changes to generic params to make everything backward compatible

Author: mlowicki

src/producer/base_producer.rs

@@ -443,7 +443,7 @@ where
     }
 }
 
-impl<C, Part> Producer<Part, C> for BaseProducer<C, Part>
+impl<C, Part> Producer<C, Part> for BaseProducer<C, Part>
 where
     Part: Partitioner,
     C: ProducerContext<Part>,
@@ -659,7 +659,7 @@ where
     }
 }
 
-impl<C, Part> Producer<Part, C> for ThreadedProducer<C, Part>
+impl<C, Part> Producer<C, Part> for ThreadedProducer<C, Part>
 where
     Part: Partitioner,
     C: ProducerContext<Part> + 'static,

src/producer/future_producer.rs

@@ -371,7 +371,7 @@ where
     }
 }
 
-impl<C, R, Part> Producer<Part, FutureProducerContext<C>> for FutureProducer<C, R, Part>
+impl<C, R, Part> Producer<FutureProducerContext<C>, Part> for FutureProducer<C, R, Part>
 where
     C: ClientContext + 'static,
     R: AsyncRuntime,

src/producer/mod.rs

@@ -267,7 +267,7 @@ impl ProducerContext<NoCustomPartitioner> for DefaultProducerContext {
 }
 
 /// Common trait for all producers.
-pub trait Producer<Part, C = DefaultProducerContext>
+pub trait Producer<C = DefaultProducerContext, Part = NoCustomPartitioner>
 where
     Part: Partitioner,
     C: ProducerContext<Part>,