if __ctfe and __ctfe functions

[Adam D. Ruppe]

On Tuesday, 29 July 2025 at 12:00:02 UTC, Quirin Schroll wrote:
> We could also decide to special-case `if (__ctfe)`, either way: 
> The branch in which `__ctfe` is guaranteed to be true should be 
> ignored w.r.t. some attribute checks: In a `__ctfe` section,
> - a `@nogc` function can allocate, and

Note that this is implemented in OpenD, it works fine and enables 
some interesting pattern when combined with a default parameter 
bug fix.

See:
https://dpldocs.info/this-week-in-d/Blog.Posted_2024_11_25.html#to-set-the-stage-for-new-memory-patterns

> - Overloading on `__ctfe` is possible and useful: Overload 
> resolution for run-time code generation discards all `__ctfe` 
> functions

Same result can be achieved by the if(__ctfe) {} branch....

> - A `__ctfe` function is guaranteed not to be emitted into the 
> binary.

this is something opend tried to do via a pragma, but had to 
revert since our impl introduced regressions. some day we'll get 
back and finish it though.