A failing CHECK has a higher precedence than a failing CHECK-NOT even if CHECK-NOT appears first in the check file. If this happens, the output is related to the failing CHECK, not the failing CHECK-NOT.
Input:
String1
Stringggg2
Check file:
CHECK-NOT:String1
CHECK:String2
Result:
/Users/Stanislaw/.pyenv/shims/filecheck
filecheck.check:2:7: error: CHECK: expected string not found in input
CHECK:String2
^
<stdin>:1:1: note: scanning from here
String1
^