> built by one single dad

Not some random dad, but a GC expert and former leader of the JavaScript VM team at Apple.

I can tell you that it's not that he's setting aside speed -- the fact that it's as fast as it is is an achievement. But there is a degree of unavoidable overhead -- IIRC his goal is to get it down to 20-30% for most workloads, but beyond that you're running into the realities of runtime bounds checks, materializing the flight ptrs, etc.

20% to 30% slower would be amazing for all the extra runtime work that is required in my limited understanding. This would be good enough for a whole lot of serious applications.

You initially said that rewriting in Rust "seems stupid" based on what Fil-C provides, and someone pointed out technical reasons why it still might be useful in some circumstances. It's great that a single dad is able to build Fil-C on his own, and you're certainly entitled to the opinion that you don't like the idea of lifetimes in the type system, but it's genuinely hard to tell if there's a specific technical point you're trying to make or you dislike Rust so much that you're interpreting someone disagreeing with you about whether Fil-C obviates it as somehow being a personal attack on the author.

> tying the lifetimes into the type system is the correct way to do memory management.

Type systems used to be THE sexy PL research topic for about twenty years or so, so all the programming languages innovation has been about doing everything with type systems.