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1463 :: Setting visibility in macros

• andrea (orginal) [2015-07-20T23:24:20+02:00] view original

  I am trying to correctly handle visibility modifiers in my patty macros for pattern matching. I am getting an error I don't understand.

  For context, the variant macro expands a declaration like

  variant Shape:
    Circle(r: float)
    Rectangle(w: float, h: float)
    UnitCircle
  Run

  to something like

  type
    ShapeKind {.pure.} = enum
      Circle, Rectangle, UnitCircle
    Shape = object
      case kind: ShapeKind
      of ShapeKind.Circle:
        r: float
      of ShapeKind.Rectangle:
        w: float
        h: float
      of ShapeKind.UnitCircle:
        nil
  Run

  plus some definitions for equality and constructors (see here for more information).

  I would like to be able to decide whether the defined types are public or private. The problem is, if I try to change this line to

  let enumType =
    if pub: newEnum(postfix(enumName, "*"), enumsIn(body))
    else: newEnum(enumName, enumsIn(body))
  Run

  that is, by adding a * if some flag is set, I get an error test.nim(77, 14) Error: invalid visibility: '*' in the calling code.

  What is the right way to set visibility inside a macro?

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• rku (orginal) [2015-07-21T07:58:51+02:00] view original

  Thats how i do it:

  if export_proc:
          ctor[0] = new_nim_node(nnkPostfix).add(
              new_ident_node("*"),
              ctor[0]
          )
  Run

  Rule of thumb - manually write code that macro should generate and dump its ast. Then make a macro to construct identical AST. Pretty sure you will find inconsistencies between AST of manually written code and AST generated by your macro.

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• andrea (orginal) [2015-07-21T09:38:34+02:00] view original

  The postfix function in the macros package is just a shortcut for that, see here

  It seems to me that the two trees are identical - in fact that is how I found out how to set the visibility. Still, I get the above error.

  EDIT: I checked by calling echo treeRepr(result) in my macro vs calling dumpTree on the desired output written by hand. I ran a diff and it turns out the two trees are identical

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• andrea (orginal) [2015-07-21T09:54:51+02:00] view original

  Sorry, it turns out it works. It is not working in my tests, probably because the type is defined inside a test, so I would have a public type defined inside a local scope, which does not make much sense now that I think about it. I will restructure my tests to avoid the issue

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• Araq (orginal) [2015-07-21T17:18:52+02:00] view original

  I will restructure my tests to avoid the issue

  Or maybe we should allow * but ignore in a local scope for convenience.

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