[kasey_junk]

Tagged types also have their problems.

1st they don't propagate, call a function on the tagged type and it returns the underlying type.

2nd they aren't type safe against the tagged type, so you can pass tagged types into functions that take the underlying type by default.

3rd in practice my code with tagged types ends up having lots of boilerplate and/or magic code that is hard to understand.

4th there are some pretty heinous compiler bugs that you will encounter with tagged types.

[noelwelsh]

It seems you've done a lot more with them than I have. I'm looking forward to crashing the compiler -- the true badge of honour amongst Scala developers ;-)

[yummyfajitas]

They absolutely shouldn't propagate.

    val x = 1.0 @@ Kilograms
    val y = x*x

y is not a Double @@ Kilograms.

[kasey_junk]

In many cases I'd like it to be.