Macro view_if 

macro_rules! view_if {
    ($cond:expr, $then:expr $(,)?) => { ... };
    ($cond:expr, $then:expr, $else:expr $(,)?) => { ... };
}

A ViewBuilder-style conditional that keeps each branch’s identity.

Unlike a plain Rust if, which picks a view and erases the branch, this builds a _ConditionalContent — so SwiftUI sees a branch change and can run insertion and removal transitions, and each arm keeps its own state.

view_if!(is_open, text("open"), text("closed"))