bodega-macros 0.8.0

bodega proc macros
Documentation 
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use syn::{GenericArgument, Path, PathArguments, PathSegment, Type};

pub(crate) fn option_kind(ty: &Type) -> Option<&Type> {
    // https://stackoverflow.com/questions/55271857/how-can-i-get-the-t-from-an-optiont-when-using-syn
    fn extract_type_path(ty: &syn::Type) -> Option<&Path> {
        match *ty {
            syn::Type::Path(ref typepath) if typepath.qself.is_none() => Some(&typepath.path),
            _ => None,
        }
    }

    fn extract_option_segment(path: &Path) -> Option<&PathSegment> {
        let idents_of_path = path.segments.iter().fold(String::new(), |mut acc, v| {
            acc.push_str(&v.ident.to_string());
            acc.push('|');
            acc
        });
        ["Option|", "std|option|Option|", "core|option|Option|"]
            .into_iter()
            .find(|s| idents_of_path == *s)
            .and_then(|_| path.segments.last())
    }

    extract_type_path(ty)
        .and_then(|path| extract_option_segment(path))
        .and_then(|path_seg| {
            let type_params = &path_seg.arguments;
            // It should have only one angle-bracketed param ("<String>"):
            match *type_params {
                PathArguments::AngleBracketed(ref params) => params.args.first(),
                _ => None,
            }
        })
        .and_then(|generic_arg| match *generic_arg {
            GenericArgument::Type(ref ty) => Some(ty),
            _ => None,
        })
}