Expanding an expandable primitive unknown to unravel, such as \directlua in LuaTeX, incorrectly puts it into the output (not even into the current prev_input) rather than for instance producing an undefined control sequence error or similar. Example:
Expanding an expandable primitive unknown to
unravel, such as\directluain LuaTeX, incorrectly puts it into the output (not even into the current prev_input) rather than for instance producing an undefined control sequence error or similar. Example: