checker: fix mut var option unwrap with != none, support `if mut x …
#268
| Job | Run time |
|---|---|
| 1m 47s | |
| 1m 45s | |
| 3m 32s |
!= none, support `if mut x …
#268
| Job | Run time |
|---|---|
| 1m 47s | |
| 1m 45s | |
| 3m 32s |