Hi, 

 I did some further test and found that the "function *** is not known
to be defined" error only happen once for either a undefined function
or a function defined in a nested structure, as seen in the attached
screenshot. 

1. The kkl0-fun, which is defined at top-level, linter shows no error 
   at all
2. The kkl1-fun is defined as *kk0l* global variable is assigned as t
3. The first linter error appears when the kkl1-fun is called first
time
4. At the second call-site of kkl1-fun, the linter "undefined-function"
error disappears 
5. the kkl2-fun is totally undefined, and linter identifies the
undefined function error at the first call-site
6. at the second call-site of kkl2-fun, the undefined-function linter
error disappears as well

So, it seems that elint starts to ignore undefined function starting
second call-site regardless that function is defined or not. we need
some further investigation on elint.el's elint-update-env function and
related functions. 

Thanks, 
Kiong-Gē.