fix(derive): restore support for inline generic type constraints

Cargo.toml

@@ -100,7 +100,7 @@ libp2p-rendezvous = { version = "0.14.0", path = "protocols/rendezvous" }
 libp2p-request-response = { version = "0.26.1", path = "protocols/request-response" }
 libp2p-server = { version = "0.12.5", path = "misc/server" }
 libp2p-swarm = { version = "0.44.1", path = "swarm" }
-libp2p-swarm-derive = { version = "=0.34.1", path = "swarm-derive" } # `libp2p-swarm-derive` may not be compatible with different `libp2p-swarm` non-breaking releases. E.g. `libp2p-swarm` might introduce a new enum variant `FromSwarm` (which is `#[non-exhaustive]`) in a non-breaking release. Older versions of `libp2p-swarm-derive` would not forward this enum variant within the `NetworkBehaviour` hierarchy. Thus the version pinning is required.
+libp2p-swarm-derive = { version = "=0.34.2", path = "swarm-derive" } # `libp2p-swarm-derive` may not be compatible with different `libp2p-swarm` non-breaking releases. E.g. `libp2p-swarm` might introduce a new enum variant `FromSwarm` (which is `#[non-exhaustive]`) in a non-breaking release. Older versions of `libp2p-swarm-derive` would not forward this enum variant within the `NetworkBehaviour` hierarchy. Thus the version pinning is required.
 libp2p-swarm-test = { version = "0.3.0", path = "swarm-test" }
 libp2p-tcp = { version = "0.41.0", path = "transports/tcp" }
 libp2p-tls = { version = "0.3.0", path = "transports/tls" }

swarm-derive/CHANGELOG.md

@@ -1,3 +1,8 @@
+## 0.34.2
+
+- Restore support for generic constraints on behaviours combined with `out_event` generated by `NetworkBehaviour` where no where clause is used.
+  See [PR 5003](https://github.com/libp2p/rust-libp2p/pull/5003).
+
 ## 0.34.1
 
 - Always forward all variants of `FromSwarm`.

swarm-derive/Cargo.toml

@@ -3,7 +3,7 @@ name = "libp2p-swarm-derive"
 edition = "2021"
 rust-version = { workspace = true }
 description = "Procedural macros of libp2p-swarm"
-version = "0.34.1"
+version = "0.34.2"
 authors = ["Parity Technologies <[email protected]>"]
 license = "MIT"
 repository = "https://github.com/libp2p/rust-libp2p"

swarm-derive/src/lib.rs

@@ -162,7 +162,7 @@ fn build_struct(ast: &DeriveInput, data_struct: &DataStruct) -> syn::Result<Toke
 
                     Some(quote! {
                         #[doc = #msg]
-                        #visibility enum #enum_name #ty_generics
+                        #visibility enum #enum_name #impl_generics
                             #where_clause
                         {
                             #(#enum_variants),*

swarm/tests/swarm_derive.rs

@@ -371,6 +371,91 @@ fn with_generics_mixed() {
     }
 }
 
+#[test]
+fn with_generics_constrained() {
+    use std::task::{Context, Poll};
+    trait Mark {}
+    struct Marked;
+    impl Mark for Marked {}
+
+    /// A struct with a generic constraint, for which we manually implement `NetworkBehaviour`.
+    #[allow(dead_code)]
+    struct Bar<A: Mark> {
+        a: A,
+    }
+
+    impl<A: Mark + 'static> NetworkBehaviour for Bar<A> {
+        type ConnectionHandler = dummy::ConnectionHandler;
+        type ToSwarm = void::Void;
+
+        fn handle_established_inbound_connection(
+            &mut self,
+            _: libp2p_swarm::ConnectionId,
+            _: libp2p_identity::PeerId,
+            _: &Multiaddr,
+            _: &Multiaddr,
+        ) -> Result<THandler<Self>, ConnectionDenied> {
+            Ok(dummy::ConnectionHandler)
+        }
+
+        fn handle_established_outbound_connection(
+            &mut self,
+            _: libp2p_swarm::ConnectionId,
+            _: libp2p_identity::PeerId,
+            _: &Multiaddr,
+            _: Endpoint,
+        ) -> Result<THandler<Self>, ConnectionDenied> {
+            Ok(dummy::ConnectionHandler)
+        }
+
+        fn on_swarm_event(&mut self, _event: FromSwarm) {}
+
+        fn on_connection_handler_event(
+            &mut self,
+            _: libp2p_identity::PeerId,
+            _: libp2p_swarm::ConnectionId,
+            _: THandlerOutEvent<Self>,
+        ) {
+        }
+
+        fn poll(
+            &mut self,
+            _: &mut Context<'_>,
+        ) -> Poll<libp2p_swarm::ToSwarm<Self::ToSwarm, THandlerInEvent<Self>>> {
+            Poll::Pending
+        }
+    }
+
+    /// A struct which uses the above, inheriting the generic constraint,
+    /// for which we want to derive the `NetworkBehaviour`.
+    #[allow(dead_code)]
+    #[derive(NetworkBehaviour)]
+    #[behaviour(prelude = "libp2p_swarm::derive_prelude")]
+    struct Foo1<A: Mark> {
+        bar: Bar<A>,
+    }
+
+    /// A struct which uses the above, inheriting the generic constraint,
+    /// for which we want to derive the `NetworkBehaviour`.
+    ///
+    /// Using a where clause instead of inline constraint.
+    #[allow(dead_code)]
+    #[derive(NetworkBehaviour)]
+    #[behaviour(prelude = "libp2p_swarm::derive_prelude")]
+    struct Foo2<A>
+    where
+        A: Mark,
+    {
+        bar: Bar<A>,
+    }
+
+    #[allow(dead_code)]
+    fn foo() {
+        require_net_behaviour::<Foo1<Marked>>();
+        require_net_behaviour::<Foo2<Marked>>();
+    }
+}
+
 #[test]
 fn custom_event_with_either() {
     use either::Either;