diff options
Diffstat (limited to 'compiler/rustc_data_structures/src')
| -rw-r--r-- | compiler/rustc_data_structures/src/stable_hasher.rs | 71 |
1 files changed, 54 insertions, 17 deletions
diff --git a/compiler/rustc_data_structures/src/stable_hasher.rs b/compiler/rustc_data_structures/src/stable_hasher.rs index b5bdf2e1790..a57f5067dd8 100644 --- a/compiler/rustc_data_structures/src/stable_hasher.rs +++ b/compiler/rustc_data_structures/src/stable_hasher.rs @@ -238,12 +238,21 @@ pub trait ToStableHashKey<HCX> { /// 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. -pub unsafe trait StableOrd: Ord { +pub trait StableOrd: Ord { const CAN_USE_UNSTABLE_SORT: bool; + + /// Marker to ensure that implementors have carefully considered + /// whether their `Ord` implementation obeys this trait's contract. + const THIS_IMPLEMENTATION_HAS_BEEN_TRIPLE_CHECKED: (); } -unsafe impl<T: StableOrd> StableOrd for &T { +impl<T: StableOrd> StableOrd for &T { const CAN_USE_UNSTABLE_SORT: bool = T::CAN_USE_UNSTABLE_SORT; + + // Ordering of a reference is exactly that of the referent, and since + // the ordering of the referet is stable so must be the ordering of the + // reference. + const THIS_IMPLEMENTATION_HAS_BEEN_TRIPLE_CHECKED: () = (); } /// This is a companion trait to `StableOrd`. Some types like `Symbol` can be @@ -290,8 +299,12 @@ macro_rules! impl_stable_traits_for_trivial_type { } } - unsafe impl $crate::stable_hasher::StableOrd for $t { + impl $crate::stable_hasher::StableOrd for $t { const CAN_USE_UNSTABLE_SORT: bool = true; + + // Encoding and decoding doesn't change the bytes of trivial types + // and `Ord::cmp` depends only on those bytes. + const THIS_IMPLEMENTATION_HAS_BEEN_TRIPLE_CHECKED: () = (); } }; } @@ -327,8 +340,12 @@ impl<CTX> HashStable<CTX> for Hash128 { } } -unsafe impl StableOrd for Hash128 { +impl StableOrd for Hash128 { const CAN_USE_UNSTABLE_SORT: bool = true; + + // Encoding and decoding doesn't change the bytes of `Hash128` + // and `Ord::cmp` depends only on those bytes. + const THIS_IMPLEMENTATION_HAS_BEEN_TRIPLE_CHECKED: () = (); } impl<CTX> HashStable<CTX> for ! { @@ -392,8 +409,12 @@ impl<T1: HashStable<CTX>, T2: HashStable<CTX>, CTX> HashStable<CTX> for (T1, T2) } } -unsafe impl<T1: StableOrd, T2: StableOrd> StableOrd for (T1, T2) { +impl<T1: StableOrd, T2: StableOrd> StableOrd for (T1, T2) { const CAN_USE_UNSTABLE_SORT: bool = T1::CAN_USE_UNSTABLE_SORT && T2::CAN_USE_UNSTABLE_SORT; + + // Ordering of tuples is a pure function of their elements' ordering, and since + // the ordering of each element is stable so must be the ordering of the tuple. + const THIS_IMPLEMENTATION_HAS_BEEN_TRIPLE_CHECKED: () = (); } impl<T1, T2, T3, CTX> HashStable<CTX> for (T1, T2, T3) @@ -410,9 +431,13 @@ where } } -unsafe impl<T1: StableOrd, T2: StableOrd, T3: StableOrd> StableOrd for (T1, T2, T3) { +impl<T1: StableOrd, T2: StableOrd, T3: StableOrd> StableOrd for (T1, T2, T3) { const CAN_USE_UNSTABLE_SORT: bool = T1::CAN_USE_UNSTABLE_SORT && T2::CAN_USE_UNSTABLE_SORT && T3::CAN_USE_UNSTABLE_SORT; + + // Ordering of tuples is a pure function of their elements' ordering, and since + // the ordering of each element is stable so must be the ordering of the tuple. + const THIS_IMPLEMENTATION_HAS_BEEN_TRIPLE_CHECKED: () = (); } impl<T1, T2, T3, T4, CTX> HashStable<CTX> for (T1, T2, T3, T4) @@ -431,13 +456,15 @@ where } } -unsafe impl<T1: StableOrd, T2: StableOrd, T3: StableOrd, T4: StableOrd> StableOrd - for (T1, T2, T3, T4) -{ +impl<T1: StableOrd, T2: StableOrd, T3: StableOrd, T4: StableOrd> StableOrd for (T1, T2, T3, T4) { const CAN_USE_UNSTABLE_SORT: bool = T1::CAN_USE_UNSTABLE_SORT && T2::CAN_USE_UNSTABLE_SORT && T3::CAN_USE_UNSTABLE_SORT && T4::CAN_USE_UNSTABLE_SORT; + + // Ordering of tuples is a pure function of their elements' ordering, and since + // the ordering of each element is stable so must be the ordering of the tuple. + const THIS_IMPLEMENTATION_HAS_BEEN_TRIPLE_CHECKED: () = (); } impl<T: HashStable<CTX>, CTX> HashStable<CTX> for [T] { @@ -530,8 +557,12 @@ impl<CTX> HashStable<CTX> for str { } } -unsafe impl StableOrd for &str { +impl StableOrd for &str { const CAN_USE_UNSTABLE_SORT: bool = true; + + // Encoding and decoding doesn't change the bytes of string slices + // and `Ord::cmp` depends only on those bytes. + const THIS_IMPLEMENTATION_HAS_BEEN_TRIPLE_CHECKED: () = (); } impl<CTX> HashStable<CTX> for String { @@ -541,10 +572,12 @@ impl<CTX> HashStable<CTX> for String { } } -// Safety: String comparison only depends on their contents and the -// contents are not changed by (de-)serialization. -unsafe impl StableOrd for String { +impl StableOrd for String { const CAN_USE_UNSTABLE_SORT: bool = true; + + // String comparison only depends on their contents and the + // contents are not changed by (de-)serialization. + const THIS_IMPLEMENTATION_HAS_BEEN_TRIPLE_CHECKED: () = (); } impl<HCX> ToStableHashKey<HCX> for String { @@ -570,9 +603,11 @@ impl<CTX> HashStable<CTX> for bool { } } -// Safety: sort order of bools is not changed by (de-)serialization. -unsafe impl StableOrd for bool { +impl StableOrd for bool { const CAN_USE_UNSTABLE_SORT: bool = true; + + // sort order of bools is not changed by (de-)serialization. + const THIS_IMPLEMENTATION_HAS_BEEN_TRIPLE_CHECKED: () = (); } impl<T, CTX> HashStable<CTX> for Option<T> @@ -590,9 +625,11 @@ where } } -// Safety: the Option wrapper does not add instability to comparison. -unsafe impl<T: StableOrd> StableOrd for Option<T> { +impl<T: StableOrd> StableOrd for Option<T> { const CAN_USE_UNSTABLE_SORT: bool = T::CAN_USE_UNSTABLE_SORT; + + // the Option wrapper does not add instability to comparison. + const THIS_IMPLEMENTATION_HAS_BEEN_TRIPLE_CHECKED: () = (); } impl<T1, T2, CTX> HashStable<CTX> for Result<T1, T2> |