Update Promise; update build

Author: noti0na1

library/src/scala/concurrent/impl/Promise.scala

@@ -274,7 +274,7 @@ private[concurrent] object Promise {
 
     override final def isCompleted: Boolean = value0 ne null
 
-    override final def value: Option[Try[T]] = Option(value0).asInstanceOf[Option[Try[T]]]
+    override final def value: Option[Try[T]] = Option(value0)
 
     @tailrec // returns null if not completed
     private final def value0: Try[T] | Null = {

library/src/scala/reflect/ClassManifestDeprecatedApis.scala

@@ -32,7 +32,7 @@ trait ClassManifestDeprecatedApis[T] extends OptManifest[T] {
     def loop(left: Set[jClass[_]], seen: Set[jClass[_]]): Boolean = {
       left.nonEmpty && {
         val next = left.head
-        val supers = next.getInterfaces.nn.toSet ++ Option(next.getSuperclass)
+        val supers = next.getInterfaces.toSet ++ Option(next.getSuperclass)
         supers(sup) || {
           val xs = left ++ supers filterNot seen
           loop(xs - next, seen + next)
@@ -137,6 +137,7 @@ trait ClassManifestDeprecatedApis[T] extends OptManifest[T] {
 
   protected def argString =
     if (typeArguments.nonEmpty) typeArguments.mkString("[", ", ", "]")
+    // TODO: remove .nn here after 3.8. See #24070
     else if (runtimeClass.isArray) "["+ClassManifest.fromClass(runtimeClass.getComponentType.nn)+"]"
     else ""
 }

project/Build.scala

@@ -238,7 +238,7 @@ object Build {
       "-deprecation",
       "-unchecked",
       //"-Wconf:cat=deprecation&msg=Unsafe:s",    // example usage
-      // "-Werror",
+      "-Werror",
       //"-Wunused:all",
       //"-rewrite", // requires -Werror:false since no rewrites are applied with errors
       "-encoding", "UTF8",
@@ -959,6 +959,9 @@ object Build {
       }
     }.value,
 
+    // TODO: Enable fatal warnings after 3.8 because old stdlib has different nullability.
+    (Compile / scalacOptions) -= "-Werror",
+
     (Test / testOptions) += Tests.Argument(
       TestFrameworks.JUnit,
       "--exclude-categories=dotty.BootstrappedOnlyTests",
@@ -1767,7 +1770,7 @@ object Build {
       Compile / scalacOptions := Seq("-deprecation", "-feature", "-unchecked", "-encoding", "UTF8", "-language:implicitConversions"),
       Compile / scalacOptions += "-Yno-stdlib-patches",
       Compile / scalacOptions += "-Yexplicit-nulls",
-      (Compile / scalacOptions) ++= Seq(
+      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(_.getCanonicalPath).distinct.mkString(File.pathSeparator),
       ),
@@ -2293,6 +2296,8 @@ object Build {
       // Make sure that the produced artifacts have the minimum JVM version in the bytecode
       Compile / javacOptions  ++= Seq("--release", Versions.minimumJVMVersion),
       Compile / scalacOptions ++= Seq("--java-output-version", Versions.minimumJVMVersion),
+      // TODO: Enable fatal warnings after 3.8 because old stdlib has different nullability.
+      Compile / scalacOptions -= "-Werror",
       // Specify the default entry point of the compiler
       Compile / mainClass := Some("dotty.tools.dotc.Main"),
       // Add entry's to the MANIFEST