[metadat]

Absolutely, the disappointing part is that as code authors, we need to constantly remember about various (otherwise appealing and even encouraged by the language syntax and control constructs) footguns and "never approach such areas" of (totally valid) syntax.

Reminds me of programming in Javascript (it's extreme example, but the similarity is there).

[throwaway894345]

Yeah, it’s a bit disappointing. It doesn’t bother me too much, but it could be improved by a linter which could help you find shared mutable state. Without a concept of “const” (for complex types, anyway), I’m not sure how feasible such a linter would be.