The error message,using expected and unexpected

Property definitions

nitcc_runtime $ NError :: message
	# The error message,using `expected` and `unexpected`
	fun message: String
	do
		var exp = expected
		var res = "Unexpected {unexpected}"
		if exp != null then res += "; is acceptable instead: {exp}"
		return res
	end
lib/nitcc_runtime/nitcc_runtime.nit:518,2--525,4