Trait StableOrd

pub trait StableOrd: Ord {
    const CAN_USE_UNSTABLE_SORT: bool;
    const THIS_IMPLEMENTATION_HAS_BEEN_TRIPLE_CHECKED: ();
}

Trait for marking a type as having a sort order that is stable across compilation session boundaries. More formally:

Ord::cmp(a1, b1) == Ord::cmp(a2, b2)
   where a2 = decode(encode(a1, context1), context2)
         b2 = decode(encode(b1, context1), context2)

i.e. the result of Ord::cmp is not influenced by encoding the values in one session and then decoding them in another session.

This is trivially true for types where encoding and decoding don’t change the bytes of the values that are used during comparison and comparison only depends on these bytes (as opposed to some non-local state). Examples are u32, String, Path, etc.

But it is not true for:

• *const T and *mut T because the values of these pointers will change between sessions.
• DefIndex, CrateNum, LocalDefId, because their concrete values depend on state that might be different between compilation sessions.

The associated constant CAN_USE_UNSTABLE_SORT denotes whether unstable sorting can be used for this type. Set to true if and only if a == b implies a and b are fully indistinguishable.

Required Associated Constants

const CAN_USE_UNSTABLE_SORT: bool

const THIS_IMPLEMENTATION_HAS_BEEN_TRIPLE_CHECKED: ()

Marker to ensure that implementors have carefully considered whether their Ord implementation obeys this trait’s contract.

Object Safety

This trait is not object safe.

Implementations on Foreign Types

impl StableOrd for &str

const CAN_USE_UNSTABLE_SORT: bool = true

const THIS_IMPLEMENTATION_HAS_BEEN_TRIPLE_CHECKED: () = ()

impl StableOrd for bool

const CAN_USE_UNSTABLE_SORT: bool = true

const THIS_IMPLEMENTATION_HAS_BEEN_TRIPLE_CHECKED: () = ()

impl StableOrd for char

const CAN_USE_UNSTABLE_SORT: bool = true

const THIS_IMPLEMENTATION_HAS_BEEN_TRIPLE_CHECKED: () = ()

impl StableOrd for i8

const CAN_USE_UNSTABLE_SORT: bool = true

const THIS_IMPLEMENTATION_HAS_BEEN_TRIPLE_CHECKED: () = ()

impl StableOrd for i16

const CAN_USE_UNSTABLE_SORT: bool = true

const THIS_IMPLEMENTATION_HAS_BEEN_TRIPLE_CHECKED: () = ()

impl StableOrd for i32

const CAN_USE_UNSTABLE_SORT: bool = true

const THIS_IMPLEMENTATION_HAS_BEEN_TRIPLE_CHECKED: () = ()

impl StableOrd for i64

const CAN_USE_UNSTABLE_SORT: bool = true

const THIS_IMPLEMENTATION_HAS_BEEN_TRIPLE_CHECKED: () = ()

impl StableOrd for i128

const CAN_USE_UNSTABLE_SORT: bool = true

const THIS_IMPLEMENTATION_HAS_BEEN_TRIPLE_CHECKED: () = ()

impl StableOrd for isize

const CAN_USE_UNSTABLE_SORT: bool = true

const THIS_IMPLEMENTATION_HAS_BEEN_TRIPLE_CHECKED: () = ()

impl StableOrd for u8

const CAN_USE_UNSTABLE_SORT: bool = true

const THIS_IMPLEMENTATION_HAS_BEEN_TRIPLE_CHECKED: () = ()

impl StableOrd for u16

const CAN_USE_UNSTABLE_SORT: bool = true

const THIS_IMPLEMENTATION_HAS_BEEN_TRIPLE_CHECKED: () = ()

impl StableOrd for u32

const CAN_USE_UNSTABLE_SORT: bool = true

const THIS_IMPLEMENTATION_HAS_BEEN_TRIPLE_CHECKED: () = ()

impl StableOrd for u64

const CAN_USE_UNSTABLE_SORT: bool = true

const THIS_IMPLEMENTATION_HAS_BEEN_TRIPLE_CHECKED: () = ()

impl StableOrd for u128

const CAN_USE_UNSTABLE_SORT: bool = true

const THIS_IMPLEMENTATION_HAS_BEEN_TRIPLE_CHECKED: () = ()

impl StableOrd for ()

const CAN_USE_UNSTABLE_SORT: bool = true

const THIS_IMPLEMENTATION_HAS_BEEN_TRIPLE_CHECKED: () = ()

impl StableOrd for usize

const CAN_USE_UNSTABLE_SORT: bool = true

const THIS_IMPLEMENTATION_HAS_BEEN_TRIPLE_CHECKED: () = ()

impl StableOrd for String

const CAN_USE_UNSTABLE_SORT: bool = true

const THIS_IMPLEMENTATION_HAS_BEEN_TRIPLE_CHECKED: () = ()

impl StableOrd for Path

const CAN_USE_UNSTABLE_SORT: bool = true

const THIS_IMPLEMENTATION_HAS_BEEN_TRIPLE_CHECKED: () = ()

impl StableOrd for PathBuf

const CAN_USE_UNSTABLE_SORT: bool = true

const THIS_IMPLEMENTATION_HAS_BEEN_TRIPLE_CHECKED: () = ()

impl<T1: StableOrd, T2: StableOrd> StableOrd for (T1, T2)

const CAN_USE_UNSTABLE_SORT: bool = _

const THIS_IMPLEMENTATION_HAS_BEEN_TRIPLE_CHECKED: () = ()

impl<T1: StableOrd, T2: StableOrd, T3: StableOrd> StableOrd for (T1, T2, T3)

const CAN_USE_UNSTABLE_SORT: bool = _

const THIS_IMPLEMENTATION_HAS_BEEN_TRIPLE_CHECKED: () = ()

impl<T1: StableOrd, T2: StableOrd, T3: StableOrd, T4: StableOrd> StableOrd for (T1, T2, T3, T4)

const CAN_USE_UNSTABLE_SORT: bool = _

const THIS_IMPLEMENTATION_HAS_BEEN_TRIPLE_CHECKED: () = ()

impl<T: StableOrd> StableOrd for Option<T>

const CAN_USE_UNSTABLE_SORT: bool = T::CAN_USE_UNSTABLE_SORT

const THIS_IMPLEMENTATION_HAS_BEEN_TRIPLE_CHECKED: () = ()

impl<T: StableOrd> StableOrd for &T

const CAN_USE_UNSTABLE_SORT: bool = T::CAN_USE_UNSTABLE_SORT

const THIS_IMPLEMENTATION_HAS_BEEN_TRIPLE_CHECKED: () = ()

Implementors

impl StableOrd for Fingerprint

const CAN_USE_UNSTABLE_SORT: bool = true

const THIS_IMPLEMENTATION_HAS_BEEN_TRIPLE_CHECKED: () = ()

impl StableOrd for Hash64

const CAN_USE_UNSTABLE_SORT: bool = true

const THIS_IMPLEMENTATION_HAS_BEEN_TRIPLE_CHECKED: () = ()

impl StableOrd for Hash128

const CAN_USE_UNSTABLE_SORT: bool = true

const THIS_IMPLEMENTATION_HAS_BEEN_TRIPLE_CHECKED: () = ()