Imported From: https://issues.scala-lang.org/browse/SI-7879?orig=1
Reporter: @OlegYch
Affected Versions: 2.10.2, 2.10.3-RC3

@paulp said:
The error message is correct. There's no copy method being generated.

"while without by-nameness the error is more clear"

That's because it's a different error. In that case there is a copy method.

@OlegYch said:
thanks, Paul, you're right
i guess we should rephrase the issue as "no copy method with by-name parameters" ?

@paulp said:
I think the repeated parameter part means what it says - repeated parameters in any parameter list including the first mean you don't get a copy method. That by-name parameters suppress the copy method is likely just undocumented. (That's why I didn't close this.)

@lrytz said:
what prompted the change was #5009 and #5118

i see that we don't generate copy when there's a by-name (https://github.com/scala/scala/blob/master/src/compiler/scala/tools/nsc/typechecker/Unapplies.scala#L186), but i don't remember why.. it should be either changed, or added to the spec

In 2.11.12, 2.12.11, and 2.13.2 REPL, I get the following (with variation in error format, but same exact message).

scala> case class UploadingFile(fid: String, name: String, length: Long, uploaded: Boolean)(onFileProcessingEnd: => String)
class UploadingFile

scala> val f = UploadingFile("", "", 0, true)("")
val f: UploadingFile = UploadingFile(,,0,true)

scala> println(f.copy(uploaded = true)())
                 ^
       error: value copy is not a member of UploadingFile
                      ^
       error: not found: value uploaded

it should be either changed, or added to the spec

I don't think we want to spec this, as Dotty does not have the restriction:

scala> f.copy(uploaded = true)("")
val res1: UploadingFile = UploadingFile(,,0,true)

and I've removed the "good first issue" label since the other choice, namely lifting the restriction in Scala 2, is probably neither easy nor especially important to tackle

thanks, @nogurenn, for taking a look 👍