src/test/ui/borrowck/borrowck-lend-flow-loop.rs

   1 fn borrow(_v: &isize) {}
   2 fn borrow_mut(_v: &mut isize) {}
   3 fn cond() -> bool { panic!() }
   4 fn produce<T>() -> T { panic!(); }
   5
   6
   7 fn inc(v: &mut Box<isize>) {
   8     *v = Box::new(**v + 1);
   9 }
  10
  11
  12 fn loop_overarching_alias_mut() {
  13     // In this instance, the borrow ends on the line before the loop
  14
  15     let mut v: Box<_> = Box::new(3);
  16     let mut x = &mut v;
  17     **x += 1;
  18     loop {
  19         borrow(&*v); // OK
  20     }
  21 }
  22
  23 fn block_overarching_alias_mut() {
  24     // In this instance, the borrow encompasses the entire closure call.
  25
  26     let mut v: Box<_> = Box::new(3);
  27     let mut x = &mut v;
  28     for _ in 0..3 {
  29         borrow(&*v); //~ ERROR cannot borrow
  30     }
  31     *x = Box::new(5);
  32 }
  33 fn loop_aliased_mut() {
  34     // In this instance, the borrow ends right after each assignment to _x
  35
  36     let mut v: Box<_> = Box::new(3);
  37     let mut w: Box<_> = Box::new(4);
  38     let mut _x = &w;
  39     loop {
  40         borrow_mut(&mut *v); // OK
  41         _x = &v;
  42     }
  43 }
  44
  45 fn while_aliased_mut() {
  46     // In this instance, the borrow ends right after each assignment to _x
  47
  48     let mut v: Box<_> = Box::new(3);
  49     let mut w: Box<_> = Box::new(4);
  50     let mut _x = &w;
  51     while cond() {
  52         borrow_mut(&mut *v); // OK
  53         _x = &v;
  54     }
  55 }
  56
  57
  58 fn loop_aliased_mut_break() {
  59     // In this instance, the borrow ends right after each assignment to _x
  60
  61     let mut v: Box<_> = Box::new(3);
  62     let mut w: Box<_> = Box::new(4);
  63     let mut _x = &w;
  64     loop {
  65         borrow_mut(&mut *v);
  66         _x = &v;
  67         break;
  68     }
  69     borrow_mut(&mut *v); // OK
  70 }
  71
  72 fn while_aliased_mut_break() {
  73     // In this instance, the borrow ends right after each assignment to _x
  74
  75     let mut v: Box<_> = Box::new(3);
  76     let mut w: Box<_> = Box::new(4);
  77     let mut _x = &w;
  78     while cond() {
  79         borrow_mut(&mut *v);
  80         _x = &v;
  81         break;
  82     }
  83     borrow_mut(&mut *v); // OK
  84 }
  85
  86 fn while_aliased_mut_cond(cond: bool, cond2: bool) {
  87     let mut v: Box<_> = Box::new(3);
  88     let mut w: Box<_> = Box::new(4);
  89     let mut x = &mut w;
  90     while cond {
  91         **x += 1;
  92         borrow(&*v); //~ ERROR cannot borrow
  93         if cond2 {
  94             x = &mut v; // OK
  95         }
  96     }
  97 }
  98 fn loop_break_pops_scopes<'r, F>(_v: &'r mut [usize], mut f: F) where
  99     F: FnMut(&'r mut usize) -> bool,
 100 {
 101     // Here we check that when you break out of an inner loop, the
 102     // borrows that go out of scope as you exit the inner loop are
 103     // removed from the bitset.
 104
 105     while cond() {
 106         while cond() {
 107             // this borrow is limited to the scope of `r`...
 108             let r: &'r mut usize = produce();
 109             if !f(&mut *r) {
 110                 break; // ...so it is not live as exit the `while` loop here
 111             }
 112         }
 113     }
 114 }
 115
 116 fn loop_loop_pops_scopes<'r, F>(_v: &'r mut [usize], mut f: F)
 117     where F: FnMut(&'r mut usize) -> bool
 118 {
 119     // Similar to `loop_break_pops_scopes` but for the `loop` keyword
 120
 121     while cond() {
 122         while cond() {
 123             // this borrow is limited to the scope of `r`...
 124             let r: &'r mut usize = produce();
 125             if !f(&mut *r) {
 126                 continue; // ...so it is not live as exit (and re-enter) the `while` loop here
 127             }
 128         }
 129     }
 130 }
 131
 132 fn main() {}