Idea: outside consts colliding local variables in macros

[oxalica]

In quiz 35 we use colored-local-vars analogy for both variables inside and outside macros, and in quiz 24 we mentioned consts are uncolored. From these, I thought local variables inside macros would still be safe from collision because they are "colored". But that's not the case. Maybe it worths another quiz, or could we expanding quiz 24?

fn main() {
    macro_rules! m {
        () => {
            // could also be `let foo = 42;` but it would give a compile error.
            match Some(42i32) {
                Some(foo) => println!("some"),
                _ => println!("other"),
            }
        };
    }

    { m!(); }
    {
        const foo: i32 = 24;
        m!();
    }
    {
        let foo = 24;
        m!();
    }
}

This code prints:

some
other
some