Forbid needless pointer casts

[tsbockman]

On Thursday, 20 February 2020 at 11:38:22 UTC, FlameInHeart wrote:
> ...mm, or is there the possibility of a problem with templated 
> or otherwise generated code?

Yes, this change would needlessly complicate some template code. 
Having to write a bunch of extra logic just to prevent a template 
from emitting harmless no-op code in some circumstances is pretty 
painful in practice.