isElementOptional

Whether the element at the given index is optional (can be absent in serialized form). For generated descriptors, all elements that have a corresponding default parameter value are marked as optional. Custom serializers can treat optional values in a serialization-specific manner without a default parameters constraint.

Example of optionality:

@Serializable
class Holder(
    val a: Int, // isElementOptional(0) == false
    val b: Int?, // isElementOptional(1) == false
    val c: Int? = null, // isElementOptional(2) == true
    val d: List<Int>, // isElementOptional(3) == false
    val e: List<Int> = listOf(1), // isElementOptional(4) == true
)

Returns false for valid indices of collections, maps, and enums.

Throws