Fix #3279

When using the repl through "sbt console", we used to use the class
loader sbt give us. But we need a class loader that has the output
directory of the compiler on the classpath

Author: allanrenucci

compiler/src/dotty/tools/repl/Rendering.scala

@@ -21,24 +21,26 @@ import dotc.core.StdNames.str
  *       `Rendering` is no longer valid.
  */
 private[repl] class Rendering(compiler: ReplCompiler,
-                              private var currentClassLoader: Option[ClassLoader] = None) {
+                              parentClassLoader: Option[ClassLoader] = None) {
 
+  private var _classLoader: ClassLoader = _
+
+  /** Class loader used to load compiled code */
   private def classLoader()(implicit ctx: Context) =
-    currentClassLoader.getOrElse {
+    if (_classLoader != null) _classLoader
+    else {
       import java.net.{URL, URLClassLoader}
 
-      /** the compiler's classpath, as URL's */
-      val compilerClasspath: Seq[URL] = ctx.platform.classPath(ctx).asURLs
-
-      def parent = new URLClassLoader(compilerClasspath.toArray,
-                                      classOf[ReplDriver].getClassLoader)
-
-      val newClsLoader = new AbstractFileClassLoader(compiler.directory,
-                                  currentClassLoader.getOrElse(parent))
+      val parent = parentClassLoader.getOrElse {
+        // the compiler's classpath, as URL's
+        val compilerClasspath = ctx.platform.classPath(ctx).asURLs
+        new URLClassLoader(compilerClasspath.toArray, classOf[ReplDriver].getClassLoader)
+      }
 
-      Thread.currentThread.setContextClassLoader(newClsLoader)
-      currentClassLoader = Some(newClsLoader)
-      newClsLoader
+      _classLoader = new AbstractFileClassLoader(compiler.directory, parent)
+      // Set the current Java "context" class loader to this rendering class loader
+      Thread.currentThread.setContextClassLoader(_classLoader)
+      _classLoader
     }
 
   /** Load the value of the symbol using reflection