I think the (JVM?) implementation of Map.getOrElse is confusing.

The implementation looks like this in Map.kt:

@kotlin.internal.InlineOnly public inline fun <K, V> Map<K, V>.getOrElse(key: K, defaultValue: () -> V): V = get(key) ?: defaultValue() 

Which seems trivial at first glance, but is incorrect if V is nullable, which is allowed in Map. So if you use getOrElse on your map that can have null values, you’re very likely making a mistake.

Below it, in the same file, I see:

internal inline fun <K, V> Map<K, V>.getOrElseNullable(key: K, defaultValue: () -> V): V { val value = get(key) if (value == null && !containsKey(key)) { return defaultValue() } else { @Suppress("UNCHECKED_CAST") return value as V } } 

Which is more correct, IMO. But it’s internal. Why doesn’t Kotlin use the safer version by default? And why doesn’t it at least expose the safer version as an option?