Update E0384.md

[JimmyOhn]

Add an example for the shadowing usage.

[rustbot]

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[JimmyOhn]

IMHO, we can use the shadowing instead. I think it's better to understand Rust first time like me.
I tested with my changes as follows.
refer to : https://rustc-dev-guide.rust-lang.org/building/quickstart.html

rustc +stage1 --explain E0384

An immutable variable was reassigned.

Erroneous code example:

fn main() {
    let x = 3;
    x = 5; // error, reassignment of immutable variable
}

By default, variables in Rust are immutable. To fix this error, add the keyword mut after the keyword let when
declaring the variable. For example:

fn main() {
    let mut x = 3;
    x = 5;
}

Otherwise you can use the shadowing instead. declared variable will be destroyed when declaring the same
variable. For example:

fn main() {
    let x = 3;
    let x = 5;
}
(END)

[pnkfelix]

@bors r+ rollup

[bors]

📌 Commit 0b5653f has been approved by pnkfelix

It is now in the queue for this repository.