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9848 :: Problem with object constructor in macro

• nick14 (orginal) [2023-01-26T20:25:54+01:00] view original

  Hello! I am learning to use macros in Nim and I am trying to define e.g. a macro that will be used like this:

  mymacro(foo: int)

  However, I am getting the error "object constructor needs an object type". It seems that the code in the macro that I have defined doesn't run at all and it fails some point before macros are run. Is there a way to bypass this error?

  Thank you!

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• xigoi (orginal) [2023-01-26T21:05:39+01:00] view original

  Unfortunately, it seems that the macro invocation is being parsed as an object construction. You'll probably have to change the syntax. How about mymacro(foo = int)?

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• georgelemon (orginal) [2023-01-26T21:40:20+01:00] view original

  Or, maybe you want to call your macro like this

  mymacro:
    foo: int
    bar: string
  Run

  macro mymacro(fields) =
    expectKind fields, nnkStmtList
    for f in fields:
      expectKind f, nnkCall
      expectKind f[0], nnkIdent
      expectKind f[1], nnkStmtList
      expectKind f[1][0], nnkIdent
      
      echo f[0].strVal      # field name
      echo f[1][0].strVal   # field type
  Run

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• DeletedUser (orginal) [2023-01-26T21:40:43+01:00] view original

  If (foo: int) is meant to be a function signature you can do mymacro do (foo: int): and not have to construct a parameter list yourself.

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