[core] Recompilation issue with incomplete type hierarchy and nested classes

[nitram84]

In this example I'm trying to decompile a library which references a dependent lib that is not available for decompilation with jadx. Let's take these two classes:

// defined in dependent lib, not reachable for jadx
package jadx;
public class BaseClass {

  public int doSomething() {
    return 0;
  }
}

// Target class for recompilation
package jadx;
public class OuterClass {

  public static class NestedClass extends BaseClass {

    @Override
    public int doSomething() {
      return super.doSomething();
    }
  }
}

If BaseClass is not available for decompilation jadx (latest git version) generates this non compilable code:

package jadx;
public class OuterClass {

  public static class NestedClass extends BaseClass {

    public int doSomething() {
      return OuterClass.super.doSomething();
    }
  }
}

We can simulate the missing base class with two smali files:

.class public Ljadx/OuterClass;
.super Ljava/lang/Object;
.source "OuterClass.java"

.annotation system Ldalvik/annotation/MemberClasses;
  value = {
    Ljadx/OuterClass$NestedClass;
  }
.end annotation

.method public constructor <init>()V
  .registers 1
  .prologue
  .line 2
    invoke-direct { p0 }, Ljava/lang/Object;-><init>()V
    return-void
.end method

.class public Ljadx/OuterClass$NestedClass;
.super Ljadx/BaseClass;
.source "OuterClass.java"

.annotation system Ldalvik/annotation/EnclosingClass;
  value = Ljadx/OuterClass;
.end annotation
.annotation system Ldalvik/annotation/InnerClass;
  accessFlags = 9
  name = "NestedClass"
.end annotation

.method public constructor <init>()V
  .registers 1
  .prologue
  .line 5
    invoke-direct { p0 }, Ljadx/BaseClass;-><init>()V
    return-void
.end method

.method public doSomething()I
  .registers 2
  .prologue
  .line 8
    invoke-super { p0 }, Ljadx/BaseClass;->doSomething()I
    move-result v0
    return v0
.end method

I'm aware that most cases with missing type hierarchy aren't fixable. But according to smali representation, I think this one is fixable.

[skylot]

@nitram84 thanks for test case! It helps me to resolve several root causes of this issue 🎉