For a value class, the parameter always generates,...

# getting-started

[andym]

For a value class, the parameter always generates,

Property "xxx" is never used

• Is it normal to use @Suppress("unused") for every value class?
• And why does the linter not recognize this special case for a value class?

[Chris Lee]

That is not normal. Please paste sample code for context.

[andym]

Oh really? That's encouraging...

My typical use case is an inner class like the following:

@JvmInline
    value class Id(private val value: String)

and for each one, I get

[Chris Lee]

yes. you have defined it as private, implying you intend to use it within the class (you don’t, hence the warning). Remove private or use the property inside the class.

[andym]

Thanks very much for the explanation.
Interesting that the examples in the docs are private

[Chris Lee]

huh. yea. they are either incorrect (s/b just val) or incomplete (should show use of the prop).

[Chris Lee]

Here’s a couple examples of how I typically use value classes for trivial types (where type-safety is desired). I don’t personally like having a public val, would rather keep things private.

@JvmInline
public value class Password(private val value: String) {
    override fun toString(): String = value
}

@JvmInline
public value class Id(private val value: String) {
    override fun toString(): String {
        return "Id(value='$value')"
    }
    public fun asString() : String = value
}

[Sam]

The equals and hashCode operations still use the private property, though, so arguably it's never truly unused. https://youtrack.jetbrains.com/issue/KTIJ-20509

[Klitos Kyriacou]

For passwords, I prefer to prevent inadvertently outputting the password (e.g. in a log message):

@JvmInline
value class Password(private val value: String) {
    override fun toString() = "***"
    fun asPlaintextString() = value
}

That way when you have to pass the actual password text (e.g. to an API) the class forces you to realise that you're passing a password in plain view.
Credit for the idea: https://void2unit.onrender.com/post/inline+password/