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2435 :: How to annotate statements in proc for macro behavior?

• Krux02 (orginal) [2016-08-04T00:55:54+02:00] view original

  I would like to create a macro that gets as argument a function call. The macro should then replace the function call with a call of a modified function. But since my macro should not generally modify everything in the function, but just annotated statements, I would like to know how I can do such annotations. Sadly user defined pragmas seem to be not suitable.

  import macros
  
  {. pragma: myAnnotation .}
  
  proc foobar(i : int) : int =
    var j {. myAnnotation .} : int = i + 2
    return i * 2 + j
  
  macro handlePragmas( arg: typed ): typed =
    echo arg[0].symbol.getImpl.repr
    discard
  
  handlePragmas: foobar(13)
  Run

  the output of the macro here is just

  
  proc foobar(i: int): int =
    var j: int = i + 2
    return result = i * 2 + j
  Run

  As you can see, the {. myAnnotation .} pragma is gone, and that is what I would need in my use case.

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• Araq (orginal) [2016-08-04T01:50:36+02:00] view original

  Yeah that's unfortunate. I planned on fixing this, maybe you can help out? The pragma is not eliminated if you declare your macro like

  macro handlePragmas( arg: untyped ): typed
  Run

  but I can imagine you like to work on sem'checked AST instead. If the whole excercise is code optimization, you can also consider to use a term rewriting macro instead. These run after sem'check too.

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