src/librustc_error_codes/error_codes/E0434.md

   1 A variable used inside an inner function comes from a dynamic environment.
   2
   3 Erroneous code example:
   4
   5 ```compile_fail,E0434
   6 fn foo() {
   7     let y = 5;
   8     fn bar() -> u32 {
   9         y // error: can't capture dynamic environment in a fn item; use the
  10           //        || { ... } closure form instead.
  11     }
  12 }
  13 ```
  14
  15 Inner functions do not have access to their containing environment. To fix this
  16 error, you can replace the function with a closure:
  17
  18 ```
  19 fn foo() {
  20     let y = 5;
  21     let bar = || {
  22         y
  23     };
  24 }
  25 ```
  26
  27 Or replace the captured variable with a constant or a static item:
  28
  29 ```
  30 fn foo() {
  31     static mut X: u32 = 4;
  32     const Y: u32 = 5;
  33     fn bar() -> u32 {
  34         unsafe {
  35             X = 3;
  36         }
  37         Y
  38     }
  39 }
  40 ```