Is this a new bug ?

[Adam D. Ruppe]

On Saturday, 20 July 2019 at 09:01:21 UTC, Newbie2019 wrote:
> I want to cast std.stdio : writefln into pure function pointer, 
> so I can call it from debug pure function.

Like the other person said, try/catch turns throws to nothrow. 
The `debug` keyword disables pure checks. Those make this easy 
without any mixin or wrappers/casts at all.

But even if you did want to do the mixin route, look at how 
Phobos does this.

http://dpldocs.info/experimental-docs/std.traits.SetFunctionAttributes.1.html

the example of that function shows adding pure to a function 
pointer. (and btw I think the phobos function itself works with 
-betterC as well, you might be able to simply call it).

But then look at its implementation too:

http://dpldocs.info/experimental-docs/source/std.traits.d.html#L2354

.stringof only appears once there, for the `static assert` error 
message. Everything else is direct stuff. It does string concat a 
list of keywords, but they are literally written.

Then, it immediately mixes it in and thus the template returns 
the generated type which is used to make an alias and a cast on 
the outside, avoiding any mixin there too.