Remove mutable methods which might potentially break due to introduce…

…d caching

compiler/src/dotty/tools/io/AbstractFile.scala

@@ -136,12 +136,6 @@ abstract class AbstractFile extends Iterable[AbstractFile] {
   /** Does this abstract file represent something which can contain classfiles? */
   def isClassContainer: Boolean = isDirectory || (jpath != null && ext.isJarOrZip)
 
-  /** Create a file on disk, if one does not exist already. */
-  def create(): Unit
-
-  /** Delete the underlying file or directory (recursively). */
-  def delete(): Unit
-
   /** Is this abstract file a directory? */
   def isDirectory: Boolean
 

compiler/src/dotty/tools/io/PlainFile.scala

@@ -15,7 +15,6 @@ import java.nio.file.{InvalidPathException, Paths}
 class PlainDirectory(givenPath: Directory) extends PlainFile(givenPath) {
   override val isDirectory: Boolean = true
   override def iterator(): Iterator[PlainFile] = givenPath.list.filter(_.exists).map(new PlainFile(_))
-  override def delete(): Unit = givenPath.deleteRecursively()
 }
 
 /** This class implements an abstract file backed by a File.
@@ -113,14 +112,6 @@ class PlainFile(val givenPath: Path) extends AbstractFile {
       null
   }
 
-  /** Does this abstract file denote an existing file? */
-  def create(): Unit = if (!exists) givenPath.createFile()
-
-  /** Delete the underlying file or directory (recursively). */
-  def delete(): Unit =
-    if (givenPath.isFile) givenPath.delete()
-    else if (givenPath.isDirectory) givenPath.toDirectory.deleteRecursively()
-
   /** Returns a plain file with the given name. It does not
    *  check that it exists.
    */