Macro params

macro_rules! params {
    () => { ... };
    (@to_pair $map:expr_2021, $name:expr_2021 => $value:expr_2021) => { ... };
    (@to_pair $map:expr_2021, $name:ident) => { ... };
    (@expand $map:expr_2021;) => { ... };
    (@expand $map:expr_2021; $name:expr_2021 => $value:expr_2021, $($tail:tt)*) => { ... };
    (@expand $map:expr_2021; $name:expr_2021 => $value:expr_2021 $(, $tail:tt)*) => { ... };
    (@expand $map:expr_2021; $name:ident, $($tail:tt)*) => { ... };
    (@expand $map:expr_2021; $name:ident $(, $tail:tt)*) => { ... };
    ($i:ident, $($tail:tt)*) => { ... };
    ($i:expr_2021 => $($tail:tt)*) => { ... };
    ($i:ident) => { ... };
}

This macro is a convenient way to pass named parameters to a statement.

let foo = 42;
conn.prep_exec("SELECT :foo, :foo2x", params! {
    foo,
    "foo2x" => foo * 2,
});