Allow to forget about borrowing outside scoping

[uzytkownik]

It's more of a paper cut but I find it tedious to write code in following fashion:

let (foo, bar, almost_all_variables) = {
     let foobar = borrow_some_variable;
     let foo = borrow_some_variable.foo();
     let bar = borrow_some_variable.bar();
     ...
     (foo, bar, almost_all_variables)
};
// Here I cannot have a borrowed variable
let (foobar, ....) = {

I would prefer to have something like:

let foobar = borrow_some_variable;
let foo = borrow_some_variable.foo();
let bar = borrow_some_variable.bar();
...
forger foobar;
// We behave as if we exited scope of foobar and all dependent variables but with autoexport of them

Or at least some syntax sugar over the top:

scoped! {
     let foobar = borrow_some_variable;
     outer!(let foo = borrow_some_variable.foo()); // Export to outer scop
     outer!(let bar = borrow_some_variable.bar());
};

[durka]

This is covered under "non-lexical lifetimes" -- once those are implemented, then drop(foobar); where foobar is a reference will work. See http://smallcultfollowing.com/babysteps/blog/2016/04/27/non-lexical-lifetimes-introduction/

[hanna-kruppe]

Part of rust-lang/rfcs#811

[Thiez]

This is covered under "non-lexical lifetimes" -- once those are implemented, then drop(foobar); where foobar is a reference will work. See http://smallcultfollowing.com/babysteps/blog/2016/04/27/non-lexical-lifetimes-introduction/

Surely that would only work for &mut T references, since &T references are Copy?

[nikomatsakis]

I'm going to close this as "the basic point of NLL" -- it seems like too general of a bug report to be actionable just now. @uzytkownik, if you like you may experiment with NLL by doing #![feature(nll)], and if you encounter problems, please do file issues! =)