Store hashes in special types so they aren't accidentally encoded as numbers

compiler/rustc_data_structures/src/fingerprint.rs

@@ -1,4 +1,4 @@
-use crate::stable_hasher;
+use crate::stable_hasher::{Hash64, StableHasher, StableHasherResult};
 use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
 use std::hash::{Hash, Hasher};
 
@@ -9,32 +9,47 @@ mod tests;
 #[repr(C)]
 pub struct Fingerprint(u64, u64);
 
+pub trait FingerprintComponent {
+    fn as_u64(&self) -> u64;
+}
+
+impl FingerprintComponent for Hash64 {
+    fn as_u64(&self) -> u64 {
+        Hash64::as_u64(*self)
+    }
+}
+
+impl FingerprintComponent for u64 {
+    fn as_u64(&self) -> u64 {
+        *self
+    }
+}
+
 impl Fingerprint {
     pub const ZERO: Fingerprint = Fingerprint(0, 0);
 
     #[inline]
-    pub fn new(_0: u64, _1: u64) -> Fingerprint {
-        Fingerprint(_0, _1)
+    pub fn new<A, B>(_0: A, _1: B) -> Fingerprint
+    where
+        A: FingerprintComponent,
+        B: FingerprintComponent,
+    {
+        Fingerprint(_0.as_u64(), _1.as_u64())
     }
 
     #[inline]
-    pub fn from_smaller_hash(hash: u64) -> Fingerprint {
-        Fingerprint(hash, hash)
-    }
-
-    #[inline]
-    pub fn to_smaller_hash(&self) -> u64 {
+    pub fn to_smaller_hash(&self) -> Hash64 {
         // Even though both halves of the fingerprint are expected to be good
         // quality hash values, let's still combine the two values because the
         // Fingerprints in DefPathHash have the StableCrateId portion which is
         // the same for all DefPathHashes from the same crate. Combining the
         // two halves makes sure we get a good quality hash in such cases too.
-        self.0.wrapping_mul(3).wrapping_add(self.1)
+        Hash64::new(self.0.wrapping_mul(3).wrapping_add(self.1))
     }
 
     #[inline]
-    pub fn as_value(&self) -> (u64, u64) {
-        (self.0, self.1)
+    pub fn split(&self) -> (Hash64, Hash64) {
+        (Hash64::new(self.0), Hash64::new(self.1))
     }
 
     #[inline]
@@ -131,9 +146,9 @@ impl FingerprintHasher for crate::unhash::Unhasher {
     }
 }
 
-impl stable_hasher::StableHasherResult for Fingerprint {
+impl StableHasherResult for Fingerprint {
     #[inline]
-    fn finish(hasher: stable_hasher::StableHasher) -> Self {
+    fn finish(hasher: StableHasher) -> Self {
         let (_0, _1) = hasher.finalize();
         Fingerprint(_0, _1)
     }