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9 :: Shouldnt this code compile?

• ventor3000 (orginal) [2012-05-21T10:36:56+02:00] view original

  Is it possible to have an array of a 'abstract' base type and if so, how is it initialize with the least effort. The code below stops compiler with error 'type mismatch', which it actually is not, because I implicitly said that array 'myarray' and 'myarray2' is of type TAnimalArray. Also a function taking an openarray of PAnimal do not support inherited types in the array. Easiest way around this, or is it a bug? (see code below)

  #Robert

  
  
  type
      TAnimal=object
      PAnimal=ref TObject
      
      TDog=object of TAnimal
      PDog=ref TDog
      
      TCat=object of TAnimal
      PCat=ref TCat
      
      TAnimalArray=array[0..2,PAnimal]
  
  proc newDog():PDog = new(result)
  
  proc newCat():PCat = new(result)
  
  
  proc test(a:openarray[PAnimal])=
      echo("dummy")
  
  test(newDog(),newCat()) #does not work
  
  var myarray:TAnimalArray=[newDog(),newCat(),newDog()] #does not work
  
  var myarray2:TAnimalArray=[newDog(),newDog(),newDog()] #does not work either
  Run

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• Araq (orginal) [2012-05-21T19:38:48+02:00] view original

  It's not a really bug but an unimplemented feature. :roll: In general the compiler doesn't really like the subtype relation (see also bug #88). But please submit a feature request. For now the easiest workaround is to explicitly upcast the items:

  
  test(PAnimal(newDog()), PAnimal(newCat()))
  Run

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