From a0186f4a6373c00ca5e9f20eb0927640f54ca23b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sosth=C3=A8ne=20Gu=C3=A9don?= <sosthene@nitrokey.com>
Date: Fri, 24 Nov 2023 15:51:59 +0100
Subject: [PATCH] Keep full generics data

---
 src/lib.rs   | 15 +++++++++------
 src/parse.rs | 12 +++---------
 2 files changed, 12 insertions(+), 15 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index 92ab0a6..dc70d15 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -32,7 +32,7 @@ mod parse;
 
 use proc_macro::TokenStream;
 use quote::{format_ident, quote};
-use syn::parse_macro_input;
+use syn::{parse_macro_input, Lifetime, LifetimeParam};
 
 use crate::parse::Input;
 
@@ -85,10 +85,11 @@ pub fn derive_serialize(input: TokenStream) -> TokenStream {
     let ident = input.ident;
     let num_fields = count_serialized_fields(&input.fields);
     let serialize_fields = serialize_fields(&input.fields, input.attrs.offset);
-    let lifetimes = &input.lifetimes;
+    let lifetimes_imp = input.generics.lifetimes();
+    let lifetimes_ty = input.generics.lifetimes();
 
     TokenStream::from(quote! {
-        impl<#(#lifetimes),*> serde::Serialize for #ident<#(#lifetimes),*> {
+        impl<#(#lifetimes_imp),*> serde::Serialize for #ident<#(#lifetimes_ty),*> {
             fn serialize<S>(&self, serializer: S) -> core::result::Result<S::Ok, S::Error>
             where
                 S: serde::Serializer
@@ -168,7 +169,8 @@ fn all_fields(fields: &[parse::Field]) -> Vec<proc_macro2::TokenStream> {
         .collect()
 }
 
-fn de_lifetime(lifetimes: &[syn::Lifetime]) -> proc_macro2::TokenStream {
+fn de_lifetime<'a>(lifetimes: impl Iterator<Item = &'a LifetimeParam>) -> proc_macro2::TokenStream {
+    let lifetimes = lifetimes.map(|l| &l.lifetime);
     quote! {
         'de: #(#lifetimes)+*
     }
@@ -182,8 +184,9 @@ pub fn derive_deserialize(input: TokenStream) -> TokenStream {
     let unwrap_expected_fields = unwrap_expected_fields(&input.fields);
     let match_fields = match_fields(&input.fields, input.attrs.offset);
     let all_fields = all_fields(&input.fields);
-    let de_lifetime = de_lifetime(&input.lifetimes);
-    let lifetimes = input.lifetimes;
+    let de_lifetime = de_lifetime(input.generics.lifetimes());
+    let lifetimes: Vec<_> = input.generics.lifetimes().collect();
+    let lifetimes = &*lifetimes;
 
     let the_loop = if !input.fields.is_empty() {
         // NB: In the previous "none_fields", we use the actual struct's
diff --git a/src/parse.rs b/src/parse.rs
index 5528fce..3255dc4 100644
--- a/src/parse.rs
+++ b/src/parse.rs
@@ -1,13 +1,13 @@
 use proc_macro2::Span;
 use syn::meta::ParseNestedMeta;
 use syn::parse::{Error, Parse, ParseStream, Result};
-use syn::{Data, DeriveInput, Fields, Ident, Lifetime, LitInt, LitStr, Token};
+use syn::{Data, DeriveInput, Fields, Generics, Ident, LitInt, LitStr, Token};
 
 pub struct Input {
     pub ident: Ident,
     pub attrs: StructAttrs,
     pub fields: Vec<Field>,
-    pub lifetimes: Vec<Lifetime>,
+    pub generics: Generics,
 }
 
 #[derive(Default)]
@@ -54,10 +54,6 @@ fn parse_attrs(attrs: &Vec<syn::Attribute>) -> Result<StructAttrs> {
     Ok(struct_attrs)
 }
 
-fn lifetimes(generics: &syn::Generics) -> Vec<Lifetime> {
-    generics.lifetimes().map(|l| l.lifetime.clone()).collect()
-}
-
 impl Parse for Input {
     fn parse(input: ParseStream) -> Result<Self> {
         let call_site = Span::call_site();
@@ -81,15 +77,13 @@ impl Parse for Input {
 
         let fields = fields_from_ast(&syn_fields.named)?;
 
-        let lifetimes = lifetimes(&derive_input.generics);
-
         //serde::internals::ast calls `fields_from_ast(cx, &fields.named, attrs, container_default)`
 
         Ok(Input {
             ident: derive_input.ident,
             attrs,
             fields,
-            lifetimes,
+            generics: derive_input.generics,
         })
     }
 }