rust/tests/mir-opt/early_otherwise_branch_soundness.rs

// skip-filecheck
//@ unit-test: EarlyOtherwiseBranch

// Tests various cases that the `early_otherwise_branch` opt should *not* optimize

// From #78496
enum E<'a> {
    Empty,
    Some(&'a E<'a>),
}

// EMIT_MIR early_otherwise_branch_soundness.no_downcast.EarlyOtherwiseBranch.diff
fn no_downcast(e: &E) -> u32 {
    if let E::Some(E::Some(_)) = e { 1 } else { 2 }
}

// SAFETY: if `a` is `Some`, `b` must point to a valid, initialized value
// EMIT_MIR early_otherwise_branch_soundness.no_deref_ptr.EarlyOtherwiseBranch.diff
unsafe fn no_deref_ptr(a: Option<i32>, b: *const Option<i32>) -> i32 {
    match a {
        // `*b` being correct depends on `a == Some(_)`
        Some(_) => match *b {
            Some(v) => v,
            _ => 0,
        },
        _ => 0,
    }
}

fn main() {
    no_downcast(&E::Empty);
    unsafe { no_deref_ptr(None, std::ptr::null()) };
}