rust/src/test/mir-opt/array-index-is-temporary.rs

// Retagging (from Stacked Borrows) relies on the array index being a fresh
// temporary, so that side-effects cannot change it.
// Test that this is indeed the case.

unsafe fn foo(z: *mut usize) -> u32 {
    *z = 2;
    99
}

// EMIT_MIR_FOR_EACH_BIT_WIDTH
// EMIT_MIR rustc.main.SimplifyCfg-elaborate-drops.after.mir
fn main() {
    let mut x = [42, 43, 44];
    let mut y = 1;
    let z: *mut usize = &mut y;
    x[y] = unsafe { foo(z) };
}