interface IDeveloper
{
  void Foo();
  void LearnNewLanguage(string language)
  {
    Console.WriteLine($"Learning {language} in a default way.");
  }
}

abstract class Developer
{
  public abstract void Foo();
  public void LearnNewLanguage(string language)
  {
    Console.WriteLine($"Learning {language} in a default way.");
  }
}

.class interface private auto ansi abstract test80.IDeveloper
{
  // Methods
  .method public hidebysig newslot abstract virtual 
    instance void Foo () cil managed 
  {
  } // end of method IDeveloper::Foo

  .method public hidebysig newslot virtual 
    instance void LearnNewLanguage (
      string language
    ) cil managed 
  {
    // Method begins at RVA 0x2084
    // Code size 24 (0x18)
    .maxstack 8

    IL_0000: nop
    IL_0001: ldstr "Learning "
    IL_0006: ldarg.1
    IL_0007: ldstr " in a default way."
    IL_000c: call string [System.Runtime]System.String::Concat(string, string, string)
    IL_0011: call void [System.Console]System.Console::WriteLine(string)
    IL_0016: nop
    IL_0017: ret
  } // end of method IDeveloper::LearnNewLanguage

}

.class private auto ansi abstract beforefieldinit test80.Developer
  extends [System.Runtime]System.Object
{
  // Methods
  .method public hidebysig newslot abstract virtual 
    instance void Foo () cil managed 
  {
  } // end of method Developer::Foo

  .method public hidebysig 
    instance void LearnNewLanguage (
      string language
    ) cil managed 
  {
    // Method begins at RVA 0x20e0
    // Code size 24 (0x18)
    .maxstack 8

    IL_0000: nop
    IL_0001: ldstr "Learning "
    IL_0006: ldarg.1
    IL_0007: ldstr " in a default way."
    IL_000c: call string [System.Runtime]System.String::Concat(string, string, string)
    IL_0011: call void [System.Console]System.Console::WriteLine(string)
    IL_0016: nop
    IL_0017: ret
  } // end of method Developer::LearnNewLanguage

  .method family hidebysig specialname rtspecialname 
    instance void .ctor () cil managed 
  {
    // Method begins at RVA 0x20f9
    // Code size 8 (0x8)
    .maxstack 8

    IL_0000: ldarg.0
    IL_0001: call instance void [System.Runtime]System.Object::.ctor()
    IL_0006: nop
    IL_0007: ret
  } // end of method Developer::.ctor
}

interface IFoo1
{
  abstract void Bar();
  public virtual void Zot() {}
}

interface IFoo2 : IFoo1
{
  public override void Zot() {} // CS0106 The modifier 'override' is not valid for this item
}

interface IFoo1
{
  abstract void Bar();
  public virtual void Zot() {}
}

interface IFoo2 : IFoo1
{
  public void Zot() {} // CS0108: 'IFoo2.Zot()' hides inherited member 'IFoo1.Zot()'. Use the new keyword if hiding was intended.
}