Suppress "Discarded Non-Unit Value" Warning
I Have Added the Scalac Command Line Argument -Ywarn-Value-Discard to My Build Because This Would Have Caught a Subtle Bug That I Just Found in My Code...
I have added the scalac command line argument -Ywarn-value-discard to my build because this would have caught a subtle bug that I just found in my code. However, I now get some warnings for "discarded non-Unit value" that are about intentional discards, not bugs. How do I suppress those warnings?
3 Answers
You suppress these warning by explictly returning unit (that is ()).
By example turn this:
def method1() = {
println("Hello")
"Bye"
}
def method2() {
method1() // Returns "Bye", which is implicitly discarded
}
into:
def method1() = {
println("Hello")
"Bye"
}
def method2() {
method1()
() // Explicitly return unit
}
According to this answer, you can also use the syntax val _, i.e.
def method2(): Unit = {
val _ = method1()
}
But there is some dispute over whether this or the answer by @Régis is the preferred style.
Now you can suppress value-discard warning via type ascription to Unit in Scala 2.13.
This is an example:
def suppressValueDiscard(): Unit =
"": Unit
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