Test const Hash, fix nits

library/core/src/hash/mod.rs

@@ -86,6 +86,7 @@
 #![stable(feature = "rust1", since = "1.0.0")]
 
 use crate::fmt;
+use crate::intrinsics::const_eval_select;
 use crate::marker::{self, Destruct};
 
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -239,17 +240,22 @@ pub trait Hash {
     where
         Self: Sized,
     {
-        //FIXME(const_iter_slice): Revert to for loop
+        //FIXME(const_trait_impl): revert to only a for loop
-        //for piece in data {
+        fn rt<T: Hash, H: Hasher>(data: &[T], state: &mut H) {
-        //    piece.hash(state);
+            for piece in data {
-        //}
+                piece.hash(state)
-
+            }
+        }
+        const fn ct<T: ~const Hash, H: ~const Hasher>(data: &[T], state: &mut H) {
             let mut i = 0;
             while i < data.len() {
                 data[i].hash(state);
                 i += 1;
             }
         }
+        // SAFETY: same behavior, CT just uses while instead of for
+        unsafe { const_eval_select((data, state), ct, rt) };
+    }
 }
 
 // Separate module to reexport the macro `Hash` from prelude without the trait `Hash`.

library/core/src/hash/sip.rs

@@ -138,6 +138,7 @@ const unsafe fn u8to64_le(buf: &[u8], start: usize, len: usize) -> u64 {
         out |= (unsafe { *buf.get_unchecked(start + i) } as u64) << (i * 8);
         i += 1;
     }
+    //FIXME(fee1-dead): use debug_assert_eq
     debug_assert!(i == len);
     out
 }

library/core/tests/hash/mod.rs

@@ -9,16 +9,19 @@ struct MyHasher {
     hash: u64,
 }
 
-impl Default for MyHasher {
+impl const Default for MyHasher {
     fn default() -> MyHasher {
         MyHasher { hash: 0 }
     }
 }
 
-impl Hasher for MyHasher {
+impl const Hasher for MyHasher {
     fn write(&mut self, buf: &[u8]) {
-        for byte in buf {
+        // FIXME(const_trait_impl): change to for loop
-            self.hash += *byte as u64;
+        let mut i = 0;
+        while i < buf.len() {
+            self.hash += buf[i] as u64;
+            i += 1;
         }
     }
     fn write_str(&mut self, s: &str) {
@@ -32,12 +35,25 @@ impl Hasher for MyHasher {
 
 #[test]
 fn test_writer_hasher() {
-    fn hash<T: Hash>(t: &T) -> u64 {
+    const fn hash<T: ~const Hash>(t: &T) -> u64 {
         let mut s = MyHasher { hash: 0 };
         t.hash(&mut s);
         s.finish()
     }
 
+    const {
+        // FIXME(fee1-dead): assert_eq
+        assert!(hash(&()) == 0);
+        assert!(hash(&5_u8) == 5);
+        assert!(hash(&5_u16) == 5);
+        assert!(hash(&5_u32) == 5);
+
+        assert!(hash(&'a') == 97);
+
+        let s: &str = "a";
+        assert!(hash(&s) == 97 + 0xFF);
+    };
+
     assert_eq!(hash(&()), 0);
 
     assert_eq!(hash(&5_u8), 5);
@@ -97,7 +113,7 @@ struct CustomHasher {
     output: u64,
 }
 
-impl Hasher for CustomHasher {
+impl const Hasher for CustomHasher {
     fn finish(&self) -> u64 {
         self.output
     }
@@ -109,27 +125,29 @@ impl Hasher for CustomHasher {
     }
 }
 
-impl Default for CustomHasher {
+impl const Default for CustomHasher {
     fn default() -> CustomHasher {
         CustomHasher { output: 0 }
     }
 }
 
-impl Hash for Custom {
+impl const Hash for Custom {
-    fn hash<H: Hasher>(&self, state: &mut H) {
+    fn hash<H: ~const Hasher>(&self, state: &mut H) {
         state.write_u64(self.hash);
     }
 }
 
 #[test]
 fn test_custom_state() {
-    fn hash<T: Hash>(t: &T) -> u64 {
+    const fn hash<T: ~const Hash>(t: &T) -> u64 {
         let mut c = CustomHasher { output: 0 };
         t.hash(&mut c);
         c.finish()
     }
 
     assert_eq!(hash(&Custom { hash: 5 }), 5);
+
+    const { assert!(hash(&Custom { hash: 6 }) == 6) };
 }
 
 // FIXME: Instantiated functions with i128 in the signature is not supported in Emscripten.

library/core/tests/hash/sip.rs

@@ -8,7 +8,6 @@ use core::{mem, slice};
 struct Bytes<'a>(&'a [u8]);
 
 impl<'a> Hash for Bytes<'a> {
-    #[allow(unused_must_use)]
     fn hash<H: Hasher>(&self, state: &mut H) {
         let Bytes(v) = *self;
         state.write(v);
@@ -24,6 +23,20 @@ fn hash<T: Hash>(x: &T) -> u64 {
     hash_with(SipHasher::new(), x)
 }
 
+#[test]
+const fn test_const_sip() {
+    let val1 = 0x45;
+    let val2 = 0xfeed;
+
+    const fn const_hash<T: ~const Hash>(x: &T) -> u64 {
+        let mut st = SipHasher::new();
+        x.hash(&mut st);
+        st.finish()
+    }
+
+    assert!(const_hash(&(val1)) != const_hash(&(val2)));
+}
+
 #[test]
 #[allow(unused_must_use)]
 fn test_siphash_1_3() {

library/core/tests/lib.rs

@@ -11,6 +11,7 @@
 #![feature(const_caller_location)]
 #![feature(const_cell_into_inner)]
 #![feature(const_convert)]
+#![feature(const_hash)]
 #![feature(const_heap)]
 #![feature(const_maybe_uninit_as_mut_ptr)]
 #![feature(const_maybe_uninit_assume_init_read)]

library/std/src/lib.rs

@@ -314,7 +314,6 @@
 #![feature(maybe_uninit_uninit_array)]
 #![feature(const_maybe_uninit_uninit_array)]
 #![feature(const_waker)]
-#![feature(const_hash)]
 //
 // Library features (alloc):
 #![feature(alloc_layout_extra)]
@@ -353,6 +352,7 @@
 //
 // Only for const-ness:
 #![feature(const_collections_with_hasher)]
+#![feature(const_hash)]
 #![feature(const_io_structs)]
 #![feature(const_ip)]
 #![feature(const_ipv4)]