From 16d1265e17228384258abe7e05ddc2baa0cc899d Mon Sep 17 00:00:00 2001
From: David Tolnay <dtolnay@gmail.com>
Date: Sat, 19 May 2018 17:14:20 -0700
Subject: [PATCH] Fix generated code for deserializing untagged newtype variant

---
 serde_derive/src/de.rs       |  6 ++----
 test_suite/tests/test_gen.rs | 10 ++++++++++
 2 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/serde_derive/src/de.rs b/serde_derive/src/de.rs
index 40a5d105..3cce5f07 100644
--- a/serde_derive/src/de.rs
+++ b/serde_derive/src/de.rs
@@ -1802,10 +1802,8 @@ fn deserialize_untagged_newtype_variant(
         }
         Some(path) => {
             quote_block! {
-                let __value: #field_ty = _serde::export::Result::map(
-                    #path(#deserializer),
-                    #this::#variant_ident);
-                __value
+                let __value: _serde::export::Result<#field_ty, _> = #path(#deserializer);
+                _serde::export::Result::map(__value, #this::#variant_ident)
             }
         }
     }
diff --git a/test_suite/tests/test_gen.rs b/test_suite/tests/test_gen.rs
index 7888f2d8..ffb73210 100644
--- a/test_suite/tests/test_gen.rs
+++ b/test_suite/tests/test_gen.rs
@@ -643,6 +643,16 @@ fn test_gen() {
     struct ImpliciltyBorrowedOption<'a> {
         option: std::option::Option<&'a str>,
     }
+
+    #[derive(Serialize, Deserialize)]
+    #[serde(untagged)]
+    enum UntaggedNewtypeVariantWith {
+        Newtype(
+            #[serde(serialize_with = "ser_x")]
+            #[serde(deserialize_with = "de_x")]
+            X,
+        ),
+    }
 }
 
 //////////////////////////////////////////////////////////////////////////