I think I get it

# atrium

[dio]

I think I get it

[robstoll]

I had a look at Arrow and see that Left and Right are both subclasses of Either. In this case you could use:

assert(either).isA<Left>{
  property(a).toBe(1)
}

That's surely still too verbose but maybe already a start

[robstoll]

Even better news, I published 0.6.0 and generalized DownCaster to TypeTransformer. Have a look at https://github.com/robstoll/atrium/blob/master/atrium-assertions/src/test/kotlin/ch/tutteli/atrium/assertions/any/typetransformation/TypeTransformerSpec.kt#L44

You could do something similar (or copy it).
Also have a look 22 where you can see its usage

[robstoll]

ah... wrong line numbers 41 and 19