From 5e20a29b4fdc8a2d442d1093681b396dcb4b816b Mon Sep 17 00:00:00 2001
From: Robin Krahl <robin.krahl@ireas.org>
Date: Tue, 7 Jan 2020 11:18:04 +0000
Subject: Add structopt dependency in version 0.3.7

This patch series replaces argparse with structopt in the argument
handling code. As a first step, we need structopt as a dependency.

Import subrepo structopt/:structopt at efbdda4753592e27bc430fb01f7b9650b2f3174d
Import subrepo bitflags/:bitflags at 30668016aca6bd3b02c766e8347e0b4080d4c296
Import subrepo clap/:clap at 784524f7eb193e35f81082cc69454c8c21b948f7
Import subrepo heck/:heck at 093d56fbf001e1506e56dbfa38631d99b1066df1
Import subrepo proc-macro-error/:proc-macro-error at 6c4cfe79a622c5de8ae68557993542be46eacae2
Import subrepo proc-macro2/:proc-macro2 at d5d48eddca4566e5438e8a2cbed4a74e049544de
Import subrepo quote/:quote at 727436c6c137b20f0f34dde5d8fda2679b9747ad
Import subrepo rustversion/:rustversion at 0c5663313516263059ce9059ef81fc7a1cf655ca
Import subrepo syn-mid/:syn-mid at 5d3d85414a9e6674e1857ec22a87b96e04a6851a
Import subrepo syn/:syn at e87c27e87f6f4ef8919d0372bdb056d53ef0d8f3
Import subrepo textwrap/:textwrap at abcd618beae3f74841032aa5b53c1086b0a57ca2
Import subrepo unicode-segmentation/:unicode-segmentation at 637c9874c4fe0c205ff27787faf150a40295c6c3
Import subrepo unicode-width/:unicode-width at 3033826f8bf05e82724140a981d5941e48fce393
Import subrepo unicode-xid/:unicode-xid at 4baae9fffb156ba229665b972a9cd5991787ceb7
---
 syn/src/expr.rs | 3236 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 3236 insertions(+)
 create mode 100644 syn/src/expr.rs

(limited to 'syn/src/expr.rs')

diff --git a/syn/src/expr.rs b/syn/src/expr.rs
new file mode 100644
index 0000000..603dc32
--- /dev/null
+++ b/syn/src/expr.rs
@@ -0,0 +1,3236 @@
+use super::*;
+use crate::punctuated::Punctuated;
+#[cfg(feature = "extra-traits")]
+use crate::tt::TokenStreamHelper;
+use proc_macro2::{Span, TokenStream};
+#[cfg(feature = "printing")]
+use quote::IdentFragment;
+#[cfg(feature = "printing")]
+use std::fmt::{self, Display};
+use std::hash::{Hash, Hasher};
+#[cfg(all(feature = "parsing", feature = "full"))]
+use std::mem;
+
+ast_enum_of_structs! {
+    /// A Rust expression.
+    ///
+    /// *This type is available if Syn is built with the `"derive"` or `"full"`
+    /// feature.*
+    ///
+    /// # Syntax tree enums
+    ///
+    /// This type is a syntax tree enum. In Syn this and other syntax tree enums
+    /// are designed to be traversed using the following rebinding idiom.
+    ///
+    /// ```
+    /// # use syn::Expr;
+    /// #
+    /// # fn example(expr: Expr) {
+    /// # const IGNORE: &str = stringify! {
+    /// let expr: Expr = /* ... */;
+    /// # };
+    /// match expr {
+    ///     Expr::MethodCall(expr) => {
+    ///         /* ... */
+    ///     }
+    ///     Expr::Cast(expr) => {
+    ///         /* ... */
+    ///     }
+    ///     Expr::If(expr) => {
+    ///         /* ... */
+    ///     }
+    ///
+    ///     /* ... */
+    ///     # _ => {}
+    /// # }
+    /// # }
+    /// ```
+    ///
+    /// We begin with a variable `expr` of type `Expr` that has no fields
+    /// (because it is an enum), and by matching on it and rebinding a variable
+    /// with the same name `expr` we effectively imbue our variable with all of
+    /// the data fields provided by the variant that it turned out to be. So for
+    /// example above if we ended up in the `MethodCall` case then we get to use
+    /// `expr.receiver`, `expr.args` etc; if we ended up in the `If` case we get
+    /// to use `expr.cond`, `expr.then_branch`, `expr.else_branch`.
+    ///
+    /// This approach avoids repeating the variant names twice on every line.
+    ///
+    /// ```
+    /// # use syn::{Expr, ExprMethodCall};
+    /// #
+    /// # fn example(expr: Expr) {
+    /// // Repetitive; recommend not doing this.
+    /// match expr {
+    ///     Expr::MethodCall(ExprMethodCall { method, args, .. }) => {
+    /// # }
+    /// # _ => {}
+    /// # }
+    /// # }
+    /// ```
+    ///
+    /// In general, the name to which a syntax tree enum variant is bound should
+    /// be a suitable name for the complete syntax tree enum type.
+    ///
+    /// ```
+    /// # use syn::{Expr, ExprField};
+    /// #
+    /// # fn example(discriminant: ExprField) {
+    /// // Binding is called `base` which is the name I would use if I were
+    /// // assigning `*discriminant.base` without an `if let`.
+    /// if let Expr::Tuple(base) = *discriminant.base {
+    /// # }
+    /// # }
+    /// ```
+    ///
+    /// A sign that you may not be choosing the right variable names is if you
+    /// see names getting repeated in your code, like accessing
+    /// `receiver.receiver` or `pat.pat` or `cond.cond`.
+    pub enum Expr #manual_extra_traits {
+        /// A slice literal expression: `[a, b, c, d]`.
+        Array(ExprArray),
+
+        /// An assignment expression: `a = compute()`.
+        Assign(ExprAssign),
+
+        /// A compound assignment expression: `counter += 1`.
+        AssignOp(ExprAssignOp),
+
+        /// An async block: `async { ... }`.
+        Async(ExprAsync),
+
+        /// An await expression: `fut.await`.
+        Await(ExprAwait),
+
+        /// A binary operation: `a + b`, `a * b`.
+        Binary(ExprBinary),
+
+        /// A blocked scope: `{ ... }`.
+        Block(ExprBlock),
+
+        /// A box expression: `box f`.
+        Box(ExprBox),
+
+        /// A `break`, with an optional label to break and an optional
+        /// expression.
+        Break(ExprBreak),
+
+        /// A function call expression: `invoke(a, b)`.
+        Call(ExprCall),
+
+        /// A cast expression: `foo as f64`.
+        Cast(ExprCast),
+
+        /// A closure expression: `|a, b| a + b`.
+        Closure(ExprClosure),
+
+        /// A `continue`, with an optional label.
+        Continue(ExprContinue),
+
+        /// Access of a named struct field (`obj.k`) or unnamed tuple struct
+        /// field (`obj.0`).
+        Field(ExprField),
+
+        /// A for loop: `for pat in expr { ... }`.
+        ForLoop(ExprForLoop),
+
+        /// An expression contained within invisible delimiters.
+        ///
+        /// This variant is important for faithfully representing the precedence
+        /// of expressions and is related to `None`-delimited spans in a
+        /// `TokenStream`.
+        Group(ExprGroup),
+
+        /// An `if` expression with an optional `else` block: `if expr { ... }
+        /// else { ... }`.
+        ///
+        /// The `else` branch expression may only be an `If` or `Block`
+        /// expression, not any of the other types of expression.
+        If(ExprIf),
+
+        /// A square bracketed indexing expression: `vector[2]`.
+        Index(ExprIndex),
+
+        /// A `let` guard: `let Some(x) = opt`.
+        Let(ExprLet),
+
+        /// A literal in place of an expression: `1`, `"foo"`.
+        Lit(ExprLit),
+
+        /// Conditionless loop: `loop { ... }`.
+        Loop(ExprLoop),
+
+        /// A macro invocation expression: `format!("{}", q)`.
+        Macro(ExprMacro),
+
+        /// A `match` expression: `match n { Some(n) => {}, None => {} }`.
+        Match(ExprMatch),
+
+        /// A method call expression: `x.foo::<T>(a, b)`.
+        MethodCall(ExprMethodCall),
+
+        /// A parenthesized expression: `(a + b)`.
+        Paren(ExprParen),
+
+        /// A path like `std::mem::replace` possibly containing generic
+        /// parameters and a qualified self-type.
+        ///
+        /// A plain identifier like `x` is a path of length 1.
+        Path(ExprPath),
+
+        /// A range expression: `1..2`, `1..`, `..2`, `1..=2`, `..=2`.
+        Range(ExprRange),
+
+        /// A referencing operation: `&a` or `&mut a`.
+        Reference(ExprReference),
+
+        /// An array literal constructed from one repeated element: `[0u8; N]`.
+        Repeat(ExprRepeat),
+
+        /// A `return`, with an optional value to be returned.
+        Return(ExprReturn),
+
+        /// A struct literal expression: `Point { x: 1, y: 1 }`.
+        ///
+        /// The `rest` provides the value of the remaining fields as in `S { a:
+        /// 1, b: 1, ..rest }`.
+        Struct(ExprStruct),
+
+        /// A try-expression: `expr?`.
+        Try(ExprTry),
+
+        /// A try block: `try { ... }`.
+        TryBlock(ExprTryBlock),
+
+        /// A tuple expression: `(a, b, c, d)`.
+        Tuple(ExprTuple),
+
+        /// A type ascription expression: `foo: f64`.
+        Type(ExprType),
+
+        /// A unary operation: `!x`, `*x`.
+        Unary(ExprUnary),
+
+        /// An unsafe block: `unsafe { ... }`.
+        Unsafe(ExprUnsafe),
+
+        /// Tokens in expression position not interpreted by Syn.
+        Verbatim(TokenStream),
+
+        /// A while loop: `while expr { ... }`.
+        While(ExprWhile),
+
+        /// A yield expression: `yield expr`.
+        Yield(ExprYield),
+
+        #[doc(hidden)]
+        __Nonexhaustive,
+    }
+}
+
+ast_struct! {
+    /// A slice literal expression: `[a, b, c, d]`.
+    ///
+    /// *This type is available if Syn is built with the `"full"` feature.*
+    pub struct ExprArray #full {
+        pub attrs: Vec<Attribute>,
+        pub bracket_token: token::Bracket,
+        pub elems: Punctuated<Expr, Token![,]>,
+    }
+}
+
+ast_struct! {
+    /// An assignment expression: `a = compute()`.
+    ///
+    /// *This type is available if Syn is built with the `"full"` feature.*
+    pub struct ExprAssign #full {
+        pub attrs: Vec<Attribute>,
+        pub left: Box<Expr>,
+        pub eq_token: Token![=],
+        pub right: Box<Expr>,
+    }
+}
+
+ast_struct! {
+    /// A compound assignment expression: `counter += 1`.
+    ///
+    /// *This type is available if Syn is built with the `"full"` feature.*
+    pub struct ExprAssignOp #full {
+        pub attrs: Vec<Attribute>,
+        pub left: Box<Expr>,
+        pub op: BinOp,
+        pub right: Box<Expr>,
+    }
+}
+
+ast_struct! {
+    /// An async block: `async { ... }`.
+    ///
+    /// *This type is available if Syn is built with the `"full"` feature.*
+    pub struct ExprAsync #full {
+        pub attrs: Vec<Attribute>,
+        pub async_token: Token![async],
+        pub capture: Option<Token![move]>,
+        pub block: Block,
+    }
+}
+
+ast_struct! {
+    /// An await expression: `fut.await`.
+    ///
+    /// *This type is available if Syn is built with the `"full"` feature.*
+    pub struct ExprAwait #full {
+        pub attrs: Vec<Attribute>,
+        pub base: Box<Expr>,
+        pub dot_token: Token![.],
+        pub await_token: token::Await,
+    }
+}
+
+ast_struct! {
+    /// A binary operation: `a + b`, `a * b`.
+    ///
+    /// *This type is available if Syn is built with the `"derive"` or
+    /// `"full"` feature.*
+    pub struct ExprBinary {
+        pub attrs: Vec<Attribute>,
+        pub left: Box<Expr>,
+        pub op: BinOp,
+        pub right: Box<Expr>,
+    }
+}
+
+ast_struct! {
+    /// A blocked scope: `{ ... }`.
+    ///
+    /// *This type is available if Syn is built with the `"full"` feature.*
+    pub struct ExprBlock #full {
+        pub attrs: Vec<Attribute>,
+        pub label: Option<Label>,
+        pub block: Block,
+    }
+}
+
+ast_struct! {
+    /// A box expression: `box f`.
+    ///
+    /// *This type is available if Syn is built with the `"full"` feature.*
+    pub struct ExprBox #full {
+        pub attrs: Vec<Attribute>,
+        pub box_token: Token![box],
+        pub expr: Box<Expr>,
+    }
+}
+
+ast_struct! {
+    /// A `break`, with an optional label to break and an optional
+    /// expression.
+    ///
+    /// *This type is available if Syn is built with the `"full"` feature.*
+    pub struct ExprBreak #full {
+        pub attrs: Vec<Attribute>,
+        pub break_token: Token![break],
+        pub label: Option<Lifetime>,
+        pub expr: Option<Box<Expr>>,
+    }
+}
+
+ast_struct! {
+    /// A function call expression: `invoke(a, b)`.
+    ///
+    /// *This type is available if Syn is built with the `"derive"` or
+    /// `"full"` feature.*
+    pub struct ExprCall {
+        pub attrs: Vec<Attribute>,
+        pub func: Box<Expr>,
+        pub paren_token: token::Paren,
+        pub args: Punctuated<Expr, Token![,]>,
+    }
+}
+
+ast_struct! {
+    /// A cast expression: `foo as f64`.
+    ///
+    /// *This type is available if Syn is built with the `"derive"` or
+    /// `"full"` feature.*
+    pub struct ExprCast {
+        pub attrs: Vec<Attribute>,
+        pub expr: Box<Expr>,
+        pub as_token: Token![as],
+        pub ty: Box<Type>,
+    }
+}
+
+ast_struct! {
+    /// A closure expression: `|a, b| a + b`.
+    ///
+    /// *This type is available if Syn is built with the `"full"` feature.*
+    pub struct ExprClosure #full {
+        pub attrs: Vec<Attribute>,
+        pub asyncness: Option<Token![async]>,
+        pub movability: Option<Token![static]>,
+        pub capture: Option<Token![move]>,
+        pub or1_token: Token![|],
+        pub inputs: Punctuated<Pat, Token![,]>,
+        pub or2_token: Token![|],
+        pub output: ReturnType,
+        pub body: Box<Expr>,
+    }
+}
+
+ast_struct! {
+    /// A `continue`, with an optional label.
+    ///
+    /// *This type is available if Syn is built with the `"full"` feature.*
+    pub struct ExprContinue #full {
+        pub attrs: Vec<Attribute>,
+        pub continue_token: Token![continue],
+        pub label: Option<Lifetime>,
+    }
+}
+
+ast_struct! {
+    /// Access of a named struct field (`obj.k`) or unnamed tuple struct
+    /// field (`obj.0`).
+    ///
+    /// *This type is available if Syn is built with the `"full"` feature.*
+    pub struct ExprField {
+        pub attrs: Vec<Attribute>,
+        pub base: Box<Expr>,
+        pub dot_token: Token![.],
+        pub member: Member,
+    }
+}
+
+ast_struct! {
+    /// A for loop: `for pat in expr { ... }`.
+    ///
+    /// *This type is available if Syn is built with the `"full"` feature.*
+    pub struct ExprForLoop #full {
+        pub attrs: Vec<Attribute>,
+        pub label: Option<Label>,
+        pub for_token: Token![for],
+        pub pat: Pat,
+        pub in_token: Token![in],
+        pub expr: Box<Expr>,
+        pub body: Block,
+    }
+}
+
+ast_struct! {
+    /// An expression contained within invisible delimiters.
+    ///
+    /// This variant is important for faithfully representing the precedence
+    /// of expressions and is related to `None`-delimited spans in a
+    /// `TokenStream`.
+    ///
+    /// *This type is available if Syn is built with the `"full"` feature.*
+    pub struct ExprGroup #full {
+        pub attrs: Vec<Attribute>,
+        pub group_token: token::Group,
+        pub expr: Box<Expr>,
+    }
+}
+
+ast_struct! {
+    /// An `if` expression with an optional `else` block: `if expr { ... }
+    /// else { ... }`.
+    ///
+    /// The `else` branch expression may only be an `If` or `Block`
+    /// expression, not any of the other types of expression.
+    ///
+    /// *This type is available if Syn is built with the `"full"` feature.*
+    pub struct ExprIf #full {
+        pub attrs: Vec<Attribute>,
+        pub if_token: Token![if],
+        pub cond: Box<Expr>,
+        pub then_branch: Block,
+        pub else_branch: Option<(Token![else], Box<Expr>)>,
+    }
+}
+
+ast_struct! {
+    /// A square bracketed indexing expression: `vector[2]`.
+    ///
+    /// *This type is available if Syn is built with the `"derive"` or
+    /// `"full"` feature.*
+    pub struct ExprIndex {
+        pub attrs: Vec<Attribute>,
+        pub expr: Box<Expr>,
+        pub bracket_token: token::Bracket,
+        pub index: Box<Expr>,
+    }
+}
+
+ast_struct! {
+    /// A `let` guard: `let Some(x) = opt`.
+    ///
+    /// *This type is available if Syn is built with the `"full"` feature.*
+    pub struct ExprLet #full {
+        pub attrs: Vec<Attribute>,
+        pub let_token: Token![let],
+        pub pat: Pat,
+        pub eq_token: Token![=],
+        pub expr: Box<Expr>,
+    }
+}
+
+ast_struct! {
+    /// A literal in place of an expression: `1`, `"foo"`.
+    ///
+    /// *This type is available if Syn is built with the `"derive"` or
+    /// `"full"` feature.*
+    pub struct ExprLit {
+        pub attrs: Vec<Attribute>,
+        pub lit: Lit,
+    }
+}
+
+ast_struct! {
+    /// Conditionless loop: `loop { ... }`.
+    ///
+    /// *This type is available if Syn is built with the `"full"` feature.*
+    pub struct ExprLoop #full {
+        pub attrs: Vec<Attribute>,
+        pub label: Option<Label>,
+        pub loop_token: Token![loop],
+        pub body: Block,
+    }
+}
+
+ast_struct! {
+    /// A macro invocation expression: `format!("{}", q)`.
+    ///
+    /// *This type is available if Syn is built with the `"full"` feature.*
+    pub struct ExprMacro #full {
+        pub attrs: Vec<Attribute>,
+        pub mac: Macro,
+    }
+}
+
+ast_struct! {
+    /// A `match` expression: `match n { Some(n) => {}, None => {} }`.
+    ///
+    /// *This type is available if Syn is built with the `"full"` feature.*
+    pub struct ExprMatch #full {
+        pub attrs: Vec<Attribute>,
+        pub match_token: Token![match],
+        pub expr: Box<Expr>,
+        pub brace_token: token::Brace,
+        pub arms: Vec<Arm>,
+    }
+}
+
+ast_struct! {
+    /// A method call expression: `x.foo::<T>(a, b)`.
+    ///
+    /// *This type is available if Syn is built with the `"full"` feature.*
+    pub struct ExprMethodCall #full {
+        pub attrs: Vec<Attribute>,
+        pub receiver: Box<Expr>,
+        pub dot_token: Token![.],
+        pub method: Ident,
+        pub turbofish: Option<MethodTurbofish>,
+        pub paren_token: token::Paren,
+        pub args: Punctuated<Expr, Token![,]>,
+    }
+}
+
+ast_struct! {
+    /// A parenthesized expression: `(a + b)`.
+    ///
+    /// *This type is available if Syn is built with the `"full"` feature.*
+    pub struct ExprParen {
+        pub attrs: Vec<Attribute>,
+        pub paren_token: token::Paren,
+        pub expr: Box<Expr>,
+    }
+}
+
+ast_struct! {
+    /// A path like `std::mem::replace` possibly containing generic
+    /// parameters and a qualified self-type.
+    ///
+    /// A plain identifier like `x` is a path of length 1.
+    ///
+    /// *This type is available if Syn is built with the `"derive"` or
+    /// `"full"` feature.*
+    pub struct ExprPath {
+        pub attrs: Vec<Attribute>,
+        pub qself: Option<QSelf>,
+        pub path: Path,
+    }
+}
+
+ast_struct! {
+    /// A range expression: `1..2`, `1..`, `..2`, `1..=2`, `..=2`.
+    ///
+    /// *This type is available if Syn is built with the `"full"` feature.*
+    pub struct ExprRange #full {
+        pub attrs: Vec<Attribute>,
+        pub from: Option<Box<Expr>>,
+        pub limits: RangeLimits,
+        pub to: Option<Box<Expr>>,
+    }
+}
+
+ast_struct! {
+    /// A referencing operation: `&a` or `&mut a`.
+    ///
+    /// *This type is available if Syn is built with the `"full"` feature.*
+    pub struct ExprReference #full {
+        pub attrs: Vec<Attribute>,
+        pub and_token: Token![&],
+        pub raw: Reserved,
+        pub mutability: Option<Token![mut]>,
+        pub expr: Box<Expr>,
+    }
+}
+
+ast_struct! {
+    /// An array literal constructed from one repeated element: `[0u8; N]`.
+    ///
+    /// *This type is available if Syn is built with the `"full"` feature.*
+    pub struct ExprRepeat #full {
+        pub attrs: Vec<Attribute>,
+        pub bracket_token: token::Bracket,
+        pub expr: Box<Expr>,
+        pub semi_token: Token![;],
+        pub len: Box<Expr>,
+    }
+}
+
+ast_struct! {
+    /// A `return`, with an optional value to be returned.
+    ///
+    /// *This type is available if Syn is built with the `"full"` feature.*
+    pub struct ExprReturn #full {
+        pub attrs: Vec<Attribute>,
+        pub return_token: Token![return],
+        pub expr: Option<Box<Expr>>,
+    }
+}
+
+ast_struct! {
+    /// A struct literal expression: `Point { x: 1, y: 1 }`.
+    ///
+    /// The `rest` provides the value of the remaining fields as in `S { a:
+    /// 1, b: 1, ..rest }`.
+    ///
+    /// *This type is available if Syn is built with the `"full"` feature.*
+    pub struct ExprStruct #full {
+        pub attrs: Vec<Attribute>,
+        pub path: Path,
+        pub brace_token: token::Brace,
+        pub fields: Punctuated<FieldValue, Token![,]>,
+        pub dot2_token: Option<Token![..]>,
+        pub rest: Option<Box<Expr>>,
+    }
+}
+
+ast_struct! {
+    /// A try-expression: `expr?`.
+    ///
+    /// *This type is available if Syn is built with the `"full"` feature.*
+    pub struct ExprTry #full {
+        pub attrs: Vec<Attribute>,
+        pub expr: Box<Expr>,
+        pub question_token: Token![?],
+    }
+}
+
+ast_struct! {
+    /// A try block: `try { ... }`.
+    ///
+    /// *This type is available if Syn is built with the `"full"` feature.*
+    pub struct ExprTryBlock #full {
+        pub attrs: Vec<Attribute>,
+        pub try_token: Token![try],
+        pub block: Block,
+    }
+}
+
+ast_struct! {
+    /// A tuple expression: `(a, b, c, d)`.
+    ///
+    /// *This type is available if Syn is built with the `"full"` feature.*
+    pub struct ExprTuple #full {
+        pub attrs: Vec<Attribute>,
+        pub paren_token: token::Paren,
+        pub elems: Punctuated<Expr, Token![,]>,
+    }
+}
+
+ast_struct! {
+    /// A type ascription expression: `foo: f64`.
+    ///
+    /// *This type is available if Syn is built with the `"full"` feature.*
+    pub struct ExprType #full {
+        pub attrs: Vec<Attribute>,
+        pub expr: Box<Expr>,
+        pub colon_token: Token![:],
+        pub ty: Box<Type>,
+    }
+}
+
+ast_struct! {
+    /// A unary operation: `!x`, `*x`.
+    ///
+    /// *This type is available if Syn is built with the `"derive"` or
+    /// `"full"` feature.*
+    pub struct ExprUnary {
+        pub attrs: Vec<Attribute>,
+        pub op: UnOp,
+        pub expr: Box<Expr>,
+    }
+}
+
+ast_struct! {
+    /// An unsafe block: `unsafe { ... }`.
+    ///
+    /// *This type is available if Syn is built with the `"full"` feature.*
+    pub struct ExprUnsafe #full {
+        pub attrs: Vec<Attribute>,
+        pub unsafe_token: Token![unsafe],
+        pub block: Block,
+    }
+}
+
+ast_struct! {
+    /// A while loop: `while expr { ... }`.
+    ///
+    /// *This type is available if Syn is built with the `"full"` feature.*
+    pub struct ExprWhile #full {
+        pub attrs: Vec<Attribute>,
+        pub label: Option<Label>,
+        pub while_token: Token![while],
+        pub cond: Box<Expr>,
+        pub body: Block,
+    }
+}
+
+ast_struct! {
+    /// A yield expression: `yield expr`.
+    ///
+    /// *This type is available if Syn is built with the `"full"` feature.*
+    pub struct ExprYield #full {
+        pub attrs: Vec<Attribute>,
+        pub yield_token: Token![yield],
+        pub expr: Option<Box<Expr>>,
+    }
+}
+
+#[cfg(feature = "extra-traits")]
+impl Eq for Expr {}
+
+#[cfg(feature = "extra-traits")]
+impl PartialEq for Expr {
+    fn eq(&self, other: &Self) -> bool {
+        match (self, other) {
+            (Expr::Array(this), Expr::Array(other)) => this == other,
+            (Expr::Assign(this), Expr::Assign(other)) => this == other,
+            (Expr::AssignOp(this), Expr::AssignOp(other)) => this == other,
+            (Expr::Async(this), Expr::Async(other)) => this == other,
+            (Expr::Await(this), Expr::Await(other)) => this == other,
+            (Expr::Binary(this), Expr::Binary(other)) => this == other,
+            (Expr::Block(this), Expr::Block(other)) => this == other,
+            (Expr::Box(this), Expr::Box(other)) => this == other,
+            (Expr::Break(this), Expr::Break(other)) => this == other,
+            (Expr::Call(this), Expr::Call(other)) => this == other,
+            (Expr::Cast(this), Expr::Cast(other)) => this == other,
+            (Expr::Closure(this), Expr::Closure(other)) => this == other,
+            (Expr::Continue(this), Expr::Continue(other)) => this == other,
+            (Expr::Field(this), Expr::Field(other)) => this == other,
+            (Expr::ForLoop(this), Expr::ForLoop(other)) => this == other,
+            (Expr::Group(this), Expr::Group(other)) => this == other,
+            (Expr::If(this), Expr::If(other)) => this == other,
+            (Expr::Index(this), Expr::Index(other)) => this == other,
+            (Expr::Let(this), Expr::Let(other)) => this == other,
+            (Expr::Lit(this), Expr::Lit(other)) => this == other,
+            (Expr::Loop(this), Expr::Loop(other)) => this == other,
+            (Expr::Macro(this), Expr::Macro(other)) => this == other,
+            (Expr::Match(this), Expr::Match(other)) => this == other,
+            (Expr::MethodCall(this), Expr::MethodCall(other)) => this == other,
+            (Expr::Paren(this), Expr::Paren(other)) => this == other,
+            (Expr::Path(this), Expr::Path(other)) => this == other,
+            (Expr::Range(this), Expr::Range(other)) => this == other,
+            (Expr::Reference(this), Expr::Reference(other)) => this == other,
+            (Expr::Repeat(this), Expr::Repeat(other)) => this == other,
+            (Expr::Return(this), Expr::Return(other)) => this == other,
+            (Expr::Struct(this), Expr::Struct(other)) => this == other,
+            (Expr::Try(this), Expr::Try(other)) => this == other,
+            (Expr::TryBlock(this), Expr::TryBlock(other)) => this == other,
+            (Expr::Tuple(this), Expr::Tuple(other)) => this == other,
+            (Expr::Type(this), Expr::Type(other)) => this == other,
+            (Expr::Unary(this), Expr::Unary(other)) => this == other,
+            (Expr::Unsafe(this), Expr::Unsafe(other)) => this == other,
+            (Expr::Verbatim(this), Expr::Verbatim(other)) => {
+                TokenStreamHelper(this) == TokenStreamHelper(other)
+            }
+            (Expr::While(this), Expr::While(other)) => this == other,
+            (Expr::Yield(this), Expr::Yield(other)) => this == other,
+            _ => false,
+        }
+    }
+}
+
+#[cfg(feature = "extra-traits")]
+impl Hash for Expr {
+    fn hash<H>(&self, hash: &mut H)
+    where
+        H: Hasher,
+    {
+        match self {
+            Expr::Array(expr) => {
+                hash.write_u8(0);
+                expr.hash(hash);
+            }
+            Expr::Assign(expr) => {
+                hash.write_u8(1);
+                expr.hash(hash);
+            }
+            Expr::AssignOp(expr) => {
+                hash.write_u8(2);
+                expr.hash(hash);
+            }
+            Expr::Async(expr) => {
+                hash.write_u8(3);
+                expr.hash(hash);
+            }
+            Expr::Await(expr) => {
+                hash.write_u8(4);
+                expr.hash(hash);
+            }
+            Expr::Binary(expr) => {
+                hash.write_u8(5);
+                expr.hash(hash);
+            }
+            Expr::Block(expr) => {
+                hash.write_u8(6);
+                expr.hash(hash);
+            }
+            Expr::Box(expr) => {
+                hash.write_u8(7);
+                expr.hash(hash);
+            }
+            Expr::Break(expr) => {
+                hash.write_u8(8);
+                expr.hash(hash);
+            }
+            Expr::Call(expr) => {
+                hash.write_u8(9);
+                expr.hash(hash);
+            }
+            Expr::Cast(expr) => {
+                hash.write_u8(10);
+                expr.hash(hash);
+            }
+            Expr::Closure(expr) => {
+                hash.write_u8(11);
+                expr.hash(hash);
+            }
+            Expr::Continue(expr) => {
+                hash.write_u8(12);
+                expr.hash(hash);
+            }
+            Expr::Field(expr) => {
+                hash.write_u8(13);
+                expr.hash(hash);
+            }
+            Expr::ForLoop(expr) => {
+                hash.write_u8(14);
+                expr.hash(hash);
+            }
+            Expr::Group(expr) => {
+                hash.write_u8(15);
+                expr.hash(hash);
+            }
+            Expr::If(expr) => {
+                hash.write_u8(16);
+                expr.hash(hash);
+            }
+            Expr::Index(expr) => {
+                hash.write_u8(17);
+                expr.hash(hash);
+            }
+            Expr::Let(expr) => {
+                hash.write_u8(18);
+                expr.hash(hash);
+            }
+            Expr::Lit(expr) => {
+                hash.write_u8(19);
+                expr.hash(hash);
+            }
+            Expr::Loop(expr) => {
+                hash.write_u8(20);
+                expr.hash(hash);
+            }
+            Expr::Macro(expr) => {
+                hash.write_u8(21);
+                expr.hash(hash);
+            }
+            Expr::Match(expr) => {
+                hash.write_u8(22);
+                expr.hash(hash);
+            }
+            Expr::MethodCall(expr) => {
+                hash.write_u8(23);
+                expr.hash(hash);
+            }
+            Expr::Paren(expr) => {
+                hash.write_u8(24);
+                expr.hash(hash);
+            }
+            Expr::Path(expr) => {
+                hash.write_u8(25);
+                expr.hash(hash);
+            }
+            Expr::Range(expr) => {
+                hash.write_u8(26);
+                expr.hash(hash);
+            }
+            Expr::Reference(expr) => {
+                hash.write_u8(27);
+                expr.hash(hash);
+            }
+            Expr::Repeat(expr) => {
+                hash.write_u8(28);
+                expr.hash(hash);
+            }
+            Expr::Return(expr) => {
+                hash.write_u8(29);
+                expr.hash(hash);
+            }
+            Expr::Struct(expr) => {
+                hash.write_u8(30);
+                expr.hash(hash);
+            }
+            Expr::Try(expr) => {
+                hash.write_u8(31);
+                expr.hash(hash);
+            }
+            Expr::TryBlock(expr) => {
+                hash.write_u8(32);
+                expr.hash(hash);
+            }
+            Expr::Tuple(expr) => {
+                hash.write_u8(33);
+                expr.hash(hash);
+            }
+            Expr::Type(expr) => {
+                hash.write_u8(34);
+                expr.hash(hash);
+            }
+            Expr::Unary(expr) => {
+                hash.write_u8(35);
+                expr.hash(hash);
+            }
+            Expr::Unsafe(expr) => {
+                hash.write_u8(36);
+                expr.hash(hash);
+            }
+            Expr::Verbatim(expr) => {
+                hash.write_u8(37);
+                TokenStreamHelper(expr).hash(hash);
+            }
+            Expr::While(expr) => {
+                hash.write_u8(38);
+                expr.hash(hash);
+            }
+            Expr::Yield(expr) => {
+                hash.write_u8(39);
+                expr.hash(hash);
+            }
+            Expr::__Nonexhaustive => unreachable!(),
+        }
+    }
+}
+
+impl Expr {
+    #[cfg(all(feature = "parsing", feature = "full"))]
+    pub(crate) fn replace_attrs(&mut self, new: Vec<Attribute>) -> Vec<Attribute> {
+        match self {
+            Expr::Box(ExprBox { attrs, .. })
+            | Expr::Array(ExprArray { attrs, .. })
+            | Expr::Call(ExprCall { attrs, .. })
+            | Expr::MethodCall(ExprMethodCall { attrs, .. })
+            | Expr::Tuple(ExprTuple { attrs, .. })
+            | Expr::Binary(ExprBinary { attrs, .. })
+            | Expr::Unary(ExprUnary { attrs, .. })
+            | Expr::Lit(ExprLit { attrs, .. })
+            | Expr::Cast(ExprCast { attrs, .. })
+            | Expr::Type(ExprType { attrs, .. })
+            | Expr::Let(ExprLet { attrs, .. })
+            | Expr::If(ExprIf { attrs, .. })
+            | Expr::While(ExprWhile { attrs, .. })
+            | Expr::ForLoop(ExprForLoop { attrs, .. })
+            | Expr::Loop(ExprLoop { attrs, .. })
+            | Expr::Match(ExprMatch { attrs, .. })
+            | Expr::Closure(ExprClosure { attrs, .. })
+            | Expr::Unsafe(ExprUnsafe { attrs, .. })
+            | Expr::Block(ExprBlock { attrs, .. })
+            | Expr::Assign(ExprAssign { attrs, .. })
+            | Expr::AssignOp(ExprAssignOp { attrs, .. })
+            | Expr::Field(ExprField { attrs, .. })
+            | Expr::Index(ExprIndex { attrs, .. })
+            | Expr::Range(ExprRange { attrs, .. })
+            | Expr::Path(ExprPath { attrs, .. })
+            | Expr::Reference(ExprReference { attrs, .. })
+            | Expr::Break(ExprBreak { attrs, .. })
+            | Expr::Continue(ExprContinue { attrs, .. })
+            | Expr::Return(ExprReturn { attrs, .. })
+            | Expr::Macro(ExprMacro { attrs, .. })
+            | Expr::Struct(ExprStruct { attrs, .. })
+            | Expr::Repeat(ExprRepeat { attrs, .. })
+            | Expr::Paren(ExprParen { attrs, .. })
+            | Expr::Group(ExprGroup { attrs, .. })
+            | Expr::Try(ExprTry { attrs, .. })
+            | Expr::Async(ExprAsync { attrs, .. })
+            | Expr::Await(ExprAwait { attrs, .. })
+            | Expr::TryBlock(ExprTryBlock { attrs, .. })
+            | Expr::Yield(ExprYield { attrs, .. }) => mem::replace(attrs, new),
+            Expr::Verbatim(_) => Vec::new(),
+            Expr::__Nonexhaustive => unreachable!(),
+        }
+    }
+}
+
+ast_enum! {
+    /// A struct or tuple struct field accessed in a struct literal or field
+    /// expression.
+    ///
+    /// *This type is available if Syn is built with the `"derive"` or `"full"`
+    /// feature.*
+    #[derive(Eq, PartialEq, Hash)]
+    pub enum Member #manual_extra_traits {
+        /// A named field like `self.x`.
+        Named(Ident),
+        /// An unnamed field like `self.0`.
+        Unnamed(Index),
+    }
+}
+
+#[cfg(feature = "printing")]
+impl IdentFragment for Member {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            Member::Named(m) => Display::fmt(m, formatter),
+            Member::Unnamed(m) => Display::fmt(&m.index, formatter),
+        }
+    }
+
+    fn span(&self) -> Option<Span> {
+        match self {
+            Member::Named(m) => Some(m.span()),
+            Member::Unnamed(m) => Some(m.span),
+        }
+    }
+}
+
+ast_struct! {
+    /// The index of an unnamed tuple struct field.
+    ///
+    /// *This type is available if Syn is built with the `"derive"` or `"full"`
+    /// feature.*
+    pub struct Index #manual_extra_traits {
+        pub index: u32,
+        pub span: Span,
+    }
+}
+
+impl From<usize> for Index {
+    fn from(index: usize) -> Index {
+        assert!(index < u32::max_value() as usize);
+        Index {
+            index: index as u32,
+            span: Span::call_site(),
+        }
+    }
+}
+
+impl Eq for Index {}
+
+impl PartialEq for Index {
+    fn eq(&self, other: &Self) -> bool {
+        self.index == other.index
+    }
+}
+
+impl Hash for Index {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        self.index.hash(state);
+    }
+}
+
+#[cfg(feature = "printing")]
+impl IdentFragment for Index {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        Display::fmt(&self.index, formatter)
+    }
+
+    fn span(&self) -> Option<Span> {
+        Some(self.span)
+    }
+}
+
+#[cfg(feature = "full")]
+ast_struct! {
+    #[derive(Default)]
+    pub struct Reserved {
+        _private: (),
+    }
+}
+
+#[cfg(feature = "full")]
+ast_struct! {
+    /// The `::<>` explicit type parameters passed to a method call:
+    /// `parse::<u64>()`.
+    ///
+    /// *This type is available if Syn is built with the `"full"` feature.*
+    pub struct MethodTurbofish {
+        pub colon2_token: Token![::],
+        pub lt_token: Token![<],
+        pub args: Punctuated<GenericMethodArgument, Token![,]>,
+        pub gt_token: Token![>],
+    }
+}
+
+#[cfg(feature = "full")]
+ast_enum! {
+    /// An individual generic argument to a method, like `T`.
+    ///
+    /// *This type is available if Syn is built with the `"full"` feature.*
+    pub enum GenericMethodArgument {
+        /// A type argument.
+        Type(Type),
+        /// A const expression. Must be inside of a block.
+        ///
+        /// NOTE: Identity expressions are represented as Type arguments, as
+        /// they are indistinguishable syntactically.
+        Const(Expr),
+    }
+}
+
+#[cfg(feature = "full")]
+ast_struct! {
+    /// A field-value pair in a struct literal.
+    ///
+    /// *This type is available if Syn is built with the `"full"` feature.*
+    pub struct FieldValue {
+        /// Attributes tagged on the field.
+        pub attrs: Vec<Attribute>,
+
+        /// Name or index of the field.
+        pub member: Member,
+
+        /// The colon in `Struct { x: x }`. If written in shorthand like
+        /// `Struct { x }`, there is no colon.
+        pub colon_token: Option<Token![:]>,
+
+        /// Value of the field.
+        pub expr: Expr,
+    }
+}
+
+#[cfg(feature = "full")]
+ast_struct! {
+    /// A lifetime labeling a `for`, `while`, or `loop`.
+    ///
+    /// *This type is available if Syn is built with the `"full"` feature.*
+    pub struct Label {
+        pub name: Lifetime,
+        pub colon_token: Token![:],
+    }
+}
+
+#[cfg(feature = "full")]
+ast_struct! {
+    /// One arm of a `match` expression: `0...10 => { return true; }`.
+    ///
+    /// As in:
+    ///
+    /// ```
+    /// # fn f() -> bool {
+    /// #     let n = 0;
+    /// match n {
+    ///     0...10 => {
+    ///         return true;
+    ///     }
+    ///     // ...
+    ///     # _ => {}
+    /// }
+    /// #   false
+    /// # }
+    /// ```
+    ///
+    /// *This type is available if Syn is built with the `"full"` feature.*
+    pub struct Arm {
+        pub attrs: Vec<Attribute>,
+        pub pat: Pat,
+        pub guard: Option<(Token![if], Box<Expr>)>,
+        pub fat_arrow_token: Token![=>],
+        pub body: Box<Expr>,
+        pub comma: Option<Token![,]>,
+    }
+}
+
+#[cfg(feature = "full")]
+ast_enum! {
+    /// Limit types of a range, inclusive or exclusive.
+    ///
+    /// *This type is available if Syn is built with the `"full"` feature.*
+    #[cfg_attr(feature = "clone-impls", derive(Copy))]
+    pub enum RangeLimits {
+        /// Inclusive at the beginning, exclusive at the end.
+        HalfOpen(Token![..]),
+        /// Inclusive at the beginning and end.
+        Closed(Token![..=]),
+    }
+}
+
+#[cfg(any(feature = "parsing", feature = "printing"))]
+#[cfg(feature = "full")]
+pub(crate) fn requires_terminator(expr: &Expr) -> bool {
+    // see https://github.com/rust-lang/rust/blob/eb8f2586e/src/libsyntax/parse/classify.rs#L17-L37
+    match *expr {
+        Expr::Unsafe(..)
+        | Expr::Block(..)
+        | Expr::If(..)
+        | Expr::Match(..)
+        | Expr::While(..)
+        | Expr::Loop(..)
+        | Expr::ForLoop(..)
+        | Expr::Async(..)
+        | Expr::TryBlock(..) => false,
+        _ => true,
+    }
+}
+
+#[cfg(feature = "parsing")]
+pub(crate) mod parsing {
+    use super::*;
+
+    use crate::parse::discouraged::Speculative;
+    use crate::parse::{Parse, ParseStream, Result};
+    use crate::path;
+
+    // When we're parsing expressions which occur before blocks, like in an if
+    // statement's condition, we cannot parse a struct literal.
+    //
+    // Struct literals are ambiguous in certain positions
+    // https://github.com/rust-lang/rfcs/pull/92
+    #[derive(Copy, Clone)]
+    pub struct AllowStruct(bool);
+
+    #[derive(Copy, Clone, PartialEq, PartialOrd)]
+    enum Precedence {
+        Any,
+        Assign,
+        Range,
+        Or,
+        And,
+        Compare,
+        BitOr,
+        BitXor,
+        BitAnd,
+        Shift,
+        Arithmetic,
+        Term,
+        Cast,
+    }
+
+    impl Precedence {
+        fn of(op: &BinOp) -> Self {
+            match *op {
+                BinOp::Add(_) | BinOp::Sub(_) => Precedence::Arithmetic,
+                BinOp::Mul(_) | BinOp::Div(_) | BinOp::Rem(_) => Precedence::Term,
+                BinOp::And(_) => Precedence::And,
+                BinOp::Or(_) => Precedence::Or,
+                BinOp::BitXor(_) => Precedence::BitXor,
+                BinOp::BitAnd(_) => Precedence::BitAnd,
+                BinOp::BitOr(_) => Precedence::BitOr,
+                BinOp::Shl(_) | BinOp::Shr(_) => Precedence::Shift,
+                BinOp::Eq(_)
+                | BinOp::Lt(_)
+                | BinOp::Le(_)
+                | BinOp::Ne(_)
+                | BinOp::Ge(_)
+                | BinOp::Gt(_) => Precedence::Compare,
+                BinOp::AddEq(_)
+                | BinOp::SubEq(_)
+                | BinOp::MulEq(_)
+                | BinOp::DivEq(_)
+                | BinOp::RemEq(_)
+                | BinOp::BitXorEq(_)
+                | BinOp::BitAndEq(_)
+                | BinOp::BitOrEq(_)
+                | BinOp::ShlEq(_)
+                | BinOp::ShrEq(_) => Precedence::Assign,
+            }
+        }
+    }
+
+    impl Parse for Expr {
+        fn parse(input: ParseStream) -> Result<Self> {
+            ambiguous_expr(input, AllowStruct(true))
+        }
+    }
+
+    #[cfg(feature = "full")]
+    fn expr_no_struct(input: ParseStream) -> Result<Expr> {
+        ambiguous_expr(input, AllowStruct(false))
+    }
+
+    #[cfg(feature = "full")]
+    fn parse_expr(
+        input: ParseStream,
+        mut lhs: Expr,
+        allow_struct: AllowStruct,
+        base: Precedence,
+    ) -> Result<Expr> {
+        loop {
+            if input
+                .fork()
+                .parse::<BinOp>()
+                .ok()
+                .map_or(false, |op| Precedence::of(&op) >= base)
+            {
+                let op: BinOp = input.parse()?;
+                let precedence = Precedence::of(&op);
+                let mut rhs = unary_expr(input, allow_struct)?;
+                loop {
+                    let next = peek_precedence(input);
+                    if next > precedence || next == precedence && precedence == Precedence::Assign {
+                        rhs = parse_expr(input, rhs, allow_struct, next)?;
+                    } else {
+                        break;
+                    }
+                }
+                lhs = if precedence == Precedence::Assign {
+                    Expr::AssignOp(ExprAssignOp {
+                        attrs: Vec::new(),
+                        left: Box::new(lhs),
+                        op,
+                        right: Box::new(rhs),
+                    })
+                } else {
+                    Expr::Binary(ExprBinary {
+                        attrs: Vec::new(),
+                        left: Box::new(lhs),
+                        op,
+                        right: Box::new(rhs),
+                    })
+                };
+            } else if Precedence::Assign >= base
+                && input.peek(Token![=])
+                && !input.peek(Token![==])
+                && !input.peek(Token![=>])
+            {
+                let eq_token: Token![=] = input.parse()?;
+                let mut rhs = unary_expr(input, allow_struct)?;
+                loop {
+                    let next = peek_precedence(input);
+                    if next >= Precedence::Assign {
+                        rhs = parse_expr(input, rhs, allow_struct, next)?;
+                    } else {
+                        break;
+                    }
+                }
+                lhs = Expr::Assign(ExprAssign {
+                    attrs: Vec::new(),
+                    left: Box::new(lhs),
+                    eq_token,
+                    right: Box::new(rhs),
+                });
+            } else if Precedence::Range >= base && input.peek(Token![..]) {
+                let limits: RangeLimits = input.parse()?;
+                let rhs = if input.is_empty()
+                    || input.peek(Token![,])
+                    || input.peek(Token![;])
+                    || !allow_struct.0 && input.peek(token::Brace)
+                {
+                    None
+                } else {
+                    let mut rhs = unary_expr(input, allow_struct)?;
+                    loop {
+                        let next = peek_precedence(input);
+                        if next > Precedence::Range {
+                            rhs = parse_expr(input, rhs, allow_struct, next)?;
+                        } else {
+                            break;
+                        }
+                    }
+                    Some(rhs)
+                };
+                lhs = Expr::Range(ExprRange {
+                    attrs: Vec::new(),
+                    from: Some(Box::new(lhs)),
+                    limits,
+                    to: rhs.map(Box::new),
+                });
+            } else if Precedence::Cast >= base && input.peek(Token![as]) {
+                let as_token: Token![as] = input.parse()?;
+                let ty = input.call(Type::without_plus)?;
+                lhs = Expr::Cast(ExprCast {
+                    attrs: Vec::new(),
+                    expr: Box::new(lhs),
+                    as_token,
+                    ty: Box::new(ty),
+                });
+            } else if Precedence::Cast >= base && input.peek(Token![:]) && !input.peek(Token![::]) {
+                let colon_token: Token![:] = input.parse()?;
+                let ty = input.call(Type::without_plus)?;
+                lhs = Expr::Type(ExprType {
+                    attrs: Vec::new(),
+                    expr: Box::new(lhs),
+                    colon_token,
+                    ty: Box::new(ty),
+                });
+            } else {
+                break;
+            }
+        }
+        Ok(lhs)
+    }
+
+    #[cfg(not(feature = "full"))]
+    fn parse_expr(
+        input: ParseStream,
+        mut lhs: Expr,
+        allow_struct: AllowStruct,
+        base: Precedence,
+    ) -> Result<Expr> {
+        loop {
+            if input
+                .fork()
+                .parse::<BinOp>()
+                .ok()
+                .map_or(false, |op| Precedence::of(&op) >= base)
+            {
+                let op: BinOp = input.parse()?;
+                let precedence = Precedence::of(&op);
+                let mut rhs = unary_expr(input, allow_struct)?;
+                loop {
+                    let next = peek_precedence(input);
+                    if next > precedence || next == precedence && precedence == Precedence::Assign {
+                        rhs = parse_expr(input, rhs, allow_struct, next)?;
+                    } else {
+                        break;
+                    }
+                }
+                lhs = Expr::Binary(ExprBinary {
+                    attrs: Vec::new(),
+                    left: Box::new(lhs),
+                    op,
+                    right: Box::new(rhs),
+                });
+            } else if Precedence::Cast >= base && input.peek(Token![as]) {
+                let as_token: Token![as] = input.parse()?;
+                let ty = input.call(Type::without_plus)?;
+                lhs = Expr::Cast(ExprCast {
+                    attrs: Vec::new(),
+                    expr: Box::new(lhs),
+                    as_token,
+                    ty: Box::new(ty),
+                });
+            } else {
+                break;
+            }
+        }
+        Ok(lhs)
+    }
+
+    fn peek_precedence(input: ParseStream) -> Precedence {
+        if let Ok(op) = input.fork().parse() {
+            Precedence::of(&op)
+        } else if input.peek(Token![=]) && !input.peek(Token![=>]) {
+            Precedence::Assign
+        } else if input.peek(Token![..]) {
+            Precedence::Range
+        } else if input.peek(Token![as]) || input.peek(Token![:]) && !input.peek(Token![::]) {
+            Precedence::Cast
+        } else {
+            Precedence::Any
+        }
+    }
+
+    // Parse an arbitrary expression.
+    fn ambiguous_expr(input: ParseStream, allow_struct: AllowStruct) -> Result<Expr> {
+        let lhs = unary_expr(input, allow_struct)?;
+        parse_expr(input, lhs, allow_struct, Precedence::Any)
+    }
+
+    // <UnOp> <trailer>
+    // & <trailer>
+    // &mut <trailer>
+    // box <trailer>
+    #[cfg(feature = "full")]
+    fn unary_expr(input: ParseStream, allow_struct: AllowStruct) -> Result<Expr> {
+        let ahead = input.fork();
+        let attrs = ahead.call(Attribute::parse_outer)?;
+        if ahead.peek(Token![&])
+            || ahead.peek(Token![box])
+            || ahead.peek(Token![*])
+            || ahead.peek(Token![!])
+            || ahead.peek(Token![-])
+        {
+            input.advance_to(&ahead);
+            if input.peek(Token![&]) {
+                Ok(Expr::Reference(ExprReference {
+                    attrs,
+                    and_token: input.parse()?,
+                    raw: Reserved::default(),
+                    mutability: input.parse()?,
+                    expr: Box::new(unary_expr(input, allow_struct)?),
+                }))
+            } else if input.peek(Token![box]) {
+                Ok(Expr::Box(ExprBox {
+                    attrs,
+                    box_token: input.parse()?,
+                    expr: Box::new(unary_expr(input, allow_struct)?),
+                }))
+            } else {
+                Ok(Expr::Unary(ExprUnary {
+                    attrs,
+                    op: input.parse()?,
+                    expr: Box::new(unary_expr(input, allow_struct)?),
+                }))
+            }
+        } else {
+            trailer_expr(input, allow_struct)
+        }
+    }
+
+    #[cfg(not(feature = "full"))]
+    fn unary_expr(input: ParseStream, allow_struct: AllowStruct) -> Result<Expr> {
+        let ahead = input.fork();
+        let attrs = ahead.call(Attribute::parse_outer)?;
+        if ahead.peek(Token![*]) || ahead.peek(Token![!]) || ahead.peek(Token![-]) {
+            input.advance_to(&ahead);
+            Ok(Expr::Unary(ExprUnary {
+                attrs,
+                op: input.parse()?,
+                expr: Box::new(unary_expr(input, allow_struct)?),
+            }))
+        } else {
+            trailer_expr(input, allow_struct)
+        }
+    }
+
+    // <atom> (..<args>) ...
+    // <atom> . <ident> (..<args>) ...
+    // <atom> . <ident> ...
+    // <atom> . <lit> ...
+    // <atom> [ <expr> ] ...
+    // <atom> ? ...
+    #[cfg(feature = "full")]
+    fn trailer_expr(input: ParseStream, allow_struct: AllowStruct) -> Result<Expr> {
+        if input.peek(token::Group) {
+            return input.call(expr_group).map(Expr::Group);
+        }
+
+        let outer_attrs = input.call(Attribute::parse_outer)?;
+
+        let atom = atom_expr(input, allow_struct)?;
+        let mut e = trailer_helper(input, atom)?;
+
+        let inner_attrs = e.replace_attrs(Vec::new());
+        let attrs = private::attrs(outer_attrs, inner_attrs);
+        e.replace_attrs(attrs);
+        Ok(e)
+    }
+
+    #[cfg(feature = "full")]
+    fn trailer_helper(input: ParseStream, mut e: Expr) -> Result<Expr> {
+        loop {
+            if input.peek(token::Paren) {
+                let content;
+                e = Expr::Call(ExprCall {
+                    attrs: Vec::new(),
+                    func: Box::new(e),
+                    paren_token: parenthesized!(content in input),
+                    args: content.parse_terminated(Expr::parse)?,
+                });
+            } else if input.peek(Token![.]) && !input.peek(Token![..]) {
+                let dot_token: Token![.] = input.parse()?;
+
+                if input.peek(token::Await) {
+                    e = Expr::Await(ExprAwait {
+                        attrs: Vec::new(),
+                        base: Box::new(e),
+                        dot_token,
+                        await_token: input.parse()?,
+                    });
+                    continue;
+                }
+
+                let member: Member = input.parse()?;
+                let turbofish = if member.is_named() && input.peek(Token![::]) {
+                    Some(MethodTurbofish {
+                        colon2_token: input.parse()?,
+                        lt_token: input.parse()?,
+                        args: {
+                            let mut args = Punctuated::new();
+                            loop {
+                                if input.peek(Token![>]) {
+                                    break;
+                                }
+                                let value = input.call(generic_method_argument)?;
+                                args.push_value(value);
+                                if input.peek(Token![>]) {
+                                    break;
+                                }
+                                let punct = input.parse()?;
+                                args.push_punct(punct);
+                            }
+                            args
+                        },
+                        gt_token: input.parse()?,
+                    })
+                } else {
+                    None
+                };
+
+                if turbofish.is_some() || input.peek(token::Paren) {
+                    if let Member::Named(method) = member {
+                        let content;
+                        e = Expr::MethodCall(ExprMethodCall {
+                            attrs: Vec::new(),
+                            receiver: Box::new(e),
+                            dot_token,
+                            method,
+                            turbofish,
+                            paren_token: parenthesized!(content in input),
+                            args: content.parse_terminated(Expr::parse)?,
+                        });
+                        continue;
+                    }
+                }
+
+                e = Expr::Field(ExprField {
+                    attrs: Vec::new(),
+                    base: Box::new(e),
+                    dot_token,
+                    member,
+                });
+            } else if input.peek(token::Bracket) {
+                let content;
+                e = Expr::Index(ExprIndex {
+                    attrs: Vec::new(),
+                    expr: Box::new(e),
+                    bracket_token: bracketed!(content in input),
+                    index: content.parse()?,
+                });
+            } else if input.peek(Token![?]) {
+                e = Expr::Try(ExprTry {
+                    attrs: Vec::new(),
+                    expr: Box::new(e),
+                    question_token: input.parse()?,
+                });
+            } else {
+                break;
+            }
+        }
+        Ok(e)
+    }
+
+    #[cfg(not(feature = "full"))]
+    fn trailer_expr(input: ParseStream, allow_struct: AllowStruct) -> Result<Expr> {
+        let mut e = atom_expr(input, allow_struct)?;
+
+        loop {
+            if input.peek(token::Paren) {
+                let content;
+                e = Expr::Call(ExprCall {
+                    attrs: Vec::new(),
+                    func: Box::new(e),
+                    paren_token: parenthesized!(content in input),
+                    args: content.parse_terminated(Expr::parse)?,
+                });
+            } else if input.peek(Token![.]) && !input.peek(Token![..]) && !input.peek2(token::Await)
+            {
+                e = Expr::Field(ExprField {
+                    attrs: Vec::new(),
+                    base: Box::new(e),
+                    dot_token: input.parse()?,
+                    member: input.parse()?,
+                });
+            } else if input.peek(token::Bracket) {
+                let content;
+                e = Expr::Index(ExprIndex {
+                    attrs: Vec::new(),
+                    expr: Box::new(e),
+                    bracket_token: bracketed!(content in input),
+                    index: content.parse()?,
+                });
+            } else {
+                break;
+            }
+        }
+
+        Ok(e)
+    }
+
+    // Parse all atomic expressions which don't have to worry about precedence
+    // interactions, as they are fully contained.
+    #[cfg(feature = "full")]
+    fn atom_expr(input: ParseStream, allow_struct: AllowStruct) -> Result<Expr> {
+        if input.peek(token::Group) {
+            input.call(expr_group).map(Expr::Group)
+        } else if input.peek(Lit) {
+            input.parse().map(Expr::Lit)
+        } else if input.peek(Token![async])
+            && (input.peek2(token::Brace) || input.peek2(Token![move]) && input.peek3(token::Brace))
+        {
+            input.call(expr_async).map(Expr::Async)
+        } else if input.peek(Token![try]) && input.peek2(token::Brace) {
+            input.call(expr_try_block).map(Expr::TryBlock)
+        } else if input.peek(Token![|])
+            || input.peek(Token![async]) && (input.peek2(Token![|]) || input.peek2(Token![move]))
+            || input.peek(Token![static])
+            || input.peek(Token![move])
+        {
+            expr_closure(input, allow_struct).map(Expr::Closure)
+        } else if input.peek(Ident)
+            || input.peek(Token![::])
+            || input.peek(Token![<])
+            || input.peek(Token![self])
+            || input.peek(Token![Self])
+            || input.peek(Token![super])
+            || input.peek(Token![extern])
+            || input.peek(Token![crate])
+        {
+            path_or_macro_or_struct(input, allow_struct)
+        } else if input.peek(token::Paren) {
+            paren_or_tuple(input)
+        } else if input.peek(Token![break]) {
+            expr_break(input, allow_struct).map(Expr::Break)
+        } else if input.peek(Token![continue]) {
+            input.call(expr_continue).map(Expr::Continue)
+        } else if input.peek(Token![return]) {
+            expr_ret(input, allow_struct).map(Expr::Return)
+        } else if input.peek(token::Bracket) {
+            array_or_repeat(input)
+        } else if input.peek(Token![let]) {
+            input.call(expr_let).map(Expr::Let)
+        } else if input.peek(Token![if]) {
+            input.parse().map(Expr::If)
+        } else if input.peek(Token![while]) {
+            input.parse().map(Expr::While)
+        } else if input.peek(Token![for]) {
+            input.parse().map(Expr::ForLoop)
+        } else if input.peek(Token![loop]) {
+            input.parse().map(Expr::Loop)
+        } else if input.peek(Token![match]) {
+            input.parse().map(Expr::Match)
+        } else if input.peek(Token![yield]) {
+            input.call(expr_yield).map(Expr::Yield)
+        } else if input.peek(Token![unsafe]) {
+            input.call(expr_unsafe).map(Expr::Unsafe)
+        } else if input.peek(token::Brace) {
+            input.call(expr_block).map(Expr::Block)
+        } else if input.peek(Token![..]) {
+            expr_range(input, allow_struct).map(Expr::Range)
+        } else if input.peek(Lifetime) {
+            let the_label: Label = input.parse()?;
+            let mut expr = if input.peek(Token![while]) {
+                Expr::While(input.parse()?)
+            } else if input.peek(Token![for]) {
+                Expr::ForLoop(input.parse()?)
+            } else if input.peek(Token![loop]) {
+                Expr::Loop(input.parse()?)
+            } else if input.peek(token::Brace) {
+                Expr::Block(input.call(expr_block)?)
+            } else {
+                return Err(input.error("expected loop or block expression"));
+            };
+            match &mut expr {
+                Expr::While(ExprWhile { label, .. })
+                | Expr::ForLoop(ExprForLoop { label, .. })
+                | Expr::Loop(ExprLoop { label, .. })
+                | Expr::Block(ExprBlock { label, .. }) => *label = Some(the_label),
+                _ => unreachable!(),
+            }
+            Ok(expr)
+        } else {
+            Err(input.error("expected expression"))
+        }
+    }
+
+    #[cfg(not(feature = "full"))]
+    fn atom_expr(input: ParseStream, _allow_struct: AllowStruct) -> Result<Expr> {
+        if input.peek(Lit) {
+            input.parse().map(Expr::Lit)
+        } else if input.peek(token::Paren) {
+            input.call(expr_paren).map(Expr::Paren)
+        } else if input.peek(Ident)
+            || input.peek(Token![::])
+            || input.peek(Token![<])
+            || input.peek(Token![self])
+            || input.peek(Token![Self])
+            || input.peek(Token![super])
+            || input.peek(Token![extern])
+            || input.peek(Token![crate])
+        {
+            input.parse().map(Expr::Path)
+        } else {
+            Err(input.error("unsupported expression; enable syn's features=[\"full\"]"))
+        }
+    }
+
+    #[cfg(feature = "full")]
+    fn path_or_macro_or_struct(input: ParseStream, allow_struct: AllowStruct) -> Result<Expr> {
+        let expr: ExprPath = input.parse()?;
+        if expr.qself.is_some() {
+            return Ok(Expr::Path(expr));
+        }
+
+        if input.peek(Token![!]) && !input.peek(Token![!=]) {
+            let mut contains_arguments = false;
+            for segment in &expr.path.segments {
+                match segment.arguments {
+                    PathArguments::None => {}
+                    PathArguments::AngleBracketed(_) | PathArguments::Parenthesized(_) => {
+                        contains_arguments = true;
+                    }
+                }
+            }
+
+            if !contains_arguments {
+                let bang_token: Token![!] = input.parse()?;
+                let (delimiter, tokens) = mac::parse_delimiter(input)?;
+                return Ok(Expr::Macro(ExprMacro {
+                    attrs: Vec::new(),
+                    mac: Macro {
+                        path: expr.path,
+                        bang_token,
+                        delimiter,
+                        tokens,
+                    },
+                }));
+            }
+        }
+
+        if allow_struct.0 && input.peek(token::Brace) {
+            let outer_attrs = Vec::new();
+            expr_struct_helper(input, outer_attrs, expr.path).map(Expr::Struct)
+        } else {
+            Ok(Expr::Path(expr))
+        }
+    }
+
+    #[cfg(feature = "full")]
+    fn paren_or_tuple(input: ParseStream) -> Result<Expr> {
+        let content;
+        let paren_token = parenthesized!(content in input);
+        let inner_attrs = content.call(Attribute::parse_inner)?;
+        if content.is_empty() {
+            return Ok(Expr::Tuple(ExprTuple {
+                attrs: inner_attrs,
+                paren_token,
+                elems: Punctuated::new(),
+            }));
+        }
+
+        let first: Expr = content.parse()?;
+        if content.is_empty() {
+            return Ok(Expr::Paren(ExprParen {
+                attrs: inner_attrs,
+                paren_token,
+                expr: Box::new(first),
+            }));
+        }
+
+        let mut elems = Punctuated::new();
+        elems.push_value(first);
+        while !content.is_empty() {
+            let punct = content.parse()?;
+            elems.push_punct(punct);
+            if content.is_empty() {
+                break;
+            }
+            let value = content.parse()?;
+            elems.push_value(value);
+        }
+        Ok(Expr::Tuple(ExprTuple {
+            attrs: inner_attrs,
+            paren_token,
+            elems,
+        }))
+    }
+
+    #[cfg(feature = "full")]
+    fn array_or_repeat(input: ParseStream) -> Result<Expr> {
+        let content;
+        let bracket_token = bracketed!(content in input);
+        let inner_attrs = content.call(Attribute::parse_inner)?;
+        if content.is_empty() {
+            return Ok(Expr::Array(ExprArray {
+                attrs: inner_attrs,
+                bracket_token,
+                elems: Punctuated::new(),
+            }));
+        }
+
+        let first: Expr = content.parse()?;
+        if content.is_empty() || content.peek(Token![,]) {
+            let mut elems = Punctuated::new();
+            elems.push_value(first);
+            while !content.is_empty() {
+                let punct = content.parse()?;
+                elems.push_punct(punct);
+                if content.is_empty() {
+                    break;
+                }
+                let value = content.parse()?;
+                elems.push_value(value);
+            }
+            Ok(Expr::Array(ExprArray {
+                attrs: inner_attrs,
+                bracket_token,
+                elems,
+            }))
+        } else if content.peek(Token![;]) {
+            let semi_token: Token![;] = content.parse()?;
+            let len: Expr = content.parse()?;
+            Ok(Expr::Repeat(ExprRepeat {
+                attrs: inner_attrs,
+                bracket_token,
+                expr: Box::new(first),
+                semi_token,
+                len: Box::new(len),
+            }))
+        } else {
+            Err(content.error("expected `,` or `;`"))
+        }
+    }
+
+    #[cfg(feature = "full")]
+    pub(crate) fn expr_early(input: ParseStream) -> Result<Expr> {
+        let mut attrs = input.call(Attribute::parse_outer)?;
+        let mut expr = if input.peek(Token![if]) {
+            Expr::If(input.parse()?)
+        } else if input.peek(Token![while]) {
+            Expr::While(input.parse()?)
+        } else if input.peek(Token![for]) {
+            Expr::ForLoop(input.parse()?)
+        } else if input.peek(Token![loop]) {
+            Expr::Loop(input.parse()?)
+        } else if input.peek(Token![match]) {
+            Expr::Match(input.parse()?)
+        } else if input.peek(Token![try]) && input.peek2(token::Brace) {
+            Expr::TryBlock(input.call(expr_try_block)?)
+        } else if input.peek(Token![unsafe]) {
+            Expr::Unsafe(input.call(expr_unsafe)?)
+        } else if input.peek(token::Brace) {
+            Expr::Block(input.call(expr_block)?)
+        } else {
+            let allow_struct = AllowStruct(true);
+            let mut expr = unary_expr(input, allow_struct)?;
+
+            attrs.extend(expr.replace_attrs(Vec::new()));
+            expr.replace_attrs(attrs);
+
+            return parse_expr(input, expr, allow_struct, Precedence::Any);
+        };
+
+        if input.peek(Token![.]) || input.peek(Token![?]) {
+            expr = trailer_helper(input, expr)?;
+
+            attrs.extend(expr.replace_attrs(Vec::new()));
+            expr.replace_attrs(attrs);
+
+            let allow_struct = AllowStruct(true);
+            return parse_expr(input, expr, allow_struct, Precedence::Any);
+        }
+
+        attrs.extend(expr.replace_attrs(Vec::new()));
+        expr.replace_attrs(attrs);
+        Ok(expr)
+    }
+
+    impl Parse for ExprLit {
+        fn parse(input: ParseStream) -> Result<Self> {
+            Ok(ExprLit {
+                attrs: Vec::new(),
+                lit: input.parse()?,
+            })
+        }
+    }
+
+    #[cfg(feature = "full")]
+    fn expr_group(input: ParseStream) -> Result<ExprGroup> {
+        let group = crate::group::parse_group(input)?;
+        Ok(ExprGroup {
+            attrs: Vec::new(),
+            group_token: group.token,
+            expr: group.content.parse()?,
+        })
+    }
+
+    #[cfg(not(feature = "full"))]
+    fn expr_paren(input: ParseStream) -> Result<ExprParen> {
+        let content;
+        Ok(ExprParen {
+            attrs: Vec::new(),
+            paren_token: parenthesized!(content in input),
+            expr: content.parse()?,
+        })
+    }
+
+    #[cfg(feature = "full")]
+    fn generic_method_argument(input: ParseStream) -> Result<GenericMethodArgument> {
+        // TODO parse const generics as well
+        input.parse().map(GenericMethodArgument::Type)
+    }
+
+    #[cfg(feature = "full")]
+    fn expr_let(input: ParseStream) -> Result<ExprLet> {
+        Ok(ExprLet {
+            attrs: Vec::new(),
+            let_token: input.parse()?,
+            pat: {
+                let leading_vert: Option<Token![|]> = input.parse()?;
+                let pat: Pat = input.parse()?;
+                if leading_vert.is_some()
+                    || input.peek(Token![|]) && !input.peek(Token![||]) && !input.peek(Token![|=])
+                {
+                    let mut cases = Punctuated::new();
+                    cases.push_value(pat);
+                    while input.peek(Token![|])
+                        && !input.peek(Token![||])
+                        && !input.peek(Token![|=])
+                    {
+                        let punct = input.parse()?;
+                        cases.push_punct(punct);
+                        let pat: Pat = input.parse()?;
+                        cases.push_value(pat);
+                    }
+                    Pat::Or(PatOr {
+                        attrs: Vec::new(),
+                        leading_vert,
+                        cases,
+                    })
+                } else {
+                    pat
+                }
+            },
+            eq_token: input.parse()?,
+            expr: Box::new(input.call(expr_no_struct)?),
+        })
+    }
+
+    #[cfg(feature = "full")]
+    impl Parse for ExprIf {
+        fn parse(input: ParseStream) -> Result<Self> {
+            Ok(ExprIf {
+                attrs: Vec::new(),
+                if_token: input.parse()?,
+                cond: Box::new(input.call(expr_no_struct)?),
+                then_branch: input.parse()?,
+                else_branch: {
+                    if input.peek(Token![else]) {
+                        Some(input.call(else_block)?)
+                    } else {
+                        None
+                    }
+                },
+            })
+        }
+    }
+
+    #[cfg(feature = "full")]
+    fn else_block(input: ParseStream) -> Result<(Token![else], Box<Expr>)> {
+        let else_token: Token![else] = input.parse()?;
+
+        let lookahead = input.lookahead1();
+        let else_branch = if input.peek(Token![if]) {
+            input.parse().map(Expr::If)?
+        } else if input.peek(token::Brace) {
+            Expr::Block(ExprBlock {
+                attrs: Vec::new(),
+                label: None,
+                block: input.parse()?,
+            })
+        } else {
+            return Err(lookahead.error());
+        };
+
+        Ok((else_token, Box::new(else_branch)))
+    }
+
+    #[cfg(feature = "full")]
+    impl Parse for ExprForLoop {
+        fn parse(input: ParseStream) -> Result<Self> {
+            let label: Option<Label> = input.parse()?;
+            let for_token: Token![for] = input.parse()?;
+
+            let leading_vert: Option<Token![|]> = input.parse()?;
+            let mut pat: Pat = input.parse()?;
+            if leading_vert.is_some() || input.peek(Token![|]) {
+                let mut cases = Punctuated::new();
+                cases.push_value(pat);
+                while input.peek(Token![|]) {
+                    let punct = input.parse()?;
+                    cases.push_punct(punct);
+                    let pat: Pat = input.parse()?;
+                    cases.push_value(pat);
+                }
+                pat = Pat::Or(PatOr {
+                    attrs: Vec::new(),
+                    leading_vert,
+                    cases,
+                });
+            }
+
+            let in_token: Token![in] = input.parse()?;
+            let expr: Expr = input.call(expr_no_struct)?;
+
+            let content;
+            let brace_token = braced!(content in input);
+            let inner_attrs = content.call(Attribute::parse_inner)?;
+            let stmts = content.call(Block::parse_within)?;
+
+            Ok(ExprForLoop {
+                attrs: inner_attrs,
+                label,
+                for_token,
+                pat,
+                in_token,
+                expr: Box::new(expr),
+                body: Block { brace_token, stmts },
+            })
+        }
+    }
+
+    #[cfg(feature = "full")]
+    impl Parse for ExprLoop {
+        fn parse(input: ParseStream) -> Result<Self> {
+            let label: Option<Label> = input.parse()?;
+            let loop_token: Token![loop] = input.parse()?;
+
+            let content;
+            let brace_token = braced!(content in input);
+            let inner_attrs = content.call(Attribute::parse_inner)?;
+            let stmts = content.call(Block::parse_within)?;
+
+            Ok(ExprLoop {
+                attrs: inner_attrs,
+                label,
+                loop_token,
+                body: Block { brace_token, stmts },
+            })
+        }
+    }
+
+    #[cfg(feature = "full")]
+    impl Parse for ExprMatch {
+        fn parse(input: ParseStream) -> Result<Self> {
+            let match_token: Token![match] = input.parse()?;
+            let expr = expr_no_struct(input)?;
+
+            let content;
+            let brace_token = braced!(content in input);
+            let inner_attrs = content.call(Attribute::parse_inner)?;
+
+            let mut arms = Vec::new();
+            while !content.is_empty() {
+                arms.push(content.call(Arm::parse)?);
+            }
+
+            Ok(ExprMatch {
+                attrs: inner_attrs,
+                match_token,
+                expr: Box::new(expr),
+                brace_token,
+                arms,
+            })
+        }
+    }
+
+    macro_rules! impl_by_parsing_expr {
+        (
+            $(
+                $expr_type:ty, $variant:ident, $msg:expr,
+            )*
+        ) => {
+            $(
+                #[cfg(all(feature = "full", feature = "printing"))]
+                impl Parse for $expr_type {
+                    fn parse(input: ParseStream) -> Result<Self> {
+                        let mut expr: Expr = input.parse()?;
+                        loop {
+                            match expr {
+                                Expr::$variant(inner) => return Ok(inner),
+                                Expr::Group(next) => expr = *next.expr,
+                                _ => return Err(Error::new_spanned(expr, $msg)),
+                            }
+                        }
+                    }
+                }
+            )*
+        };
+    }
+
+    impl_by_parsing_expr! {
+        ExprBox, Box, "expected box expression",
+        ExprArray, Array, "expected slice literal expression",
+        ExprCall, Call, "expected function call expression",
+        ExprMethodCall, MethodCall, "expected method call expression",
+        ExprTuple, Tuple, "expected tuple expression",
+        ExprBinary, Binary, "expected binary operation",
+        ExprUnary, Unary, "expected unary operation",
+        ExprCast, Cast, "expected cast expression",
+        ExprType, Type, "expected type ascription expression",
+        ExprLet, Let, "expected let guard",
+        ExprClosure, Closure, "expected closure expression",
+        ExprUnsafe, Unsafe, "expected unsafe block",
+        ExprBlock, Block, "expected blocked scope",
+        ExprAssign, Assign, "expected assignment expression",
+        ExprAssignOp, AssignOp, "expected compound assignment expression",
+        ExprField, Field, "expected struct field access",
+        ExprIndex, Index, "expected indexing expression",
+        ExprRange, Range, "expected range expression",
+        ExprReference, Reference, "expected referencing operation",
+        ExprBreak, Break, "expected break expression",
+        ExprContinue, Continue, "expected continue expression",
+        ExprReturn, Return, "expected return expression",
+        ExprMacro, Macro, "expected macro invocation expression",
+        ExprStruct, Struct, "expected struct literal expression",
+        ExprRepeat, Repeat, "expected array literal constructed from one repeated element",
+        ExprParen, Paren, "expected parenthesized expression",
+        ExprTry, Try, "expected try expression",
+        ExprAsync, Async, "expected async block",
+        ExprTryBlock, TryBlock, "expected try block",
+        ExprYield, Yield, "expected yield expression",
+    }
+
+    #[cfg(feature = "full")]
+    fn expr_try_block(input: ParseStream) -> Result<ExprTryBlock> {
+        Ok(ExprTryBlock {
+            attrs: Vec::new(),
+            try_token: input.parse()?,
+            block: input.parse()?,
+        })
+    }
+
+    #[cfg(feature = "full")]
+    fn expr_yield(input: ParseStream) -> Result<ExprYield> {
+        Ok(ExprYield {
+            attrs: Vec::new(),
+            yield_token: input.parse()?,
+            expr: {
+                if !input.is_empty() && !input.peek(Token![,]) && !input.peek(Token![;]) {
+                    Some(input.parse()?)
+                } else {
+                    None
+                }
+            },
+        })
+    }
+
+    #[cfg(feature = "full")]
+    fn expr_closure(input: ParseStream, allow_struct: AllowStruct) -> Result<ExprClosure> {
+        let asyncness: Option<Token![async]> = input.parse()?;
+        let movability: Option<Token![static]> = if asyncness.is_none() {
+            input.parse()?
+        } else {
+            None
+        };
+        let capture: Option<Token![move]> = input.parse()?;
+        let or1_token: Token![|] = input.parse()?;
+
+        let mut inputs = Punctuated::new();
+        loop {
+            if input.peek(Token![|]) {
+                break;
+            }
+            let value = closure_arg(input)?;
+            inputs.push_value(value);
+            if input.peek(Token![|]) {
+                break;
+            }
+            let punct: Token![,] = input.parse()?;
+            inputs.push_punct(punct);
+        }
+
+        let or2_token: Token![|] = input.parse()?;
+
+        let (output, body) = if input.peek(Token![->]) {
+            let arrow_token: Token![->] = input.parse()?;
+            let ty: Type = input.parse()?;
+            let body: Block = input.parse()?;
+            let output = ReturnType::Type(arrow_token, Box::new(ty));
+            let block = Expr::Block(ExprBlock {
+                attrs: Vec::new(),
+                label: None,
+                block: body,
+            });
+            (output, block)
+        } else {
+            let body = ambiguous_expr(input, allow_struct)?;
+            (ReturnType::Default, body)
+        };
+
+        Ok(ExprClosure {
+            attrs: Vec::new(),
+            asyncness,
+            movability,
+            capture,
+            or1_token,
+            inputs,
+            or2_token,
+            output,
+            body: Box::new(body),
+        })
+    }
+
+    #[cfg(feature = "full")]
+    fn expr_async(input: ParseStream) -> Result<ExprAsync> {
+        Ok(ExprAsync {
+            attrs: Vec::new(),
+            async_token: input.parse()?,
+            capture: input.parse()?,
+            block: input.parse()?,
+        })
+    }
+
+    #[cfg(feature = "full")]
+    fn closure_arg(input: ParseStream) -> Result<Pat> {
+        let attrs = input.call(Attribute::parse_outer)?;
+        let mut pat: Pat = input.parse()?;
+
+        if input.peek(Token![:]) {
+            Ok(Pat::Type(PatType {
+                attrs,
+                pat: Box::new(pat),
+                colon_token: input.parse()?,
+                ty: input.parse()?,
+            }))
+        } else {
+            match &mut pat {
+                Pat::Box(pat) => pat.attrs = attrs,
+                Pat::Ident(pat) => pat.attrs = attrs,
+                Pat::Lit(pat) => pat.attrs = attrs,
+                Pat::Macro(pat) => pat.attrs = attrs,
+                Pat::Or(pat) => pat.attrs = attrs,
+                Pat::Path(pat) => pat.attrs = attrs,
+                Pat::Range(pat) => pat.attrs = attrs,
+                Pat::Reference(pat) => pat.attrs = attrs,
+                Pat::Rest(pat) => pat.attrs = attrs,
+                Pat::Slice(pat) => pat.attrs = attrs,
+                Pat::Struct(pat) => pat.attrs = attrs,
+                Pat::Tuple(pat) => pat.attrs = attrs,
+                Pat::TupleStruct(pat) => pat.attrs = attrs,
+                Pat::Type(_) => unreachable!(),
+                Pat::Verbatim(_) => {}
+                Pat::Wild(pat) => pat.attrs = attrs,
+                Pat::__Nonexhaustive => unreachable!(),
+            }
+            Ok(pat)
+        }
+    }
+
+    #[cfg(feature = "full")]
+    impl Parse for ExprWhile {
+        fn parse(input: ParseStream) -> Result<Self> {
+            let label: Option<Label> = input.parse()?;
+            let while_token: Token![while] = input.parse()?;
+            let cond = expr_no_struct(input)?;
+
+            let content;
+            let brace_token = braced!(content in input);
+            let inner_attrs = content.call(Attribute::parse_inner)?;
+            let stmts = content.call(Block::parse_within)?;
+
+            Ok(ExprWhile {
+                attrs: inner_attrs,
+                label,
+                while_token,
+                cond: Box::new(cond),
+                body: Block { brace_token, stmts },
+            })
+        }
+    }
+
+    #[cfg(feature = "full")]
+    impl Parse for Label {
+        fn parse(input: ParseStream) -> Result<Self> {
+            Ok(Label {
+                name: input.parse()?,
+                colon_token: input.parse()?,
+            })
+        }
+    }
+
+    #[cfg(feature = "full")]
+    impl Parse for Option<Label> {
+        fn parse(input: ParseStream) -> Result<Self> {
+            if input.peek(Lifetime) {
+                input.parse().map(Some)
+            } else {
+                Ok(None)
+            }
+        }
+    }
+
+    #[cfg(feature = "full")]
+    fn expr_continue(input: ParseStream) -> Result<ExprContinue> {
+        Ok(ExprContinue {
+            attrs: Vec::new(),
+            continue_token: input.parse()?,
+            label: input.parse()?,
+        })
+    }
+
+    #[cfg(feature = "full")]
+    fn expr_break(input: ParseStream, allow_struct: AllowStruct) -> Result<ExprBreak> {
+        Ok(ExprBreak {
+            attrs: Vec::new(),
+            break_token: input.parse()?,
+            label: input.parse()?,
+            expr: {
+                if input.is_empty()
+                    || input.peek(Token![,])
+                    || input.peek(Token![;])
+                    || !allow_struct.0 && input.peek(token::Brace)
+                {
+                    None
+                } else {
+                    let expr = ambiguous_expr(input, allow_struct)?;
+                    Some(Box::new(expr))
+                }
+            },
+        })
+    }
+
+    #[cfg(feature = "full")]
+    fn expr_ret(input: ParseStream, allow_struct: AllowStruct) -> Result<ExprReturn> {
+        Ok(ExprReturn {
+            attrs: Vec::new(),
+            return_token: input.parse()?,
+            expr: {
+                if input.is_empty() || input.peek(Token![,]) || input.peek(Token![;]) {
+                    None
+                } else {
+                    // NOTE: return is greedy and eats blocks after it even when in a
+                    // position where structs are not allowed, such as in if statement
+                    // conditions. For example:
+                    //
+                    // if return { println!("A") } {} // Prints "A"
+                    let expr = ambiguous_expr(input, allow_struct)?;
+                    Some(Box::new(expr))
+                }
+            },
+        })
+    }
+
+    #[cfg(feature = "full")]
+    impl Parse for FieldValue {
+        fn parse(input: ParseStream) -> Result<Self> {
+            let attrs = input.call(Attribute::parse_outer)?;
+            let member: Member = input.parse()?;
+            let (colon_token, value) = if input.peek(Token![:]) || !member.is_named() {
+                let colon_token: Token![:] = input.parse()?;
+                let value: Expr = input.parse()?;
+                (Some(colon_token), value)
+            } else if let Member::Named(ident) = &member {
+                let value = Expr::Path(ExprPath {
+                    attrs: Vec::new(),
+                    qself: None,
+                    path: Path::from(ident.clone()),
+                });
+                (None, value)
+            } else {
+                unreachable!()
+            };
+
+            Ok(FieldValue {
+                attrs,
+                member,
+                colon_token,
+                expr: value,
+            })
+        }
+    }
+
+    #[cfg(feature = "full")]
+    fn expr_struct_helper(
+        input: ParseStream,
+        outer_attrs: Vec<Attribute>,
+        path: Path,
+    ) -> Result<ExprStruct> {
+        let content;
+        let brace_token = braced!(content in input);
+        let inner_attrs = content.call(Attribute::parse_inner)?;
+        let attrs = private::attrs(outer_attrs, inner_attrs);
+
+        let mut fields = Punctuated::new();
+        while !content.is_empty() {
+            if content.peek(Token![..]) {
+                return Ok(ExprStruct {
+                    attrs,
+                    brace_token,
+                    path,
+                    fields,
+                    dot2_token: Some(content.parse()?),
+                    rest: Some(Box::new(content.parse()?)),
+                });
+            }
+
+            fields.push(content.parse()?);
+            if !content.peek(Token![,]) {
+                break;
+            }
+            let punct: Token![,] = content.parse()?;
+            fields.push_punct(punct);
+        }
+
+        Ok(ExprStruct {
+            attrs,
+            brace_token,
+            path,
+            fields,
+            dot2_token: None,
+            rest: None,
+        })
+    }
+
+    #[cfg(feature = "full")]
+    fn expr_unsafe(input: ParseStream) -> Result<ExprUnsafe> {
+        let unsafe_token: Token![unsafe] = input.parse()?;
+
+        let content;
+        let brace_token = braced!(content in input);
+        let inner_attrs = content.call(Attribute::parse_inner)?;
+        let stmts = content.call(Block::parse_within)?;
+
+        Ok(ExprUnsafe {
+            attrs: inner_attrs,
+            unsafe_token,
+            block: Block { brace_token, stmts },
+        })
+    }
+
+    #[cfg(feature = "full")]
+    pub fn expr_block(input: ParseStream) -> Result<ExprBlock> {
+        let label: Option<Label> = input.parse()?;
+
+        let content;
+        let brace_token = braced!(content in input);
+        let inner_attrs = content.call(Attribute::parse_inner)?;
+        let stmts = content.call(Block::parse_within)?;
+
+        Ok(ExprBlock {
+            attrs: inner_attrs,
+            label,
+            block: Block { brace_token, stmts },
+        })
+    }
+
+    #[cfg(feature = "full")]
+    fn expr_range(input: ParseStream, allow_struct: AllowStruct) -> Result<ExprRange> {
+        Ok(ExprRange {
+            attrs: Vec::new(),
+            from: None,
+            limits: input.parse()?,
+            to: {
+                if input.is_empty()
+                    || input.peek(Token![,])
+                    || input.peek(Token![;])
+                    || !allow_struct.0 && input.peek(token::Brace)
+                {
+                    None
+                } else {
+                    let to = ambiguous_expr(input, allow_struct)?;
+                    Some(Box::new(to))
+                }
+            },
+        })
+    }
+
+    #[cfg(feature = "full")]
+    impl Parse for RangeLimits {
+        fn parse(input: ParseStream) -> Result<Self> {
+            let lookahead = input.lookahead1();
+            if lookahead.peek(Token![..=]) {
+                input.parse().map(RangeLimits::Closed)
+            } else if lookahead.peek(Token![...]) {
+                let dot3: Token![...] = input.parse()?;
+                Ok(RangeLimits::Closed(Token![..=](dot3.spans)))
+            } else if lookahead.peek(Token![..]) {
+                input.parse().map(RangeLimits::HalfOpen)
+            } else {
+                Err(lookahead.error())
+            }
+        }
+    }
+
+    impl Parse for ExprPath {
+        fn parse(input: ParseStream) -> Result<Self> {
+            #[cfg(not(feature = "full"))]
+            let attrs = Vec::new();
+            #[cfg(feature = "full")]
+            let attrs = input.call(Attribute::parse_outer)?;
+
+            let (qself, path) = path::parsing::qpath(input, true)?;
+
+            Ok(ExprPath { attrs, qself, path })
+        }
+    }
+
+    impl Parse for Member {
+        fn parse(input: ParseStream) -> Result<Self> {
+            if input.peek(Ident) {
+                input.parse().map(Member::Named)
+            } else if input.peek(LitInt) {
+                input.parse().map(Member::Unnamed)
+            } else {
+                Err(input.error("expected identifier or integer"))
+            }
+        }
+    }
+
+    #[cfg(feature = "full")]
+    impl Parse for Arm {
+        fn parse(input: ParseStream) -> Result<Arm> {
+            let requires_comma;
+            Ok(Arm {
+                attrs: input.call(Attribute::parse_outer)?,
+                pat: {
+                    let leading_vert: Option<Token![|]> = input.parse()?;
+                    let pat: Pat = input.parse()?;
+                    if leading_vert.is_some() || input.peek(Token![|]) {
+                        let mut cases = Punctuated::new();
+                        cases.push_value(pat);
+                        while input.peek(Token![|]) {
+                            let punct = input.parse()?;
+                            cases.push_punct(punct);
+                            let pat: Pat = input.parse()?;
+                            cases.push_value(pat);
+                        }
+                        Pat::Or(PatOr {
+                            attrs: Vec::new(),
+                            leading_vert,
+                            cases,
+                        })
+                    } else {
+                        pat
+                    }
+                },
+                guard: {
+                    if input.peek(Token![if]) {
+                        let if_token: Token![if] = input.parse()?;
+                        let guard: Expr = input.parse()?;
+                        Some((if_token, Box::new(guard)))
+                    } else {
+                        None
+                    }
+                },
+                fat_arrow_token: input.parse()?,
+                body: {
+                    let body = input.call(expr_early)?;
+                    requires_comma = requires_terminator(&body);
+                    Box::new(body)
+                },
+                comma: {
+                    if requires_comma && !input.is_empty() {
+                        Some(input.parse()?)
+                    } else {
+                        input.parse()?
+                    }
+                },
+            })
+        }
+    }
+
+    impl Parse for Index {
+        fn parse(input: ParseStream) -> Result<Self> {
+            let lit: LitInt = input.parse()?;
+            if lit.suffix().is_empty() {
+                Ok(Index {
+                    index: lit
+                        .base10_digits()
+                        .parse()
+                        .map_err(|err| Error::new(lit.span(), err))?,
+                    span: lit.span(),
+                })
+            } else {
+                Err(Error::new(lit.span(), "expected unsuffixed integer"))
+            }
+        }
+    }
+
+    #[cfg(feature = "full")]
+    impl Member {
+        fn is_named(&self) -> bool {
+            match *self {
+                Member::Named(_) => true,
+                Member::Unnamed(_) => false,
+            }
+        }
+    }
+}
+
+#[cfg(feature = "printing")]
+pub(crate) mod printing {
+    use super::*;
+
+    use proc_macro2::{Literal, TokenStream};
+    use quote::{ToTokens, TokenStreamExt};
+
+    #[cfg(feature = "full")]
+    use crate::attr::FilterAttrs;
+    #[cfg(feature = "full")]
+    use crate::print::TokensOrDefault;
+
+    // If the given expression is a bare `ExprStruct`, wraps it in parenthesis
+    // before appending it to `TokenStream`.
+    #[cfg(feature = "full")]
+    fn wrap_bare_struct(tokens: &mut TokenStream, e: &Expr) {
+        if let Expr::Struct(_) = *e {
+            token::Paren::default().surround(tokens, |tokens| {
+                e.to_tokens(tokens);
+            });
+        } else {
+            e.to_tokens(tokens);
+        }
+    }
+
+    #[cfg(feature = "full")]
+    pub(crate) fn outer_attrs_to_tokens(attrs: &[Attribute], tokens: &mut TokenStream) {
+        tokens.append_all(attrs.outer());
+    }
+
+    #[cfg(feature = "full")]
+    fn inner_attrs_to_tokens(attrs: &[Attribute], tokens: &mut TokenStream) {
+        tokens.append_all(attrs.inner());
+    }
+
+    #[cfg(not(feature = "full"))]
+    pub(crate) fn outer_attrs_to_tokens(_attrs: &[Attribute], _tokens: &mut TokenStream) {}
+
+    #[cfg(not(feature = "full"))]
+    fn inner_attrs_to_tokens(_attrs: &[Attribute], _tokens: &mut TokenStream) {}
+
+    #[cfg(feature = "full")]
+    impl ToTokens for ExprBox {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            outer_attrs_to_tokens(&self.attrs, tokens);
+            self.box_token.to_tokens(tokens);
+            self.expr.to_tokens(tokens);
+        }
+    }
+
+    #[cfg(feature = "full")]
+    impl ToTokens for ExprArray {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            outer_attrs_to_tokens(&self.attrs, tokens);
+            self.bracket_token.surround(tokens, |tokens| {
+                inner_attrs_to_tokens(&self.attrs, tokens);
+                self.elems.to_tokens(tokens);
+            })
+        }
+    }
+
+    impl ToTokens for ExprCall {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            outer_attrs_to_tokens(&self.attrs, tokens);
+            self.func.to_tokens(tokens);
+            self.paren_token.surround(tokens, |tokens| {
+                self.args.to_tokens(tokens);
+            })
+        }
+    }
+
+    #[cfg(feature = "full")]
+    impl ToTokens for ExprMethodCall {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            outer_attrs_to_tokens(&self.attrs, tokens);
+            self.receiver.to_tokens(tokens);
+            self.dot_token.to_tokens(tokens);
+            self.method.to_tokens(tokens);
+            self.turbofish.to_tokens(tokens);
+            self.paren_token.surround(tokens, |tokens| {
+                self.args.to_tokens(tokens);
+            });
+        }
+    }
+
+    #[cfg(feature = "full")]
+    impl ToTokens for MethodTurbofish {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            self.colon2_token.to_tokens(tokens);
+            self.lt_token.to_tokens(tokens);
+            self.args.to_tokens(tokens);
+            self.gt_token.to_tokens(tokens);
+        }
+    }
+
+    #[cfg(feature = "full")]
+    impl ToTokens for GenericMethodArgument {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            match self {
+                GenericMethodArgument::Type(t) => t.to_tokens(tokens),
+                GenericMethodArgument::Const(c) => c.to_tokens(tokens),
+            }
+        }
+    }
+
+    #[cfg(feature = "full")]
+    impl ToTokens for ExprTuple {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            outer_attrs_to_tokens(&self.attrs, tokens);
+            self.paren_token.surround(tokens, |tokens| {
+                inner_attrs_to_tokens(&self.attrs, tokens);
+                self.elems.to_tokens(tokens);
+                // If we only have one argument, we need a trailing comma to
+                // distinguish ExprTuple from ExprParen.
+                if self.elems.len() == 1 && !self.elems.trailing_punct() {
+                    <Token![,]>::default().to_tokens(tokens);
+                }
+            })
+        }
+    }
+
+    impl ToTokens for ExprBinary {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            outer_attrs_to_tokens(&self.attrs, tokens);
+            self.left.to_tokens(tokens);
+            self.op.to_tokens(tokens);
+            self.right.to_tokens(tokens);
+        }
+    }
+
+    impl ToTokens for ExprUnary {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            outer_attrs_to_tokens(&self.attrs, tokens);
+            self.op.to_tokens(tokens);
+            self.expr.to_tokens(tokens);
+        }
+    }
+
+    impl ToTokens for ExprLit {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            outer_attrs_to_tokens(&self.attrs, tokens);
+            self.lit.to_tokens(tokens);
+        }
+    }
+
+    impl ToTokens for ExprCast {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            outer_attrs_to_tokens(&self.attrs, tokens);
+            self.expr.to_tokens(tokens);
+            self.as_token.to_tokens(tokens);
+            self.ty.to_tokens(tokens);
+        }
+    }
+
+    #[cfg(feature = "full")]
+    impl ToTokens for ExprType {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            outer_attrs_to_tokens(&self.attrs, tokens);
+            self.expr.to_tokens(tokens);
+            self.colon_token.to_tokens(tokens);
+            self.ty.to_tokens(tokens);
+        }
+    }
+
+    #[cfg(feature = "full")]
+    fn maybe_wrap_else(tokens: &mut TokenStream, else_: &Option<(Token![else], Box<Expr>)>) {
+        if let Some((else_token, else_)) = else_ {
+            else_token.to_tokens(tokens);
+
+            // If we are not one of the valid expressions to exist in an else
+            // clause, wrap ourselves in a block.
+            match **else_ {
+                Expr::If(_) | Expr::Block(_) => {
+                    else_.to_tokens(tokens);
+                }
+                _ => {
+                    token::Brace::default().surround(tokens, |tokens| {
+                        else_.to_tokens(tokens);
+                    });
+                }
+            }
+        }
+    }
+
+    #[cfg(feature = "full")]
+    impl ToTokens for ExprLet {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            outer_attrs_to_tokens(&self.attrs, tokens);
+            self.let_token.to_tokens(tokens);
+            self.pat.to_tokens(tokens);
+            self.eq_token.to_tokens(tokens);
+            wrap_bare_struct(tokens, &self.expr);
+        }
+    }
+
+    #[cfg(feature = "full")]
+    impl ToTokens for ExprIf {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            outer_attrs_to_tokens(&self.attrs, tokens);
+            self.if_token.to_tokens(tokens);
+            wrap_bare_struct(tokens, &self.cond);
+            self.then_branch.to_tokens(tokens);
+            maybe_wrap_else(tokens, &self.else_branch);
+        }
+    }
+
+    #[cfg(feature = "full")]
+    impl ToTokens for ExprWhile {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            outer_attrs_to_tokens(&self.attrs, tokens);
+            self.label.to_tokens(tokens);
+            self.while_token.to_tokens(tokens);
+            wrap_bare_struct(tokens, &self.cond);
+            self.body.brace_token.surround(tokens, |tokens| {
+                inner_attrs_to_tokens(&self.attrs, tokens);
+                tokens.append_all(&self.body.stmts);
+            });
+        }
+    }
+
+    #[cfg(feature = "full")]
+    impl ToTokens for ExprForLoop {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            outer_attrs_to_tokens(&self.attrs, tokens);
+            self.label.to_tokens(tokens);
+            self.for_token.to_tokens(tokens);
+            self.pat.to_tokens(tokens);
+            self.in_token.to_tokens(tokens);
+            wrap_bare_struct(tokens, &self.expr);
+            self.body.brace_token.surround(tokens, |tokens| {
+                inner_attrs_to_tokens(&self.attrs, tokens);
+                tokens.append_all(&self.body.stmts);
+            });
+        }
+    }
+
+    #[cfg(feature = "full")]
+    impl ToTokens for ExprLoop {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            outer_attrs_to_tokens(&self.attrs, tokens);
+            self.label.to_tokens(tokens);
+            self.loop_token.to_tokens(tokens);
+            self.body.brace_token.surround(tokens, |tokens| {
+                inner_attrs_to_tokens(&self.attrs, tokens);
+                tokens.append_all(&self.body.stmts);
+            });
+        }
+    }
+
+    #[cfg(feature = "full")]
+    impl ToTokens for ExprMatch {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            outer_attrs_to_tokens(&self.attrs, tokens);
+            self.match_token.to_tokens(tokens);
+            wrap_bare_struct(tokens, &self.expr);
+            self.brace_token.surround(tokens, |tokens| {
+                inner_attrs_to_tokens(&self.attrs, tokens);
+                for (i, arm) in self.arms.iter().enumerate() {
+                    arm.to_tokens(tokens);
+                    // Ensure that we have a comma after a non-block arm, except
+                    // for the last one.
+                    let is_last = i == self.arms.len() - 1;
+                    if !is_last && requires_terminator(&arm.body) && arm.comma.is_none() {
+                        <Token![,]>::default().to_tokens(tokens);
+                    }
+                }
+            });
+        }
+    }
+
+    #[cfg(feature = "full")]
+    impl ToTokens for ExprAsync {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            outer_attrs_to_tokens(&self.attrs, tokens);
+            self.async_token.to_tokens(tokens);
+            self.capture.to_tokens(tokens);
+            self.block.to_tokens(tokens);
+        }
+    }
+
+    #[cfg(feature = "full")]
+    impl ToTokens for ExprAwait {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            outer_attrs_to_tokens(&self.attrs, tokens);
+            self.base.to_tokens(tokens);
+            self.dot_token.to_tokens(tokens);
+            self.await_token.to_tokens(tokens);
+        }
+    }
+
+    #[cfg(feature = "full")]
+    impl ToTokens for ExprTryBlock {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            outer_attrs_to_tokens(&self.attrs, tokens);
+            self.try_token.to_tokens(tokens);
+            self.block.to_tokens(tokens);
+        }
+    }
+
+    #[cfg(feature = "full")]
+    impl ToTokens for ExprYield {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            outer_attrs_to_tokens(&self.attrs, tokens);
+            self.yield_token.to_tokens(tokens);
+            self.expr.to_tokens(tokens);
+        }
+    }
+
+    #[cfg(feature = "full")]
+    impl ToTokens for ExprClosure {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            outer_attrs_to_tokens(&self.attrs, tokens);
+            self.asyncness.to_tokens(tokens);
+            self.movability.to_tokens(tokens);
+            self.capture.to_tokens(tokens);
+            self.or1_token.to_tokens(tokens);
+            self.inputs.to_tokens(tokens);
+            self.or2_token.to_tokens(tokens);
+            self.output.to_tokens(tokens);
+            self.body.to_tokens(tokens);
+        }
+    }
+
+    #[cfg(feature = "full")]
+    impl ToTokens for ExprUnsafe {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            outer_attrs_to_tokens(&self.attrs, tokens);
+            self.unsafe_token.to_tokens(tokens);
+            self.block.brace_token.surround(tokens, |tokens| {
+                inner_attrs_to_tokens(&self.attrs, tokens);
+                tokens.append_all(&self.block.stmts);
+            });
+        }
+    }
+
+    #[cfg(feature = "full")]
+    impl ToTokens for ExprBlock {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            outer_attrs_to_tokens(&self.attrs, tokens);
+            self.label.to_tokens(tokens);
+            self.block.brace_token.surround(tokens, |tokens| {
+                inner_attrs_to_tokens(&self.attrs, tokens);
+                tokens.append_all(&self.block.stmts);
+            });
+        }
+    }
+
+    #[cfg(feature = "full")]
+    impl ToTokens for ExprAssign {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            outer_attrs_to_tokens(&self.attrs, tokens);
+            self.left.to_tokens(tokens);
+            self.eq_token.to_tokens(tokens);
+            self.right.to_tokens(tokens);
+        }
+    }
+
+    #[cfg(feature = "full")]
+    impl ToTokens for ExprAssignOp {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            outer_attrs_to_tokens(&self.attrs, tokens);
+            self.left.to_tokens(tokens);
+            self.op.to_tokens(tokens);
+            self.right.to_tokens(tokens);
+        }
+    }
+
+    impl ToTokens for ExprField {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            outer_attrs_to_tokens(&self.attrs, tokens);
+            self.base.to_tokens(tokens);
+            self.dot_token.to_tokens(tokens);
+            self.member.to_tokens(tokens);
+        }
+    }
+
+    impl ToTokens for Member {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            match self {
+                Member::Named(ident) => ident.to_tokens(tokens),
+                Member::Unnamed(index) => index.to_tokens(tokens),
+            }
+        }
+    }
+
+    impl ToTokens for Index {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            let mut lit = Literal::i64_unsuffixed(i64::from(self.index));
+            lit.set_span(self.span);
+            tokens.append(lit);
+        }
+    }
+
+    impl ToTokens for ExprIndex {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            outer_attrs_to_tokens(&self.attrs, tokens);
+            self.expr.to_tokens(tokens);
+            self.bracket_token.surround(tokens, |tokens| {
+                self.index.to_tokens(tokens);
+            });
+        }
+    }
+
+    #[cfg(feature = "full")]
+    impl ToTokens for ExprRange {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            outer_attrs_to_tokens(&self.attrs, tokens);
+            self.from.to_tokens(tokens);
+            match &self.limits {
+                RangeLimits::HalfOpen(t) => t.to_tokens(tokens),
+                RangeLimits::Closed(t) => t.to_tokens(tokens),
+            }
+            self.to.to_tokens(tokens);
+        }
+    }
+
+    impl ToTokens for ExprPath {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            outer_attrs_to_tokens(&self.attrs, tokens);
+            private::print_path(tokens, &self.qself, &self.path);
+        }
+    }
+
+    #[cfg(feature = "full")]
+    impl ToTokens for ExprReference {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            outer_attrs_to_tokens(&self.attrs, tokens);
+            self.and_token.to_tokens(tokens);
+            self.mutability.to_tokens(tokens);
+            self.expr.to_tokens(tokens);
+        }
+    }
+
+    #[cfg(feature = "full")]
+    impl ToTokens for ExprBreak {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            outer_attrs_to_tokens(&self.attrs, tokens);
+            self.break_token.to_tokens(tokens);
+            self.label.to_tokens(tokens);
+            self.expr.to_tokens(tokens);
+        }
+    }
+
+    #[cfg(feature = "full")]
+    impl ToTokens for ExprContinue {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            outer_attrs_to_tokens(&self.attrs, tokens);
+            self.continue_token.to_tokens(tokens);
+            self.label.to_tokens(tokens);
+        }
+    }
+
+    #[cfg(feature = "full")]
+    impl ToTokens for ExprReturn {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            outer_attrs_to_tokens(&self.attrs, tokens);
+            self.return_token.to_tokens(tokens);
+            self.expr.to_tokens(tokens);
+        }
+    }
+
+    #[cfg(feature = "full")]
+    impl ToTokens for ExprMacro {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            outer_attrs_to_tokens(&self.attrs, tokens);
+            self.mac.to_tokens(tokens);
+        }
+    }
+
+    #[cfg(feature = "full")]
+    impl ToTokens for ExprStruct {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            outer_attrs_to_tokens(&self.attrs, tokens);
+            self.path.to_tokens(tokens);
+            self.brace_token.surround(tokens, |tokens| {
+                inner_attrs_to_tokens(&self.attrs, tokens);
+                self.fields.to_tokens(tokens);
+                if self.rest.is_some() {
+                    TokensOrDefault(&self.dot2_token).to_tokens(tokens);
+                    self.rest.to_tokens(tokens);
+                }
+            })
+        }
+    }
+
+    #[cfg(feature = "full")]
+    impl ToTokens for ExprRepeat {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            outer_attrs_to_tokens(&self.attrs, tokens);
+            self.bracket_token.surround(tokens, |tokens| {
+                inner_attrs_to_tokens(&self.attrs, tokens);
+                self.expr.to_tokens(tokens);
+                self.semi_token.to_tokens(tokens);
+                self.len.to_tokens(tokens);
+            })
+        }
+    }
+
+    #[cfg(feature = "full")]
+    impl ToTokens for ExprGroup {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            outer_attrs_to_tokens(&self.attrs, tokens);
+            self.group_token.surround(tokens, |tokens| {
+                self.expr.to_tokens(tokens);
+            });
+        }
+    }
+
+    impl ToTokens for ExprParen {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            outer_attrs_to_tokens(&self.attrs, tokens);
+            self.paren_token.surround(tokens, |tokens| {
+                inner_attrs_to_tokens(&self.attrs, tokens);
+                self.expr.to_tokens(tokens);
+            });
+        }
+    }
+
+    #[cfg(feature = "full")]
+    impl ToTokens for ExprTry {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            outer_attrs_to_tokens(&self.attrs, tokens);
+            self.expr.to_tokens(tokens);
+            self.question_token.to_tokens(tokens);
+        }
+    }
+
+    #[cfg(feature = "full")]
+    impl ToTokens for Label {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            self.name.to_tokens(tokens);
+            self.colon_token.to_tokens(tokens);
+        }
+    }
+
+    #[cfg(feature = "full")]
+    impl ToTokens for FieldValue {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            outer_attrs_to_tokens(&self.attrs, tokens);
+            self.member.to_tokens(tokens);
+            if let Some(colon_token) = &self.colon_token {
+                colon_token.to_tokens(tokens);
+                self.expr.to_tokens(tokens);
+            }
+        }
+    }
+
+    #[cfg(feature = "full")]
+    impl ToTokens for Arm {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            tokens.append_all(&self.attrs);
+            self.pat.to_tokens(tokens);
+            if let Some((if_token, guard)) = &self.guard {
+                if_token.to_tokens(tokens);
+                guard.to_tokens(tokens);
+            }
+            self.fat_arrow_token.to_tokens(tokens);
+            self.body.to_tokens(tokens);
+            self.comma.to_tokens(tokens);
+        }
+    }
+}
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