rust/tests/ui/closures/2229_closure_analysis/diagnostics/cant-mutate-imm-borrow.rs

// edition:2021

// Test that if we deref an immutable borrow to access a Place,
// then we can't mutate the final place.

fn main() {
    let mut x = (format!(""), format!("X2"));
    let mut y = (&x, "Y");
    let z = (&mut y, "Z");

    // `x.0` is mutable but we access `x` via `*z.0.0`, which is an immutable reference and
    // therefore can't be mutated.
    let mut c = || {
    //~^ ERROR: cannot borrow `*z.0.0` as mutable, as it is behind a `&` reference
        z.0.0.0 = format!("X1");
    };

    c();
}