Conditionally capture variables in closure to implement custom control

I'm trying to implement custom control structures in Rust. For example, suppose that for whatever reason, I want to implement a custom if statement as a function. The function would take a condition, a closure representing the true branch and a closure representing the false branch. Depending on the condition, I would call the true branch closure or the false branch closure.

It looks something like this:

pub fn fun_if<O>(
    cond: bool,
    mut tbranch: impl FnMut() -> O,
    mut fbranch: impl FnMut() -> O,
) -> O {
    if cond {
        tbranch()
    } else {
        fbranch()
    }
}

The problem with this implementation is that the true closure can not mutably borrow the same variables as the false closure:

let mut test = 0;
fun_if(true, || test = 1, || test = 2)
                ^^^^         ^^^^ ! error !

However, the rust if statement is smart enough to know that the true and false branch will never be called together. The following compiles just fine:

let mut test = 0;
if true {
    test = 1
} else {
    test = 2
}

My question is if the behavior of if is possible to replicate with functions and unsafe code in rust.

(This is a slightly contrived example and I'm happy to provide the real example where this came up if anybody is interested. What I asked here is the core idea though.)