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9313 :: Weird Type Mismatch error for JS backend (1.6.X)

• Niminem (orginal) [2022-07-22T09:33:33+02:00] view original

  Hi guys,

  I'm playing around with the JS backend and tried this snippet:

  import dom, jsconsole
  window.addEventListener("mousemove",
      proc(event: MouseEvent) =
          console.log(cstring"test")
      )
  Run

  I found this doesn't work with 1.6.0 and 1.6.6 but it does work with 1.4.8. I even tested with an earlier version, 1.2.2, and seems like it doesn't work with that version either.

  When I'm using a version that doesn't work I get a Type Mismatch: required type for cb: proc (ev: Event){.closure.}. Pretty weird considering MouseEvent IS inherited by the Event object type. Anyone know why I get this error? What could be the difference between 1.4.8 and the other versions that would throw this kind of error?

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• ElegantBeef (orginal) [2022-07-22T10:05:14+02:00] view original

  The older versions 'incorrectly' allowed a procedure that took a child type to upcast into a procedure that takes a parent type. The solution is to either internally convert the parameter into the child

  let event = MouseEvent event
  Run

  or cast the procedure to the base

  cast[proc(event: Event)](myProcHere)
  Run

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• Niminem (orginal) [2022-07-23T02:39:16+02:00] view original

  Interesting thanks for the explanation! I did not know this

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