Unused value warnings for XML literals starting with Scala 2.13.9

[BennyMcBenBen]

If I am using XML literals, then I am seeing compile warnings starting with Scala version 2.13.9. I am using the sbt-tpolecat plugin so these are actually compile errors for me.

Example:

import scala.xml.Elem

case class ToDoItem(name: String) {
  def toXml: Elem = {
    <to-do-item>
      <name>{name}</name>
    </to-do-item>
  }
}

Compile errors:

[error] ToDoItem.scala:5:5: unused value of type scala.xml.NodeBuffer (add `: Unit` to discard silently)
[error]     <to-do-item>
[error]     ^
[error] /ToDoItem.scala:6:7: unused value of type scala.xml.NodeBuffer (add `: Unit` to discard silently)
[error]       <name>{name}</name>

Is this a bug or are the new unused warnings incompatible with XML literals? What do you recommend? Thank you.

[lrytz]

The issue here is in the compiler (code it generates for XML literals), not in the xml library. Existing ticket: scala/bug#12658

[som-snytt]

Reopening in order to close it.

Note that under duress, it would be possible to generate different code in the compiler, at the cost of some complexity, but the simple and correct fix is to correct the signature of &+ aka addOne or append for NodeBuffer.