A modern programming language that makes developers happier.

kotlinlang

I was looking at Kotlin source.  I found code
    `contract { callsInPlace(block, InvocationKind.EXACTLY_ONCE) }`
Where does `contract` come from?
What does this code do?

I remember <@U092N7GGG> mention that this is a feature currently been played with, that’s supposed to define a set of contracts a function will adhere to.
However, it’s only visible in the src, but doesn’t do anything at the moment

<https://github.com/JetBrains/kotlin/blob/edd3f76e7ba3578e1328009ac2f4d56ff9ecec95/libraries/stdlib/src/kotlin/internal/contracts/ContractBuilder.kt#L40-L43>