Extension method not found when using by-name parameter in presence of implicit conversion

[OndrejSpanel]

Reproduction steps

Scala version: 2.13.10

import scala.language.implicitConversions

implicit class OrObj[T <: AnyRef](a: T) {
  def || (b: =>T): T = if (a != null) a else b
}

implicit def objToBool[T <: AnyRef](x: T): Boolean = x != null

class C(x: String)

val a = new C("A")
val b = new C("B")

a || b

Problem

Produces error "value || is not a member of C".

Note:

• the code compiles fine in Scala3
• the code compiles fine when implicit conversion objToBool is removed
• the code compiles fine when parameter to || is by value
• the code compiles fine when OrObj is not generic

[Jasper-M]

The strange part to me is that the implicit conversion is no longer ambiguous when you switch the parameter to by-value.

[som-snytt]

There is a glitch where Boolean ops are defined in the spec as by-name for purposes of laziness but do not actually have that signature. Also in Scala 2, f(=>A) is less specific than f(A), but not in 3. Perhaps the specificity of the results of the conversions determines the choice.