New type solver throws type error with unclear message when return type is optional

[Daw588]

The new type solver throws type error with unclear message when return type is optional and the return keyword is used without a value.

function RandBool(): boolean?
	if math.random() > 0.5 then
		return true
	end
	return -- TypeError: Type pack '' could not be converted into 'boolean?' Luau(1035)
end

However, this does not occur when the return keyword is used with nil.

function RandBool(): boolean?
	if math.random() > 0.5 then
		return true
	end
	return nil -- OK
end

[aatxe]

Thanks for the report, agreed the error message could definitely be better here, but an empty typepack is indeed not at the type boolean? (you can observe the difference by select('#', ...) on the result of your two versions of RandBool).