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armanriazi•rust•error•E0501•cannot borrow `x` as immutable because previous closure requires unique access

ArmanRiazi answered on May 27, 2022 Popularity 1/10 Helpfulness 1/10

answer armanriazi•rust•error•E0501•cannot borrow `x` as immutable because previous closure requires unique access

armanriazi•rust•error•E0501•cannot borrow `x` as immutable because previous closure requires unique access

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/// # In this case, borrowing x mutably is not possible, because x is not mut. But at the same time, borrowing x immutably would make the assignment illegal, because a & &mut reference might not be unique, so it cannot safely be used to modify a value. So a unique immutable borrow is used: it borrows x immutably, but like a mutable borrow, it must be unique.
/// In the above example, uncommenting the declaration of y will produce an error because it would violate the uniqueness of the closure's borrow of x; the declaration of z is valid because the closure's lifetime has expired at the end of the block, releasing the borrow.#

#![allow(unused)]
fn main() {
let mut b = false;
let x = &mut b;
{
    let mut c = || { *x = true; };
    // The following line is an error:
    // let y = &x;
    c();
}
let z = &x;
}

Popularity 1/10 Helpfulness 1/10 Language rust

Source: Grepper

Tags: borrow requires rust unique

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Contributed on May 27 2022

ArmanRiazi

0 Answers Avg Quality 2/10

armanriazi•rust•error•E0501•cannot borrow `x` as immutable because previous closure requires unique access

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