debug a reserved keyword (even for enums?)

[Jonathan M Davis]

On Friday, April 10, 2026 4:37:54 PM Mountain Daylight Time Katastic via Digitalmars-d wrote:
> Hello all, it's been awhile. I have a question. Does it make
> 'sense' that debug is a reserved keyword even when its inside an
> enum?
>
> ```D
> enum loggingLevel {
>   none = 0,
>   debug, // Error: found `debug` when expecting `identifier`
>   info,
>   warning,
>   error
> }
> ```
>
> Is there anywhere where that would actually clash?
> ```D
> void myFunction(loggingLevel l);
> myFunction(loggingLevel.debug);
>
> with(loggingLevel){
> myFunction(debug);
> }
> ```
>
> Is 'debug' used anywhere outside of version() statements? Would
> it explode templates or something?

As a general rule, keywords in D are keywords no matter where they are. They
are not contextual. As such, you cannot use them anywhere other than where
the language uses that word. There are of course downsides to that approach,
but it's simpler to process than contextual keywords, and it tends to work
better with stuff like error messages (since the keyword then is essentially
an anchor point in the grammar instead of the compiler needing to figure
which context you're trying to use the keyword in when the context isn't
well-formed due to typos or whatnot).

Obviously, that's annoying when you have a situation where a keyword is the
best identfier, but you can't use it, because it's a keyword. However, the
solution that's generally used in D (and given in the official style guide)
is that when you need to use a keyword as an identifier, you apppend an
underscore to it:

https://dlang.org/dstyle.html#naming_keywords

So, you'd have LoggingLevel.debug_ rather than LoggingLevel.debug.

A prime example of where this comes up in the standard library is with
std.traits.FunctionAttribute:

https://dlang.org/phobos/std_traits.html#.FunctionAttribute

The enum literally needs to list a bunch of keywords as its values, and
that's not legal, so trailing underscores have been added to those keywords.

- Jonathan M Davis