Use parent class loader in runner

Author: som-snytt

compiler/src/dotty/tools/MainGenericRunner.scala

@@ -193,8 +193,8 @@ object MainGenericRunner {
 
       case ExecuteMode.PossibleRun =>
         val newClasspath = (settings.classPath :+ ".").flatMap(_.split(classpathSeparator).filter(_.nonEmpty)).map(File(_).toURI.toURL)
-        import dotty.tools.runner.RichClassLoader._
-        val newClassLoader = ScalaClassLoader.fromURLsParallelCapable(newClasspath)
+        import dotty.tools.runner.RichClassLoader.{getClass as _, *}
+        val newClassLoader = ScalaClassLoader.fromURLsParallelCapable(newClasspath, getClass.getClassLoader)
         val targetToRun = settings.possibleEntryPaths.to(LazyList).find { entryPath =>
           newClassLoader.tryToLoadClass(entryPath).orElse {
             Option.when(Jar.isJarOrZip(dotty.tools.io.Path(entryPath)))(Jar(entryPath).mainClass).flatten

tests/run-with-compiler/i14541.check

@@ -1,2 +1,3 @@
 hello raw world
+hello rawr world
 hello run world

tests/run-with-compiler/i14541.scala

@@ -5,6 +5,7 @@ object Test:
   val classpath = dotty.tools.dotc.util.ClasspathFromClassloader(getClass.getClassLoader)
   def main(args: Array[String]): Unit =
     getClass.getClassLoader.run("echo", List("hello", "raw", "world"))
+    getClass.getClassLoader.run("dotty.tools.MainGenericRunner", List("echo", "hello", "rawr", "world"))
     // caution: uses "SCALA_OPTS"
     dotty.tools.MainGenericRunner.main(Array("--class-path", classpath, "echo", "hello", "run", "world"))