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2843 :: Method does not work, implicit generic?

• mmierzwa (orginal) [2017-03-11T17:50:16+01:00] view original

  Hi

  I have had hard time with method which did not behave as I expected to.

  child.nim

  type Parent* = ref object of RootObj
  type Child* = ref object of Parent
  type Some = object
  
  method getDataToSave*(x: Parent): object {.base.} =
      echo("took getDataToSave Parent")
      var o: Some
      return o
  
  method getDataToSave*(x: Child): object =
      echo("took getDataToSave from Child")
      var o: Some
      return o
  Run

  main.nim

  from child import Parent, Child, getDataToSave
  
  proc test() =
      var x: Parent = Child()
      discard getDataToSave(x)
  
  test()
  Run

  It compiles and gives "took getDataToSave from Parent", whilst I expected method on Child would be invoked. After long long time I noticed that problem lies in return type which is object. If you change child.nim

  type Parent* = ref object of RootObj
  type Child* = ref object of Parent
  type Some = object
  
  method getDataToSave*(x: Parent): Some {.base.} =
      echo("took getDataToSave Parent")
      var o: Some
      return o
  
  method getDataToSave*(x: Child): Some =
      echo("took getDataToSave from Child")
      var o: Some
      return o
  Run

  It is working as expected, which means I get "took getDataToSave from Child". Perhaps compiler should give warning?

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