For several reasons during development I sometimes comment out code. As I am chaotic and sometimes in a hurry, some of these make it to source control.

I also use comments to clarify blocks of code.

For instance:

MyClass MyFunction()
{
    (...)
    // return null; // TODO: dummy for now
    return obj;
}

Even though it "works" and alot of people do it this way, it annoys me that you cannot automatically distinguish commented-out code from "real" comments that clarify code:

• it adds noise when trying to read code
• you cannot search for commented-out code for for instance an on-commit hook in source control.

Some languages support multiple single-line comment styles - for instance in PHP you can either use // or # for a single-line comment - and developers can agree on using one of these for commented-out code:

# return null; // TODO: dummy for now
return obj;

Other languages - like C# which I am using today - have one style for single-line comments (right? I wish I was wrong). I have also seen examples of "commenting-out" code using compiler directives, which is great for large blocks of code, but a bit overkill for single lines as two new lines are required for the directive:

#if compile_commented_out
    return null; // TODO: dummy for now
#endif
return obj;

So as commenting-out code happens in every(?) language, shouldn't "disabled code" get its own syntax in language specifications? Are the pro's (separation of comments / disabled code, editors / source control acting on them) good enough and the cons ("shouldn't do commenting-out anyway", not a functional part of a language, potential IDE lag (thanks Thomas)) worth sacrificing?

Edit

I realise the example I used is silly; the dummy code could easily be removed as it is replaced by the actual code.