Logical functions aliases

[arnaudgolfouse]

Example

// In `creusot_contracts`

impl<K, V> FMap<K, V> {
    #[trusted]
    #[logic]
    #[ensures(result >= 0)]
    pub fn len_logic(self) -> Int {
        dead
    }

    #[trusted]
    #[pure]
    #[has_logical_alias(Self::len_logic)]
    pub fn len(self) -> Int {
        panic!()
    }
}

// User code

pub fn foo() {
    let mut m = FMap::new();
    proof_assert!(m.len() == 0); // logic call
    ghost! {
        m.insert_ghost(1int, 1int);
        let l = m.len(); // program (ghost) call
        proof_assert!(l == 1);
        m.insert_ghost(2int, 2int);
        proof_assert!(m.len() == 2);
    };
}