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use proc_macro2::Span;
use parse::{Lookahead1, Parse, ParseStream, Result};
pub trait Token: private::Sealed {
#[doc(hidden)]
fn peek(lookahead: &Lookahead1) -> bool;
#[doc(hidden)]
fn display() -> String;
}
mod private {
pub trait Sealed {}
}
#[macro_export]
#[cfg_attr(rustfmt, rustfmt_skip)]
macro_rules! Token {
(struct) => { $crate::token::Struct };
(enum) => { $crate::token::Enum };
(:) => { $crate::token::Colon };
(,) => { $crate::token::Comma };
}
macro_rules! define_token {
($token:tt $name:ident #[$doc:meta]) => {
#[$doc]
#[derive(Debug)]
pub struct $name(pub Span);
impl Token for $name {
fn peek(lookahead: &Lookahead1) -> bool {
::lookahead::is_token(lookahead, $token)
}
fn display() -> String {
concat!("`", $token, "`").to_owned()
}
}
impl private::Sealed for $name {}
};
}
macro_rules! define_keywords {
($($token:tt $name:ident #[$doc:meta])*) => {
$(
define_token!($token $name #[$doc]);
impl Parse for $name {
fn parse(input: ParseStream) -> Result<Self> {
parse_keyword(input, $token).map($name)
}
}
)*
};
}
macro_rules! define_punctuation {
($($token:tt $name:ident #[$doc:meta])*) => {
$(
define_token!($token $name #[$doc]);
impl Parse for $name {
fn parse(input: ParseStream) -> Result<Self> {
parse_punctuation(input, $token).map($name)
}
}
)*
};
}
define_keywords! {
"struct" Struct
"enum" Enum
}
define_punctuation! {
":" Colon
"," Comma
}
#[derive(Debug)]
pub struct Brace(pub Span);
fn parse_keyword(input: ParseStream, token: &str) -> Result<Span> {
input.step_cursor(|cursor| {
if let Some((ident, rest)) = cursor.ident() {
if ident == token {
return Ok((ident.span(), rest));
}
}
Err(cursor.error(format!("expected `{}`", token)))
})
}
fn parse_punctuation(input: ParseStream, token: &str) -> Result<Span> {
input.step_cursor(|cursor| {
if let Some((punct, rest)) = cursor.punct() {
if punct.as_char() == token.chars().next().unwrap() {
return Ok((punct.span(), rest));
}
}
Err(cursor.error(format!("expected `{}`", token)))
})
}