network: clarify comment on Default for handshake::Builder
@@ -140,7 +140,9 @@ where
{
/// Create a builder that configures a [`Handshake`] service.
pub fn builder() -> Builder<S> {
- // can't derive Builder::default without a bound on S :(
+ // We don't derive `Default` because the derive inserts a `where S:
+ // Default` bound even though `Option<S>` implements `Default` even if
+ // `S` does not.
Builder {
config: None,
inbound_service: None,
