Constant shadowing

---

examples/constants/constant-shadowing/src/main.rs

fn main() {
    const NAME: &str = "Foo";
    println!("name={NAME}");

    {
        println!("name={NAME}");
        const NAME: &str = "Bar";
        println!("name={NAME}");
    }
    println!("name={NAME}");
}

name=Foo
name=Bar
name=Bar
name=Foo