NullPointerException when putting a Singleton type in an AnyVal

[Atry]

Welcome to Scala 2.13.0 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_202-ea).
Type in expressions for evaluation. Or try :help.

scala> class Foo[S <: AnyRef](val s: S) extends AnyVal
defined class Foo

scala> def Foo[S <: AnyRef](name: S) = new Foo[name.type](name)
Foo: [S <: AnyRef](name: S)Foo[name.type]

scala> Foo("xx")
java.lang.NullPointerException
  at Foo$.hashCode$extension(<console>:1)
  at Foo.hashCode(<console>:1)
  at java.lang.Object.toString(Object.java:236)
  at scala.runtime.ScalaRunTime$.inner$1(ScalaRunTime.scala:238)
  at scala.runtime.ScalaRunTime$.stringOf(ScalaRunTime.scala:243)
  at scala.runtime.ScalaRunTime$.replStringOf(ScalaRunTime.scala:251)
  at .$print$lzycompute(<synthetic>:8)
  ... 26 elided

[som-snytt]

class Foo[S <: AnyRef](val s: S) extends AnyVal

object Test {
  def Foo[S <: AnyRef](name: S) = new Foo[name.type](name)

  val foo = Foo("x")

  def main(args: Array[String]) = println {
    foo
  }
}

The foo field initialization is incorrectly elided in constructors, apparently. Null foo results in NPE.

  object Test extends Object {
    def <init>(): Test.type = {
      Test.super.<init>();
      ()
    };
    def Foo(name: Object): Object = name;
    private[this] val foo: String("x") = Test.this.Foo("x").$asInstanceOf[String("x")]();
    <stable> <accessor> def foo(): String("x") = Test.this.foo;
    def main(args: Array[String]): Unit = scala.Predef.println(new Foo(Test.this.foo()))
  }
[[syntax trees at end of              constructors]] // t11659.scala
  object Test extends Object {
    def Foo(name: Object): Object = name;
    <stable> <accessor> def foo(): String("x") = Test.this.foo;
    def main(args: Array[String]): Unit = scala.Predef.println(new Foo(Test.this.foo()));
    def <init>(): Test.type = {
      Test.super.<init>();
      ()
    }
  }

[jxnu-liguobin]

I'm not familiar with this. Looks like I lost this? private[this] val foo: String("x") in object Test, tree.tpe=String("x")

I tested it. It seems that it has nothing to do with repl. It's a compiler error. The compiler did not call putstatic for field foo before use getstatic

      DefDef( // val foo(): String("x") in object Test
        <method> <stable> <accessor> <triedcooking>
        "foo"
        []
        List(Nil)
        <tpt> // tree.tpe=String("x")
        Test.this."foo " // private[this] val foo: String("x") in object Test, tree.tpe=String("x")
      )

[jxnu-liguobin]

I did some interesting tests.

conclusion: lost private[this] val f: String("x") = _;,Test.this.f = Test.this.Foo("x").$asInstanceOf[String("x")](): String("x")

But I don't know where the relevant files are and whether they can be repaired? Can anyone tell me? Thank you

Singleton

 object Test extends Object {
    def Foo(name: Object): Object = name;
    <stable> <accessor> def f(): String("x") = Test.this.f;
    def main(args: Array[String]): Unit = scala.Predef.println(new sandbox.Foo(Test.this.f()));
    def <init>(): sandbox.Test.type = {
      Test.super.<init>();
      ()
    }
  }

non-Singleton

 object Test extends Object {
    def Foo(name: Object): Object = name;
    private[this] val f: String = _;
    <stable> <accessor> def f(): String = Test.this.f;
    def main(args: Array[String]): Unit = scala.Predef.println(scala.Int.box(sandbox.Foo.hashCode$extension(Test.this.f())));
    def <init>(): sandbox.Test.type = {
      Test.super.<init>();
      Test.this.f = Test.this.Foo("x").$asInstanceOf[String]();
      ()
    }
  }

Singleton but lazy

object Test extends Object {
    final <synthetic> lazy private[this] var f: String("x") = _;
    @volatile private[this] var bitmap$0: Boolean = _;
    def Foo(name: Object): Object = name;
    private def f$lzycompute(): String("x") = {
      Test.this.synchronized[Unit](if (Test.this.bitmap$0.unary_!())
        {
          Test.this.f = (Test.this.Foo("x").$asInstanceOf[String("x")](): String("x"));
          Test.this.bitmap$0 = true
        });
      Test.this.f
    };
    <stable> <accessor> lazy def f(): String("x") = (if (Test.this.bitmap$0.unary_!())
      Test.this.f$lzycompute()
    else
      Test.this.f: String("x"));
    def main(args: Array[String]): Unit = scala.Predef.println(new sandbox.Foo(Test.this.f()));
    def <init>(): sandbox.Test.type = {
      Test.super.<init>();
      ()
    }
  }