Now I have to write:
if ($isTrue) then 'true'
toString($isTrue) or even shorter: '' + $isTrue
when using a Boolean value as a parameter in for instance a Log message.
Yet it would even be better if the type of parameter didn't matter at all. One is composing a text (String) so the system should be able to convert every parameter type into a String. As far as Java is concerned every object has a toString method and String.valueOf(obj) could be used to avoid NullPointerExceptions. So it seems like a sensibel thing to support.
I completely agree. Also, it should be possible to omit the toString() call altogether in these cases. If you need to you could still write
($one + $two) if you want 3 printed instead of 12.