gistfile1.txt

fn main() {
  let mut x: i32 = 17;
  let     y: i32 = 21;
 
  let mut u: Vec<&/* '0 */ i32> = vec![];
  let mut v: Vec<&/* '1 */ i32> = vec![];
 
  /* { // NLL */
 
  let p: &/* '3 */ i32 = &/* '2 */x; // Hence: '3: '5
  let q: &/* '5 */ i32 = &/* '4 */y; // Hence: '4: '5
 
  let mut r: &/* '6 */ mut Vec<&/* '7 */ i32>;
 
  r = &/* '8 */ mut u;      // Hence: {'8: '6, '0 = '7}
  r.push(p);                // Hence: '3: '7
 
  // Here, the value of `r` is dead. The analysis as I specified
  // it would therefore discard relations that directly involve
  // '6 and '7 but keep transitive relations.
  //
  // In this case ,that means ('3: '0) is retained.
 
  r = &/* '9 */ mut v;      // Hence: {'9: '6, '1 = '7}
  r.push(q);                // Hence: '5: '7

  // Again, the value of `r` is dead, but ('5: '0) is retained.

  /* } // NLL */
 
  // Here: we could conclude that the borrows of `p` and `q` are in scope,
  // yes, and hence prohibit mutation of `x` (and `y`). 
  
  x += 1; // <-- Error! can't mutate `x` while borrowed by `u` through `p`
          // If `'0 == '1 == '7`, could the analysis (wrongly) conclude
          // that the borrowing by `v` is also problematic?
 
  take(v);
}