From 55afe8f243c21f4bc276c877b4d6ccd716965e13 Mon Sep 17 00:00:00 2001
From: AlexSherbinin <alex.sherbinin.andr@gmail.com>
Date: Thu, 29 Aug 2024 17:46:48 +0300
Subject: [PATCH] fix: replaced empty tuple error types with Infallible

---
 dhkem/src/ecdh_kem.rs   |  6 +++---
 dhkem/src/x25519_kem.rs |  5 +++--
 ml-kem/src/kem.rs       | 18 ++++++++----------
 3 files changed, 14 insertions(+), 15 deletions(-)

diff --git a/dhkem/src/ecdh_kem.rs b/dhkem/src/ecdh_kem.rs
index 8dda9e0..03bf256 100644
--- a/dhkem/src/ecdh_kem.rs
+++ b/dhkem/src/ecdh_kem.rs
@@ -1,7 +1,7 @@
 //! Generic Elliptic Curve Diffie-Hellman KEM adapter.
 
 use crate::{DhDecapsulator, DhEncapsulator, DhKem};
-use core::marker::PhantomData;
+use core::{convert::Infallible, marker::PhantomData};
 use elliptic_curve::{
     ecdh::{EphemeralSecret, SharedSecret},
     CurveArithmetic, PublicKey,
@@ -19,7 +19,7 @@ impl<C> Encapsulate<PublicKey<C>, SharedSecret<C>> for DhEncapsulator<PublicKey<
 where
     C: CurveArithmetic,
 {
-    type Error = ();
+    type Error = Infallible;
 
     fn encapsulate(
         &self,
@@ -38,7 +38,7 @@ impl<C> Decapsulate<PublicKey<C>, SharedSecret<C>> for DhDecapsulator<EphemeralS
 where
     C: CurveArithmetic,
 {
-    type Error = ();
+    type Error = Infallible;
 
     fn decapsulate(&self, encapsulated_key: &PublicKey<C>) -> Result<SharedSecret<C>, Self::Error> {
         let ss = self.0.diffie_hellman(encapsulated_key);
diff --git a/dhkem/src/x25519_kem.rs b/dhkem/src/x25519_kem.rs
index 2deb80c..6cd35fd 100644
--- a/dhkem/src/x25519_kem.rs
+++ b/dhkem/src/x25519_kem.rs
@@ -1,4 +1,5 @@
 use crate::{DhDecapsulator, DhEncapsulator, DhKem};
+use core::convert::Infallible;
 use kem::{Decapsulate, Encapsulate};
 use rand_core::CryptoRngCore;
 use x25519::{PublicKey, ReusableSecret, SharedSecret};
@@ -9,7 +10,7 @@ use x25519::{PublicKey, ReusableSecret, SharedSecret};
 pub struct X25519Kem;
 
 impl Encapsulate<PublicKey, SharedSecret> for DhEncapsulator<PublicKey> {
-    type Error = ();
+    type Error = Infallible;
 
     fn encapsulate(
         &self,
@@ -25,7 +26,7 @@ impl Encapsulate<PublicKey, SharedSecret> for DhEncapsulator<PublicKey> {
 }
 
 impl Decapsulate<PublicKey, SharedSecret> for DhDecapsulator<ReusableSecret> {
-    type Error = ();
+    type Error = Infallible;
 
     fn decapsulate(&self, encapsulated_key: &PublicKey) -> Result<SharedSecret, Self::Error> {
         let ss = self.0.diffie_hellman(encapsulated_key);
diff --git a/ml-kem/src/kem.rs b/ml-kem/src/kem.rs
index 0047125..4abc52a 100644
--- a/ml-kem/src/kem.rs
+++ b/ml-kem/src/kem.rs
@@ -1,3 +1,4 @@
+use core::convert::Infallible;
 use core::marker::PhantomData;
 use hybrid_array::typenum::U32;
 use rand_core::CryptoRngCore;
@@ -85,12 +86,12 @@ impl<P> ::kem::Decapsulate<EncodedCiphertext<P>, SharedKey> for DecapsulationKey
 where
     P: KemParams,
 {
-    // Decapsulation is infallible
-    // XXX(RLB): Maybe we should reflect decryption failure as an error?
-    // TODO(RLB) Make Infallible
-    type Error = ();
+    type Error = Infallible;
 
-    fn decapsulate(&self, encapsulated_key: &EncodedCiphertext<P>) -> Result<SharedKey, ()> {
+    fn decapsulate(
+        &self,
+        encapsulated_key: &EncodedCiphertext<P>,
+    ) -> Result<SharedKey, Self::Error> {
         let mp = self.dk_pke.decrypt(encapsulated_key);
         let (Kp, rp) = G(&[&mp, &self.ek.h]);
         let Kbar = J(&[self.z.as_slice(), encapsulated_key.as_ref()]);
@@ -187,9 +188,7 @@ impl<P> ::kem::Encapsulate<EncodedCiphertext<P>, SharedKey> for EncapsulationKey
 where
     P: KemParams,
 {
-    // TODO(RLB) Make Infallible
-    // TODO(RLB) Swap the order of the
-    type Error = ();
+    type Error = Infallible;
 
     fn encapsulate(
         &self,
@@ -205,8 +204,7 @@ impl<P> crate::EncapsulateDeterministic<EncodedCiphertext<P>, SharedKey> for Enc
 where
     P: KemParams,
 {
-    // TODO(RLB) Make Infallible
-    type Error = ();
+    type Error = Infallible;
 
     fn encapsulate_deterministic(
         &self,