Macro lalrpop_lambda::map

macro_rules! map {
    (@single $($x:tt)*) => { ... };
    (@count $($rest:expr),*) => { ... };
    ($($key:expr => $value:expr,)+) => { ... };
    ($($key:expr => $value:expr),*) => { ... };
}

A HashMap macro like vec!

map! { 'a' => 1, 'b' => 2, 'c' => 3 };
map! { 'a' => "a", 'b' => "b", 'c' => "c" };