src/expr.rs

use super::*;
use delimited::Delimited;

ast_struct! {
    /// An expression.
    pub struct Expr {
        /// Type of the expression.
        pub node: ExprKind,

        /// Attributes tagged on the expression.
        pub attrs: Vec<Attribute>,
    }
}

impl From<ExprKind> for Expr {
    fn from(node: ExprKind) -> Expr {
        Expr {
            node: node,
            attrs: Vec::new(),
        }
    }
}

ast_enum_of_structs! {
    pub enum ExprKind {
        /// A `box x` expression.
        pub Box(ExprBox {
            pub expr: Box<Expr>,
            pub box_token: tokens::Box_,
        }),

        /// E.g. 'place <- val'.
        pub InPlace(ExprInPlace {
            pub place: Box<Expr>,
            pub value: Box<Expr>,
            pub in_token: tokens::In,
        }),

        /// An array, e.g. `[a, b, c, d]`.
        pub Array(ExprArray {
            pub exprs: Delimited<Expr, tokens::Comma>,
            pub bracket_token: tokens::Bracket,
        }),

        /// A function call.
        pub Call(ExprCall {
            pub func: Box<Expr>,
            pub args: Delimited<Expr, tokens::Comma>,
            pub paren_token: tokens::Paren,
        }),

        /// A method call (`x.foo::<Bar, Baz>(a, b, c, d)`)
        ///
        /// The `Ident` is the identifier for the method name.
        /// The vector of `Ty`s are the ascripted type parameters for the method
        /// (within the angle brackets).
        ///
        /// Thus, `x.foo::<Bar, Baz>(a, b, c, d)` is represented as
        /// `ExprKind::MethodCall(foo, [Bar, Baz], [x, a, b, c, d])`.
        pub MethodCall(ExprMethodCall {
            pub expr: Box<Expr>,
            pub method: Ident,
            pub typarams: Delimited<Ty, tokens::Comma>,
            pub args: Delimited<Expr, tokens::Comma>,
            pub paren_token: tokens::Paren,
            pub dot_token: tokens::Dot,
            pub lt_token: Option<tokens::Lt>,
            pub colon2_token: Option<tokens::Colon2>,
            pub gt_token: Option<tokens::Gt>,
        }),

        /// A tuple, e.g. `(a, b, c, d)`.
        pub Tup(ExprTup {
            pub args: Delimited<Expr, tokens::Comma>,
            pub paren_token: tokens::Paren,
            pub lone_comma: Option<tokens::Comma>,
        }),

        /// A binary operation, e.g. `a + b`, `a * b`.
        pub Binary(ExprBinary {
            pub op: BinOp,
            pub left: Box<Expr>,
            pub right: Box<Expr>,
        }),

        /// A unary operation, e.g. `!x`, `*x`.
        pub Unary(ExprUnary {
            pub op: UnOp,
            pub expr: Box<Expr>,
        }),

        /// A literal, e.g. `1`, `"foo"`.
        pub Lit(Lit),

        /// A cast, e.g. `foo as f64`.
        pub Cast(ExprCast {
            pub expr: Box<Expr>,
            pub as_token: tokens::As,
            pub ty: Box<Ty>,
        }),

        /// A type ascription, e.g. `foo: f64`.
        pub Type(ExprType {
            pub expr: Box<Expr>,
            pub colon_token: tokens::Colon,
            pub ty: Box<Ty>,
        }),

        /// An `if` block, with an optional else block
        ///
        /// E.g., `if expr { block } else { expr }`
        pub If(ExprIf {
            pub cond: Box<Expr>,
            pub if_true: Block,
            pub if_false: Option<Box<Expr>>,
            pub if_token: tokens::If,
            pub else_token: Option<tokens::Else>,
        }),

        /// An `if let` expression with an optional else block
        ///
        /// E.g., `if let pat = expr { block } else { expr }`
        ///
        /// This is desugared to a `match` expression.
        pub IfLet(ExprIfLet {
            pub pat: Box<Pat>,
            pub expr: Box<Expr>,
            pub if_true: Block,
            pub if_false: Option<Box<Expr>>,
            pub if_token: tokens::If,
            pub let_token: tokens::Let,
            pub eq_token: tokens::Eq,
            pub else_token: Option<tokens::Else>,
        }),

        /// A while loop, with an optional label
        ///
        /// E.g., `'label: while expr { block }`
        pub While(ExprWhile {
            pub cond: Box<Expr>,
            pub body: Block,
            pub label: Option<Ident>,
            pub colon_token: Option<tokens::Colon>,
            pub while_token: tokens::While,
        }),

        /// A while-let loop, with an optional label.
        ///
        /// E.g., `'label: while let pat = expr { block }`
        ///
        /// This is desugared to a combination of `loop` and `match` expressions.
        pub WhileLet(ExprWhileLet {
            pub pat: Box<Pat>,
            pub expr: Box<Expr>,
            pub body: Block,
            pub label: Option<Ident>,
            pub colon_token: Option<tokens::Colon>,
            pub while_token: tokens::While,
            pub let_token: tokens::Let,
            pub eq_token: tokens::Eq,
        }),

        /// A for loop, with an optional label.
        ///
        /// E.g., `'label: for pat in expr { block }`
        ///
        /// This is desugared to a combination of `loop` and `match` expressions.
        pub ForLoop(ExprForLoop {
            pub pat: Box<Pat>,
            pub expr: Box<Expr>,
            pub body: Block,
            pub label: Option<Ident>,
            pub for_token: tokens::For,
            pub colon_token: Option<tokens::Colon>,
            pub in_token: tokens::In,
        }),

        /// Conditionless loop with an optional label.
        ///
        /// E.g. `'label: loop { block }`
        pub Loop(ExprLoop {
            pub body: Block,
            pub label: Option<Ident>,
            pub loop_token: tokens::Loop,
            pub colon_token: Option<tokens::Colon>,
        }),

        /// A `match` block.
        pub Match(ExprMatch {
            pub match_token: tokens::Match,
            pub brace_token: tokens::Brace,
            pub expr: Box<Expr>,
            pub arms: Vec<Arm>,
        }),

        /// A closure (for example, `move |a, b, c| a + b + c`)
        pub Closure(ExprClosure {
            pub capture: CaptureBy,
            pub decl: Box<FnDecl>,
            pub body: Box<Expr>,
            pub or1_token: tokens::Or,
            pub or2_token: tokens::Or,
        }),

        /// A block (`{ ... }` or `unsafe { ... }`)
        pub Block(ExprBlock {
            pub unsafety: Unsafety,
            pub block: Block,
        }),

        /// An assignment (`a = foo()`)
        pub Assign(ExprAssign {
            pub left: Box<Expr>,
            pub right: Box<Expr>,
            pub eq_token: tokens::Eq,
        }),

        /// An assignment with an operator
        ///
        /// For example, `a += 1`.
        pub AssignOp(ExprAssignOp {
            pub op: BinOp,
            pub left: Box<Expr>,
            pub right: Box<Expr>,
        }),

        /// Access of a named struct field (`obj.foo`)
        pub Field(ExprField {
            pub expr: Box<Expr>,
            pub field: Ident,
            pub dot_token: tokens::Dot,
        }),

        /// Access of an unnamed field of a struct or tuple-struct
        ///
        /// For example, `foo.0`.
        pub TupField(ExprTupField {
            pub expr: Box<Expr>,
            pub field: Lit,
            pub dot_token: tokens::Dot,
        }),

        /// An indexing operation (`foo[2]`)
        pub Index(ExprIndex {
            pub expr: Box<Expr>,
            pub index: Box<Expr>,
            pub bracket_token: tokens::Bracket,
        }),

        /// A range (`1..2`, `1..`, `..2`, `1...2`, `1...`, `...2`)
        pub Range(ExprRange {
            pub from: Option<Box<Expr>>,
            pub to: Option<Box<Expr>>,
            pub limits: RangeLimits,
        }),

        /// Variable reference, possibly containing `::` and/or type
        /// parameters, e.g. foo::bar::<baz>.
        ///
        /// Optionally "qualified",
        /// E.g. `<Vec<T> as SomeTrait>::SomeType`.
        pub Path(ExprPath {
            pub qself: Option<QSelf>,
            pub path: Path,
        }),

        /// A referencing operation (`&a` or `&mut a`)
        pub AddrOf(ExprAddrOf {
            pub and_token: tokens::And,
            pub mutbl: Mutability,
            pub expr: Box<Expr>,
        }),

        /// A `break`, with an optional label to break, and an optional expression
        pub Break(ExprBreak {
            pub label: Option<Ident>,
            pub expr: Option<Box<Expr>>,
            pub break_token: tokens::Break,
        }),

        /// A `continue`, with an optional label
        pub Continue(ExprContinue {
            pub label: Option<Ident>,
            pub continue_token: tokens::Continue,
        }),

        /// A `return`, with an optional value to be returned
        pub Ret(ExprRet {
            pub expr: Option<Box<Expr>>,
            pub return_token: tokens::Return,
        }),

        /// A macro invocation; pre-expansion
        pub Mac(Mac),

        /// A struct literal expression.
        ///
        /// For example, `Foo {x: 1, y: 2}`, or
        /// `Foo {x: 1, .. base}`, where `base` is the `Option<Expr>`.
        pub Struct(ExprStruct {
            pub path: Path,
            pub fields: Delimited<FieldValue, tokens::Comma>,
            pub rest: Option<Box<Expr>>,
            pub dot2_token: Option<tokens::Dot2>,
            pub brace_token: tokens::Brace,
        }),

        /// An array literal constructed from one repeated element.
        ///
        /// For example, `[1; 5]`. The first expression is the element
        /// to be repeated; the second is the number of times to repeat it.
        pub Repeat(ExprRepeat {
            pub bracket_token: tokens::Bracket,
            pub semi_token: tokens::Semi,
            pub expr: Box<Expr>,
            pub amt: Box<Expr>,
        }),

        /// No-op: used solely so we can pretty-print faithfully
        pub Paren(ExprParen {
            pub expr: Box<Expr>,
            pub paren_token: tokens::Paren,
        }),

        /// `expr?`
        pub Try(ExprTry {
            pub expr: Box<Expr>,
            pub question_token: tokens::Question,
        }),

        /// A catch expression.
        ///
        /// E.g. `do catch { block }`
        pub Catch(ExprCatch {
            pub do_token: tokens::Do,
            pub catch_token: tokens::Catch,
            pub block: Block,
        }),
    }
}

ast_struct! {
    /// A field-value pair in a struct literal.
    pub struct FieldValue {
        /// Name of the field.
        pub ident: Ident,

        /// Value of the field.
        pub expr: Expr,

        /// Whether this is a shorthand field, e.g. `Struct { x }`
        /// instead of `Struct { x: x }`.
        pub is_shorthand: bool,

        /// Attributes tagged on the field.
        pub attrs: Vec<Attribute>,

        pub colon_token: Option<tokens::Colon>,
    }
}

ast_struct! {
    /// A Block (`{ .. }`).
    ///
    /// E.g. `{ .. }` as in `fn foo() { .. }`
    pub struct Block {
        pub brace_token: tokens::Brace,
        /// Statements in a block
        pub stmts: Vec<Stmt>,
    }
}

ast_enum! {
    /// A statement, usually ending in a semicolon.
    pub enum Stmt {
        /// A local (let) binding.
        Local(Box<Local>),

        /// An item definition.
        Item(Box<Item>),

        /// Expr without trailing semicolon.
        Expr(Box<Expr>),

        /// Expression with trailing semicolon;
        Semi(Box<Expr>, tokens::Semi),

        /// Macro invocation.
        Mac(Box<(Mac, MacStmtStyle, Vec<Attribute>)>),
    }
}

ast_enum! {
    /// How a macro was invoked.
    #[cfg_attr(feature = "clone-impls", derive(Copy))]
    pub enum MacStmtStyle {
        /// The macro statement had a trailing semicolon, e.g. `foo! { ... };`
        /// `foo!(...);`, `foo![...];`
        Semicolon(tokens::Semi),

        /// The macro statement had braces; e.g. foo! { ... }
        Braces,

        /// The macro statement had parentheses or brackets and no semicolon; e.g.
        /// `foo!(...)`. All of these will end up being converted into macro
        /// expressions.
        NoBraces,
    }
}

ast_struct! {
    /// Local represents a `let` statement, e.g., `let <pat>:<ty> = <expr>;`
    pub struct Local {
        pub let_token: tokens::Let,
        pub colon_token: Option<tokens::Colon>,
        pub eq_token: Option<tokens::Eq>,
        pub semi_token: tokens::Semi,

        pub pat: Box<Pat>,
        pub ty: Option<Box<Ty>>,

        /// Initializer expression to set the value, if any
        pub init: Option<Box<Expr>>,
        pub attrs: Vec<Attribute>,
    }
}

ast_enum_of_structs! {
    // Clippy false positive
    // https://github.com/Manishearth/rust-clippy/issues/1241
    #[cfg_attr(feature = "cargo-clippy", allow(enum_variant_names))]
    pub enum Pat {
        /// Represents a wildcard pattern (`_`)
        pub Wild(PatWild {
            pub underscore_token: tokens::Underscore,
        }),

        /// A `Pat::Ident` may either be a new bound variable (`ref mut binding @ OPT_SUBPATTERN`),
        /// or a unit struct/variant pattern, or a const pattern (in the last two cases the third
        /// field must be `None`). Disambiguation cannot be done with parser alone, so it happens
        /// during name resolution.
        pub Ident(PatIdent {
            pub mode: BindingMode,
            pub ident: Ident,
            pub subpat: Option<Box<Pat>>,
            pub at_token: Option<tokens::At>,
        }),

        /// A struct or struct variant pattern, e.g. `Variant {x, y, ..}`.
        /// The `bool` is `true` in the presence of a `..`.
        pub Struct(PatStruct {
            pub path: Path,
            pub fields: Delimited<FieldPat, tokens::Comma>,
            pub brace_token: tokens::Brace,
            pub dot2_token: Option<tokens::Dot2>,
        }),

        /// A tuple struct/variant pattern `Variant(x, y, .., z)`.
        /// If the `..` pattern fragment is present, then `Option<usize>` denotes its position.
        /// 0 <= position <= subpats.len()
        pub TupleStruct(PatTupleStruct {
            pub path: Path,
            pub pat: PatTuple,
        }),

        /// A possibly qualified path pattern.
        /// Unquailfied path patterns `A::B::C` can legally refer to variants, structs, constants
        /// or associated constants. Quailfied path patterns `<A>::B::C`/`<A as Trait>::B::C` can
        /// only legally refer to associated constants.
        pub Path(PatPath {
            pub qself: Option<QSelf>,
            pub path: Path,
        }),

        /// A tuple pattern `(a, b)`.
        /// If the `..` pattern fragment is present, then `Option<usize>` denotes its position.
        /// 0 <= position <= subpats.len()
        pub Tuple(PatTuple {
            pub pats: Delimited<Pat, tokens::Comma>,
            pub dots_pos: Option<usize>,
            pub paren_token: tokens::Paren,
            pub dot2_token: Option<tokens::Dot2>,
            pub comma_token: Option<tokens::Comma>,
        }),
        /// A `box` pattern
        pub Box(PatBox {
            pub pat: Box<Pat>,
            pub box_token: tokens::Box_,
        }),
        /// A reference pattern, e.g. `&mut (a, b)`
        pub Ref(PatRef {
            pub pat: Box<Pat>,
            pub mutbl: Mutability,
            pub and_token: tokens::And,
        }),
        /// A literal
        pub Lit(PatLit {
            pub expr: Box<Expr>,
        }),
        /// A range pattern, e.g. `1...2`
        pub Range(PatRange {
            pub lo: Box<Expr>,
            pub hi: Box<Expr>,
            pub limits: RangeLimits,
        }),
        /// `[a, b, ..i, y, z]` is represented as:
        pub Slice(PatSlice {
            pub front: Delimited<Pat, tokens::Comma>,
            pub middle: Option<Box<Pat>>,
            pub back: Delimited<Pat, tokens::Comma>,
            pub dot2_token: Option<tokens::Dot2>,
            pub comma_token: Option<tokens::Comma>,
            pub bracket_token: tokens::Bracket,
        }),
        /// A macro pattern; pre-expansion
        pub Mac(Mac),
    }
}

ast_struct! {
    /// An arm of a 'match'.
    ///
    /// E.g. `0...10 => { println!("match!") }` as in
    ///
    /// ```rust,ignore
    /// match n {
    ///     0...10 => { println!("match!") },
    ///     // ..
    /// }
    /// ```
    pub struct Arm {
        pub attrs: Vec<Attribute>,
        pub pats: Delimited<Pat, tokens::Or>,
        pub if_token: Option<tokens::If>,
        pub guard: Option<Box<Expr>>,
        pub rocket_token: tokens::Rocket,
        pub body: Box<Expr>,
        pub comma: Option<tokens::Comma>,
    }
}

ast_enum! {
    /// A capture clause
    #[cfg_attr(feature = "clone-impls", derive(Copy))]
    pub enum CaptureBy {
        Value(tokens::Move),
        Ref,
    }
}

ast_enum! {
    /// Limit types of a range (inclusive or exclusive)
    #[cfg_attr(feature = "clone-impls", derive(Copy))]
    pub enum RangeLimits {
        /// Inclusive at the beginning, exclusive at the end
        HalfOpen(tokens::Dot2),
        /// Inclusive at the beginning and end
        Closed(tokens::Dot3),
    }
}

ast_struct! {
    /// A single field in a struct pattern
    ///
    /// Patterns like the fields of Foo `{ x, ref y, ref mut z }`
    /// are treated the same as `x: x, y: ref y, z: ref mut z`,
    /// except `is_shorthand` is true
    pub struct FieldPat {
        /// The identifier for the field
        pub ident: Ident,
        /// The pattern the field is destructured to
        pub pat: Box<Pat>,
        pub is_shorthand: bool,
        pub colon_token: Option<tokens::Colon>,
        pub attrs: Vec<Attribute>,
    }
}

ast_enum! {
    #[cfg_attr(feature = "clone-impls", derive(Copy))]
    pub enum BindingMode {
        ByRef(tokens::Ref, Mutability),
        ByValue(Mutability),
    }
}

#[cfg(feature = "parsing")]
pub mod parsing {
    use super::*;
    use ty::parsing::qpath;

    use proc_macro2::{TokenStream, TokenKind, Delimiter};
    use synom::{PResult, Cursor, Synom, parse_error};
    use synom::tokens::*;

    // Struct literals are ambiguous in certain positions
    // https://github.com/rust-lang/rfcs/pull/92
    macro_rules! named_ambiguous_expr {
        ($name:ident -> $o:ty, $allow_struct:ident, $submac:ident!( $($args:tt)* )) => {
            fn $name(i: $crate::synom::Cursor, $allow_struct: bool)
                     -> $crate::synom::PResult<$o> {
                $submac!(i, $($args)*)
            }
        };
    }

    macro_rules! ambiguous_expr {
        ($i:expr, $allow_struct:ident) => {
            ambiguous_expr($i, $allow_struct, true)
        };
    }

    impl Synom for Expr {
        named!(parse -> Self, ambiguous_expr!(true));

        fn description() -> Option<&'static str> {
            Some("expression")
        }
    }


    named!(expr_no_struct -> Expr, ambiguous_expr!(false));

    #[cfg_attr(feature = "cargo-clippy", allow(cyclomatic_complexity))]
    fn ambiguous_expr(i: Cursor,
                      allow_struct: bool,
                      allow_block: bool)
                      -> PResult<Expr> {
        do_parse! {
            i,
            mut e: alt!(
                syn!(Lit) => { ExprKind::Lit } // must be before expr_struct
                |
                // must be before expr_path
                cond_reduce!(allow_struct, map!(syn!(ExprStruct), ExprKind::Struct))
                |
                syn!(ExprParen) => { ExprKind::Paren } // must be before expr_tup
                |
                syn!(Mac) => { ExprKind::Mac } // must be before expr_path
                |
                call!(expr_break, allow_struct) // must be before expr_path
                |
                syn!(ExprContinue) => { ExprKind::Continue } // must be before expr_path
                |
                call!(expr_ret, allow_struct) // must be before expr_path
                |
                call!(expr_box, allow_struct)
                |
                syn!(ExprInPlace) => { ExprKind::InPlace }
                |
                syn!(ExprArray) => { ExprKind::Array }
                |
                syn!(ExprTup) => { ExprKind::Tup }
                |
                call!(expr_unary, allow_struct)
                |
                syn!(ExprIf) => { ExprKind::If }
                |
                syn!(ExprIfLet) => { ExprKind::IfLet }
                |
                syn!(ExprWhile) => { ExprKind::While }
                |
                syn!(ExprWhileLet) => { ExprKind::WhileLet }
                |
                syn!(ExprForLoop) => { ExprKind::ForLoop }
                |
                syn!(ExprLoop) => { ExprKind::Loop }
                |
                syn!(ExprMatch) => { ExprKind::Match }
                |
                syn!(ExprCatch) => { ExprKind::Catch }
                |
                call!(expr_closure, allow_struct)
                |
                cond_reduce!(allow_block, map!(syn!(ExprBlock), ExprKind::Block))
                |
                call!(expr_range, allow_struct)
                |
                syn!(ExprPath) => { ExprKind::Path }
                |
                call!(expr_addr_of, allow_struct)
                |
                syn!(ExprRepeat) => { ExprKind::Repeat }
            ) >>
            many0!(alt!(
                tap!(args: and_call => {
                    let (args, paren) = args;
                    e = ExprCall {
                        func: Box::new(e.into()),
                        args: args,
                        paren_token: paren,
                    }.into();
                })
                |
                tap!(more: and_method_call => {
                    let mut call = more;
                    call.expr = Box::new(e.into());
                    e = call.into();
                })
                |
                tap!(more: call!(and_binary, allow_struct) => {
                    let (op, other) = more;
                    e = ExprBinary {
                        op: op,
                        left: Box::new(e.into()),
                        right: Box::new(other),
                    }.into();
                })
                |
                tap!(ty: and_cast => {
                    let (ty, token) = ty;
                    e = ExprCast {
                        expr: Box::new(e.into()),
                        ty: Box::new(ty),
                        as_token: token,
                    }.into();
                })
                |
                tap!(ty: and_ascription => {
                    let (ty, token) = ty;
                    e = ExprType {
                        expr: Box::new(e.into()),
                        ty: Box::new(ty),
                        colon_token: token,
                    }.into();
                })
                |
                tap!(v: call!(and_assign, allow_struct) => {
                    let (v, token) = v;
                    e = ExprAssign {
                        left: Box::new(e.into()),
                        eq_token: token,
                        right: Box::new(v),
                    }.into();
                })
                |
                tap!(more: call!(and_assign_op, allow_struct) => {
                    let (op, v) = more;
                    e = ExprAssignOp {
                        op: op,
                        left: Box::new(e.into()),
                        right: Box::new(v),
                    }.into();
                })
                |
                tap!(field: and_field => {
                    let (field, token) = field;
                    e = ExprField {
                        expr: Box::new(e.into()),
                        field: field,
                        dot_token: token,
                    }.into();
                })
                |
                tap!(field: and_tup_field => {
                    let (field, token) = field;
                    e = ExprTupField {
                        expr: Box::new(e.into()),
                        field: field,
                        dot_token: token,
                    }.into();
                })
                |
                tap!(i: and_index => {
                    let (i, token) = i;
                    e = ExprIndex {
                        expr: Box::new(e.into()),
                        bracket_token: token,
                        index: Box::new(i),
                    }.into();
                })
                |
                tap!(more: call!(and_range, allow_struct) => {
                    let (limits, hi) = more;
                    e = ExprRange {
                        from: Some(Box::new(e.into())),
                        to: hi.map(Box::new),
                        limits: limits,
                    }.into();
                })
                |
                tap!(question: syn!(Question) => {
                    e = ExprTry {
                        expr: Box::new(e.into()),
                        question_token: question,
                    }.into();
                })
            )) >>
            (e.into())
        }
    }

    impl Synom for ExprParen {
        named!(parse -> Self, do_parse!(
            e: parens!(syn!(Expr)) >>
            (ExprParen {
                expr: Box::new(e.0),
                paren_token: e.1,
            }.into())
        ));
    }

    named_ambiguous_expr!(expr_box -> ExprKind, allow_struct, do_parse!(
        box_: syn!(Box_) >>
        inner: ambiguous_expr!(allow_struct) >>
        (ExprBox {
            expr: Box::new(inner),
            box_token: box_,
        }.into())
    ));

    impl Synom for ExprInPlace {
        named!(parse -> Self, do_parse!(
            in_: syn!(In) >>
            place: expr_no_struct >>
            value: braces!(call!(Block::parse_within)) >>
            (ExprInPlace {
                in_token: in_,
                place: Box::new(place),
                value: Box::new(Expr {
                    node: ExprBlock {
                        unsafety: Unsafety::Normal,
                        block: Block {
                            stmts: value.0,
                            brace_token: value.1,
                        },
                    }.into(),
                    attrs: Vec::new(),
                }),
            })
        ));
    }

    impl Synom for ExprArray {
        named!(parse -> Self, do_parse!(
            elems: brackets!(call!(Delimited::parse_terminated)) >>
            (ExprArray {
                exprs: elems.0,
                bracket_token: elems.1,
            })
        ));
    }

    named!(and_call -> (Delimited<Expr, tokens::Comma>, tokens::Paren),
           parens!(call!(Delimited::parse_terminated)));

    named!(and_method_call -> ExprMethodCall, do_parse!(
        dot: syn!(Dot) >>
        method: syn!(Ident) >>
        typarams: option!(do_parse!(
            colon2: syn!(Colon2) >>
            lt: syn!(Lt) >>
            tys: call!(Delimited::parse_terminated) >>
            gt: syn!(Gt) >>
            (colon2, lt, tys, gt)
        )) >>
        args: parens!(call!(Delimited::parse_terminated)) >>
        ({
            let (colon2, lt, tys, gt) = match typarams {
                Some((a, b, c, d)) => (Some(a), Some(b), Some(c), Some(d)),
                None => (None, None, None, None),
            };
            ExprMethodCall {
                // this expr will get overwritten after being returned
                expr: Box::new(ExprKind::Lit(Lit {
                    span: Span::default(),
                    value: LitKind::Bool(false),
                }).into()),

                method: method,
                args: args.0,
                paren_token: args.1,
                dot_token: dot,
                lt_token: lt,
                gt_token: gt,
                colon2_token: colon2,
                typarams: tys.unwrap_or_default(),
            }
        })
    ));

    impl Synom for ExprTup {
        named!(parse -> Self, do_parse!(
            elems: parens!(call!(Delimited::parse_terminated)) >>
            (ExprTup {
                args: elems.0,
                paren_token: elems.1,
                lone_comma: None, // TODO: parse this
            })
        ));
    }

    named_ambiguous_expr!(and_binary -> (BinOp, Expr), allow_struct, tuple!(
        call!(BinOp::parse_binop),
        ambiguous_expr!(allow_struct)
    ));

    named_ambiguous_expr!(expr_unary -> ExprKind, allow_struct, do_parse!(
        operator: syn!(UnOp) >>
        operand: ambiguous_expr!(allow_struct) >>
        (ExprUnary { op: operator, expr: Box::new(operand) }.into())
    ));

    named!(and_cast -> (Ty, As), do_parse!(
        as_: syn!(As) >>
        ty: syn!(Ty) >>
        (ty, as_)
    ));

    named!(and_ascription -> (Ty, Colon),
           map!(tuple!(syn!(Colon), syn!(Ty)), |(a, b)| (b, a)));

    impl Synom for ExprIfLet {
        named!(parse -> Self, do_parse!(
            if_: syn!(If) >>
            let_: syn!(Let) >>
            pat: syn!(Pat) >>
            eq: syn!(Eq) >>
            cond: expr_no_struct >>
            then_block: braces!(call!(Block::parse_within)) >>
            else_block: option!(else_block) >>
            (ExprIfLet {
                pat: Box::new(pat),
                let_token: let_,
                eq_token: eq,
                expr: Box::new(cond),
                if_true: Block {
                    stmts: then_block.0,
                    brace_token: then_block.1,
                },
                if_token: if_,
                else_token: else_block.as_ref().map(|p| Else((p.0).0)),
                if_false: else_block.map(|p| Box::new(p.1.into())),
            })
        ));
    }

    impl Synom for ExprIf {
        named!(parse -> Self, do_parse!(
            if_: syn!(If) >>
            cond: expr_no_struct >>
            then_block: braces!(call!(Block::parse_within)) >>
            else_block: option!(else_block) >>
            (ExprIf {
                cond: Box::new(cond),
                if_true: Block {
                    stmts: then_block.0,
                    brace_token: then_block.1,
                },
                if_token: if_,
                else_token: else_block.as_ref().map(|p| Else((p.0).0)),
                if_false: else_block.map(|p| Box::new(p.1.into())),
            })
        ));
    }

    named!(else_block -> (Else, ExprKind), do_parse!(
        else_: syn!(Else) >>
        expr: alt!(
            syn!(ExprIf) => { ExprKind::If }
            |
            syn!(ExprIfLet) => { ExprKind::IfLet }
            |
            do_parse!(
                else_block: braces!(call!(Block::parse_within)) >>
                (ExprKind::Block(ExprBlock {
                    unsafety: Unsafety::Normal,
                    block: Block {
                        stmts: else_block.0,
                        brace_token: else_block.1,
                    },
                }))
            )
        ) >>
        (else_, expr)
    ));


    impl Synom for ExprForLoop {
        named!(parse -> Self, do_parse!(
            lbl: option!(tuple!(label, syn!(Colon))) >>
            for_: syn!(For) >>
            pat: syn!(Pat) >>
            in_: syn!(In) >>
            expr: expr_no_struct >>
            loop_block: syn!(Block) >>
            (ExprForLoop {
                for_token: for_,
                in_token: in_,
                pat: Box::new(pat),
                expr: Box::new(expr),
                body: loop_block,
                colon_token: lbl.as_ref().map(|p| Colon((p.1).0)),
                label: lbl.map(|p| p.0),
            })
        ));
    }

    impl Synom for ExprLoop {
        named!(parse -> Self, do_parse!(
            lbl: option!(tuple!(label, syn!(Colon))) >>
            loop_: syn!(Loop) >>
            loop_block: syn!(Block) >>
            (ExprLoop {
                loop_token: loop_,
                body: loop_block,
                colon_token: lbl.as_ref().map(|p| Colon((p.1).0)),
                label: lbl.map(|p| p.0),
            })
        ));
    }

    impl Synom for ExprMatch {
        named!(parse -> Self, do_parse!(
            match_: syn!(Match) >>
            obj: expr_no_struct >>
            res: braces!(do_parse!(
                mut arms: many0!(do_parse!(
                    arm: syn!(Arm) >>
                        cond!(arm_requires_comma(&arm), syn!(Comma)) >>
                        cond!(!arm_requires_comma(&arm), option!(syn!(Comma))) >>
                        (arm)
                )) >>
                last_arm: option!(syn!(Arm)) >>
                ({
                    arms.extend(last_arm);
                    arms
                })
            )) >>
            ({
                let (mut arms, brace) = res;
                ExprMatch {
                    expr: Box::new(obj),
                    match_token: match_,
                    brace_token: brace,
                    arms: {
                        for arm in &mut arms {
                            if arm_requires_comma(arm) {
                                arm.comma = Some(tokens::Comma::default());
                            }
                        }
                        arms
                    },
                }
            })
        ));
    }

    impl Synom for ExprCatch {
        named!(parse -> Self, do_parse!(
            do_: syn!(Do) >>
            catch_: syn!(Catch) >>
            catch_block: syn!(Block) >>
            (ExprCatch {
                block: catch_block,
                do_token: do_,
                catch_token: catch_,
            }.into())
        ));
    }

    fn arm_requires_comma(arm: &Arm) -> bool {
        if let ExprKind::Block(ExprBlock { unsafety: Unsafety::Normal, .. }) = arm.body.node {
            false
        } else {
            true
        }
    }

    impl Synom for Arm {
        named!(parse -> Self, do_parse!(
            attrs: many0!(call!(Attribute::parse_outer)) >>
            pats: call!(Delimited::parse_separated_nonempty) >>
            guard: option!(tuple!(syn!(If), syn!(Expr))) >>
            rocket: syn!(Rocket) >>
            body: alt!(
                map!(syn!(Block), |blk| {
                    ExprKind::Block(ExprBlock {
                        unsafety: Unsafety::Normal,
                        block: blk,
                    }).into()
                })
                |
                syn!(Expr)
            ) >>
            (Arm {
                rocket_token: rocket,
                if_token: guard.as_ref().map(|p| If((p.0).0)),
                attrs: attrs,
                pats: pats,
                guard: guard.map(|p| Box::new(p.1)),
                body: Box::new(body),
                comma: None,
            })
        ));
    }

    named_ambiguous_expr!(expr_closure -> ExprKind, allow_struct, do_parse!(
        capture: syn!(CaptureBy) >>
        or1: syn!(Or) >>
        inputs: call!(Delimited::parse_terminated_with, fn_arg) >>
        or2: syn!(Or) >>
        ret_and_body: alt!(
            do_parse!(
                arrow: syn!(RArrow) >>
                ty: syn!(Ty) >>
                body: syn!(Block) >>
                (FunctionRetTy::Ty(ty, arrow),
                 ExprKind::Block(ExprBlock {
                    unsafety: Unsafety::Normal,
                    block: body,
                }).into())
            )
            |
            map!(ambiguous_expr!(allow_struct), |e| (FunctionRetTy::Default, e))
        ) >>
        (ExprClosure {
            capture: capture,
            or1_token: or1,
            or2_token: or2,
            decl: Box::new(FnDecl {
                inputs: inputs,
                output: ret_and_body.0,
                variadic: false,
                dot_tokens: None,
                fn_token: tokens::Fn_::default(),
                generics: Generics::default(),
                paren_token: tokens::Paren::default(),
            }),
            body: Box::new(ret_and_body.1),
        }.into())
    ));

    named!(fn_arg -> FnArg, do_parse!(
        pat: syn!(Pat) >>
        ty: option!(tuple!(syn!(Colon), syn!(Ty))) >>
        ({
            let (colon, ty) = ty.unwrap_or_else(|| {
                (Colon::default(), TyInfer {
                    underscore_token: Underscore::default(),
                }.into())
            });
            ArgCaptured {
                pat: pat,
                colon_token: colon,
                ty: ty,
            }.into()
        })
    ));

    impl Synom for ExprWhile {
        named!(parse -> Self, do_parse!(
            lbl: option!(tuple!(label, syn!(Colon))) >>
            while_: syn!(While) >>
            cond: expr_no_struct >>
            while_block: syn!(Block) >>
            (ExprWhile {
                while_token: while_,
                colon_token: lbl.as_ref().map(|p| Colon((p.1).0)),
                cond: Box::new(cond),
                body: while_block,
                label: lbl.map(|p| p.0),
            })
        ));
    }

    impl Synom for ExprWhileLet {
        named!(parse -> Self, do_parse!(
            lbl: option!(tuple!(label, syn!(Colon))) >>
            while_: syn!(While) >>
            let_: syn!(Let) >>
            pat: syn!(Pat) >>
            eq: syn!(Eq) >>
            value: expr_no_struct >>
            while_block: syn!(Block) >>
            (ExprWhileLet {
                eq_token: eq,
                let_token: let_,
                while_token: while_,
                colon_token: lbl.as_ref().map(|p| Colon((p.1).0)),
                pat: Box::new(pat),
                expr: Box::new(value),
                body: while_block,
                label: lbl.map(|p| p.0),
            })
        ));
    }

    impl Synom for ExprContinue {
        named!(parse -> Self, do_parse!(
            cont: syn!(Continue) >>
            lbl: option!(label) >>
            (ExprContinue {
                continue_token: cont,
                label: lbl,
            })
        ));
    }

    named_ambiguous_expr!(expr_break -> ExprKind, allow_struct, do_parse!(
        break_: syn!(Break) >>
        lbl: option!(label) >>
        val: option!(call!(ambiguous_expr, allow_struct, false)) >>
        (ExprBreak {
            label: lbl,
            expr: val.map(Box::new),
            break_token: break_,
        }.into())
    ));

    named_ambiguous_expr!(expr_ret -> ExprKind, allow_struct, do_parse!(
        return_: syn!(Return) >>
        ret_value: option!(ambiguous_expr!(allow_struct)) >>
        (ExprRet {
            expr: ret_value.map(Box::new),
            return_token: return_,
        }.into())
    ));

    impl Synom for ExprStruct {
        named!(parse -> Self, do_parse!(
            path: syn!(Path) >>
            data: braces!(do_parse!(
                fields: call!(Delimited::parse_terminated) >>
                base: option!(
                    cond!(fields.is_empty() || fields.trailing_delim(),
                        do_parse!(
                            dots: syn!(Dot2) >>
                            base: syn!(Expr) >>
                            (dots, base)
                        )
                    )
                ) >>
                (fields, base)
            )) >>
            ({
                let ((fields, base), brace) = data;
                let (dots, rest) = match base.and_then(|b| b) {
                    Some((dots, base)) => (Some(dots), Some(base)),
                    None => (None, None),
                };
                ExprStruct {
                    brace_token: brace,
                    path: path,
                    fields: fields,
                    dot2_token: dots,
                    rest: rest.map(Box::new),
                }
            })
        ));
    }

    impl Synom for FieldValue {
        named!(parse -> Self, alt!(
            do_parse!(
                name: wordlike >>
                colon: syn!(Colon) >>
                value: syn!(Expr) >>
                (FieldValue {
                    ident: name,
                    expr: value,
                    is_shorthand: false,
                    attrs: Vec::new(),
                    colon_token: Some(colon),
                })
            )
            |
            map!(syn!(Ident), |name: Ident| FieldValue {
                ident: name.clone(),
                expr: ExprKind::Path(ExprPath { qself: None, path: name.into() }).into(),
                is_shorthand: true,
                attrs: Vec::new(),
                colon_token: None,
            })
        ));
    }

    impl Synom for ExprRepeat {
        named!(parse -> Self, do_parse!(
            data: brackets!(do_parse!(
                value: syn!(Expr) >>
                semi: syn!(Semi) >>
                times: syn!(Expr) >>
                (value, semi, times)
            )) >>
            (ExprRepeat {
                expr: Box::new((data.0).0),
                amt: Box::new((data.0).2),
                bracket_token: data.1,
                semi_token: (data.0).1,
            })
        ));
    }

    impl Synom for ExprBlock {
        named!(parse -> Self, do_parse!(
            rules: syn!(Unsafety) >>
            b: syn!(Block) >>
            (ExprBlock {
                unsafety: rules,
                block: b,
            })
        ));
    }

    named_ambiguous_expr!(expr_range -> ExprKind, allow_struct, do_parse!(
        limits: syn!(RangeLimits) >>
        hi: option!(ambiguous_expr!(allow_struct)) >>
        (ExprRange { from: None, to: hi.map(Box::new), limits: limits }.into())
    ));

    impl Synom for RangeLimits {
        named!(parse -> Self, alt!(
            // Must come before Dot2
            syn!(Dot3) => { RangeLimits::Closed }
            |
            syn!(Dot2) => { RangeLimits::HalfOpen }
        ));
    }

    impl Synom for ExprPath {
        named!(parse -> Self, do_parse!(
            pair: qpath >>
            (ExprPath {
                qself: pair.0,
                path: pair.1,
            })
        ));
    }

    named_ambiguous_expr!(expr_addr_of -> ExprKind, allow_struct, do_parse!(
        and: syn!(And) >>
        mutability: syn!(Mutability) >>
        expr: ambiguous_expr!(allow_struct) >>
        (ExprAddrOf {
            mutbl: mutability,
            expr: Box::new(expr),
            and_token: and,
        }.into())
    ));

    named_ambiguous_expr!(and_assign -> (Expr, Eq), allow_struct,
        map!(
            tuple!(syn!(Eq), ambiguous_expr!(allow_struct)),
            |(a, b)| (b, a)
        )
    );

    named_ambiguous_expr!(and_assign_op -> (BinOp, Expr), allow_struct, tuple!(
        call!(BinOp::parse_assign_op),
        ambiguous_expr!(allow_struct)
    ));

    named!(and_field -> (Ident, Dot),
           map!(tuple!(syn!(Dot), syn!(Ident)), |(a, b)| (b, a)));

    named!(and_tup_field -> (Lit, Dot),
           map!(tuple!(syn!(Dot), syn!(Lit)), |(a, b)| (b, a)));

    named!(and_index -> (Expr, tokens::Bracket), brackets!(syn!(Expr)));

    named_ambiguous_expr!(and_range -> (RangeLimits, Option<Expr>), allow_struct, tuple!(
        syn!(RangeLimits),
        option!(call!(ambiguous_expr, allow_struct, false))
    ));

    impl Synom for Block {
        named!(parse -> Self, do_parse!(
            stmts: braces!(call!(Block::parse_within)) >>
            (Block {
                stmts: stmts.0,
                brace_token: stmts.1,
            })
        ));
    }

    impl Block {
        named!(pub parse_within -> Vec<Stmt>, do_parse!(
            many0!(syn!(Semi)) >>
            mut standalone: many0!(terminated!(syn!(Stmt), many0!(syn!(Semi)))) >>
            last: option!(syn!(Expr)) >>
            (match last {
                None => standalone,
                Some(last) => {
                    standalone.push(Stmt::Expr(Box::new(last)));
                    standalone
                }
            })
        ));
    }

    impl Synom for Stmt {
        named!(parse -> Self, alt!(
            stmt_mac
            |
            stmt_local
            |
            stmt_item
            |
            stmt_expr
        ));
    }

    named!(stmt_mac -> Stmt, do_parse!(
        attrs: many0!(call!(Attribute::parse_outer)) >>
        what: syn!(Path) >>
        bang: syn!(Bang) >>
    // Only parse braces here; paren and bracket will get parsed as
    // expression statements
        data: braces!(syn!(TokenStream)) >>
        semi: option!(syn!(Semi)) >>
        (Stmt::Mac(Box::new((
            Mac {
                path: what,
                bang_token: bang,
                tokens: vec![TokenTree(proc_macro2::TokenTree {
                    span: ((data.1).0).0,
                    kind: TokenKind::Sequence(Delimiter::Brace, data.0),
                })],
            },
            match semi {
                Some(semi) => MacStmtStyle::Semicolon(semi),
                None => MacStmtStyle::Braces,
            },
            attrs,
        ))))
    ));

    named!(stmt_local -> Stmt, do_parse!(
        attrs: many0!(call!(Attribute::parse_outer)) >>
        let_: syn!(Let) >>
        pat: syn!(Pat) >>
        ty: option!(tuple!(syn!(Colon), syn!(Ty))) >>
        init: option!(tuple!(syn!(Eq), syn!(Expr))) >>
        semi: syn!(Semi) >>
        (Stmt::Local(Box::new(Local {
            let_token: let_,
            semi_token: semi,
            colon_token: ty.as_ref().map(|p| Colon((p.0).0)),
            eq_token: init.as_ref().map(|p| Eq((p.0).0)),
            pat: Box::new(pat),
            ty: ty.map(|p| Box::new(p.1)),
            init: init.map(|p| Box::new(p.1)),
            attrs: attrs,
        })))
    ));

    named!(stmt_item -> Stmt, map!(syn!(Item), |i| Stmt::Item(Box::new(i))));

    fn requires_semi(e: &Expr) -> bool {
        match e.node {
            ExprKind::If(_) |
            ExprKind::IfLet(_) |
            ExprKind::While(_) |
            ExprKind::WhileLet(_) |
            ExprKind::ForLoop(_) |
            ExprKind::Loop(_) |
            ExprKind::Match(_) |
            ExprKind::Block(_) => false,

            _ => true,
        }
    }

    named!(stmt_expr -> Stmt, do_parse!(
        attrs: many0!(call!(Attribute::parse_outer)) >>
        mut e: syn!(Expr) >>
        semi: option!(syn!(Semi)) >>
        ({
            e.attrs = attrs;
            if let Some(s) = semi {
                Stmt::Semi(Box::new(e), s)
            } else if requires_semi(&e) {
                return parse_error();
            } else {
                Stmt::Expr(Box::new(e))
            }
        })
    ));

    impl Synom for Pat {
        named!(parse -> Self, alt!(
            syn!(PatWild) => { Pat::Wild } // must be before pat_ident
            |
            syn!(PatBox) => { Pat::Box }  // must be before pat_ident
            |
            syn!(PatRange) => { Pat::Range } // must be before pat_lit
            |
            syn!(PatTupleStruct) => { Pat::TupleStruct }  // must be before pat_ident
            |
            syn!(PatStruct) => { Pat::Struct } // must be before pat_ident
            |
            syn!(Mac) => { Pat::Mac } // must be before pat_ident
            |
            syn!(PatLit) => { Pat::Lit } // must be before pat_ident
            |
            syn!(PatIdent) => { Pat::Ident } // must be before pat_path
            |
            syn!(PatPath) => { Pat::Path }
            |
            syn!(PatTuple) => { Pat::Tuple }
            |
            syn!(PatRef) => { Pat::Ref }
            |
            syn!(PatSlice) => { Pat::Slice }
        ));
    }

    impl Synom for PatWild {
        named!(parse -> Self, map!(
            syn!(Underscore),
            |u| PatWild { underscore_token: u }
        ));
    }

    impl Synom for PatBox {
        named!(parse -> Self, do_parse!(
            boxed: syn!(Box_) >>
            pat: syn!(Pat) >>
            (PatBox {
                pat: Box::new(pat),
                box_token: boxed,
            })
        ));
    }

    impl Synom for PatIdent {
        named!(parse -> Self, do_parse!(
            mode: option!(syn!(Ref)) >>
            mutability: syn!(Mutability) >>
            name: alt!(
                syn!(Ident)
                |
                syn!(Self_) => { Into::into }
            ) >>
            not!(syn!(Lt)) >>
            not!(syn!(Colon2)) >>
            subpat: option!(tuple!(syn!(At), syn!(Pat))) >>
            (PatIdent {
                mode: match mode {
                    Some(mode) => BindingMode::ByRef(mode, mutability),
                    None => BindingMode::ByValue(mutability),
                },
                ident: name,
                at_token: subpat.as_ref().map(|p| At((p.0).0)),
                subpat: subpat.map(|p| Box::new(p.1)),
            })
        ));
    }

    impl Synom for PatTupleStruct {
        named!(parse -> Self, do_parse!(
            path: syn!(Path) >>
            tuple: syn!(PatTuple) >>
            (PatTupleStruct {
                path: path,
                pat: tuple,
            })
        ));
    }

    impl Synom for PatStruct {
        named!(parse -> Self, do_parse!(
            path: syn!(Path) >>
            data: braces!(do_parse!(
                fields: call!(Delimited::parse_terminated) >>
                base: option!(
                    cond!(fields.is_empty() || fields.trailing_delim(),
                          syn!(Dot2))
                ) >>
                (fields, base)
            )) >>
            (PatStruct {
                path: path,
                fields: (data.0).0,
                brace_token: data.1,
                dot2_token: (data.0).1.and_then(|m| m),
            })
        ));
    }

    impl Synom for FieldPat {
        named!(parse -> Self, alt!(
            do_parse!(
                ident: wordlike >>
                colon: syn!(Colon) >>
                pat: syn!(Pat) >>
                (FieldPat {
                    ident: ident,
                    pat: Box::new(pat),
                    is_shorthand: false,
                    attrs: Vec::new(),
                    colon_token: Some(colon),
                })
            )
            |
            do_parse!(
                boxed: option!(syn!(Box_)) >>
                mode: option!(syn!(Ref)) >>
                mutability: syn!(Mutability) >>
                ident: syn!(Ident) >>
                ({
                    let mut pat: Pat = PatIdent {
                        mode: if let Some(mode) = mode {
                            BindingMode::ByRef(mode, mutability)
                        } else {
                            BindingMode::ByValue(mutability)
                        },
                        ident: ident.clone(),
                        subpat: None,
                        at_token: None,
                    }.into();
                    if let Some(boxed) = boxed {
                        pat = PatBox {
                            pat: Box::new(pat),
                            box_token: boxed,
                        }.into();
                    }
                    FieldPat {
                        ident: ident,
                        pat: Box::new(pat),
                        is_shorthand: true,
                        attrs: Vec::new(),
                        colon_token: None,
                    }
                })
            )
        ));
    }

    named!(wordlike -> Ident, alt!(
        syn!(Ident)
        |
        do_parse!(
            lit: syn!(Lit) >>
            ({
                let s = lit.value.to_string();
                if s.parse::<u32>().is_ok() {
                    Ident::new(s.into(), lit.span)
                } else {
                    return parse_error();
                }
            })
        )
    ));

    impl Synom for PatPath {
        named!(parse -> Self, map!(
            syn!(ExprPath),
            |p: ExprPath| PatPath { qself: p.qself, path: p.path }
        ));
    }

    impl Synom for PatTuple {
        named!(parse -> Self, do_parse!(
            data: parens!(do_parse!(
                elems: call!(Delimited::parse_terminated) >>
                dotdot: map!(cond!(
                    elems.is_empty() || elems.trailing_delim(),
                    option!(do_parse!(
                        dots: syn!(Dot2) >>
                        trailing: option!(syn!(Comma)) >>
                        (dots, trailing)
                    ))
                ), |x: Option<_>| x.and_then(|x| x)) >>
                rest: cond!(match dotdot {
                                Some((_, Some(_))) => true,
                                _ => false,
                            },
                            call!(Delimited::parse_terminated)) >>
                (elems, dotdot, rest)
            )) >>
            ({
                let ((mut elems, dotdot, rest), parens) = data;
                let (dotdot, trailing) = match dotdot {
                    Some((a, b)) => (Some(a), Some(b)),
                    None => (None, None),
                };
                PatTuple {
                    paren_token: parens,
                    dots_pos: dotdot.as_ref().map(|_| elems.len()),
                    dot2_token: dotdot,
                    comma_token: trailing.and_then(|b| b),
                    pats: {
                        if let Some(rest) = rest {
                            for elem in rest {
                                elems.push(elem);
                            }
                        }
                        elems
                    },
                }
            })
        ));
    }

    impl Synom for PatRef {
        named!(parse -> Self, do_parse!(
            and: syn!(And) >>
            mutability: syn!(Mutability) >>
            pat: syn!(Pat) >>
            (PatRef {
                pat: Box::new(pat),
                mutbl: mutability,
                and_token: and,
            })
        ));
    }

    impl Synom for PatLit {
        named!(parse -> Self, do_parse!(
            lit: pat_lit_expr >>
            (if let ExprKind::Path(_) = lit.node {
                return parse_error(); // these need to be parsed by pat_path
            } else {
                PatLit {
                    expr: Box::new(lit),
                }
            })
        ));
    }

    impl Synom for PatRange {
        named!(parse -> Self, do_parse!(
            lo: pat_lit_expr >>
            limits: syn!(RangeLimits) >>
            hi: pat_lit_expr >>
            (PatRange {
                lo: Box::new(lo),
                hi: Box::new(hi),
                limits: limits,
            })
        ));
    }

    named!(pat_lit_expr -> Expr, do_parse!(
        neg: option!(syn!(Sub)) >>
        v: alt!(
            syn!(Lit) => { ExprKind::Lit }
            |
            syn!(ExprPath) => { ExprKind::Path }
        ) >>
        (if neg.is_some() {
            ExprKind::Unary(ExprUnary {
                op: UnOp::Neg(tokens::Sub::default()),
                expr: Box::new(v.into())
            }).into()
        } else {
            v.into()
        })
    ));

    impl Synom for PatSlice {
        named!(parse -> Self, map!(
            brackets!(do_parse!(
                before: call!(Delimited::parse_terminated) >>
                middle: option!(do_parse!(
                    dots: syn!(Dot2) >>
                    trailing: option!(syn!(Comma)) >>
                    (dots, trailing)
                )) >>
                after: cond!(
                    match middle {
                        Some((_, ref trailing)) => trailing.is_some(),
                        _ => false,
                    },
                    call!(Delimited::parse_terminated)
                ) >>
                (before, middle, after)
            )),
            |((before, middle, after), brackets)| {
                let mut before: Delimited<Pat, tokens::Comma> = before;
                let after: Option<Delimited<Pat, tokens::Comma>> = after;
                let middle: Option<(Dot2, Option<Comma>)> = middle;
                PatSlice {
                    dot2_token: middle.as_ref().map(|m| Dot2((m.0).0)),
                    comma_token: middle.as_ref().and_then(|m| {
                        m.1.as_ref().map(|m| Comma(m.0))
                    }),
                    bracket_token: brackets,
                    middle: middle.and_then(|_| {
                        if !before.is_empty() && !before.trailing_delim() {
                            Some(Box::new(before.pop().unwrap().into_item()))
                        } else {
                            None
                        }
                    }),
                    front: before,
                    back: after.unwrap_or_default(),
                }
            }
        ));
    }

    impl Synom for CaptureBy {
        named!(parse -> Self, alt!(
            syn!(Move) => { CaptureBy::Value }
            |
            epsilon!() => { |_| CaptureBy::Ref }
        ));
    }

    named!(label -> Ident, map!(syn!(Lifetime), |lt: Lifetime| lt.ident));
}

#[cfg(feature = "printing")]
mod printing {
    use super::*;
    use attr::FilterAttrs;
    use quote::{Tokens, ToTokens};

    impl ToTokens for Expr {
        fn to_tokens(&self, tokens: &mut Tokens) {
            tokens.append_all(self.attrs.outer());
            self.node.to_tokens(tokens)
        }
    }

    impl ToTokens for ExprBox {
        fn to_tokens(&self, tokens: &mut Tokens) {
            self.box_token.to_tokens(tokens);
            self.expr.to_tokens(tokens);
        }
    }

    impl ToTokens for ExprInPlace {
        fn to_tokens(&self, tokens: &mut Tokens) {
            self.in_token.to_tokens(tokens);
            self.place.to_tokens(tokens);
            self.value.to_tokens(tokens);
        }
    }

    impl ToTokens for ExprArray {
        fn to_tokens(&self, tokens: &mut Tokens) {
            self.bracket_token.surround(tokens, |tokens| {
                self.exprs.to_tokens(tokens);
            })
        }
    }

    impl ToTokens for ExprCall {
        fn to_tokens(&self, tokens: &mut Tokens) {
            self.func.to_tokens(tokens);
            self.paren_token.surround(tokens, |tokens| {
                self.args.to_tokens(tokens);
            })
        }
    }

    impl ToTokens for ExprMethodCall {
        fn to_tokens(&self, tokens: &mut Tokens) {
            self.expr.to_tokens(tokens);
            self.dot_token.to_tokens(tokens);
            self.method.to_tokens(tokens);
            self.colon2_token.to_tokens(tokens);
            self.lt_token.to_tokens(tokens);
            self.typarams.to_tokens(tokens);
            self.gt_token.to_tokens(tokens);
            self.paren_token.surround(tokens, |tokens| {
                self.args.to_tokens(tokens);
            });
        }
    }

    impl ToTokens for ExprTup {
        fn to_tokens(&self, tokens: &mut Tokens) {
            self.paren_token.surround(tokens, |tokens| {
                self.args.to_tokens(tokens);
                self.lone_comma.to_tokens(tokens);
            })
        }
    }

    impl ToTokens for ExprBinary {
        fn to_tokens(&self, tokens: &mut 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 Tokens) {
            self.op.to_tokens(tokens);
            self.expr.to_tokens(tokens);
        }
    }

    impl ToTokens for ExprCast {
        fn to_tokens(&self, tokens: &mut Tokens) {
            self.expr.to_tokens(tokens);
            self.as_token.to_tokens(tokens);
            self.ty.to_tokens(tokens);
        }
    }

    impl ToTokens for ExprType {
        fn to_tokens(&self, tokens: &mut Tokens) {
            self.expr.to_tokens(tokens);
            self.colon_token.to_tokens(tokens);
            self.ty.to_tokens(tokens);
        }
    }

    impl ToTokens for ExprIf {
        fn to_tokens(&self, tokens: &mut Tokens) {
            self.if_token.to_tokens(tokens);
            self.cond.to_tokens(tokens);
            self.if_true.to_tokens(tokens);
            self.else_token.to_tokens(tokens);
            self.if_false.to_tokens(tokens);
        }
    }

    impl ToTokens for ExprIfLet {
        fn to_tokens(&self, tokens: &mut Tokens) {
            self.if_token.to_tokens(tokens);
            self.let_token.to_tokens(tokens);
            self.pat.to_tokens(tokens);
            self.eq_token.to_tokens(tokens);
            self.expr.to_tokens(tokens);
            self.if_true.to_tokens(tokens);
            self.else_token.to_tokens(tokens);
            self.if_false.to_tokens(tokens);
        }
    }

    impl ToTokens for ExprWhile {
        fn to_tokens(&self, tokens: &mut Tokens) {
            self.label.to_tokens(tokens);
            self.colon_token.to_tokens(tokens);
            self.while_token.to_tokens(tokens);
            self.cond.to_tokens(tokens);
            self.body.to_tokens(tokens);
        }
    }

    impl ToTokens for ExprWhileLet {
        fn to_tokens(&self, tokens: &mut Tokens) {
            self.label.to_tokens(tokens);
            self.colon_token.to_tokens(tokens);
            self.while_token.to_tokens(tokens);
            self.let_token.to_tokens(tokens);
            self.pat.to_tokens(tokens);
            self.eq_token.to_tokens(tokens);
            self.expr.to_tokens(tokens);
            self.body.to_tokens(tokens);
        }
    }

    impl ToTokens for ExprForLoop {
        fn to_tokens(&self, tokens: &mut Tokens) {
            self.label.to_tokens(tokens);
            self.colon_token.to_tokens(tokens);
            self.for_token.to_tokens(tokens);
            self.pat.to_tokens(tokens);
            self.in_token.to_tokens(tokens);
            self.expr.to_tokens(tokens);
            self.body.to_tokens(tokens);
        }
    }

    impl ToTokens for ExprLoop {
        fn to_tokens(&self, tokens: &mut Tokens) {
            self.label.to_tokens(tokens);
            self.colon_token.to_tokens(tokens);
            self.loop_token.to_tokens(tokens);
            self.body.to_tokens(tokens);
        }
    }

    impl ToTokens for ExprMatch {
        fn to_tokens(&self, tokens: &mut Tokens) {
            self.match_token.to_tokens(tokens);
            self.expr.to_tokens(tokens);
            self.brace_token.surround(tokens, |tokens| {
                tokens.append_all(&self.arms);
            });
        }
    }

    impl ToTokens for ExprCatch {
        fn to_tokens(&self, tokens: &mut Tokens) {
            self.do_token.to_tokens(tokens);
            self.catch_token.to_tokens(tokens);
            self.block.to_tokens(tokens);
        }
    }

    impl ToTokens for ExprClosure {
        fn to_tokens(&self, tokens: &mut Tokens) {
            self.capture.to_tokens(tokens);
            self.or1_token.to_tokens(tokens);
            for item in self.decl.inputs.iter() {
                match **item.item() {
                    FnArg::Captured(ArgCaptured { ref pat, ty: Ty::Infer(_), .. }) => {
                        pat.to_tokens(tokens);
                    }
                    _ => item.item().to_tokens(tokens),
                }
                item.delimiter().to_tokens(tokens);
            }
            self.or2_token.to_tokens(tokens);
            self.decl.output.to_tokens(tokens);
            self.body.to_tokens(tokens);
        }
    }

    impl ToTokens for ExprBlock {
        fn to_tokens(&self, tokens: &mut Tokens) {
            self.unsafety.to_tokens(tokens);
            self.block.to_tokens(tokens);
        }
    }

    impl ToTokens for ExprAssign {
        fn to_tokens(&self, tokens: &mut Tokens) {
            self.left.to_tokens(tokens);
            self.eq_token.to_tokens(tokens);
            self.right.to_tokens(tokens);
        }
    }

    impl ToTokens for ExprAssignOp {
        fn to_tokens(&self, tokens: &mut 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 Tokens) {
            self.expr.to_tokens(tokens);
            self.dot_token.to_tokens(tokens);
            self.field.to_tokens(tokens);
        }
    }

    impl ToTokens for ExprTupField {
        fn to_tokens(&self, tokens: &mut Tokens) {
            self.expr.to_tokens(tokens);
            self.dot_token.to_tokens(tokens);
            self.field.to_tokens(tokens);
        }
    }

    impl ToTokens for ExprIndex {
        fn to_tokens(&self, tokens: &mut Tokens) {
            self.expr.to_tokens(tokens);
            self.bracket_token.surround(tokens, |tokens| {
                self.index.to_tokens(tokens);
            });
        }
    }

    impl ToTokens for ExprRange {
        fn to_tokens(&self, tokens: &mut Tokens) {
            self.from.to_tokens(tokens);
            self.limits.to_tokens(tokens);
            self.to.to_tokens(tokens);
        }
    }

    impl ToTokens for ExprPath {
        fn to_tokens(&self, tokens: &mut Tokens) {
            ::PathTokens(&self.qself, &self.path).to_tokens(tokens)
        }
    }

    impl ToTokens for ExprAddrOf {
        fn to_tokens(&self, tokens: &mut Tokens) {
            self.and_token.to_tokens(tokens);
            self.mutbl.to_tokens(tokens);
            self.expr.to_tokens(tokens);
        }
    }

    impl ToTokens for ExprBreak {
        fn to_tokens(&self, tokens: &mut Tokens) {
            self.break_token.to_tokens(tokens);
            self.label.to_tokens(tokens);
            self.expr.to_tokens(tokens);
        }
    }

    impl ToTokens for ExprContinue {
        fn to_tokens(&self, tokens: &mut Tokens) {
            self.continue_token.to_tokens(tokens);
            self.label.to_tokens(tokens);
        }
    }

    impl ToTokens for ExprRet {
        fn to_tokens(&self, tokens: &mut Tokens) {
            self.return_token.to_tokens(tokens);
            self.expr.to_tokens(tokens);
        }
    }

    impl ToTokens for ExprStruct {
        fn to_tokens(&self, tokens: &mut Tokens) {
            self.path.to_tokens(tokens);
            self.brace_token.surround(tokens, |tokens| {
                self.fields.to_tokens(tokens);
                self.dot2_token.to_tokens(tokens);
                self.rest.to_tokens(tokens);
            })
        }
    }

    impl ToTokens for ExprRepeat {
        fn to_tokens(&self, tokens: &mut Tokens) {
            self.bracket_token.surround(tokens, |tokens| {
                self.expr.to_tokens(tokens);
                self.semi_token.to_tokens(tokens);
                self.amt.to_tokens(tokens);
            })
        }
    }

    impl ToTokens for ExprParen {
        fn to_tokens(&self, tokens: &mut Tokens) {
            self.paren_token.surround(tokens, |tokens| {
                self.expr.to_tokens(tokens);
            });
        }
    }

    impl ToTokens for ExprTry {
        fn to_tokens(&self, tokens: &mut Tokens) {
            self.expr.to_tokens(tokens);
            self.question_token.to_tokens(tokens);
        }
    }

    impl ToTokens for FieldValue {
        fn to_tokens(&self, tokens: &mut Tokens) {
            self.ident.to_tokens(tokens);
            if !self.is_shorthand {
                self.colon_token.to_tokens(tokens);
                self.expr.to_tokens(tokens);
            }
        }
    }

    impl ToTokens for Arm {
        fn to_tokens(&self, tokens: &mut Tokens) {
            tokens.append_all(&self.attrs);
            self.pats.to_tokens(tokens);
            self.if_token.to_tokens(tokens);
            self.guard.to_tokens(tokens);
            self.rocket_token.to_tokens(tokens);
            self.body.to_tokens(tokens);
            self.comma.to_tokens(tokens);
        }
    }

    impl ToTokens for PatWild {
        fn to_tokens(&self, tokens: &mut Tokens) {
            self.underscore_token.to_tokens(tokens);
        }
    }

    impl ToTokens for PatIdent {
        fn to_tokens(&self, tokens: &mut Tokens) {
            self.mode.to_tokens(tokens);
            self.ident.to_tokens(tokens);
            self.at_token.to_tokens(tokens);
            self.subpat.to_tokens(tokens);
        }
    }

    impl ToTokens for PatStruct {
        fn to_tokens(&self, tokens: &mut Tokens) {
            self.path.to_tokens(tokens);
            self.brace_token.surround(tokens, |tokens| {
                self.fields.to_tokens(tokens);
                self.dot2_token.to_tokens(tokens);
            });
        }
    }

    impl ToTokens for PatTupleStruct {
        fn to_tokens(&self, tokens: &mut Tokens) {
            self.path.to_tokens(tokens);
            self.pat.to_tokens(tokens);
        }
    }

    impl ToTokens for PatPath {
        fn to_tokens(&self, tokens: &mut Tokens) {
            ::PathTokens(&self.qself, &self.path).to_tokens(tokens);
        }
    }

    impl ToTokens for PatTuple {
        fn to_tokens(&self, tokens: &mut Tokens) {
            self.paren_token.surround(tokens, |tokens| {
                for (i, token) in self.pats.iter().enumerate() {
                    if Some(i) == self.dots_pos {
                        self.dot2_token.to_tokens(tokens);
                        self.comma_token.to_tokens(tokens);
                    }
                    token.to_tokens(tokens);
                }

                if Some(self.pats.len()) == self.dots_pos {
                    self.dot2_token.to_tokens(tokens);
                }
            });
        }
    }

    impl ToTokens for PatBox {
        fn to_tokens(&self, tokens: &mut Tokens) {
            self.box_token.to_tokens(tokens);
            self.pat.to_tokens(tokens);
        }
    }

    impl ToTokens for PatRef {
        fn to_tokens(&self, tokens: &mut Tokens) {
            self.and_token.to_tokens(tokens);
            self.mutbl.to_tokens(tokens);
            self.pat.to_tokens(tokens);
        }
    }

    impl ToTokens for PatLit {
        fn to_tokens(&self, tokens: &mut Tokens) {
            self.expr.to_tokens(tokens);
        }
    }

    impl ToTokens for PatRange {
        fn to_tokens(&self, tokens: &mut Tokens) {
            self.lo.to_tokens(tokens);
            self.limits.to_tokens(tokens);
            self.hi.to_tokens(tokens);
        }
    }

    impl ToTokens for PatSlice {
        fn to_tokens(&self, tokens: &mut Tokens) {
            self.bracket_token.surround(tokens, |tokens| {
                self.front.to_tokens(tokens);
                self.middle.to_tokens(tokens);
                self.dot2_token.to_tokens(tokens);
                self.comma_token.to_tokens(tokens);
                self.back.to_tokens(tokens);
            })
        }
    }

    impl ToTokens for RangeLimits {
        fn to_tokens(&self, tokens: &mut Tokens) {
            match *self {
                RangeLimits::HalfOpen(ref t) => t.to_tokens(tokens),
                RangeLimits::Closed(ref t) => t.to_tokens(tokens),
            }
        }
    }

    impl ToTokens for FieldPat {
        fn to_tokens(&self, tokens: &mut Tokens) {
            if !self.is_shorthand {
                self.ident.to_tokens(tokens);
                self.colon_token.to_tokens(tokens);
            }
            self.pat.to_tokens(tokens);
        }
    }

    impl ToTokens for BindingMode {
        fn to_tokens(&self, tokens: &mut Tokens) {
            match *self {
                BindingMode::ByRef(ref t, ref m) => {
                    t.to_tokens(tokens);
                    m.to_tokens(tokens);
                }
                BindingMode::ByValue(ref m) => {
                    m.to_tokens(tokens);
                }
            }
        }
    }

    impl ToTokens for CaptureBy {
        fn to_tokens(&self, tokens: &mut Tokens) {
            match *self {
                CaptureBy::Value(ref t) => t.to_tokens(tokens),
                CaptureBy::Ref => {
                    // nothing
                }
            }
        }
    }

    impl ToTokens for Block {
        fn to_tokens(&self, tokens: &mut Tokens) {
            self.brace_token.surround(tokens, |tokens| {
                tokens.append_all(&self.stmts);
            });
        }
    }

    impl ToTokens for Stmt {
        fn to_tokens(&self, tokens: &mut Tokens) {
            match *self {
                Stmt::Local(ref local) => local.to_tokens(tokens),
                Stmt::Item(ref item) => item.to_tokens(tokens),
                Stmt::Expr(ref expr) => expr.to_tokens(tokens),
                Stmt::Semi(ref expr, ref semi) => {
                    expr.to_tokens(tokens);
                    semi.to_tokens(tokens);
                }
                Stmt::Mac(ref mac) => {
                    let (ref mac, ref style, ref attrs) = **mac;
                    tokens.append_all(attrs.outer());
                    mac.to_tokens(tokens);
                    match *style {
                        MacStmtStyle::Semicolon(ref s) => s.to_tokens(tokens),
                        MacStmtStyle::Braces | MacStmtStyle::NoBraces => {
                            // no semicolon
                        }
                    }
                }
            }
        }
    }

    impl ToTokens for Local {
        fn to_tokens(&self, tokens: &mut Tokens) {
            tokens.append_all(self.attrs.outer());
            self.let_token.to_tokens(tokens);
            self.pat.to_tokens(tokens);
            self.colon_token.to_tokens(tokens);
            self.ty.to_tokens(tokens);
            self.eq_token.to_tokens(tokens);
            self.init.to_tokens(tokens);
            self.semi_token.to_tokens(tokens);
        }
    }
}