async-trait-sync 0.1.57

Fork of async-trait with support to Sync future
Documentation 
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use proc_macro2::Span;
use syn::parse::{Error, Parse, ParseStream, Result};
use syn::Token;

#[derive(Copy, Clone)]
pub struct Args {
    pub local: bool,
    pub sync: bool,
}

mod kw {
    syn::custom_keyword!(Send);
    syn::custom_keyword!(Sync);
}

impl Parse for Args {
    fn parse(input: ParseStream) -> Result<Self> {
        match try_parse(input) {
            Ok(args) if input.is_empty() => Ok(args),
            _ => Err(error()),
        }
    }
}

fn try_parse(input: ParseStream) -> Result<Args> {
    if input.peek(Token![?]) {
        input.parse::<Token![?]>()?;
        input.parse::<kw::Send>()?;
        Ok(Args {
            local: true,
            sync: false,
        })
    } else if input.peek(Token![+]) {
        input.parse::<Token![+]>()?;
        input.parse::<kw::Sync>()?;
        Ok(Args {
            local: false,
            sync: true,
        })
    } else {
        Ok(Args {
            local: false,
            sync: false,
        })
    }
}

fn error() -> Error {
    let msg = "expected #[async_trait] or #[async_trait(?Send)]";
    Error::new(Span::call_site(), msg)
}