Don't use empty files to indicate presence of tasty in class path.

Use hasTasty files instead.

Author: DarkDimius

compiler/src/dotty/tools/backend/jvm/GenBCode.scala

@@ -214,7 +214,8 @@ class GenBCodePipeline(val entryPoints: List[Symbol], val int: DottyBackendInter
             } else if (!outTastyFile.isVirtual) {
               // Create an empty file to signal that a tasty section exist in the corresponding .class
               // This is much cheaper and simpler to check than doing classfile parsing
-              outTastyFile.create()
+              val hasTasty = getFileForClassfile(outF, store.name, ".hasTasty")
+              hasTasty.create()
             }
           }
 

compiler/src/dotty/tools/dotc/interactive/InteractiveDriver.scala

@@ -86,10 +86,10 @@ class InteractiveDriver(settings: List[String]) extends Driver {
             else
               null
           prefix != null && {
-            val tastyFile = prefix + ".tasty"
+            val hasTastyFile = prefix + ".hasTasty"
             binFile match {
               case pf: PlainFile =>
-                val tastyPath = pf.givenPath.parent / tastyFile
+                val tastyPath = pf.givenPath.parent / hasTastyFile
                 tastyPath.exists
               case _ =>
                 sys.error(s"Unhandled file type: $binFile [getClass = ${binFile.getClass}]")