[josephlord]

Good point. I missed that. Trouble with reading blog posts is getting relevant bits of code together on the screen, should have opened a second browser window (or third to include the HN discussion).

Value types are actually copy on write internally in Swift so no copy will be done unless a mutation of the error is attempted.

[JSoto]

Oh yeah that's a good point! (and a really interesting optimization that can be applied to immutable values)