Yes, lot of formal verifications are (almost) free and most others are not. But if you at least take the free ones, why not…

I wish something like Lamport's TLA+ (https://lamport.azurewebsites.net/tla/tla.html) was supported in modern language compilers - perhaps with annotations/macros and a mini formal DSL.

And types too :)

I know many words have been spilled over why it shouldn't have them, but I remain unconvinced.

I modelled a trivial traffic light system to make sure the cars and pedestrians didn't have "green" at the same time. And they didn't, because they had "green_light" at the same time. Oops!

It's still in pretty early development, but you may be interested in https://github.com/informalsystems/quint

> It combines the robust theoretical basis of the Temporal Logic of Actions (TLA) with state-of-the-art static analysis and development tooling.

And it is typed ;)

It's a tooling problem. Nearly every comment I read about formal verification being overkill are about proposal to incorporate existing formal verification tools into existing workflows. It is not easy to get an organization to adopt TLA+ in a way that's useful for almost any problem.

Add a language feature like the above to TS and you'd see adoption overnight. Pretty much everyone is happy to let their build system add additional correctness guarantees if its fast enough.