[laurenth]

It seems ShellCheck errs on the side of caution when checking arithmetic expansions and some of its recommendations are not relevant in the context they are given. For example, on `cat.sh`, one of the lines that are marked in red is:

  In examples/compiled/cat.sh line 7:
    : $((_$__ALLOC = $2)) # Track object size
      ^-- SC1102 (error): Shells disambiguate $(( differently or not at all. For $(command substitution), add space after $( . For $((arithmetics)), fix parsing errors.
      ^-----------------^ SC2046 (warning): Quote this to prevent word splitting.
        ^--------------^ SC2205 (warning): (..) is a subshell. Did you mean [ .. ], a test expression?
                   ^-- SC2283 (error): Remove spaces around = to assign (or use [ ] to compare, or quote '=' if literal).
                     ^-- SC2086 (info): Double quote to prevent globbing and word splitting.

It seems to be parsing the arithmetic expansion as a command substitution, which then causes the analyzer to produce errors that aren't relevant. ShellCheck's own documentation[0] mention this in the exceptions section, and the code is generated such that quoting and word splitting are not an issue (because variables never contain whitespace or special characters).

It also warns about `let` being undefined in POSIX shell, but `let` is defined in the shell script so it's a false positive that's caused by the use of the `let` keyword specifically.

If you think there are other issues or ways to improve Pnut's compatibility with Shellcheck, please let us know!

0: https://www.shellcheck.net/wiki/SC1102