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use quote::quote;
use syn::*;
pub fn gen_transparent_convert(s: ItemStruct) -> proc_macro2::TokenStream {
let mut fields = s.fields.iter();
let field1 = if let Some(field1) = fields.next() {
&field1.ty
} else {
panic!("#[diplomat::transparent_convert] only allowed on structs with a single field")
};
if fields.next().is_some() {
panic!("#[diplomat::transparent_convert] only allowed on structs with a single field")
}
let struct_name = &s.ident;
let (impl_generics, ty_generics, _) = s.generics.split_for_impl();
let mut impl_generics: Generics = parse_quote!(#impl_generics);
let custom_lifetime: GenericParam = parse_quote!('transparent_convert_outer);
impl_generics.params.push(custom_lifetime);
quote! {
impl #impl_generics #struct_name #ty_generics {
// can potentially add transparent_convert_owned, _mut later
pub(crate) fn transparent_convert(from: &'transparent_convert_outer #field1) -> &'transparent_convert_outer Self {
unsafe {
&*(from as *const #field1 as *const Self)
}
}
}
}
}