Unnecessary allocation in name-based matching on value class #12405
Description
final class OptionVal[+A](val x: A) extends AnyVal {
def isEmpty: Boolean =
x == null
def get: A =
if (x == null) throw new NoSuchElementException("OptionVal.None.get")
else x
}
object OptionVal {
object Some {
def apply[A](x: A): OptionVal[A] = new OptionVal(x)
def unapply[A](x: OptionVal[A]): OptionVal[A] = x
}
def none[A]: OptionVal[A] = None.asInstanceOf[OptionVal[A]]
val None = new OptionVal[Null](null)
}
class Test {
def foo: OptionVal[String] = ???
def bar = foo match {
case OptionVal.Some(s) => s
case _ => ""
}
}The 2.13 compiler emits a redunand null check on a freshly created OptionVal instance.
public String bar() {
String s;
String string;
String string2 = this.foo();
String string3 = new OptionVal<String>(string2) != null && !OptionVal$.MODULE$.isEmpty$extension(string = OptionVal.Some$.MODULE$.unapply(string2)) ? (s = OptionVal$.MODULE$.get$extension(string)) : "";
return string3;
}
This was not the case in 2.12:
public String bar() {
String s;
String string = this.foo();
String string2 = OptionVal.Some$.MODULE$.unapply(string);
String string3 = !OptionVal$.MODULE$.isEmpty$extension(string2) ? (s = OptionVal$.MODULE$.get$extension(string2)) : "";
return string3;
}