How to raise an error?

[ales-tsurko]

I see try/catch, but can't find how to actually raise an error. Is it possible?

[irh]

It's not possible at the moment, other than using assertions or deliberately doing something invalid.

IIRC I was about to work on throw after adding try/catch, but then I moved on to other things and it slipped my mind.

As things stand throw would only support strings being thrown, but I would like to support custom error types and I haven't got a complete picture of what that would look like yet.

[irh]

I think what could work is that throw would accept a string, or any map that implements @display (@display doesn't exist yet, but it would be useful in general for overriding string formatting behaviour).

try
  throw 
    data: foo
    @display: |self| "A terrible error occurred: {}".format self.data
catch error
  log_error_data error.data
  throw error

...then if the error is returned from the runtime then a meaningful error message would be available.

[ales-tsurko]

Using maps would also allow making different types of errors.

[irh]

Yes exactly, you can stick any data you like in the map, and it can have any structure as long as @display is implemented.

[irh]

I've implemented @display in #55, and I'll open an issue for throw.

[irh]

Issue for throw: #56.

[irh]

throw is now available, added in #57.