Don't use "=>" for void methods in delegates.

lib/src/delegate/sink.dart

Index: lib/src/delegate/sink.dart
diff --git a/lib/src/delegate/sink.dart b/lib/src/delegate/sink.dart
index 5cf4f563adf0956274f4ba7024d763a80431e02b..bb50da33972521ff47578bf255566f0262c683ee 100644
--- a/lib/src/delegate/sink.dart
+++ b/lib/src/delegate/sink.dart
@@ -15,7 +15,11 @@ class DelegatingSink<T> implements Sink<T> {
   DelegatingSink(Sink sink)
       : _sink = sink;
 
-  void add(T data) => _sink.add(data);
+  void add(T data) {
+    _sink.add(data);
+  }
 
-  void close() => _sink.close();
+  void close() {
+    _sink.close();
+  }
 }