in crumb-compiler/src/main/kotlin/com/uber/crumb/internal/wire/ProtoReader.kt [427:434]
fun readUnknownField(tag: Int) {
val unknownFieldsWriter = ProtoWriter(bufferStack[recursionDepth - 1])
val fieldEncoding = peekFieldEncoding()
val protoAdapter = fieldEncoding!!.rawProtoAdapter()
val value = protoAdapter.decode(this)
@Suppress("UNCHECKED_CAST") // We encode and decode the same types.
(protoAdapter as ProtoAdapter<Any>).encodeWithTag(unknownFieldsWriter, tag, value)
}