write(f)ln style exception factory

[Dmitry Olshansky via Digitalmars-d]

Recalling the previous discussion of throwing exception being costly, I 
thought the idiom of "pay as you go" is worth incorporating into the 
standard library.

In brief:

throw exception("CPU temperature is below", 2.5, "K");
vs
throw new Exception(text("CPU temperature is below", 2.5, "K"));
or:
enforce(false, text("CPU temperature is below", 2.5, "K"));

The benefit that the latter will only construct string if printing is 
indeed requested.

Proof of concept:
https://gist.github.com/DmitryOlshansky/59ec5953874bc1985ac5

The problem with it is that for some reason writeln of exception won't 
compile while thrown exception is printed just fine by the trace handler.

Thoughts?

-- 
Dmitry Olshansky