IMO it depends if you're already in a chaining context. I wouldn't use it in a simple if-else branch, but it also removes the need to use if-else when you're already in a 10-function long chain.

Before:

if a.b().c().d().e().f() { Some(g().h().i()) } else { None }

Now:

a().b().c().d().e().f().then(|| g().h().i())

Even better if you have multiple boolean returns in the chain.

The naming can be confusing since "then" is usually used for async operations.

I used to like explicit if/then and using match, but chaining really does reduce code. It can sometimes take a while to golf it down, but damn is it satisfying when it’s all so compact. Followed by a `cargo fmt` and it feels way more elegant than branching

It is a lambda function with no parameters.

The argument of then() is a function which is evaluated only if the bool is true.

Rust lambdas look like this:

    |ar,gs| expr

So `|| expr` is just a lambda function that takes no arguments and evaluates to `expr`.

empty parameter list of a closure.

rust: |x| x+x

swift: {x in x+x}

rust: || 42

swift: { 42 }