wacky idea: extend smart casting to understand `ja...

# language-proposals

[phroa]

wacky idea: extend smart casting to understand java.util.Optional#isPresent --

>>> import java.util.Optional
>>> val opt = Optional.of("hi")
>>> opt
Optional[hi]
>>> if (opt.isPresent())
...   System.out.println(opt) // rather than opt.get()
hi