Regression call outer class super method from inner class

[FabioPinheiro]

Minimized code

trait A {
  val s = "same val in A"
  def f: String = s
}

class B extends A {
  class C {
    def call_f_in_A: String = B.super[A].f
  }
}
val b = new B                                                                                                                                                                                                                          
val c = new b.C
c.call_f_in_A // AbstractMethodError

Output

java.lang.AbstractMethodError:
Receiver class rs$line$3$B$C does not define or inherit an implementation of the 
resolved method 'abstract java.lang.String rs$line$3$A$$s()' of interface rs$line$3$A.

// defined trait A
// defined class B
java.lang.AbstractMethodError: Receiver class rs$line$3$B$C does not define or inherit an implementation of the resolved method 'abstract java.lang.String rs$line$3$A$$s()' of interface rs$line$3$A.
	at rs$line$3$A.f(rs$line$3:3)
	at rs$line$3$B$C.call_f_in_A(rs$line$3:8)
	at rs$line$3$.<init>(rs$line$3:13)
	at rs$line$3$.<clinit>(rs$line$3)
	at rs$line$3.b(rs$line$3)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:566)
	at dotty.tools.repl.Rendering.$anonfun$3(Rendering.scala:84)
	at scala.Option.map(Option.scala:242)
	at dotty.tools.repl.Rendering.valueOf(Rendering.scala:84)
	at dotty.tools.repl.Rendering.renderVal(Rendering.scala:121)
	at dotty.tools.repl.ReplDriver.$anonfun$13(ReplDriver.scala:306)
	at scala.collection.immutable.List.flatMap(List.scala:293)
	at scala.collection.immutable.List.flatMap(List.scala:79)
	at dotty.tools.repl.ReplDriver.extractAndFormatMembers$2(ReplDriver.scala:306)
	at dotty.tools.repl.ReplDriver.renderDefinitions$$anonfun$2(ReplDriver.scala:327)
	at scala.Option.map(Option.scala:242)
	at dotty.tools.repl.ReplDriver.renderDefinitions(ReplDriver.scala:330)
	at dotty.tools.repl.ReplDriver.compile$$anonfun$2(ReplDriver.scala:250)
	at scala.util.Either.fold(Either.scala:189)
	at dotty.tools.repl.ReplDriver.compile(ReplDriver.scala:265)
	at dotty.tools.repl.ReplDriver.interpret(ReplDriver.scala:195)
	at dotty.tools.repl.ReplDriver.loop$1(ReplDriver.scala:128)
	at dotty.tools.repl.ReplDriver.runUntilQuit$$anonfun$1(ReplDriver.scala:131)
	at dotty.tools.repl.ReplDriver.withRedirectedOutput(ReplDriver.scala:150)
	at dotty.tools.repl.ReplDriver.runUntilQuit(ReplDriver.scala:131)
	at dotty.tools.repl.Main$.main(Main.scala:6)
	at dotty.tools.repl.Main.main(Main.scala)

java.lang.NoClassDefFoundError: Could not initialize class rs$line$3$
	at rs$line$3.c(rs$line$3)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:566)
	at dotty.tools.repl.Rendering.$anonfun$3(Rendering.scala:84)
	at scala.Option.map(Option.scala:242)
	at dotty.tools.repl.Rendering.valueOf(Rendering.scala:84)
	at dotty.tools.repl.Rendering.renderVal(Rendering.scala:121)
	at dotty.tools.repl.ReplDriver.$anonfun$13(ReplDriver.scala:306)
	at scala.collection.immutable.List.flatMap(List.scala:293)
	at scala.collection.immutable.List.flatMap(List.scala:79)
	at dotty.tools.repl.ReplDriver.extractAndFormatMembers$2(ReplDriver.scala:306)
	at dotty.tools.repl.ReplDriver.renderDefinitions$$anonfun$2(ReplDriver.scala:327)
	at scala.Option.map(Option.scala:242)
	at dotty.tools.repl.ReplDriver.renderDefinitions(ReplDriver.scala:330)
	at dotty.tools.repl.ReplDriver.compile$$anonfun$2(ReplDriver.scala:250)
	at scala.util.Either.fold(Either.scala:189)
	at dotty.tools.repl.ReplDriver.compile(ReplDriver.scala:265)
	at dotty.tools.repl.ReplDriver.interpret(ReplDriver.scala:195)
	at dotty.tools.repl.ReplDriver.loop$1(ReplDriver.scala:128)
	at dotty.tools.repl.ReplDriver.runUntilQuit$$anonfun$1(ReplDriver.scala:131)
	at dotty.tools.repl.ReplDriver.withRedirectedOutput(ReplDriver.scala:150)
	at dotty.tools.repl.ReplDriver.runUntilQuit(ReplDriver.scala:131)
	at dotty.tools.repl.Main$.main(Main.scala:6)
	at dotty.tools.repl.Main.main(Main.scala)

java.lang.NoClassDefFoundError: Could not initialize class rs$line$3$
	at rs$line$3.res1(rs$line$3)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:566)
	at dotty.tools.repl.Rendering.$anonfun$3(Rendering.scala:84)
	at scala.Option.map(Option.scala:242)
	at dotty.tools.repl.Rendering.valueOf(Rendering.scala:84)
	at dotty.tools.repl.Rendering.renderVal(Rendering.scala:121)
	at dotty.tools.repl.ReplDriver.$anonfun$13(ReplDriver.scala:306)
	at scala.collection.immutable.List.flatMap(List.scala:293)
	at scala.collection.immutable.List.flatMap(List.scala:79)
	at dotty.tools.repl.ReplDriver.extractAndFormatMembers$2(ReplDriver.scala:306)
	at dotty.tools.repl.ReplDriver.renderDefinitions$$anonfun$2(ReplDriver.scala:327)
	at scala.Option.map(Option.scala:242)
	at dotty.tools.repl.ReplDriver.renderDefinitions(ReplDriver.scala:330)
	at dotty.tools.repl.ReplDriver.compile$$anonfun$2(ReplDriver.scala:250)
	at scala.util.Either.fold(Either.scala:189)
	at dotty.tools.repl.ReplDriver.compile(ReplDriver.scala:265)
	at dotty.tools.repl.ReplDriver.interpret(ReplDriver.scala:195)
	at dotty.tools.repl.ReplDriver.loop$1(ReplDriver.scala:128)
	at dotty.tools.repl.ReplDriver.runUntilQuit$$anonfun$1(ReplDriver.scala:131)
	at dotty.tools.repl.ReplDriver.withRedirectedOutput(ReplDriver.scala:150)
	at dotty.tools.repl.ReplDriver.runUntilQuit(ReplDriver.scala:131)
	at dotty.tools.repl.Main$.main(Main.scala:6)
	at dotty.tools.repl.Main.main(Main.scala)

Expectation

It should compile.
I had the impression this was working one week ago. Maybe it was long ago or I'm just mistaken.

[FabioPinheiro]

Ok. Does not matter if B is a Class ra an Object.
C just needs only to be an enclosing class. So we can use the syntax super[<Something>].
If we remove the [A] after super the example works fine.
The syntax super[<Something>] needs to disambiguate names from multiple inheritance (or close enough when extends multiple traits).

[odersky]

The unimplemented method is def s(): String in class C (!). I printed out the code at the end of all miniphases but there is no such member defined in C. Could it be that the backend creates it somehow?

@FabioPinheiro To troubleshoot it's generallty better to have self-contained test cases instead of the REPL. Less moving parts that way. To be sure, this problem is present also in the self-contained test:

trait A {
  val s = "same val in A"
  def f: String = s
}

class B extends A {
  class C {
    def call_f_in_A: String = B.super[A].f
  }
}
object Test extends App {
  val b = new B
  val c = new b.C
  c.call_f_in_A // AbstractMethodError
}

[FabioPinheiro]

OK. I will do that If I open any other ticket.

[FabioPinheiro]

Could it be that the backend creates it somehow?

@odersky I'm not sure if that was or not a question for me.
I'm trying things with the scalajs enable. There I get the error A expected but B$C found for tree of type org.scalajs.ir.Trees$This

Forgot to mention on the ticket.
If instead of a val s = "same val in A" we define a method def s = "same val in A". This example works.
This behavior makes more sense now to me.
After you mention that def s(): String is an unimplemented method on C. I tried to define an s in C (with val, def or var). It works*, that value is used instead.
For example, if s is a private val in A and we define something named A$$s in C. The value of A$$s will be used.

trait A {
  private val s = "same val in A"
  def f: String = s
}
class B extends A {
  class C {
    val A$$s = "This will be called and it shouldn't"
    def call_f_in_A: String = B.super[A].f
  }
}
object Test extends App {
  val b = new B
  val c = new b.C
  println(c.call_f_in_A) // It will print "This will be called and it shouldn't"
}

---

From my limited knowledge of reading the output from each phase.
Here are my assumptions and I hope this makes sense.

If we define s as a method in trait A and some val s in C

trait A {
  def s = "same val in A"
  def f: String = s
}
class B extends A {
  class C {
    val s = "This will be called and it shouldn't"
    def call_f_in_A: String = B.super[A].f
  }
}

Before the byte code generation, we have

  A() extends Object {
    def s(): String = "same val in A"
    def f(): String = this.s()
  }
...
  class B$C extends Object {
    ...
    private val s: String
    def s(): String = this.s
    def call_f_in_A(): String = B.super[A].f()
  }

The body of the method f(B.super[A].f()) is this.s(). That in the context of inner class B$C s will be a local method and it behaves as an overwrite method (the method s from A is never called).

If we define s as a val in trait A and nothing in C called s.
Before the byte code generation we end up with:

  A extends Object {
    def $init$(): Unit = 
      {
        ()
      }
    def s(): String
    protected def initial$s(): String = 
      {
        "same val in A"
      }
    def f(): String = this.s()
  }

Here the method s is unimplemented.

[odersky]

Yes, but that still begs the question why an (abstract) s is defined in C if there is no explicit val s. The question whether it happens in the backend was a general one, for people who know the backend or have touched it recently.