Macro screaming 

macro_rules! screaming {
    ($ident:expr => ident) => { ... };
    ($s:expr) => { ... };
}

Converts a string or ident to SCREAMING_SNAKE_CASE.

• screaming!("HelloWorld") → "HELLO_WORLD" (String)
• screaming!(ident => ident) → SCREAMING_SNAKE_CASE syn::Ident