What do grave accents do/mean in Kotlin?

Question

In as many expressions/definitions as possible please.

I'm writing a test function, where after the call fails, the function returns:

`this `fails with` "the state is propagated"`

(with the grave accents surrounding fails with ^ i don't know how to escape, sorry)

Answer 1

You want to use them when something is a Kotlin keyword (like Java's System.in) but you need to call it. Then you can do

System.`in` 

instead to make it work.

You can also use this in variables, functions, classes and any other identifiers. There is a small paragraph on this topic on Kotlin's documentation.

Answer 2

Actually, it is more than that.

You can use any class, function, variable, or identifier whose name contains spaces or symbols with grave accents.

class `Class name with spaces` {
    fun `method name with spaces, +, -`(`a parameter`: Int) {
        val `variable?!` = `a parameter` + 1
        println(`variable?!`.toString())
    }
}

fun main(args: Array<String>) {
    val instance = `Class name with spaces`()
    instance.`method name with spaces, +, -`(100)
}

This is a compilable and working code:

This is often used in testing, in order to make the test method names self-explanatory.

class OperationsUnitTest {
    @Test
    fun `addition should be commutative`() {
        ...
    }
}