> One of the key ideas with Ezno is that it attempts "maximum" knowledge of a source<p>I've been working on a new TypeScript-like language myself from scratch, which among other things takes this approach. Mine can do some of the numeric stuff shown here, but I'm jealous of (inspired by? :)) some of the crazier stuff going on here, like usage-based argument types and tracing not just value <i>shapes</i> but value <i>reference identities</i><p>The "automatic generics" feature in particular is absolutely bonkers. It never even occurred to me that you could do that. I'm wondering if there are unforeseen edge-cases, but also wishing I had it at work. Clunky generics syntax is one of the worst parts of TypeScript, even while generic function types are one of its best parts.<p>Wow, and side-effects-tracking too! Amazing<p>I am curious whether some of these checks will be limited by JavaScript's dynamism. Part of why I'm doing mine as a new language is that JavaScript's semantics are just way too flexible to form some of the guarantees I feel like you need for some of this aggressive inference. But now I'm questioning that.<p>Either way, this is insanely impressive. Definitely not just yet-another-JavaScript-toolchian.