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7853 :: Simulate super in Java at compile time

• Dabod (orginal) [2021-04-25T07:49:33+02:00] view original

  I am not sure if my code is valid (without last line, it can compile and run)

  import typetraits
  
  type
    Parent {.inheritable.} = object
    Child = object of Parent
  
  proc super(_: typedesc[Parent]): typedesc = typedesc[void]
  proc super(_: typedesc[Child]): typedesc = typedesc[Parent]
  
  echo Parent.name
  echo Child.name
  #echo Child.super.name
  Run

  The last line is compile with error

  
  Error: expression 'super(Child)' has no type (or is ambiguous)
  Run

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• ElegantBeef (orginal) [2021-04-25T07:58:59+02:00] view original

  Well you could use template instead of proc there, but that's very tedious to maintain and this is just easier.

  import std/macros
  
  type
    Parent {.inheritable.} = object
    Child = object of Parent
  macro parent(typ: typedesc): untyped =
    let impl = typ.getImpl
    assert impl[^1].kind == nnkObjectTy and impl[^1][1].kind == nnkOfInherit, "Type is not a child obj"
    result = impl[^1][1][0]
  echo Parent
  echo Child
  echo Child.parent
  Run

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• Dabod (orginal) [2021-04-25T08:00:05+02:00] view original

  With template, it can build and run as expected

  
  import typetraits
  
  type
    Parent {.inheritable.} = object
    Child = object of Parent
  
  template super(_: typedesc[Parent]): typedesc = typedesc[void]
  template super(_: typedesc[Child]): typedesc = typedesc[Parent]
  
  echo Parent.name
  echo Child.name
  echo Child.super.name
  Run

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