Tracking Issue for mem_reshape

[hazelwiss]

Feature gate: #![feature(mem_reshape)]

This is a tracking issue for core::mem::reshape.

core::mem::reshape allows modifying a mutable reference with its moved underlying value.

Public API

// core::mem

let mut x = "some_string".to_string();
reshape(&mut x, |x|  x + " that is reshaped");

println!("{x}");

Steps / History

• Implementation: added core::mem::reshape #130849
• Final comment period (FCP)¹
• Stabilization PR

Unresolved Questions

• None yet.

Footnotes

1. https://std-dev-guide.rust-lang.org/feature-lifecycle/stabilization.html ↩

[workingjubilee]

The example is poorly-motivated because it is easily done using AddAssign:

fn mut_ref_boundary(s: &mut String) {
    *s += " that is reshaped";
}

let mut x = "some_string".to_string();
mut_ref_boundary(&mut x);

println!("{x}");

The cases where we need this function, also called replace_with, are somewhat complex. If we were to add it, we would need a similarly somewhat complex example, or else we would not be able to explain what it is actually needed for.