Meaningful changes from aggressive-clippy

I do want to enable a few specific lints, yet aggressive-clippy as a whole
isn't worthwhile.

crypto/frost/src/tests/mod.rs

@@ -27,7 +27,7 @@ pub const PARTICIPANTS: u16 = 5;
 pub const THRESHOLD: u16 = ((PARTICIPANTS * 2) / 3) + 1;
 
 /// Clone a map without a specific value.
-pub fn clone_without<K: Clone + std::cmp::Eq + std::hash::Hash, V: Clone>(
+pub fn clone_without<K: Clone + core::cmp::Eq + core::hash::Hash, V: Clone>(
   map: &HashMap<K, V>,
   without: &K,
 ) -> HashMap<K, V> {
@@ -177,8 +177,8 @@ pub fn sign<R: RngCore + CryptoRng, M: PreprocessMachine>(
     machines,
     |rng, machines| {
       // Cache and rebuild half of the machines
-      let mut included = machines.keys().cloned().collect::<Vec<_>>();
-      for i in included.drain(..) {
+      let included = machines.keys().cloned().collect::<Vec<_>>();
+      for i in included {
         if (rng.next_u64() % 2) == 0 {
           let cache = machines.remove(&i).unwrap().cache();
           machines.insert(
@@ -226,7 +226,7 @@ pub fn test_offset_schnorr<R: RngCore + CryptoRng, C: Curve, H: Hram<C>>(rng: &m
 
   let offset = C::F::from(5);
   let offset_key = group_key + (C::generator() * offset);
-  for (_, keys) in keys.iter_mut() {
+  for keys in keys.values_mut() {
     *keys = keys.offset(offset);
     assert_eq!(keys.group_key(), offset_key);
   }

crypto/frost/src/tests/nonces.rs

@@ -176,13 +176,8 @@ pub fn test_invalid_commitment<R: RngCore + CryptoRng, C: Curve>(rng: &mut R) {
   let nonce =
     preprocess.commitments.nonces.get_mut(usize::try_from(rng.next_u64()).unwrap() % 2).unwrap();
   let generators_len = nonce.generators.len();
-  *nonce
-    .generators
-    .get_mut(usize::try_from(rng.next_u64()).unwrap() % generators_len)
-    .unwrap()
-    .0
-    .get_mut(usize::try_from(rng.next_u64()).unwrap() % 2)
-    .unwrap() = C::G::random(&mut *rng);
+  nonce.generators[usize::try_from(rng.next_u64()).unwrap() % generators_len].0
+    [usize::try_from(rng.next_u64()).unwrap() % 2] = C::G::random(&mut *rng);
 
   // The commitments are validated at time of deserialization (read_preprocess)
   // Accordingly, serialize it and read it again to make sure that errors

crypto/frost/src/tests/vectors.rs

@@ -166,8 +166,8 @@ pub fn test_with_vectors<R: RngCore + CryptoRng, C: Curve, H: Hram<C>>(
     }
 
     let mut commitments = HashMap::new();
-    let mut machines = machines
-      .drain(..)
+    let machines = machines
+      .into_iter()
       .enumerate()
       .map(|(c, (i, machine))| {
         let nonce = |i| {
@@ -224,8 +224,8 @@ pub fn test_with_vectors<R: RngCore + CryptoRng, C: Curve, H: Hram<C>>(
       .collect::<Vec<_>>();
 
     let mut shares = HashMap::new();
-    let mut machines = machines
-      .drain(..)
+    let machines = machines
+      .into_iter()
       .enumerate()
       .map(|(c, (i, machine))| {
         let (machine, share) = machine
@@ -242,9 +242,9 @@ pub fn test_with_vectors<R: RngCore + CryptoRng, C: Curve, H: Hram<C>>(
         shares.insert(*i, machine.read_share::<&[u8]>(&mut share.as_ref()).unwrap());
         (i, machine)
       })
-      .collect::<HashMap<_, _>>();
+      .collect::<Vec<_>>();
 
-    for (i, machine) in machines.drain() {
+    for (i, machine) in machines {
       let sig = machine.complete(clone_without(&shares, i)).unwrap();
       let mut serialized = sig.R.to_bytes().as_ref().to_vec();
       serialized.extend(sig.s.to_repr().as_ref());
@@ -347,7 +347,7 @@ pub fn test_with_vectors<R: RngCore + CryptoRng, C: Curve, H: Hram<C>>(
       machines.push((i, AlgorithmMachine::new(IetfSchnorr::<C, H>::ietf(), keys[i].clone())));
     }
 
-    for (i, machine) in machines.drain(..) {
+    for (i, machine) in machines {
       let (_, preprocess) = machine.preprocess(&mut frosts.clone());
 
       // Calculate the expected nonces