`move` `Copy` values

Copy values have special copy semantics, when they're moved away, the old place still have valid value alive. A lot of times this is not people want. For example, it's very easy to typo and wrongly use some temporary values after they have been sent away with assignment.

If possible, i'd propose a move expression:

`move` `(` expr `)`

The parenthesis are for avoiding the ambiguity with move closures.

Example:

let a = 42;
x.a = move(a);
double(&mut x.a);
dbg!(a);  // compile error

Alternatives:

• unlet a;
• a.move
• let a = 42 in { ... };

This is a language-design proposal for changing how moved Copy values behave, with move(expr) and several alternatives listed. Start by reviewing Rust's existing move and Copy semantics and the RFC process; done would require an agreed design and accepted RFC rather than a localized code change.