@samth Can I get an update on this?

@lexi-lambda Sorry about the delay with the review here -- this all looks quite good. Do the error messages show the fake struct you create ever?

@samth I've tested it in various situations, and I haven't managed to make TR print the fake struct in any error messages. The only possible problem is that there isn't actually way, as far as I can tell, to introspect what the types of the aliases actually are.

For example, evaluating (:print-type make-time) simply prints this:

(-> Time-Type Nanosecond Second Time)

It doesn't actually print what, say, Nanosecond actually is, and there doesn't appear to be any way to find out. It's actually an Index, but short of looking at the srfi/19 documentation, I don't think there would be any way to be aware of that.

Ok, seems reasonable. @takikawa @stamourv @shekari Any thoughts on the alias printing issue?

Actually, I've thought of another problem which makes me reconsider this hack. As much as I like its elegance, I don't think it's a good idea to use in actual code. This is why:

(define x : Index (time-nanosecond (current-time)))

The above code fails to typecheck.

Yeah, that's not ok, especially since just changing Index to Number will also not type check.

I think the right solution is to just not use the type aliases, given the error message issues.

/me should do something more sensible with error messages.

@samth Fixed. It would be nice to have better error messages, though, so that something like that is at least possible.

Ok, great, I'll merge soon.