There is a lot of discussion ongoing about ARC vs GC but in
practice forcing either of those is unacceptable. Language that
is strongly coupled with hard-coded memory model will inevitably
fail in some domain.
For me perfect solution would have been to use an allocator
concept as language basis instead and let you chose any
conformant allocator for built-in language features. With both GC
and ARC available in Phobos / druntime.
Bottom-Up design is simply superior to Top-Down when it comes to
tools.
