src/librustc_error_codes/error_codes/E0409.md

   1 An "or" pattern was used where the variable bindings are not consistently bound
   2 across patterns.
   3
   4 Erroneous code example:
   5
   6 ```compile_fail,E0409
   7 let x = (0, 2);
   8 match x {
   9     (0, ref y) | (y, 0) => { /* use y */} // error: variable `y` is bound with
  10                                           //        different mode in pattern #2
  11                                           //        than in pattern #1
  12     _ => ()
  13 }
  14 ```
  15
  16 Here, `y` is bound by-value in one case and by-reference in the other.
  17
  18 To fix this error, just use the same mode in both cases.
  19 Generally using `ref` or `ref mut` where not already used will fix this:
  20
  21 ```
  22 let x = (0, 2);
  23 match x {
  24     (0, ref y) | (ref y, 0) => { /* use y */}
  25     _ => ()
  26 }
  27 ```
  28
  29 Alternatively, split the pattern:
  30
  31 ```
  32 let x = (0, 2);
  33 match x {
  34     (y, 0) => { /* use y */ }
  35     (0, ref y) => { /* use y */}
  36     _ => ()
  37 }
  38 ```