loops can break with a value

Minimum Rust version: 1.19

loops can now break with a value:

  2. #![allow(unused_variables)]
  3. fn main() {
  4. // old code
  5. let x;
  7. loop {
  8.     x = 7;
  9.     break;
  10. }
  12. // new code
  13. let x = loop { break 7; };
  14. }

Rust has traditionally positioned itself as an “expression orientedlanguage”, that is, most things are expressions that evaluate to a value,rather than statements. loop stuck out as strange in this way, as it waspreviously a statement.

For now, this only applies to loop, and not things like while or for.See the rationale for this decision in RFC issue #1767.