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Jeongseop LimandJeong YunWon
c271e33214
* Count positional arguments before converting any FuncArgs::bind_for rejected surplus positional arguments only after FromArgs::from_args had converted every declared parameter. A conversion can run user code (__iter__ for PyIter, __index__ for ArgIndex), so filter(None, it, 0), hex(x, 1) and pairwise(it, 0) raised whatever that code raised instead of the TypeError CPython reports before it touches any argument. Check the count against FromArgs::arity() before from_args runs. For that bound to be safe: - The default arity() has no upper bound, since a manual impl may take positional arguments itself. KwArgs, (), DirFd, OpenDirFd and csv's FormatOptions declare the bound they actually have. - A derived struct adds the upper bound of each flattened field. - A tuple sums upper bounds with saturating_add. Assisted-by: Claude Code:claude-opus-5-5 * Note why arity upper bounds saturate Comment that an unbounded upper bound is usize::MAX, which is why the tuple and derived arity() sums use saturating_add, and drop the CPython mention from the positional count check comment. Assisted-by: Claude Code:claude-opus-5-5 --------- Co-authored-by: Jeong YunWon <jeong@youknowone.org>