Macro stringlet 

macro_rules! stringlet {
    (_:  $($rest:tt)+) => { ... };
    (var  $($rest:tt)+) => { ... };
    (v  $($rest:tt)+) => { ... };
    (slim  $($rest:tt)+) => { ... };
    (s  $($rest:tt)+) => { ... };
    ($size:tt $(@ $align:tt)?: $($rest:tt)+) => { ... };
    (@ $align:tt: $($rest:tt)+) => { ... };
    ($($rest:tt)+) => { ... };
}

Turn a const str expression into the smallest Stringlet that can contain it. Shorthand to optionally give generic parameters SIZE and FIXED. For now, please check README.md.

These are equivalent:

let s1 = stringlet!("abc");
let s2: Stringlet<3> = stringlet!("abc");
let s3 = stringlet!(" abc ".trim_ascii());
assert_eq!(s1, s2);
assert_eq!(s2, s3);

As are these:

let s1 = stringlet!("abcdefghijklmno");
let s2: Stringlet<15> = stringlet!("abcdefghijklmno");
let s3 = stringlet!(concat!("abcdefgh", 'i', "jklmno"));
assert_eq!(s1, s2);
assert_eq!(s2, s3);