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This marker distinguishes the experimental contract declaration API and is used to opt-in for that feature when declaring contracts of user functions.
Any usage of a declaration annotated with @ExperimentalContracts
must be accepted either by
annotating that usage with the OptIn annotation, e.g. @OptIn(ExperimentalContracts::class)
,
or by using the compiler argument -opt-in=kotlin.contracts.ExperimentalContracts
.