Macro lalrpop_lambda::abs

macro_rules! abs {
    {. $body:ident} => { ... };
    {. $body:expr} => { ... };
    {$($arg:ident : $ty:ident)* . $body:ident} => { ... };
    {$($arg:ident)* . $body:ident} => { ... };
    {$($arg:ident : $ty:ident)* . $body:expr} => { ... };
    {$($arg:ident)* . $body:expr} => { ... };
}

An abstraction (Abs) expression