SaferExceptions1.scala

package progscala3.rounding.saferexceptions
import java.io.{IOException, File}
import scala.annotation.experimental
// Enable safer exceptions
import language.experimental.saferExceptions

/**
 * Currently as written, this file doesn't compile using Scala 3.1.
 * Also, the object needs the `@experimental` annotation in order to use this feature.
 */
@experimental  // Must annotate all the types or methods that use the feature...
object SaferExceptions:
  def main(fileNames: Array[String]): Unit =
    fileNames.foreach { fileName =>
      val file = openExistingFile(fileName)
      val path = file.getCanonicalPath()
      val size = file.length()
      println(s"file $fileName ($path) has $size bytes.")
    }

  def openExistingFile(fileName: String): File throws IOException =  // <1>
    val file = new File(fileName)
    if file.exists() == false then throw new IOException(s"$fileName doesn't exist!")
    file