zeroize: `Vec<Z>::zeroize()` zeroizes the initialized elements twice

[chpio]

Hi!

utils/zeroize/src/lib.rs

Lines 528 to 536 in 03a330e

	fn zeroize(&mut self) {
	// Zeroize all the initialized elements.
	self.iter_mut().zeroize();
	// Set the Vec's length to 0 and drop all the elements.
	self.clear();
	// Zero the full capacity of `Vec`.
	self.spare_capacity_mut().zeroize();

:

fn zeroize(&mut self) {
    // Zeroize all the initialized elements.
    self.iter_mut().zeroize();

    // Set the Vec's length to 0 and drop all the elements.
    self.clear();

    // Zero the full capacity of `Vec`.
    self.spare_capacity_mut().zeroize();
}

After self.clear(), len is 0, so self.spare_capacity_mut() in the third step covers the entire allocation, including the range that was already zeroized by the first step.

Is there are reason for that? If so, a comment might help.

Thank you