How to fix compiler warning on scala.xml.Elem -

the following code generates compilation warning : a repeated case parameter or extracted sequence should matched sequence wildcard (_*)

import scala.xml.elem def matchelem(e: elem) = e match { case <source/> => "match!" } 

how fix ?

you can use scalac -xlint:-stars-align,_ suppress warning, this issue.

your function looks -xprint:typer:

        def matchelem(e: scala.xml.elem): string = e match {           case scala.xml.elem.unapplyseq(<unapply-selector>) <unapply> (_, "source", _, _) => "match!"         } 

to answer question:

$ scala -xlint welcome scala version 2.11.6 (java hotspot(tm) 64-bit server vm, java 1.8.0_45). type in expressions have them evaluated. type :help more information.  scala> import xml._ import xml._  scala> def matchelem(e: elem) = e match { case elem(_, "source", _, _, _*) => "match!" } matchelem: (e: scala.xml.elem)string 

or embed sequence wildcard in pattern:

scala> <a/> match { case <a/> => } <console>:8: warning: repeated case parameter or extracted sequence should matched sequence wildcard (_*).        <a/> match { case <a/> => }                           ^  scala> <a/> match { case <a>{ ns @ _* }</a> if ns.isempty => }