For Boolean conditionals, you're right. But there are richer conditionals that make certain variables available in only one clause of them, e.g., matching on whether an Either in Haskell is Left or Right, or whether a Result in Rust is an Err or an Ok.

> Does that work in anything but boilerplate code?

It depends on the problem and the language.

The most impressive I've ever seen was implementing "call with current continuation" as a monad, given nothing but the type signature.

Generally, it works best in strongly-typed, functional languages.

> The most impressive I've ever seen was implementing "call with current continuation" as a monad, given nothing but the type signature.

That sounds cool. Where to find this? I get only irrelevant search results.

To be honest, boilerplate is where I think I'd appreciate code generation the most.

That makes sense, but it also seems like a “the cause of, and solution to, all of life’s problems” sort of situation.