Fix circular reference detection to notice that OpSet passes around l…

…hs/rhs as a single var, not multiple

docsrc/cli.rst

@@ -117,7 +117,7 @@ Option                                  Meaning
 ``--ignore | -i <patt> [<patt>] ...``   Filter out warnings matching patterns.
 ``--enable | -e <patt> [<patt>] ...``   Do not filter out warnings matching patterns.
 ``--only | -o <patt> [<patt>] ...``     Filter out warnings not matching patterns.
-``--operators <patt> [<patt>] ...``     Allow compound operators matching patterns.
+``--operators <patt> [<patt>] ...``     Allow compound operators matching patterns. (Multiple assignment not supported, as this is specifically for the Playdate SDK.)
 ``--config <config>``                   Path to custom configuration file (default: ``.luacheckrc``).
 ``--no-config``                         Do not look up custom configuration file.
 ``--default-config <config>``           Default path to custom configuration file, to be used if ``--[no-]config`` is not used and ``.luacheckrc`` is not found.

src/luacheck/stages/resolve_locals.lua

@@ -96,18 +96,18 @@ end
 
 local function is_circular_reference(item, var)
    -- No support for matching multiple assignment to the specific assignment
-   if not item.lhs or #item.lhs ~= 1 or not item.rhs or #item.rhs ~= 1 then
+   if not (item.tag == "Set" or item.tag == "Local" or item.tag == "OpSet") then
       return false
    end
 
    -- Case t[t.function()] = t.func()
    -- Functions can have side-effects, so this isn't purely circular
-   local right_assignment = item.rhs[1]
+   local right_assignment = item.tag == "OpSet" and item.rhs or item.rhs[1]
    if contains_call(right_assignment) then
       return false
    end
 
-   local left_assignment = item.lhs[1]
+   local left_assignment = item.tag == "OpSet" and item.lhs or item.lhs[1]
    if contains_call(left_assignment) then
       return false
    end