[OTHER] Consider calling ptr::drop_in_place inside StackVec::truncate_unchecked

[str4d]

Description

minimal-lexical/src/stackvec.rs

Lines 155 to 163 in e997c46

	/// Truncate vector to new length, dropping any items after `len`.
	///
	/// # Safety
	///
	/// Safe as long as `len <= self.capacity()`.
	unsafe fn truncate_unchecked(&mut self, len: usize) {
	debug_assert!(len <= self.capacity());
	self.length = len as u16;
	}

This is technically sound as-is, because Limb is defined as an alias to either u32 or u64. But if in some future refactor Limb became a type with a real Drop impl, this code would become unsound.

Looping over the truncated elements and calling ptr::drop_in_place would future-proof this part of the code, while hopefully being optimised out by LLVM for the current Drop-less Limb types.

Additional Context

I'm in the process of migrating Fuchsia to use nom 7, which depends on minimal-lexical 0.1, and am opening issues in response to review comments (visible here: https://fuchsia-review.googlesource.com/c/fuchsia/+/589324).