[FLINK-3563] .returns() doesn't compile when using .map() with a custom MapFunction

• Type: Bug
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 0.10.1
• Fix Version/s: 1.0.1, 1.1.0
• Component/s: API / Type Serialization System
• Assignee: Timo Walther
• Reporter: Simone Robutti
• Created: 02/Mar/16 11:16
• Updated: 14/Mar/16 12:47
• Resolved: 14/Mar/16 12:47

Description

Defined a DummyMapFunction that goes from a java Map to another java Map like this:

DummyMapFunction.scalaborderStyle=solid

class DummyMapFunction() extends MapFunction[java.util.Map[String, Any], java.util.Map[FieldName, Any]] {
  override def map(input: java.util.Map[String, Any]): java.util.Map[FieldName, Any] = {
    val result: java.util.Map[FieldName, Any] = new java.util.HashMap[FieldName, Any]()
    result
  }
}

and trying to use it with a map:

Main.java

DummyMapFunction operator = new DummyMapFunction();

DataSource<Map<String, Object>> dataset = env.fromCollection(input);
        List<java.util.Map<FieldName, Object>> collectedResult = dataset.map(operator).returns(java.util.Map.class).collect();

the returns call doesn't compile because it can't resolve the returns method with the parameter.

But if insted of creating a variable of type DummyMapFunction I create a

MapFunction operator=new DummyMapFuction();

or I explicitly cast the variable to a MapFunction, it compiles and work flawlessly.

This is a trick that works but I think is an unexpected behaviour.