src/test/ui/consts/control-flow/interior-mutability.rs

   1 // Ensure that *any* assignment to the return place of a value with interior mutability
   2 // disqualifies it from promotion.
   3
   4 use std::cell::Cell;
   5
   6 const X: Option<Cell<i32>> = {
   7     let mut x = None;
   8     if false {
   9         x = Some(Cell::new(4));
  10     }
  11     x
  12 };
  13
  14 const Y: Option<Cell<i32>> = {
  15     let mut y = Some(Cell::new(4));
  16     if true {
  17         y = None;
  18     }
  19     y
  20 };
  21
  22 const Z: Option<Cell<i32>> = {
  23     let mut z = None;
  24     let mut i = 0;
  25     while i < 10 {
  26         if i == 8 {
  27             z = Some(Cell::new(4));
  28         }
  29
  30         if i == 9 {
  31             z = None;
  32         }
  33
  34         i += 1;
  35     }
  36     z
  37 };
  38
  39 fn main() {
  40     let x: &'static _ = &X; //~ ERROR temporary value dropped while borrowed
  41     let y: &'static _ = &Y; //~ ERROR temporary value dropped while borrowed
  42     let z: &'static _ = &Z; //~ ERROR temporary value dropped while borrowed
  43 }