--[[
	diag_line277.luau -- the build harness died at CarManager:277 with
	"attempt to concatenate string with nil", but line 277 of the LOCAL file is
	a comment. So the code that ran is not the code on disk.

	Two candidates:
	  (a) the pushed Source is out of sync with disk
	  (b) require() handed back a STALE CACHED module from earlier this session
	      (the known Studio trap: editing Source does NOT invalidate the cache)

	This reads the Source text directly -- never require() -- and prints the
	real lines around 277, plus the reverted-convention markers, so we can tell
	(a) from (b) instead of guessing.
]]

local RS = game:GetService("ReplicatedStorage")
local SSS = game:GetService("ServerScriptService")

local function find(name)
	for _, root in ipairs({ SSS, RS, game:GetService("ServerStorage"), workspace }) do
		local m = root:FindFirstChild(name, true)
		if m and m:IsA("ModuleScript") then
			return m
		end
	end
	return nil
end

local cm = find("CarManager")
if not cm then
	return "FATAL: CarManager not found"
end

local src = cm.Source
local lines = {}
for l in (src .. "\n"):gmatch("([^\n]*)\n") do
	table.insert(lines, l)
end

local out = {}
table.insert(out, string.format("%s  %d bytes, %d lines", cm:GetFullName(), #src, #lines))
table.insert(out, "")
table.insert(out, "--- Studio Source lines 270..284 ---")
for i = 270, math.min(284, #lines) do
	table.insert(out, string.format("%4d | %s", i, lines[i]))
end

table.insert(out, "")
table.insert(out, "--- markers ---")
table.insert(out, "  isFront = zSign < 0 present : " .. tostring(src:find("isFront = zSign < 0", 1, true) ~= nil))
table.insert(out, "  _buildForDiag present       : " .. tostring(src:find("_buildForDiag", 1, true) ~= nil))

-- Where does _buildForDiag get assigned, per the Studio copy?
for i, l in ipairs(lines) do
	if l:find("_buildForDiag", 1, true) then
		table.insert(out, string.format("  _buildForDiag at line %d: %s", i, l))
	end
end

-- What does buildCarModel expect? Print its declaration line.
for i, l in ipairs(lines) do
	if l:find("function buildCarModel", 1, true) or l:find("local function buildCarModel", 1, true) then
		table.insert(out, string.format("  buildCarModel declared line %d: %s", i, l))
	end
end

return table.concat(out, "\n")