Adding pure to a function type

[jmh530]

On Thursday, 26 October 2017 at 19:08:56 UTC, Andrei Alexandrescu 
wrote:
>
> One additional thing I noted is that I wanted to add 
> attributes, not set them. I'd like some simpler primitives like 
> AddPure, RemovePure etc. BTW the PR is 
> https://github.com/dlang/phobos/pull/5470. -- Andrei

My above code could be easily adapted for adding attributes in 
the general case. The doc unittest for SetFunctionAttributes has 
an assumePure that shows how to add an attribute (though I'm not 
sure on removing).

While I think that it makes sense to add an 
AddFunctionAttributes/RemoveFunctionAttributes that match the 
functionality of SetFunctionAttributes, it's probably more 
convenient to also add an overload with a string template 
parameter, so AddPure!T would just be AddFunctionAttributes!(T, 
"pure") instead of AddFunctionAttributes!(T, 
FunctionAttribute.pure_).