src/lit.rs

use std::fmt;
use std::hash::{Hash, Hasher};

use proc_macro2::{self, Literal, Span, Term, TokenNode, TokenTree};

#[derive(Clone)]
pub struct Lit {
    pub value: LitKind,
    pub span: Span,
}

#[derive(Clone)]
pub enum LitKind {
    Bool(bool),
    Other(Literal),
}

impl Lit {
    pub fn into_token_tree(self) -> TokenTree {
        let kind = match self.value {
            LitKind::Bool(true) => TokenNode::Term(Term::intern("true")),
            LitKind::Bool(false) => TokenNode::Term(Term::intern("false")),
            LitKind::Other(l) => TokenNode::Literal(l),
        };
        proc_macro2::TokenTree {
            span: self.span,
            kind: kind,
        }
    }
}

impl fmt::Display for Lit {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        fmt::Display::fmt(&self.value, f)
    }
}

impl fmt::Debug for Lit {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        fmt::Display::fmt(&self.value, f)
    }
}

impl PartialEq for Lit {
    fn eq(&self, other: &Lit) -> bool {
        self.value == other.value
    }
}

impl Eq for Lit {}

impl Hash for Lit {
    fn hash<H: Hasher>(&self, hasher: &mut H) {
        self.value.hash(hasher)
    }
}

impl fmt::Display for LitKind {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match *self {
            LitKind::Bool(b) => b.fmt(f),
            LitKind::Other(ref l) => l.fmt(f),
        }
    }
}

impl fmt::Debug for LitKind {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match *self {
            LitKind::Bool(b) => b.fmt(f),
            LitKind::Other(ref l) => fmt::Display::fmt(l, f),
        }
    }
}

impl PartialEq for LitKind {
    fn eq(&self, other: &LitKind) -> bool {
        match (self, other) {
            (&LitKind::Bool(b1), &LitKind::Bool(b2)) => b1 == b2,
            (&LitKind::Other(ref l1), &LitKind::Other(ref l2)) => l1.to_string() == l2.to_string(),
            _ => false,
        }
    }
}

impl Eq for LitKind {}

impl Hash for LitKind {
    fn hash<H: Hasher>(&self, hasher: &mut H) {
        match *self {
            LitKind::Bool(b) => (0u8, b).hash(hasher),
            LitKind::Other(ref l) => (1u8, l.to_string()).hash(hasher),
        }
    }
}

#[cfg(feature = "parsing")]
pub mod parsing {
    use super::*;
    use synom::Synom;
    use cursor::Cursor;
    use parse_error;
    use synom::PResult;

    impl Synom for Lit {
        fn parse(input: Cursor) -> PResult<Self> {
            match input.literal() {
                Some((rest, span, lit)) => Ok((
                    rest,
                    Lit {
                        span: span,
                        value: LitKind::Other(lit),
                    },
                )),
                _ => match input.word() {
                    Some((rest, span, sym)) => {
                        let kind = if sym.as_str() == "true" {
                            LitKind::Bool(true)
                        } else if sym.as_str() == "false" {
                            LitKind::Bool(false)
                        } else {
                            return parse_error();
                        };

                        Ok((
                            rest,
                            Lit {
                                span: span,
                                value: kind,
                            },
                        ))
                    }
                    _ => parse_error(),
                },
            }
        }

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

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

    impl ToTokens for Lit {
        fn to_tokens(&self, tokens: &mut Tokens) {
            self.clone().into_token_tree().to_tokens(tokens)
        }
    }
}