Add a non-canonical SCALE derivations feature

Enables representing IUMT within `StorageValues`. Applied to a variety of
values.

Fixes a bug where `Some([0; 32])` would be considered a valid block anchor.

substrate/primitives/Cargo.toml

@@ -32,5 +32,6 @@ bech32 = { version = "0.11", default-features = false }
 rand_core = { version = "0.6", default-features = false, features = ["std"] }
 
 [features]
+non_canonical_scale_derivations = []
 std = ["zeroize/std", "borsh/std", "ciphersuite/std", "dkg/std", "sp-core/std", "bech32/std"]
 default = ["std"]

substrate/primitives/src/balance.rs

@@ -10,18 +10,10 @@ use crate::coin::{ExternalCoin, Coin};
 pub type AmountRepr = u64;
 
 /// A wrapper used to represent amounts.
-#[derive(
-  Clone,
-  Copy,
-  PartialEq,
-  Eq,
-  PartialOrd,
-  Ord,
-  Hash,
-  Debug,
-  Zeroize,
-  BorshSerialize,
-  BorshDeserialize,
+#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, Zeroize, BorshSerialize, BorshDeserialize)]
+#[cfg_attr(
+  feature = "non_canonical_scale_derivations",
+  derive(scale::Encode, scale::Decode, scale::MaxEncodedLen)
 )]
 pub struct Amount(pub AmountRepr);
 
@@ -48,6 +40,10 @@ impl Mul for Amount {
 
 /// An ExternalCoin and an Amount, forming a balance for an external coin.
 #[derive(Clone, Copy, PartialEq, Eq, Debug, Zeroize, BorshSerialize, BorshDeserialize)]
+#[cfg_attr(
+  feature = "non_canonical_scale_derivations",
+  derive(scale::Encode, scale::Decode, scale::MaxEncodedLen)
+)]
 pub struct ExternalBalance {
   /// The coin this is a balance for.
   pub coin: ExternalCoin,
@@ -78,6 +74,10 @@ impl Mul<Amount> for ExternalBalance {
 
 /// A Coin and an Amount, forming a balance for a coin.
 #[derive(Clone, Copy, PartialEq, Eq, Debug, Zeroize, BorshSerialize, BorshDeserialize)]
+#[cfg_attr(
+  feature = "non_canonical_scale_derivations",
+  derive(scale::Encode, scale::Decode, scale::MaxEncodedLen)
+)]
 pub struct Balance {
   /// The coin this is a balance for.
   pub coin: Coin,

substrate/primitives/src/coin.rs

@@ -9,6 +9,10 @@ use crate::network_id::{ExternalNetworkId, NetworkId};
 /// This type serializes to a subset of `Coin`.
 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, Zeroize, BorshSerialize, BorshDeserialize)]
 #[borsh(use_discriminant = true)]
+#[cfg_attr(
+  feature = "non_canonical_scale_derivations",
+  derive(scale::Encode, scale::Decode, scale::MaxEncodedLen)
+)]
 #[non_exhaustive]
 pub enum ExternalCoin {
   /// Bitcoin, from the Bitcoin network.
@@ -31,6 +35,10 @@ impl ExternalCoin {
 
 /// The type used to identify coins.
 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, Zeroize)]
+#[cfg_attr(
+  feature = "non_canonical_scale_derivations",
+  derive(scale::Encode, scale::Decode, scale::MaxEncodedLen)
+)]
 pub enum Coin {
   /// The Serai coin.
   Serai,

substrate/primitives/src/merkle.rs

@@ -67,7 +67,8 @@ impl UnbalancedMerkleTree {
 }
 
 /// An unbalanced Merkle tree which is incrementally created.
-#[derive(Clone, PartialEq, Eq, Debug, BorshSerialize, BorshDeserialize)]
+#[derive(Clone, PartialEq, Eq, Debug)]
+#[cfg_attr(feature = "non_canonical_scale_derivations", derive(scale::Encode, scale::Decode))]
 pub struct IncrementalUnbalancedMerkleTree {
   /// (number of children under branch, branch hash)
   branches: Vec<(u64, [u8; 32])>,