Deserializing invalid JSON does not always throw SerializationException

[diesieben07]

When deserializing JSON that does not fit the target classes, SerializationException should be thrown always. If the input JSON has the wrong type (e.g. 123 where a Boolean is expected), IllegalStateException is thrown instead (by StreamingJsonDecoder, which uses toBooleanStrict, for example).

This makes it difficult to distinguish invalid JSON from other errors, especially in a server environment, where you want to inform clients that their request is invalid (as opposed to some internal server error).

To Reproduce

@Serializable
data class SerializerBug(val booleanValue: Boolean)

fun main() {
    val json = Json {  }
    // throws java.lang.IllegalStateException: 123 does not represent a Boolean
    json.decodeFromString(SerializerBug.serializer(), """{"booleanValue": 123}""")
}

Expected behavior
kotlinx.serialization.SerializationException is thrown instead of generic IllegalStateException.

Environment

• Kotlin version: 1.4.21
• Library version: 1.0.1
• Kotlin platforms: Tested on JVM, but this bug exists in common code
• Gradle version: 6.7