| 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 { |
| // Safety: This is safe because the caller of gen_transparent_convert |
| // adds a repr(transparent) to the struct. |
| unsafe { |
| &*(from as *const #field1 as *const Self) |
| } |
| } |
| } |
| } |
| } |
