Comment by zem

you would end up with llvm-ir-like code that was only technically rust/d insofar as the compilers could handle it. it would not be human-readable or maintainable at all; indeed, it would be harder to convert that to idiomatic rust/d than hand-translating the c++ code. and really, all you would gain would be getting rid of the c++ compiler and ending up with worse code.

the point of carbon is that you can incrementally migrate your c++ program to it in place, and the migrated code will end up easier to maintain than the original c++.