src/lib.rs

#[macro_use]
extern crate nom;

use nom::IResult;
use nom::{digit, multispace as space};

use std::str;

#[derive(Debug, Clone, Eq, PartialEq)]
pub struct Item {
    pub ident: Ident,
    pub vis: Visibility,
    pub attrs: Vec<Attribute>,
    pub generics: Generics,
    pub body: Body,
}

pub type Ident = String;

#[derive(Debug, Clone, Eq, PartialEq)]
pub struct Attribute {
    pub value: MetaItem,
    pub is_sugared_doc: bool,
}

/// A compile-time attribute item.
///
/// E.g. `#[test]`, `#[derive(..)]` or `#[feature = "foo"]`
#[derive(Debug, Clone, Eq, PartialEq)]
pub enum MetaItem {
    /// Word meta item.
    ///
    /// E.g. `test` as in `#[test]`
    Word(Ident),
    /// List meta item.
    ///
    /// E.g. `derive(..)` as in `#[derive(..)]`
    List(Ident, Vec<MetaItem>),
    /// Name value meta item.
    ///
    /// E.g. `feature = "foo"` as in `#[feature = "foo"]`
    NameValue(Ident, String),
}

#[derive(Debug, Clone, Eq, PartialEq, Default)]
pub struct Generics {
    pub lifetimes: Vec<LifetimeDef>,
    pub ty_params: Vec<TyParam>,
    pub where_clause: Vec<WherePredicate>,
}

/// A single predicate in a `where` clause
#[derive(Debug, Clone, Eq, PartialEq)]
pub enum WherePredicate {
    /// A type binding, e.g. `for<'c> Foo: Send+Clone+'c`
    BoundPredicate(WhereBoundPredicate),
    /// A lifetime predicate, e.g. `'a: 'b+'c`
    RegionPredicate(WhereRegionPredicate),
}

/// A type bound.
///
/// E.g. `for<'c> Foo: Send+Clone+'c`
#[derive(Debug, Clone, Eq, PartialEq)]
pub struct WhereBoundPredicate {
    /// Any lifetimes from a `for` binding
    pub bound_lifetimes: Vec<LifetimeDef>,
    /// The type being bounded
    pub bounded_ty: Ty,
    /// Trait and lifetime bounds (`Clone+Send+'static`)
    pub bounds: Vec<TyParamBound>,
}

/// A lifetime predicate.
///
/// E.g. `'a: 'b+'c`
#[derive(Debug, Clone, Eq, PartialEq)]
pub struct WhereRegionPredicate {
    pub lifetime: Lifetime,
    pub bounds: Vec<Lifetime>,
}

#[derive(Debug, Clone, Eq, PartialEq)]
pub struct LifetimeDef {
    pub lifetime: Lifetime,
    pub bounds: Vec<Lifetime>,
}

#[derive(Debug, Clone, Eq, PartialEq)]
pub struct Lifetime {
    pub ident: Ident,
}

#[derive(Debug, Clone, Eq, PartialEq)]
pub struct TyParam {
    pub ident: Ident,
    pub bounds: Vec<TyParamBound>,
    pub default: Option<Ty>,
}

#[derive(Debug, Clone, Eq, PartialEq)]
pub enum TyParamBound {
    MaybeSized,
    Region(Lifetime),
    Trait(PolyTraitRef),
}

#[derive(Debug, Clone, Eq, PartialEq)]
pub struct PolyTraitRef {
    /// The `'a` in `<'a> Foo<&'a T>`
    pub bound_lifetimes: Vec<LifetimeDef>,
    /// The `Foo<&'a T>` in `<'a> Foo<&'a T>`
    pub trait_ref: Path,
}

#[derive(Debug, Clone, Eq, PartialEq)]
pub struct Path {
    pub global: bool,
    pub segments: Vec<PathSegment>,
}

/// A segment of a path: an identifier, an optional lifetime, and a set of types.
///
/// E.g. `std`, `String` or `Box<T>`
#[derive(Debug, Clone, Eq, PartialEq)]
pub struct PathSegment {
    pub ident: Ident,
    pub parameters: PathParameters,
}

impl PathSegment {
    pub fn ident(ident: Ident) -> Self {
        PathSegment {
            ident: ident,
            parameters: PathParameters::none(),
        }
    }
}

/// Parameters of a path segment.
///
/// E.g. `<A, B>` as in `Foo<A, B>` or `(A, B)` as in `Foo(A, B)`
#[derive(Debug, Clone, Eq, PartialEq)]
pub enum PathParameters {
    /// The `<'a, A, B, C>` in `foo::bar::baz::<'a, A, B, C>`
    AngleBracketed(AngleBracketedParameterData),
    /// The `(A, B)` and `C` in `Foo(A, B) -> C`
    Parenthesized(ParenthesizedParameterData),
}

impl PathParameters {
    pub fn none() -> Self {
        PathParameters::AngleBracketed(AngleBracketedParameterData::default())
    }
}

/// A path like `Foo<'a, T>`
#[derive(Debug, Clone, Eq, PartialEq, Default)]
pub struct AngleBracketedParameterData {
    /// The lifetime parameters for this path segment.
    pub lifetimes: Vec<Lifetime>,
    /// The type parameters for this path segment, if present.
    pub types: Vec<Ty>,
    /// Bindings (equality constraints) on associated types, if present.
    ///
    /// E.g., `Foo<A=Bar>`.
    pub bindings: Vec<TypeBinding>,
}

/// Bind a type to an associated type: `A=Foo`.
#[derive(Debug, Clone, Eq, PartialEq)]
pub struct TypeBinding {
    pub ident: Ident,
    pub ty: Ty,
}

/// A path like `Foo(A,B) -> C`
#[derive(Debug, Clone, Eq, PartialEq)]
pub struct ParenthesizedParameterData {
    /// `(A, B)`
    pub inputs: Vec<Ty>,
    /// `C`
    pub output: Option<Ty>,
}

#[derive(Debug, Clone, Eq, PartialEq)]
pub enum Body {
    Enum(Vec<Variant>),
    Struct(Style, Vec<Field>),
}

#[derive(Debug, Clone, Eq, PartialEq)]
pub struct Variant {
    pub ident: Ident,
    pub attrs: Vec<Attribute>,
    pub style: Style,
    pub fields: Vec<Field>,
}

#[derive(Debug, Clone, Eq, PartialEq)]
pub enum Style {
    Struct,
    Tuple,
    Unit,
}

#[derive(Debug, Clone, Eq, PartialEq)]
pub struct Field {
    pub ident: Option<Ident>,
    pub vis: Visibility,
    pub attrs: Vec<Attribute>,
    pub ty: Ty,
}

#[derive(Debug, Clone, Eq, PartialEq)]
pub enum Visibility {
    Public,
    Inherited,
}

#[derive(Debug, Clone, Eq, PartialEq)]
pub enum Ty {
    /// A variable-length array (`[T]`)
    Vec(Box<Ty>),
    /// A fixed length array (`[T; n]`)
    FixedLengthVec(Box<Ty>, usize),
    /// A raw pointer (`*const T` or `*mut T`)
    Ptr(Box<MutTy>),
    /// A reference (`&'a T` or `&'a mut T`)
    Rptr(Option<Lifetime>, Box<MutTy>),
    /// A bare function (e.g. `fn(usize) -> bool`)
    BareFn(Box<BareFnTy>),
    /// The never type (`!`)
    Never,
    /// A tuple (`(A, B, C, D, ...)`)
    Tup(Vec<Ty>),
    /// A path (`module::module::...::Type`), optionally
    /// "qualified", e.g. `<Vec<T> as SomeTrait>::SomeType`.
    ///
    /// Type parameters are stored in the Path itself
    Path(Option<QSelf>, Path),
    /// Something like `A+B`. Note that `B` must always be a path.
    ObjectSum(Box<Ty>, Vec<TyParamBound>),
    /// A type like `for<'a> Foo<&'a Bar>`
    PolyTraitRef(Vec<TyParamBound>),
    /// An `impl TraitA+TraitB` type.
    ImplTrait(Vec<TyParamBound>),
    /// No-op; kept solely so that we can pretty-print faithfully
    Paren(Box<Ty>),
    /// TyKind::Infer means the type should be inferred instead of it having been
    /// specified. This can appear anywhere in a type.
    Infer,
}

#[derive(Debug, Clone, Eq, PartialEq)]
pub struct MutTy {
    pub ty: Ty,
    pub mutability: Mutability,
}

#[derive(Debug, Clone, Eq, PartialEq)]
pub enum Mutability {
    Mutable,
    Immutable,
}

/// The explicit Self type in a "qualified path". The actual
/// path, including the trait and the associated item, is stored
/// separately. `position` represents the index of the associated
/// item qualified with this Self type.
///
/// ```rust,ignore
/// <Vec<T> as a::b::Trait>::AssociatedItem
///  ^~~~~     ~~~~~~~~~~~~~~^
///  ty        position = 3
///
/// <Vec<T>>::AssociatedItem
///  ^~~~~    ^
///  ty       position = 0
/// ```
#[derive(Debug, Clone, Eq, PartialEq)]
pub struct QSelf {
    pub ty: Box<Ty>,
    pub position: usize
}

#[derive(Debug, Clone, Eq, PartialEq)]
pub struct BareFnTy {
    pub lifetimes: Vec<LifetimeDef>,
    pub decl: FnDecl
}

/// Header (not the body) of a function declaration.
///
/// E.g. `fn foo(bar: baz)`
#[derive(Debug, Clone, Eq, PartialEq)]
pub struct FnDecl {
    pub inputs: Vec<Arg>,
    pub output: FunctionRetTy,
}

/// An argument in a function header.
///
/// E.g. `bar: usize` as in `fn foo(bar: usize)`
#[derive(Debug, Clone, Eq, PartialEq)]
pub struct Arg {
    pub pat: Option<Ident>,
    pub ty: Ty,
}

#[derive(Debug, Clone, Eq, PartialEq)]
pub enum FunctionRetTy {
    /// Return type is not specified.
    ///
    /// Functions default to `()` and
    /// closures default to inference. Span points to where return
    /// type would be inserted.
    Default,
    /// Everything else
    Ty(Ty),
}

pub fn epsilon<T>(input: T) -> IResult<T, ()> {
    IResult::Done(input, ())
}

pub fn escaped_string(input: &str) -> IResult<&str, String> {
    let mut s = String::new();
    let mut chars = input.char_indices().peekable();
    while let Some((byte_offset, ch)) = chars.next() {
        match ch {
            '"' => {
                return IResult::Done(&input[byte_offset..], s);
            }
            '\\' => {
                match chars.next() {
                    Some((_, 'x')) => unimplemented!(),
                    Some((_, 'u')) => unimplemented!(),
                    Some((_, 'n')) => s.push('\n'),
                    Some((_, 'r')) => s.push('\r'),
                    Some((_, 't')) => s.push('\t'),
                    Some((_, '0')) => s.push('\0'),
                    Some((_, '\\')) => s.push('\\'),
                    Some((_, '\n')) => {
                        while let Some(&(_, ch)) = chars.peek() {
                            if ch.is_whitespace() {
                                chars.next();
                            } else {
                                break;
                            }
                        }
                    }
                    _ => break,
                }
            }
            ch => {
                s.push(ch);
            }
        }
    }
    IResult::Error(nom::Err::Position(nom::ErrorKind::Escaped, input))
}

macro_rules! punct {
    ($i:expr, $ch:expr) => {
        tuple!($i, opt!(space), tag_s!($ch))
    };
}

named!(quoted<&str, String>, delimited!(
    punct!("\""),
    escaped_string,
    tag_s!("\"")
));

named!(meta_item<&str, MetaItem>, alt!(
    chain!(
        ident: word ~
        punct!("(") ~
        inner: separated_list!(punct!(","), meta_item) ~
        punct!(")"),
        move || MetaItem::List(ident, inner)
    )
    |
    chain!(
        ident: word ~
        punct!("=") ~
        string: quoted,
        move || MetaItem::NameValue(ident, string)
    )
    |
    map!(word, MetaItem::Word)
));

named!(attribute<&str, Attribute>, chain!(
    punct!("#") ~
    punct!("[") ~
    meta_item: meta_item ~
    punct!("]"),
    move || Attribute {
        value: meta_item,
        is_sugared_doc: false,
    }
));

named!(mutability<&str, Mutability>, preceded!(
    opt!(space),
    alt!(
        terminated!(tag_s!("mut"), space) => { |_| Mutability::Mutable }
        |
        epsilon => { |_| Mutability::Immutable }
    )
));

named!(visibility<&str, Visibility>, preceded!(
    opt!(space),
    alt!(
        terminated!(tag_s!("pub"), space) => { |_| Visibility::Public }
        |
        epsilon => { |_| Visibility::Inherited }
    )
));

fn ident_ch(ch: char) -> bool {
    ch.is_alphanumeric() || ch == '_'
}

named!(word<&str, Ident>, preceded!(
    opt!(space),
    map!(take_while1_s!(ident_ch), String::from)
));

macro_rules! opt_vec (
    ($i:expr, $submac:ident!( $($args:tt)* )) => ({
        match $submac!($i, $($args)*) {
            IResult::Done(i, o) => IResult::Done(i, o),
            IResult::Error(_) => IResult::Done($i, Vec::new()),
            IResult::Incomplete(i) => IResult::Incomplete(i)
        }
    });
);

named!(type_binding<&str, TypeBinding>, chain!(
    ident: word ~
    punct!("=") ~
    ty: ty,
    move || TypeBinding {
        ident: ident,
        ty: ty,
    }
));

named!(path_segment<&str, PathSegment>, alt!(
    chain!(
        ident: word ~
        punct!("<") ~
        lifetimes: separated_list!(punct!(","), lifetime) ~
        types: opt_vec!(preceded!(
            cond!(!lifetimes.is_empty(), punct!(",")),
            separated_nonempty_list!(
                punct!(","),
                terminated!(ty, not!(peek!(punct!("="))))
            )
        )) ~
        bindings: opt_vec!(preceded!(
            cond!(!lifetimes.is_empty() || !types.is_empty(), punct!(",")),
            separated_nonempty_list!(punct!(","), type_binding)
        )) ~
        punct!(">"),
        move || PathSegment {
            ident: ident,
            parameters: PathParameters::AngleBracketed(
                AngleBracketedParameterData {
                    lifetimes: lifetimes,
                    types: types,
                    bindings: bindings,
                }
            ),
        }
    )
    |
    map!(word, PathSegment::ident)
));

named!(path<&str, Path>, chain!(
    global: punct!("::")? ~
    segments: separated_nonempty_list!(punct!("::"), path_segment),
    move || Path {
        global: global.is_some(),
        segments: segments,
    }
));

named!(fn_arg<&str, Arg>, chain!(
    pat: opt!(terminated!(word, punct!(":"))) ~
    ty: ty,
    move || Arg {
        pat: pat,
        ty: ty,
    }
));

named!(ty<&str, Ty>, alt!(
    delimited!(
        punct!("["),
        ty,
        punct!("]")
    ) => { |elem| Ty::Vec(Box::new(elem)) }
    |
    chain!(
        punct!("[") ~
        elem: ty ~
        punct!(";") ~
        space? ~
        size: map_res!(digit, str::parse),
        move || Ty::FixedLengthVec(Box::new(elem), size)
    )
    |
    chain!(
        punct!("*") ~
        mutability: alt!(
            punct!("const") => { |_| Mutability::Immutable }
            |
            punct!("mut") => { |_| Mutability::Mutable }
        ) ~
        target: ty,
        move || Ty::Ptr(Box::new(MutTy {
            ty: target,
            mutability: mutability,
        }))
    )
    |
    chain!(
        punct!("&") ~
        life: lifetime? ~
        mutability: mutability ~
        target: ty,
        move || Ty::Rptr(life, Box::new(MutTy {
            ty: target,
            mutability: mutability,
        }))
    )
    |
    chain!(
        punct!("fn") ~
        space ~
        lifetimes: opt_vec!(delimited!(
            punct!("<"),
            separated_list!(punct!(","), lifetime_def),
            punct!(">")
        )) ~
        punct!("(") ~
        inputs: separated_list!(punct!(","), fn_arg) ~
        punct!(")") ~
        output: opt!(preceded!(
            punct!("->"),
            ty
        )),
        move || Ty::BareFn(Box::new(BareFnTy {
            lifetimes: lifetimes,
            decl: FnDecl {
                inputs: inputs,
                output: match output {
                    Some(ty) => FunctionRetTy::Ty(ty),
                    None => FunctionRetTy::Default,
                },
            },
        }))
    )
    |
    punct!("!") => { |_| Ty::Never }
    |
    delimited!(
        punct!("("),
        separated_list!(punct!(","), ty),
        punct!(")")
    ) => { Ty::Tup }
    |
    path => { |p| Ty::Path(None, p) }
    |
    chain!(
        punct!("<") ~
        this: map!(ty, Box::new) ~
        path: opt!(preceded!(
            tuple!(punct!("as"), space),
            path
        )) ~
        punct!(">") ~
        punct!("::") ~
        rest: separated_nonempty_list!(punct!("::"), path_segment),
        move || {
            match path {
                Some(mut path) => {
                    let pos = path.segments.len();
                    path.segments.extend(rest);
                    Ty::Path(Some(QSelf { ty: this, position: pos }), path)
                }
                None => {
                    Ty::Path(Some(QSelf { ty: this, position: 0 }), Path {
                        global: false,
                        segments: rest,
                    })
                }
            }
        }
    )
    |
    preceded!(
        tuple!(punct!("impl"), space),
        separated_nonempty_list!(punct!("+"), ty_param_bound)
    ) => { Ty::ImplTrait }
    |
    delimited!(
        punct!("("),
        ty,
        punct!(")")
    ) => { |inner| Ty::Paren(Box::new(inner)) }
));

named!(struct_field<&str, Field>, chain!(
    attrs: many0!(attribute) ~
    vis: visibility ~
    ident: word ~
    punct!(":") ~
    ty: ty,
    move || Field {
        ident: Some(ident),
        vis: vis,
        attrs: attrs,
        ty: ty,
    }
));

named!(tuple_field<&str, Field>, chain!(
    attrs: many0!(attribute) ~
    vis: visibility ~
    ty: ty,
    move || Field {
        ident: None,
        vis: vis,
        attrs: attrs,
        ty: ty,
    }
));

named!(struct_like_body<&str, Vec<Field> >, chain!(
    punct!("{") ~
    fields: separated_list!(punct!(","), struct_field) ~
    punct!(",")? ~
    punct!("}"),
    move || fields
));

named!(tuple_like_body<&str, Vec<Field> >, chain!(
    punct!("(") ~
    fields: separated_list!(punct!(","), tuple_field) ~
    punct!(",")? ~
    punct!(")"),
    move || fields
));

named!(struct_body<&str, (Style, Vec<Field>)>, alt!(
    struct_like_body => { |fields| (Style::Struct, fields) }
    |
    terminated!(tuple_like_body, punct!(";")) => { |fields| (Style::Tuple, fields) }
    |
    punct!(";") => { |_| (Style::Unit, Vec::new()) }
));

named!(variant<&str, Variant>, chain!(
    attrs: many0!(attribute) ~
    ident: word ~
    body: alt!(
        struct_like_body => { |fields| (Style::Struct, fields) }
        |
        tuple_like_body => { |fields| (Style::Tuple, fields) }
        |
        epsilon => { |_| (Style::Unit, Vec::new()) }
    ),
    move || Variant {
        ident: ident,
        attrs: attrs,
        style: body.0,
        fields: body.1,
    }
));

named!(enum_body<&str, Body>, chain!(
    punct!("{") ~
    variants: separated_list!(punct!(","), variant) ~
    punct!(",")? ~
    punct!("}"),
    move || Body::Enum(variants)
));

named!(lifetime<&str, Lifetime>, preceded!(
    punct!("'"),
    map!(word, |ident| Lifetime { ident: ident })
));

named!(bound_lifetimes<&str, Vec<LifetimeDef> >, opt_vec!(chain!(
    punct!("for") ~
    punct!("<") ~
    lifetimes: separated_list!(punct!(","), lifetime_def) ~
    punct!(">"),
    move || lifetimes
)));

named!(poly_trait_ref<&str, PolyTraitRef>, chain!(
    bound_lifetimes: bound_lifetimes ~
    trait_ref: path,
    move || PolyTraitRef {
        bound_lifetimes: bound_lifetimes,
        trait_ref: trait_ref,
    }
));

named!(ty_param_bound<&str, TyParamBound>, alt!(
    tuple!(punct!("?"), punct!("Sized")) => { |_| TyParamBound::MaybeSized }
    |
    lifetime => { TyParamBound::Region }
    |
    poly_trait_ref => { TyParamBound::Trait }
));

named!(where_predicate<&str, WherePredicate>, alt!(
    chain!(
        ident: lifetime ~
        punct!(":") ~
        bounds: separated_nonempty_list!(punct!("+"), lifetime),
        move || WherePredicate::RegionPredicate(WhereRegionPredicate {
            lifetime: ident,
            bounds: bounds,
        })
    )
    |
    chain!(
        bound_lifetimes: bound_lifetimes ~
        bounded_ty: ty ~
        punct!(":") ~
        bounds: separated_nonempty_list!(punct!("+"), ty_param_bound),
        move || WherePredicate::BoundPredicate(WhereBoundPredicate {
            bound_lifetimes: bound_lifetimes,
            bounded_ty: bounded_ty,
            bounds: bounds,
        })
    )
));

named!(lifetime_def<&str, LifetimeDef>, chain!(
    life: lifetime ~
    bounds: opt_vec!(preceded!(
        punct!(":"),
        separated_nonempty_list!(punct!(","), lifetime)
    )),
    move || LifetimeDef {
        lifetime: life,
        bounds: bounds,
    }
));

named!(ty_param<&str, TyParam>, chain!(
    ident: word ~
    bounds: opt_vec!(preceded!(
        punct!(":"),
        separated_nonempty_list!(punct!("+"), ty_param_bound)
    )) ~
    default: opt!(preceded!(
        punct!("="),
        ty
    )) ~
    move || TyParam {
        ident: ident,
        bounds: bounds,
        default: default,
    }
));

named!(generics<&str, Generics>, chain!(
    bracketed: alt!(
        chain!(
            punct!("<") ~
            lifetimes: separated_list!(punct!(","), lifetime_def) ~
            ty_params: opt_vec!(preceded!(
                cond!(!lifetimes.is_empty(), punct!(",")),
                separated_nonempty_list!(punct!(","), ty_param)
            )) ~
            punct!(">"),
            move || (lifetimes, ty_params)
        )
        |
        epsilon => { |_| (Vec::new(), Vec::new()) }
    ) ~
    where_clause: opt_vec!(chain!(
        punct!("where") ~
        space ~
        predicates: separated_nonempty_list!(punct!(","), where_predicate) ~
        punct!(",")? ~
        move || predicates
    )),
    move || Generics {
        lifetimes: bracketed.0,
        ty_params: bracketed.1,
        where_clause: where_clause,
    }
));

named!(item<&str, Item>, chain!(
    attrs: many0!(attribute) ~
    vis: visibility ~
    which: alt!(tag_s!("struct") | tag_s!("enum")) ~
    space ~
    ident: word ~
    generics: generics ~
    item: switch!(value!(which),
        "struct" => map!(struct_body, move |(style, fields)| Item {
            ident: ident,
            vis: vis,
            attrs: attrs,
            generics: generics,
            body: Body::Struct(style, fields),
        })
        |
        "enum" => map!(enum_body, move |body| Item {
            ident: ident,
            vis: vis,
            attrs: attrs,
            generics: generics,
            body: body,
        })
    ) ~
    space?,
    move || item
));

pub fn parse(input: &str) -> Item {
    match item(input) {
        IResult::Done(rest, ast) => {
            if rest.is_empty() {
                ast
            } else {
                panic!("more than a single input item: {:?}", rest)
            }
        }
        IResult::Error(err) => raise(err),
        IResult::Incomplete(_) => panic!("incomplete input item"),
    }
}

fn raise(mut err: nom::Err<&str>) -> ! {
    loop {
        match err {
            nom::Err::Code(kind) => {
                panic!("failed to parse {:?}", kind)
            }
            nom::Err::Position(kind, pos) => {
                panic!("failed to parse {:?}: {:?}", kind, pos)
            }
            nom::Err::Node(_, next) |
            nom::Err::NodePosition(_, _, next) => {
                err = *next;
            }
        }
    }
}