Macro lazy

macro_rules! lazy {
    { move $($body:tt)* } => { ... };
    { $($body:tt)* } => { ... };
}

Construct a value lazily (for expressions that return Result, use lazyresult) (Todo: update to not require &mut)

Construct a Lazy value that runs the code body given to the macro once on the first call to force. Moves the captured values if a move keyword is given as the first item in the body. If the body evaluates to a Result, better use lazyresult! instead because Result is generally not cloneable and thus force()? won’t work.