#[derive(Debug, FromField)]
#[darling(attributes(my_attribute))]
struct StructFieldReceiver {
    ident: Option<syn::Ident>,
    vis: syn::Visibility,
    ty: syn::Type,
    name: String,
    sql_type: SqlType,
}

#[derive(Debug, FromMeta)]
#[darling(rename_all = "lowercase")]
enum SqlType {
// omitted variants
    BigInt, Int, SmallInt, TinyInt, Bit,
    Float(Option<u8>),
    Decimal{
        p: Option<u8>,
        s: Option<u8>
    },
// omitted variants
}