Alternative API for set_isolation_group().

Instead of requiring a `Box<dyn Isolation>`, it now takes either a
`Box<dyn Isolation>`, or an arbitrary `T` that implements
`Isolation`.

This API still allows the user to pass in a `Box<dyn Isolation>` if
that's what they have, but it doesn't require them to Box the
isolation on their own.

Part of #414.

crates/arti-bench/src/main.rs

@@ -684,7 +684,7 @@ impl<R: Runtime> Benchmark<R> {
 
         self.run(BenchmarkType::Arti, |run| {
             let mut prefs = arti_client::StreamPrefs::new();
-            prefs.set_isolation_group(Box::new(iso.next_in(run)));
+            prefs.set_isolation_group(iso.next_in(run));
 
             tor_client.connect(addr.clone())
         })

crates/arti-client/src/client.rs

@@ -231,8 +231,11 @@ impl StreamPrefs {
     /// [`TorClient::isolated_client`].  Connections made with an `isolated_client` (and its
     /// clones) will not share circuits with the original client, even if the same
     /// `isolation_group` is specified via the `ConnectionPrefs` in force.
-    pub fn set_isolation_group(&mut self, isolation_group: Box<dyn Isolation>) -> &mut Self {
-        self.isolation = StreamIsolationPreference::Explicit(isolation_group);
+    pub fn set_isolation_group<T>(&mut self, isolation_group: T) -> &mut Self
+    where
+        T: Into<Box<dyn Isolation>>,
+    {
+        self.isolation = StreamIsolationPreference::Explicit(isolation_group.into());
         self
     }
 

crates/arti/src/dns.rs

@@ -69,7 +69,7 @@ where
     let mut answers = Vec::new();
 
     let mut prefs = StreamPrefs::new();
-    prefs.set_isolation_group(Box::new(DnsIsolationKey(socket_id, addr.ip())));
+    prefs.set_isolation_group(DnsIsolationKey(socket_id, addr.ip()));
 
     for query in query.queries() {
         let mut a = Vec::new();

crates/arti/src/socks.rs

@@ -176,7 +176,7 @@ See <a href="https://gitlab.torproject.org/tpo/core/arti/#todo-need-to-change-wh
 
     // Determine whether we want to ask for IPv4/IPv6 addresses.
     let mut prefs = stream_preference(&request, &addr);
-    prefs.set_isolation_group(Box::new(SocksIsolationKey(source_address, ip, auth)));
+    prefs.set_isolation_group(SocksIsolationKey(source_address, ip, auth));
 
     match request.command() {
         SocksCmd::CONNECT => {

crates/tor-circmgr/src/usage.rs

@@ -115,6 +115,11 @@ pub trait Isolation: Downcast + DynClone + std::fmt::Debug + Send + Sync + 'stat
 }
 impl_downcast!(Isolation);
 clone_trait_object!(Isolation);
+impl<T: Isolation> From<T> for Box<dyn Isolation> {
+    fn from(isolation: T) -> Self {
+        Box::new(isolation)
+    }
+}
 
 impl<T: IsolationHelper + Clone + std::fmt::Debug + Send + Sync + 'static> Isolation for T {
     fn compatible(&self, other: &dyn Isolation) -> bool {