Given conversion loosing type, when inlined

[edolgy]

The code does not compile, but would compile if 'inline' is removed.

Introduced in 0.22, was fine in 0.21

object NOTHING

inline given [A]: Conversion[NOTHING.type, Option[A]] = _ => None

def apply[A](p: Vector[A], o: Option[A] = NOTHING): Unit = ???

apply[String](Vector.empty)

[error]  Found: Option[Any],  Required: Option[String]

[odersky]

It works fine if I give the default argument explicitly:

apply[String](Vector.empty, NOTHING)

There's a little too much going on here at the same time. To rely on an implicit conversion to make a default argument conform to the indicated type is a bit crazy. The problem might go away by itself if we redesign default arguments. Until then it's better to wait.

[nicolasstucki]

Workaround

object NOTHING

inline given [A]: Conversion[NOTHING.type, Option[A]] = _ => None

def apply[A](p: Vector[A], o: Option[A] = NOTHING:  Option[A]): Unit = ???

def test = apply[String](Vector.empty)