From 615dd3332fd4d14d9f41ffa69ee4beb841aece98 Mon Sep 17 00:00:00 2001
From: Dan Robertson <dan@dlrobertson.com>
Date: Mon, 21 Jan 2019 10:56:01 +0000
Subject: [PATCH] derive(NetworkBehaviour) handles trailing commas (#874)

Properly handle trailing commas in derive(NetworkBehaviour)
---
 misc/core-derive/src/lib.rs    | 6 +++++-
 misc/core-derive/tests/test.rs | 6 ++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/misc/core-derive/src/lib.rs b/misc/core-derive/src/lib.rs
index 0a423b18..79a551a5 100644
--- a/misc/core-derive/src/lib.rs
+++ b/misc/core-derive/src/lib.rs
@@ -112,7 +112,11 @@ fn build_struct(ast: &DeriveInput, data_struct: &DataStruct) -> TokenStream {
         additional.push(quote!{#substream_generic: ::libp2p::tokio_io::AsyncWrite});
 
         if let Some(where_clause) = where_clause {
-            Some(quote!{#where_clause, #(#additional),*})
+            if where_clause.predicates.trailing_punct() {
+                Some(quote!{#where_clause #(#additional),*})
+            } else {
+                Some(quote!{#where_clause, #(#additional),*})
+            }
         } else {
             Some(quote!{where #(#additional),*})
         }
diff --git a/misc/core-derive/tests/test.rs b/misc/core-derive/tests/test.rs
index 0f90baf6..98073e94 100644
--- a/misc/core-derive/tests/test.rs
+++ b/misc/core-derive/tests/test.rs
@@ -205,6 +205,12 @@ fn where_clause() {
         ping: libp2p::ping::Ping<TSubstream>,
     }
 
+    #[allow(dead_code)]
+    #[derive(NetworkBehaviour)]
+    struct Baz<TSubstream> where TSubstream: std::fmt::Debug + Clone, {
+        ping: libp2p::ping::Ping<TSubstream>,
+    }
+
     #[allow(dead_code)]
     #[derive(NetworkBehaviour)]
     struct Qux<TSubstream: std::fmt::Debug> where TSubstream: Clone {