Do not use Files.{exists, isRegularFile, isDirectory}

Apparently these methods are known to be slow on Java 8 (it got better
with Java 9):
https://rules.sonarsource.com/java/tag/performance/RSPEC-3725, this is
significant enough to show up in our benchmarks.

Author: smarter

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

@@ -121,7 +121,7 @@ abstract class AbstractFile extends Iterable[AbstractFile] {
 
   /** Does this abstract file denote an existing file? */
   def exists: Boolean = {
-    (jpath eq null) || Files.exists(jpath)
+    (jpath eq null) || jpath.toFile.exists
   }
 
   /** Does this abstract file represent something which can contain classfiles? */

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

@@ -54,8 +54,9 @@ object Path {
 
   def apply(path: String): Path = apply(Paths.get(path))
   def apply(jpath: JPath): Path = try {
-    if (Files.isRegularFile(jpath)) new File(jpath)
-    else if (Files.isDirectory(jpath)) new Directory(jpath)
+    val jfile = jpath.toFile
+    if (jfile.isFile) new File(jpath)
+    else if (jfile.isDirectory) new Directory(jpath)
     else new Path(jpath)
   } catch { case ex: SecurityException => new Path(jpath) }
 
@@ -160,10 +161,10 @@ class Path private[io] (val jpath: JPath) {
   // Boolean tests
   def canRead: Boolean = Files.isReadable(jpath)
   def canWrite: Boolean = Files.isWritable(jpath)
-  def exists: Boolean = try Files.exists(jpath)  catch { case ex: SecurityException => false }
-  def isFile: Boolean = try Files.isRegularFile(jpath)  catch { case ex: SecurityException => false }
+  def exists: Boolean = try jpath.toFile.exists  catch { case ex: SecurityException => false }
+  def isFile: Boolean = try jpath.toFile.isFile  catch { case ex: SecurityException => false }
   def isDirectory: Boolean =
-    try Files.isDirectory(jpath)
+    try jpath.toFile.isDirectory
     catch { case ex: SecurityException => jpath.toString == "." }
   def isAbsolute: Boolean = jpath.isAbsolute()
   def isEmpty: Boolean = path.length == 0