False negative: change in default parameter type

[dwijnand]

Version 1

package t

final class Foo(x: Int, y: String) {
  def copy(x: Int = x, y: String = y) = new Foo(x, y)
}

Version 2

package t

final class Foo(z: Boolean = false, x: Int, y: String) {
  def this(x: Int, y: String) = this(false, x, y)
  def copy(x: Int, y: String) = new Foo(z, x, y)
  def copy(z: Boolean = z, x: Int = x, y: String = y) = new Foo(z, x, y)
}

Client

package t

object T {
  def main(args: Array[String]): Unit = {
    val x = new Foo(1, "a")
    val y = x.copy(y = "b")
    println(y)
  }
}

Error

t: found 0 potential binary incompatibilities while checking against com.dwijnand:t_2.12:0.1.0

java.lang.NoSuchMethodError: t.Foo.copy$default$1()I
	at t.T$.main(T.scala:6)
	at t.T.main(T.scala)

Note

See sbt/contraband#48 for more context.

[szeiger]

Looks like we shouldn't ignore the synthetic accessors for default values. AFAIR synthetic accessors are generally ignored because they cannot be called across compilation units but this is not the case here.

[jvican]

I would be happy to fix this in the upcoming days.

[szeiger]

@jvican Are you working on this or should I take a closer look? (I'd expect a fix to be pretty much along the lines of #144)

[jvican]

@szeiger Go ahead, I didn't start my fix. 😉