Version: Nightly

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@__copy_capture

Deprecated

The @__copy_capture decorator is deprecated and will be removed in a future release. Use the current closure syntax with capture lists.

You can add the @__copy_capture decorator on a legacy closure to capture register-passable values by copy. This decorator causes a nested function to copy the value of the indicated variable into the closure object at the point of formation instead of capturing that variable by reference. This allows you to pass the closure as a parameter, but lifetimes aren't guaranteed to be respected.

  def foo(x: Int):
      var z = x

      @__copy_capture(z)
      @__parameter
      def formatter() -> Int:
          return z
      z = 2
      print(formatter())

  def main():
      foo(5)