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7070 :: Type problem with 1.4.0

• Peter (orginal) [2020-11-10T22:38:16+01:00] view original

  Hello,

  I use some complex ref types as follows:

  type
    PTimeInfo = ref DateTime
    
    TimeInfoEvent = ref object of PTimeInfo
      channel : int
      command : string
  Run

  Then I use a variable of TimeInfoEvent in a function to initialize it:

  proc initTimeInfoEvent(tie : TimeInfoEvent, ch : int = 0, cmd : string = "") =
    var ti=now()
    tie.channel = ch
    tie.command = cmd
    tie.second = ti.second
    tie.hour = ti.hour
    tie.minute = ti.minute
  Run

  It compiles correctly using Nim 1.0.6, but it fails with Nim 1.4.0 (even using --useVersion:1.0 option):

  
  Error: type mismatch: got <TimeInfoEvent, SecondRange>
  but expected one of:
  proc second=(dt: var DateTime; value: SecondRange)
    first type mismatch at position: 1
    required type for dt: var DateTime
    but expression 'tie' is of type: TimeInfoEvent
  Run

  How can I fix it?

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• DeletedUser (orginal) [2020-11-11T06:09:59+01:00] view original

  The problem here is that the second accessor accepts a var DateTime which is not automatically convertible from a ref DateTime. However, if you put {.experimental: "implicitDeref".} at the top of your module or use the dereference operator like tie[].second = ti.second, then it will work.

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• Peter (orginal) [2020-11-11T15:56:35+01:00] view original

  Indeed, {.experimental: "implicitDeref".} helps here. Thanks a lot for this hint. Where can I read the information about this behavior change between 1.0 and 1.4 versions?

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