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Error when implementing java varargs method on anonymous type with explicit type #4729

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scabug opened this issue Jun 22, 2011 · 5 comments
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@scabug
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scabug commented Jun 22, 2011

I've got a compiler error when trying to implement a java interface which has a method with vararg parameter using a anonymous class. It is strange 'cause it only happens when i explicit define its type. See example bellow:

// Java Interface: 
public interface VarArgs {
  public void method(String... s);
} 
 
// Scala class: 
class ScalaVarArgs extends VarArgs { 
  // -- no problem on overriding it using ordinary class 
  def method(s: String*) { println(s) } 
} 

object ScalaVarArgs { 
  def main(args: Array[String]) { 
    //[1] Ok - no problem using inferred type 
    val varArgs = new VarArgs { 
      def method(s: String*) { println(s) } 
    } 
    varArgs.method("1", "2") 

    //[2] Ok -- no problem when explicit set its type after construction
    val b: VarArgs = varArgs 
    b.method("1", "2") 
    
    //[3] Ok -- no problem on calling its method
    (new ScalaVarArgs).method("1", "2") 
    (new ScalaVarArgs: VarArgs).method("1", "2") 
    
    //[4] Not Ok -- error when assigning anonymous class to a explictly typed val
    // Compiler error:  object creation impossible, since method method in trait VarArgs of type (s: <repeated...>[java.lang.String])Unit is not defined 
    val tagged: VarArgs = new VarArgs { 
      def method(s: String*) { println(s) } 
    } 
  } 
} 

Note: this error/doubt was original post at scala-users mail list: http://groups.google.com/group/scala-user/browse_thread/thread/85757cea2cd25069/27817e912c89a6f5?lnk=gst&q=fabio.veronez#27817e912c89a6f5

@scabug
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scabug commented Jun 22, 2011

Imported From: https://issues.scala-lang.org/browse/SI-4729?orig=1
Reporter: Fabio (fabio.veronez)

@scabug
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scabug commented Mar 12, 2012

Sarah Gerweck (gerweck) said:
I am encountering this exact same bug in Scala 2.9.1 final. It's quite an annoying issue!

@scabug
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scabug commented Oct 1, 2012

Alexandre Cardoso (accbel) said:
Same error when trying following case

class A {
  def otherMethod(arg: VarArgs) {
    //A piece of code
  }
}

// Not Ok -- error when assigning anonymous class as a method parameter
// Compiler error:  object creation impossible, since method method in trait VarArgs of type (s: <repeated...>[java.lang.String])Unit is not defined
new A().otherMethod(new VarArgs {
  def method(s: String*) { println(s) }
}

@scabug
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scabug commented Oct 1, 2012

@paulp said:
I submitted a fix a couple days ago; it's not merged yet. scala/scala#1430

@scabug
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scabug commented Jan 23, 2013

@adriaanm said:
fixed for 2.11 in paulp/scala@32e70a0 -- potential backport pending

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