Well, I see your point. But here we are presuming "no investigation" on the OP part, no?
The Lua community is much more technically adept than average bunch of programmers and as such I expect a little more self investigation before asking a question. Simple ones like "Why does the number of local variables I declare affect which part of the table assignment errors?" or "Why does Lua not assign a local variable only once?" raise themselves after only a brief time spent playing with luac -l and the original program.
There are other variants of the original program, such as one where there are thousands of 0s, before the nested table. The fact that it is 50 elements before the nested table is a red herring and one that would be quickly found. Likewise why is it the inline nesting of a table that triggers the error and not when it is added as a separate step "a[#a] = {1,1,....1}"?
> Why such short code is considered to be "too complex"?
Does not seem to touch on any of the issues that the code raises. Which I why I believe that the poster has conducted no investigation.