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Merge pull request #569 from Nitrokey/default-len-type

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Make LenType opt-in
This commit is contained in:
Markus Reiter 2025-05-16 07:48:04 +00:00 committed by GitHub
commit 6b17767190
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7 changed files with 41 additions and 270 deletions
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2
CHANGELOG.md
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@ -11,6 +11,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
- `bytes::BufMut` is now implemented on `VecInner`.
- Removed generic from `history_buf::OldestOrdered`.
- Made `LenType` opt-in.
### Fixed
@ -19,6 +20,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
### Removed
- Removed invalid `bytes::Buf` implementation.
- Removed `DefaultLenType` struct.
## [v0.9.0] - 2025-04-28 [YANKED]

4
src/c_string.rs
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@ -1,6 +1,6 @@
//! A fixed capacity [`CString`](https://doc.rust-lang.org/std/ffi/struct.CString.html).
use crate::{len_type::DefaultLenType, vec::Vec, CapacityError, LenType};
use crate::{vec::Vec, CapacityError, LenType};
use core::{
borrow::Borrow,
cmp::Ordering,
@ -14,7 +14,7 @@ use core::{
///
/// It stores up to `N - 1` non-nul characters with a trailing nul terminator.
#[derive(Clone, Hash)]
pub struct CString<const N: usize, LenT: LenType = DefaultLenType<N>> {
pub struct CString<const N: usize, LenT: LenType = usize> {
inner: Vec<u8, N, LenT>,
}

180
src/len_type.rs
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@ -85,186 +85,6 @@ impl_lentype!(
usize
);
macro_rules! impl_lentodefault {
($LenT:ty: $($len:literal),*) => {$(
impl SmallestLenType for Const<$len> {
type Type = $LenT;
}
)*};
}
/// A struct to create individual types for mapping with [`SmallestLenType`].
///
/// See the documentation of [`DefaultLenType`] for a detailed explanation.
pub struct Const<const N: usize>;
/// A trait to map [`Const`] to it's respective [`LenType`].
///
/// See the documentation of [`DefaultLenType`] for a detailed explanation.
#[diagnostic::on_unimplemented(
message = "Length `N` does not have a default `LenType` mapping",
note = "Provide the `LenType` explicitly, such as `usize`"
)]
pub trait SmallestLenType {
type Type: LenType;
}
/// A type alias to perform the `const N: usize` -> `LenType` mapping.
///
/// This is impossible to perform directly, but it is possible to write a `const N: usize` -> related `Type` mapping via a const generic argument,
/// then map from that to an unrelated type via a trait with associated types.
///
/// [`Const`] is the "related type" in the above explaination, [`SmallestLenType`] is the mapping trait.
#[allow(rustdoc::private_intra_doc_links)] // Only publically exposed via `crate::_export`
pub type DefaultLenType<const N: usize> = <Const<N> as SmallestLenType>::Type;
impl_lentodefault!(ZeroLenType: 0);
impl_lentodefault!(u8: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 189, 190, 191, 192, 193, 194, 195, 196, 197, 198, 199, 200, 201, 202, 203, 204, 205, 206, 207, 208, 209, 210, 211, 212, 213, 214, 215, 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, 228, 229, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239, 240, 241, 242, 243, 244, 245, 246, 247, 248, 249, 250, 251, 252, 253, 254, 255);
impl_lentodefault!(u16: 256, 300, 400, 500, 512, 600, 700, 800, 900, 1000, 1024, 2000, 2048, 4000, 4096, 8000, 8192, 16000, 16384, 32000, 32768, 65000, 65535);
#[cfg(any(target_pointer_width = "32", target_pointer_width = "64"))]
impl_lentodefault!(u32: 65536, 131072, 262144, 524288, 1048576, 2097152, 4194304, 8388608, 16777216, 33554432, 67108864, 134217728, 268435456, 536870912, 1073741824, 2147483648);
pub const fn check_capacity_fits<LenT: LenType, const N: usize>() {
assert!(LenT::MAX_USIZE >= N, "The capacity is larger than `LenT` can hold, increase the size of `LenT` or reduce the capacity");
}
/// Container with 0 capacity always has length 0, so there is no need to track length of such containers at all.
///
/// This type is used as a placeholder for length of container with 0 capacity. It allows optimizing total size of
/// containers like this to 0 bytes.
///
/// Logically, this type always stores value 0. Because of this ZeroLenType::one() panics and should never be called.
#[doc(hidden)]
#[derive(Copy, Clone, PartialEq, PartialOrd)]
pub struct ZeroLenType;
impl Debug for ZeroLenType {
fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
write!(f, "0")
}
}
impl Display for ZeroLenType {
fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
write!(f, "0")
}
}
impl Sealed for ZeroLenType {
const ZERO: Self = Self;
const MAX: Self = Self;
const MAX_USIZE: usize = 0;
#[inline]
fn one() -> Self {
panic!("ZeroLenType cannot represent value 1");
}
}
impl LenType for ZeroLenType {}
impl Add for ZeroLenType {
type Output = Self;
fn add(self, _rhs: Self) -> Self::Output {
Self::ZERO
}
}
impl AddAssign for ZeroLenType {
fn add_assign(&mut self, _rhs: Self) {}
}
impl Sub for ZeroLenType {
type Output = Self;
fn sub(self, _rhs: Self) -> Self::Output {
Self::ZERO
}
}
impl SubAssign for ZeroLenType {
fn sub_assign(&mut self, _rhs: Self) {}
}
#[doc(hidden)]
#[derive(Debug, PartialEq)]
pub struct ZeroLenTypeTryFromError;
impl TryFrom<usize> for ZeroLenType {
type Error = ZeroLenTypeTryFromError;
fn try_from(value: usize) -> Result<Self, Self::Error> {
if value > 0 {
return Err(ZeroLenTypeTryFromError);
}
Ok(Self::ZERO)
}
}
impl TryInto<usize> for ZeroLenType {
type Error = ();
fn try_into(self) -> Result<usize, Self::Error> {
Ok(0)
}
}
#[cfg(test)]
mod tests {
use crate::len_type::{Sealed, ZeroLenType, ZeroLenTypeTryFromError};
#[test]
pub fn test_zero_len_type_conversions() {
assert_eq!(ZeroLenType::into_usize(ZeroLenType::ZERO), 0_usize);
assert_eq!(ZeroLenType::from_usize(0_usize), ZeroLenType::ZERO);
assert_eq!(ZeroLenType::ZERO.try_into(), Ok(0_usize));
assert_eq!(ZeroLenType::try_from(0_usize), Ok(ZeroLenType::ZERO));
assert_eq!(ZeroLenType::try_from(1_usize), Err(ZeroLenTypeTryFromError));
}
#[test]
#[should_panic]
pub fn test_zero_len_type_one() {
ZeroLenType::one();
}
#[test]
#[should_panic]
pub fn test_zero_len_type_one_usize() {
ZeroLenType::from_usize(1);
}
#[test]
pub fn test_zero_len_type_constants() {
assert_eq!(ZeroLenType::ZERO, ZeroLenType);
assert_eq!(ZeroLenType::MAX, ZeroLenType);
assert_eq!(ZeroLenType::MAX_USIZE, 0_usize);
}
#[test]
pub fn test_zero_len_type_size() {
assert_eq!(core::mem::size_of::<ZeroLenType>(), 0);
}
#[test]
pub fn test_zero_len_type_ops() {
assert_eq!(ZeroLenType::ZERO + ZeroLenType::ZERO, ZeroLenType::ZERO);
assert_eq!(ZeroLenType::ZERO - ZeroLenType::ZERO, ZeroLenType::ZERO);
let mut zero = ZeroLenType::ZERO;
zero += ZeroLenType::ZERO;
assert_eq!(zero, ZeroLenType::ZERO);
zero -= ZeroLenType::ZERO;
assert_eq!(zero, ZeroLenType::ZERO);
}
#[test]
pub fn test_zero_len_type_debug() {
assert_eq!(format!("{}", ZeroLenType), "0");
assert_eq!(format!("{:?}", ZeroLenType), "0");
}
}

1
src/lib.rs
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@ -241,7 +241,6 @@ mod ufmt;
/// Do not use. Used for macros only. Not covered by semver guarantees.
#[doc(hidden)]
pub mod _export {
pub use crate::len_type::DefaultLenType;
pub use crate::string::format;
}

42
src/sorted_linked_list.rs
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@ -8,7 +8,7 @@
//!
//! ```
//! use heapless::sorted_linked_list::{Max, SortedLinkedList};
//! let mut ll: SortedLinkedList<_, Max, 3> = SortedLinkedList::new_u8();
//! let mut ll: SortedLinkedList<_, Max, 3, u8> = SortedLinkedList::new_u8();
//!
//! // The largest value will always be first
//! ll.push(1).unwrap();
@ -156,7 +156,7 @@ pub use storage::{
OwnedSortedLinkedListStorage, SortedLinkedListStorage, ViewSortedLinkedListStorage,
};
use crate::len_type::{DefaultLenType, LenType};
use crate::len_type::LenType;
/// Marker for Min sorted [`SortedLinkedList`].
pub struct Min;
@ -212,7 +212,7 @@ where
}
/// The linked list.
pub type SortedLinkedList<T, K, const N: usize, Idx = DefaultLenType<N>> =
pub type SortedLinkedList<T, K, const N: usize, Idx = usize> =
SortedLinkedListInner<T, Idx, K, OwnedSortedLinkedListStorage<T, Idx, N>>;
/// The linked list.
@ -391,7 +391,7 @@ where
///
/// ```
/// use heapless::sorted_linked_list::{Max, SortedLinkedList};
/// let mut ll: SortedLinkedList<_, Max, 3> = SortedLinkedList::new_u8();
/// let mut ll: SortedLinkedList<_, Max, 3, u8> = SortedLinkedList::new_u8();
///
/// // The largest value will always be first
/// ll.push(1).unwrap();
@ -421,7 +421,7 @@ where
///
/// ```
/// use heapless::sorted_linked_list::{Max, Min, SortedLinkedList};
/// let mut ll_max: SortedLinkedList<_, Max, 3> = SortedLinkedList::new_u8();
/// let mut ll_max: SortedLinkedList<_, Max, 3, u8> = SortedLinkedList::new_u8();
///
/// // The largest value will always be first
/// ll_max.push(1).unwrap();
@ -431,7 +431,7 @@ where
/// ll_max.push(3).unwrap();
/// assert_eq!(ll_max.peek(), Some(&3));
///
/// let mut ll_min: SortedLinkedList<_, Min, 3> = SortedLinkedList::new_u8();
/// let mut ll_min: SortedLinkedList<_, Min, 3, u8> = SortedLinkedList::new_u8();
///
/// // The Smallest value will always be first
/// ll_min.push(3).unwrap();
@ -470,7 +470,7 @@ where
///
/// ```
/// use heapless::sorted_linked_list::{Max, SortedLinkedList};
/// let mut ll: SortedLinkedList<_, Max, 3> = SortedLinkedList::new_u8();
/// let mut ll: SortedLinkedList<_, Max, 3, u8> = SortedLinkedList::new_u8();
///
/// ll.push(1).unwrap();
/// ll.push(2).unwrap();
@ -493,7 +493,7 @@ where
///
/// ```
/// use heapless::sorted_linked_list::{Max, SortedLinkedList};
/// let mut ll: SortedLinkedList<_, Max, 3> = SortedLinkedList::new_u8();
/// let mut ll: SortedLinkedList<_, Max, 3, u8> = SortedLinkedList::new_u8();
///
/// assert_eq!(ll.is_full(), false);
///
@ -515,7 +515,7 @@ where
///
/// ```
/// use heapless::sorted_linked_list::{Max, SortedLinkedList};
/// let mut ll: SortedLinkedList<_, Max, 3> = SortedLinkedList::new_u8();
/// let mut ll: SortedLinkedList<_, Max, 3, u8> = SortedLinkedList::new_u8();
///
/// assert_eq!(ll.is_empty(), true);
///
@ -541,7 +541,7 @@ where
///
/// ```
/// use heapless::sorted_linked_list::{Max, SortedLinkedList};
/// let mut ll: SortedLinkedList<_, Max, 3> = SortedLinkedList::new_u8();
/// let mut ll: SortedLinkedList<_, Max, 3, u8> = SortedLinkedList::new_u8();
///
/// ll.push(1).unwrap();
/// ll.push(2).unwrap();
@ -565,7 +565,7 @@ where
///
/// ```
/// use heapless::sorted_linked_list::{Max, SortedLinkedList};
/// let mut ll: SortedLinkedList<_, Max, 3> = SortedLinkedList::new_u8();
/// let mut ll: SortedLinkedList<_, Max, 3, u8> = SortedLinkedList::new_u8();
///
/// ll.push(1).unwrap();
/// ll.push(2).unwrap();
@ -695,7 +695,7 @@ where
///
/// ```
/// use heapless::sorted_linked_list::{Max, SortedLinkedList};
/// let mut ll: SortedLinkedList<_, Max, 3> = SortedLinkedList::new_u8();
/// let mut ll: SortedLinkedList<_, Max, 3, u8> = SortedLinkedList::new_u8();
///
/// ll.push(1).unwrap();
/// ll.push(2).unwrap();
@ -725,7 +725,7 @@ where
///
/// ```
/// use heapless::sorted_linked_list::{Max, SortedLinkedList};
/// let mut ll: SortedLinkedList<_, Max, 3> = SortedLinkedList::new_u8();
/// let mut ll: SortedLinkedList<_, Max, 3, u8> = SortedLinkedList::new_u8();
///
/// ll.push(1).unwrap();
/// ll.push(2).unwrap();
@ -863,7 +863,7 @@ mod tests {
#[test]
fn test_peek() {
let mut ll: SortedLinkedList<u32, Max, 3> = SortedLinkedList::new_u8();
let mut ll: SortedLinkedList<u32, Max, 3, u8> = SortedLinkedList::new_u8();
ll.push(1).unwrap();
assert_eq!(ll.peek().unwrap(), &1);
@ -874,7 +874,7 @@ mod tests {
ll.push(3).unwrap();
assert_eq!(ll.peek().unwrap(), &3);
let mut ll: SortedLinkedList<u32, Min, 3> = SortedLinkedList::new_u8();
let mut ll: SortedLinkedList<u32, Min, 3, u8> = SortedLinkedList::new_u8();
ll.push(2).unwrap();
assert_eq!(ll.peek().unwrap(), &2);
@ -888,7 +888,7 @@ mod tests {
#[test]
fn test_full() {
let mut ll: SortedLinkedList<u32, Max, 3> = SortedLinkedList::new_u8();
let mut ll: SortedLinkedList<u32, Max, 3, u8> = SortedLinkedList::new_u8();
ll.push(1).unwrap();
ll.push(2).unwrap();
ll.push(3).unwrap();
@ -898,7 +898,7 @@ mod tests {
#[test]
fn test_empty() {
let ll: SortedLinkedList<u32, Max, 3> = SortedLinkedList::new_u8();
let ll: SortedLinkedList<u32, Max, 3, u8> = SortedLinkedList::new_u8();
assert!(ll.is_empty());
}
@ -913,7 +913,7 @@ mod tests {
#[test]
fn test_rejected_push() {
let mut ll: SortedLinkedList<u32, Max, 3> = SortedLinkedList::new_u8();
let mut ll: SortedLinkedList<u32, Max, 3, u8> = SortedLinkedList::new_u8();
ll.push(1).unwrap();
ll.push(2).unwrap();
ll.push(3).unwrap();
@ -926,7 +926,7 @@ mod tests {
#[test]
fn test_updating() {
let mut ll: SortedLinkedList<u32, Max, 3> = SortedLinkedList::new_u8();
let mut ll: SortedLinkedList<u32, Max, 3, u8> = SortedLinkedList::new_u8();
ll.push(1).unwrap();
ll.push(2).unwrap();
ll.push(3).unwrap();
@ -953,7 +953,7 @@ mod tests {
#[test]
fn test_updating_1() {
let mut ll: SortedLinkedList<u32, Max, 3> = SortedLinkedList::new_u8();
let mut ll: SortedLinkedList<u32, Max, 3, u8> = SortedLinkedList::new_u8();
ll.push(1).unwrap();
let v = ll.pop().unwrap();
@ -963,7 +963,7 @@ mod tests {
#[test]
fn test_updating_2() {
let mut ll: SortedLinkedList<u32, Max, 3> = SortedLinkedList::new_u8();
let mut ll: SortedLinkedList<u32, Max, 3, u8> = SortedLinkedList::new_u8();
ll.push(1).unwrap();
let mut find = ll.find_mut(|v| *v == 1).unwrap();

45
src/string/mod.rs
View File

@ -11,7 +11,7 @@ use core::{
str::{self, Utf8Error},
};
use crate::{len_type::DefaultLenType, CapacityError};
use crate::CapacityError;
use crate::{
len_type::LenType,
vec::{OwnedVecStorage, Vec, VecInner, ViewVecStorage},
@ -147,10 +147,10 @@ pub struct StringInner<LenT: LenType, S: StringStorage + ?Sized> {
}
/// A fixed capacity [`String`](https://doc.rust-lang.org/std/string/struct.String.html).
pub type String<const N: usize, LenT = DefaultLenType<N>> = StringInner<LenT, OwnedStorage<N>>;
pub type String<const N: usize, LenT = usize> = StringInner<LenT, OwnedStorage<N>>;
/// A dynamic capacity [`String`](https://doc.rust-lang.org/std/string/struct.String.html).
pub type StringView<LenT> = StringInner<LenT, ViewStorage>;
pub type StringView<LenT = usize> = StringInner<LenT, ViewStorage>;
impl<LenT: LenType, const N: usize> String<N, LenT> {
/// Constructs a new, empty `String` with a fixed capacity of `N` bytes.
@ -368,7 +368,7 @@ impl<LenT: LenType, S: StringStorage + ?Sized> StringInner<LenT, S> {
/// ```rust
/// # use heapless::string::{String, StringView};
/// let s: String<10, _> = String::try_from("hello").unwrap();
/// let view: &StringView<u8> = s.as_view();
/// let view: &StringView = s.as_view();
/// ```
///
/// It is often preferable to do the same through type coerction, since `String<N>` implements `Unsize<StringView>`:
@ -376,7 +376,7 @@ impl<LenT: LenType, S: StringStorage + ?Sized> StringInner<LenT, S> {
/// ```rust
/// # use heapless::string::{String, StringView};
/// let s: String<10, _> = String::try_from("hello").unwrap();
/// let view: &StringView<u8> = &s;
/// let view: &StringView = &s;
/// ```
#[inline]
pub fn as_view(&self) -> &StringView<LenT> {
@ -389,7 +389,7 @@ impl<LenT: LenType, S: StringStorage + ?Sized> StringInner<LenT, S> {
/// ```rust
/// # use heapless::string::{String, StringView};
/// let mut s: String<10> = String::try_from("hello").unwrap();
/// let view: &mut StringView<_> = s.as_mut_view();
/// let view: &mut StringView = s.as_mut_view();
/// ```
///
/// It is often preferable to do the same through type coerction, since `String<N>` implements `Unsize<StringView>`:
@ -397,7 +397,7 @@ impl<LenT: LenType, S: StringStorage + ?Sized> StringInner<LenT, S> {
/// ```rust
/// # use heapless::string::{String, StringView};
/// let mut s: String<10> = String::try_from("hello").unwrap();
/// let view: &mut StringView<_> = &mut s;
/// let view: &mut StringView = &mut s;
/// ```
#[inline]
pub fn as_mut_view(&mut self) -> &mut StringView<LenT> {
@ -938,8 +938,12 @@ pub fn format<const N: usize, LenT: LenType>(
macro_rules! format {
// Without semicolon as separator to disambiguate between arms, Rust just
// chooses the first so that the format string would land in $max.
($max:expr; $lenT:path; $($arg:tt)*) => {{
let res = $crate::_export::format::<$max, $lenT>(core::format_args!($($arg)*));
res
}};
($max:expr; $($arg:tt)*) => {{
let res = $crate::_export::format::<$max, $crate::_export::DefaultLenType<$max>>(core::format_args!($($arg)*));
let res = $crate::_export::format::<$max, usize>(core::format_args!($($arg)*));
res
}};
($($arg:tt)*) => {{
@ -1236,29 +1240,4 @@ mod tests {
let formatted = format!(2; "123");
assert_eq!(formatted, Err(core::fmt::Error));
}
#[test]
fn zero_capacity() {
let mut s: String<0> = String::new();
// Validate capacity
assert_eq!(s.capacity(), 0);
// Make sure there is no capacity
assert!(s.push('a').is_err());
// Validate length
assert_eq!(s.len(), 0);
// Validate pop
assert_eq!(s.pop(), None);
// Validate slice
assert_eq!(s.as_str(), "");
// Validate empty
assert!(s.is_empty());
// Size of string with zero capacity should be 0 bytes because of `ZeroLenType` optimization
assert_eq!(core::mem::size_of_val(&s), 0);
}
}

37
src/vec/mod.rs
View File

@ -11,7 +11,7 @@ use core::{
slice,
};
use crate::len_type::{check_capacity_fits, DefaultLenType, LenType};
use crate::len_type::{check_capacity_fits, LenType};
use crate::CapacityError;
mod drain;
@ -255,8 +255,7 @@ pub struct VecInner<T, LenT: LenType, S: VecStorage<T> + ?Sized> {
/// For uncommmon capacity values, or in generic scenarios, you may have to provide the `LenT` generic yourself.
///
/// This should be the smallest unsigned integer type that your capacity fits in, or `usize` if you don't want to consider this.
pub type Vec<T, const N: usize, LenT = DefaultLenType<N>> =
VecInner<T, LenT, OwnedVecStorage<T, N>>;
pub type Vec<T, const N: usize, LenT = usize> = VecInner<T, LenT, OwnedVecStorage<T, N>>;
/// A [`Vec`] with dynamic capacity
///
@ -1806,7 +1805,7 @@ mod tests {
{
let v: Vec<Droppable, 2> = Vec::new();
let v: Box<Vec<Droppable, 2>> = Box::new(v);
let mut v: Box<VecView<Droppable, u8>> = v;
let mut v: Box<VecView<Droppable>> = v;
v.push(Droppable::new()).ok().unwrap();
v.push(Droppable::new()).ok().unwrap();
assert_eq!(Droppable::count(), 2);
@ -1819,7 +1818,7 @@ mod tests {
{
let v: Vec<Droppable, 2> = Vec::new();
let v: Box<Vec<Droppable, 2>> = Box::new(v);
let mut v: Box<VecView<Droppable, u8>> = v;
let mut v: Box<VecView<Droppable>> = v;
v.push(Droppable::new()).ok().unwrap();
v.push(Droppable::new()).ok().unwrap();
assert_eq!(Droppable::count(), 2);
@ -2181,34 +2180,6 @@ mod tests {
assert!(!v.ends_with(b"a"));
}
#[test]
fn zero_capacity() {
let mut v: Vec<u8, 0> = Vec::new();
// Validate capacity
assert_eq!(v.capacity(), 0);
// Make sure there is no capacity
assert!(v.push(1).is_err());
// Validate length
assert_eq!(v.len(), 0);
// Validate pop
assert_eq!(v.pop(), None);
// Validate slice
assert_eq!(v.as_slice(), &[]);
// Validate empty
assert!(v.is_empty());
// Validate full
assert!(v.is_full());
// Size of vector with zero capacity should be 0 bytes because of `ZeroLenType` optimization
assert_eq!(core::mem::size_of_val(&v), 0);
}
#[test]
fn spare_capacity_mut() {
let mut v: Vec<_, 4> = Vec::new();