password-hash: improve PHC PasswordVerifier blanket impl (#2182)

Rather than using the `FromStr` impl to parse the associated `Params`
type, it instead bounds on a `TryFrom<phc::ParamsString>` impl, which
provides a more explicit PHC-specific params conversion.

Author: tarcieri

password-hash/src/error.rs

@@ -66,12 +66,6 @@ impl fmt::Display for Error {
 
 impl core::error::Error for Error {}
 
-impl From<core::num::ParseIntError> for Error {
-    fn from(_: core::num::ParseIntError) -> Error {
-        Error::EncodingInvalid
-    }
-}
-
 #[cfg(feature = "getrandom")]
 impl From<getrandom::Error> for Error {
     fn from(_: getrandom::Error) -> Self {

password-hash/src/lib.rs

@@ -166,10 +166,9 @@ pub trait PasswordVerifier<H: ?Sized> {
 }
 
 #[cfg(feature = "phc")]
-impl<T: CustomizedPasswordHasher<phc::PasswordHash>, E> PasswordVerifier<phc::PasswordHash> for T
+impl<T: CustomizedPasswordHasher<phc::PasswordHash>> PasswordVerifier<phc::PasswordHash> for T
 where
-    T::Params: FromStr<Err = E>,
-    Error: From<E>,
+    T::Params: for<'a> TryFrom<&'a phc::ParamsString, Error = Error>,
 {
     fn verify_password(&self, password: &[u8], hash: &phc::PasswordHash) -> Result<()> {
         #[allow(clippy::single_match)]
@@ -180,7 +179,7 @@ where
                     salt,
                     Some(hash.algorithm.as_str()),
                     hash.version,
-                    T::Params::from_str(hash.params.as_str())?,
+                    T::Params::try_from(&hash.params)?,
                 )?;
 
                 if let Some(computed_output) = &computed_hash.hash {