Reserved Identifiers (just making sure)

[Meta via Digitalmars-d-learn]

On Tuesday, 12 January 2016 at 16:20:10 UTC, naptime wrote:
> Hello,
>
>
> I already know the answer to my question, but I would like 
> someone to reassure me that I'm not mistaken before I rename 
> literally hundreds of identifiers in my code (and refactor at 
> least two large templates).
>
> TL;DR:  Am I understanding correctly that "_Foo" is NOT 
> reserved as an identifier in the sense that "__foo" IS 
> reserved, since they both are reserved in C?
>
>
> I have been using D for about two years.  Before that, I wrote 
> everything in strict ANSI C.  In C, not only are identifies 
> beginning with two underscores reserved (e.g. __foo), but 
> identifiers beginning with a single underscore followed by a 
> capital letter are also reserved (e.g. _Foo)†.  I would like to 
> verify that this is not the case in D.  To be absolutely clear, 
> I already know that such identifiers compile; I want to know if 
> they are reserved for future use by the D language.
>
>
> The following quote is from:
> https://dlang.org/spec/lex.html#Identifier
>
> Quote:
> "Identifiers start with a letter, _, or universal alpha, and 
> are followed by any number of letters, _, digits, or universal 
> alphas. Universal alphas are as defined in ISO/IEC 9899:1999(E) 
> Appendix D. (This is the C99 Standard.) Identifiers can be 
> arbitrarily long, and are case sensitive. Identifiers starting 
> with __ (two underscores) are reserved."
>
>
> The above quote makes it perfectly clear that identifiers 
> beginning with an underscore followed by an uppercase letter 
> are not reserved, but I could not find an example of such in 
> object.d, DRuntime, nor in Phobos2 source (my usual method of 
> verification).  Could someone who knows for sure please verify 
> that "_Foo" is not reserved in D?
>
>
> Thank you for your patience, and in advance for any assistance!
>
>
> †(, as well as some other obscure restrictions e.g. 
> all-uppercase identifiers beginning with 'E' are reserved in C.)

Yes, symbols in the form of `_Foo` are not reserved in D. Only 
symbols beginning with two underscores, such as __traits or 
__gshared. Technically the different `op*` names such as opCat, 
opBinary, etc. are reserved as well, int he sense that the 
compiler will recognize them and do special things, such as 
writing a + b as a.opBinary!"+"(b).