Make Hash, Hasher and BuildHasher #[const_trait] and make Sip const Hasher

library/core/src/hash/mod.rs

@@ -86,7 +86,7 @@
 #![stable(feature = "rust1", since = "1.0.0")]
 
 use crate::fmt;
-use crate::marker;
+use crate::marker::{self, Destruct};
 
 #[stable(feature = "rust1", since = "1.0.0")]
 #[allow(deprecated)]
@@ -183,6 +183,7 @@ mod sip;
 /// [impl]: ../../std/primitive.str.html#impl-Hash-for-str
 #[stable(feature = "rust1", since = "1.0.0")]
 #[rustc_diagnostic_item = "Hash"]
+#[const_trait]
 pub trait Hash {
     /// Feeds this value into the given [`Hasher`].
     ///
@@ -234,12 +235,19 @@ pub trait Hash {
     /// [`hash`]: Hash::hash
     /// [`hash_slice`]: Hash::hash_slice
     #[stable(feature = "hash_slice", since = "1.3.0")]
-    fn hash_slice<H: Hasher>(data: &[Self], state: &mut H)
+    fn hash_slice<H: ~const Hasher>(data: &[Self], state: &mut H)
     where
         Self: Sized,
     {
-        for piece in data {
-            piece.hash(state);
+        //FIXME(const_iter_slice): Revert to for loop
+        //for piece in data {
+        //    piece.hash(state);
+        //}
+
+        let mut i = 0;
+        while i < data.len() {
+            data[i].hash(state);
+            i += 1;
         }
     }
 }
@@ -313,6 +321,7 @@ pub use macros::Hash;
 /// [`write_u8`]: Hasher::write_u8
 /// [`write_u32`]: Hasher::write_u32
 #[stable(feature = "rust1", since = "1.0.0")]
+#[const_trait]
 pub trait Hasher {
     /// Returns the hash value for the values written so far.
     ///
@@ -558,7 +567,8 @@ pub trait Hasher {
 }
 
 #[stable(feature = "indirect_hasher_impl", since = "1.22.0")]
-impl<H: Hasher + ?Sized> Hasher for &mut H {
+#[rustc_const_unstable(feature = "const_hash", issue = "104061")]
+impl<H: ~const Hasher + ?Sized> const Hasher for &mut H {
     fn finish(&self) -> u64 {
         (**self).finish()
     }
@@ -638,6 +648,7 @@ impl<H: Hasher + ?Sized> Hasher for &mut H {
 /// [`build_hasher`]: BuildHasher::build_hasher
 /// [`HashMap`]: ../../std/collections/struct.HashMap.html
 #[stable(since = "1.7.0", feature = "build_hasher")]
+#[const_trait]
 pub trait BuildHasher {
     /// Type of the hasher that will be created.
     #[stable(since = "1.7.0", feature = "build_hasher")]
@@ -698,9 +709,10 @@ pub trait BuildHasher {
     /// );
     /// ```
     #[unstable(feature = "build_hasher_simple_hash_one", issue = "86161")]
-    fn hash_one<T: Hash>(&self, x: T) -> u64
+    fn hash_one<T: ~const Hash + ~const Destruct>(&self, x: T) -> u64
     where
         Self: Sized,
+        Self::Hasher: ~const Hasher + ~const Destruct,
     {
         let mut hasher = self.build_hasher();
         x.hash(&mut hasher);
@@ -764,7 +776,8 @@ impl<H> fmt::Debug for BuildHasherDefault<H> {
 }
 
 #[stable(since = "1.7.0", feature = "build_hasher")]
-impl<H: Default + Hasher> BuildHasher for BuildHasherDefault<H> {
+#[rustc_const_unstable(feature = "const_hash", issue = "104061")]
+impl<H: ~const Default + Hasher> const BuildHasher for BuildHasherDefault<H> {
     type Hasher = H;
 
     fn build_hasher(&self) -> H {
@@ -806,14 +819,15 @@ mod impls {
     macro_rules! impl_write {
         ($(($ty:ident, $meth:ident),)*) => {$(
             #[stable(feature = "rust1", since = "1.0.0")]
-            impl Hash for $ty {
+            #[rustc_const_unstable(feature = "const_hash", issue = "104061")]
+            impl const Hash for $ty {
                 #[inline]
-                fn hash<H: Hasher>(&self, state: &mut H) {
+                fn hash<H: ~const Hasher>(&self, state: &mut H) {
                     state.$meth(*self)
                 }
 
                 #[inline]
-                fn hash_slice<H: Hasher>(data: &[$ty], state: &mut H) {
+                fn hash_slice<H: ~const Hasher>(data: &[$ty], state: &mut H) {
                     let newlen = data.len() * mem::size_of::<$ty>();
                     let ptr = data.as_ptr() as *const u8;
                     // SAFETY: `ptr` is valid and aligned, as this macro is only used
@@ -842,54 +856,60 @@ mod impls {
     }
 
     #[stable(feature = "rust1", since = "1.0.0")]
-    impl Hash for bool {
+    #[rustc_const_unstable(feature = "const_hash", issue = "104061")]
+    impl const Hash for bool {
         #[inline]
-        fn hash<H: Hasher>(&self, state: &mut H) {
+        fn hash<H: ~const Hasher>(&self, state: &mut H) {
             state.write_u8(*self as u8)
         }
     }
 
     #[stable(feature = "rust1", since = "1.0.0")]
-    impl Hash for char {
+    #[rustc_const_unstable(feature = "const_hash", issue = "104061")]
+    impl const Hash for char {
         #[inline]
-        fn hash<H: Hasher>(&self, state: &mut H) {
+        fn hash<H: ~const Hasher>(&self, state: &mut H) {
             state.write_u32(*self as u32)
         }
     }
 
     #[stable(feature = "rust1", since = "1.0.0")]
-    impl Hash for str {
+    #[rustc_const_unstable(feature = "const_hash", issue = "104061")]
+    impl const Hash for str {
         #[inline]
-        fn hash<H: Hasher>(&self, state: &mut H) {
+        fn hash<H: ~const Hasher>(&self, state: &mut H) {
             state.write_str(self);
         }
     }
 
     #[stable(feature = "never_hash", since = "1.29.0")]
-    impl Hash for ! {
+    #[rustc_const_unstable(feature = "const_hash", issue = "104061")]
+    impl const Hash for ! {
         #[inline]
-        fn hash<H: Hasher>(&self, _: &mut H) {
+        fn hash<H: ~const Hasher>(&self, _: &mut H) {
             *self
         }
     }
 
     macro_rules! impl_hash_tuple {
         () => (
             #[stable(feature = "rust1", since = "1.0.0")]
-            impl Hash for () {
+            #[rustc_const_unstable(feature = "const_hash", issue = "104061")]
+            impl const Hash for () {
                 #[inline]
-                fn hash<H: Hasher>(&self, _state: &mut H) {}
+                fn hash<H: ~const Hasher>(&self, _state: &mut H) {}
             }
         );
 
         ( $($name:ident)+) => (
             maybe_tuple_doc! {
                 $($name)+ @
                 #[stable(feature = "rust1", since = "1.0.0")]
-                impl<$($name: Hash),+> Hash for ($($name,)+) where last_type!($($name,)+): ?Sized {
+                #[rustc_const_unstable(feature = "const_hash", issue = "104061")]
+                impl<$($name: ~const Hash),+> const Hash for ($($name,)+) where last_type!($($name,)+): ?Sized {
                     #[allow(non_snake_case)]
                     #[inline]
-                    fn hash<S: Hasher>(&self, state: &mut S) {
+                    fn hash<S: ~const Hasher>(&self, state: &mut S) {
                         let ($(ref $name,)+) = *self;
                         $($name.hash(state);)+
                     }
@@ -932,24 +952,27 @@ mod impls {
     impl_hash_tuple! { T B C D E F G H I J K L }
 
     #[stable(feature = "rust1", since = "1.0.0")]
-    impl<T: Hash> Hash for [T] {
+    #[rustc_const_unstable(feature = "const_hash", issue = "104061")]
+    impl<T: ~const Hash> const Hash for [T] {
         #[inline]
-        fn hash<H: Hasher>(&self, state: &mut H) {
+        fn hash<H: ~const Hasher>(&self, state: &mut H) {
             state.write_length_prefix(self.len());
             Hash::hash_slice(self, state)
         }
     }
 
     #[stable(feature = "rust1", since = "1.0.0")]
-    impl<T: ?Sized + Hash> Hash for &T {
+    #[rustc_const_unstable(feature = "const_hash", issue = "104061")]
+    impl<T: ?Sized + ~const Hash> const Hash for &T {
         #[inline]
-        fn hash<H: Hasher>(&self, state: &mut H) {
+        fn hash<H: ~const Hasher>(&self, state: &mut H) {
             (**self).hash(state);
         }
     }
 
     #[stable(feature = "rust1", since = "1.0.0")]
-    impl<T: ?Sized + Hash> Hash for &mut T {
+    #[rustc_const_unstable(feature = "const_hash", issue = "104061")]
+    impl<T: ?Sized + ~const Hash> const Hash for &mut T {
         #[inline]
         fn hash<H: Hasher>(&self, state: &mut H) {
             (**self).hash(state);

library/core/src/hash/sip.rs

@@ -118,7 +118,7 @@ macro_rules! load_int_le {
 /// Safety: this performs unchecked indexing of `buf` at `start..start+len`, so
 /// that must be in-bounds.
 #[inline]
-unsafe fn u8to64_le(buf: &[u8], start: usize, len: usize) -> u64 {
+const unsafe fn u8to64_le(buf: &[u8], start: usize, len: usize) -> u64 {
     debug_assert!(len < 8);
     let mut i = 0; // current byte index (from LSB) in the output u64
     let mut out = 0;
@@ -138,7 +138,7 @@ unsafe fn u8to64_le(buf: &[u8], start: usize, len: usize) -> u64 {
         out |= (unsafe { *buf.get_unchecked(start + i) } as u64) << (i * 8);
         i += 1;
     }
-    debug_assert_eq!(i, len);
+    debug_assert!(i == len);
     out
 }
 
@@ -150,8 +150,9 @@ impl SipHasher {
         since = "1.13.0",
         note = "use `std::collections::hash_map::DefaultHasher` instead"
     )]
+    #[rustc_const_unstable(feature = "const_hash", issue = "104061")]
     #[must_use]
-    pub fn new() -> SipHasher {
+    pub const fn new() -> SipHasher {
         SipHasher::new_with_keys(0, 0)
     }
 
@@ -162,8 +163,9 @@ impl SipHasher {
         since = "1.13.0",
         note = "use `std::collections::hash_map::DefaultHasher` instead"
     )]
+    #[rustc_const_unstable(feature = "const_hash", issue = "104061")]
     #[must_use]
-    pub fn new_with_keys(key0: u64, key1: u64) -> SipHasher {
+    pub const fn new_with_keys(key0: u64, key1: u64) -> SipHasher {
         SipHasher(SipHasher24 { hasher: Hasher::new_with_keys(key0, key1) })
     }
 }
@@ -176,7 +178,8 @@ impl SipHasher13 {
         since = "1.13.0",
         note = "use `std::collections::hash_map::DefaultHasher` instead"
     )]
-    pub fn new() -> SipHasher13 {
+    #[rustc_const_unstable(feature = "const_hash", issue = "104061")]
+    pub const fn new() -> SipHasher13 {
         SipHasher13::new_with_keys(0, 0)
     }
 
@@ -187,14 +190,15 @@ impl SipHasher13 {
         since = "1.13.0",
         note = "use `std::collections::hash_map::DefaultHasher` instead"
     )]
-    pub fn new_with_keys(key0: u64, key1: u64) -> SipHasher13 {
+    #[rustc_const_unstable(feature = "const_hash", issue = "104061")]
+    pub const fn new_with_keys(key0: u64, key1: u64) -> SipHasher13 {
         SipHasher13 { hasher: Hasher::new_with_keys(key0, key1) }
     }
 }
 
 impl<S: Sip> Hasher<S> {
     #[inline]
-    fn new_with_keys(key0: u64, key1: u64) -> Hasher<S> {
+    const fn new_with_keys(key0: u64, key1: u64) -> Hasher<S> {
         let mut state = Hasher {
             k0: key0,
             k1: key1,
@@ -209,7 +213,7 @@ impl<S: Sip> Hasher<S> {
     }
 
     #[inline]
-    fn reset(&mut self) {
+    const fn reset(&mut self) {
         self.length = 0;
         self.state.v0 = self.k0 ^ 0x736f6d6570736575;
         self.state.v1 = self.k1 ^ 0x646f72616e646f6d;
@@ -220,7 +224,8 @@ impl<S: Sip> Hasher<S> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl super::Hasher for SipHasher {
+#[rustc_const_unstable(feature = "const_hash", issue = "104061")]
+impl const super::Hasher for SipHasher {
     #[inline]
     fn write(&mut self, msg: &[u8]) {
         self.0.hasher.write(msg)
@@ -238,7 +243,8 @@ impl super::Hasher for SipHasher {
 }
 
 #[unstable(feature = "hashmap_internals", issue = "none")]
-impl super::Hasher for SipHasher13 {
+#[rustc_const_unstable(feature = "const_hash", issue = "104061")]
+impl const super::Hasher for SipHasher13 {
     #[inline]
     fn write(&mut self, msg: &[u8]) {
         self.hasher.write(msg)
@@ -255,7 +261,7 @@ impl super::Hasher for SipHasher13 {
     }
 }
 
-impl<S: Sip> super::Hasher for Hasher<S> {
+impl<S: ~const Sip> const super::Hasher for Hasher<S> {
     // Note: no integer hashing methods (`write_u*`, `write_i*`) are defined
     // for this type. We could add them, copy the `short_write` implementation
     // in librustc_data_structures/sip128.rs, and add `write_u*`/`write_i*`
@@ -335,7 +341,7 @@ impl<S: Sip> super::Hasher for Hasher<S> {
     }
 }
 
-impl<S: Sip> Clone for Hasher<S> {
+impl<S: Sip> const Clone for Hasher<S> {
     #[inline]
     fn clone(&self) -> Hasher<S> {
         Hasher {
@@ -359,6 +365,7 @@ impl<S: Sip> Default for Hasher<S> {
 }
 
 #[doc(hidden)]
+#[const_trait]
 trait Sip {
     fn c_rounds(_: &mut State);
     fn d_rounds(_: &mut State);
@@ -367,7 +374,7 @@ trait Sip {
 #[derive(Debug, Clone, Default)]
 struct Sip13Rounds;
 
-impl Sip for Sip13Rounds {
+impl const Sip for Sip13Rounds {
     #[inline]
     fn c_rounds(state: &mut State) {
         compress!(state);
@@ -384,7 +391,7 @@ impl Sip for Sip13Rounds {
 #[derive(Debug, Clone, Default)]
 struct Sip24Rounds;
 
-impl Sip for Sip24Rounds {
+impl const Sip for Sip24Rounds {
     #[inline]
     fn c_rounds(state: &mut State) {
         compress!(state);

library/core/src/lib.rs

@@ -112,6 +112,7 @@
 #![feature(const_float_bits_conv)]
 #![feature(const_float_classify)]
 #![feature(const_fmt_arguments_new)]
+#![feature(const_hash)]
 #![feature(const_heap)]
 #![feature(const_convert)]
 #![feature(const_index_range_slice_index)]

library/std/src/collections/hash/map.rs

@@ -3161,14 +3161,16 @@ impl DefaultHasher {
     #[stable(feature = "hashmap_default_hasher", since = "1.13.0")]
     #[inline]
     #[allow(deprecated)]
+    #[rustc_const_unstable(feature = "const_hash", issue = "104061")]
     #[must_use]
-    pub fn new() -> DefaultHasher {
+    pub const fn new() -> DefaultHasher {
         DefaultHasher(SipHasher13::new_with_keys(0, 0))
     }
 }
 
 #[stable(feature = "hashmap_default_hasher", since = "1.13.0")]
-impl Default for DefaultHasher {
+#[rustc_const_unstable(feature = "const_hash", issue = "104061")]
+impl const Default for DefaultHasher {
     /// Creates a new `DefaultHasher` using [`new`].
     /// See its documentation for more.
     ///
@@ -3180,7 +3182,8 @@ impl Default for DefaultHasher {
 }
 
 #[stable(feature = "hashmap_default_hasher", since = "1.13.0")]
-impl Hasher for DefaultHasher {
+#[rustc_const_unstable(feature = "const_hash", issue = "104061")]
+impl const Hasher for DefaultHasher {
     // The underlying `SipHasher13` doesn't override the other
     // `write_*` methods, so it's ok not to forward them here.
 

library/std/src/lib.rs

@@ -314,6 +314,7 @@
 #![feature(maybe_uninit_uninit_array)]
 #![feature(const_maybe_uninit_uninit_array)]
 #![feature(const_waker)]
+#![feature(const_hash)]
 //
 // Library features (alloc):
 #![feature(alloc_layout_extra)]