Add fix for broken test

src/NoYield.lua

@@ -10,8 +10,15 @@
 
 local function resultHandler(co: thread, ok: boolean, ...)
 	if not ok then
-		local message = (...)
-		error(debug.traceback(co, message), 2)
+		local err = (...)
+		if typeof(err) == "string" then
+			error(debug.traceback(co, err), 2)
+		else
+			-- If the error is not of type string, just assume it has some
+			-- meaningful information and rethrow it with a `tostring` so that
+			-- top-level error handlers can process it
+			error(tostring(err), 2)
+		end
 	end
 
 	if coroutine.status(co) ~= "dead" then

src/NoYield.spec.lua

@@ -53,4 +53,30 @@ return function()
 		expect(err:find("foo")).to.be.ok()
 		expect(err:find("NoYield.spec")).to.be.ok()
 	end)
+
+	it("should handle non-string error messages", function()
+		local count = 0
+
+		local function makeErrorObject()
+			return setmetatable({
+				message = "errored with an error object",
+				stack = debug.traceback(),
+			}, {
+				__tostring = function(self)
+					return self.message .. "\n" .. self.stack
+				end,
+			})
+		end
+
+		local function test()
+			count = count + 1
+			error(makeErrorObject())
+		end
+
+		local ok, err = pcall(NoYield, test)
+
+		expect(ok).to.equal(false)
+		expect(err:find("errored with an error object")).to.be.ok()
+		expect(err:find("NoYield.spec")).to.be.ok()
+	end)
 end