Argument for implicit parameter sender was supplied using a default argument: 3.3.7-RC1

[He-Pin]

Compiler version

3.3.7-RC1

Minimized code

https://github.com/apache/pekko/actions/runs/17338073097/job/49227565939?pr=2104

  final def scheduleOnce(delay: FiniteDuration, receiver: ActorRef, message: Any)(
      implicit
      executor: ExecutionContext,
      sender: ActorRef = Actor.noSender): Cancellable

Output

[error] -- [E220] Type Error: /home/runner/work/pekko/pekko/actor-tests/src/test/scala/org/apache/pekko/actor/SupervisorHierarchySpec.scala:242:70 
[error] 242 |        context.system.scheduler.scheduleOnce(1.second, self, Dump(0))(context.dispatcher)
[error]     |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[error]     |Argument for implicit parameter sender was supplied using a default argument.
[error]     |
[error]     | longer explanation available when compiling with `-explain`

Expectation

Compiles ok
refs: #23559

The implicit ActorRef is from the Actor where:

  /**
   * The 'self' field holds the ActorRef for this actor.
   * <p/>
   * Can be used to send messages to itself:
   * <pre>
   * self ! message
   * </pre>
   */
  implicit final val self: ActorRef = context.self // MUST BE A VAL, TRUST ME

And then, when using the method inside the Actor, this will cause an error. I think the value should be bound to self and no warning.

[He-Pin]

@som-snytt FYI.

[som-snytt]

@He-Pin an explicit application uses default args in preference to implicits in scope.

def ov(i: Int)(implicit s: String, j: Int = 1) = s * (i + j)
def ov(s: String) = s

then

  locally:
    given Int = 2 // same with implicit val myInt: Int = 2
    println(ov(10)("x"))

uses the default arg

            final lazy given val given_Int: Int = 2
            println(ov(10)("x", i23541$package.ov$default$3(10)))

This is a unit test on release-3.3.7. 3.7.x will say that it should be ov(10)(using "x").

Are you sure your test code isn't using the default arg?

[He-Pin]

hum, unexpected behavior!!!

def ov(i: Int)(implicit s: String, j: Int = 1) = s * (i + j)
def ov(s: String) = s

implicit val x:Int = 100

println(ov(10)("x"))

only gives : xxxxxxxxxxx

[He-Pin]

@som-snytt Thanks, I will update the code then, really unexpected!

[som-snytt]

@He-Pin I'll also add a test for overloading!

I agree the behavior is subtle and hard to spot.