reinitialization with let

What it does

If an assignment dominate all usages where it can reach, assignment can be replaced by a let bind, instead of overwrite

Advantage

• less mut
• like functional programming
• explicit dominance
• helpful in jumpping to definition in ide

Drawbacks

None (not sure)

Example

 let mut x = "hello".to_string();
    let mut y = vec![];

    y.push(x);

    x = "goodbye".to_string();

    println!("{}", x); 

Could be written as:

 let mut x = "hello".to_string();
    let mut y = vec![];

    y.push(x);

    let x = "goodbye".to_string();

    println!("{}", x); 

Start by reviewing the issue's Rust examples and the linked pull request #11687 to understand the proposed reinitialization behavior. Determine the intended lint scope, its handling of dominance and later bindings, and the tests needed to establish when the transformation is valid; done means the behavior and acceptance criteria are agreed.