From 6fb82e13b90b7c5362e69cb542a13eb9b25b9e49 Mon Sep 17 00:00:00 2001
From: naskya <m@naskya.net>
Date: Tue, 16 Jul 2024 02:11:16 +0900
Subject: [PATCH] fix: incorrect merge logic

---
 crates/relax-macros/src/lib.rs | 23 +++++++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/crates/relax-macros/src/lib.rs b/crates/relax-macros/src/lib.rs
index e2d2710..f21baaf 100644
--- a/crates/relax-macros/src/lib.rs
+++ b/crates/relax-macros/src/lib.rs
@@ -137,7 +137,7 @@ fn derive_impl(input: syn::DeriveInput) -> syn::Result<TokenStream> {
 
             if field.attrs.iter().any(|attr| attr.path().is_ident("relax")) {
                 // nested
-                Ok(quote! { #vis #name: ::std::option::Option<<#ty as ::relax::Relax>::Partial> })
+                Ok(quote! { #vis #name: ::std::option::Option<<#ty as Relax>::Partial> })
             } else {
                 // not nested
                 match get_generic_ty("Option", ty) {
@@ -176,10 +176,25 @@ fn derive_impl(input: syn::DeriveInput) -> syn::Result<TokenStream> {
         })
     }).collect::<syn::Result<Vec<_>>>()?;
 
-    let merge_fields = fields.iter().map(|field| {
+    let merge_fields = fields.iter().map(|field| -> syn::Result<TokenStream> {
         let name = field.ident.as_ref();
-        quote! { #name: self.#name.or(optb.#name) }
-    });
+        let nested = field
+            .attrs
+            .iter()
+            .any(|attr| attr.path().is_ident("relax"));
+
+        Ok(match nested {
+            false => quote! { #name: self.#name.or(optb.#name) },
+            true => quote! {
+                #name: match (self.#name, optb.#name) {
+                    (::std::option::Option::Some(a), ::std::option::Option::None) => ::std::option::Option::Some(a),
+                    (::std::option::Option::None, ::std::option::Option::Some(b)) => ::std::option::Option::Some(b),
+                    (::std::option::Option::None, ::std::option::Option::None) => ::std::option::Option::None,
+                    (::std::option::Option::Some(a), ::std::option::Option::Some(b)) => ::std::option::Option::Some(a.merge(b)),
+                }
+            }
+        })
+    }).collect::<syn::Result<Vec<_>>>()?;
 
     Ok(quote! {
         #(#extra_attrs)*