mcf: add PasswordHash::as_password_hash_ref (#2117)

Adds an explicit method for borrowing a `&PasswordHashRef` from
`&PasswordHash`, which is useful over `AsRef`/`Borrow`/`Deref` when
avoiding inference and being explicit is preferable.

To denote the pending breaking changes, this also bumps the version to
v0.6.0-pre, so as to match `password-hash` and `phc`'s version.

Author: tarcieri

Cargo.lock

@@ -1,6 +1,6 @@
 [package]
 name = "mcf"
-version = "0.2.0"
+version = "0.6.0-pre"
 authors = ["RustCrypto Developers"]
 edition = "2024"
 rust-version = "1.85"

mcf/Cargo.toml

@@ -147,6 +147,15 @@ mod allocating {
             Ok(Self(s))
         }
 
+        /// Borrow the contents of this password hash as a [`PasswordHashRef`].
+        ///
+        /// Similar conversions can be performed using [`AsRef`], [`Borrow`], and [`Deref`], however
+        /// this one is useful when the return type may be ambiguous and avoiding potential
+        /// inference bugs is preferable.
+        pub fn as_password_hash_ref(&self) -> &PasswordHashRef {
+            PasswordHashRef::new_unchecked(&self.0)
+        }
+
         /// Create an [`PasswordHash`] from an identifier.
         ///
         /// # Returns
@@ -207,21 +216,21 @@ mod allocating {
 
     impl AsRef<PasswordHashRef> for PasswordHash {
         fn as_ref(&self) -> &PasswordHashRef {
-            PasswordHashRef::new_unchecked(&self.0)
+            self.as_password_hash_ref()
         }
     }
 
     impl Borrow<PasswordHashRef> for PasswordHash {
         fn borrow(&self) -> &PasswordHashRef {
-            self.as_ref()
+            self.as_password_hash_ref()
         }
     }
 
     impl Deref for PasswordHash {
         type Target = PasswordHashRef;
 
         fn deref(&self) -> &PasswordHashRef {
-            self.as_ref()
+            self.as_password_hash_ref()
         }
     }
 
@@ -231,6 +240,12 @@ mod allocating {
         }
     }
 
+    impl From<&PasswordHash> for String {
+        fn from(hash: &PasswordHash) -> Self {
+            hash.0.clone()
+        }
+    }
+
     impl FromStr for PasswordHash {
         type Err = Error;
 
@@ -267,7 +282,7 @@ mod allocating {
 
     impl<'a> From<&'a PasswordHash> for &'a PasswordHashRef {
         fn from(hash: &'a PasswordHash) -> &'a PasswordHashRef {
-            hash.as_ref()
+            hash.as_password_hash_ref()
         }
     }