Docs: Section on local variables

[Jonathan M Davis]

On Thursday, April 26, 2012 19:46:38 Stewart Gordon wrote:
> I can begin to see why it makes errors for unused variables a bad idea. But
> why no warnings? Obviously the user wouldn't like to see warnings thrown
> at them when they try using templates with such constraints. But:

The existence of -w makes it so that warnings are just as bad as errors for 
something like this, since it makes warnings errors. The result is that there 
is a minimal difference between warnings and errors with dmd.

And honestly, while I agree that code shouldn't normally have unused 
variables, I so rarely see code with any that I think that it's a complete 
non-issue in general. I don't even know the last time that I saw an unused
variable left in code (except for on purpose in something like isInputRange).
I'd much prefer that warning about that sort of thing be left up to a
lint-like tool.

- Jonathan M Davis