[clang] [Clang] Add [[clang::no_specializations]] (PR #101469)

[Aaron Ballman via cfe-commits]

AaronBallman wrote:

> > > I did think about it more, and I think it would be more consistent to support the attribute on any sort of specializable entity, including functions - regardless of STL needs @AaronBallman @ldionne
> > 
> > 
> > Agreed; if we're adding a custom attribute, we might as well support it in a general form so users can also make use of it for their needs (which may be different than STL needs).
> 
> While I don't see much of a use-case for functions, I also don't see much of a downside (assuming implementing the attribute is as simple for functions as it is for variables and classes). Is there anything else that can be specialized?

Classes, functions, variables
Enumerations... maybe... ish?: https://godbolt.org/z/78qn1hf8d
(https://en.cppreference.com/w/cpp/language/template_specialization)

https://github.com/llvm/llvm-project/pull/101469