If you require the use of a GC, you can never be as "fast as C" in the general case, since there will always be specific cases where manual memory management will do something more efficient than what an automatic GC would have done --- just like a car with an automatic transmission can never be quite as efficient as a car with a manual transmission used competently.
If you want to talk about efficient GCed languages, you have many choices, most of which have more tooling and mindshare advantages than you language has tooling advantages.
Really, GCed languages are commodities these days. A lot of people have put a lot of work into the fundamental building blocks, and now people are just combining them in various ways.
If you want to talk about efficient GCed languages, you have many choices, most of which have more tooling and mindshare advantages than you language has tooling advantages.
Really, GCed languages are commodities these days. A lot of people have put a lot of work into the fundamental building blocks, and now people are just combining them in various ways.