src/test/run-pass/unboxed-closures-counter-not-moved.rs

   1 // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 // Test that we mutate a counter on the stack only when we expect to.
  12
  13 fn call<F>(f: F) where F : FnOnce() {
  14     f();
  15 }
  16
  17 fn main() {
  18     let y = vec![format!("Hello"), format!("World")];
  19     let mut counter = 22_u32;
  20
  21     call(|| {
  22         // Move `y`, but do not move `counter`, even though it is read
  23         // by value (note that it is also mutated).
  24         for item in y {
  25             let v = counter;
  26             counter += v;
  27         }
  28     });
  29     assert_eq!(counter, 88);
  30
  31     call(move || {
  32         // this mutates a moved copy, and hence doesn't affect original
  33         counter += 1;
  34     });
  35     assert_eq!(counter, 88);
  36 }