diff --git a/src/len_type.rs b/src/len_type.rs index 9263a5f980..282c4acc54 100644 --- a/src/len_type.rs +++ b/src/len_type.rs @@ -48,7 +48,7 @@ pub trait LenType: const ZERO: Self; /// The one value of the integer type. const ONE: Self; - /// The maxiumum value of this type, as a usize. + /// The maximum value of this type, as a `usize`. const MAX: usize; /// An infallible conversion from `usize` to `LenT`. @@ -72,28 +72,40 @@ impl_lentype!( macro_rules! impl_lentodefault { ($LenT:ty: $($len:literal),*) => {$( - impl LenToDefault for Const<$len> { - type Default = $LenT; + impl SmallestLenType for Const<$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; +/// 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", + message = "Length `N` does not have a default `LenType` mapping", note = "Provide the `LenType` explicitly, such as `usize`" )] -pub trait LenToDefault { - type Default: LenType; +pub trait SmallestLenType { + type Type: LenType; } -pub type DefaultLenType = as LenToDefault>::Default; +/// 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. +pub type DefaultLenType = as SmallestLenType>::Type; impl_lentodefault!(u8: 0, 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); 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() { - assert!(LenT::MAX >= N, "The capacity is larger than LenT can hold, increase the size of `LenT` or reduce the capacity") + assert!(LenT::MAX >= N, "The capacity is larger than `LenT` can hold, increase the size of `LenT` or reduce the capacity") } diff --git a/src/string/mod.rs b/src/string/mod.rs index 6fe05a6da9..768b2971ed 100644 --- a/src/string/mod.rs +++ b/src/string/mod.rs @@ -213,6 +213,8 @@ impl String { #[inline] pub fn from_utf8(vec: Vec) -> Result { core::str::from_utf8(&vec)?; + + // SAFETY: UTF-8 invariant has just been checked by `str::from_utf8`. Ok(unsafe { Self::from_utf8_unchecked(vec) }) } diff --git a/src/vec/mod.rs b/src/vec/mod.rs index 3a537f93c0..c90117372e 100644 --- a/src/vec/mod.rs +++ b/src/vec/mod.rs @@ -190,6 +190,8 @@ impl Vec { const { check_capacity_fits::() } let this = ManuallyDrop::new(self); + // SAFETY: Pointer argument is derived from a reference, meeting the safety documented invariants. + // This also prevents double drops by wrapping `self` in `ManuallyDrop`. Vec { len: NewLenT::from_usize(this.len()), buffer: unsafe { ptr::read(&this.buffer) },