Why I cannot compare two `&'static str`s in a const context?

8

My final code is like:

    const fn const_bytes_equal(lhs: &[u8], rhs: &[u8]) -> bool {
        if lhs.len() != rhs.len() {
            return false;
        }
        let mut i = 0;
        while i < lhs.len() {
            if lhs[i] != rhs[i] {
                return false;
            }
            i += 1;
        }
        true
    }
    
    const fn const_str_equal(lhs: &str, rhs: &str) -> bool {
        const_bytes_equal(lhs.as_bytes(), rhs.as_bytes())
    }

    macro_rules! id_name_conv {
        ($($id:literal -> $name:literal)*) => {
            const fn id2name(id: u32) -> &'static str {
                match id {
                    $($id => $name,)*
                    _ => unreachable!(),
                }
            }
    
            const fn name2id(name: &'static str) -> u32 {
                $(if const_str_equal(name, $name) {
                    return $id
                })*
                unreachable!();
            }
        };
    }
    
    id_name_conv!(
        0 -> "a"
        1 -> "b"
    );
    
    assert_eq!(id2name(0), "a");
    assert_eq!(name2id("b"), 1);
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