If it is a pure value, I'd assume yes, but if it is tied to a side effect (E.g. write its value to a file), then it would be not used but still could break your app if removed.

I'm not familiar with rust language specifically, but generally that's what could happen

Yeah that should be looked for in a CI line check, not a compilation requirement

You mean a system like the compiler

Yeah any compiler should support environments or config files. Our CI would never work with without --env “stage”

Let's not pretend people acknowledge warnings, though. It's a popular meme that projects will have hundreds of warnings and that devs will ignore them all.

There's a perfectly valid use case for opinionated languages that don't let you get away with that. It's also similar to how go has gofmt to enforce a consistent formatting.

Honestly, I've been using Go for years and this unused variable error rarely comes up. When it does, it's trivial to resolve. But the error has saved me from bugs more often than it has wasted my time. Most commonly when you declare a new variable in a narrower scope when you intended to assign to the variable of the same name (since Go has separate declare vs assign operators).

Some people simply ignore warnings, that's the main issue. Trust me, I saw this way too often.

If you cannot compile it than you have to fix it, otherwise just mark unused variables as 'not an error' via _ = someunusedvar.