Regarding "unconst", we need to have a discussion. There are ways to make it implicit, namely by tying the return continuation of `if` to the constness of the conditional, but then one loses the ability to specialize the return continuation for constant results.

Named `let` is the most primitive form of loop, suitable for use in runtime and compile time (constexpr-style) context. There are more convenient, less versatile and compiler-friendly versions like `for ... in` and `while`. It is possible to design your own loop structures, and even build an auto-unconsting `if`, so I was hoping that the community would innovate here within the language.

Partial evaluation is user-controlled. The rules are deterministic: the system guarantees that constant expressions are always folded. The error message would not exist if we could solve the halting problem. There is no way to tell in every instance if a loop or recursion ever terminates, so I went for the simplest rule, which is that if a label is reentered the 32th time, we abort compilation. It's a cautious limit because constant folding is interpretation (slow), and I don't think that programmers want big loops to unroll. This can and should be discussed. I certainly don't have all the answers.

> I understand that it's the underlying label/goto abstraction leaking through

Scopes' abstractions aren't leaking, they are offering their innards to you. You can generate and inspect IL from within the language. Everything has been made so that you can build your own abstractions on top of them, which is only possible when the internals aren't hidden. The philosophy is that a compiler is a servant, not a framework.