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support termination of errors by __close() #1

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support termination of errors by __close() #1

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@belm0
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@belm0 belm0 commented Oct 23, 2022 •
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If a __close() metamethod was called with an error in flight, the error can be terminated by returning true.

See use cases.

This is a work in progress, and the implementation may not be robust.

example (not yet working):

do
  local x <close> = setmetatable({}, {
    __close = function(self, err)
      print('__close()')
      return true
    end
  })

  error('oops')
  print('not reached')
end

print('goodbye')
__close()
goodbye

TODO:

  • fix stack unwind not stopping at the to-be-closed level
  • documentation

@belm0 belm0 marked this pull request as draft October 23, 2022 15:11
@well-in-that-case
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well-in-that-case commented Oct 23, 2022

Maybe I've misunderstood the rationale, but I feel like this is a patch skirting around try .. catch syntax. A TBC variable being able to enforce such authority over an entire block of code is uncanny.

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@belm0 @well-in-that-case