From cb2b92f828c48edf714350815ffa984b8aa4ad31 Mon Sep 17 00:00:00 2001
From: David Tolnay <dtolnay@gmail.com>
Date: Tue, 1 May 2018 22:25:06 -0700
Subject: [PATCH] Handle flatten + deserialize_with

---
 serde_derive/src/de.rs       | 6 +++++-
 test_suite/tests/test_gen.rs | 7 +++++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/serde_derive/src/de.rs b/serde_derive/src/de.rs
index e08a1fcf..af3d3693 100644
--- a/serde_derive/src/de.rs
+++ b/serde_derive/src/de.rs
@@ -2279,8 +2279,12 @@ fn deserialize_map(
         .filter(|&&(field, _)| field.attrs.flatten())
         .map(|&(field, ref name)| {
             let field_ty = field.ty;
+            let func = match field.attrs.deserialize_with() {
+                None => quote!(_serde::de::Deserialize::deserialize),
+                Some(path) => quote!(#path),
+            };
             quote! {
-                let #name: #field_ty = try!(_serde::de::Deserialize::deserialize(
+                let #name: #field_ty = try!(#func(
                     _serde::private::de::FlatMapDeserializer(
                         &mut __collect,
                         _serde::export::PhantomData)));
diff --git a/test_suite/tests/test_gen.rs b/test_suite/tests/test_gen.rs
index 2a78fcf7..e06ec5a8 100644
--- a/test_suite/tests/test_gen.rs
+++ b/test_suite/tests/test_gen.rs
@@ -492,6 +492,13 @@ fn test_gen() {
     }
     assert_ser::<UntaggedVariantWith>();
 
+    #[derive(Serialize, Deserialize)]
+    struct FlattenWith {
+        #[serde(flatten, serialize_with = "ser_x", deserialize_with = "de_x")]
+        x: X,
+    }
+    assert::<FlattenWith>();
+
     #[derive(Serialize, Deserialize)]
     struct StaticStrStruct<'a> {
         a: &'a str,