| error[E0381]: used binding `cfg_res` is possibly-uninitialized | 
 |   --> $DIR/try-block-opt-init.rs:15:5 | 
 |    | | 
 | LL |     let cfg_res; | 
 |    |         ------- binding declared here but left uninitialized | 
 | ... | 
 | LL |         cfg_res = 5; | 
 |    |         ----------- binding initialized here in some conditions | 
 | ... | 
 | LL |     assert_eq!(cfg_res, 5); | 
 |    |     ^^^^^^^^^^^^^^^^^^^^^^ `cfg_res` used here but it is possibly-uninitialized | 
 |    | | 
 |    = note: this error originates in the macro `assert_eq` (in Nightly builds, run with -Z macro-backtrace for more info) | 
 |  | 
 | error: aborting due to 1 previous error | 
 |  | 
 | For more information about this error, try `rustc --explain E0381`. |