chore: make the compiler and library compile

Author: hamzaremmal

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

@@ -109,7 +109,7 @@ class GenBCode extends Phase { self =>
       result
     finally
       // frontendAccess and postProcessor are created lazilly, clean them up only if they were initialized
-      if _frontendAccess ne null then
+      if !(_frontendAccess eq null) then
         frontendAccess.compilerSettings.outputDirectory match {
           case jar: JarArchive =>
             if (ctx.run.nn.suspendedUnits.nonEmpty)
@@ -120,7 +120,7 @@ class GenBCode extends Phase { self =>
             jar.close()
           case _ => ()
         }
-      if _postProcessor ne null then
+      if !(_postProcessor eq null) then
         postProcessor.classfileWriter.close()
       generatedClassHandler.close()
   }

project/Build.scala

@@ -1110,7 +1110,8 @@ object Build {
     (Compile / scalacOptions) ++= Seq(
       // Needed so that the library sources are visible when `dotty.tools.dotc.core.Definitions#init` is called
       "-sourcepath", (Compile / sourceDirectories).value.map(_.getAbsolutePath).distinct.mkString(File.pathSeparator),
-      "-Yexplicit-nulls",
+      // "-Yexplicit-nulls", TODO: Enable it back
+      "-Ycompile-scala2-library"
     ),
     (Compile / doc / scalacOptions) ++= ScaladocConfigs.DefaultGenerationSettings.value.settings,
     (Compile / packageSrc / mappings) ++= {