Spurious ambiguous reference error in Scala 2.7.7 compiler/interpreter?

Question

Can anyone explain the compile error below? Interestingly, if I change the return type of the get() method to String, the code compiles just fine. Note that the thenReturn method has two overloads: a unary method and a varargs method that takes at least one argument. It seems to me that if the invocation is ambiguous here, then it would always be ambiguous.

More importantly, is there any way to resolve the ambiguity?

import org.scalatest.mock.MockitoSugar
import org.mockito.Mockito._

trait Thing { 
   def get(): java.lang.Object 
}

new MockitoSugar {   
   val t = mock[Thing]  

   when(t.get()).thenReturn("a")  
}

error: ambiguous reference to overloaded definition, both method thenReturn in trait OngoingStubbing of type
java.lang.Object,java.lang.Object*)org.mockito.stubbing.OngoingStubbing[java.lang.Object] and method thenReturn in trait OngoingStubbing of type (java.lang.Object)org.mockito.stubbing.OngoingStubbing[java.lang.Object] match argument types (java.lang.String) when(t.get()).thenReturn("a")

Answer 1

I had a similar problem using Oval (oval.sf.net) trying to call it's validate()-method.

Oval defines 2 validate() methods:

public List<ConstraintViolation> validate(final Object validatedObject)
public List<ConstraintViolation> validate(final Object validatedObject, final String... profiles)

Trying this from Scala: validator.validate(value) produces the following compiler-error:

both method validate in class Validator of type (x$1: Any,x$2: <repeated...>[java.lang.String])java.util.List[net.sf.oval.ConstraintViolation]                                                          
and  method validate in class Validator of type (x$1: Any)java.util.List[net.sf.oval.ConstraintViolation]                                                                                               
match argument types (T)                                                                                                                                                                                
        var violations = validator.validate(entity);                                                                                                                                                    

Oval needs the varargs-parameter to be null, not an empty-array, so I finally got it to work with this:

validator.validate(value, null.asInstanceOf[Array[String]]: _*)