Macro temp 

macro_rules! temp {
    (($Var:ident), $body:expr) => { ... };
    (($Var:ident,), $body:expr) => { ... };
    (($Var:ident, $($rest:ident),+ $(,)?), $body:expr) => { ... };
}

Introduces one or more temporary query variables for a nested constraint.

temp! is only meaningful inside macros that provide a local query context, such as find!, exists!, or macros expanded from them like pattern!. Each identifier becomes a fresh query variable that is scoped to the wrapped body.

find!(
    (person: Inline<_>),
    temp!((friend), and!(
        pattern!(&kb, [{ ?person @ social::friend: ?friend }]),
        pattern!(&kb, [{ ?friend @ social::name: "Bob" }])
    ))
)