItem::MetaItem(ref item) => item.span,
-            NestedMetaItem::Literal(ref lit) => lit.span,
-        }
-    }
-
-    fn token_trees(&self) -> Vec<TokenTree> {
-        match *self {
-            NestedMetaItem::MetaItem(ref item) => item.token_trees(),
-            NestedMetaItem::Literal(ref lit) => {
-                vec![TokenTree::Token(lit.to_token(), Spacing::Alone)]
-            }
+        match self {
+            NestedMetaItem::MetaItem(item) => item.span,
+            NestedMetaItem::Lit(lit) => lit.span,
         }
     }
 
@@ -668,10 +611,10 @@ impl NestedMetaItem {
     {
         match tokens.peek() {
             Some(TokenTree::Token(token, _))
-                if let Ok(lit) = Lit::from_token(token) =>
+                if let Some(lit) = MetaItemLit::from_token(token) =>
             {
                 tokens.next();
-                return Some(NestedMetaItem::Literal(lit));
+                return Some(NestedMetaItem::Lit(lit));
             }
             Some(TokenTree::Delimited(_, Delimiter::Invisible, inner_tokens)) => {
                 let inner_tokens = inner_tokens.clone();
diff --git a/compiler/rustc_ast/src/lib.rs b/compiler/rustc_ast/src/lib.rs
index eeb7e56e2..9c1dfeb1a 100644
--- a/compiler/rustc_ast/src/lib.rs
+++ b/compiler/rustc_ast/src/lib.rs
@@ -29,6 +29,7 @@ extern crate rustc_macros;
 extern crate tracing;
 
 pub mod util {
+    pub mod case;
     pub mod classify;
     pub mod comments;
     pub mod literal;
diff --git a/compiler/rustc_ast/src/mut_visit.rs b/compiler/rustc_ast/src/mut_visit.rs
index b970e57e0..a45ee6067 100644
--- a/compiler/rustc_ast/src/mut_visit.rs
+++ b/compiler/rustc_ast/src/mut_visit.rs
@@ -194,7 +194,7 @@ pub trait MutVisitor: Sized {
         noop_visit_path(p, self);
     }
 
-    fn visit_qself(&mut self, qs: &mut Option<QSelf>) {
+    fn visit_qself(&mut self, qs: &mut Option<P<QSelf>>) {
         noop_visit_qself(qs, self);
     }
 
@@ -367,23 +367,27 @@ pub fn visit_fn_sig<T: MutVisitor>(FnSig { header, decl, span }: &mut FnSig, vis
 }
 
 // No `noop_` prefix because there isn't a corresponding method in `MutVisitor`.
-pub fn visit_mac_args<T: MutVisitor>(args: &mut MacArgs, vis: &mut T) {
+pub fn visit_attr_args<T: MutVisitor>(args: &mut AttrArgs, vis: &mut T) {
     match args {
-        MacArgs::Empty => {}
-        MacArgs::Delimited(dspan, _delim, tokens) => {
-            visit_delim_span(dspan, vis);
-            visit_tts(tokens, vis);
-        }
-        MacArgs::Eq(eq_span, MacArgsEq::Ast(expr)) => {
+        AttrArgs::Empty => {}
+        AttrArgs::Delimited(args) => visit_delim_args(args, vis),
+        AttrArgs::Eq(eq_span, AttrArgsEq::Ast(expr)) => {
             vis.visit_span(eq_span);
             vis.visit_expr(expr);
         }
-        MacArgs::Eq(_, MacArgsEq::Hir(lit)) => {
+        AttrArgs::Eq(_, AttrArgsEq::Hir(lit)) => {
             unreachable!("in literal form when visiting mac args eq: {:?}", lit)
         }
     }
 }
 
+// No `noop_` prefix because there isn't a corresponding method in `MutVisitor`.
+pub fn visit_delim_args<T: MutVisitor>(args: &mut DelimArgs, vis: &mut T) {
+    let DelimArgs { dspan, delim: _, tokens } = args;
+    visit_delim_span(dspan, vis);
+    visit_tts(tokens, vis);
+}
+
 pub fn visit_delim_span<T: MutVisitor>(dspan: &mut DelimSpan, vis: &mut T) {
     vis.visit_span(&mut dspan.open);
     vis.visit_span(&mut dspan.close);
@@ -406,11 +410,7 @@ pub fn noop_visit_use_tree<T: MutVisitor>(use_tree: &mut UseTree, vis: &mut T) {
     let UseTree { prefix, kind, span } = use_tree;
     vis.visit_path(prefix);
     match kind {
-        UseTreeKind::Simple(rename, id1, id2) => {
-            visit_opt(rename, |rename| vis.visit_ident(rename));
-            vis.visit_id(id1);
-            vis.visit_id(id2);
-        }
+        UseTreeKind::Simple(rename) => visit_opt(rename, |rename| vis.visit_ident(rename)),
         UseTreeKind::Nested(items) => {
             for (tree, id) in items {
                 vis.visit_use_tree(tree);
@@ -439,15 +439,15 @@ pub fn noop_visit_constraint<T: MutVisitor>(
 ) {
     vis.visit_id(id);
     vis.visit_ident(ident);
-    if let Some(ref mut gen_args) = gen_args {
+    if let Some(gen_args) = gen_args {
         vis.visit_generic_args(gen_args);
     }
     match kind {
-        AssocConstraintKind::Equality { ref mut term } => match term {
+        AssocConstraintKind::Equality { term } => match term {
             Term::Ty(ty) => vis.visit_ty(ty),
             Term::Const(c) => vis.visit_anon_const(c),
         },
-        AssocConstraintKind::Bound { ref mut bounds } => visit_bounds(bounds, vis),
+        AssocConstraintKind::Bound { bounds } => visit_bounds(bounds, vis),
     }
     vis.visit_span(span);
 }
@@ -529,8 +529,9 @@ pub fn noop_visit_path<T: MutVisitor>(Path { segments, span, tokens }: &mut Path
     visit_lazy_tts(tokens, vis);
 }
 
-pub fn noop_visit_qself<T: MutVisitor>(qself: &mut Option<QSelf>, vis: &mut T) {
-    visit_opt(qself, |QSelf { ty, path_span, position: _ }| {
+pub fn noop_visit_qself<T: MutVisitor>(qself: &mut Option<P<QSelf>>, vis: &mut T) {
+    visit_opt(qself, |qself| {
+        let QSelf { ty, path_span, position: _ } = &mut **qself;
         vis.visit_ty(ty);
         vis.visit_span(path_span);
     })
@@ -600,7 +601,7 @@ pub fn noop_visit_attribute<T: MutVisitor>(attr: &mut Attribute, vis: &mut T) {
             let NormalAttr { item: AttrItem { path, args, tokens }, tokens: attr_tokens } =
                 &mut **normal;
             vis.visit_path(path);
-            visit_mac_args(args, vis);
+            visit_attr_args(args, vis);
             visit_lazy_tts(tokens, vis);
             visit_lazy_tts(attr_tokens, vis);
         }
@@ -612,18 +613,18 @@ pub fn noop_visit_attribute<T: MutVisitor>(attr: &mut Attribute, vis: &mut T) {
 pub fn noop_visit_mac<T: MutVisitor>(mac: &mut MacCall, vis: &mut T) {
     let MacCall { path, args, prior_type_ascription: _ } = mac;
     vis.visit_path(path);
-    visit_mac_args(args, vis);
+    visit_delim_args(args, vis);
 }
 
 pub fn noop_visit_macro_def<T: MutVisitor>(macro_def: &mut MacroDef, vis: &mut T) {
     let MacroDef { body, macro_rules: _ } = macro_def;
-    visit_mac_args(body, vis);
+    visit_delim_args(body, vis);
 }
 
 pub fn noop_visit_meta_list_item<T: MutVisitor>(li: &mut NestedMetaItem, vis: &mut T) {
     match li {
         NestedMetaItem::MetaItem(mi) => vis.visit_meta_item(mi),
-        NestedMetaItem::Literal(_lit) => {}
+        NestedMetaItem::Lit(_lit) => {}
     }
 }
 
@@ -720,10 +721,10 @@ pub fn visit_lazy_tts<T: MutVisitor>(lazy_tts: &mut Option<LazyAttrTokenStream>,
     visit_lazy_tts_opt_mut(lazy_tts.as_mut(), vis);
 }
 
+/// Applies ident visitor if it's an ident; applies other visits to interpolated nodes.
+/// In practice the ident part is not actually used by specific visitors right now,
+/// but there's a test below checking that it works.
 // No `noop_` prefix because there isn't a corresponding method in `MutVisitor`.
-// Applies ident visitor if it's an ident; applies other visits to interpolated nodes.
-// In practice the ident part is not actually used by specific visitors right now,
-// but there's a test below checking that it works.
 pub fn visit_token<T: MutVisitor>(t: &mut Token, vis: &mut T) {
     let Token { kind, span } = t;
     match kind {
@@ -735,8 +736,7 @@ pub fn visit_token<T: MutVisitor>(t: &mut Token, vis: &mut T) {
             return; // Avoid visiting the span for the second time.
         }
         token::Interpolated(nt) => {
-            let mut nt = Lrc::make_mut(nt);
-            visit_nonterminal(&mut nt, vis);
+            visit_nonterminal(Lrc::make_mut(nt), vis);
         }
         _ => {}
     }
@@ -791,7 +791,7 @@ pub fn visit_nonterminal<T: MutVisitor>(nt: &mut token::Nonterminal, vis: &mut T
         token::NtMeta(item) => {
             let AttrItem { path, args, tokens } = item.deref_mut();
             vis.visit_path(path);
-            visit_mac_args(args, vis);
+            visit_attr_args(args, vis);
             visit_lazy_tts(tokens, vis);
         }
         token::NtPath(path) => vis.visit_path(path),
@@ -879,7 +879,7 @@ pub fn noop_flat_map_generic_param<T: MutVisitor>(
     let GenericParam { id, ident, attrs, bounds, kind, colon_span, is_placeholder: _ } = &mut param;
     vis.visit_id(id);
     vis.visit_ident(ident);
-    if let Some(ref mut colon_span) = colon_span {
+    if let Some(colon_span) = colon_span {
         vis.visit_span(colon_span);
     }
     visit_attrs(attrs, vis);
@@ -1303,12 +1303,17 @@ pub fn noop_visit_expr<T: MutVisitor>(
             vis.visit_expr(f);
             visit_exprs(args, vis);
         }
-        ExprKind::MethodCall(PathSegment { ident, id, args }, receiver, exprs, span) => {
+        ExprKind::MethodCall(box MethodCall {
+            seg: PathSegment { ident, id, args: seg_args },
+            receiver,
+            args: call_args,
+            span,
+        }) => {
             vis.visit_ident(ident);
             vis.visit_id(id);
-            visit_opt(args, |args| vis.visit_generic_args(args));
+            visit_opt(seg_args, |args| vis.visit_generic_args(args));
             vis.visit_method_receiver_expr(receiver);
-            visit_exprs(exprs, vis);
+            visit_exprs(call_args, vis);
             vis.visit_span(span);
         }
         ExprKind::Binary(_binop, lhs, rhs) => {
@@ -1345,20 +1350,30 @@ pub fn noop_visit_expr<T: MutVisitor>(
             vis.visit_block(body);
             visit_opt(label, |label| vis.visit_label(label));
         }
-        ExprKind::Loop(body, label) => {
+        ExprKind::Loop(body, label, span) => {
             vis.visit_block(body);
             visit_opt(label, |label| vis.visit_label(label));
+            vis.visit_span(span);
         }
         ExprKind::Match(expr, arms) => {
             vis.visit_expr(expr);
             arms.flat_map_in_place(|arm| vis.flat_map_arm(arm));
         }
-        ExprKind::Closure(binder, _capture_by, asyncness, _movability, decl, body, span) => {
+        ExprKind::Closure(box Closure {
+            binder,
+            capture_clause: _,
+            asyncness,
+            movability: _,
+            fn_decl,
+            body,
+            fn_decl_span,
+            fn_arg_span: _,
+        }) => {
             vis.visit_closure_binder(binder);
             vis.visit_asyncness(asyncness);
-            vis.visit_fn_decl(decl);
+            vis.visit_fn_decl(fn_decl);
             vis.visit_expr(body);
-            vis.visit_span(span);
+            vis.visit_span(fn_decl_span);
         }
         ExprKind::Block(blk, label) => {
             vis.visit_block(blk);
@@ -1428,7 +1443,7 @@ pub fn noop_visit_expr<T: MutVisitor>(
         }
         ExprKind::Try(expr) => vis.visit_expr(expr),
         ExprKind::TryBlock(body) => vis.visit_block(body),
-        ExprKind::Lit(_) | ExprKind::Err => {}
+        ExprKind::Lit(_) | ExprKind::IncludedBytes(..) | ExprKind::Err => {}
     }
     vis.visit_id(id);
     vis.visit_span(span);
diff --git a/compiler/rustc_ast/src/token.rs b/compiler/rustc_ast/src/token.rs
index 83b10d906..c0cc4e79a 100644
--- a/compiler/rustc_ast/src/token.rs
+++ b/compiler/rustc_ast/src/token.rs
@@ -5,6 +5,7 @@ pub use TokenKind::*;
 
 use crate::ast;
 use crate::ptr::P;
+use crate::util::case::Case;
 
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_data_structures::sync::Lrc;
@@ -58,13 +59,17 @@ pub enum Delimiter {
     Invisible,
 }
 
+// Note that the suffix is *not* considered when deciding the `LitKind` in this
+// type. This means that float literals like `1f32` are classified by this type
+// as `Int`. Only upon conversion to `ast::LitKind` will such a literal be
+// given the `Float` kind.
 #[derive(Clone, Copy, PartialEq, Encodable, Decodable, Debug, HashStable_Generic)]
 pub enum LitKind {
     Bool, // AST only, must never appear in a `Token`
     Byte,
     Char,
-    Integer,
-    Float,
+    Integer, // e.g. `1`, `1u8`, `1f32`
+    Float,   // e.g. `1.`, `1.0`, `1e3f32`
     Str,
     StrRaw(u8), // raw string delimited by `n` hash symbols
     ByteStr,
@@ -80,6 +85,42 @@ pub struct Lit {
     pub suffix: Option<Symbol>,
 }
 
+impl Lit {
+    pub fn new(kind: LitKind, symbol: Symbol, suffix: Option<Symbol>) -> Lit {
+        Lit { kind, symbol, suffix }
+    }
+
+    /// Returns `true` if this is semantically a float literal. This includes
+    /// ones like `1f32` that have an `Integer` kind but a float suffix.
+    pub fn is_semantic_float(&self) -> bool {
+        match self.kind {
+            LitKind::Float => true,
+            LitKind::Integer => match self.suffix {
+                Some(sym) => sym == sym::f32 || sym == sym::f64,
+                None => false,
+            },
+            _ => false,
+        }
+    }
+
+    /// Keep this in sync with `Token::can_begin_literal_or_bool` excluding unary negation.
+    pub fn from_token(token: &Token) -> Option<Lit> {
+        match token.uninterpolate().kind {
+            Ident(name, false) if name.is_bool_lit() => {
+                Some(Lit::new(Bool, name, None))
+            }
+            Literal(token_lit) => Some(token_lit),
+            Interpolated(ref nt)
+                if let NtExpr(expr) | NtLiteral(expr) = &**nt
+                && let ast::ExprKind::Lit(token_lit) = expr.kind =>
+            {
+                Some(token_lit.clone())
+            }
+            _ => None,
+        }
+    }
+}
+
 impl fmt::Display for Lit {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         let Lit { kind, symbol, suffix } = *self;
@@ -138,12 +179,6 @@ impl LitKind {
     }
 }
 
-impl Lit {
-    pub fn new(kind: LitKind, symbol: Symbol, suffix: Option<Symbol>) -> Lit {
-        Lit { kind, symbol, suffix }
-    }
-}
-
 pub fn ident_can_begin_expr(name: Symbol, span: Span, is_raw: bool) -> bool {
     let ident_token = Token::new(Ident(name, is_raw), span);
 
@@ -267,9 +302,9 @@ 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`.
+    /// 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),
@@ -503,10 +538,10 @@ impl Token {
         }
     }
 
-    // A convenience function for matching on identifiers during parsing.
-    // Turns interpolated identifier (`$i: ident`) or lifetime (`$l: lifetime`) token
-    // into the regular identifier or lifetime token it refers to,
-    // otherwise returns the original token.
+    /// A convenience function for matching on identifiers during parsing.
+    /// Turns interpolated identifier (`$i: ident`) or lifetime (`$l: lifetime`) token
+    /// into the regular identifier or lifetime token it refers to,
+    /// otherwise returns the original token.
     pub fn uninterpolate(&self) -> Cow<'_, Token> {
         match &self.kind {
             Interpolated(nt) => match **nt {
@@ -566,9 +601,10 @@ impl Token {
 
     /// Returns `true` if the token is an interpolated path.
     fn is_path(&self) -> bool {
-        if let Interpolated(ref nt) = self.kind && let NtPath(..) = **nt {
+        if let Interpolated(nt) = &self.kind && let NtPath(..) = **nt {
             return true;
         }
+
         false
     }
 
@@ -576,7 +612,7 @@ impl Token {
     /// That is, is this a pre-parsed expression dropped into the token stream
     /// (which happens while parsing the result of macro expansion)?
     pub fn is_whole_expr(&self) -> bool {
-        if let Interpolated(ref nt) = self.kind
+        if let Interpolated(nt) = &self.kind
             && let NtExpr(_) | NtLiteral(_) | NtPath(_) | NtBlock(_) = **nt
         {
             return true;
@@ -585,11 +621,12 @@ impl Token {
         false
     }
 
-    // Is the token an interpolated block (`$b:block`)?
+    /// Is the token an interpolated block (`$b:block`)?
     pub fn is_whole_block(&self) -> bool {
-        if let Interpolated(ref nt) = self.kind && let NtBlock(..) = **nt {
+        if let Interpolated(nt) = &self.kind && let NtBlock(..) = **nt {
             return true;
         }
+
         false
     }
 
@@ -615,12 +652,21 @@ impl Token {
         self.is_non_raw_ident_where(|id| id.name == kw)
     }
 
+    /// Returns `true` if the token is a given keyword, `kw` or if `case` is `Insensitive` and this token is an identifier equal to `kw` ignoring the case.
+    pub fn is_keyword_case(&self, kw: Symbol, case: Case) -> bool {
+        self.is_keyword(kw)
+            || (case == Case::Insensitive
+                && self.is_non_raw_ident_where(|id| {
+                    id.name.as_str().to_lowercase() == kw.as_str().to_lowercase()
+                }))
+    }
+
     pub fn is_path_segment_keyword(&self) -> bool {
         self.is_non_raw_ident_where(Ident::is_path_segment_keyword)
     }
 
-    // Returns true for reserved identifiers used internally for elided lifetimes,
-    // unnamed method parameters, crate root module, error recovery etc.
+    /// Returns true for reserved identifiers used internally for elided lifetimes,
+    /// unnamed method parameters, crate root module, error recovery etc.
     pub fn is_special_ident(&self) -> bool {
         self.is_non_raw_ident_where(Ident::is_special)
     }
diff --git a/compiler/rustc_ast/src/tokenstream.rs b/compiler/rustc_ast/src/tokenstream.rs
index 015f5c1ee..482c30295 100644
--- a/compiler/rustc_ast/src/tokenstream.rs
+++ b/compiler/rustc_ast/src/tokenstream.rs
@@ -64,7 +64,7 @@ impl TokenTree {
         match (self, other) {
             (TokenTree::Token(token, _), TokenTree::Token(token2, _)) => token.kind == token2.kind,
             (TokenTree::Delimited(_, delim, tts), TokenTree::Delimited(_, delim2, tts2)) => {
-                delim == delim2 && tts.eq_unspanned(&tts2)
+                delim == delim2 && tts.eq_unspanned(tts2)
             }
             _ => false,
         }
@@ -86,12 +86,12 @@ impl TokenTree {
         }
     }
 
-    // Create a `TokenTree::Token` with alone spacing.
+    /// Create a `TokenTree::Token` with alone spacing.
     pub fn token_alone(kind: TokenKind, span: Span) -> TokenTree {
         TokenTree::Token(Token::new(kind, span), Spacing::Alone)
     }
 
-    // Create a `TokenTree::Token` with joint spacing.
+    /// Create a `TokenTree::Token` with joint spacing.
     pub fn token_joint(kind: TokenKind, span: Span) -> TokenTree {
         TokenTree::Token(Token::new(kind, span), Spacing::Joint)
     }
@@ -402,7 +402,7 @@ impl TokenStream {
         let mut t1 = self.trees();
         let mut t2 = other.trees();
         for (t1, t2) in iter::zip(&mut t1, &mut t2) {
-            if !t1.eq_unspanned(&t2) {
+            if !t1.eq_unspanned(t2) {
                 return false;
             }
         }
@@ -413,17 +413,17 @@ impl TokenStream {
         TokenStream(Lrc::new(self.0.iter().enumerate().map(|(i, tree)| f(i, tree)).collect()))
     }
 
-    // Create a token stream containing a single token with alone spacing.
+    /// Create a token stream containing a single token with alone spacing.
     pub fn token_alone(kind: TokenKind, span: Span) -> TokenStream {
         TokenStream::new(vec![TokenTree::token_alone(kind, span)])
     }
 
-    // Create a token stream containing a single token with joint spacing.
+    /// Create a token stream containing a single token with joint spacing.
     pub fn token_joint(kind: TokenKind, span: Span) -> TokenStream {
         TokenStream::new(vec![TokenTree::token_joint(kind, span)])
     }
 
-    // Create a token stream containing a single `Delimited`.
+    /// Create a token stream containing a single `Delimited`.
     pub fn delimited(span: DelimSpan, delim: Delimiter, tts: TokenStream) -> TokenStream {
         TokenStream::new(vec![TokenTree::Delimited(span, delim, tts)])
     }
@@ -475,7 +475,7 @@ impl TokenStream {
             token::Interpolated(nt) => TokenTree::Delimited(
                 DelimSpan::from_single(token.span),
                 Delimiter::Invisible,
-                TokenStream::from_nonterminal_ast(&nt).flattened(),
+                TokenStream::from_nonterminal_ast(nt).flattened(),
             ),
             _ => TokenTree::Token(token.clone(), spacing),
         }
@@ -511,7 +511,7 @@ impl TokenStream {
     fn try_glue_to_last(vec: &mut Vec<TokenTree>, tt: &TokenTree) -> bool {
         if let Some(TokenTree::Token(last_tok, Spacing::Joint)) = vec.last()
             && let TokenTree::Token(tok, spacing) = tt
-            && let Some(glued_tok) = last_tok.glue(&tok)
+            && let Some(glued_tok) = last_tok.glue(tok)
         {
             // ...then overwrite the last token tree in `vec` with the
             // glued token, and skip the first token tree from `stream`.
@@ -522,8 +522,8 @@ impl TokenStream {
         }
     }
 
-    // Push `tt` onto the end of the stream, possibly gluing it to the last
-    // token. Uses `make_mut` to maximize efficiency.
+    /// Push `tt` onto the end of the stream, possibly gluing it to the last
+    /// token. Uses `make_mut` to maximize efficiency.
     pub fn push_tree(&mut self, tt: TokenTree) {
         let vec_mut = Lrc::make_mut(&mut self.0);
 
@@ -534,9 +534,9 @@ impl TokenStream {
         }
     }
 
-    // Push `stream` onto the end of the stream, possibly gluing the first
-    // token tree to the last token. (No other token trees will be glued.)
-    // Uses `make_mut` to maximize efficiency.
+    /// Push `stream` onto the end of the stream, possibly gluing the first
+    /// token tree to the last token. (No other token trees will be glued.)
+    /// Uses `make_mut` to maximize efficiency.
     pub fn push_stream(&mut self, stream: TokenStream) {
         let vec_mut = Lrc::make_mut(&mut self.0);
 
diff --git a/compiler/rustc_ast/src/util/case.rs b/compiler/rustc_ast/src/util/case.rs
new file mode 100644
index 000000000..1afd7dea7
--- /dev/null
+++ b/compiler/rustc_ast/src/util/case.rs
@@ -0,0 +1,6 @@
+/// Whatever to ignore case (`fn` vs `Fn` vs `FN`) or not. Used for recovering.
+#[derive(Copy, Clone, Debug, Eq, PartialEq)]
+pub enum Case {
+    Sensitive,
+    Insensitive,
+}
diff --git a/compiler/rustc_ast/src/util/classify.rs b/compiler/rustc_ast/src/util/classify.rs
index 6ea3db6d3..cdc244c12 100644
--- a/compiler/rustc_ast/src/util/classify.rs
+++ b/compiler/rustc_ast/src/util/classify.rs
@@ -21,6 +21,7 @@ pub fn expr_requires_semi_to_be_stmt(e: &ast::Expr) -> bool {
             | ast::ExprKind::Loop(..)
             | ast::ExprKind::ForLoop(..)
             | ast::ExprKind::TryBlock(..)
+            | ast::ExprKind::ConstBlock(..)
     )
 }
 
@@ -36,7 +37,6 @@ pub fn expr_trailing_brace(mut expr: &ast::Expr) -> Option<&ast::Expr> {
             | Binary(_, _, e)
             | Box(e)
             | Break(_, Some(e))
-            | Closure(.., e, _)
             | Let(_, e, _)
             | Range(_, Some(e), _)
             | Ret(Some(e))
@@ -44,6 +44,9 @@ pub fn expr_trailing_brace(mut expr: &ast::Expr) -> Option<&ast::Expr> {
             | Yield(Some(e)) => {
                 expr = e;
             }
+            Closure(closure) => {
+                expr = &closure.body;
+            }
             Async(..) | Block(..) | ForLoop(..) | If(..) | Loop(..) | Match(..) | Struct(..)
             | TryBlock(..) | While(..) => break Some(expr),
             _ => break None,
diff --git a/compiler/rustc_ast/src/util/comments.rs b/compiler/rustc_ast/src/util/comments.rs
index c96474ccb..35454c3a6 100644
--- a/compiler/rustc_ast/src/util/comments.rs
+++ b/compiler/rustc_ast/src/util/comments.rs
@@ -110,7 +110,7 @@ pub fn beautify_doc_string(data: Symbol, kind: CommentKind) -> Symbol {
         } else {
             &mut lines
         };
-        if let Some(horizontal) = get_horizontal_trim(&lines, kind) {
+        if let Some(horizontal) = get_horizontal_trim(lines, kind) {
             changes = true;
             // remove a "[ \t]*\*" block from each line, if possible
             for line in lines.iter_mut() {
@@ -147,7 +147,7 @@ fn all_whitespace(s: &str, col: CharPos) -> Option<usize> {
 
 fn trim_whitespace_prefix(s: &str, col: CharPos) -> &str {
     let len = s.len();
-    match all_whitespace(&s, col) {
+    match all_whitespace(s, col) {
         Some(col) => {
             if col < len {
                 &s[col..]
diff --git a/compiler/rustc_ast/src/util/literal.rs b/compiler/rustc_ast/src/util/literal.rs
index 536b38560..f6f186b51 100644
--- a/compiler/rustc_ast/src/util/literal.rs
+++ b/compiler/rustc_ast/src/util/literal.rs
@@ -1,17 +1,14 @@
 //! Code related to parsing literals.
 
-use crate::ast::{self, Lit, LitKind};
+use crate::ast::{self, LitKind, MetaItemLit};
 use crate::token::{self, Token};
-
-use rustc_lexer::unescape::{unescape_byte, unescape_char};
-use rustc_lexer::unescape::{unescape_byte_literal, unescape_literal, Mode};
+use rustc_lexer::unescape::{byte_from_char, unescape_byte, unescape_char, unescape_literal, Mode};
 use rustc_span::symbol::{kw, sym, Symbol};
 use rustc_span::Span;
-
 use std::ascii;
 
+#[derive(Debug)]
 pub enum LitError {
-    NotLiteral,
     LexerError,
     InvalidSuffix,
     InvalidIntSuffix,
@@ -55,14 +52,14 @@ impl LitKind {
                 // new symbol because the string in the LitKind is different to the
                 // string in the token.
                 let s = symbol.as_str();
-                let symbol = if s.contains(&['\\', '\r']) {
+                let symbol = if s.contains(['\\', '\r']) {
                     let mut buf = String::with_capacity(s.len());
                     let mut error = Ok(());
                     // Force-inlining here is aggressive but the closure is
                     // called on every char in the string, so it can be
                     // hot in programs with many long strings.
                     unescape_literal(
-                        &s,
+                        s,
                         Mode::Str,
                         &mut #[inline(always)]
                         |_, unescaped_char| match unescaped_char {
@@ -88,7 +85,7 @@ impl LitKind {
                     if s.contains('\r') {
                         let mut buf = String::with_capacity(s.len());
                         let mut error = Ok(());
-                        unescape_literal(&s, Mode::RawStr, &mut |_, unescaped_char| {
+                        unescape_literal(s, Mode::RawStr, &mut |_, unescaped_char| {
                             match unescaped_char {
                                 Ok(c) => buf.push(c),
                                 Err(err) => {
@@ -109,13 +106,11 @@ impl LitKind {
                 let s = symbol.as_str();
                 let mut buf = Vec::with_capacity(s.len());
                 let mut error = Ok(());
-                unescape_byte_literal(&s, Mode::ByteStr, &mut |_, unescaped_byte| {
-                    match unescaped_byte {
-                        Ok(c) => buf.push(c),
-                        Err(err) => {
-                            if err.is_fatal() {
-                                error = Err(LitError::LexerError);
-                            }
+                unescape_literal(s, Mode::ByteStr, &mut |_, c| match c {
+                    Ok(c) => buf.push(byte_from_char(c)),
+                    Err(err) => {
+                        if err.is_fatal() {
+                            error = Err(LitError::LexerError);
                         }
                     }
                 });
@@ -127,13 +122,11 @@ impl LitKind {
                 let bytes = if s.contains('\r') {
                     let mut buf = Vec::with_capacity(s.len());
                     let mut error = Ok(());
-                    unescape_byte_literal(&s, Mode::RawByteStr, &mut |_, unescaped_byte| {
-                        match unescaped_byte {
-                            Ok(c) => buf.push(c),
-                            Err(err) => {
-                                if err.is_fatal() {
-                                    error = Err(LitError::LexerError);
-                                }
+                    unescape_literal(s, Mode::RawByteStr, &mut |_, c| match c {
+                        Ok(c) => buf.push(byte_from_char(c)),
+                        Err(err) => {
+                            if err.is_fatal() {
+                                error = Err(LitError::LexerError);
                             }
                         }
                     });
@@ -202,49 +195,16 @@ impl LitKind {
     }
 }
 
-impl Lit {
-    /// Converts literal token into an AST literal.
-    pub fn from_token_lit(token_lit: token::Lit, span: Span) -> Result<Lit, LitError> {
-        Ok(Lit { token_lit, kind: LitKind::from_token_lit(token_lit)?, span })
-    }
-
-    /// Converts arbitrary token into an AST literal.
-    ///
-    /// Keep this in sync with `Token::can_begin_literal_or_bool` excluding unary negation.
-    pub fn from_token(token: &Token) -> Result<Lit, LitError> {
-        let lit = match token.uninterpolate().kind {
-            token::Ident(name, false) if name.is_bool_lit() => {
-                token::Lit::new(token::Bool, name, None)
-            }
-            token::Literal(lit) => lit,
-            token::Interpolated(ref nt) => {
-                if let token::NtExpr(expr) | token::NtLiteral(expr) = &**nt
-                    && let ast::ExprKind::Lit(lit) = &expr.kind
-                {
-                    return Ok(lit.clone());
-                }
-                return Err(LitError::NotLiteral);
-            }
-            _ => return Err(LitError::NotLiteral),
-        };
-
-        Lit::from_token_lit(lit, token.span)
-    }
-
-    /// Attempts to recover an AST literal from semantic literal.
-    /// This function is used when the original token doesn't exist (e.g. the literal is created
-    /// by an AST-based macro) or unavailable (e.g. from HIR pretty-printing).
-    pub fn from_lit_kind(kind: LitKind, span: Span) -> Lit {
-        Lit { token_lit: kind.to_token_lit(), kind, span }
+impl MetaItemLit {
+    /// Converts token literal into a meta item literal.
+    pub fn from_token_lit(token_lit: token::Lit, span: Span) -> Result<MetaItemLit, LitError> {
+        Ok(MetaItemLit { token_lit, kind: LitKind::from_token_lit(token_lit)?, span })
     }
 
-    /// Losslessly convert an AST literal into a token.
-    pub fn to_token(&self) -> Token {
-        let kind = match self.token_lit.kind {
-            token::Bool => token::Ident(self.token_lit.symbol, false),
-            _ => token::Literal(self.token_lit),
-        };
-        Token::new(kind, self.span)
+    /// Converts an arbitrary token into meta item literal.
+    pub fn from_token(token: &Token) -> Option<MetaItemLit> {
+        token::Lit::from_token(token)
+            .and_then(|token_lit| MetaItemLit::from_token_lit(token_lit, token.span).ok())
     }
 }
 
diff --git a/compiler/rustc_ast/src/util/parser.rs b/compiler/rustc_ast/src/util/parser.rs
index b40ad6f70..819f1884a 100644
--- a/compiler/rustc_ast/src/util/parser.rs
+++ b/compiler/rustc_ast/src/util/parser.rs
@@ -377,28 +377,28 @@ pub fn needs_par_as_let_scrutinee(order: i8) -> bool {
 /// parens or other delimiters, e.g., `X { y: 1 }`, `X { y: 1 }.method()`, `foo == X { y: 1 }` and
 /// `X { y: 1 } == foo` all do, but `(X { y: 1 }) == foo` does not.
 pub fn contains_exterior_struct_lit(value: &ast::Expr) -> bool {
-    match value.kind {
+    match &value.kind {
         ast::ExprKind::Struct(..) => true,
 
-        ast::ExprKind::Assign(ref lhs, ref rhs, _)
-        | ast::ExprKind::AssignOp(_, ref lhs, ref rhs)
-        | ast::ExprKind::Binary(_, ref lhs, ref rhs) => {
+        ast::ExprKind::Assign(lhs, rhs, _)
+        | ast::ExprKind::AssignOp(_, lhs, rhs)
+        | ast::ExprKind::Binary(_, lhs, rhs) => {
             // X { y: 1 } + X { y: 2 }
-            contains_exterior_struct_lit(&lhs) || contains_exterior_struct_lit(&rhs)
+            contains_exterior_struct_lit(lhs) || contains_exterior_struct_lit(rhs)
         }
-        ast::ExprKind::Await(ref x)
-        | ast::ExprKind::Unary(_, ref x)
-        | ast::ExprKind::Cast(ref x, _)
-        | ast::ExprKind::Type(ref x, _)
-        | ast::ExprKind::Field(ref x, _)
-        | ast::ExprKind::Index(ref x, _) => {
+        ast::ExprKind::Await(x)
+        | ast::ExprKind::Unary(_, x)
+        | ast::ExprKind::Cast(x, _)
+        | ast::ExprKind::Type(x, _)
+        | ast::ExprKind::Field(x, _)
+        | ast::ExprKind::Index(x, _) => {
             // &X { y: 1 }, X { y: 1 }.y
-            contains_exterior_struct_lit(&x)
+            contains_exterior_struct_lit(x)
         }
 
-        ast::ExprKind::MethodCall(_, ref receiver, _, _) => {
+        ast::ExprKind::MethodCall(box ast::MethodCall { receiver, .. }) => {
             // X { y: 1 }.bar(...)
-            contains_exterior_struct_lit(&receiver)
+            contains_exterior_struct_lit(receiver)
         }
 
         _ => false,
diff --git a/compiler/rustc_ast/src/util/unicode.rs b/compiler/rustc_ast/src/util/unicode.rs
index f009f7b30..0eae791b2 100644
--- a/compiler/rustc_ast/src/util/unicode.rs
+++ b/compiler/rustc_ast/src/util/unicode.rs
@@ -17,7 +17,7 @@ pub fn contains_text_flow_control_chars(s: &str) -> bool {
     // U+2069 - E2 81 A9
     let mut bytes = s.as_bytes();
     loop {
-        match core::slice::memchr::memchr(0xE2, &bytes) {
+        match core::slice::memchr::memchr(0xE2, bytes) {
             Some(idx) => {
                 // bytes are valid UTF-8 -> E2 must be followed by two bytes
                 let ch = &bytes[idx..idx + 3];
diff --git a/compiler/rustc_ast/src/visit.rs b/compiler/rustc_ast/src/visit.rs
index 6f56c1ef0..991eb489f 100644
--- a/compiler/rustc_ast/src/visit.rs
+++ b/compiler/rustc_ast/src/visit.rs
@@ -251,7 +251,7 @@ pub trait Visitor<'ast>: Sized {
 macro_rules! walk_list {
     ($visitor: expr, $method: ident, $list: expr $(, $($extra_args: expr),* )?) => {
         {
-            #[cfg_attr(not(bootstrap), allow(for_loops_over_fallibles))]
+            #[allow(for_loops_over_fallibles)]
             for elem in $list {
                 $visitor.$method(elem $(, $($extra_args,)* )?)
             }
@@ -299,74 +299,68 @@ pub fn walk_trait_ref<'a, V: Visitor<'a>>(visitor: &mut V, trait_ref: &'a TraitR
 pub fn walk_item<'a, V: Visitor<'a>>(visitor: &mut V, item: &'a Item) {
     visitor.visit_vis(&item.vis);
     visitor.visit_ident(item.ident);
-    match item.kind {
+    match &item.kind {
         ItemKind::ExternCrate(_) => {}
-        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::Use(use_tree) => visitor.visit_use_tree(use_tree, item.id, false),
+        ItemKind::Static(typ, _, expr) | ItemKind::Const(_, typ, expr) => {
             visitor.visit_ty(typ);
             walk_list!(visitor, visit_expr, expr);
         }
-        ItemKind::Fn(box Fn { defaultness: _, ref generics, ref sig, ref body }) => {
+        ItemKind::Fn(box Fn { defaultness: _, generics, sig, body }) => {
             let kind =
                 FnKind::Fn(FnCtxt::Free, item.ident, sig, &item.vis, generics, body.as_deref());
             visitor.visit_fn(kind, item.span, item.id)
         }
-        ItemKind::Mod(_unsafety, ref mod_kind) => match mod_kind {
+        ItemKind::Mod(_unsafety, mod_kind) => match mod_kind {
             ModKind::Loaded(items, _inline, _inner_span) => {
                 walk_list!(visitor, visit_item, items)
             }
             ModKind::Unloaded => {}
         },
-        ItemKind::ForeignMod(ref foreign_module) => {
+        ItemKind::ForeignMod(foreign_module) => {
             walk_list!(visitor, visit_foreign_item, &foreign_module.items);
         }
-        ItemKind::GlobalAsm(ref asm) => visitor.visit_inline_asm(asm),
-        ItemKind::TyAlias(box TyAlias { ref generics, ref bounds, ref ty, .. }) => {
+        ItemKind::GlobalAsm(asm) => visitor.visit_inline_asm(asm),
+        ItemKind::TyAlias(box TyAlias { generics, bounds, ty, .. }) => {
             visitor.visit_generics(generics);
             walk_list!(visitor, visit_param_bound, bounds, BoundKind::Bound);
             walk_list!(visitor, visit_ty, ty);
         }
-        ItemKind::Enum(ref enum_definition, ref generics) => {
+        ItemKind::Enum(enum_definition, generics) => {
             visitor.visit_generics(generics);
             visitor.visit_enum_def(enum_definition)
         }
         ItemKind::Impl(box Impl {
             defaultness: _,
             unsafety: _,
-            ref generics,
+            generics,
             constness: _,
             polarity: _,
-            ref of_trait,
-            ref self_ty,
-            ref items,
+            of_trait,
+            self_ty,
+            items,
         }) => {
             visitor.visit_generics(generics);
             walk_list!(visitor, visit_trait_ref, of_trait);
             visitor.visit_ty(self_ty);
             walk_list!(visitor, visit_assoc_item, items, AssocCtxt::Impl);
         }
-        ItemKind::Struct(ref struct_definition, ref generics)
-        | ItemKind::Union(ref struct_definition, ref generics) => {
+        ItemKind::Struct(struct_definition, generics)
+        | ItemKind::Union(struct_definition, generics) => {
             visitor.visit_generics(generics);
             visitor.visit_variant_data(struct_definition);
         }
-        ItemKind::Trait(box Trait {
-            unsafety: _,
-            is_auto: _,
-            ref generics,
-            ref bounds,
-            ref items,
-        }) => {
+        ItemKind::Trait(box Trait { unsafety: _, is_auto: _, generics, bounds, items }) => {
             visitor.visit_generics(generics);
             walk_list!(visitor, visit_param_bound, bounds, BoundKind::SuperTraits);
             walk_list!(visitor, visit_assoc_item, items, AssocCtxt::Trait);
         }
-        ItemKind::TraitAlias(ref generics, ref bounds) => {
+        ItemKind::TraitAlias(generics, bounds) => {
             visitor.visit_generics(generics);
             walk_list!(visitor, visit_param_bound, bounds, BoundKind::Bound);
         }
-        ItemKind::MacCall(ref mac) => visitor.visit_mac_call(mac),
-        ItemKind::MacroDef(ref ts) => visitor.visit_mac_def(ts, item.id),
+        ItemKind::MacCall(mac) => visitor.visit_mac_call(mac),
+        ItemKind::MacroDef(ts) => visitor.visit_mac_def(ts, item.id),
     }
     walk_list!(visitor, visit_attribute, &item.attrs);
 }
@@ -399,39 +393,39 @@ pub fn walk_pat_field<'a, V: Visitor<'a>>(visitor: &mut V, fp: &'a PatField) {
 }
 
 pub fn walk_ty<'a, V: Visitor<'a>>(visitor: &mut V, typ: &'a Ty) {
-    match typ.kind {
-        TyKind::Slice(ref ty) | TyKind::Paren(ref ty) => visitor.visit_ty(ty),
-        TyKind::Ptr(ref mutable_type) => visitor.visit_ty(&mutable_type.ty),
-        TyKind::Rptr(ref opt_lifetime, ref mutable_type) => {
+    match &typ.kind {
+        TyKind::Slice(ty) | TyKind::Paren(ty) => visitor.visit_ty(ty),
+        TyKind::Ptr(mutable_type) => visitor.visit_ty(&mutable_type.ty),
+        TyKind::Rptr(opt_lifetime, mutable_type) => {
             walk_list!(visitor, visit_lifetime, opt_lifetime, LifetimeCtxt::Rptr);
             visitor.visit_ty(&mutable_type.ty)
         }
-        TyKind::Tup(ref tuple_element_types) => {
+        TyKind::Tup(tuple_element_types) => {
             walk_list!(visitor, visit_ty, tuple_element_types);
         }
-        TyKind::BareFn(ref function_declaration) => {
+        TyKind::BareFn(function_declaration) => {
             walk_list!(visitor, visit_generic_param, &function_declaration.generic_params);
             walk_fn_decl(visitor, &function_declaration.decl);
         }
-        TyKind::Path(ref maybe_qself, ref path) => {
-            if let Some(ref qself) = *maybe_qself {
+        TyKind::Path(maybe_qself, path) => {
+            if let Some(qself) = maybe_qself {
                 visitor.visit_ty(&qself.ty);
             }
             visitor.visit_path(path, typ.id);
         }
-        TyKind::Array(ref ty, ref length) => {
+        TyKind::Array(ty, length) => {
             visitor.visit_ty(ty);
             visitor.visit_anon_const(length)
         }
-        TyKind::TraitObject(ref bounds, ..) => {
+        TyKind::TraitObject(bounds, ..) => {
             walk_list!(visitor, visit_param_bound, bounds, BoundKind::TraitObject);
         }
-        TyKind::ImplTrait(_, ref bounds) => {
+        TyKind::ImplTrait(_, bounds) => {
             walk_list!(visitor, visit_param_bound, bounds, BoundKind::Impl);
         }
-        TyKind::Typeof(ref expression) => visitor.visit_anon_const(expression),
+        TyKind::Typeof(expression) => visitor.visit_anon_const(expression),
         TyKind::Infer | TyKind::ImplicitSelf | TyKind::Err => {}
-        TyKind::MacCall(ref mac) => visitor.visit_mac_call(mac),
+        TyKind::MacCall(mac) => visitor.visit_mac_call(mac),
         TyKind::Never | TyKind::CVarArgs => {}
     }
 }
@@ -444,15 +438,15 @@ pub fn walk_path<'a, V: Visitor<'a>>(visitor: &mut V, path: &'a Path) {
 
 pub fn walk_use_tree<'a, V: Visitor<'a>>(visitor: &mut V, use_tree: &'a UseTree, id: NodeId) {
     visitor.visit_path(&use_tree.prefix, id);
-    match use_tree.kind {
-        UseTreeKind::Simple(rename, ..) => {
+    match &use_tree.kind {
+        UseTreeKind::Simple(rename) => {
             // The extra IDs are handled during HIR lowering.
-            if let Some(rename) = rename {
+            if let &Some(rename) = rename {
                 visitor.visit_ident(rename);
             }
         }
         UseTreeKind::Glob => {}
-        UseTreeKind::Nested(ref use_trees) => {
+        UseTreeKind::Nested(use_trees) => {
             for &(ref nested_tree, nested_id) in use_trees {
                 visitor.visit_use_tree(nested_tree, nested_id, true);
             }
@@ -462,7 +456,7 @@ pub fn walk_use_tree<'a, V: Visitor<'a>>(visitor: &mut V, use_tree: &'a UseTree,
 
 pub fn walk_path_segment<'a, V: Visitor<'a>>(visitor: &mut V, segment: &'a PathSegment) {
     visitor.visit_ident(segment.ident);
-    if let Some(ref args) = segment.args {
+    if let Some(args) = &segment.args {
         visitor.visit_generic_args(args);
     }
 }
@@ -471,8 +465,8 @@ pub fn walk_generic_args<'a, V>(visitor: &mut V, generic_args: &'a GenericArgs)
 where
     V: Visitor<'a>,
 {
-    match *generic_args {
-        GenericArgs::AngleBracketed(ref data) => {
+    match generic_args {
+        GenericArgs::AngleBracketed(data) => {
             for arg in &data.args {
                 match arg {
                     AngleBracketedArg::Arg(a) => visitor.visit_generic_arg(a),
@@ -480,7 +474,7 @@ where
                 }
             }
         }
-        GenericArgs::Parenthesized(ref data) => {
+        GenericArgs::Parenthesized(data) => {
             walk_list!(visitor, visit_ty, &data.inputs);
             walk_fn_ret_ty(visitor, &data.output);
         }
@@ -500,64 +494,64 @@ where
 
 pub fn walk_assoc_constraint<'a, V: Visitor<'a>>(visitor: &mut V, constraint: &'a AssocConstraint) {
     visitor.visit_ident(constraint.ident);
-    if let Some(ref gen_args) = constraint.gen_args {
+    if let Some(gen_args) = &constraint.gen_args {
         visitor.visit_generic_args(gen_args);
     }
-    match constraint.kind {
-        AssocConstraintKind::Equality { ref term } => match term {
+    match &constraint.kind {
+        AssocConstraintKind::Equality { term } => match term {
             Term::Ty(ty) => visitor.visit_ty(ty),
             Term::Const(c) => visitor.visit_anon_const(c),
         },
-        AssocConstraintKind::Bound { ref bounds } => {
+        AssocConstraintKind::Bound { bounds } => {
             walk_list!(visitor, visit_param_bound, bounds, BoundKind::Bound);
         }
     }
 }
 
 pub fn walk_pat<'a, V: Visitor<'a>>(visitor: &mut V, pattern: &'a Pat) {
-    match pattern.kind {
-        PatKind::TupleStruct(ref opt_qself, ref path, ref elems) => {
-            if let Some(ref qself) = *opt_qself {
+    match &pattern.kind {
+        PatKind::TupleStruct(opt_qself, path, elems) => {
+            if let Some(qself) = opt_qself {
                 visitor.visit_ty(&qself.ty);
             }
             visitor.visit_path(path, pattern.id);
             walk_list!(visitor, visit_pat, elems);
         }
-        PatKind::Path(ref opt_qself, ref path) => {
-            if let Some(ref qself) = *opt_qself {
+        PatKind::Path(opt_qself, path) => {
+            if let Some(qself) = opt_qself {
                 visitor.visit_ty(&qself.ty);
             }
             visitor.visit_path(path, pattern.id)
         }
-        PatKind::Struct(ref opt_qself, ref path, ref fields, _) => {
-            if let Some(ref qself) = *opt_qself {
+        PatKind::Struct(opt_qself, path, fields, _) => {
+            if let Some(qself) = opt_qself {
                 visitor.visit_ty(&qself.ty);
             }
             visitor.visit_path(path, pattern.id);
             walk_list!(visitor, visit_pat_field, fields);
         }
-        PatKind::Box(ref subpattern)
-        | PatKind::Ref(ref subpattern, _)
-        | PatKind::Paren(ref subpattern) => visitor.visit_pat(subpattern),
-        PatKind::Ident(_, ident, ref optional_subpattern) => {
-            visitor.visit_ident(ident);
+        PatKind::Box(subpattern) | PatKind::Ref(subpattern, _) | PatKind::Paren(subpattern) => {
+            visitor.visit_pat(subpattern)
+        }
+        PatKind::Ident(_, ident, optional_subpattern) => {
+            visitor.visit_ident(*ident);
             walk_list!(visitor, visit_pat, optional_subpattern);
         }
-        PatKind::Lit(ref expression) => visitor.visit_expr(expression),
-        PatKind::Range(ref lower_bound, ref upper_bound, _) => {
+        PatKind::Lit(expression) => visitor.visit_expr(expression),
+        PatKind::Range(lower_bound, upper_bound, _) => {
             walk_list!(visitor, visit_expr, lower_bound);
             walk_list!(visitor, visit_expr, upper_bound);
         }
         PatKind::Wild | PatKind::Rest => {}
-        PatKind::Tuple(ref elems) | PatKind::Slice(ref elems) | PatKind::Or(ref elems) => {
+        PatKind::Tuple(elems) | PatKind::Slice(elems) | PatKind::Or(elems) => {
             walk_list!(visitor, visit_pat, elems);
         }
-        PatKind::MacCall(ref mac) => visitor.visit_mac_call(mac),
+        PatKind::MacCall(mac) => visitor.visit_mac_call(mac),
     }
 }
 
 pub fn walk_foreign_item<'a, V: Visitor<'a>>(visitor: &mut V, item: &'a ForeignItem) {
-    let Item { id, span, ident, ref vis, ref attrs, ref kind, tokens: _ } = *item;
+    let &Item { id, span, ident, ref vis, ref attrs, ref kind, tokens: _ } = item;
     visitor.visit_vis(vis);
     visitor.visit_ident(ident);
     walk_list!(visitor, visit_attribute, attrs);
@@ -566,7 +560,7 @@ pub fn walk_foreign_item<'a, V: Visitor<'a>>(visitor: &mut V, item: &'a ForeignI
             visitor.visit_ty(ty);
             walk_list!(visitor, visit_expr, expr);
         }
-        ForeignItemKind::Fn(box Fn { defaultness: _, ref generics, ref sig, ref body }) => {
+        ForeignItemKind::Fn(box Fn { defaultness: _, generics, sig, body }) => {
             let kind = FnKind::Fn(FnCtxt::Foreign, ident, sig, vis, generics, body.as_deref());
             visitor.visit_fn(kind, span, id);
         }
@@ -582,11 +576,9 @@ pub fn walk_foreign_item<'a, V: Visitor<'a>>(visitor: &mut V, item: &'a ForeignI
 }
 
 pub fn walk_param_bound<'a, V: Visitor<'a>>(visitor: &mut V, bound: &'a GenericBound) {
-    match *bound {
-        GenericBound::Trait(ref typ, ref _modifier) => visitor.visit_poly_trait_ref(typ),
-        GenericBound::Outlives(ref lifetime) => {
-            visitor.visit_lifetime(lifetime, LifetimeCtxt::Bound)
-        }
+    match bound {
+        GenericBound::Trait(typ, _modifier) => visitor.visit_poly_trait_ref(typ),
+        GenericBound::Outlives(lifetime) => visitor.visit_lifetime(lifetime, LifetimeCtxt::Bound),
     }
 }
 
@@ -594,10 +586,10 @@ pub fn walk_generic_param<'a, V: Visitor<'a>>(visitor: &mut V, param: &'a Generi
     visitor.visit_ident(param.ident);
     walk_list!(visitor, visit_attribute, param.attrs.iter());
     walk_list!(visitor, visit_param_bound, &param.bounds, BoundKind::Bound);
-    match param.kind {
+    match &param.kind {
         GenericParamKind::Lifetime => (),
-        GenericParamKind::Type { ref default } => walk_list!(visitor, visit_ty, default),
-        GenericParamKind::Const { ref ty, ref default, .. } => {
+        GenericParamKind::Type { default } => walk_list!(visitor, visit_ty, default),
+        GenericParamKind::Const { ty, default, .. } => {
             visitor.visit_ty(ty);
             if let Some(default) = default {
                 visitor.visit_anon_const(default);
@@ -621,24 +613,22 @@ pub fn walk_closure_binder<'a, V: Visitor<'a>>(visitor: &mut V, binder: &'a Clos
 }
 
 pub fn walk_where_predicate<'a, V: Visitor<'a>>(visitor: &mut V, predicate: &'a WherePredicate) {
-    match *predicate {
+    match predicate {
         WherePredicate::BoundPredicate(WhereBoundPredicate {
-            ref bounded_ty,
-            ref bounds,
-            ref bound_generic_params,
+            bounded_ty,
+            bounds,
+            bound_generic_params,
             ..
         }) => {
             visitor.visit_ty(bounded_ty);
             walk_list!(visitor, visit_param_bound, bounds, BoundKind::Bound);
             walk_list!(visitor, visit_generic_param, bound_generic_params);
         }
-        WherePredicate::RegionPredicate(WhereRegionPredicate {
-            ref lifetime, ref bounds, ..
-        }) => {
+        WherePredicate::RegionPredicate(WhereRegionPredicate { lifetime, bounds, .. }) => {
             visitor.visit_lifetime(lifetime, LifetimeCtxt::Bound);
             walk_list!(visitor, visit_param_bound, bounds, BoundKind::Bound);
         }
-        WherePredicate::EqPredicate(WhereEqPredicate { ref lhs_ty, ref rhs_ty, .. }) => {
+        WherePredicate::EqPredicate(WhereEqPredicate { lhs_ty, rhs_ty, .. }) => {
             visitor.visit_ty(lhs_ty);
             visitor.visit_ty(rhs_ty);
         }
@@ -646,7 +636,7 @@ 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 FnRetTy) {
-    if let FnRetTy::Ty(ref output_ty) = *ret_ty {
+    if let FnRetTy::Ty(output_ty) = ret_ty {
         visitor.visit_ty(output_ty)
     }
 }
@@ -675,7 +665,7 @@ pub fn walk_fn<'a, V: Visitor<'a>>(visitor: &mut V, kind: FnKind<'a>) {
 }
 
 pub fn walk_assoc_item<'a, V: Visitor<'a>>(visitor: &mut V, item: &'a AssocItem, ctxt: AssocCtxt) {
-    let Item { id, span, ident, ref vis, ref attrs, ref kind, tokens: _ } = *item;
+    let &Item { id, span, ident, ref vis, ref attrs, ref kind, tokens: _ } = item;
     visitor.visit_vis(vis);
     visitor.visit_ident(ident);
     walk_list!(visitor, visit_attribute, attrs);
@@ -684,7 +674,7 @@ pub fn walk_assoc_item<'a, V: Visitor<'a>>(visitor: &mut V, item: &'a AssocItem,
             visitor.visit_ty(ty);
             walk_list!(visitor, visit_expr, expr);
         }
-        AssocItemKind::Fn(box Fn { defaultness: _, ref generics, ref sig, ref body }) => {
+        AssocItemKind::Fn(box Fn { defaultness: _, generics, sig, body }) => {
             let kind = FnKind::Fn(FnCtxt::Assoc(ctxt), ident, sig, vis, generics, body.as_deref());
             visitor.visit_fn(kind, span, id);
         }
@@ -717,13 +707,13 @@ pub fn walk_block<'a, V: Visitor<'a>>(visitor: &mut V, block: &'a Block) {
 }
 
 pub fn walk_stmt<'a, V: Visitor<'a>>(visitor: &mut V, statement: &'a Stmt) {
-    match statement.kind {
-        StmtKind::Local(ref local) => visitor.visit_local(local),
-        StmtKind::Item(ref item) => visitor.visit_item(item),
-        StmtKind::Expr(ref expr) | StmtKind::Semi(ref expr) => visitor.visit_expr(expr),
+    match &statement.kind {
+        StmtKind::Local(local) => visitor.visit_local(local),
+        StmtKind::Item(item) => visitor.visit_item(item),
+        StmtKind::Expr(expr) | StmtKind::Semi(expr) => visitor.visit_expr(expr),
         StmtKind::Empty => {}
-        StmtKind::MacCall(ref mac) => {
-            let MacCallStmt { ref mac, style: _, ref attrs, tokens: _ } = **mac;
+        StmtKind::MacCall(mac) => {
+            let MacCallStmt { mac, attrs, style: _, tokens: _ } = &**mac;
             visitor.visit_mac_call(mac);
             for attr in attrs.iter() {
                 visitor.visit_attribute(attr);
@@ -760,7 +750,7 @@ pub fn walk_inline_asm<'a, V: Visitor<'a>>(visitor: &mut V, asm: &'a InlineAsm)
 }
 
 pub fn walk_inline_asm_sym<'a, V: Visitor<'a>>(visitor: &mut V, sym: &'a InlineAsmSym) {
-    if let Some(ref qself) = sym.qself {
+    if let Some(qself) = &sym.qself {
         visitor.visit_ty(&qself.ty);
     }
     visitor.visit_path(&sym.path, sym.id);
@@ -769,18 +759,18 @@ pub fn walk_inline_asm_sym<'a, V: Visitor<'a>>(visitor: &mut V, sym: &'a InlineA
 pub fn walk_expr<'a, V: Visitor<'a>>(visitor: &mut V, expression: &'a Expr) {
     walk_list!(visitor, visit_attribute, expression.attrs.iter());
 
-    match expression.kind {
-        ExprKind::Box(ref subexpression) => visitor.visit_expr(subexpression),
-        ExprKind::Array(ref subexpressions) => {
+    match &expression.kind {
+        ExprKind::Box(subexpression) => visitor.visit_expr(subexpression),
+        ExprKind::Array(subexpressions) => {
             walk_list!(visitor, visit_expr, subexpressions);
         }
-        ExprKind::ConstBlock(ref anon_const) => visitor.visit_anon_const(anon_const),
-        ExprKind::Repeat(ref element, ref count) => {
+        ExprKind::ConstBlock(anon_const) => visitor.visit_anon_const(anon_const),
+        ExprKind::Repeat(element, count) => {
             visitor.visit_expr(element);
             visitor.visit_anon_const(count)
         }
-        ExprKind::Struct(ref se) => {
-            if let Some(ref qself) = se.qself {
+        ExprKind::Struct(se) => {
+            if let Some(qself) = &se.qself {
                 visitor.visit_ty(&qself.ty);
             }
             visitor.visit_path(&se.path, expression.id);
@@ -791,117 +781,126 @@ pub fn walk_expr<'a, V: Visitor<'a>>(visitor: &mut V, expression: &'a Expr) {
                 StructRest::None => {}
             }
         }
-        ExprKind::Tup(ref subexpressions) => {
+        ExprKind::Tup(subexpressions) => {
             walk_list!(visitor, visit_expr, subexpressions);
         }
-        ExprKind::Call(ref callee_expression, ref arguments) => {
+        ExprKind::Call(callee_expression, arguments) => {
             visitor.visit_expr(callee_expression);
             walk_list!(visitor, visit_expr, arguments);
         }
-        ExprKind::MethodCall(ref segment, ref receiver, ref arguments, _span) => {
-            visitor.visit_path_segment(segment);
+        ExprKind::MethodCall(box MethodCall { seg, receiver, args, span: _ }) => {
+            visitor.visit_path_segment(seg);
             visitor.visit_expr(receiver);
-            walk_list!(visitor, visit_expr, arguments);
+            walk_list!(visitor, visit_expr, args);
         }
-        ExprKind::Binary(_, ref left_expression, ref right_expression) => {
+        ExprKind::Binary(_, left_expression, right_expression) => {
             visitor.visit_expr(left_expression);
             visitor.visit_expr(right_expression)
         }
-        ExprKind::AddrOf(_, _, ref subexpression) | ExprKind::Unary(_, ref subexpression) => {
+        ExprKind::AddrOf(_, _, subexpression) | ExprKind::Unary(_, subexpression) => {
             visitor.visit_expr(subexpression)
         }
-        ExprKind::Cast(ref subexpression, ref typ) | ExprKind::Type(ref subexpression, ref typ) => {
+        ExprKind::Cast(subexpression, typ) | ExprKind::Type(subexpression, typ) => {
             visitor.visit_expr(subexpression);
             visitor.visit_ty(typ)
         }
-        ExprKind::Let(ref pat, ref expr, _) => {
+        ExprKind::Let(pat, expr, _) => {
             visitor.visit_pat(pat);
             visitor.visit_expr(expr);
         }
-        ExprKind::If(ref head_expression, ref if_block, ref optional_else) => {
+        ExprKind::If(head_expression, if_block, optional_else) => {
             visitor.visit_expr(head_expression);
             visitor.visit_block(if_block);
             walk_list!(visitor, visit_expr, optional_else);
         }
-        ExprKind::While(ref subexpression, ref block, ref opt_label) => {
+        ExprKind::While(subexpression, block, opt_label) => {
             walk_list!(visitor, visit_label, opt_label);
             visitor.visit_expr(subexpression);
             visitor.visit_block(block);
         }
-        ExprKind::ForLoop(ref pattern, ref subexpression, ref block, ref opt_label) => {
+        ExprKind::ForLoop(pattern, subexpression, block, opt_label) => {
             walk_list!(visitor, visit_label, opt_label);
             visitor.visit_pat(pattern);
             visitor.visit_expr(subexpression);
             visitor.visit_block(block);
         }
-        ExprKind::Loop(ref block, ref opt_label) => {
+        ExprKind::Loop(block, opt_label, _) => {
             walk_list!(visitor, visit_label, opt_label);
             visitor.visit_block(block);
         }
-        ExprKind::Match(ref subexpression, ref arms) => {
+        ExprKind::Match(subexpression, arms) => {
             visitor.visit_expr(subexpression);
             walk_list!(visitor, visit_arm, arms);
         }
-        ExprKind::Closure(ref binder, _, _, _, ref decl, ref body, _decl_span) => {
-            visitor.visit_fn(FnKind::Closure(binder, decl, body), expression.span, expression.id)
+        ExprKind::Closure(box Closure {
+            binder,
+            capture_clause: _,
+            asyncness: _,
+            movability: _,
+            fn_decl,
+            body,
+            fn_decl_span: _,
+            fn_arg_span: _,
+        }) => {
+            visitor.visit_fn(FnKind::Closure(binder, fn_decl, body), expression.span, expression.id)
         }
-        ExprKind::Block(ref block, ref opt_label) => {
+        ExprKind::Block(block, opt_label) => {
             walk_list!(visitor, visit_label, opt_label);
             visitor.visit_block(block);
         }
-        ExprKind::Async(_, _, ref body) => {
+        ExprKind::Async(_, _, body) => {
             visitor.visit_block(body);
         }
-        ExprKind::Await(ref expr) => visitor.visit_expr(expr),
-        ExprKind::Assign(ref lhs, ref rhs, _) => {
+        ExprKind::Await(expr) => visitor.visit_expr(expr),
+        ExprKind::Assign(lhs, rhs, _) => {
             visitor.visit_expr(lhs);
             visitor.visit_expr(rhs);
         }
-        ExprKind::AssignOp(_, ref left_expression, ref right_expression) => {
+        ExprKind::AssignOp(_, left_expression, right_expression) => {
             visitor.visit_expr(left_expression);
             visitor.visit_expr(right_expression);
         }
-        ExprKind::Field(ref subexpression, ident) => {
+        ExprKind::Field(subexpression, ident) => {
             visitor.visit_expr(subexpression);
-            visitor.visit_ident(ident);
+            visitor.visit_ident(*ident);
         }
-        ExprKind::Index(ref main_expression, ref index_expression) => {
+        ExprKind::Index(main_expression, index_expression) => {
             visitor.visit_expr(main_expression);
             visitor.visit_expr(index_expression)
         }
-        ExprKind::Range(ref start, ref end, _) => {
+        ExprKind::Range(start, end, _) => {
             walk_list!(visitor, visit_expr, start);
             walk_list!(visitor, visit_expr, end);
         }
         ExprKind::Underscore => {}
-        ExprKind::Path(ref maybe_qself, ref path) => {
-            if let Some(ref qself) = *maybe_qself {
+        ExprKind::Path(maybe_qself, path) => {
+            if let Some(qself) = maybe_qself {
                 visitor.visit_ty(&qself.ty);
             }
             visitor.visit_path(path, expression.id)
         }
-        ExprKind::Break(ref opt_label, ref opt_expr) => {
+        ExprKind::Break(opt_label, opt_expr) => {
             walk_list!(visitor, visit_label, opt_label);
             walk_list!(visitor, visit_expr, opt_expr);
         }
-        ExprKind::Continue(ref opt_label) => {
+        ExprKind::Continue(opt_label) => {
             walk_list!(visitor, visit_label, opt_label);
         }
-        ExprKind::Ret(ref optional_expression) => {
+        ExprKind::Ret(optional_expression) => {
             walk_list!(visitor, visit_expr, optional_expression);
         }
-        ExprKind::Yeet(ref optional_expression) => {
+        ExprKind::Yeet(optional_expression) => {
             walk_list!(visitor, visit_expr, optional_expression);
         }
-        ExprKind::MacCall(ref mac) => visitor.visit_mac_call(mac),
-        ExprKind::Paren(ref subexpression) => visitor.visit_expr(subexpression),
-        ExprKind::InlineAsm(ref asm) => visitor.visit_inline_asm(asm),
-        ExprKind::Yield(ref optional_expression) => {
+        ExprKind::MacCall(mac) => visitor.visit_mac_call(mac),
+        ExprKind::Paren(subexpression) => visitor.visit_expr(subexpression),
+        ExprKind::InlineAsm(asm) => visitor.visit_inline_asm(asm),
+        ExprKind::Yield(optional_expression) => {
             walk_list!(visitor, visit_expr, optional_expression);
         }
-        ExprKind::Try(ref subexpression) => visitor.visit_expr(subexpression),
-        ExprKind::TryBlock(ref body) => visitor.visit_block(body),
-        ExprKind::Lit(_) | ExprKind::Err => {}
+        ExprKind::Try(subexpression) => visitor.visit_expr(subexpression),
+        ExprKind::TryBlock(body) => visitor.visit_block(body),
+        ExprKind::Lit(_) | ExprKind::IncludedBytes(..) | ExprKind::Err => {}
     }
 
     visitor.visit_expr_post(expression)
@@ -927,18 +926,18 @@ pub fn walk_vis<'a, V: Visitor<'a>>(visitor: &mut V, vis: &'a Visibility) {
 }
 
 pub fn walk_attribute<'a, V: Visitor<'a>>(visitor: &mut V, attr: &'a Attribute) {
-    match attr.kind {
-        AttrKind::Normal(ref normal) => walk_mac_args(visitor, &normal.item.args),
+    match &attr.kind {
+        AttrKind::Normal(normal) => walk_attr_args(visitor, &normal.item.args),
         AttrKind::DocComment(..) => {}
     }
 }
 
-pub fn walk_mac_args<'a, V: Visitor<'a>>(visitor: &mut V, args: &'a MacArgs) {
+pub fn walk_attr_args<'a, V: Visitor<'a>>(visitor: &mut V, args: &'a AttrArgs) {
     match args {
-        MacArgs::Empty => {}
-        MacArgs::Delimited(_dspan, _delim, _tokens) => {}
-        MacArgs::Eq(_eq_span, MacArgsEq::Ast(expr)) => visitor.visit_expr(expr),
-        MacArgs::Eq(_, MacArgsEq::Hir(lit)) => {
+        AttrArgs::Empty => {}
+        AttrArgs::Delimited(_) => {}
+        AttrArgs::Eq(_eq_span, AttrArgsEq::Ast(expr)) => visitor.visit_expr(expr),
+        AttrArgs::Eq(_, AttrArgsEq::Hir(lit)) => {
             unreachable!("in literal form when walking mac args eq: {:?}", lit)
         }
     }
diff --git a/compiler/rustc_ast_lowering/Cargo.toml b/compiler/rustc_ast_lowering/Cargo.toml
index ce1c8d499..6a59b9e61 100644
--- a/compiler/rustc_ast_lowering/Cargo.toml
+++ b/compiler/rustc_ast_lowering/Cargo.toml
@@ -21,5 +21,5 @@ rustc_session = { path = "../rustc_session" }
 rustc_span = { path = "../rustc_span" }
 rustc_target = { path = "../rustc_target" }
 smallvec = { version = "1.8.1", features = ["union", "may_dangle"] }
-thin-vec = "0.2.8"
+thin-vec = "0.2.9"
 tracing = "0.1"
diff --git a/compiler/rustc_ast_lowering/src/asm.rs b/compiler/rustc_ast_lowering/src/asm.rs
index 450cdf246..dfef6ec70 100644
--- a/compiler/rustc_ast_lowering/src/asm.rs
+++ b/compiler/rustc_ast_lowering/src/asm.rs
@@ -11,7 +11,7 @@ use super::LoweringContext;
 
 use rustc_ast::ptr::P;
 use rustc_ast::*;
-use rustc_data_structures::fx::{FxHashMap, FxHashSet};
+use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap};
 use rustc_hir as hir;
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::definitions::DefPathData;
@@ -71,7 +71,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             .emit();
         }
 
-        let mut clobber_abis = FxHashMap::default();
+        let mut clobber_abis = FxIndexMap::default();
         if let Some(asm_arch) = asm_arch {
             for (abi_name, abi_span) in &asm.clobber_abis {
                 match asm::InlineAsmClobberAbi::parse(asm_arch, &self.tcx.sess.target, *abi_name) {
@@ -123,7 +123,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             .operands
             .iter()
             .map(|(op, op_sp)| {
-                let lower_reg = |reg| match reg {
+                let lower_reg = |&reg: &_| match reg {
                     InlineAsmRegOrRegClass::Reg(reg) => {
                         asm::InlineAsmRegOrRegClass::Reg(if let Some(asm_arch) = asm_arch {
                             asm::InlineAsmReg::parse(asm_arch, reg).unwrap_or_else(|error| {
@@ -152,32 +152,30 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                     }
                 };
 
-                let op = match *op {
-                    InlineAsmOperand::In { reg, ref expr } => hir::InlineAsmOperand::In {
+                let op = match op {
+                    InlineAsmOperand::In { reg, expr } => hir::InlineAsmOperand::In {
                         reg: lower_reg(reg),
                         expr: self.lower_expr(expr),
                     },
-                    InlineAsmOperand::Out { reg, late, ref expr } => hir::InlineAsmOperand::Out {
+                    InlineAsmOperand::Out { reg, late, expr } => hir::InlineAsmOperand::Out {
                         reg: lower_reg(reg),
-                        late,
+                        late: *late,
                         expr: expr.as_ref().map(|expr| self.lower_expr(expr)),
                     },
-                    InlineAsmOperand::InOut { reg, late, ref expr } => {
-                        hir::InlineAsmOperand::InOut {
-                            reg: lower_reg(reg),
-                            late,
-                            expr: self.lower_expr(expr),
-                        }
-                    }
-                    InlineAsmOperand::SplitInOut { reg, late, ref in_expr, ref out_expr } => {
+                    InlineAsmOperand::InOut { reg, late, expr } => hir::InlineAsmOperand::InOut {
+                        reg: lower_reg(reg),
+                        late: *late,
+                        expr: self.lower_expr(expr),
+                    },
+                    InlineAsmOperand::SplitInOut { reg, late, in_expr, out_expr } => {
                         hir::InlineAsmOperand::SplitInOut {
                             reg: lower_reg(reg),
-                            late,
+                            late: *late,
                             in_expr: self.lower_expr(in_expr),
                             out_expr: out_expr.as_ref().map(|expr| self.lower_expr(expr)),
                         }
                     }
-                    InlineAsmOperand::Const { ref anon_const } => {
+                    InlineAsmOperand::Const { anon_const } => {
                         if !self.tcx.features().asm_const {
                             feature_err(
                                 &sess.parse_sess,
@@ -191,7 +189,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                             anon_const: self.lower_anon_const(anon_const),
                         }
                     }
-                    InlineAsmOperand::Sym { ref sym } => {
+                    InlineAsmOperand::Sym { sym } => {
                         let static_def_id = self
                             .resolver
                             .get_partial_res(sym.id)
@@ -224,7 +222,12 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                             // Wrap the expression in an AnonConst.
                             let parent_def_id = self.current_hir_id_owner;
                             let node_id = self.next_node_id();
-                            self.create_def(parent_def_id.def_id, node_id, DefPathData::AnonConst);
+                            self.create_def(
+                                parent_def_id.def_id,
+                                node_id,
+                                DefPathData::AnonConst,
+                                *op_sp,
+                            );
                             let anon_const = AnonConst { id: node_id, value: P(expr) };
                             hir::InlineAsmOperand::SymFn {
                                 anon_const: self.lower_anon_const(&anon_const),
@@ -347,7 +350,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                                     skip = true;
 
                                     let idx2 = *o.get();
-                                    let &(ref op2, op_sp2) = &operands[idx2];
+                                    let (ref op2, op_sp2) = operands[idx2];
                                     let Some(asm::InlineAsmRegOrRegClass::Reg(reg2)) = op2.reg() else {
                                         unreachable!();
                                     };
diff --git a/compiler/rustc_ast_lowering/src/block.rs b/compiler/rustc_ast_lowering/src/block.rs
index 12a0cc0d2..d310f72f7 100644
--- a/compiler/rustc_ast_lowering/src/block.rs
+++ b/compiler/rustc_ast_lowering/src/block.rs
@@ -31,8 +31,8 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         let mut stmts = SmallVec::<[hir::Stmt<'hir>; 8]>::new();
         let mut expr = None;
         while let [s, tail @ ..] = ast_stmts {
-            match s.kind {
-                StmtKind::Local(ref local) => {
+            match &s.kind {
+                StmtKind::Local(local) => {
                     let hir_id = self.lower_node_id(s.id);
                     let local = self.lower_local(local);
                     self.alias_attrs(hir_id, local.hir_id);
@@ -40,7 +40,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                     let span = self.lower_span(s.span);
                     stmts.push(hir::Stmt { hir_id, kind, span });
                 }
-                StmtKind::Item(ref it) => {
+                StmtKind::Item(it) => {
                     stmts.extend(self.lower_item_ref(it).into_iter().enumerate().map(
                         |(i, item_id)| {
                             let hir_id = match i {
@@ -53,7 +53,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                         },
                     ));
                 }
-                StmtKind::Expr(ref e) => {
+                StmtKind::Expr(e) => {
                     let e = self.lower_expr(e);
                     if tail.is_empty() {
                         expr = Some(e);
@@ -65,7 +65,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                         stmts.push(hir::Stmt { hir_id, kind, span });
                     }
                 }
-                StmtKind::Semi(ref e) => {
+                StmtKind::Semi(e) => {
                     let e = self.lower_expr(e);
                     let hir_id = self.lower_node_id(s.id);
                     self.alias_attrs(hir_id, e.hir_id);
diff --git a/compiler/rustc_ast_lowering/src/errors.rs b/compiler/rustc_ast_lowering/src/errors.rs
index 157f46501..21c6a2d26 100644
--- a/compiler/rustc_ast_lowering/src/errors.rs
+++ b/compiler/rustc_ast_lowering/src/errors.rs
@@ -277,8 +277,9 @@ pub struct RegisterConflict<'a> {
 pub struct SubTupleBinding<'a> {
     #[primary_span]
     #[label]
-    #[suggestion_verbose(
+    #[suggestion(
         ast_lowering_sub_tuple_binding_suggestion,
+        style = "verbose",
         code = "..",
         applicability = "maybe-incorrect"
     )]
diff --git a/compiler/rustc_ast_lowering/src/expr.rs b/compiler/rustc_ast_lowering/src/expr.rs
index ec9c39350..7dd6d5acc 100644
--- a/compiler/rustc_ast_lowering/src/expr.rs
+++ b/compiler/rustc_ast_lowering/src/expr.rs
@@ -14,6 +14,7 @@ use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_hir as hir;
 use rustc_hir::def::Res;
 use rustc_hir::definitions::DefPathData;
+use rustc_session::errors::report_lit_error;
 use rustc_span::source_map::{respan, DesugaringKind, Span, Spanned};
 use rustc_span::symbol::{sym, Ident};
 use rustc_span::DUMMY_SP;
@@ -30,20 +31,20 @@ impl<'hir> LoweringContext<'_, 'hir> {
 
     pub(super) fn lower_expr_mut(&mut self, e: &Expr) -> hir::Expr<'hir> {
         ensure_sufficient_stack(|| {
-            let kind = match e.kind {
-                ExprKind::Box(ref inner) => hir::ExprKind::Box(self.lower_expr(inner)),
-                ExprKind::Array(ref exprs) => hir::ExprKind::Array(self.lower_exprs(exprs)),
-                ExprKind::ConstBlock(ref anon_const) => {
+            let kind = match &e.kind {
+                ExprKind::Box(inner) => hir::ExprKind::Box(self.lower_expr(inner)),
+                ExprKind::Array(exprs) => hir::ExprKind::Array(self.lower_exprs(exprs)),
+                ExprKind::ConstBlock(anon_const) => {
                     let anon_const = self.lower_anon_const(anon_const);
                     hir::ExprKind::ConstBlock(anon_const)
                 }
-                ExprKind::Repeat(ref expr, ref count) => {
+                ExprKind::Repeat(expr, count) => {
                     let expr = self.lower_expr(expr);
                     let count = self.lower_array_length(count);
                     hir::ExprKind::Repeat(expr, count)
                 }
-                ExprKind::Tup(ref elts) => hir::ExprKind::Tup(self.lower_exprs(elts)),
-                ExprKind::Call(ref f, ref args) => {
+                ExprKind::Tup(elts) => hir::ExprKind::Tup(self.lower_exprs(elts)),
+                ExprKind::Call(f, args) => {
                     if e.attrs.get(0).map_or(false, |a| a.has_name(sym::rustc_box)) {
                         if let [inner] = &args[..] && e.attrs.len() == 1 {
                             let kind = hir::ExprKind::Box(self.lower_expr(&inner));
@@ -60,7 +61,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                         hir::ExprKind::Call(f, self.lower_exprs(args))
                     }
                 }
-                ExprKind::MethodCall(ref seg, ref receiver, ref args, span) => {
+                ExprKind::MethodCall(box MethodCall { seg, receiver, args, span }) => {
                     let hir_seg = self.arena.alloc(self.lower_path_segment(
                         e.span,
                         seg,
@@ -71,81 +72,89 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     let receiver = self.lower_expr(receiver);
                     let args =
                         self.arena.alloc_from_iter(args.iter().map(|x| self.lower_expr_mut(x)));
-                    hir::ExprKind::MethodCall(hir_seg, receiver, args, self.lower_span(span))
+                    hir::ExprKind::MethodCall(hir_seg, receiver, args, self.lower_span(*span))
                 }
-                ExprKind::Binary(binop, ref lhs, ref rhs) => {
-                    let binop = self.lower_binop(binop);
+                ExprKind::Binary(binop, lhs, rhs) => {
+                    let binop = self.lower_binop(*binop);
                     let lhs = self.lower_expr(lhs);
                     let rhs = self.lower_expr(rhs);
                     hir::ExprKind::Binary(binop, lhs, rhs)
                 }
-                ExprKind::Unary(op, ref ohs) => {
-                    let op = self.lower_unop(op);
+                ExprKind::Unary(op, ohs) => {
+                    let op = self.lower_unop(*op);
                     let ohs = self.lower_expr(ohs);
                     hir::ExprKind::Unary(op, ohs)
                 }
-                ExprKind::Lit(ref l) => {
-                    hir::ExprKind::Lit(respan(self.lower_span(l.span), l.kind.clone()))
+                ExprKind::Lit(token_lit) => {
+                    let lit_kind = match LitKind::from_token_lit(*token_lit) {
+                        Ok(lit_kind) => lit_kind,
+                        Err(err) => {
+                            report_lit_error(&self.tcx.sess.parse_sess, err, *token_lit, e.span);
+                            LitKind::Err
+                        }
+                    };
+                    hir::ExprKind::Lit(respan(self.lower_span(e.span), lit_kind))
                 }
-                ExprKind::Cast(ref expr, ref ty) => {
+                ExprKind::IncludedBytes(bytes) => hir::ExprKind::Lit(respan(
+                    self.lower_span(e.span),
+                    LitKind::ByteStr(bytes.clone()),
+                )),
+                ExprKind::Cast(expr, ty) => {
                     let expr = self.lower_expr(expr);
                     let ty =
                         self.lower_ty(ty, &ImplTraitContext::Disallowed(ImplTraitPosition::Type));
                     hir::ExprKind::Cast(expr, ty)
                 }
-                ExprKind::Type(ref expr, ref ty) => {
+                ExprKind::Type(expr, ty) => {
                     let expr = self.lower_expr(expr);
                     let ty =
                         self.lower_ty(ty, &ImplTraitContext::Disallowed(ImplTraitPosition::Type));
                     hir::ExprKind::Type(expr, ty)
                 }
-                ExprKind::AddrOf(k, m, ref ohs) => {
+                ExprKind::AddrOf(k, m, ohs) => {
                     let ohs = self.lower_expr(ohs);
-                    hir::ExprKind::AddrOf(k, m, ohs)
+                    hir::ExprKind::AddrOf(*k, *m, ohs)
                 }
-                ExprKind::Let(ref pat, ref scrutinee, span) => {
+                ExprKind::Let(pat, scrutinee, span) => {
                     hir::ExprKind::Let(self.arena.alloc(hir::Let {
                         hir_id: self.next_id(),
-                        span: self.lower_span(span),
+                        span: self.lower_span(*span),
                         pat: self.lower_pat(pat),
                         ty: None,
                         init: self.lower_expr(scrutinee),
                     }))
                 }
-                ExprKind::If(ref cond, ref then, ref else_opt) => {
+                ExprKind::If(cond, then, else_opt) => {
                     self.lower_expr_if(cond, then, else_opt.as_deref())
                 }
-                ExprKind::While(ref cond, ref body, opt_label) => {
-                    self.with_loop_scope(e.id, |this| {
-                        let span =
-                            this.mark_span_with_reason(DesugaringKind::WhileLoop, e.span, None);
-                        this.lower_expr_while_in_loop_scope(span, cond, body, opt_label)
-                    })
-                }
-                ExprKind::Loop(ref body, opt_label) => self.with_loop_scope(e.id, |this| {
+                ExprKind::While(cond, body, opt_label) => self.with_loop_scope(e.id, |this| {
+                    let span = this.mark_span_with_reason(DesugaringKind::WhileLoop, e.span, None);
+                    this.lower_expr_while_in_loop_scope(span, cond, body, *opt_label)
+                }),
+                ExprKind::Loop(body, opt_label, span) => self.with_loop_scope(e.id, |this| {
                     hir::ExprKind::Loop(
                         this.lower_block(body, false),
-                        this.lower_label(opt_label),
+                        this.lower_label(*opt_label),
                         hir::LoopSource::Loop,
-                        DUMMY_SP,
+                        this.lower_span(*span),
                     )
                 }),
-                ExprKind::TryBlock(ref body) => self.lower_expr_try_block(body),
-                ExprKind::Match(ref expr, ref arms) => hir::ExprKind::Match(
+                ExprKind::TryBlock(body) => self.lower_expr_try_block(body),
+                ExprKind::Match(expr, arms) => hir::ExprKind::Match(
                     self.lower_expr(expr),
                     self.arena.alloc_from_iter(arms.iter().map(|x| self.lower_arm(x))),
                     hir::MatchSource::Normal,
                 ),
-                ExprKind::Async(capture_clause, closure_node_id, ref block) => self
-                    .make_async_expr(
-                        capture_clause,
-                        closure_node_id,
-                        None,
-                        block.span,
-                        hir::AsyncGeneratorKind::Block,
-                        |this| this.with_new_scopes(|this| this.lower_block_expr(block)),
-                    ),
-                ExprKind::Await(ref expr) => {
+                ExprKind::Async(capture_clause, closure_node_id, block) => self.make_async_expr(
+                    *capture_clause,
+                    None,
+                    *closure_node_id,
+                    None,
+                    e.span,
+                    hir::AsyncGeneratorKind::Block,
+                    |this| this.with_new_scopes(|this| this.lower_block_expr(block)),
+                ),
+                ExprKind::Await(expr) => {
                     let dot_await_span = if expr.span.hi() < e.span.hi() {
                         let span_with_whitespace = self
                             .tcx
@@ -160,66 +169,67 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     };
                     self.lower_expr_await(dot_await_span, expr)
                 }
-                ExprKind::Closure(
-                    ref binder,
+                ExprKind::Closure(box Closure {
+                    binder,
                     capture_clause,
                     asyncness,
                     movability,
-                    ref decl,
-                    ref body,
+                    fn_decl,
+                    body,
                     fn_decl_span,
-                ) => {
+                    fn_arg_span,
+                }) => {
                     if let Async::Yes { closure_id, .. } = asyncness {
                         self.lower_expr_async_closure(
                             binder,
-                            capture_clause,
+                            *capture_clause,
                             e.id,
-                            closure_id,
-                            decl,
+                            *closure_id,
+                            fn_decl,
                             body,
-                            fn_decl_span,
+                            *fn_decl_span,
+                            *fn_arg_span,
                         )
                     } else {
                         self.lower_expr_closure(
                             binder,
-                            capture_clause,
+                            *capture_clause,
                             e.id,
-                            movability,
-                            decl,
+                            *movability,
+                            fn_decl,
                             body,
-                            fn_decl_span,
+                            *fn_decl_span,
+                            *fn_arg_span,
                         )
                     }
                 }
-                ExprKind::Block(ref blk, opt_label) => {
-                    let opt_label = self.lower_label(opt_label);
+                ExprKind::Block(blk, opt_label) => {
+                    let opt_label = self.lower_label(*opt_label);
                     hir::ExprKind::Block(self.lower_block(blk, opt_label.is_some()), opt_label)
                 }
-                ExprKind::Assign(ref el, ref er, span) => {
-                    self.lower_expr_assign(el, er, span, e.span)
-                }
-                ExprKind::AssignOp(op, ref el, ref er) => hir::ExprKind::AssignOp(
-                    self.lower_binop(op),
+                ExprKind::Assign(el, er, span) => self.lower_expr_assign(el, er, *span, e.span),
+                ExprKind::AssignOp(op, el, er) => hir::ExprKind::AssignOp(
+                    self.lower_binop(*op),
                     self.lower_expr(el),
                     self.lower_expr(er),
                 ),
-                ExprKind::Field(ref el, ident) => {
-                    hir::ExprKind::Field(self.lower_expr(el), self.lower_ident(ident))
+                ExprKind::Field(el, ident) => {
+                    hir::ExprKind::Field(self.lower_expr(el), self.lower_ident(*ident))
                 }
-                ExprKind::Index(ref el, ref er) => {
+                ExprKind::Index(el, er) => {
                     hir::ExprKind::Index(self.lower_expr(el), self.lower_expr(er))
                 }
-                ExprKind::Range(Some(ref e1), Some(ref e2), RangeLimits::Closed) => {
+                ExprKind::Range(Some(e1), Some(e2), RangeLimits::Closed) => {
                     self.lower_expr_range_closed(e.span, e1, e2)
                 }
-                ExprKind::Range(ref e1, ref e2, lims) => {
-                    self.lower_expr_range(e.span, e1.as_deref(), e2.as_deref(), lims)
+                ExprKind::Range(e1, e2, lims) => {
+                    self.lower_expr_range(e.span, e1.as_deref(), e2.as_deref(), *lims)
                 }
                 ExprKind::Underscore => {
                     self.tcx.sess.emit_err(UnderscoreExprLhsAssign { span: e.span });
                     hir::ExprKind::Err
                 }
-                ExprKind::Path(ref qself, ref path) => {
+                ExprKind::Path(qself, path) => {
                     let qpath = self.lower_qpath(
                         e.id,
                         qself,
@@ -229,22 +239,22 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     );
                     hir::ExprKind::Path(qpath)
                 }
-                ExprKind::Break(opt_label, ref opt_expr) => {
+                ExprKind::Break(opt_label, opt_expr) => {
                     let opt_expr = opt_expr.as_ref().map(|x| self.lower_expr(x));
-                    hir::ExprKind::Break(self.lower_jump_destination(e.id, opt_label), opt_expr)
+                    hir::ExprKind::Break(self.lower_jump_destination(e.id, *opt_label), opt_expr)
                 }
                 ExprKind::Continue(opt_label) => {
-                    hir::ExprKind::Continue(self.lower_jump_destination(e.id, opt_label))
+                    hir::ExprKind::Continue(self.lower_jump_destination(e.id, *opt_label))
                 }
-                ExprKind::Ret(ref e) => {
+                ExprKind::Ret(e) => {
                     let e = e.as_ref().map(|x| self.lower_expr(x));
                     hir::ExprKind::Ret(e)
                 }
-                ExprKind::Yeet(ref sub_expr) => self.lower_expr_yeet(e.span, sub_expr.as_deref()),
-                ExprKind::InlineAsm(ref asm) => {
+                ExprKind::Yeet(sub_expr) => self.lower_expr_yeet(e.span, sub_expr.as_deref()),
+                ExprKind::InlineAsm(asm) => {
                     hir::ExprKind::InlineAsm(self.lower_inline_asm(e.span, asm))
                 }
-                ExprKind::Struct(ref se) => {
+                ExprKind::Struct(se) => {
                     let rest = match &se.rest {
                         StructRest::Base(e) => Some(self.lower_expr(e)),
                         StructRest::Rest(sp) => {
@@ -266,10 +276,10 @@ impl<'hir> LoweringContext<'_, 'hir> {
                         rest,
                     )
                 }
-                ExprKind::Yield(ref opt_expr) => self.lower_expr_yield(e.span, opt_expr.as_deref()),
+                ExprKind::Yield(opt_expr) => self.lower_expr_yield(e.span, opt_expr.as_deref()),
                 ExprKind::Err => hir::ExprKind::Err,
-                ExprKind::Try(ref sub_expr) => self.lower_expr_try(e.span, sub_expr),
-                ExprKind::Paren(ref ex) => {
+                ExprKind::Try(sub_expr) => self.lower_expr_try(e.span, sub_expr),
+                ExprKind::Paren(ex) => {
                     let mut ex = self.lower_expr_mut(ex);
                     // Include parens in span, but only if it is a super-span.
                     if e.span.contains(ex.span) {
@@ -294,8 +304,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
 
                 // Desugar `ExprForLoop`
                 // from: `[opt_ident]: for <pat> in <head> <body>`
-                ExprKind::ForLoop(ref pat, ref head, ref body, opt_label) => {
-                    return self.lower_expr_for(e, pat, head, body, opt_label);
+                ExprKind::ForLoop(pat, head, body, opt_label) => {
+                    return self.lower_expr_for(e, pat, head, body, *opt_label);
                 }
                 ExprKind::MacCall(_) => panic!("{:?} shouldn't exist here", e.span),
             };
@@ -346,7 +356,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         args: Vec<AstP<Expr>>,
         legacy_args_idx: &[usize],
     ) -> hir::ExprKind<'hir> {
-        let ExprKind::Path(None, ref mut path) = f.kind else {
+        let ExprKind::Path(None, path) = &mut f.kind else {
             unreachable!();
         };
 
@@ -359,7 +369,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 let node_id = self.next_node_id();
 
                 // Add a definition for the in-band const def.
-                self.create_def(parent_def_id.def_id, node_id, DefPathData::AnonConst);
+                self.create_def(parent_def_id.def_id, node_id, DefPathData::AnonConst, f.span);
 
                 let anon_const = AnonConst { id: node_id, value: arg };
                 generic_args.push(AngleBracketedArg::Arg(GenericArg::Const(anon_const)));
@@ -426,18 +436,14 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 let lhs = self.lower_cond(lhs);
                 let rhs = self.lower_cond(rhs);
 
-                self.arena.alloc(self.expr(
-                    cond.span,
-                    hir::ExprKind::Binary(op, lhs, rhs),
-                    AttrVec::new(),
-                ))
+                self.arena.alloc(self.expr(cond.span, hir::ExprKind::Binary(op, lhs, rhs)))
             }
             ExprKind::Let(..) => self.lower_expr(cond),
             _ => {
                 let cond = self.lower_expr(cond);
                 let reason = DesugaringKind::CondTemporary;
                 let span_block = self.mark_span_with_reason(reason, cond.span, None);
-                self.expr_drop_temps(span_block, cond, AttrVec::new())
+                self.expr_drop_temps(span_block, cond)
             }
         }
     }
@@ -467,12 +473,12 @@ impl<'hir> LoweringContext<'_, 'hir> {
     ) -> hir::ExprKind<'hir> {
         let lowered_cond = self.with_loop_condition_scope(|t| t.lower_cond(cond));
         let then = self.lower_block_expr(body);
-        let expr_break = self.expr_break(span, AttrVec::new());
+        let expr_break = self.expr_break(span);
         let stmt_break = self.stmt_expr(span, expr_break);
         let else_blk = self.block_all(span, arena_vec![self; stmt_break], None);
-        let else_expr = self.arena.alloc(self.expr_block(else_blk, AttrVec::new()));
+        let else_expr = self.arena.alloc(self.expr_block(else_blk));
         let if_kind = hir::ExprKind::If(lowered_cond, self.arena.alloc(then), Some(else_expr));
-        let if_expr = self.expr(span, if_kind, AttrVec::new());
+        let if_expr = self.expr(span, if_kind);
         let block = self.block_expr(self.arena.alloc(if_expr));
         let span = self.lower_span(span.with_hi(cond.span.hi()));
         let opt_label = self.lower_label(opt_label);
@@ -528,22 +534,17 @@ impl<'hir> LoweringContext<'_, 'hir> {
         expr: &'hir hir::Expr<'hir>,
         overall_span: Span,
     ) -> &'hir hir::Expr<'hir> {
-        let constructor = self.arena.alloc(self.expr_lang_item_path(
-            method_span,
-            lang_item,
-            AttrVec::new(),
-            None,
-        ));
+        let constructor = self.arena.alloc(self.expr_lang_item_path(method_span, lang_item, None));
         self.expr_call(overall_span, constructor, std::slice::from_ref(expr))
     }
 
     fn lower_arm(&mut self, arm: &Arm) -> hir::Arm<'hir> {
         let pat = self.lower_pat(&arm.pat);
         let guard = arm.guard.as_ref().map(|cond| {
-            if let ExprKind::Let(ref pat, ref scrutinee, span) = cond.kind {
+            if let ExprKind::Let(pat, scrutinee, span) = &cond.kind {
                 hir::Guard::IfLet(self.arena.alloc(hir::Let {
                     hir_id: self.next_id(),
-                    span: self.lower_span(span),
+                    span: self.lower_span(*span),
                     pat: self.lower_pat(pat),
                     ty: None,
                     init: self.lower_expr(scrutinee),
@@ -563,37 +564,35 @@ impl<'hir> LoweringContext<'_, 'hir> {
         }
     }
 
-    /// Lower an `async` construct to a generator that is then wrapped so it implements `Future`.
+    /// Lower an `async` construct to a generator that implements `Future`.
     ///
     /// This results in:
     ///
     /// ```text
-    /// std::future::from_generator(static move? |_task_context| -> <ret_ty> {
+    /// std::future::identity_future(static move? |_task_context| -> <ret_ty> {
     ///     <body>
     /// })
     /// ```
     pub(super) fn make_async_expr(
         &mut self,
         capture_clause: CaptureBy,
+        outer_hir_id: Option<hir::HirId>,
         closure_node_id: NodeId,
-        ret_ty: Option<AstP<Ty>>,
+        ret_ty: Option<hir::FnRetTy<'hir>>,
         span: Span,
         async_gen_kind: hir::AsyncGeneratorKind,
         body: impl FnOnce(&mut Self) -> hir::Expr<'hir>,
     ) -> hir::ExprKind<'hir> {
-        let output = match ret_ty {
-            Some(ty) => hir::FnRetTy::Return(
-                self.lower_ty(&ty, &ImplTraitContext::Disallowed(ImplTraitPosition::AsyncBlock)),
-            ),
-            None => hir::FnRetTy::DefaultReturn(self.lower_span(span)),
-        };
+        let output = ret_ty.unwrap_or_else(|| hir::FnRetTy::DefaultReturn(self.lower_span(span)));
 
-        // Resume argument type. We let the compiler infer this to simplify the lowering. It is
-        // fully constrained by `future::from_generator`.
+        // Resume argument type: `ResumeTy`
+        let unstable_span =
+            self.mark_span_with_reason(DesugaringKind::Async, span, self.allow_gen_future.clone());
+        let resume_ty = hir::QPath::LangItem(hir::LangItem::ResumeTy, unstable_span, None);
         let input_ty = hir::Ty {
             hir_id: self.next_id(),
-            kind: hir::TyKind::Infer,
-            span: self.lower_span(span),
+            kind: hir::TyKind::Path(resume_ty),
+            span: unstable_span,
         };
 
         // The closure/generator `FnDecl` takes a single (resume) argument of type `input_ty`.
@@ -602,6 +601,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
             output,
             c_variadic: false,
             implicit_self: hir::ImplicitSelfKind::None,
+            lifetime_elision_allowed: false,
         });
 
         // Lower the argument pattern/ident. The ident is used again in the `.await` lowering.
@@ -631,35 +631,63 @@ impl<'hir> LoweringContext<'_, 'hir> {
         // `static |_task_context| -> <ret_ty> { body }`:
         let generator_kind = {
             let c = self.arena.alloc(hir::Closure {
+                def_id: self.local_def_id(closure_node_id),
                 binder: hir::ClosureBinder::Default,
                 capture_clause,
                 bound_generic_params: &[],
                 fn_decl,
                 body,
                 fn_decl_span: self.lower_span(span),
+                fn_arg_span: None,
                 movability: Some(hir::Movability::Static),
             });
 
             hir::ExprKind::Closure(c)
         };
-        let generator = hir::Expr {
-            hir_id: self.lower_node_id(closure_node_id),
-            kind: generator_kind,
-            span: self.lower_span(span),
-        };
 
-        // `future::from_generator`:
+        let hir_id = self.lower_node_id(closure_node_id);
         let unstable_span =
             self.mark_span_with_reason(DesugaringKind::Async, span, self.allow_gen_future.clone());
-        let gen_future = self.expr_lang_item_path(
-            unstable_span,
-            hir::LangItem::FromGenerator,
-            AttrVec::new(),
-            None,
-        );
 
-        // `future::from_generator(generator)`:
-        hir::ExprKind::Call(self.arena.alloc(gen_future), arena_vec![self; generator])
+        if self.tcx.features().closure_track_caller
+            && let Some(outer_hir_id) = outer_hir_id
+            && let Some(attrs) = self.attrs.get(&outer_hir_id.local_id)
+            && attrs.into_iter().any(|attr| attr.has_name(sym::track_caller))
+        {
+            self.lower_attrs(
+                hir_id,
+                &[Attribute {
+                    kind: AttrKind::Normal(ptr::P(NormalAttr {
+                        item: AttrItem {
+                            path: Path::from_ident(Ident::new(sym::track_caller, span)),
+                            args: AttrArgs::Empty,
+                            tokens: None,
+                        },
+                        tokens: None,
+                    })),
+                    id: self.tcx.sess.parse_sess.attr_id_generator.mk_attr_id(),
+                    style: AttrStyle::Outer,
+                    span: unstable_span,
+                }],
+            );
+        }
+
+        let generator = hir::Expr { hir_id, kind: generator_kind, span: self.lower_span(span) };
+
+        // FIXME(swatinem):
+        // For some reason, the async block needs to flow through *any*
+        // call (like the identity function), as otherwise type and lifetime
+        // inference have a hard time figuring things out.
+        // Without this, we would get:
+        // E0720 in src/test/ui/impl-trait/in-trait/default-body-with-rpit.rs
+        // E0700 in src/test/ui/self/self_lifetime-async.rs
+
+        // `future::identity_future`:
+        let identity_future =
+            self.expr_lang_item_path(unstable_span, hir::LangItem::IdentityFuture, None);
+
+        // `future::identity_future(generator)`:
+        hir::ExprKind::Call(self.arena.alloc(identity_future), arena_vec![self; generator])
     }
 
     /// Desugar `<expr>.await` into:
@@ -759,7 +787,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
             let break_x = self.with_loop_scope(loop_node_id, move |this| {
                 let expr_break =
                     hir::ExprKind::Break(this.lower_loop_destination(None), Some(x_expr));
-                this.arena.alloc(this.expr(gen_future_span, expr_break, AttrVec::new()))
+                this.arena.alloc(this.expr(gen_future_span, expr_break))
             });
             self.arm(ready_pat, break_x)
         };
@@ -792,17 +820,13 @@ impl<'hir> LoweringContext<'_, 'hir> {
             let yield_expr = self.expr(
                 span,
                 hir::ExprKind::Yield(unit, hir::YieldSource::Await { expr: Some(expr_hir_id) }),
-                AttrVec::new(),
             );
             let yield_expr = self.arena.alloc(yield_expr);
 
             if let Some(task_context_hid) = self.task_context {
                 let lhs = self.expr_ident(span, task_context_ident, task_context_hid);
-                let assign = self.expr(
-                    span,
-                    hir::ExprKind::Assign(lhs, yield_expr, self.lower_span(span)),
-                    AttrVec::new(),
-                );
+                let assign =
+                    self.expr(span, hir::ExprKind::Assign(lhs, yield_expr, self.lower_span(span)));
                 self.stmt_expr(span, assign)
             } else {
                 // Use of `await` outside of an async context. Return `yield_expr` so that we can
@@ -860,6 +884,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         decl: &FnDecl,
         body: &Expr,
         fn_decl_span: Span,
+        fn_arg_span: Span,
     ) -> hir::ExprKind<'hir> {
         let (binder_clause, generic_params) = self.lower_closure_binder(binder);
 
@@ -880,15 +905,17 @@ impl<'hir> LoweringContext<'_, 'hir> {
 
         let bound_generic_params = self.lower_lifetime_binder(closure_id, generic_params);
         // Lower outside new scope to preserve `is_in_loop_condition`.
-        let fn_decl = self.lower_fn_decl(decl, None, fn_decl_span, FnDeclKind::Closure, None);
+        let fn_decl = self.lower_fn_decl(decl, closure_id, fn_decl_span, FnDeclKind::Closure, None);
 
         let c = self.arena.alloc(hir::Closure {
+            def_id: self.local_def_id(closure_id),
             binder: binder_clause,
             capture_clause,
             bound_generic_params,
             fn_decl,
             body: body_id,
             fn_decl_span: self.lower_span(fn_decl_span),
+            fn_arg_span: Some(self.lower_span(fn_arg_span)),
             movability: generator_option,
         });
 
@@ -927,8 +954,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
     ) -> (hir::ClosureBinder, &'c [GenericParam]) {
         let (binder, params) = match binder {
             ClosureBinder::NotPresent => (hir::ClosureBinder::Default, &[][..]),
-            &ClosureBinder::For { span, ref generic_params } => {
-                let span = self.lower_span(span);
+            ClosureBinder::For { span, generic_params } => {
+                let span = self.lower_span(*span);
                 (hir::ClosureBinder::For { span }, &**generic_params)
             }
         };
@@ -945,6 +972,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         decl: &FnDecl,
         body: &Expr,
         fn_decl_span: Span,
+        fn_arg_span: Span,
     ) -> hir::ExprKind<'hir> {
         if let &ClosureBinder::For { span, .. } = binder {
             self.tcx.sess.emit_err(NotSupportedForLifetimeBinderAsyncClosure { span });
@@ -962,19 +990,27 @@ impl<'hir> LoweringContext<'_, 'hir> {
             }
 
             // Transform `async |x: u8| -> X { ... }` into
-            // `|x: u8| future_from_generator(|| -> X { ... })`.
+            // `|x: u8| identity_future(|| -> X { ... })`.
             let body_id = this.lower_fn_body(&outer_decl, |this| {
-                let async_ret_ty =
-                    if let FnRetTy::Ty(ty) = &decl.output { Some(ty.clone()) } else { None };
+                let async_ret_ty = if let FnRetTy::Ty(ty) = &decl.output {
+                    let itctx = ImplTraitContext::Disallowed(ImplTraitPosition::AsyncBlock);
+                    Some(hir::FnRetTy::Return(this.lower_ty(&ty, &itctx)))
+                } else {
+                    None
+                };
+
                 let async_body = this.make_async_expr(
                     capture_clause,
+                    // FIXME(nbdd0121): This should also use a proper HIR id so `#[track_caller]`
+                    // can be applied on async closures as well.
+                    None,
                     inner_closure_id,
                     async_ret_ty,
                     body.span,
                     hir::AsyncGeneratorKind::Closure,
                     |this| this.with_new_scopes(|this| this.lower_expr_mut(body)),
                 );
-                this.expr(fn_decl_span, async_body, AttrVec::new())
+                this.expr(fn_decl_span, async_body)
             });
             body_id
         });
@@ -984,15 +1020,17 @@ impl<'hir> LoweringContext<'_, 'hir> {
         // have to conserve the state of being inside a loop condition for the
         // closure argument types.
         let fn_decl =
-            self.lower_fn_decl(&outer_decl, None, fn_decl_span, FnDeclKind::Closure, None);
+            self.lower_fn_decl(&outer_decl, closure_id, fn_decl_span, FnDeclKind::Closure, None);
 
         let c = self.arena.alloc(hir::Closure {
+            def_id: self.local_def_id(closure_id),
             binder: binder_clause,
             capture_clause,
             bound_generic_params,
             fn_decl,
             body,
             fn_decl_span: self.lower_span(fn_decl_span),
+            fn_arg_span: Some(self.lower_span(fn_arg_span)),
             movability: None,
         });
         hir::ExprKind::Closure(c)
@@ -1065,7 +1103,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
     fn extract_tuple_struct_path<'a>(
         &mut self,
         expr: &'a Expr,
-    ) -> Option<(&'a Option<QSelf>, &'a Path)> {
+    ) -> Option<(&'a Option<AstP<QSelf>>, &'a Path)> {
         if let ExprKind::Path(qself, path) = &expr.kind {
             // Does the path resolve to something disallowed in a tuple struct/variant pattern?
             if let Some(partial_res) = self.resolver.get_partial_res(expr.id) {
@@ -1085,7 +1123,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
     fn extract_unit_struct_path<'a>(
         &mut self,
         expr: &'a Expr,
-    ) -> Option<(&'a Option<QSelf>, &'a Path)> {
+    ) -> Option<(&'a Option<AstP<QSelf>>, &'a Path)> {
         if let ExprKind::Path(qself, path) = &expr.kind {
             // Does the path resolve to something disallowed in a unit struct/variant pattern?
             if let Some(partial_res) = self.resolver.get_partial_res(expr.id) {
@@ -1232,7 +1270,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         let ident = self.expr_ident(lhs.span, ident, binding);
         let assign =
             hir::ExprKind::Assign(self.lower_expr(lhs), ident, self.lower_span(eq_sign_span));
-        let expr = self.expr(lhs.span, assign, AttrVec::new());
+        let expr = self.expr(lhs.span, assign);
         assignments.push(self.stmt_expr(lhs.span, expr));
         pat
     }
@@ -1273,8 +1311,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         let e2 = self.lower_expr_mut(e2);
         let fn_path =
             hir::QPath::LangItem(hir::LangItem::RangeInclusiveNew, self.lower_span(span), None);
-        let fn_expr =
-            self.arena.alloc(self.expr(span, hir::ExprKind::Path(fn_path), AttrVec::new()));
+        let fn_expr = self.arena.alloc(self.expr(span, hir::ExprKind::Path(fn_path)));
         hir::ExprKind::Call(fn_expr, arena_vec![self; e1, e2])
     }
 
@@ -1446,8 +1483,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
 
         // `None => break`
         let none_arm = {
-            let break_expr =
-                self.with_loop_scope(e.id, |this| this.expr_break_alloc(for_span, AttrVec::new()));
+            let break_expr = self.with_loop_scope(e.id, |this| this.expr_break_alloc(for_span));
             let pat = self.pat_none(for_span);
             self.arm(pat, break_expr)
         };
@@ -1456,7 +1492,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         let some_arm = {
             let some_pat = self.pat_some(pat_span, pat);
             let body_block = self.with_loop_scope(e.id, |this| this.lower_block(body, false));
-            let body_expr = self.arena.alloc(self.expr_block(body_block, AttrVec::new()));
+            let body_expr = self.arena.alloc(self.expr_block(body_block));
             self.arm(some_pat, body_expr)
         };
 
@@ -1519,7 +1555,9 @@ impl<'hir> LoweringContext<'_, 'hir> {
         // surrounding scope of the `match` since the `match` is not a terminating scope.
         //
         // Also, add the attributes to the outer returned expr node.
-        self.expr_drop_temps_mut(for_span, match_expr, e.attrs.clone())
+        let expr = self.expr_drop_temps_mut(for_span, match_expr);
+        self.lower_attrs(expr.hir_id, &e.attrs);
+        expr
     }
 
     /// Desugar `ExprKind::Try` from: `<expr>?` into:
@@ -1561,28 +1599,21 @@ impl<'hir> LoweringContext<'_, 'hir> {
         };
 
         // `#[allow(unreachable_code)]`
-        let attr = {
-            // `allow(unreachable_code)`
-            let allow = {
-                let allow_ident = Ident::new(sym::allow, self.lower_span(span));
-                let uc_ident = Ident::new(sym::unreachable_code, self.lower_span(span));
-                let uc_nested = attr::mk_nested_word_item(uc_ident);
-                attr::mk_list_item(allow_ident, vec![uc_nested])
-            };
-            attr::mk_attr_outer(&self.tcx.sess.parse_sess.attr_id_generator, allow)
-        };
+        let attr = attr::mk_attr_nested_word(
+            &self.tcx.sess.parse_sess.attr_id_generator,
+            AttrStyle::Outer,
+            sym::allow,
+            sym::unreachable_code,
+            self.lower_span(span),
+        );
         let attrs: AttrVec = thin_vec![attr];
 
         // `ControlFlow::Continue(val) => #[allow(unreachable_code)] val,`
         let continue_arm = {
             let val_ident = Ident::with_dummy_span(sym::val);
             let (val_pat, val_pat_nid) = self.pat_ident(span, val_ident);
-            let val_expr = self.arena.alloc(self.expr_ident_with_attrs(
-                span,
-                val_ident,
-                val_pat_nid,
-                attrs.clone(),
-            ));
+            let val_expr = self.expr_ident(span, val_ident, val_pat_nid);
+            self.lower_attrs(val_expr.hir_id, &attrs);
             let continue_pat = self.pat_cf_continue(unstable_span, val_pat);
             self.arm(continue_pat, val_expr)
         };
@@ -1608,15 +1639,11 @@ impl<'hir> LoweringContext<'_, 'hir> {
                         hir::Destination { label: None, target_id },
                         Some(from_residual_expr),
                     ),
-                    attrs,
                 ))
             } else {
-                self.arena.alloc(self.expr(
-                    try_span,
-                    hir::ExprKind::Ret(Some(from_residual_expr)),
-                    attrs,
-                ))
+                self.arena.alloc(self.expr(try_span, hir::ExprKind::Ret(Some(from_residual_expr))))
             };
+            self.lower_attrs(ret_expr.hir_id, &attrs);
 
             let break_pat = self.pat_cf_break(try_span, residual_local);
             self.arm(break_pat, ret_expr)
@@ -1681,18 +1708,16 @@ impl<'hir> LoweringContext<'_, 'hir> {
         &mut self,
         span: Span,
         expr: &'hir hir::Expr<'hir>,
-        attrs: AttrVec,
     ) -> &'hir hir::Expr<'hir> {
-        self.arena.alloc(self.expr_drop_temps_mut(span, expr, attrs))
+        self.arena.alloc(self.expr_drop_temps_mut(span, expr))
     }
 
     pub(super) fn expr_drop_temps_mut(
         &mut self,
         span: Span,
         expr: &'hir hir::Expr<'hir>,
-        attrs: AttrVec,
     ) -> hir::Expr<'hir> {
-        self.expr(span, hir::ExprKind::DropTemps(expr), attrs)
+        self.expr(span, hir::ExprKind::DropTemps(expr))
     }
 
     fn expr_match(
@@ -1702,29 +1727,25 @@ impl<'hir> LoweringContext<'_, 'hir> {
         arms: &'hir [hir::Arm<'hir>],
         source: hir::MatchSource,
     ) -> hir::Expr<'hir> {
-        self.expr(span, hir::ExprKind::Match(arg, arms, source), AttrVec::new())
+        self.expr(span, hir::ExprKind::Match(arg, arms, source))
     }
 
-    fn expr_break(&mut self, span: Span, attrs: AttrVec) -> hir::Expr<'hir> {
+    fn expr_break(&mut self, span: Span) -> hir::Expr<'hir> {
         let expr_break = hir::ExprKind::Break(self.lower_loop_destination(None), None);
-        self.expr(span, expr_break, attrs)
+        self.expr(span, expr_break)
     }
 
-    fn expr_break_alloc(&mut self, span: Span, attrs: AttrVec) -> &'hir hir::Expr<'hir> {
-        let expr_break = self.expr_break(span, attrs);
+    fn expr_break_alloc(&mut self, span: Span) -> &'hir hir::Expr<'hir> {
+        let expr_break = self.expr_break(span);
         self.arena.alloc(expr_break)
     }
 
     fn expr_mut_addr_of(&mut self, span: Span, e: &'hir hir::Expr<'hir>) -> hir::Expr<'hir> {
-        self.expr(
-            span,
-            hir::ExprKind::AddrOf(hir::BorrowKind::Ref, hir::Mutability::Mut, e),
-            AttrVec::new(),
-        )
+        self.expr(span, hir::ExprKind::AddrOf(hir::BorrowKind::Ref, hir::Mutability::Mut, e))
     }
 
     fn expr_unit(&mut self, sp: Span) -> &'hir hir::Expr<'hir> {
-        self.arena.alloc(self.expr(sp, hir::ExprKind::Tup(&[]), AttrVec::new()))
+        self.arena.alloc(self.expr(sp, hir::ExprKind::Tup(&[])))
     }
 
     fn expr_call_mut(
@@ -1733,7 +1754,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         e: &'hir hir::Expr<'hir>,
         args: &'hir [hir::Expr<'hir>],
     ) -> hir::Expr<'hir> {
-        self.expr(span, hir::ExprKind::Call(e, args), AttrVec::new())
+        self.expr(span, hir::ExprKind::Call(e, args))
     }
 
     fn expr_call(
@@ -1752,8 +1773,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         args: &'hir [hir::Expr<'hir>],
         hir_id: Option<hir::HirId>,
     ) -> hir::Expr<'hir> {
-        let path =
-            self.arena.alloc(self.expr_lang_item_path(span, lang_item, AttrVec::new(), hir_id));
+        let path = self.arena.alloc(self.expr_lang_item_path(span, lang_item, hir_id));
         self.expr_call_mut(span, path, args)
     }
 
@@ -1771,13 +1791,11 @@ impl<'hir> LoweringContext<'_, 'hir> {
         &mut self,
         span: Span,
         lang_item: hir::LangItem,
-        attrs: AttrVec,
         hir_id: Option<hir::HirId>,
     ) -> hir::Expr<'hir> {
         self.expr(
             span,
             hir::ExprKind::Path(hir::QPath::LangItem(lang_item, self.lower_span(span), hir_id)),
-            attrs,
         )
     }
 
@@ -1792,19 +1810,9 @@ impl<'hir> LoweringContext<'_, 'hir> {
 
     pub(super) fn expr_ident_mut(
         &mut self,
-        sp: Span,
-        ident: Ident,
-        binding: hir::HirId,
-    ) -> hir::Expr<'hir> {
-        self.expr_ident_with_attrs(sp, ident, binding, AttrVec::new())
-    }
-
-    fn expr_ident_with_attrs(
-        &mut self,
         span: Span,
         ident: Ident,
         binding: hir::HirId,
-        attrs: AttrVec,
     ) -> hir::Expr<'hir> {
         let hir_id = self.next_id();
         let res = Res::Local(binding);
@@ -1817,7 +1825,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
             }),
         ));
 
-        self.expr(span, expr_path, attrs)
+        self.expr(span, expr_path)
     }
 
     fn expr_unsafe(&mut self, expr: &'hir hir::Expr<'hir>) -> hir::Expr<'hir> {
@@ -1836,32 +1844,21 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 }),
                 None,
             ),
-            AttrVec::new(),
         )
     }
 
     fn expr_block_empty(&mut self, span: Span) -> &'hir hir::Expr<'hir> {
         let blk = self.block_all(span, &[], None);
-        let expr = self.expr_block(blk, AttrVec::new());
+        let expr = self.expr_block(blk);
         self.arena.alloc(expr)
     }
 
-    pub(super) fn expr_block(
-        &mut self,
-        b: &'hir hir::Block<'hir>,
-        attrs: AttrVec,
-    ) -> hir::Expr<'hir> {
-        self.expr(b.span, hir::ExprKind::Block(b, None), attrs)
+    pub(super) fn expr_block(&mut self, b: &'hir hir::Block<'hir>) -> hir::Expr<'hir> {
+        self.expr(b.span, hir::ExprKind::Block(b, None))
     }
 
-    pub(super) fn expr(
-        &mut self,
-        span: Span,
-        kind: hir::ExprKind<'hir>,
-        attrs: AttrVec,
-    ) -> hir::Expr<'hir> {
+    pub(super) fn expr(&mut self, span: Span, kind: hir::ExprKind<'hir>) -> hir::Expr<'hir> {
         let hir_id = self.next_id();
-        self.lower_attrs(hir_id, &attrs);
         hir::Expr { hir_id, kind, span: self.lower_span(span) }
     }
 
diff --git a/compiler/rustc_ast_lowering/src/index.rs b/compiler/rustc_ast_lowering/src/index.rs
index f1851d7b4..fe0bd4381 100644
--- a/compiler/rustc_ast_lowering/src/index.rs
+++ b/compiler/rustc_ast_lowering/src/index.rs
@@ -77,7 +77,7 @@ impl<'a, 'hir> NodeCollector<'a, 'hir> {
             if hir_id.owner != self.owner {
                 span_bug!(
                     span,
-                    "inconsistent DepNode at `{:?}` for `{:?}`: \
+                    "inconsistent HirId at `{:?}` for `{:?}`: \
                      current_dep_node_owner={} ({:?}), hir_id.owner={} ({:?})",
                     self.source_map.span_to_diagnostic_string(span),
                     node,
@@ -145,7 +145,7 @@ impl<'a, 'hir> Visitor<'hir> for NodeCollector<'a, 'hir> {
     fn visit_item(&mut self, i: &'hir Item<'hir>) {
         debug_assert_eq!(i.owner_id, self.owner);
         self.with_parent(i.hir_id(), |this| {
-            if let ItemKind::Struct(ref struct_def, _) = i.kind {
+            if let ItemKind::Struct(struct_def, _) = &i.kind {
                 // If this is a tuple or unit-like struct, register the constructor.
                 if let Some(ctor_hir_id) = struct_def.ctor_hir_id() {
                     this.insert(i.span, ctor_hir_id, Node::Ctor(struct_def));
@@ -303,12 +303,12 @@ impl<'a, 'hir> Visitor<'hir> for NodeCollector<'a, 'hir> {
     }
 
     fn visit_lifetime(&mut self, lifetime: &'hir Lifetime) {
-        self.insert(lifetime.span, lifetime.hir_id, Node::Lifetime(lifetime));
+        self.insert(lifetime.ident.span, lifetime.hir_id, Node::Lifetime(lifetime));
     }
 
     fn visit_variant(&mut self, v: &'hir Variant<'hir>) {
-        self.insert(v.span, v.id, Node::Variant(v));
-        self.with_parent(v.id, |this| {
+        self.insert(v.span, v.hir_id, Node::Variant(v));
+        self.with_parent(v.hir_id, |this| {
             // Register the constructor of this variant.
             if let Some(ctor_hir_id) = v.data.ctor_hir_id() {
                 this.insert(v.span, ctor_hir_id, Node::Ctor(&v.data));
diff --git a/compiler/rustc_ast_lowering/src/item.rs b/compiler/rustc_ast_lowering/src/item.rs
index 76316a574..d73d6d391 100644
--- a/compiler/rustc_ast_lowering/src/item.rs
+++ b/compiler/rustc_ast_lowering/src/item.rs
@@ -6,7 +6,6 @@ use super::{FnDeclKind, LoweringContext, ParamMode};
 use rustc_ast::ptr::P;
 use rustc_ast::visit::AssocCtxt;
 use rustc_ast::*;
-use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::sorted_map::SortedMap;
 use rustc_hir as hir;
 use rustc_hir::def::{DefKind, Res};
@@ -20,8 +19,7 @@ use rustc_span::symbol::{kw, sym, Ident};
 use rustc_span::{Span, Symbol};
 use rustc_target::spec::abi;
 use smallvec::{smallvec, SmallVec};
-
-use std::iter;
+use thin_vec::ThinVec;
 
 pub(super) struct ItemLowerer<'a, 'hir> {
     pub(super) tcx: TyCtxt<'hir>,
@@ -67,7 +65,7 @@ impl<'a, 'hir> ItemLowerer<'a, 'hir> {
             // HirId handling.
             bodies: Vec::new(),
             attrs: SortedMap::default(),
-            children: FxHashMap::default(),
+            children: Vec::default(),
             current_hir_id_owner: hir::CRATE_OWNER_ID,
             item_local_id_counter: hir::ItemLocalId::new(0),
             node_id_to_local_id: Default::default(),
@@ -86,7 +84,7 @@ impl<'a, 'hir> ItemLowerer<'a, 'hir> {
             impl_trait_defs: Vec::new(),
             impl_trait_bounds: Vec::new(),
             allow_try_trait: Some([sym::try_trait_v2, sym::yeet_desugar_details][..].into()),
-            allow_gen_future: Some([sym::gen_future][..].into()),
+            allow_gen_future: Some([sym::gen_future, sym::closure_track_caller][..].into()),
             allow_into_future: Some([sym::into_future][..].into()),
             generics_def_id_map: Default::default(),
         };
@@ -143,7 +141,7 @@ impl<'a, 'hir> ItemLowerer<'a, 'hir> {
             // This is used to track which lifetimes have already been defined,
             // and which need to be replicated when lowering an async fn.
             match parent_hir.node().expect_item().kind {
-                hir::ItemKind::Impl(hir::Impl { ref of_trait, .. }) => {
+                hir::ItemKind::Impl(hir::Impl { of_trait, .. }) => {
                     lctx.is_in_trait_impl = of_trait.is_some();
                 }
                 _ => {}
@@ -179,37 +177,23 @@ impl<'hir> LoweringContext<'_, 'hir> {
     pub(super) fn lower_item_ref(&mut self, i: &Item) -> SmallVec<[hir::ItemId; 1]> {
         let mut node_ids =
             smallvec![hir::ItemId { owner_id: hir::OwnerId { def_id: self.local_def_id(i.id) } }];
-        if let ItemKind::Use(ref use_tree) = &i.kind {
-            self.lower_item_id_use_tree(use_tree, i.id, &mut node_ids);
+        if let ItemKind::Use(use_tree) = &i.kind {
+            self.lower_item_id_use_tree(use_tree, &mut node_ids);
         }
         node_ids
     }
 
-    fn lower_item_id_use_tree(
-        &mut self,
-        tree: &UseTree,
-        base_id: NodeId,
-        vec: &mut SmallVec<[hir::ItemId; 1]>,
-    ) {
-        match tree.kind {
-            UseTreeKind::Nested(ref nested_vec) => {
+    fn lower_item_id_use_tree(&mut self, tree: &UseTree, vec: &mut SmallVec<[hir::ItemId; 1]>) {
+        match &tree.kind {
+            UseTreeKind::Nested(nested_vec) => {
                 for &(ref nested, id) in nested_vec {
                     vec.push(hir::ItemId {
                         owner_id: hir::OwnerId { def_id: self.local_def_id(id) },
                     });
-                    self.lower_item_id_use_tree(nested, id, vec);
-                }
-            }
-            UseTreeKind::Glob => {}
-            UseTreeKind::Simple(_, id1, id2) => {
-                for (_, &id) in
-                    iter::zip(self.expect_full_res_from_use(base_id).skip(1), &[id1, id2])
-                {
-                    vec.push(hir::ItemId {
-                        owner_id: hir::OwnerId { def_id: self.local_def_id(id) },
-                    });
+                    self.lower_item_id_use_tree(nested, vec);
                 }
             }
+            UseTreeKind::Simple(..) | UseTreeKind::Glob => {}
         }
     }
 
@@ -239,26 +223,26 @@ impl<'hir> LoweringContext<'_, 'hir> {
         vis_span: Span,
         i: &ItemKind,
     ) -> hir::ItemKind<'hir> {
-        match *i {
-            ItemKind::ExternCrate(orig_name) => hir::ItemKind::ExternCrate(orig_name),
-            ItemKind::Use(ref use_tree) => {
+        match i {
+            ItemKind::ExternCrate(orig_name) => hir::ItemKind::ExternCrate(*orig_name),
+            ItemKind::Use(use_tree) => {
                 // Start with an empty prefix.
-                let prefix = Path { segments: vec![], span: use_tree.span, tokens: None };
+                let prefix = Path { segments: ThinVec::new(), span: use_tree.span, tokens: None };
 
                 self.lower_use_tree(use_tree, &prefix, id, vis_span, ident, attrs)
             }
-            ItemKind::Static(ref t, m, ref e) => {
+            ItemKind::Static(t, m, e) => {
                 let (ty, body_id) = self.lower_const_item(t, span, e.as_deref());
-                hir::ItemKind::Static(ty, m, body_id)
+                hir::ItemKind::Static(ty, *m, body_id)
             }
-            ItemKind::Const(_, ref t, ref e) => {
+            ItemKind::Const(_, t, e) => {
                 let (ty, body_id) = self.lower_const_item(t, span, e.as_deref());
                 hir::ItemKind::Const(ty, body_id)
             }
             ItemKind::Fn(box Fn {
-                sig: FnSig { ref decl, header, span: fn_sig_span },
-                ref generics,
-                ref body,
+                sig: FnSig { decl, header, span: fn_sig_span },
+                generics,
+                body,
                 ..
             }) => {
                 self.with_new_scopes(|this| {
@@ -269,43 +253,41 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     // only cares about the input argument patterns in the function
                     // declaration (decl), not the return types.
                     let asyncness = header.asyncness;
-                    let body_id =
-                        this.lower_maybe_async_body(span, &decl, asyncness, body.as_deref());
+                    let body_id = this.lower_maybe_async_body(
+                        span,
+                        hir_id,
+                        &decl,
+                        asyncness,
+                        body.as_deref(),
+                    );
 
                     let mut itctx = ImplTraitContext::Universal;
                     let (generics, decl) = this.lower_generics(generics, id, &mut itctx, |this| {
                         let ret_id = asyncness.opt_return_id();
-                        this.lower_fn_decl(&decl, Some(id), fn_sig_span, FnDeclKind::Fn, ret_id)
+                        this.lower_fn_decl(&decl, id, *fn_sig_span, FnDeclKind::Fn, ret_id)
                     });
                     let sig = hir::FnSig {
                         decl,
-                        header: this.lower_fn_header(header),
-                        span: this.lower_span(fn_sig_span),
+                        header: this.lower_fn_header(*header),
+                        span: this.lower_span(*fn_sig_span),
                     };
                     hir::ItemKind::Fn(sig, generics, body_id)
                 })
             }
-            ItemKind::Mod(_, ref mod_kind) => match mod_kind {
+            ItemKind::Mod(_, mod_kind) => match mod_kind {
                 ModKind::Loaded(items, _, spans) => {
                     hir::ItemKind::Mod(self.lower_mod(items, spans))
                 }
                 ModKind::Unloaded => panic!("`mod` items should have been loaded by now"),
             },
-            ItemKind::ForeignMod(ref fm) => hir::ItemKind::ForeignMod {
+            ItemKind::ForeignMod(fm) => hir::ItemKind::ForeignMod {
                 abi: fm.abi.map_or(abi::Abi::FALLBACK, |abi| self.lower_abi(abi)),
                 items: self
                     .arena
                     .alloc_from_iter(fm.items.iter().map(|x| self.lower_foreign_item_ref(x))),
             },
-            ItemKind::GlobalAsm(ref asm) => {
-                hir::ItemKind::GlobalAsm(self.lower_inline_asm(span, asm))
-            }
-            ItemKind::TyAlias(box TyAlias {
-                ref generics,
-                where_clauses,
-                ty: Some(ref ty),
-                ..
-            }) => {
+            ItemKind::GlobalAsm(asm) => hir::ItemKind::GlobalAsm(self.lower_inline_asm(span, asm)),
+            ItemKind::TyAlias(box TyAlias { generics, where_clauses, ty: Some(ty), .. }) => {
                 // We lower
                 //
                 // type Foo = impl Trait
@@ -315,7 +297,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 // type Foo = Foo1
                 // opaque type Foo1: Trait
                 let mut generics = generics.clone();
-                add_ty_alias_where_clause(&mut generics, where_clauses, true);
+                add_ty_alias_where_clause(&mut generics, *where_clauses, true);
                 let (generics, ty) = self.lower_generics(
                     &generics,
                     id,
@@ -324,9 +306,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 );
                 hir::ItemKind::TyAlias(ty, generics)
             }
-            ItemKind::TyAlias(box TyAlias {
-                ref generics, ref where_clauses, ty: None, ..
-            }) => {
+            ItemKind::TyAlias(box TyAlias { generics, where_clauses, ty: None, .. }) => {
                 let mut generics = generics.clone();
                 add_ty_alias_where_clause(&mut generics, *where_clauses, true);
                 let (generics, ty) = self.lower_generics(
@@ -337,7 +317,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 );
                 hir::ItemKind::TyAlias(ty, generics)
             }
-            ItemKind::Enum(ref enum_definition, ref generics) => {
+            ItemKind::Enum(enum_definition, generics) => {
                 let (generics, variants) = self.lower_generics(
                     generics,
                     id,
@@ -350,7 +330,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 );
                 hir::ItemKind::Enum(hir::EnumDef { variants }, generics)
             }
-            ItemKind::Struct(ref struct_def, ref generics) => {
+            ItemKind::Struct(struct_def, generics) => {
                 let (generics, struct_def) = self.lower_generics(
                     generics,
                     id,
@@ -359,7 +339,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 );
                 hir::ItemKind::Struct(struct_def, generics)
             }
-            ItemKind::Union(ref vdata, ref generics) => {
+            ItemKind::Union(vdata, generics) => {
                 let (generics, vdata) = self.lower_generics(
                     generics,
                     id,
@@ -373,10 +353,10 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 polarity,
                 defaultness,
                 constness,
-                generics: ref ast_generics,
-                of_trait: ref trait_ref,
-                self_ty: ref ty,
-                items: ref impl_items,
+                generics: ast_generics,
+                of_trait: trait_ref,
+                self_ty: ty,
+                items: impl_items,
             }) => {
                 // Lower the "impl header" first. This ordering is important
                 // for in-band lifetimes! Consider `'a` here:
@@ -414,30 +394,24 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 // `defaultness.has_value()` is never called for an `impl`, always `true` in order
                 // to not cause an assertion failure inside the `lower_defaultness` function.
                 let has_val = true;
-                let (defaultness, defaultness_span) = self.lower_defaultness(defaultness, has_val);
+                let (defaultness, defaultness_span) = self.lower_defaultness(*defaultness, has_val);
                 let polarity = match polarity {
                     ImplPolarity::Positive => ImplPolarity::Positive,
-                    ImplPolarity::Negative(s) => ImplPolarity::Negative(self.lower_span(s)),
+                    ImplPolarity::Negative(s) => ImplPolarity::Negative(self.lower_span(*s)),
                 };
                 hir::ItemKind::Impl(self.arena.alloc(hir::Impl {
-                    unsafety: self.lower_unsafety(unsafety),
+                    unsafety: self.lower_unsafety(*unsafety),
                     polarity,
                     defaultness,
                     defaultness_span,
-                    constness: self.lower_constness(constness),
+                    constness: self.lower_constness(*constness),
                     generics,
                     of_trait: trait_ref,
                     self_ty: lowered_ty,
                     items: new_impl_items,
                 }))
             }
-            ItemKind::Trait(box Trait {
-                is_auto,
-                unsafety,
-                ref generics,
-                ref bounds,
-                ref items,
-            }) => {
+            ItemKind::Trait(box Trait { is_auto, unsafety, generics, bounds, items }) => {
                 let (generics, (unsafety, items, bounds)) = self.lower_generics(
                     generics,
                     id,
@@ -450,13 +424,13 @@ impl<'hir> LoweringContext<'_, 'hir> {
                         let items = this.arena.alloc_from_iter(
                             items.iter().map(|item| this.lower_trait_item_ref(item)),
                         );
-                        let unsafety = this.lower_unsafety(unsafety);
+                        let unsafety = this.lower_unsafety(*unsafety);
                         (unsafety, items, bounds)
                     },
                 );
-                hir::ItemKind::Trait(is_auto, unsafety, generics, bounds, items)
+                hir::ItemKind::Trait(*is_auto, unsafety, generics, bounds, items)
             }
-            ItemKind::TraitAlias(ref generics, ref bounds) => {
+            ItemKind::TraitAlias(generics, bounds) => {
                 let (generics, bounds) = self.lower_generics(
                     generics,
                     id,
@@ -470,10 +444,10 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 );
                 hir::ItemKind::TraitAlias(generics, bounds)
             }
-            ItemKind::MacroDef(MacroDef { ref body, macro_rules }) => {
-                let body = P(self.lower_mac_args(body));
+            ItemKind::MacroDef(MacroDef { body, macro_rules }) => {
+                let body = P(self.lower_delim_args(body));
                 let macro_kind = self.resolver.decl_macro_kind(self.local_def_id(id));
-                hir::ItemKind::Macro(ast::MacroDef { body, macro_rules }, macro_kind)
+                hir::ItemKind::Macro(ast::MacroDef { body, macro_rules: *macro_rules }, macro_kind)
             }
             ItemKind::MacCall(..) => {
                 panic!("`TyMac` should have been expanded by now")
@@ -505,7 +479,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         let segments = prefix.segments.iter().chain(path.segments.iter()).cloned().collect();
 
         match tree.kind {
-            UseTreeKind::Simple(rename, id1, id2) => {
+            UseTreeKind::Simple(rename) => {
                 *ident = tree.ident();
 
                 // First, apply the prefix to the path.
@@ -521,66 +495,16 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     }
                 }
 
-                let mut resolutions = self.expect_full_res_from_use(id).fuse();
-                // We want to return *something* from this function, so hold onto the first item
-                // for later.
-                let ret_res = self.lower_res(resolutions.next().unwrap_or(Res::Err));
-
-                // Here, we are looping over namespaces, if they exist for the definition
-                // being imported. We only handle type and value namespaces because we
-                // won't be dealing with macros in the rest of the compiler.
-                // Essentially a single `use` which imports two names is desugared into
-                // two imports.
-                for new_node_id in [id1, id2] {
-                    let new_id = self.local_def_id(new_node_id);
-                    let Some(res) = resolutions.next() else {
-                        // Associate an HirId to both ids even if there is no resolution.
-                        let _old = self.children.insert(
-                            new_id,
-                            hir::MaybeOwner::NonOwner(hir::HirId::make_owner(new_id)),
-                        );
-                        debug_assert!(_old.is_none());
-                        continue;
-                    };
-                    let ident = *ident;
-                    let mut path = path.clone();
-                    for seg in &mut path.segments {
-                        // Give the cloned segment the same resolution information
-                        // as the old one (this is needed for stability checking).
-                        let new_id = self.next_node_id();
-                        self.resolver.clone_res(seg.id, new_id);
-                        seg.id = new_id;
-                    }
-                    let span = path.span;
-
-                    self.with_hir_id_owner(new_node_id, |this| {
-                        let res = this.lower_res(res);
-                        let path = this.lower_path_extra(res, &path, ParamMode::Explicit);
-                        let kind = hir::ItemKind::Use(path, hir::UseKind::Single);
-                        if let Some(attrs) = attrs {
-                            this.attrs.insert(hir::ItemLocalId::new(0), attrs);
-                        }
-
-                        let item = hir::Item {
-                            owner_id: hir::OwnerId { def_id: new_id },
-                            ident: this.lower_ident(ident),
-                            kind,
-                            vis_span,
-                            span: this.lower_span(span),
-                        };
-                        hir::OwnerNode::Item(this.arena.alloc(item))
-                    });
-                }
-
-                let path = self.lower_path_extra(ret_res, &path, ParamMode::Explicit);
+                let res =
+                    self.expect_full_res_from_use(id).map(|res| self.lower_res(res)).collect();
+                let path = self.lower_use_path(res, &path, ParamMode::Explicit);
                 hir::ItemKind::Use(path, hir::UseKind::Single)
             }
             UseTreeKind::Glob => {
-                let path = self.lower_path(
-                    id,
-                    &Path { segments, span: path.span, tokens: None },
-                    ParamMode::Explicit,
-                );
+                let res = self.expect_full_res(id);
+                let res = smallvec![self.lower_res(res)];
+                let path = Path { segments, span: path.span, tokens: None };
+                let path = self.lower_use_path(res, &path, ParamMode::Explicit);
                 hir::ItemKind::Use(path, hir::UseKind::Glob)
             }
             UseTreeKind::Nested(ref trees) => {
@@ -650,9 +574,9 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     });
                 }
 
-                let res = self.expect_full_res_from_use(id).next().unwrap_or(Res::Err);
-                let res = self.lower_res(res);
-                let path = self.lower_path_extra(res, &prefix, ParamMode::Explicit);
+                let res =
+                    self.expect_full_res_from_use(id).map(|res| self.lower_res(res)).collect();
+                let path = self.lower_use_path(res, &prefix, ParamMode::Explicit);
                 hir::ItemKind::Use(path, hir::UseKind::ListStem)
             }
         }
@@ -665,8 +589,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
         let item = hir::ForeignItem {
             owner_id,
             ident: self.lower_ident(i.ident),
-            kind: match i.kind {
-                ForeignItemKind::Fn(box Fn { ref sig, ref generics, .. }) => {
+            kind: match &i.kind {
+                ForeignItemKind::Fn(box Fn { sig, generics, .. }) => {
                     let fdec = &sig.decl;
                     let mut itctx = ImplTraitContext::Universal;
                     let (generics, (fn_dec, fn_args)) =
@@ -675,7 +599,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                                 // Disallow `impl Trait` in foreign items.
                                 this.lower_fn_decl(
                                     fdec,
-                                    None,
+                                    i.id,
                                     sig.span,
                                     FnDeclKind::ExternFn,
                                     None,
@@ -686,10 +610,10 @@ impl<'hir> LoweringContext<'_, 'hir> {
 
                     hir::ForeignItemKind::Fn(fn_dec, fn_args, generics)
                 }
-                ForeignItemKind::Static(ref t, m, _) => {
+                ForeignItemKind::Static(t, m, _) => {
                     let ty =
                         self.lower_ty(t, &ImplTraitContext::Disallowed(ImplTraitPosition::Type));
-                    hir::ForeignItemKind::Static(ty, m)
+                    hir::ForeignItemKind::Static(ty, *m)
                 }
                 ForeignItemKind::TyAlias(..) => hir::ForeignItemKind::Type,
                 ForeignItemKind::MacCall(_) => panic!("macro shouldn't exist here"),
@@ -709,11 +633,12 @@ impl<'hir> LoweringContext<'_, 'hir> {
     }
 
     fn lower_variant(&mut self, v: &Variant) -> hir::Variant<'hir> {
-        let id = self.lower_node_id(v.id);
-        self.lower_attrs(id, &v.attrs);
+        let hir_id = self.lower_node_id(v.id);
+        self.lower_attrs(hir_id, &v.attrs);
         hir::Variant {
-            id,
-            data: self.lower_variant_data(id, &v.data),
+            hir_id,
+            def_id: self.local_def_id(v.id),
+            data: self.lower_variant_data(hir_id, &v.data),
             disr_expr: v.disr_expr.as_ref().map(|e| self.lower_anon_const(e)),
             ident: self.lower_ident(v.ident),
             span: self.lower_span(v.span),
@@ -725,32 +650,33 @@ impl<'hir> LoweringContext<'_, 'hir> {
         parent_id: hir::HirId,
         vdata: &VariantData,
     ) -> hir::VariantData<'hir> {
-        match *vdata {
-            VariantData::Struct(ref fields, recovered) => hir::VariantData::Struct(
+        match vdata {
+            VariantData::Struct(fields, recovered) => hir::VariantData::Struct(
                 self.arena
                     .alloc_from_iter(fields.iter().enumerate().map(|f| self.lower_field_def(f))),
-                recovered,
+                *recovered,
             ),
-            VariantData::Tuple(ref fields, id) => {
-                let ctor_id = self.lower_node_id(id);
+            VariantData::Tuple(fields, id) => {
+                let ctor_id = self.lower_node_id(*id);
                 self.alias_attrs(ctor_id, parent_id);
                 hir::VariantData::Tuple(
                     self.arena.alloc_from_iter(
                         fields.iter().enumerate().map(|f| self.lower_field_def(f)),
                     ),
                     ctor_id,
+                    self.local_def_id(*id),
                 )
             }
             VariantData::Unit(id) => {
-                let ctor_id = self.lower_node_id(id);
+                let ctor_id = self.lower_node_id(*id);
                 self.alias_attrs(ctor_id, parent_id);
-                hir::VariantData::Unit(ctor_id)
+                hir::VariantData::Unit(ctor_id, self.local_def_id(*id))
             }
         }
     }
 
     fn lower_field_def(&mut self, (index, f): (usize, &FieldDef)) -> hir::FieldDef<'hir> {
-        let ty = if let TyKind::Path(ref qself, ref path) = f.ty.kind {
+        let ty = if let TyKind::Path(qself, path) = &f.ty.kind {
             let t = self.lower_path_ty(
                 &f.ty,
                 qself,
@@ -767,6 +693,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         hir::FieldDef {
             span: self.lower_span(f.span),
             hir_id,
+            def_id: self.local_def_id(f.id),
             ident: match f.ident {
                 Some(ident) => self.lower_ident(ident),
                 // FIXME(jseyfried): positional field hygiene.
@@ -779,15 +706,16 @@ impl<'hir> LoweringContext<'_, 'hir> {
 
     fn lower_trait_item(&mut self, i: &AssocItem) -> &'hir hir::TraitItem<'hir> {
         let hir_id = self.lower_node_id(i.id);
+        self.lower_attrs(hir_id, &i.attrs);
         let trait_item_def_id = hir_id.expect_owner();
 
-        let (generics, kind, has_default) = match i.kind {
-            AssocItemKind::Const(_, ref ty, ref default) => {
+        let (generics, kind, has_default) = match &i.kind {
+            AssocItemKind::Const(_, ty, default) => {
                 let ty = self.lower_ty(ty, &ImplTraitContext::Disallowed(ImplTraitPosition::Type));
                 let body = default.as_ref().map(|x| self.lower_const_body(i.span, Some(x)));
                 (hir::Generics::empty(), hir::TraitItemKind::Const(ty, body), body.is_some())
             }
-            AssocItemKind::Fn(box Fn { ref sig, ref generics, body: None, .. }) => {
+            AssocItemKind::Fn(box Fn { sig, generics, body: None, .. }) => {
                 let asyncness = sig.header.asyncness;
                 let names = self.lower_fn_params_to_names(&sig.decl);
                 let (generics, sig) = self.lower_method_sig(
@@ -799,10 +727,10 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 );
                 (generics, hir::TraitItemKind::Fn(sig, hir::TraitFn::Required(names)), false)
             }
-            AssocItemKind::Fn(box Fn { ref sig, ref generics, body: Some(ref body), .. }) => {
+            AssocItemKind::Fn(box Fn { sig, generics, body: Some(body), .. }) => {
                 let asyncness = sig.header.asyncness;
                 let body_id =
-                    self.lower_maybe_async_body(i.span, &sig.decl, asyncness, Some(&body));
+                    self.lower_maybe_async_body(i.span, hir_id, &sig.decl, asyncness, Some(&body));
                 let (generics, sig) = self.lower_method_sig(
                     generics,
                     sig,
@@ -812,15 +740,9 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 );
                 (generics, hir::TraitItemKind::Fn(sig, hir::TraitFn::Provided(body_id)), true)
             }
-            AssocItemKind::Type(box TyAlias {
-                ref generics,
-                where_clauses,
-                ref bounds,
-                ref ty,
-                ..
-            }) => {
+            AssocItemKind::Type(box TyAlias { generics, where_clauses, bounds, ty, .. }) => {
                 let mut generics = generics.clone();
-                add_ty_alias_where_clause(&mut generics, where_clauses, false);
+                add_ty_alias_where_clause(&mut generics, *where_clauses, false);
                 let (generics, kind) = self.lower_generics(
                     &generics,
                     i.id,
@@ -843,7 +765,6 @@ impl<'hir> LoweringContext<'_, 'hir> {
             AssocItemKind::MacCall(..) => panic!("macro item shouldn't exist at this point"),
         };
 
-        self.lower_attrs(hir_id, &i.attrs);
         let item = hir::TraitItem {
             owner_id: trait_item_def_id,
             ident: self.lower_ident(i.ident),
@@ -875,13 +796,15 @@ impl<'hir> LoweringContext<'_, 'hir> {
 
     /// Construct `ExprKind::Err` for the given `span`.
     pub(crate) fn expr_err(&mut self, span: Span) -> hir::Expr<'hir> {
-        self.expr(span, hir::ExprKind::Err, AttrVec::new())
+        self.expr(span, hir::ExprKind::Err)
     }
 
     fn lower_impl_item(&mut self, i: &AssocItem) -> &'hir hir::ImplItem<'hir> {
         // Since `default impl` is not yet implemented, this is always true in impls.
         let has_value = true;
         let (defaultness, _) = self.lower_defaultness(i.kind.defaultness(), has_value);
+        let hir_id = self.lower_node_id(i.id);
+        self.lower_attrs(hir_id, &i.attrs);
 
         let (generics, kind) = match &i.kind {
             AssocItemKind::Const(_, ty, expr) => {
@@ -894,8 +817,13 @@ impl<'hir> LoweringContext<'_, 'hir> {
             AssocItemKind::Fn(box Fn { sig, generics, body, .. }) => {
                 self.current_item = Some(i.span);
                 let asyncness = sig.header.asyncness;
-                let body_id =
-                    self.lower_maybe_async_body(i.span, &sig.decl, asyncness, body.as_deref());
+                let body_id = self.lower_maybe_async_body(
+                    i.span,
+                    hir_id,
+                    &sig.decl,
+                    asyncness,
+                    body.as_deref(),
+                );
                 let (generics, sig) = self.lower_method_sig(
                     generics,
                     sig,
@@ -928,8 +856,6 @@ impl<'hir> LoweringContext<'_, 'hir> {
             AssocItemKind::MacCall(..) => panic!("`TyMac` should have been expanded by now"),
         };
 
-        let hir_id = self.lower_node_id(i.id);
-        self.lower_attrs(hir_id, &i.attrs);
         let item = hir::ImplItem {
             owner_id: hir_id.expect_owner(),
             ident: self.lower_ident(i.ident),
@@ -1062,6 +988,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
     fn lower_maybe_async_body(
         &mut self,
         span: Span,
+        fn_id: hir::HirId,
         decl: &FnDecl,
         asyncness: Async,
         body: Option<&Block>,
@@ -1212,6 +1139,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
 
             let async_expr = this.make_async_expr(
                 CaptureBy::Value,
+                Some(fn_id),
                 closure_id,
                 None,
                 body.span,
@@ -1223,11 +1151,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     // Transform into `drop-temps { <user-body> }`, an expression:
                     let desugared_span =
                         this.mark_span_with_reason(DesugaringKind::Async, user_body.span, None);
-                    let user_body = this.expr_drop_temps(
-                        desugared_span,
-                        this.arena.alloc(user_body),
-                        AttrVec::new(),
-                    );
+                    let user_body =
+                        this.expr_drop_temps(desugared_span, this.arena.alloc(user_body));
 
                     // As noted above, create the final block like
                     //
@@ -1244,14 +1169,11 @@ impl<'hir> LoweringContext<'_, 'hir> {
                         Some(user_body),
                     );
 
-                    this.expr_block(body, AttrVec::new())
+                    this.expr_block(body)
                 },
             );
 
-            (
-                this.arena.alloc_from_iter(parameters),
-                this.expr(body.span, async_expr, AttrVec::new()),
-            )
+            (this.arena.alloc_from_iter(parameters), this.expr(body.span, async_expr))
         })
     }
 
@@ -1266,7 +1188,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         let header = self.lower_fn_header(sig.header);
         let mut itctx = ImplTraitContext::Universal;
         let (generics, decl) = self.lower_generics(generics, id, &mut itctx, |this| {
-            this.lower_fn_decl(&sig.decl, Some(id), sig.span, kind, is_async)
+            this.lower_fn_decl(&sig.decl, id, sig.span, kind, is_async)
         });
         (generics, hir::FnSig { header, decl, span: self.lower_span(sig.span) })
     }
@@ -1352,7 +1274,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         // keep track of the Span info. Now, `add_implicitly_sized` in `AstConv` checks both param bounds and
         // where clauses for `?Sized`.
         for pred in &generics.where_clause.predicates {
-            let WherePredicate::BoundPredicate(ref bound_pred) = *pred else {
+            let WherePredicate::BoundPredicate(bound_pred) = pred else {
                 continue;
             };
             let compute_is_param = || {
@@ -1498,10 +1420,9 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 }))
             }
             GenericParamKind::Lifetime => {
-                let ident_span = self.lower_span(ident.span);
                 let ident = self.lower_ident(ident);
                 let lt_id = self.next_node_id();
-                let lifetime = self.new_named_lifetime(id, lt_id, ident_span, ident);
+                let lifetime = self.new_named_lifetime(id, lt_id, ident);
                 Some(hir::WherePredicate::RegionPredicate(hir::WhereRegionPredicate {
                     lifetime,
                     span,
@@ -1513,11 +1434,11 @@ impl<'hir> LoweringContext<'_, 'hir> {
     }
 
     fn lower_where_predicate(&mut self, pred: &WherePredicate) -> hir::WherePredicate<'hir> {
-        match *pred {
+        match pred {
             WherePredicate::BoundPredicate(WhereBoundPredicate {
-                ref bound_generic_params,
-                ref bounded_ty,
-                ref bounds,
+                bound_generic_params,
+                bounded_ty,
+                bounds,
                 span,
             }) => hir::WherePredicate::BoundPredicate(hir::WhereBoundPredicate {
                 hir_id: self.next_id(),
@@ -1530,29 +1451,27 @@ impl<'hir> LoweringContext<'_, 'hir> {
                         &ImplTraitContext::Disallowed(ImplTraitPosition::Bound),
                     )
                 })),
-                span: self.lower_span(span),
+                span: self.lower_span(*span),
                 origin: PredicateOrigin::WhereClause,
             }),
-            WherePredicate::RegionPredicate(WhereRegionPredicate {
-                ref lifetime,
-                ref bounds,
-                span,
-            }) => hir::WherePredicate::RegionPredicate(hir::WhereRegionPredicate {
-                span: self.lower_span(span),
-                lifetime: self.lower_lifetime(lifetime),
-                bounds: self.lower_param_bounds(
-                    bounds,
-                    &ImplTraitContext::Disallowed(ImplTraitPosition::Bound),
-                ),
-                in_where_clause: true,
-            }),
-            WherePredicate::EqPredicate(WhereEqPredicate { ref lhs_ty, ref rhs_ty, span }) => {
+            WherePredicate::RegionPredicate(WhereRegionPredicate { lifetime, bounds, span }) => {
+                hir::WherePredicate::RegionPredicate(hir::WhereRegionPredicate {
+                    span: self.lower_span(*span),
+                    lifetime: self.lower_lifetime(lifetime),
+                    bounds: self.lower_param_bounds(
+                        bounds,
+                        &ImplTraitContext::Disallowed(ImplTraitPosition::Bound),
+                    ),
+                    in_where_clause: true,
+                })
+            }
+            WherePredicate::EqPredicate(WhereEqPredicate { lhs_ty, rhs_ty, span }) => {
                 hir::WherePredicate::EqPredicate(hir::WhereEqPredicate {
                     lhs_ty: self
                         .lower_ty(lhs_ty, &ImplTraitContext::Disallowed(ImplTraitPosition::Type)),
                     rhs_ty: self
                         .lower_ty(rhs_ty, &ImplTraitContext::Disallowed(ImplTraitPosition::Type)),
-                    span: self.lower_span(span),
+                    span: self.lower_span(*span),
                 })
             }
         }
diff --git a/compiler/rustc_ast_lowering/src/lib.rs b/compiler/rustc_ast_lowering/src/lib.rs
index ff29d15f1..4fa18907f 100644
--- a/compiler/rustc_ast_lowering/src/lib.rs
+++ b/compiler/rustc_ast_lowering/src/lib.rs
@@ -34,7 +34,6 @@
 #![feature(let_chains)]
 #![feature(never_type)]
 #![recursion_limit = "256"]
-#![allow(rustc::potential_query_instability)]
 #![deny(rustc::untranslatable_diagnostic)]
 #![deny(rustc::diagnostic_outside_of_impl)]
 
@@ -61,8 +60,8 @@ use rustc_hir::def_id::{LocalDefId, CRATE_DEF_ID};
 use rustc_hir::definitions::DefPathData;
 use rustc_hir::{ConstArg, GenericArg, ItemLocalId, ParamName, TraitCandidate};
 use rustc_index::vec::{Idx, IndexVec};
+use rustc_middle::span_bug;
 use rustc_middle::ty::{ResolverAstLowering, TyCtxt};
-use rustc_middle::{bug, span_bug};
 use rustc_session::parse::feature_err;
 use rustc_span::hygiene::MacroKind;
 use rustc_span::source_map::DesugaringKind;
@@ -107,7 +106,7 @@ struct LoweringContext<'a, 'hir> {
     /// Attributes inside the owner being lowered.
     attrs: SortedMap<hir::ItemLocalId, &'hir [Attribute]>,
     /// Collect items that were created by lowering the current owner.
-    children: FxHashMap<LocalDefId, hir::MaybeOwner<&'hir hir::OwnerInfo<'hir>>>,
+    children: Vec<(LocalDefId, hir::MaybeOwner<&'hir hir::OwnerInfo<'hir>>)>,
 
     generator_kind: Option<hir::GeneratorKind>,
 
@@ -260,6 +259,8 @@ enum ImplTraitContext {
     },
     /// Impl trait in type aliases.
     TypeAliasesOpaqueTy,
+    /// `impl Trait` is unstably accepted in this position.
+    FeatureGated(ImplTraitPosition, Symbol),
     /// `impl Trait` is not accepted in this position.
     Disallowed(ImplTraitPosition),
 }
@@ -328,7 +329,14 @@ enum FnDeclKind {
 }
 
 impl FnDeclKind {
-    fn impl_trait_allowed(&self, tcx: TyCtxt<'_>) -> bool {
+    fn param_impl_trait_allowed(&self) -> bool {
+        match self {
+            FnDeclKind::Fn | FnDeclKind::Inherent | FnDeclKind::Impl | FnDeclKind::Trait => true,
+            _ => false,
+        }
+    }
+
+    fn return_impl_trait_allowed(&self, tcx: TyCtxt<'_>) -> bool {
         match self {
             FnDeclKind::Fn | FnDeclKind::Inherent => true,
             FnDeclKind::Impl if tcx.features().return_position_impl_trait_in_trait => true,
@@ -481,6 +489,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         parent: LocalDefId,
         node_id: ast::NodeId,
         data: DefPathData,
+        span: Span,
     ) -> LocalDefId {
         debug_assert_ne!(node_id, ast::DUMMY_NODE_ID);
         assert!(
@@ -491,7 +500,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             self.tcx.hir().def_key(self.local_def_id(node_id)),
         );
 
-        let def_id = self.tcx.create_def(parent, data);
+        let def_id = self.tcx.at(span).create_def(parent, data).def_id();
 
         debug!("create_def: def_id_to_node_id[{:?}] <-> {:?}", def_id, node_id);
         self.resolver.node_id_to_def_id.insert(node_id, def_id);
@@ -611,8 +620,8 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         self.impl_trait_defs = current_impl_trait_defs;
         self.impl_trait_bounds = current_impl_trait_bounds;
 
-        let _old = self.children.insert(def_id, hir::MaybeOwner::Owner(info));
-        debug_assert!(_old.is_none())
+        debug_assert!(self.children.iter().find(|(id, _)| id == &def_id).is_none());
+        self.children.push((def_id, hir::MaybeOwner::Owner(info)));
     }
 
     /// Installs the remapping `remap` in scope while `f` is being executed.
@@ -719,8 +728,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
 
                 assert_ne!(local_id, hir::ItemLocalId::new(0));
                 if let Some(def_id) = self.opt_local_def_id(ast_node_id) {
-                    // Do not override a `MaybeOwner::Owner` that may already here.
-                    self.children.entry(def_id).or_insert(hir::MaybeOwner::NonOwner(hir_id));
+                    self.children.push((def_id, hir::MaybeOwner::NonOwner(hir_id)));
                     self.local_id_to_def_id.insert(local_id, def_id);
                 }
 
@@ -818,6 +826,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                     self.current_hir_id_owner.def_id,
                     param,
                     DefPathData::LifetimeNs(kw::UnderscoreLifetime),
+                    ident.span,
                 );
                 debug!(?_def_id);
 
@@ -830,8 +839,10 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             ),
         };
         let hir_id = self.lower_node_id(node_id);
+        let def_id = self.local_def_id(node_id);
         Some(hir::GenericParam {
             hir_id,
+            def_id,
             name,
             span: self.lower_span(ident.span),
             pure_wrt_drop: false,
@@ -911,7 +922,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             AttrKind::Normal(ref normal) => AttrKind::Normal(P(NormalAttr {
                 item: AttrItem {
                     path: normal.item.path.clone(),
-                    args: self.lower_mac_args(&normal.item.args),
+                    args: self.lower_attr_args(&normal.item.args),
                     tokens: None,
                 },
                 tokens: None,
@@ -931,51 +942,39 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         }
     }
 
-    fn lower_mac_args(&self, args: &MacArgs) -> MacArgs {
-        match *args {
-            MacArgs::Empty => MacArgs::Empty,
-            MacArgs::Delimited(dspan, delim, ref tokens) => {
-                // This is either a non-key-value attribute, or a `macro_rules!` body.
-                // We either not have any nonterminals present (in the case of an attribute),
-                // or have tokens available for all nonterminals in the case of a nested
-                // `macro_rules`: e.g:
-                //
-                // ```rust
-                // macro_rules! outer {
-                //     ($e:expr) => {
-                //         macro_rules! inner {
-                //             () => { $e }
-                //         }
-                //     }
-                // }
-                // ```
-                //
-                // In both cases, we don't want to synthesize any tokens
-                MacArgs::Delimited(dspan, delim, tokens.flattened())
-            }
+    fn lower_attr_args(&self, args: &AttrArgs) -> AttrArgs {
+        match args {
+            AttrArgs::Empty => AttrArgs::Empty,
+            AttrArgs::Delimited(args) => AttrArgs::Delimited(self.lower_delim_args(args)),
             // This is an inert key-value attribute - it will never be visible to macros
             // after it gets lowered to HIR. Therefore, we can extract literals to handle
             // nonterminals in `#[doc]` (e.g. `#[doc = $e]`).
-            MacArgs::Eq(eq_span, MacArgsEq::Ast(ref expr)) => {
+            AttrArgs::Eq(eq_span, AttrArgsEq::Ast(expr)) => {
                 // In valid code the value always ends up as a single literal. Otherwise, a dummy
                 // literal suffices because the error is handled elsewhere.
-                let lit = if let ExprKind::Lit(lit) = &expr.kind {
-                    lit.clone()
+                let lit = if let ExprKind::Lit(token_lit) = expr.kind
+                    && let Ok(lit) = MetaItemLit::from_token_lit(token_lit, expr.span)
+                {
+                    lit
                 } else {
-                    Lit {
+                    MetaItemLit {
                         token_lit: token::Lit::new(token::LitKind::Err, kw::Empty, None),
                         kind: LitKind::Err,
                         span: DUMMY_SP,
                     }
                 };
-                MacArgs::Eq(eq_span, MacArgsEq::Hir(lit))
+                AttrArgs::Eq(*eq_span, AttrArgsEq::Hir(lit))
             }
-            MacArgs::Eq(_, MacArgsEq::Hir(ref lit)) => {
+            AttrArgs::Eq(_, AttrArgsEq::Hir(lit)) => {
                 unreachable!("in literal form when lowering mac args eq: {:?}", lit)
             }
         }
     }
 
+    fn lower_delim_args(&self, args: &DelimArgs) -> DelimArgs {
+        DelimArgs { dspan: args.dspan, delim: args.delim, tokens: args.tokens.flattened() }
+    }
+
     /// Given an associated type constraint like one of these:
     ///
     /// ```ignore (illustrative)
@@ -994,12 +993,12 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     ) -> hir::TypeBinding<'hir> {
         debug!("lower_assoc_ty_constraint(constraint={:?}, itctx={:?})", constraint, itctx);
         // lower generic arguments of identifier in constraint
-        let gen_args = if let Some(ref gen_args) = constraint.gen_args {
+        let gen_args = if let Some(gen_args) = &constraint.gen_args {
             let gen_args_ctor = match gen_args {
-                GenericArgs::AngleBracketed(ref data) => {
+                GenericArgs::AngleBracketed(data) => {
                     self.lower_angle_bracketed_parameter_data(data, ParamMode::Explicit, itctx).0
                 }
-                GenericArgs::Parenthesized(ref data) => {
+                GenericArgs::Parenthesized(data) => {
                     self.emit_bad_parenthesized_trait_in_assoc_ty(data);
                     let aba = self.ast_arena.aba.alloc(data.as_angle_bracketed_args());
                     self.lower_angle_bracketed_parameter_data(aba, ParamMode::Explicit, itctx).0
@@ -1011,15 +1010,15 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         };
         let itctx_tait = &ImplTraitContext::TypeAliasesOpaqueTy;
 
-        let kind = match constraint.kind {
-            AssocConstraintKind::Equality { ref term } => {
+        let kind = match &constraint.kind {
+            AssocConstraintKind::Equality { term } => {
                 let term = match term {
-                    Term::Ty(ref ty) => self.lower_ty(ty, itctx).into(),
-                    Term::Const(ref c) => self.lower_anon_const(c).into(),
+                    Term::Ty(ty) => self.lower_ty(ty, itctx).into(),
+                    Term::Const(c) => self.lower_anon_const(c).into(),
                 };
                 hir::TypeBindingKind::Equality { term }
             }
-            AssocConstraintKind::Bound { ref bounds } => {
+            AssocConstraintKind::Bound { bounds } => {
                 // Piggy-back on the `impl Trait` context to figure out the correct behavior.
                 let (desugar_to_impl_trait, itctx) = match itctx {
                     // We are in the return position:
@@ -1129,7 +1128,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         match arg {
             ast::GenericArg::Lifetime(lt) => GenericArg::Lifetime(self.lower_lifetime(&lt)),
             ast::GenericArg::Type(ty) => {
-                match ty.kind {
+                match &ty.kind {
                     TyKind::Infer if self.tcx.features().generic_arg_infer => {
                         return GenericArg::Infer(hir::InferArg {
                             hir_id: self.lower_node_id(ty.id),
@@ -1140,7 +1139,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                     // parsing. We try to resolve that ambiguity by attempting resolution in both the
                     // type and value namespaces. If we resolved the path in the value namespace, we
                     // transform it into a generic const argument.
-                    TyKind::Path(ref qself, ref path) => {
+                    TyKind::Path(qself, path) => {
                         if let Some(res) = self
                             .resolver
                             .get_partial_res(ty.id)
@@ -1156,15 +1155,16 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
 
                                 let parent_def_id = self.current_hir_id_owner;
                                 let node_id = self.next_node_id();
+                                let span = self.lower_span(ty.span);
 
                                 // Add a definition for the in-band const def.
-                                self.create_def(
+                                let def_id = self.create_def(
                                     parent_def_id.def_id,
                                     node_id,
                                     DefPathData::AnonConst,
+                                    span,
                                 );
 
-                                let span = self.lower_span(ty.span);
                                 let path_expr = Expr {
                                     id: ty.id,
                                     kind: ExprKind::Path(qself.clone(), path.clone()),
@@ -1174,6 +1174,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                                 };
 
                                 let ct = self.with_new_scopes(|this| hir::AnonConst {
+                                    def_id,
                                     hir_id: this.lower_node_id(node_id),
                                     body: this.lower_const_body(path_expr.span, Some(&path_expr)),
                                 });
@@ -1200,7 +1201,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     fn lower_path_ty(
         &mut self,
         t: &Ty,
-        qself: &Option<QSelf>,
+        qself: &Option<ptr::P<QSelf>>,
         path: &Path,
         param_mode: ParamMode,
         itctx: &ImplTraitContext,
@@ -1246,12 +1247,12 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     }
 
     fn lower_ty_direct(&mut self, t: &Ty, itctx: &ImplTraitContext) -> hir::Ty<'hir> {
-        let kind = match t.kind {
+        let kind = match &t.kind {
             TyKind::Infer => hir::TyKind::Infer,
             TyKind::Err => hir::TyKind::Err,
-            TyKind::Slice(ref ty) => hir::TyKind::Slice(self.lower_ty(ty, itctx)),
-            TyKind::Ptr(ref mt) => hir::TyKind::Ptr(self.lower_mt(mt, itctx)),
-            TyKind::Rptr(ref region, ref mt) => {
+            TyKind::Slice(ty) => hir::TyKind::Slice(self.lower_ty(ty, itctx)),
+            TyKind::Ptr(mt) => hir::TyKind::Ptr(self.lower_mt(mt, itctx)),
+            TyKind::Rptr(region, mt) => {
                 let region = region.unwrap_or_else(|| {
                     let id = if let Some(LifetimeRes::ElidedAnchor { start, end }) =
                         self.resolver.get_lifetime_res(t.id)
@@ -1261,30 +1262,30 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                     } else {
                         self.next_node_id()
                     };
-                    let span = self.tcx.sess.source_map().start_point(t.span);
+                    let span = self.tcx.sess.source_map().start_point(t.span).shrink_to_hi();
                     Lifetime { ident: Ident::new(kw::UnderscoreLifetime, span), id }
                 });
                 let lifetime = self.lower_lifetime(&region);
                 hir::TyKind::Rptr(lifetime, self.lower_mt(mt, itctx))
             }
-            TyKind::BareFn(ref f) => {
+            TyKind::BareFn(f) => {
                 let generic_params = self.lower_lifetime_binder(t.id, &f.generic_params);
                 hir::TyKind::BareFn(self.arena.alloc(hir::BareFnTy {
                     generic_params,
                     unsafety: self.lower_unsafety(f.unsafety),
                     abi: self.lower_extern(f.ext),
-                    decl: self.lower_fn_decl(&f.decl, None, t.span, FnDeclKind::Pointer, None),
+                    decl: self.lower_fn_decl(&f.decl, t.id, t.span, FnDeclKind::Pointer, None),
                     param_names: self.lower_fn_params_to_names(&f.decl),
                 }))
             }
             TyKind::Never => hir::TyKind::Never,
-            TyKind::Tup(ref tys) => hir::TyKind::Tup(
+            TyKind::Tup(tys) => hir::TyKind::Tup(
                 self.arena.alloc_from_iter(tys.iter().map(|ty| self.lower_ty_direct(ty, itctx))),
             ),
-            TyKind::Paren(ref ty) => {
+            TyKind::Paren(ty) => {
                 return self.lower_ty_direct(ty, itctx);
             }
-            TyKind::Path(ref qself, ref path) => {
+            TyKind::Path(qself, path) => {
                 return self.lower_path_ty(t, qself, path, ParamMode::Explicit, itctx);
             }
             TyKind::ImplicitSelf => {
@@ -1304,48 +1305,46 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                     }),
                 ))
             }
-            TyKind::Array(ref ty, ref length) => {
+            TyKind::Array(ty, length) => {
                 hir::TyKind::Array(self.lower_ty(ty, itctx), self.lower_array_length(length))
             }
-            TyKind::Typeof(ref expr) => hir::TyKind::Typeof(self.lower_anon_const(expr)),
-            TyKind::TraitObject(ref bounds, kind) => {
+            TyKind::Typeof(expr) => hir::TyKind::Typeof(self.lower_anon_const(expr)),
+            TyKind::TraitObject(bounds, kind) => {
                 let mut lifetime_bound = None;
                 let (bounds, lifetime_bound) = self.with_dyn_type_scope(true, |this| {
                     let bounds =
-                        this.arena.alloc_from_iter(bounds.iter().filter_map(
-                            |bound| match *bound {
-                                GenericBound::Trait(
-                                    ref ty,
-                                    TraitBoundModifier::None | TraitBoundModifier::MaybeConst,
-                                ) => Some(this.lower_poly_trait_ref(ty, itctx)),
-                                // `~const ?Bound` will cause an error during AST validation
-                                // anyways, so treat it like `?Bound` as compilation proceeds.
-                                GenericBound::Trait(
-                                    _,
-                                    TraitBoundModifier::Maybe | TraitBoundModifier::MaybeConstMaybe,
-                                ) => None,
-                                GenericBound::Outlives(ref lifetime) => {
-                                    if lifetime_bound.is_none() {
-                                        lifetime_bound = Some(this.lower_lifetime(lifetime));
-                                    }
-                                    None
+                        this.arena.alloc_from_iter(bounds.iter().filter_map(|bound| match bound {
+                            GenericBound::Trait(
+                                ty,
+                                TraitBoundModifier::None | TraitBoundModifier::MaybeConst,
+                            ) => Some(this.lower_poly_trait_ref(ty, itctx)),
+                            // `~const ?Bound` will cause an error during AST validation
+                            // anyways, so treat it like `?Bound` as compilation proceeds.
+                            GenericBound::Trait(
+                                _,
+                                TraitBoundModifier::Maybe | TraitBoundModifier::MaybeConstMaybe,
+                            ) => None,
+                            GenericBound::Outlives(lifetime) => {
+                                if lifetime_bound.is_none() {
+                                    lifetime_bound = Some(this.lower_lifetime(lifetime));
                                 }
-                            },
-                        ));
+                                None
+                            }
+                        }));
                     let lifetime_bound =
                         lifetime_bound.unwrap_or_else(|| this.elided_dyn_bound(t.span));
                     (bounds, lifetime_bound)
                 });
-                hir::TyKind::TraitObject(bounds, lifetime_bound, kind)
+                hir::TyKind::TraitObject(bounds, lifetime_bound, *kind)
             }
-            TyKind::ImplTrait(def_node_id, ref bounds) => {
+            TyKind::ImplTrait(def_node_id, bounds) => {
                 let span = t.span;
                 match itctx {
                     ImplTraitContext::ReturnPositionOpaqueTy { origin, in_trait } => self
                         .lower_opaque_impl_trait(
                             span,
                             *origin,
-                            def_node_id,
+                            *def_node_id,
                             bounds,
                             *in_trait,
                             itctx,
@@ -1353,38 +1352,37 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                     ImplTraitContext::TypeAliasesOpaqueTy => self.lower_opaque_impl_trait(
                         span,
                         hir::OpaqueTyOrigin::TyAlias,
-                        def_node_id,
+                        *def_node_id,
                         bounds,
                         false,
                         itctx,
                     ),
                     ImplTraitContext::Universal => {
+                        let span = t.span;
                         self.create_def(
                             self.current_hir_id_owner.def_id,
-                            def_node_id,
+                            *def_node_id,
                             DefPathData::ImplTrait,
+                            span,
                         );
-                        let span = t.span;
                         let ident = Ident::from_str_and_span(&pprust::ty_to_string(t), span);
                         let (param, bounds, path) =
-                            self.lower_generic_and_bounds(def_node_id, span, ident, bounds);
+                            self.lower_generic_and_bounds(*def_node_id, span, ident, bounds);
                         self.impl_trait_defs.push(param);
                         if let Some(bounds) = bounds {
                             self.impl_trait_bounds.push(bounds);
                         }
                         path
                     }
-                    ImplTraitContext::Disallowed(
-                        position @ (ImplTraitPosition::TraitReturn | ImplTraitPosition::ImplReturn),
-                    ) => {
+                    ImplTraitContext::FeatureGated(position, feature) => {
                         self.tcx
                             .sess
                             .create_feature_err(
                                 MisplacedImplTrait {
                                     span: t.span,
-                                    position: DiagnosticArgFromDisplay(&position),
+                                    position: DiagnosticArgFromDisplay(position),
                                 },
-                                sym::return_position_impl_trait_in_trait,
+                                *feature,
                             )
                             .emit();
                         hir::TyKind::Err
@@ -1392,7 +1390,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                     ImplTraitContext::Disallowed(position) => {
                         self.tcx.sess.emit_err(MisplacedImplTrait {
                             span: t.span,
-                            position: DiagnosticArgFromDisplay(&position),
+                            position: DiagnosticArgFromDisplay(position),
                         });
                         hir::TyKind::Err
                     }
@@ -1457,17 +1455,12 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         // frequently opened issues show.
         let opaque_ty_span = self.mark_span_with_reason(DesugaringKind::OpaqueTy, span, None);
 
-        let opaque_ty_def_id = match origin {
-            hir::OpaqueTyOrigin::TyAlias => self.create_def(
-                self.current_hir_id_owner.def_id,
-                opaque_ty_node_id,
-                DefPathData::ImplTrait,
-            ),
-            hir::OpaqueTyOrigin::FnReturn(fn_def_id) => {
-                self.create_def(fn_def_id, opaque_ty_node_id, DefPathData::ImplTrait)
-            }
-            hir::OpaqueTyOrigin::AsyncFn(..) => bug!("unreachable"),
-        };
+        let opaque_ty_def_id = self.create_def(
+            self.current_hir_id_owner.def_id,
+            opaque_ty_node_id,
+            DefPathData::ImplTrait,
+            opaque_ty_span,
+        );
         debug!(?opaque_ty_def_id);
 
         // Contains the new lifetime definitions created for the TAIT (if any).
@@ -1521,6 +1514,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
 
                         hir::GenericParam {
                             hir_id,
+                            def_id: lctx.local_def_id(new_node_id),
                             name,
                             span: lifetime.ident.span,
                             pure_wrt_drop: false,
@@ -1559,15 +1553,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         let lifetimes =
             self.arena.alloc_from_iter(collected_lifetimes.into_iter().map(|(_, lifetime)| {
                 let id = self.next_node_id();
-                let span = lifetime.ident.span;
-
-                let ident = if lifetime.ident.name == kw::UnderscoreLifetime {
-                    Ident::with_dummy_span(kw::UnderscoreLifetime)
-                } else {
-                    lifetime.ident
-                };
-
-                let l = self.new_named_lifetime(lifetime.id, id, span, ident);
+                let l = self.new_named_lifetime(lifetime.id, id, lifetime.ident);
                 hir::GenericArg::Lifetime(l)
             }));
         debug!(?lifetimes);
@@ -1627,6 +1613,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                             parent_def_id,
                             node_id,
                             DefPathData::LifetimeNs(lifetime.ident.name),
+                            lifetime.ident.span,
                         );
                         remapping.insert(old_def_id, new_def_id);
 
@@ -1643,6 +1630,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                             parent_def_id,
                             node_id,
                             DefPathData::LifetimeNs(kw::UnderscoreLifetime),
+                            lifetime.ident.span,
                         );
                         remapping.insert(old_def_id, new_def_id);
 
@@ -1692,7 +1680,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     fn lower_fn_decl(
         &mut self,
         decl: &FnDecl,
-        fn_node_id: Option<NodeId>,
+        fn_node_id: NodeId,
         fn_span: Span,
         kind: FnDeclKind,
         make_ret_async: Option<(NodeId, Span)>,
@@ -1707,23 +1695,21 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             inputs = &inputs[..inputs.len() - 1];
         }
         let inputs = self.arena.alloc_from_iter(inputs.iter().map(|param| {
-            if fn_node_id.is_some() {
-                self.lower_ty_direct(&param.ty, &ImplTraitContext::Universal)
+            let itctx = if kind.param_impl_trait_allowed() {
+                ImplTraitContext::Universal
             } else {
-                self.lower_ty_direct(
-                    &param.ty,
-                    &ImplTraitContext::Disallowed(match kind {
-                        FnDeclKind::Fn | FnDeclKind::Inherent => {
-                            unreachable!("fn should allow in-band lifetimes")
-                        }
-                        FnDeclKind::ExternFn => ImplTraitPosition::ExternFnParam,
-                        FnDeclKind::Closure => ImplTraitPosition::ClosureParam,
-                        FnDeclKind::Pointer => ImplTraitPosition::PointerParam,
-                        FnDeclKind::Trait => ImplTraitPosition::TraitParam,
-                        FnDeclKind::Impl => ImplTraitPosition::ImplParam,
-                    }),
-                )
-            }
+                ImplTraitContext::Disallowed(match kind {
+                    FnDeclKind::Fn | FnDeclKind::Inherent => {
+                        unreachable!("fn should allow APIT")
+                    }
+                    FnDeclKind::ExternFn => ImplTraitPosition::ExternFnParam,
+                    FnDeclKind::Closure => ImplTraitPosition::ClosureParam,
+                    FnDeclKind::Pointer => ImplTraitPosition::PointerParam,
+                    FnDeclKind::Trait => ImplTraitPosition::TraitParam,
+                    FnDeclKind::Impl => ImplTraitPosition::ImplParam,
+                })
+            };
+            self.lower_ty_direct(&param.ty, &itctx)
         }));
 
         let output = if let Some((ret_id, span)) = make_ret_async {
@@ -1746,22 +1732,21 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
 
             self.lower_async_fn_ret_ty(
                 &decl.output,
-                fn_node_id.expect("`make_ret_async` but no `fn_def_id`"),
+                fn_node_id,
                 ret_id,
                 matches!(kind, FnDeclKind::Trait),
             )
         } else {
-            match decl.output {
-                FnRetTy::Ty(ref ty) => {
-                    let mut context = match fn_node_id {
-                        Some(fn_node_id) if kind.impl_trait_allowed(self.tcx) => {
-                            let fn_def_id = self.local_def_id(fn_node_id);
-                            ImplTraitContext::ReturnPositionOpaqueTy {
-                                origin: hir::OpaqueTyOrigin::FnReturn(fn_def_id),
-                                in_trait: matches!(kind, FnDeclKind::Trait),
-                            }
+            match &decl.output {
+                FnRetTy::Ty(ty) => {
+                    let context = if kind.return_impl_trait_allowed(self.tcx) {
+                        let fn_def_id = self.local_def_id(fn_node_id);
+                        ImplTraitContext::ReturnPositionOpaqueTy {
+                            origin: hir::OpaqueTyOrigin::FnReturn(fn_def_id),
+                            in_trait: matches!(kind, FnDeclKind::Trait),
                         }
-                        _ => ImplTraitContext::Disallowed(match kind {
+                    } else {
+                        let position = match kind {
                             FnDeclKind::Fn | FnDeclKind::Inherent => {
                                 unreachable!("fn should allow in-band lifetimes")
                             }
@@ -1770,11 +1755,18 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                             FnDeclKind::Pointer => ImplTraitPosition::PointerReturn,
                             FnDeclKind::Trait => ImplTraitPosition::TraitReturn,
                             FnDeclKind::Impl => ImplTraitPosition::ImplReturn,
-                        }),
+                        };
+                        match kind {
+                            FnDeclKind::Trait | FnDeclKind::Impl => ImplTraitContext::FeatureGated(
+                                position,
+                                sym::return_position_impl_trait_in_trait,
+                            ),
+                            _ => ImplTraitContext::Disallowed(position),
+                        }
                     };
-                    hir::FnRetTy::Return(self.lower_ty(ty, &mut context))
+                    hir::FnRetTy::Return(self.lower_ty(ty, &context))
                 }
-                FnRetTy::Default(span) => hir::FnRetTy::DefaultReturn(self.lower_span(span)),
+                FnRetTy::Default(span) => hir::FnRetTy::DefaultReturn(self.lower_span(*span)),
             }
         };
 
@@ -1782,26 +1774,23 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             inputs,
             output,
             c_variadic,
+            lifetime_elision_allowed: self.resolver.lifetime_elision_allowed.contains(&fn_node_id),
             implicit_self: decl.inputs.get(0).map_or(hir::ImplicitSelfKind::None, |arg| {
                 let is_mutable_pat = matches!(
                     arg.pat.kind,
                     PatKind::Ident(hir::BindingAnnotation(_, Mutability::Mut), ..)
                 );
 
-                match arg.ty.kind {
+                match &arg.ty.kind {
                     TyKind::ImplicitSelf if is_mutable_pat => hir::ImplicitSelfKind::Mut,
                     TyKind::ImplicitSelf => hir::ImplicitSelfKind::Imm,
                     // Given we are only considering `ImplicitSelf` types, we needn't consider
                     // the case where we have a mutable pattern to a reference as that would
                     // no longer be an `ImplicitSelf`.
-                    TyKind::Rptr(_, ref mt)
-                        if mt.ty.kind.is_implicit_self() && mt.mutbl == ast::Mutability::Mut =>
-                    {
-                        hir::ImplicitSelfKind::MutRef
-                    }
-                    TyKind::Rptr(_, ref mt) if mt.ty.kind.is_implicit_self() => {
-                        hir::ImplicitSelfKind::ImmRef
-                    }
+                    TyKind::Rptr(_, mt) if mt.ty.kind.is_implicit_self() => match mt.mutbl {
+                        hir::Mutability::Not => hir::ImplicitSelfKind::ImmRef,
+                        hir::Mutability::Mut => hir::ImplicitSelfKind::MutRef,
+                    },
                     _ => hir::ImplicitSelfKind::None,
                 }
             }),
@@ -1828,9 +1817,11 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
 
         let opaque_ty_span = self.mark_span_with_reason(DesugaringKind::Async, span, None);
 
-        let opaque_ty_def_id = self.local_def_id(opaque_ty_node_id);
         let fn_def_id = self.local_def_id(fn_node_id);
 
+        let opaque_ty_def_id =
+            self.create_def(fn_def_id, opaque_ty_node_id, DefPathData::ImplTrait, opaque_ty_span);
+
         // When we create the opaque type for this async fn, it is going to have
         // to capture all the lifetimes involved in the signature (including in the
         // return type). This is done by introducing lifetime parameters for:
@@ -1889,6 +1880,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                 opaque_ty_def_id,
                 inner_node_id,
                 DefPathData::LifetimeNs(ident.name),
+                ident.span,
             );
             new_remapping.insert(outer_def_id, inner_def_id);
 
@@ -1953,7 +1945,10 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                     output,
                     span,
                     if in_trait && !this.tcx.features().return_position_impl_trait_in_trait {
-                        ImplTraitContext::Disallowed(ImplTraitPosition::TraitReturn)
+                        ImplTraitContext::FeatureGated(
+                            ImplTraitPosition::TraitReturn,
+                            sym::return_position_impl_trait_in_trait,
+                        )
                     } else {
                         ImplTraitContext::ReturnPositionOpaqueTy {
                             origin: hir::OpaqueTyOrigin::FnReturn(fn_def_id),
@@ -1978,6 +1973,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
 
                         hir::GenericParam {
                             hir_id,
+                            def_id: this.local_def_id(new_node_id),
                             name,
                             span: lifetime.ident.span,
                             pure_wrt_drop: false,
@@ -2024,18 +2020,10 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         let generic_args = self.arena.alloc_from_iter(collected_lifetimes.into_iter().map(
             |(_, lifetime, res)| {
                 let id = self.next_node_id();
-                let span = lifetime.ident.span;
-
-                let ident = if lifetime.ident.name == kw::UnderscoreLifetime {
-                    Ident::with_dummy_span(kw::UnderscoreLifetime)
-                } else {
-                    lifetime.ident
-                };
-
                 let res = res.unwrap_or(
                     self.resolver.get_lifetime_res(lifetime.id).unwrap_or(LifetimeRes::Error),
                 );
-                hir::GenericArg::Lifetime(self.new_named_lifetime_with_res(id, span, ident, res))
+                hir::GenericArg::Lifetime(self.new_named_lifetime_with_res(id, lifetime.ident, res))
             },
         ));
 
@@ -2105,43 +2093,40 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     }
 
     fn lower_lifetime(&mut self, l: &Lifetime) -> &'hir hir::Lifetime {
-        let span = self.lower_span(l.ident.span);
         let ident = self.lower_ident(l.ident);
-        self.new_named_lifetime(l.id, l.id, span, ident)
+        self.new_named_lifetime(l.id, l.id, ident)
     }
 
     #[instrument(level = "debug", skip(self))]
     fn new_named_lifetime_with_res(
         &mut self,
         id: NodeId,
-        span: Span,
         ident: Ident,
         res: LifetimeRes,
     ) -> &'hir hir::Lifetime {
-        let name = match res {
+        let res = match res {
             LifetimeRes::Param { param, .. } => {
-                let p_name = ParamName::Plain(ident);
                 let param = self.get_remapped_def_id(param);
-
-                hir::LifetimeName::Param(param, p_name)
+                hir::LifetimeName::Param(param)
             }
             LifetimeRes::Fresh { param, .. } => {
-                debug_assert_eq!(ident.name, kw::UnderscoreLifetime);
                 let param = self.local_def_id(param);
-
-                hir::LifetimeName::Param(param, ParamName::Fresh)
+                hir::LifetimeName::Param(param)
             }
             LifetimeRes::Infer => hir::LifetimeName::Infer,
             LifetimeRes::Static => hir::LifetimeName::Static,
             LifetimeRes::Error => hir::LifetimeName::Error,
-            res => panic!("Unexpected lifetime resolution {:?} for {:?} at {:?}", res, ident, span),
+            res => panic!(
+                "Unexpected lifetime resolution {:?} for {:?} at {:?}",
+                res, ident, ident.span
+            ),
         };
 
-        debug!(?name);
+        debug!(?res);
         self.arena.alloc(hir::Lifetime {
             hir_id: self.lower_node_id(id),
-            span: self.lower_span(span),
-            name,
+            ident: self.lower_ident(ident),
+            res,
         })
     }
 
@@ -2150,11 +2135,10 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         &mut self,
         id: NodeId,
         new_id: NodeId,
-        span: Span,
         ident: Ident,
     ) -> &'hir hir::Lifetime {
         let res = self.resolver.get_lifetime_res(id).unwrap_or(LifetimeRes::Error);
-        self.new_named_lifetime_with_res(new_id, span, ident, res)
+        self.new_named_lifetime_with_res(new_id, ident, res)
     }
 
     fn lower_generic_params_mut<'s>(
@@ -2176,6 +2160,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         self.lower_attrs(hir_id, &param.attrs);
         hir::GenericParam {
             hir_id,
+            def_id: self.local_def_id(param.id),
             name,
             span: self.lower_span(param.span()),
             pure_wrt_drop: self.tcx.sess.contains_name(&param.attrs, sym::may_dangle),
@@ -2188,7 +2173,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         &mut self,
         param: &GenericParam,
     ) -> (hir::ParamName, hir::GenericParamKind<'hir>) {
-        match param.kind {
+        match &param.kind {
             GenericParamKind::Lifetime => {
                 // AST resolution emitted an error on those parameters, so we lower them using
                 // `ParamName::Error`.
@@ -2204,7 +2189,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
 
                 (param_name, kind)
             }
-            GenericParamKind::Type { ref default, .. } => {
+            GenericParamKind::Type { default, .. } => {
                 let kind = hir::GenericParamKind::Type {
                     default: default.as_ref().map(|x| {
                         self.lower_ty(x, &ImplTraitContext::Disallowed(ImplTraitPosition::Type))
@@ -2214,7 +2199,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
 
                 (hir::ParamName::Plain(self.lower_ident(param.ident)), kind)
             }
-            GenericParamKind::Const { ref ty, kw_span: _, ref default } => {
+            GenericParamKind::Const { ty, kw_span: _, default } => {
                 let ty = self.lower_ty(&ty, &ImplTraitContext::Disallowed(ImplTraitPosition::Type));
                 let default = default.as_ref().map(|def| self.lower_anon_const(def));
                 (
@@ -2280,6 +2265,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         // Set the name to `impl Bound1 + Bound2`.
         let param = hir::GenericParam {
             hir_id: self.lower_node_id(node_id),
+            def_id,
             name: ParamName::Plain(self.lower_ident(ident)),
             pure_wrt_drop: false,
             span: self.lower_span(span),
@@ -2315,7 +2301,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     /// has no attributes and is not targeted by a `break`.
     fn lower_block_expr(&mut self, b: &Block) -> hir::Expr<'hir> {
         let block = self.lower_block(b, false);
-        self.expr_block(block, AttrVec::new())
+        self.expr_block(block)
     }
 
     fn lower_array_length(&mut self, c: &AnonConst) -> hir::ArrayLen {
@@ -2340,6 +2326,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
 
     fn lower_anon_const(&mut self, c: &AnonConst) -> hir::AnonConst {
         self.with_new_scopes(|this| hir::AnonConst {
+            def_id: this.local_def_id(c.id),
             hir_id: this.lower_node_id(c.id),
             body: this.lower_const_body(c.value.span, Some(&c.value)),
         })
@@ -2563,8 +2550,8 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     fn elided_dyn_bound(&mut self, span: Span) -> &'hir hir::Lifetime {
         let r = hir::Lifetime {
             hir_id: self.next_id(),
-            span: self.lower_span(span),
-            name: hir::LifetimeName::ImplicitObjectLifetimeDefault,
+            ident: Ident::new(kw::Empty, self.lower_span(span)),
+            res: hir::LifetimeName::ImplicitObjectLifetimeDefault,
         };
         debug!("elided_dyn_bound: r={:?}", r);
         self.arena.alloc(r)
diff --git a/compiler/rustc_ast_lowering/src/pat.rs b/compiler/rustc_ast_lowering/src/pat.rs
index 1af1633b5..16b012630 100644
--- a/compiler/rustc_ast_lowering/src/pat.rs
+++ b/compiler/rustc_ast_lowering/src/pat.rs
@@ -22,16 +22,16 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         ensure_sufficient_stack(|| {
             // loop here to avoid recursion
             let node = loop {
-                match pattern.kind {
+                match &pattern.kind {
                     PatKind::Wild => break hir::PatKind::Wild,
-                    PatKind::Ident(binding_mode, ident, ref sub) => {
-                        let lower_sub = |this: &mut Self| sub.as_ref().map(|s| this.lower_pat(&*s));
-                        break self.lower_pat_ident(pattern, binding_mode, ident, lower_sub);
+                    PatKind::Ident(binding_mode, ident, sub) => {
+                        let lower_sub = |this: &mut Self| sub.as_ref().map(|s| this.lower_pat(s));
+                        break self.lower_pat_ident(pattern, *binding_mode, *ident, lower_sub);
                     }
-                    PatKind::Lit(ref e) => {
+                    PatKind::Lit(e) => {
                         break hir::PatKind::Lit(self.lower_expr_within_pat(e, false));
                     }
-                    PatKind::TupleStruct(ref qself, ref path, ref pats) => {
+                    PatKind::TupleStruct(qself, path, pats) => {
                         let qpath = self.lower_qpath(
                             pattern.id,
                             qself,
@@ -42,12 +42,12 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                         let (pats, ddpos) = self.lower_pat_tuple(pats, "tuple struct");
                         break hir::PatKind::TupleStruct(qpath, pats, ddpos);
                     }
-                    PatKind::Or(ref pats) => {
+                    PatKind::Or(pats) => {
                         break hir::PatKind::Or(
                             self.arena.alloc_from_iter(pats.iter().map(|x| self.lower_pat_mut(x))),
                         );
                     }
-                    PatKind::Path(ref qself, ref path) => {
+                    PatKind::Path(qself, path) => {
                         let qpath = self.lower_qpath(
                             pattern.id,
                             qself,
@@ -57,7 +57,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                         );
                         break hir::PatKind::Path(qpath);
                     }
-                    PatKind::Struct(ref qself, ref path, ref fields, etc) => {
+                    PatKind::Struct(qself, path, fields, etc) => {
                         let qpath = self.lower_qpath(
                             pattern.id,
                             qself,
@@ -78,32 +78,32 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                                 span: self.lower_span(f.span),
                             }
                         }));
-                        break hir::PatKind::Struct(qpath, fs, etc);
+                        break hir::PatKind::Struct(qpath, fs, *etc);
                     }
-                    PatKind::Tuple(ref pats) => {
+                    PatKind::Tuple(pats) => {
                         let (pats, ddpos) = self.lower_pat_tuple(pats, "tuple");
                         break hir::PatKind::Tuple(pats, ddpos);
                     }
-                    PatKind::Box(ref inner) => {
+                    PatKind::Box(inner) => {
                         break hir::PatKind::Box(self.lower_pat(inner));
                     }
-                    PatKind::Ref(ref inner, mutbl) => {
-                        break hir::PatKind::Ref(self.lower_pat(inner), mutbl);
+                    PatKind::Ref(inner, mutbl) => {
+                        break hir::PatKind::Ref(self.lower_pat(inner), *mutbl);
                     }
-                    PatKind::Range(ref e1, ref e2, Spanned { node: ref end, .. }) => {
+                    PatKind::Range(e1, e2, Spanned { node: end, .. }) => {
                         break hir::PatKind::Range(
                             e1.as_deref().map(|e| self.lower_expr_within_pat(e, true)),
                             e2.as_deref().map(|e| self.lower_expr_within_pat(e, true)),
                             self.lower_range_end(end, e2.is_some()),
                         );
                     }
-                    PatKind::Slice(ref pats) => break self.lower_pat_slice(pats),
+                    PatKind::Slice(pats) => break self.lower_pat_slice(pats),
                     PatKind::Rest => {
                         // If we reach here the `..` pattern is not semantically allowed.
                         break self.ban_illegal_rest_pat(pattern.span);
                     }
                     // return inner to be processed in next loop
-                    PatKind::Paren(ref inner) => pattern = inner,
+                    PatKind::Paren(inner) => pattern = inner,
                     PatKind::MacCall(_) => panic!("{:?} shouldn't exist here", pattern.span),
                 }
             };
@@ -126,7 +126,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             // Note that unlike for slice patterns,
             // where `xs @ ..` is a legal sub-slice pattern,
             // it is not a legal sub-tuple pattern.
-            match pat.kind {
+            match &pat.kind {
                 // Found a sub-tuple rest pattern
                 PatKind::Rest => {
                     rest = Some((idx, pat.span));
@@ -134,12 +134,12 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                 }
                 // Found a sub-tuple pattern `$binding_mode $ident @ ..`.
                 // This is not allowed as a sub-tuple pattern
-                PatKind::Ident(ref _bm, ident, Some(ref sub)) if sub.is_rest() => {
+                PatKind::Ident(_, ident, Some(sub)) if sub.is_rest() => {
                     let sp = pat.span;
                     self.tcx.sess.emit_err(SubTupleBinding {
                         span: sp,
                         ident_name: ident.name,
-                        ident,
+                        ident: *ident,
                         ctx,
                     });
                 }
@@ -176,7 +176,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         let mut prev_rest_span = None;
 
         // Lowers `$bm $ident @ ..` to `$bm $ident @ _`.
-        let lower_rest_sub = |this: &mut Self, pat, ann, ident, sub| {
+        let lower_rest_sub = |this: &mut Self, pat, &ann, &ident, sub| {
             let lower_sub = |this: &mut Self| Some(this.pat_wild_with_node_id_of(sub));
             let node = this.lower_pat_ident(pat, ann, ident, lower_sub);
             this.pat_with_node_id_of(pat, node)
@@ -185,7 +185,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         let mut iter = pats.iter();
         // Lower all the patterns until the first occurrence of a sub-slice pattern.
         for pat in iter.by_ref() {
-            match pat.kind {
+            match &pat.kind {
                 // Found a sub-slice pattern `..`. Record, lower it to `_`, and stop here.
                 PatKind::Rest => {
                     prev_rest_span = Some(pat.span);
@@ -194,7 +194,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                 }
                 // Found a sub-slice pattern `$binding_mode $ident @ ..`.
                 // Record, lower it to `$binding_mode $ident @ _`, and stop here.
-                PatKind::Ident(ann, ident, Some(ref sub)) if sub.is_rest() => {
+                PatKind::Ident(ann, ident, Some(sub)) if sub.is_rest() => {
                     prev_rest_span = Some(sub.span);
                     slice = Some(self.arena.alloc(lower_rest_sub(self, pat, ann, ident, sub)));
                     break;
@@ -207,9 +207,9 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         // Lower all the patterns after the first sub-slice pattern.
         for pat in iter {
             // There was a previous subslice pattern; make sure we don't allow more.
-            let rest_span = match pat.kind {
+            let rest_span = match &pat.kind {
                 PatKind::Rest => Some(pat.span),
-                PatKind::Ident(ann, ident, Some(ref sub)) if sub.is_rest() => {
+                PatKind::Ident(ann, ident, Some(sub)) if sub.is_rest() => {
                     // #69103: Lower into `binding @ _` as above to avoid ICEs.
                     after.push(lower_rest_sub(self, pat, ann, ident, sub));
                     Some(sub.span)
@@ -322,10 +322,13 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     // m!(S);
     // ```
     fn lower_expr_within_pat(&mut self, expr: &Expr, allow_paths: bool) -> &'hir hir::Expr<'hir> {
-        match expr.kind {
-            ExprKind::Lit(..) | ExprKind::ConstBlock(..) | ExprKind::Err => {}
+        match &expr.kind {
+            ExprKind::Lit(..)
+            | ExprKind::ConstBlock(..)
+            | ExprKind::IncludedBytes(..)
+            | ExprKind::Err => {}
             ExprKind::Path(..) if allow_paths => {}
-            ExprKind::Unary(UnOp::Neg, ref inner) if matches!(inner.kind, ExprKind::Lit(_)) => {}
+            ExprKind::Unary(UnOp::Neg, inner) if matches!(inner.kind, ExprKind::Lit(_)) => {}
             _ => {
                 self.tcx.sess.emit_err(ArbitraryExpressionInPattern { span: expr.span });
                 return self.arena.alloc(self.expr_err(expr.span));
diff --git a/compiler/rustc_ast_lowering/src/path.rs b/compiler/rustc_ast_lowering/src/path.rs
index 888776ccc..592fc5aa6 100644
--- a/compiler/rustc_ast_lowering/src/path.rs
+++ b/compiler/rustc_ast_lowering/src/path.rs
@@ -9,17 +9,17 @@ use rustc_ast::{self as ast, *};
 use rustc_hir as hir;
 use rustc_hir::def::{DefKind, PartialRes, Res};
 use rustc_hir::GenericArg;
-use rustc_span::symbol::{kw, Ident};
+use rustc_span::symbol::{kw, sym, Ident};
 use rustc_span::{BytePos, Span, DUMMY_SP};
 
-use smallvec::smallvec;
+use smallvec::{smallvec, SmallVec};
 
 impl<'a, 'hir> LoweringContext<'a, 'hir> {
     #[instrument(level = "trace", skip(self))]
     pub(crate) fn lower_qpath(
         &mut self,
         id: NodeId,
-        qself: &Option<QSelf>,
+        qself: &Option<ptr::P<QSelf>>,
         p: &Path,
         param_mode: ParamMode,
         itctx: &ImplTraitContext,
@@ -144,13 +144,13 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         );
     }
 
-    pub(crate) fn lower_path_extra(
+    pub(crate) fn lower_use_path(
         &mut self,
-        res: Res,
+        res: SmallVec<[Res; 3]>,
         p: &Path,
         param_mode: ParamMode,
-    ) -> &'hir hir::Path<'hir> {
-        self.arena.alloc(hir::Path {
+    ) -> &'hir hir::UsePath<'hir> {
+        self.arena.alloc(hir::UsePath {
             res,
             segments: self.arena.alloc_from_iter(p.segments.iter().map(|segment| {
                 self.lower_path_segment(
@@ -165,17 +165,6 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         })
     }
 
-    pub(crate) fn lower_path(
-        &mut self,
-        id: NodeId,
-        p: &Path,
-        param_mode: ParamMode,
-    ) -> &'hir hir::Path<'hir> {
-        let res = self.expect_full_res(id);
-        let res = self.lower_res(res);
-        self.lower_path_extra(res, p, param_mode)
-    }
-
     pub(crate) fn lower_path_segment(
         &mut self,
         path_span: Span,
@@ -185,13 +174,15 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         itctx: &ImplTraitContext,
     ) -> hir::PathSegment<'hir> {
         debug!("path_span: {:?}, lower_path_segment(segment: {:?})", path_span, segment,);
-        let (mut generic_args, infer_args) = if let Some(ref generic_args) = segment.args {
-            match **generic_args {
-                GenericArgs::AngleBracketed(ref data) => {
+        let (mut generic_args, infer_args) = if let Some(generic_args) = segment.args.as_deref() {
+            match generic_args {
+                GenericArgs::AngleBracketed(data) => {
                     self.lower_angle_bracketed_parameter_data(data, param_mode, itctx)
                 }
-                GenericArgs::Parenthesized(ref data) => match parenthesized_generic_args {
-                    ParenthesizedGenericArgs::Ok => self.lower_parenthesized_parameter_data(data),
+                GenericArgs::Parenthesized(data) => match parenthesized_generic_args {
+                    ParenthesizedGenericArgs::Ok => {
+                        self.lower_parenthesized_parameter_data(data, itctx)
+                    }
                     ParenthesizedGenericArgs::Err => {
                         // Suggest replacing parentheses with angle brackets `Trait(params...)` to `Trait<params...>`
                         let sub = if !data.inputs.is_empty() {
@@ -307,7 +298,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                 let id = NodeId::from_u32(i);
                 let l = self.lower_lifetime(&Lifetime {
                     id,
-                    ident: Ident::new(kw::UnderscoreLifetime, elided_lifetime_span),
+                    ident: Ident::new(kw::Empty, elided_lifetime_span),
                 });
                 GenericArg::Lifetime(l)
             }),
@@ -344,6 +335,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     fn lower_parenthesized_parameter_data(
         &mut self,
         data: &ParenthesizedArgs,
+        itctx: &ImplTraitContext,
     ) -> (GenericArgsCtor<'hir>, bool) {
         // Switch to `PassThrough` mode for anonymous lifetimes; this
         // means that we permit things like `&Ref<T>`, where `Ref` has
@@ -355,6 +347,24 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             self.lower_ty_direct(ty, &ImplTraitContext::Disallowed(ImplTraitPosition::FnTraitParam))
         }));
         let output_ty = match output {
+            // Only allow `impl Trait` in return position. i.e.:
+            // ```rust
+            // fn f(_: impl Fn() -> impl Debug) -> impl Fn() -> impl Debug
+            // //      disallowed --^^^^^^^^^^        allowed --^^^^^^^^^^
+            // ```
+            FnRetTy::Ty(ty) if matches!(itctx, ImplTraitContext::ReturnPositionOpaqueTy { .. }) => {
+                if self.tcx.features().impl_trait_in_fn_trait_return {
+                    self.lower_ty(&ty, itctx)
+                } else {
+                    self.lower_ty(
+                        &ty,
+                        &ImplTraitContext::FeatureGated(
+                            ImplTraitPosition::FnTraitReturn,
+                            sym::impl_trait_in_fn_trait_return,
+                        ),
+                    )
+                }
+            }
             FnRetTy::Ty(ty) => {
                 self.lower_ty(&ty, &ImplTraitContext::Disallowed(ImplTraitPosition::FnTraitReturn))
             }
diff --git a/compiler/rustc_ast_passes/src/ast_validation.rs b/compiler/rustc_ast_passes/src/ast_validation.rs
index 036643244..eb9c841d8 100644
--- a/compiler/rustc_ast_passes/src/ast_validation.rs
+++ b/compiler/rustc_ast_passes/src/ast_validation.rs
@@ -209,7 +209,7 @@ impl<'a> AstValidator<'a> {
 
     // Mirrors `visit::walk_ty`, but tracks relevant state.
     fn walk_ty(&mut self, t: &'a Ty) {
-        match t.kind {
+        match &t.kind {
             TyKind::ImplTrait(..) => {
                 self.with_impl_trait(Some(t.span), |this| visit::walk_ty(this, t))
             }
@@ -217,7 +217,7 @@ impl<'a> AstValidator<'a> {
                 .with_banned_tilde_const(DisallowTildeConstContext::TraitObject, |this| {
                     visit::walk_ty(this, t)
                 }),
-            TyKind::Path(ref qself, ref path) => {
+            TyKind::Path(qself, path) => {
                 // We allow these:
                 //  - `Option<impl Trait>`
                 //  - `option::Option<impl Trait>`
@@ -231,7 +231,7 @@ impl<'a> AstValidator<'a> {
                 // (for cases like `<impl Trait>::Foo>`)
                 // but we allow `impl Trait` in `GenericArgs`
                 // iff there are no more PathSegments.
-                if let Some(ref qself) = *qself {
+                if let Some(qself) = qself {
                     // `impl Trait` in `qself` is always illegal
                     self.with_banned_impl_trait(|this| this.visit_ty(&qself.ty));
                 }
@@ -738,8 +738,8 @@ impl<'a> AstValidator<'a> {
     }
 
     fn visit_ty_common(&mut self, ty: &'a Ty) {
-        match ty.kind {
-            TyKind::BareFn(ref bfty) => {
+        match &ty.kind {
+            TyKind::BareFn(bfty) => {
                 self.check_fn_decl(&bfty.decl, SelfSemantic::No);
                 Self::check_decl_no_pat(&bfty.decl, |span, _, _| {
                     struct_span_err!(
@@ -756,10 +756,10 @@ impl<'a> AstValidator<'a> {
                     self.maybe_lint_missing_abi(sig_span, ty.id);
                 }
             }
-            TyKind::TraitObject(ref bounds, ..) => {
+            TyKind::TraitObject(bounds, ..) => {
                 let mut any_lifetime_bounds = false;
                 for bound in bounds {
-                    if let GenericBound::Outlives(ref lifetime) = *bound {
+                    if let GenericBound::Outlives(lifetime) = bound {
                         if any_lifetime_bounds {
                             struct_span_err!(
                                 self.session,
@@ -774,7 +774,7 @@ impl<'a> AstValidator<'a> {
                     }
                 }
             }
-            TyKind::ImplTrait(_, ref bounds) => {
+            TyKind::ImplTrait(_, bounds) => {
                 if self.is_impl_trait_banned {
                     struct_span_err!(
                         self.session,
@@ -842,8 +842,8 @@ fn validate_generic_param_order(
         let (kind, bounds, span) = (&param.kind, &param.bounds, ident.span);
         let (ord_kind, ident) = match &param.kind {
             GenericParamKind::Lifetime => (ParamKindOrd::Lifetime, ident.to_string()),
-            GenericParamKind::Type { default: _ } => (ParamKindOrd::TypeOrConst, ident.to_string()),
-            GenericParamKind::Const { ref ty, kw_span: _, default: _ } => {
+            GenericParamKind::Type { .. } => (ParamKindOrd::TypeOrConst, ident.to_string()),
+            GenericParamKind::Const { ty, .. } => {
                 let ty = pprust::ty_to_string(ty);
                 (ParamKindOrd::TypeOrConst, format!("const {}: {}", ident, ty))
             }
@@ -912,7 +912,7 @@ fn validate_generic_param_order(
 
 impl<'a> Visitor<'a> for AstValidator<'a> {
     fn visit_attribute(&mut self, attr: &Attribute) {
-        validate_attr::check_meta(&self.session.parse_sess, attr);
+        validate_attr::check_attr(&self.session.parse_sess, attr);
     }
 
     fn visit_expr(&mut self, expr: &'a Expr) {
@@ -948,8 +948,8 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                 }
                 ExprKind::Paren(local_expr) => {
                     fn has_let_expr(expr: &Expr) -> bool {
-                        match expr.kind {
-                            ExprKind::Binary(_, ref lhs, ref rhs) => has_let_expr(lhs) || has_let_expr(rhs),
+                        match &expr.kind {
+                            ExprKind::Binary(_, lhs, rhs) => has_let_expr(lhs) || has_let_expr(rhs),
                             ExprKind::Let(..) => true,
                             _ => false,
                         }
@@ -1005,18 +1005,18 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
             self.check_nomangle_item_asciionly(item.ident, item.span);
         }
 
-        match item.kind {
+        match &item.kind {
             ItemKind::Impl(box Impl {
                 unsafety,
                 polarity,
                 defaultness: _,
                 constness,
-                ref generics,
-                of_trait: Some(ref t),
-                ref self_ty,
-                ref items,
+                generics,
+                of_trait: Some(t),
+                self_ty,
+                items,
             }) => {
-                self.with_in_trait_impl(true, Some(constness), |this| {
+                self.with_in_trait_impl(true, Some(*constness), |this| {
                     this.invalid_visibility(&item.vis, None);
                     if let TyKind::Err = self_ty.kind {
                         this.err_handler()
@@ -1027,7 +1027,8 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                             .help("use `auto trait Trait {}` instead")
                             .emit();
                     }
-                    if let (Unsafe::Yes(span), ImplPolarity::Negative(sp)) = (unsafety, polarity) {
+                    if let (&Unsafe::Yes(span), &ImplPolarity::Negative(sp)) = (unsafety, polarity)
+                    {
                         struct_span_err!(
                             this.session,
                             sp.to(t.path.span),
@@ -1051,6 +1052,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
 
                     walk_list!(this, visit_assoc_item, items, AssocCtxt::Impl);
                 });
+                walk_list!(self, visit_attribute, &item.attrs);
                 return; // Avoid visiting again.
             }
             ItemKind::Impl(box Impl {
@@ -1060,7 +1062,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                 constness,
                 generics: _,
                 of_trait: None,
-                ref self_ty,
+                self_ty,
                 items: _,
             }) => {
                 let error = |annotation_span, annotation| {
@@ -1077,25 +1079,25 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                     &item.vis,
                     Some(InvalidVisibilityNote::IndividualImplItems),
                 );
-                if let Unsafe::Yes(span) = unsafety {
+                if let &Unsafe::Yes(span) = unsafety {
                     error(span, "unsafe").code(error_code!(E0197)).emit();
                 }
-                if let ImplPolarity::Negative(span) = polarity {
+                if let &ImplPolarity::Negative(span) = polarity {
                     error(span, "negative").emit();
                 }
-                if let Defaultness::Default(def_span) = defaultness {
+                if let &Defaultness::Default(def_span) = defaultness {
                     error(def_span, "`default`")
                         .note("only trait implementations may be annotated with `default`")
                         .emit();
                 }
-                if let Const::Yes(span) = constness {
+                if let &Const::Yes(span) = constness {
                     error(span, "`const`")
                         .note("only trait implementations may be annotated with `const`")
                         .emit();
                 }
             }
-            ItemKind::Fn(box Fn { defaultness, ref sig, ref generics, ref body }) => {
-                self.check_defaultness(item.span, defaultness);
+            ItemKind::Fn(box Fn { defaultness, sig, generics, body }) => {
+                self.check_defaultness(item.span, *defaultness);
 
                 if body.is_none() {
                     self.session.emit_err(FnWithoutBody {
@@ -1131,7 +1133,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                     &item.vis,
                     Some(InvalidVisibilityNote::IndividualForeignItems),
                 );
-                if let Unsafe::Yes(span) = unsafety {
+                if let &Unsafe::Yes(span) = unsafety {
                     self.err_handler().span_err(span, "extern block cannot be declared unsafe");
                 }
                 if abi.is_none() {
@@ -1141,7 +1143,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                 self.extern_mod = old_item;
                 return; // Avoid visiting again.
             }
-            ItemKind::Enum(ref def, _) => {
+            ItemKind::Enum(def, _) => {
                 for variant in &def.variants {
                     self.invalid_visibility(&variant.vis, None);
                     for field in variant.data.fields() {
@@ -1149,8 +1151,8 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                     }
                 }
             }
-            ItemKind::Trait(box Trait { is_auto, ref generics, ref bounds, ref items, .. }) => {
-                if is_auto == IsAuto::Yes {
+            ItemKind::Trait(box Trait { is_auto, generics, bounds, items, .. }) => {
+                if *is_auto == IsAuto::Yes {
                     // Auto traits cannot have generics, super traits nor contain items.
                     self.deny_generic_params(generics, item.ident.span);
                     self.deny_super_traits(bounds, item.ident.span);
@@ -1168,10 +1170,10 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                 });
                 walk_list!(self, visit_assoc_item, items, AssocCtxt::Trait);
                 walk_list!(self, visit_attribute, &item.attrs);
-                return;
+                return; // Avoid visiting again
             }
-            ItemKind::Mod(unsafety, ref mod_kind) => {
-                if let Unsafe::Yes(span) = unsafety {
+            ItemKind::Mod(unsafety, mod_kind) => {
+                if let &Unsafe::Yes(span) = unsafety {
                     self.err_handler().span_err(span, "module cannot be declared unsafe");
                 }
                 // Ensure that `path` attributes on modules are recorded as used (cf. issue #35584).
@@ -1181,13 +1183,13 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                     self.check_mod_file_item_asciionly(item.ident);
                 }
             }
-            ItemKind::Union(ref vdata, ..) => {
+            ItemKind::Union(vdata, ..) => {
                 if vdata.fields().is_empty() {
                     self.err_handler().span_err(item.span, "unions cannot have zero fields");
                 }
             }
             ItemKind::Const(def, .., None) => {
-                self.check_defaultness(item.span, def);
+                self.check_defaultness(item.span, *def);
                 self.session.emit_err(ConstWithoutBody {
                     span: item.span,
                     replace_span: self.ending_semi_or_hi(item.span),
@@ -1199,14 +1201,8 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                     replace_span: self.ending_semi_or_hi(item.span),
                 });
             }
-            ItemKind::TyAlias(box TyAlias {
-                defaultness,
-                where_clauses,
-                ref bounds,
-                ref ty,
-                ..
-            }) => {
-                self.check_defaultness(item.span, defaultness);
+            ItemKind::TyAlias(box TyAlias { defaultness, where_clauses, bounds, ty, .. }) => {
+                self.check_defaultness(item.span, *defaultness);
                 if ty.is_none() {
                     self.session.emit_err(TyAliasWithoutBody {
                         span: item.span,
@@ -1265,8 +1261,8 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
 
     // Mirrors `visit::walk_generic_args`, but tracks relevant state.
     fn visit_generic_args(&mut self, generic_args: &'a GenericArgs) {
-        match *generic_args {
-            GenericArgs::AngleBracketed(ref data) => {
+        match generic_args {
+            GenericArgs::AngleBracketed(data) => {
                 self.check_generic_args_before_constraints(data);
 
                 for arg in &data.args {
@@ -1282,7 +1278,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                     }
                 }
             }
-            GenericArgs::Parenthesized(ref data) => {
+            GenericArgs::Parenthesized(data) => {
                 walk_list!(self, visit_ty, &data.inputs);
                 if let FnRetTy::Ty(ty) = &data.output {
                     // `-> Foo` syntax is essentially an associated type binding,
@@ -1318,7 +1314,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
         validate_generic_param_order(self.err_handler(), &generics.params, generics.span);
 
         for predicate in &generics.where_clause.predicates {
-            if let WherePredicate::EqPredicate(ref predicate) = *predicate {
+            if let WherePredicate::EqPredicate(predicate) = predicate {
                 deny_equality_constraints(self, predicate, generics);
             }
         }
@@ -1367,7 +1363,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
     }
 
     fn visit_param_bound(&mut self, bound: &'a GenericBound, ctxt: BoundKind) {
-        if let GenericBound::Trait(ref poly, modify) = *bound {
+        if let GenericBound::Trait(poly, modify) = bound {
             match (ctxt, modify) {
                 (BoundKind::SuperTraits, TraitBoundModifier::Maybe) => {
                     let mut err = self
@@ -1572,8 +1568,8 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
             self.check_item_named(item.ident, "const");
         }
 
-        match item.kind {
-            AssocItemKind::Type(box TyAlias { ref generics, ref bounds, ref ty, .. })
+        match &item.kind {
+            AssocItemKind::Type(box TyAlias { generics, bounds, ty, .. })
                 if ctxt == AssocCtxt::Trait =>
             {
                 self.visit_vis(&item.vis);
@@ -1585,7 +1581,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                 });
                 walk_list!(self, visit_ty, ty);
             }
-            AssocItemKind::Fn(box Fn { ref sig, ref generics, ref body, .. })
+            AssocItemKind::Fn(box Fn { sig, generics, body, .. })
                 if self.in_const_trait_impl
                     || ctxt == AssocCtxt::Trait
                     || matches!(sig.header.constness, Const::Yes(_)) =>
@@ -1636,7 +1632,7 @@ fn deny_equality_constraints(
                                     // Remove `Bar` from `Foo::Bar`.
                                     assoc_path.segments.pop();
                                     let len = assoc_path.segments.len() - 1;
-                                    let gen_args = args.as_ref().map(|p| (**p).clone());
+                                    let gen_args = args.as_deref().cloned();
                                     // Build `<Bar = RhsTy>`.
                                     let arg = AngleBracketedArg::Constraint(AssocConstraint {
                                         id: rustc_ast::node_id::DUMMY_NODE_ID,
diff --git a/compiler/rustc_ast_passes/src/feature_gate.rs b/compiler/rustc_ast_passes/src/feature_gate.rs
index 546010135..32f45f8b5 100644
--- a/compiler/rustc_ast_passes/src/feature_gate.rs
+++ b/compiler/rustc_ast_passes/src/feature_gate.rs
@@ -198,8 +198,8 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
     }
 
     fn visit_item(&mut self, i: &'a ast::Item) {
-        match i.kind {
-            ast::ItemKind::ForeignMod(ref foreign_module) => {
+        match &i.kind {
+            ast::ItemKind::ForeignMod(foreign_module) => {
                 if let Some(abi) = foreign_module.abi {
                     self.check_abi(abi, ast::Const::No);
                 }
@@ -233,8 +233,8 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
                 }
             }
 
-            ast::ItemKind::Impl(box ast::Impl { polarity, defaultness, ref of_trait, .. }) => {
-                if let ast::ImplPolarity::Negative(span) = polarity {
+            ast::ItemKind::Impl(box ast::Impl { polarity, defaultness, of_trait, .. }) => {
+                if let &ast::ImplPolarity::Negative(span) = polarity {
                     gate_feature_post!(
                         &self,
                         negative_impls,
@@ -267,7 +267,7 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
                 gate_feature_post!(&self, decl_macro, i.span, msg);
             }
 
-            ast::ItemKind::TyAlias(box ast::TyAlias { ty: Some(ref ty), .. }) => {
+            ast::ItemKind::TyAlias(box ast::TyAlias { ty: Some(ty), .. }) => {
                 self.check_impl_trait(&ty)
             }
 
@@ -302,8 +302,8 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
     }
 
     fn visit_ty(&mut self, ty: &'a ast::Ty) {
-        match ty.kind {
-            ast::TyKind::BareFn(ref bare_fn_ty) => {
+        match &ty.kind {
+            ast::TyKind::BareFn(bare_fn_ty) => {
                 // Function pointers cannot be `const`
                 self.check_extern(bare_fn_ty.ext, ast::Const::No);
             }
@@ -319,7 +319,7 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
     }
 
     fn visit_fn_ret_ty(&mut self, ret_ty: &'a ast::FnRetTy) {
-        if let ast::FnRetTy::Ty(ref output_ty) = *ret_ty {
+        if let ast::FnRetTy::Ty(output_ty) = ret_ty {
             if let ast::TyKind::Never = output_ty.kind {
                 // Do nothing.
             } else {
@@ -455,9 +455,9 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
     }
 
     fn visit_assoc_item(&mut self, i: &'a ast::AssocItem, ctxt: AssocCtxt) {
-        let is_fn = match i.kind {
+        let is_fn = match &i.kind {
             ast::AssocItemKind::Fn(_) => true,
-            ast::AssocItemKind::Type(box ast::TyAlias { ref ty, .. }) => {
+            ast::AssocItemKind::Type(box ast::TyAlias { ty, .. }) => {
                 if let (Some(_), AssocCtxt::Trait) = (ty, ctxt) {
                     gate_feature_post!(
                         &self,
diff --git a/compiler/rustc_ast_pretty/src/helpers.rs b/compiler/rustc_ast_pretty/src/helpers.rs
index 5ec71cddf..c3e0eccd3 100644
--- a/compiler/rustc_ast_pretty/src/helpers.rs
+++ b/compiler/rustc_ast_pretty/src/helpers.rs
@@ -36,8 +36,8 @@ impl Printer {
         self.nbsp()
     }
 
-    // Synthesizes a comment that was not textually present in the original
-    // source file.
+    /// Synthesizes a comment that was not textually present in the original
+    /// source file.
     pub fn synth_comment(&mut self, text: impl Into<Cow<'static, str>>) {
         self.word("/*");
         self.space();
diff --git a/compiler/rustc_ast_pretty/src/pprust/state.rs b/compiler/rustc_ast_pretty/src/pprust/state.rs
index b87c6f78d..d3d8431c1 100644
--- a/compiler/rustc_ast_pretty/src/pprust/state.rs
+++ b/compiler/rustc_ast_pretty/src/pprust/state.rs
@@ -11,16 +11,15 @@ use rustc_ast::tokenstream::{TokenStream, TokenTree};
 use rustc_ast::util::classify;
 use rustc_ast::util::comments::{gather_comments, Comment, CommentStyle};
 use rustc_ast::util::parser;
-use rustc_ast::{self as ast, BlockCheckMode, Mutability, PatKind, RangeEnd, RangeSyntax};
-use rustc_ast::{attr, BindingAnnotation, ByRef, Term};
-use rustc_ast::{GenericArg, MacArgs, MacArgsEq};
-use rustc_ast::{GenericBound, SelfKind, TraitBoundModifier};
+use rustc_ast::{self as ast, AttrArgs, AttrArgsEq, BlockCheckMode, PatKind};
+use rustc_ast::{attr, BindingAnnotation, ByRef, DelimArgs, RangeEnd, RangeSyntax, Term};
+use rustc_ast::{GenericArg, GenericBound, SelfKind, TraitBoundModifier};
 use rustc_ast::{InlineAsmOperand, InlineAsmRegOrRegClass};
 use rustc_ast::{InlineAsmOptions, InlineAsmTemplatePiece};
 use rustc_span::edition::Edition;
 use rustc_span::source_map::{SourceMap, Spanned};
 use rustc_span::symbol::{kw, sym, Ident, IdentPrinter, Symbol};
-use rustc_span::{BytePos, FileName, Span};
+use rustc_span::{BytePos, FileName, Span, DUMMY_SP};
 
 use rustc_ast::attr::AttrIdGenerator;
 use std::borrow::Cow;
@@ -65,6 +64,7 @@ impl<'a> Comments<'a> {
         Comments { sm, comments, current: 0 }
     }
 
+    // FIXME: This shouldn't probably clone lmao
     pub fn next(&self) -> Option<Comment> {
         self.comments.get(self.current).cloned()
     }
@@ -120,17 +120,20 @@ pub fn print_crate<'a>(
         // of the feature gate, so we fake them up here.
 
         // `#![feature(prelude_import)]`
-        let pi_nested = attr::mk_nested_word_item(Ident::with_dummy_span(sym::prelude_import));
-        let list = attr::mk_list_item(Ident::with_dummy_span(sym::feature), vec![pi_nested]);
-        let fake_attr = attr::mk_attr_inner(g, list);
+        let fake_attr = attr::mk_attr_nested_word(
+            g,
+            ast::AttrStyle::Inner,
+            sym::feature,
+            sym::prelude_import,
+            DUMMY_SP,
+        );
         s.print_attribute(&fake_attr);
 
         // Currently, in Rust 2018 we don't have `extern crate std;` at the crate
         // root, so this is not needed, and actually breaks things.
         if edition == Edition::Edition2015 {
             // `#![no_std]`
-            let no_std_meta = attr::mk_word_item(Ident::with_dummy_span(sym::no_std));
-            let fake_attr = attr::mk_attr_inner(g, no_std_meta);
+            let fake_attr = attr::mk_attr_word(g, ast::AttrStyle::Inner, sym::no_std, DUMMY_SP);
             s.print_attribute(&fake_attr);
         }
     }
@@ -269,10 +272,10 @@ pub trait PrintState<'a>: std::ops::Deref<Target = pp::Printer> + std::ops::Dere
 
     fn maybe_print_comment(&mut self, pos: BytePos) -> bool {
         let mut has_comment = false;
-        while let Some(ref cmnt) = self.next_comment() {
+        while let Some(cmnt) = self.next_comment() {
             if cmnt.pos < pos {
                 has_comment = true;
-                self.print_comment(cmnt);
+                self.print_comment(&cmnt);
             } else {
                 break;
             }
@@ -367,14 +370,18 @@ pub trait PrintState<'a>: std::ops::Deref<Target = pp::Printer> + std::ops::Dere
         if self.next_comment().is_none() {
             self.hardbreak();
         }
-        while let Some(ref cmnt) = self.next_comment() {
-            self.print_comment(cmnt)
+        while let Some(cmnt) = self.next_comment() {
+            self.print_comment(&cmnt)
         }
     }
 
-    fn print_literal(&mut self, lit: &ast::Lit) {
-        self.maybe_print_comment(lit.span.lo());
-        self.word(lit.token_lit.to_string())
+    fn print_meta_item_lit(&mut self, lit: &ast::MetaItemLit) {
+        self.print_token_literal(lit.token_lit, lit.span)
+    }
+
+    fn print_token_literal(&mut self, token_lit: token::Lit, span: Span) {
+        self.maybe_print_comment(span.lo());
+        self.word(token_lit.to_string())
     }
 
     fn print_string(&mut self, st: &str, style: ast::StrStyle) {
@@ -443,8 +450,8 @@ pub trait PrintState<'a>: std::ops::Deref<Target = pp::Printer> + std::ops::Dere
             self.hardbreak_if_not_bol();
         }
         self.maybe_print_comment(attr.span.lo());
-        match attr.kind {
-            ast::AttrKind::Normal(ref normal) => {
+        match &attr.kind {
+            ast::AttrKind::Normal(normal) => {
                 match attr.style {
                     ast::AttrStyle::Inner => self.word("#!["),
                     ast::AttrStyle::Outer => self.word("#["),
@@ -453,7 +460,7 @@ pub trait PrintState<'a>: std::ops::Deref<Target = pp::Printer> + std::ops::Dere
                 self.word("]");
             }
             ast::AttrKind::DocComment(comment_kind, data) => {
-                self.word(doc_comment_to_string(comment_kind, attr.style, data));
+                self.word(doc_comment_to_string(*comment_kind, attr.style, *data));
                 self.hardbreak()
             }
         }
@@ -462,30 +469,30 @@ pub trait PrintState<'a>: std::ops::Deref<Target = pp::Printer> + std::ops::Dere
     fn print_attr_item(&mut self, item: &ast::AttrItem, span: Span) {
         self.ibox(0);
         match &item.args {
-            MacArgs::Delimited(_, delim, tokens) => self.print_mac_common(
+            AttrArgs::Delimited(DelimArgs { dspan: _, delim, tokens }) => self.print_mac_common(
                 Some(MacHeader::Path(&item.path)),
                 false,
                 None,
-                Some(delim.to_token()),
+                delim.to_token(),
                 tokens,
                 true,
                 span,
             ),
-            MacArgs::Empty => {
+            AttrArgs::Empty => {
                 self.print_path(&item.path, false, 0);
             }
-            MacArgs::Eq(_, MacArgsEq::Ast(expr)) => {
+            AttrArgs::Eq(_, AttrArgsEq::Ast(expr)) => {
                 self.print_path(&item.path, false, 0);
                 self.space();
                 self.word_space("=");
                 let token_str = self.expr_to_string(expr);
                 self.word(token_str);
             }
-            MacArgs::Eq(_, MacArgsEq::Hir(lit)) => {
+            AttrArgs::Eq(_, AttrArgsEq::Hir(lit)) => {
                 self.print_path(&item.path, false, 0);
                 self.space();
                 self.word_space("=");
-                let token_str = self.literal_to_string(lit);
+                let token_str = self.meta_item_lit_to_string(lit);
                 self.word(token_str);
             }
         }
@@ -494,25 +501,25 @@ pub trait PrintState<'a>: std::ops::Deref<Target = pp::Printer> + std::ops::Dere
 
     fn print_meta_list_item(&mut self, item: &ast::NestedMetaItem) {
         match item {
-            ast::NestedMetaItem::MetaItem(ref mi) => self.print_meta_item(mi),
-            ast::NestedMetaItem::Literal(ref lit) => self.print_literal(lit),
+            ast::NestedMetaItem::MetaItem(mi) => self.print_meta_item(mi),
+            ast::NestedMetaItem::Lit(lit) => self.print_meta_item_lit(lit),
         }
     }
 
     fn print_meta_item(&mut self, item: &ast::MetaItem) {
         self.ibox(INDENT_UNIT);
-        match item.kind {
+        match &item.kind {
             ast::MetaItemKind::Word => self.print_path(&item.path, false, 0),
-            ast::MetaItemKind::NameValue(ref value) => {
+            ast::MetaItemKind::NameValue(value) => {
                 self.print_path(&item.path, false, 0);
                 self.space();
                 self.word_space("=");
-                self.print_literal(value);
+                self.print_meta_item_lit(value);
             }
-            ast::MetaItemKind::List(ref items) => {
+            ast::MetaItemKind::List(items) => {
                 self.print_path(&item.path, false, 0);
                 self.popen();
-                self.commasep(Consistent, &items, |s, i| s.print_meta_list_item(i));
+                self.commasep(Consistent, items, |s, i| s.print_meta_list_item(i));
                 self.pclose();
             }
         }
@@ -529,7 +536,7 @@ pub trait PrintState<'a>: std::ops::Deref<Target = pp::Printer> + std::ops::Dere
     fn print_tt(&mut self, tt: &TokenTree, convert_dollar_crate: bool) {
         match tt {
             TokenTree::Token(token, _) => {
-                let token_str = self.token_to_string_ext(&token, convert_dollar_crate);
+                let token_str = self.token_to_string_ext(token, convert_dollar_crate);
                 self.word(token_str);
                 if let token::DocComment(..) = token.kind {
                     self.hardbreak()
@@ -540,7 +547,7 @@ pub trait PrintState<'a>: std::ops::Deref<Target = pp::Printer> + std::ops::Dere
                     None,
                     false,
                     None,
-                    Some(*delim),
+                    *delim,
                     tts,
                     convert_dollar_crate,
                     dspan.entire(),
@@ -566,12 +573,12 @@ pub trait PrintState<'a>: std::ops::Deref<Target = pp::Printer> + std::ops::Dere
         header: Option<MacHeader<'_>>,
         has_bang: bool,
         ident: Option<Ident>,
-        delim: Option<Delimiter>,
+        delim: Delimiter,
         tts: &TokenStream,
         convert_dollar_crate: bool,
         span: Span,
     ) {
-        if delim == Some(Delimiter::Brace) {
+        if delim == Delimiter::Brace {
             self.cbox(INDENT_UNIT);
         }
         match header {
@@ -587,7 +594,7 @@ pub trait PrintState<'a>: std::ops::Deref<Target = pp::Printer> + std::ops::Dere
             self.print_ident(ident);
         }
         match delim {
-            Some(Delimiter::Brace) => {
+            Delimiter::Brace => {
                 if header.is_some() || has_bang || ident.is_some() {
                     self.nbsp();
                 }
@@ -601,7 +608,7 @@ pub trait PrintState<'a>: std::ops::Deref<Target = pp::Printer> + std::ops::Dere
                 let empty = tts.is_empty();
                 self.bclose(span, empty);
             }
-            Some(delim) => {
+            delim => {
                 let token_str = self.token_kind_to_string(&token::OpenDelim(delim));
                 self.word(token_str);
                 self.ibox(0);
@@ -610,11 +617,6 @@ pub trait PrintState<'a>: std::ops::Deref<Target = pp::Printer> + std::ops::Dere
                 let token_str = self.token_kind_to_string(&token::CloseDelim(delim));
                 self.word(token_str);
             }
-            None => {
-                self.ibox(0);
-                self.print_tts(tts, convert_dollar_crate);
-                self.end();
-            }
         }
     }
 
@@ -635,8 +637,8 @@ pub trait PrintState<'a>: std::ops::Deref<Target = pp::Printer> + std::ops::Dere
             Some(MacHeader::Keyword(kw)),
             has_bang,
             Some(*ident),
-            macro_def.body.delim(),
-            &macro_def.body.inner_tokens(),
+            macro_def.body.delim.to_token(),
+            &macro_def.body.tokens.clone(),
             true,
             sp,
         );
@@ -659,7 +661,7 @@ pub trait PrintState<'a>: std::ops::Deref<Target = pp::Printer> + std::ops::Dere
     fn print_path_segment(&mut self, segment: &ast::PathSegment, colons_before_params: bool) {
         if segment.ident.name != kw::PathRoot {
             self.print_ident(segment.ident);
-            if let Some(ref args) = segment.args {
+            if let Some(args) = &segment.args {
                 self.print_generic_args(args, colons_before_params);
             }
         }
@@ -714,19 +716,19 @@ pub trait PrintState<'a>: std::ops::Deref<Target = pp::Printer> + std::ops::Dere
     }
 
     fn nonterminal_to_string(&self, nt: &Nonterminal) -> String {
-        match *nt {
-            token::NtExpr(ref e) => self.expr_to_string(e),
-            token::NtMeta(ref e) => self.attr_item_to_string(e),
-            token::NtTy(ref e) => self.ty_to_string(e),
-            token::NtPath(ref e) => self.path_to_string(e),
-            token::NtItem(ref e) => self.item_to_string(e),
-            token::NtBlock(ref e) => self.block_to_string(e),
-            token::NtStmt(ref e) => self.stmt_to_string(e),
-            token::NtPat(ref e) => self.pat_to_string(e),
-            token::NtIdent(e, is_raw) => IdentPrinter::for_ast_ident(e, is_raw).to_string(),
+        match nt {
+            token::NtExpr(e) => self.expr_to_string(e),
+            token::NtMeta(e) => self.attr_item_to_string(e),
+            token::NtTy(e) => self.ty_to_string(e),
+            token::NtPath(e) => self.path_to_string(e),
+            token::NtItem(e) => self.item_to_string(e),
+            token::NtBlock(e) => self.block_to_string(e),
+            token::NtStmt(e) => self.stmt_to_string(e),
+            token::NtPat(e) => self.pat_to_string(e),
+            token::NtIdent(e, is_raw) => IdentPrinter::for_ast_ident(*e, *is_raw).to_string(),
             token::NtLifetime(e) => e.to_string(),
-            token::NtLiteral(ref e) => self.expr_to_string(e),
-            token::NtVis(ref e) => self.vis_to_string(e),
+            token::NtLiteral(e) => self.expr_to_string(e),
+            token::NtVis(e) => self.vis_to_string(e),
         }
     }
 
@@ -827,8 +829,8 @@ pub trait PrintState<'a>: std::ops::Deref<Target = pp::Printer> + std::ops::Dere
         Self::to_string(|s| s.print_expr(e))
     }
 
-    fn literal_to_string(&self, lit: &ast::Lit) -> String {
-        Self::to_string(|s| s.print_literal(lit))
+    fn meta_item_lit_to_string(&self, lit: &ast::MetaItemLit) -> String {
+        Self::to_string(|s| s.print_meta_item_lit(lit))
     }
 
     fn tt_to_string(&self, tt: &TokenTree) -> String {
@@ -919,8 +921,8 @@ impl<'a> PrintState<'a> for State<'a> {
             self.word("::")
         }
 
-        match *args {
-            ast::GenericArgs::AngleBracketed(ref data) => {
+        match args {
+            ast::GenericArgs::AngleBracketed(data) => {
                 self.word("<");
                 self.commasep(Inconsistent, &data.args, |s, arg| match arg {
                     ast::AngleBracketedArg::Arg(a) => s.print_generic_arg(a),
@@ -929,7 +931,7 @@ impl<'a> PrintState<'a> for State<'a> {
                 self.word(">")
             }
 
-            ast::GenericArgs::Parenthesized(ref data) => {
+            ast::GenericArgs::Parenthesized(data) => {
                 self.word("(");
                 self.commasep(Inconsistent, &data.inputs, |s, ty| s.print_type(ty));
                 self.word(")");
@@ -996,7 +998,7 @@ impl<'a> State<'a> {
             ast::AssocConstraintKind::Bound { bounds } => {
                 if !bounds.is_empty() {
                     self.word_nbsp(":");
-                    self.print_type_bounds(&bounds);
+                    self.print_type_bounds(bounds);
                 }
             }
         }
@@ -1013,17 +1015,17 @@ impl<'a> State<'a> {
     pub fn print_type(&mut self, ty: &ast::Ty) {
         self.maybe_print_comment(ty.span.lo());
         self.ibox(0);
-        match ty.kind {
-            ast::TyKind::Slice(ref ty) => {
+        match &ty.kind {
+            ast::TyKind::Slice(ty) => {
                 self.word("[");
                 self.print_type(ty);
                 self.word("]");
             }
-            ast::TyKind::Ptr(ref mt) => {
+            ast::TyKind::Ptr(mt) => {
                 self.word("*");
                 self.print_mt(mt, true);
             }
-            ast::TyKind::Rptr(ref lifetime, ref mt) => {
+            ast::TyKind::Rptr(lifetime, mt) => {
                 self.word("&");
                 self.print_opt_lifetime(lifetime);
                 self.print_mt(mt, false);
@@ -1031,44 +1033,44 @@ impl<'a> State<'a> {
             ast::TyKind::Never => {
                 self.word("!");
             }
-            ast::TyKind::Tup(ref elts) => {
+            ast::TyKind::Tup(elts) => {
                 self.popen();
-                self.commasep(Inconsistent, &elts, |s, ty| s.print_type(ty));
+                self.commasep(Inconsistent, elts, |s, ty| s.print_type(ty));
                 if elts.len() == 1 {
                     self.word(",");
                 }
                 self.pclose();
             }
-            ast::TyKind::Paren(ref typ) => {
+            ast::TyKind::Paren(typ) => {
                 self.popen();
                 self.print_type(typ);
                 self.pclose();
             }
-            ast::TyKind::BareFn(ref f) => {
+            ast::TyKind::BareFn(f) => {
                 self.print_ty_fn(f.ext, f.unsafety, &f.decl, None, &f.generic_params);
             }
-            ast::TyKind::Path(None, ref path) => {
+            ast::TyKind::Path(None, path) => {
                 self.print_path(path, false, 0);
             }
-            ast::TyKind::Path(Some(ref qself), ref path) => self.print_qpath(path, qself, false),
-            ast::TyKind::TraitObject(ref bounds, syntax) => {
-                if syntax == ast::TraitObjectSyntax::Dyn {
+            ast::TyKind::Path(Some(qself), path) => self.print_qpath(path, qself, false),
+            ast::TyKind::TraitObject(bounds, syntax) => {
+                if *syntax == ast::TraitObjectSyntax::Dyn {
                     self.word_nbsp("dyn");
                 }
                 self.print_type_bounds(bounds);
             }
-            ast::TyKind::ImplTrait(_, ref bounds) => {
+            ast::TyKind::ImplTrait(_, bounds) => {
                 self.word_nbsp("impl");
                 self.print_type_bounds(bounds);
             }
-            ast::TyKind::Array(ref ty, ref length) => {
+            ast::TyKind::Array(ty, length) => {
                 self.word("[");
                 self.print_type(ty);
                 self.word("; ");
                 self.print_expr(&length.value);
                 self.word("]");
             }
-            ast::TyKind::Typeof(ref e) => {
+            ast::TyKind::Typeof(e) => {
                 self.word("typeof(");
                 self.print_expr(&e.value);
                 self.word(")");
@@ -1084,7 +1086,7 @@ impl<'a> State<'a> {
             ast::TyKind::ImplicitSelf => {
                 self.word("Self");
             }
-            ast::TyKind::MacCall(ref m) => {
+            ast::TyKind::MacCall(m) => {
                 self.print_mac(m);
             }
             ast::TyKind::CVarArgs => {
@@ -1113,8 +1115,8 @@ impl<'a> State<'a> {
 
     pub(crate) fn print_stmt(&mut self, st: &ast::Stmt) {
         self.maybe_print_comment(st.span.lo());
-        match st.kind {
-            ast::StmtKind::Local(ref loc) => {
+        match &st.kind {
+            ast::StmtKind::Local(loc) => {
                 self.print_outer_attributes(&loc.attrs);
                 self.space_if_not_bol();
                 self.ibox(INDENT_UNIT);
@@ -1137,15 +1139,15 @@ impl<'a> State<'a> {
                 self.word(";");
                 self.end(); // `let` ibox
             }
-            ast::StmtKind::Item(ref item) => self.print_item(item),
-            ast::StmtKind::Expr(ref expr) => {
+            ast::StmtKind::Item(item) => self.print_item(item),
+            ast::StmtKind::Expr(expr) => {
                 self.space_if_not_bol();
                 self.print_expr_outer_attr_style(expr, false);
                 if classify::expr_requires_semi_to_be_stmt(expr) {
                     self.word(";");
                 }
             }
-            ast::StmtKind::Semi(ref expr) => {
+            ast::StmtKind::Semi(expr) => {
                 self.space_if_not_bol();
                 self.print_expr_outer_attr_style(expr, false);
                 self.word(";");
@@ -1154,7 +1156,7 @@ impl<'a> State<'a> {
                 self.space_if_not_bol();
                 self.word(";");
             }
-            ast::StmtKind::MacCall(ref mac) => {
+            ast::StmtKind::MacCall(mac) => {
                 self.space_if_not_bol();
                 self.print_outer_attributes(&mac.attrs);
                 self.print_mac(&mac.mac);
@@ -1195,8 +1197,8 @@ impl<'a> State<'a> {
         let has_attrs = self.print_inner_attributes(attrs);
 
         for (i, st) in blk.stmts.iter().enumerate() {
-            match st.kind {
-                ast::StmtKind::Expr(ref expr) if i == blk.stmts.len() - 1 => {
+            match &st.kind {
+                ast::StmtKind::Expr(expr) if i == blk.stmts.len() - 1 => {
                     self.maybe_print_comment(st.span.lo());
                     self.space_if_not_bol();
                     self.print_expr_outer_attr_style(expr, false);
@@ -1226,8 +1228,8 @@ impl<'a> State<'a> {
             Some(MacHeader::Path(&m.path)),
             true,
             None,
-            m.args.delim(),
-            &m.args.inner_tokens(),
+            m.args.delim.to_token(),
+            &m.args.tokens.clone(),
             true,
             m.span(),
         );
@@ -1252,7 +1254,7 @@ impl<'a> State<'a> {
 
         self.popen();
         self.commasep(Consistent, &args, |s, arg| match arg {
-            AsmArg::Template(template) => s.print_string(&template, ast::StrStyle::Cooked),
+            AsmArg::Template(template) => s.print_string(template, ast::StrStyle::Cooked),
             AsmArg::Operand(op) => {
                 let print_reg_or_class = |s: &mut Self, r: &InlineAsmRegOrRegClass| match r {
                     InlineAsmRegOrRegClass::Reg(r) => s.print_symbol(*r, ast::StrStyle::Cooked),
@@ -1364,7 +1366,7 @@ impl<'a> State<'a> {
 
     pub(crate) fn print_local_decl(&mut self, loc: &ast::Local) {
         self.print_pat(&loc.pat);
-        if let Some(ref ty) = loc.ty {
+        if let Some(ty) = &loc.ty {
             self.word_space(":");
             self.print_type(ty);
         }
@@ -1388,7 +1390,7 @@ impl<'a> State<'a> {
         for item_segment in &path.segments[qself.position..] {
             self.word("::");
             self.print_ident(item_segment.ident);
-            if let Some(ref args) = item_segment.args {
+            if let Some(args) = &item_segment.args {
                 self.print_generic_args(args, colons_before_params)
             }
         }
@@ -1399,42 +1401,42 @@ impl<'a> State<'a> {
         self.ann.pre(self, AnnNode::Pat(pat));
         /* Pat isn't normalized, but the beauty of it
         is that it doesn't matter */
-        match pat.kind {
+        match &pat.kind {
             PatKind::Wild => self.word("_"),
-            PatKind::Ident(BindingAnnotation(by_ref, mutbl), ident, ref sub) => {
-                if by_ref == ByRef::Yes {
+            PatKind::Ident(BindingAnnotation(by_ref, mutbl), ident, sub) => {
+                if *by_ref == ByRef::Yes {
                     self.word_nbsp("ref");
                 }
-                if mutbl == Mutability::Mut {
+                if mutbl.is_mut() {
                     self.word_nbsp("mut");
                 }
-                self.print_ident(ident);
-                if let Some(ref p) = *sub {
+                self.print_ident(*ident);
+                if let Some(p) = sub {
                     self.space();
                     self.word_space("@");
                     self.print_pat(p);
                 }
             }
-            PatKind::TupleStruct(ref qself, ref path, ref elts) => {
+            PatKind::TupleStruct(qself, path, elts) => {
                 if let Some(qself) = qself {
                     self.print_qpath(path, qself, true);
                 } else {
                     self.print_path(path, true, 0);
                 }
                 self.popen();
-                self.commasep(Inconsistent, &elts, |s, p| s.print_pat(p));
+                self.commasep(Inconsistent, elts, |s, p| s.print_pat(p));
                 self.pclose();
             }
-            PatKind::Or(ref pats) => {
-                self.strsep("|", true, Inconsistent, &pats, |s, p| s.print_pat(p));
+            PatKind::Or(pats) => {
+                self.strsep("|", true, Inconsistent, pats, |s, p| s.print_pat(p));
             }
-            PatKind::Path(None, ref path) => {
+            PatKind::Path(None, path) => {
                 self.print_path(path, true, 0);
             }
-            PatKind::Path(Some(ref qself), ref path) => {
+            PatKind::Path(Some(qself), path) => {
                 self.print_qpath(path, qself, false);
             }
-            PatKind::Struct(ref qself, ref path, ref fields, etc) => {
+            PatKind::Struct(qself, path, fields, etc) => {
                 if let Some(qself) = qself {
                     self.print_qpath(path, qself, true);
                 } else {
@@ -1448,7 +1450,7 @@ impl<'a> State<'a> {
                 }
                 self.commasep_cmnt(
                     Consistent,
-                    &fields,
+                    fields,
                     |s, f| {
                         s.cbox(INDENT_UNIT);
                         if !f.is_shorthand {
@@ -1460,7 +1462,7 @@ impl<'a> State<'a> {
                     },
                     |f| f.pat.span,
                 );
-                if etc {
+                if *etc {
                     if !fields.is_empty() {
                         self.word_space(",");
                     }
@@ -1471,21 +1473,21 @@ impl<'a> State<'a> {
                 }
                 self.word("}");
             }
-            PatKind::Tuple(ref elts) => {
+            PatKind::Tuple(elts) => {
                 self.popen();
-                self.commasep(Inconsistent, &elts, |s, p| s.print_pat(p));
+                self.commasep(Inconsistent, elts, |s, p| s.print_pat(p));
                 if elts.len() == 1 {
                     self.word(",");
                 }
                 self.pclose();
             }
-            PatKind::Box(ref inner) => {
+            PatKind::Box(inner) => {
                 self.word("box ");
                 self.print_pat(inner);
             }
-            PatKind::Ref(ref inner, mutbl) => {
+            PatKind::Ref(inner, mutbl) => {
                 self.word("&");
-                if mutbl == Mutability::Mut {
+                if mutbl.is_mut() {
                     self.word("mut ");
                 }
                 if let PatKind::Ident(ast::BindingAnnotation::MUT, ..) = inner.kind {
@@ -1496,12 +1498,12 @@ impl<'a> State<'a> {
                     self.print_pat(inner);
                 }
             }
-            PatKind::Lit(ref e) => self.print_expr(&**e),
-            PatKind::Range(ref begin, ref end, Spanned { node: ref end_kind, .. }) => {
+            PatKind::Lit(e) => self.print_expr(e),
+            PatKind::Range(begin, end, Spanned { node: end_kind, .. }) => {
                 if let Some(e) = begin {
                     self.print_expr(e);
                 }
-                match *end_kind {
+                match end_kind {
                     RangeEnd::Included(RangeSyntax::DotDotDot) => self.word("..."),
                     RangeEnd::Included(RangeSyntax::DotDotEq) => self.word("..="),
                     RangeEnd::Excluded => self.word(".."),
@@ -1510,36 +1512,36 @@ impl<'a> State<'a> {
                     self.print_expr(e);
                 }
             }
-            PatKind::Slice(ref elts) => {
+            PatKind::Slice(elts) => {
                 self.word("[");
-                self.commasep(Inconsistent, &elts, |s, p| s.print_pat(p));
+                self.commasep(Inconsistent, elts, |s, p| s.print_pat(p));
                 self.word("]");
             }
             PatKind::Rest => self.word(".."),
-            PatKind::Paren(ref inner) => {
+            PatKind::Paren(inner) => {
                 self.popen();
                 self.print_pat(inner);
                 self.pclose();
             }
-            PatKind::MacCall(ref m) => self.print_mac(m),
+            PatKind::MacCall(m) => self.print_mac(m),
         }
         self.ann.post(self, AnnNode::Pat(pat))
     }
 
     fn print_explicit_self(&mut self, explicit_self: &ast::ExplicitSelf) {
-        match explicit_self.node {
+        match &explicit_self.node {
             SelfKind::Value(m) => {
-                self.print_mutability(m, false);
+                self.print_mutability(*m, false);
                 self.word("self")
             }
-            SelfKind::Region(ref lt, m) => {
+            SelfKind::Region(lt, m) => {
                 self.word("&");
                 self.print_opt_lifetime(lt);
-                self.print_mutability(m, false);
+                self.print_mutability(*m, false);
                 self.word("self")
             }
-            SelfKind::Explicit(ref typ, m) => {
-                self.print_mutability(m, false);
+            SelfKind::Explicit(typ, m) => {
+                self.print_mutability(*m, false);
                 self.word("self");
                 self.word_space(":");
                 self.print_type(typ)
@@ -1598,10 +1600,10 @@ impl<'a> State<'a> {
 
         self.word("<");
 
-        self.commasep(Inconsistent, &generic_params, |s, param| {
+        self.commasep(Inconsistent, generic_params, |s, param| {
             s.print_outer_attributes_inline(&param.attrs);
 
-            match param.kind {
+            match &param.kind {
                 ast::GenericParamKind::Lifetime => {
                     let lt = ast::Lifetime { id: param.id, ident: param.ident };
                     s.print_lifetime(lt);
@@ -1610,19 +1612,19 @@ impl<'a> State<'a> {
                         s.print_lifetime_bounds(&param.bounds)
                     }
                 }
-                ast::GenericParamKind::Type { ref default } => {
+                ast::GenericParamKind::Type { default } => {
                     s.print_ident(param.ident);
                     if !param.bounds.is_empty() {
                         s.word_nbsp(":");
                         s.print_type_bounds(&param.bounds);
                     }
-                    if let Some(ref default) = default {
+                    if let Some(default) = default {
                         s.space();
                         s.word_space("=");
                         s.print_type(default)
                     }
                 }
-                ast::GenericParamKind::Const { ref ty, kw_span: _, ref default } => {
+                ast::GenericParamKind::Const { ty, default, .. } => {
                     s.word_space("const");
                     s.print_ident(param.ident);
                     s.space();
@@ -1632,7 +1634,7 @@ impl<'a> State<'a> {
                         s.word_nbsp(":");
                         s.print_type_bounds(&param.bounds);
                     }
-                    if let Some(ref default) = default {
+                    if let Some(default) = default {
                         s.space();
                         s.word_space("=");
                         s.print_expr(&default.value);
@@ -1714,9 +1716,9 @@ impl<'a> State<'a> {
             where_clause: ast::WhereClause {
                 has_where_token: false,
                 predicates: Vec::new(),
-                span: rustc_span::DUMMY_SP,
+                span: DUMMY_SP,
             },
-            span: rustc_span::DUMMY_SP,
+            span: DUMMY_SP,
         };
         let header = ast::FnHeader { unsafety, ext, ..ast::FnHeader::default() };
         self.print_fn(decl, header, name, &generics);
@@ -1735,7 +1737,7 @@ impl<'a> State<'a> {
             }
             ast::Extern::Explicit(abi, _) => {
                 self.word_nbsp("extern");
-                self.print_literal(&abi.as_lit());
+                self.print_token_literal(abi.as_token_lit(), abi.span);
                 self.nbsp();
             }
         }
diff --git a/compiler/rustc_ast_pretty/src/pprust/state/expr.rs b/compiler/rustc_ast_pretty/src/pprust/state/expr.rs
index bcefa8ce0..4ed16e337 100644
--- a/compiler/rustc_ast_pretty/src/pprust/state/expr.rs
+++ b/compiler/rustc_ast_pretty/src/pprust/state/expr.rs
@@ -8,9 +8,9 @@ use rustc_ast::{self as ast, BlockCheckMode};
 impl<'a> State<'a> {
     fn print_else(&mut self, els: Option<&ast::Expr>) {
         if let Some(_else) = els {
-            match _else.kind {
+            match &_else.kind {
                 // Another `else if` block.
-                ast::ExprKind::If(ref i, ref then, ref e) => {
+                ast::ExprKind::If(i, then, e) => {
                     self.cbox(INDENT_UNIT - 1);
                     self.ibox(0);
                     self.word(" else if ");
@@ -20,7 +20,7 @@ impl<'a> State<'a> {
                     self.print_else(e.as_deref())
                 }
                 // Final `else` block.
-                ast::ExprKind::Block(ref b, _) => {
+                ast::ExprKind::Block(b, _) => {
                     self.cbox(INDENT_UNIT - 1);
                     self.ibox(0);
                     self.word(" else ");
@@ -58,10 +58,10 @@ impl<'a> State<'a> {
         self.print_expr_cond_paren(expr, Self::cond_needs_par(expr))
     }
 
-    // Does `expr` need parentheses when printed in a condition position?
-    //
-    // These cases need parens due to the parse error observed in #26461: `if return {}`
-    // parses as the erroneous construct `if (return {})`, not `if (return) {}`.
+    /// Does `expr` need parentheses when printed in a condition position?
+    ///
+    /// These cases need parens due to the parse error observed in #26461: `if return {}`
+    /// parses as the erroneous construct `if (return {})`, not `if (return) {}`.
     pub(super) fn cond_needs_par(expr: &ast::Expr) -> bool {
         match expr.kind {
             ast::ExprKind::Break(..)
@@ -121,7 +121,7 @@ impl<'a> State<'a> {
 
     fn print_expr_struct(
         &mut self,
-        qself: &Option<ast::QSelf>,
+        qself: &Option<P<ast::QSelf>>,
         path: &ast::Path,
         fields: &[ast::ExprField],
         rest: &ast::StructRest,
@@ -202,7 +202,7 @@ impl<'a> State<'a> {
         self.print_expr_maybe_paren(receiver, parser::PREC_POSTFIX);
         self.word(".");
         self.print_ident(segment.ident);
-        if let Some(ref args) = segment.args {
+        if let Some(args) = &segment.args {
             self.print_generic_args(args, true);
         }
         self.print_call_post(base_args)
@@ -284,64 +284,66 @@ impl<'a> State<'a> {
 
         self.ibox(INDENT_UNIT);
         self.ann.pre(self, AnnNode::Expr(expr));
-        match expr.kind {
-            ast::ExprKind::Box(ref expr) => {
+        match &expr.kind {
+            ast::ExprKind::Box(expr) => {
                 self.word_space("box");
                 self.print_expr_maybe_paren(expr, parser::PREC_PREFIX);
             }
-            ast::ExprKind::Array(ref exprs) => {
+            ast::ExprKind::Array(exprs) => {
                 self.print_expr_vec(exprs);
             }
-            ast::ExprKind::ConstBlock(ref anon_const) => {
+            ast::ExprKind::ConstBlock(anon_const) => {
                 self.print_expr_anon_const(anon_const, attrs);
             }
-            ast::ExprKind::Repeat(ref element, ref count) => {
+            ast::ExprKind::Repeat(element, count) => {
                 self.print_expr_repeat(element, count);
             }
-            ast::ExprKind::Struct(ref se) => {
+            ast::ExprKind::Struct(se) => {
                 self.print_expr_struct(&se.qself, &se.path, &se.fields, &se.rest);
             }
-            ast::ExprKind::Tup(ref exprs) => {
+            ast::ExprKind::Tup(exprs) => {
                 self.print_expr_tup(exprs);
             }
-            ast::ExprKind::Call(ref func, ref args) => {
-                self.print_expr_call(func, &args);
+            ast::ExprKind::Call(func, args) => {
+                self.print_expr_call(func, args);
+            }
+            ast::ExprKind::MethodCall(box ast::MethodCall { seg, receiver, args, .. }) => {
+                self.print_expr_method_call(seg, receiver, args);
             }
-            ast::ExprKind::MethodCall(ref segment, ref receiver, ref args, _) => {
-                self.print_expr_method_call(segment, &receiver, &args);
+            ast::ExprKind::Binary(op, lhs, rhs) => {
+                self.print_expr_binary(*op, lhs, rhs);
             }
-            ast::ExprKind::Binary(op, ref lhs, ref rhs) => {
-                self.print_expr_binary(op, lhs, rhs);
+            ast::ExprKind::Unary(op, expr) => {
+                self.print_expr_unary(*op, expr);
             }
-            ast::ExprKind::Unary(op, ref expr) => {
-                self.print_expr_unary(op, expr);
+            ast::ExprKind::AddrOf(k, m, expr) => {
+                self.print_expr_addr_of(*k, *m, expr);
             }
-            ast::ExprKind::AddrOf(k, m, ref expr) => {
-                self.print_expr_addr_of(k, m, expr);
+            ast::ExprKind::Lit(token_lit) => {
+                self.print_token_literal(*token_lit, expr.span);
             }
-            ast::ExprKind::Lit(ref lit) => {
-                self.print_literal(lit);
+            ast::ExprKind::IncludedBytes(bytes) => {
+                let lit = ast::LitKind::ByteStr(bytes.clone()).to_token_lit();
+                self.print_token_literal(lit, expr.span)
             }
-            ast::ExprKind::Cast(ref expr, ref ty) => {
+            ast::ExprKind::Cast(expr, ty) => {
                 let prec = AssocOp::As.precedence() as i8;
                 self.print_expr_maybe_paren(expr, prec);
                 self.space();
                 self.word_space("as");
                 self.print_type(ty);
             }
-            ast::ExprKind::Type(ref expr, ref ty) => {
+            ast::ExprKind::Type(expr, ty) => {
                 let prec = AssocOp::Colon.precedence() as i8;
                 self.print_expr_maybe_paren(expr, prec);
                 self.word_space(":");
                 self.print_type(ty);
             }
-            ast::ExprKind::Let(ref pat, ref scrutinee, _) => {
+            ast::ExprKind::Let(pat, scrutinee, _) => {
                 self.print_let(pat, scrutinee);
             }
-            ast::ExprKind::If(ref test, ref blk, ref elseopt) => {
-                self.print_if(test, blk, elseopt.as_deref())
-            }
-            ast::ExprKind::While(ref test, ref blk, opt_label) => {
+            ast::ExprKind::If(test, blk, elseopt) => self.print_if(test, blk, elseopt.as_deref()),
+            ast::ExprKind::While(test, blk, opt_label) => {
                 if let Some(label) = opt_label {
                     self.print_ident(label.ident);
                     self.word_space(":");
@@ -353,7 +355,7 @@ impl<'a> State<'a> {
                 self.space();
                 self.print_block_with_attrs(blk, attrs);
             }
-            ast::ExprKind::ForLoop(ref pat, ref iter, ref blk, opt_label) => {
+            ast::ExprKind::ForLoop(pat, iter, blk, opt_label) => {
                 if let Some(label) = opt_label {
                     self.print_ident(label.ident);
                     self.word_space(":");
@@ -368,7 +370,7 @@ impl<'a> State<'a> {
                 self.space();
                 self.print_block_with_attrs(blk, attrs);
             }
-            ast::ExprKind::Loop(ref blk, opt_label) => {
+            ast::ExprKind::Loop(blk, opt_label, _) => {
                 if let Some(label) = opt_label {
                     self.print_ident(label.ident);
                     self.word_space(":");
@@ -378,7 +380,7 @@ impl<'a> State<'a> {
                 self.word_nbsp("loop");
                 self.print_block_with_attrs(blk, attrs);
             }
-            ast::ExprKind::Match(ref expr, ref arms) => {
+            ast::ExprKind::Match(expr, arms) => {
                 self.cbox(0);
                 self.ibox(0);
                 self.word_nbsp("match");
@@ -392,21 +394,22 @@ impl<'a> State<'a> {
                 let empty = attrs.is_empty() && arms.is_empty();
                 self.bclose(expr.span, empty);
             }
-            ast::ExprKind::Closure(
-                ref binder,
+            ast::ExprKind::Closure(box ast::Closure {
+                binder,
                 capture_clause,
                 asyncness,
                 movability,
-                ref decl,
-                ref body,
-                _,
-            ) => {
+                fn_decl,
+                body,
+                fn_decl_span: _,
+                fn_arg_span: _,
+            }) => {
                 self.print_closure_binder(binder);
-                self.print_movability(movability);
-                self.print_asyncness(asyncness);
-                self.print_capture_clause(capture_clause);
+                self.print_movability(*movability);
+                self.print_asyncness(*asyncness);
+                self.print_capture_clause(*capture_clause);
 
-                self.print_fn_params_and_ret(decl, true);
+                self.print_fn_params_and_ret(fn_decl, true);
                 self.space();
                 self.print_expr(body);
                 self.end(); // need to close a box
@@ -416,7 +419,7 @@ impl<'a> State<'a> {
                 // empty box to satisfy the close.
                 self.ibox(0);
             }
-            ast::ExprKind::Block(ref blk, opt_label) => {
+            ast::ExprKind::Block(blk, opt_label) => {
                 if let Some(label) = opt_label {
                     self.print_ident(label.ident);
                     self.word_space(":");
@@ -427,26 +430,26 @@ impl<'a> State<'a> {
                 self.ibox(0);
                 self.print_block_with_attrs(blk, attrs);
             }
-            ast::ExprKind::Async(capture_clause, _, ref blk) => {
+            ast::ExprKind::Async(capture_clause, _, blk) => {
                 self.word_nbsp("async");
-                self.print_capture_clause(capture_clause);
+                self.print_capture_clause(*capture_clause);
                 // cbox/ibox in analogy to the `ExprKind::Block` arm above
                 self.cbox(0);
                 self.ibox(0);
                 self.print_block_with_attrs(blk, attrs);
             }
-            ast::ExprKind::Await(ref expr) => {
+            ast::ExprKind::Await(expr) => {
                 self.print_expr_maybe_paren(expr, parser::PREC_POSTFIX);
                 self.word(".await");
             }
-            ast::ExprKind::Assign(ref lhs, ref rhs, _) => {
+            ast::ExprKind::Assign(lhs, rhs, _) => {
                 let prec = AssocOp::Assign.precedence() as i8;
                 self.print_expr_maybe_paren(lhs, prec + 1);
                 self.space();
                 self.word_space("=");
                 self.print_expr_maybe_paren(rhs, prec);
             }
-            ast::ExprKind::AssignOp(op, ref lhs, ref rhs) => {
+            ast::ExprKind::AssignOp(op, lhs, rhs) => {
                 let prec = AssocOp::Assign.precedence() as i8;
                 self.print_expr_maybe_paren(lhs, prec + 1);
                 self.space();
@@ -454,45 +457,44 @@ impl<'a> State<'a> {
                 self.word_space("=");
                 self.print_expr_maybe_paren(rhs, prec);
             }
-            ast::ExprKind::Field(ref expr, ident) => {
+            ast::ExprKind::Field(expr, ident) => {
                 self.print_expr_maybe_paren(expr, parser::PREC_POSTFIX);
                 self.word(".");
-                self.print_ident(ident);
+                self.print_ident(*ident);
             }
-            ast::ExprKind::Index(ref expr, ref index) => {
+            ast::ExprKind::Index(expr, index) => {
                 self.print_expr_maybe_paren(expr, parser::PREC_POSTFIX);
                 self.word("[");
                 self.print_expr(index);
                 self.word("]");
             }
-            ast::ExprKind::Range(ref start, ref end, limits) => {
+            ast::ExprKind::Range(start, end, limits) => {
                 // Special case for `Range`.  `AssocOp` claims that `Range` has higher precedence
                 // than `Assign`, but `x .. x = x` gives a parse error instead of `x .. (x = x)`.
                 // Here we use a fake precedence value so that any child with lower precedence than
                 // a "normal" binop gets parenthesized.  (`LOr` is the lowest-precedence binop.)
                 let fake_prec = AssocOp::LOr.precedence() as i8;
-                if let Some(ref e) = *start {
+                if let Some(e) = start {
                     self.print_expr_maybe_paren(e, fake_prec);
                 }
-                if limits == ast::RangeLimits::HalfOpen {
-                    self.word("..");
-                } else {
-                    self.word("..=");
+                match limits {
+                    ast::RangeLimits::HalfOpen => self.word(".."),
+                    ast::RangeLimits::Closed => self.word("..="),
                 }
-                if let Some(ref e) = *end {
+                if let Some(e) = end {
                     self.print_expr_maybe_paren(e, fake_prec);
                 }
             }
             ast::ExprKind::Underscore => self.word("_"),
-            ast::ExprKind::Path(None, ref path) => self.print_path(path, true, 0),
-            ast::ExprKind::Path(Some(ref qself), ref path) => self.print_qpath(path, qself, true),
-            ast::ExprKind::Break(opt_label, ref opt_expr) => {
+            ast::ExprKind::Path(None, path) => self.print_path(path, true, 0),
+            ast::ExprKind::Path(Some(qself), path) => self.print_qpath(path, qself, true),
+            ast::ExprKind::Break(opt_label, opt_expr) => {
                 self.word("break");
                 if let Some(label) = opt_label {
                     self.space();
                     self.print_ident(label.ident);
                 }
-                if let Some(ref expr) = *opt_expr {
+                if let Some(expr) = opt_expr {
                     self.space();
                     self.print_expr_maybe_paren(expr, parser::PREC_JUMP);
                 }
@@ -504,45 +506,45 @@ impl<'a> State<'a> {
                     self.print_ident(label.ident);
                 }
             }
-            ast::ExprKind::Ret(ref result) => {
+            ast::ExprKind::Ret(result) => {
                 self.word("return");
-                if let Some(ref expr) = *result {
+                if let Some(expr) = result {
                     self.word(" ");
                     self.print_expr_maybe_paren(expr, parser::PREC_JUMP);
                 }
             }
-            ast::ExprKind::Yeet(ref result) => {
+            ast::ExprKind::Yeet(result) => {
                 self.word("do");
                 self.word(" ");
                 self.word("yeet");
-                if let Some(ref expr) = *result {
+                if let Some(expr) = result {
                     self.word(" ");
                     self.print_expr_maybe_paren(expr, parser::PREC_JUMP);
                 }
             }
-            ast::ExprKind::InlineAsm(ref a) => {
+            ast::ExprKind::InlineAsm(a) => {
                 self.word("asm!");
                 self.print_inline_asm(a);
             }
-            ast::ExprKind::MacCall(ref m) => self.print_mac(m),
-            ast::ExprKind::Paren(ref e) => {
+            ast::ExprKind::MacCall(m) => self.print_mac(m),
+            ast::ExprKind::Paren(e) => {
                 self.popen();
                 self.print_expr(e);
                 self.pclose();
             }
-            ast::ExprKind::Yield(ref e) => {
+            ast::ExprKind::Yield(e) => {
                 self.word("yield");
 
-                if let Some(ref expr) = *e {
+                if let Some(expr) = e {
                     self.space();
                     self.print_expr_maybe_paren(expr, parser::PREC_JUMP);
                 }
             }
-            ast::ExprKind::Try(ref e) => {
+            ast::ExprKind::Try(e) => {
                 self.print_expr_maybe_paren(e, parser::PREC_POSTFIX);
                 self.word("?")
             }
-            ast::ExprKind::TryBlock(ref blk) => {
+            ast::ExprKind::TryBlock(blk) => {
                 self.cbox(0);
                 self.ibox(0);
                 self.word_nbsp("try");
@@ -569,15 +571,15 @@ impl<'a> State<'a> {
         self.print_outer_attributes(&arm.attrs);
         self.print_pat(&arm.pat);
         self.space();
-        if let Some(ref e) = arm.guard {
+        if let Some(e) = &arm.guard {
             self.word_space("if");
             self.print_expr(e);
             self.space();
         }
         self.word_space("=>");
 
-        match arm.body.kind {
-            ast::ExprKind::Block(ref blk, opt_label) => {
+        match &arm.body.kind {
+            ast::ExprKind::Block(blk, opt_label) => {
                 if let Some(label) = opt_label {
                     self.print_ident(label.ident);
                     self.word_space(":");
@@ -604,7 +606,7 @@ impl<'a> State<'a> {
         match binder {
             ast::ClosureBinder::NotPresent => {}
             ast::ClosureBinder::For { generic_params, .. } => {
-                self.print_formal_generic_params(&generic_params)
+                self.print_formal_generic_params(generic_params)
             }
         }
     }
diff --git a/compiler/rustc_ast_pretty/src/pprust/state/item.rs b/compiler/rustc_ast_pretty/src/pprust/state/item.rs
index 159853c9e..5b6a07721 100644
--- a/compiler/rustc_ast_pretty/src/pprust/state/item.rs
+++ b/compiler/rustc_ast_pretty/src/pprust/state/item.rs
@@ -136,10 +136,10 @@ impl<'a> State<'a> {
         self.maybe_print_comment(item.span.lo());
         self.print_outer_attributes(&item.attrs);
         self.ann.pre(self, AnnNode::Item(item));
-        match item.kind {
+        match &item.kind {
             ast::ItemKind::ExternCrate(orig_name) => {
                 self.head(visibility_qualified(&item.vis, "extern crate"));
-                if let Some(orig_name) = orig_name {
+                if let &Some(orig_name) = orig_name {
                     self.print_name(orig_name);
                     self.space();
                     self.word("as");
@@ -150,35 +150,41 @@ impl<'a> State<'a> {
                 self.end(); // end inner head-block
                 self.end(); // end outer head-block
             }
-            ast::ItemKind::Use(ref tree) => {
+            ast::ItemKind::Use(tree) => {
                 self.print_visibility(&item.vis);
                 self.word_nbsp("use");
                 self.print_use_tree(tree);
                 self.word(";");
             }
-            ast::ItemKind::Static(ref ty, mutbl, ref body) => {
+            ast::ItemKind::Static(ty, mutbl, body) => {
                 let def = ast::Defaultness::Final;
-                self.print_item_const(item.ident, Some(mutbl), ty, body.as_deref(), &item.vis, def);
+                self.print_item_const(
+                    item.ident,
+                    Some(*mutbl),
+                    ty,
+                    body.as_deref(),
+                    &item.vis,
+                    def,
+                );
             }
-            ast::ItemKind::Const(def, ref ty, ref body) => {
-                self.print_item_const(item.ident, None, ty, body.as_deref(), &item.vis, def);
+            ast::ItemKind::Const(def, ty, body) => {
+                self.print_item_const(item.ident, None, ty, body.as_deref(), &item.vis, *def);
             }
-            ast::ItemKind::Fn(box ast::Fn { defaultness, ref sig, ref generics, ref body }) => {
-                let body = body.as_deref();
+            ast::ItemKind::Fn(box ast::Fn { defaultness, sig, generics, body }) => {
                 self.print_fn_full(
                     sig,
                     item.ident,
                     generics,
                     &item.vis,
-                    defaultness,
-                    body,
+                    *defaultness,
+                    body.as_deref(),
                     &item.attrs,
                 );
             }
-            ast::ItemKind::Mod(unsafety, ref mod_kind) => {
+            ast::ItemKind::Mod(unsafety, mod_kind) => {
                 self.head(Self::to_string(|s| {
                     s.print_visibility(&item.vis);
-                    s.print_unsafety(unsafety);
+                    s.print_unsafety(*unsafety);
                     s.word("mod");
                 }));
                 self.print_ident(item.ident);
@@ -201,13 +207,13 @@ impl<'a> State<'a> {
                     }
                 }
             }
-            ast::ItemKind::ForeignMod(ref nmod) => {
+            ast::ItemKind::ForeignMod(nmod) => {
                 self.head(Self::to_string(|s| {
                     s.print_unsafety(nmod.unsafety);
                     s.word("extern");
                 }));
                 if let Some(abi) = nmod.abi {
-                    self.print_literal(&abi.as_lit());
+                    self.print_token_literal(abi.as_token_lit(), abi.span);
                     self.nbsp();
                 }
                 self.bopen();
@@ -215,7 +221,7 @@ impl<'a> State<'a> {
                 let empty = item.attrs.is_empty() && nmod.items.is_empty();
                 self.bclose(item.span, empty);
             }
-            ast::ItemKind::GlobalAsm(ref asm) => {
+            ast::ItemKind::GlobalAsm(asm) => {
                 self.head(visibility_qualified(&item.vis, "global_asm!"));
                 self.print_inline_asm(asm);
                 self.word(";");
@@ -224,32 +230,31 @@ impl<'a> State<'a> {
             }
             ast::ItemKind::TyAlias(box ast::TyAlias {
                 defaultness,
-                ref generics,
+                generics,
                 where_clauses,
                 where_predicates_split,
-                ref bounds,
-                ref ty,
+                bounds,
+                ty,
             }) => {
-                let ty = ty.as_deref();
                 self.print_associated_type(
                     item.ident,
                     generics,
-                    where_clauses,
-                    where_predicates_split,
+                    *where_clauses,
+                    *where_predicates_split,
                     bounds,
-                    ty,
+                    ty.as_deref(),
                     &item.vis,
-                    defaultness,
+                    *defaultness,
                 );
             }
-            ast::ItemKind::Enum(ref enum_definition, ref params) => {
+            ast::ItemKind::Enum(enum_definition, params) => {
                 self.print_enum_def(enum_definition, params, item.ident, item.span, &item.vis);
             }
-            ast::ItemKind::Struct(ref struct_def, ref generics) => {
+            ast::ItemKind::Struct(struct_def, generics) => {
                 self.head(visibility_qualified(&item.vis, "struct"));
                 self.print_struct(struct_def, generics, item.ident, item.span, true);
             }
-            ast::ItemKind::Union(ref struct_def, ref generics) => {
+            ast::ItemKind::Union(struct_def, generics) => {
                 self.head(visibility_qualified(&item.vis, "union"));
                 self.print_struct(struct_def, generics, item.ident, item.span, true);
             }
@@ -258,15 +263,15 @@ impl<'a> State<'a> {
                 polarity,
                 defaultness,
                 constness,
-                ref generics,
-                ref of_trait,
-                ref self_ty,
-                ref items,
+                generics,
+                of_trait,
+                self_ty,
+                items,
             }) => {
                 self.head("");
                 self.print_visibility(&item.vis);
-                self.print_defaultness(defaultness);
-                self.print_unsafety(unsafety);
+                self.print_defaultness(*defaultness);
+                self.print_unsafety(*unsafety);
                 self.word("impl");
 
                 if generics.params.is_empty() {
@@ -276,13 +281,13 @@ impl<'a> State<'a> {
                     self.space();
                 }
 
-                self.print_constness(constness);
+                self.print_constness(*constness);
 
                 if let ast::ImplPolarity::Negative(_) = polarity {
                     self.word("!");
                 }
 
-                if let Some(ref t) = *of_trait {
+                if let Some(t) = of_trait {
                     self.print_trait_ref(t);
                     self.space();
                     self.word_space("for");
@@ -303,21 +308,21 @@ impl<'a> State<'a> {
             ast::ItemKind::Trait(box ast::Trait {
                 is_auto,
                 unsafety,
-                ref generics,
-                ref bounds,
-                ref items,
+                generics,
+                bounds,
+                items,
                 ..
             }) => {
                 self.head("");
                 self.print_visibility(&item.vis);
-                self.print_unsafety(unsafety);
-                self.print_is_auto(is_auto);
+                self.print_unsafety(*unsafety);
+                self.print_is_auto(*is_auto);
                 self.word_nbsp("trait");
                 self.print_ident(item.ident);
                 self.print_generic_params(&generics.params);
                 let mut real_bounds = Vec::with_capacity(bounds.len());
                 for b in bounds.iter() {
-                    if let GenericBound::Trait(ref ptr, ast::TraitBoundModifier::Maybe) = *b {
+                    if let GenericBound::Trait(ptr, ast::TraitBoundModifier::Maybe) = b {
                         self.space();
                         self.word_space("for ?");
                         self.print_trait_ref(&ptr.trait_ref);
@@ -339,38 +344,27 @@ impl<'a> State<'a> {
                 let empty = item.attrs.is_empty() && items.is_empty();
                 self.bclose(item.span, empty);
             }
-            ast::ItemKind::TraitAlias(ref generics, ref bounds) => {
+            ast::ItemKind::TraitAlias(generics, bounds) => {
                 self.head(visibility_qualified(&item.vis, "trait"));
                 self.print_ident(item.ident);
                 self.print_generic_params(&generics.params);
-                let mut real_bounds = Vec::with_capacity(bounds.len());
-                // FIXME(durka) this seems to be some quite outdated syntax
-                for b in bounds.iter() {
-                    if let GenericBound::Trait(ref ptr, ast::TraitBoundModifier::Maybe) = *b {
-                        self.space();
-                        self.word_space("for ?");
-                        self.print_trait_ref(&ptr.trait_ref);
-                    } else {
-                        real_bounds.push(b.clone());
-                    }
-                }
                 self.nbsp();
-                if !real_bounds.is_empty() {
+                if !bounds.is_empty() {
                     self.word_nbsp("=");
-                    self.print_type_bounds(&real_bounds);
+                    self.print_type_bounds(&bounds);
                 }
                 self.print_where_clause(&generics.where_clause);
                 self.word(";");
                 self.end(); // end inner head-block
                 self.end(); // end outer head-block
             }
-            ast::ItemKind::MacCall(ref mac) => {
+            ast::ItemKind::MacCall(mac) => {
                 self.print_mac(mac);
                 if mac.args.need_semicolon() {
                     self.word(";");
                 }
             }
-            ast::ItemKind::MacroDef(ref macro_def) => {
+            ast::ItemKind::MacroDef(macro_def) => {
                 self.print_mac_def(macro_def, &item.ident, item.span, |state| {
                     state.print_visibility(&item.vis)
                 });
@@ -412,11 +406,11 @@ impl<'a> State<'a> {
     }
 
     pub(crate) fn print_visibility(&mut self, vis: &ast::Visibility) {
-        match vis.kind {
+        match &vis.kind {
             ast::VisibilityKind::Public => self.word_nbsp("pub"),
-            ast::VisibilityKind::Restricted { ref path, id: _, shorthand } => {
+            ast::VisibilityKind::Restricted { path, shorthand, .. } => {
                 let path = Self::to_string(|s| s.print_path(path, false, 0));
-                if shorthand && (path == "crate" || path == "self" || path == "super") {
+                if *shorthand && (path == "crate" || path == "self" || path == "super") {
                     self.word_nbsp(format!("pub({})", path))
                 } else {
                     self.word_nbsp(format!("pub(in {})", path))
@@ -465,7 +459,7 @@ impl<'a> State<'a> {
     ) {
         self.print_ident(ident);
         self.print_generic_params(&generics.params);
-        match struct_def {
+        match &struct_def {
             ast::VariantData::Tuple(..) | ast::VariantData::Unit(..) => {
                 if let ast::VariantData::Tuple(..) = struct_def {
                     self.popen();
@@ -484,7 +478,7 @@ impl<'a> State<'a> {
                 self.end();
                 self.end(); // Close the outer-box.
             }
-            ast::VariantData::Struct(ref fields, ..) => {
+            ast::VariantData::Struct(fields, ..) => {
                 self.print_where_clause(&generics.where_clause);
                 self.print_record_struct_body(fields, span);
             }
@@ -496,7 +490,7 @@ impl<'a> State<'a> {
         self.print_visibility(&v.vis);
         let generics = ast::Generics::default();
         self.print_struct(&v.data, &generics, v.ident, v.span, false);
-        if let Some(ref d) = v.disr_expr {
+        if let Some(d) = &v.disr_expr {
             self.space();
             self.word_space("=");
             self.print_expr(&d.value)
@@ -657,10 +651,10 @@ impl<'a> State<'a> {
     }
 
     fn print_use_tree(&mut self, tree: &ast::UseTree) {
-        match tree.kind {
-            ast::UseTreeKind::Simple(rename, ..) => {
+        match &tree.kind {
+            ast::UseTreeKind::Simple(rename) => {
                 self.print_path(&tree.prefix, false, 0);
-                if let Some(rename) = rename {
+                if let &Some(rename) = rename {
                     self.nbsp();
                     self.word_nbsp("as");
                     self.print_ident(rename);
@@ -673,7 +667,7 @@ impl<'a> State<'a> {
                 }
                 self.word("*");
             }
-            ast::UseTreeKind::Nested(ref items) => {
+            ast::UseTreeKind::Nested(items) => {
                 if !tree.prefix.segments.is_empty() {
                     self.print_path(&tree.prefix, false, 0);
                     self.word("::");