bounded-collections: Fixes Hash impl

bounded-collections/CHANGELOG.md

@@ -4,6 +4,9 @@ The format is based on [Keep a Changelog].
 
 [Keep a Changelog]: http://keepachangelog.com/en/1.0.0/
 
+## [0.1.5] - 2023-02-13
+- Fixed `Hash` impl (previously it could not be used in practice, because the size bound was required to also implement `Hash`).
+
 ## [0.1.4] - 2023-01-28
 - Fixed unnecessary decoding and allocations for bounded types, when the decoded length is greater than the allowed bound.
 - Add `Hash` derivation (when `feature = "std"`) for bounded types.

bounded-collections/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "bounded-collections"
-version = "0.1.4"
+version = "0.1.5"
 authors = ["Parity Technologies <[email protected]>"]
 license = "MIT OR Apache-2.0"
 homepage = "https://github.com/paritytech/parity-common"

bounded-collections/src/bounded_btree_map.rs

@@ -29,7 +29,6 @@ use core::{borrow::Borrow, marker::PhantomData, ops::Deref};
 ///
 /// Unlike a standard `BTreeMap`, there is an enforced upper limit to the number of items in the
 /// map. All internal operations ensure this bound is respected.
-#[cfg_attr(feature = "std", derive(Hash))]
 #[derive(Encode, scale_info::TypeInfo)]
 #[scale_info(skip_type_params(S))]
 pub struct BoundedBTreeMap<K, V, S>(BTreeMap<K, V>, PhantomData<S>);
@@ -237,6 +236,15 @@ where
 	}
 }
 
+// Custom implementation of `Hash` since deriving it would require all generic bounds to also
+// implement it.
+#[cfg(feature = "std")]
+impl<K: std::hash::Hash, V: std::hash::Hash, S> std::hash::Hash for BoundedBTreeMap<K, V, S> {
+	fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
+		self.0.hash(state);
+	}
+}
+
 impl<K, V, S1, S2> PartialEq<BoundedBTreeMap<K, V, S1>> for BoundedBTreeMap<K, V, S2>
 where
 	BTreeMap<K, V>: PartialEq,
@@ -641,4 +649,16 @@ mod test {
 
 		assert_eq!(Ok(b2), b1.try_map(|(_, v)| (v as u16).checked_mul(100_u16).ok_or("overflow")));
 	}
+
+	// Just a test that structs containing `BoundedBTreeMap` can derive `Hash`. (This was broken
+	// when it was deriving `Hash`).
+	#[test]
+	#[cfg(feature = "std")]
+	fn container_can_derive_hash() {
+		#[derive(Hash)]
+		struct Foo {
+			bar: u8,
+			map: BoundedBTreeMap<String, usize, ConstU32<16>>,
+		}
+	}
 }

bounded-collections/src/bounded_btree_set.rs

@@ -29,7 +29,6 @@ use core::{borrow::Borrow, marker::PhantomData, ops::Deref};
 ///
 /// Unlike a standard `BTreeSet`, there is an enforced upper limit to the number of items in the
 /// set. All internal operations ensure this bound is respected.
-#[cfg_attr(feature = "std", derive(Hash))]
 #[derive(Encode, scale_info::TypeInfo)]
 #[scale_info(skip_type_params(S))]
 pub struct BoundedBTreeSet<T, S>(BTreeSet<T>, PhantomData<S>);
@@ -176,6 +175,15 @@ where
 	}
 }
 
+// Custom implementation of `Hash` since deriving it would require all generic bounds to also
+// implement it.
+#[cfg(feature = "std")]
+impl<T: std::hash::Hash, S> std::hash::Hash for BoundedBTreeSet<T, S> {
+	fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
+		self.0.hash(state);
+	}
+}
+
 impl<T, S1, S2> PartialEq<BoundedBTreeSet<T, S1>> for BoundedBTreeSet<T, S2>
 where
 	BTreeSet<T>: PartialEq,
@@ -502,4 +510,16 @@ mod test {
 		let b2: Result<BoundedBTreeSet<u32, ConstU32<1>>, _> = b1.iter().map(|k| k + 1).skip(2).try_collect();
 		assert!(b2.is_err());
 	}
+
+	// Just a test that structs containing `BoundedBTreeSet` can derive `Hash`. (This was broken
+	// when it was deriving `Hash`).
+	#[test]
+	#[cfg(feature = "std")]
+	fn container_can_derive_hash() {
+		#[derive(Hash)]
+		struct Foo {
+			bar: u8,
+			set: BoundedBTreeSet<String, ConstU32<16>>,
+		}
+	}
 }

bounded-collections/src/bounded_vec.rs

@@ -40,7 +40,7 @@ use serde::{
 ///
 /// As the name suggests, the length of the queue is always bounded. All internal operations ensure
 /// this bound is respected.
-#[cfg_attr(feature = "std", derive(Hash, Serialize), serde(transparent))]
+#[cfg_attr(feature = "std", derive(Serialize), serde(transparent))]
 #[derive(Encode, scale_info::TypeInfo)]
 #[scale_info(skip_type_params(S))]
 pub struct BoundedVec<T, S>(pub(super) Vec<T>, #[cfg_attr(feature = "std", serde(skip_serializing))] PhantomData<S>);
@@ -108,7 +108,6 @@ where
 /// A bounded slice.
 ///
 /// Similar to a `BoundedVec`, but not owned and cannot be decoded.
-#[cfg_attr(feature = "std", derive(Hash))]
 #[derive(Encode)]
 pub struct BoundedSlice<'a, T, S>(pub(super) &'a [T], PhantomData<S>);
 
@@ -273,6 +272,15 @@ impl<'a, T, S> Deref for BoundedSlice<'a, T, S> {
 	}
 }
 
+// Custom implementation of `Hash` since deriving it would require all generic bounds to also
+// implement it.
+#[cfg(feature = "std")]
+impl<'a, T: std::hash::Hash, S> std::hash::Hash for BoundedSlice<'a, T, S> {
+	fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
+		self.0.hash(state);
+	}
+}
+
 impl<'a, T, S> core::iter::IntoIterator for BoundedSlice<'a, T, S> {
 	type Item = &'a T;
 	type IntoIter = core::slice::Iter<'a, T>;
@@ -703,6 +711,15 @@ impl<T, S: Get<u32>> TruncateFrom<Vec<T>> for BoundedVec<T, S> {
 	}
 }
 
+// Custom implementation of `Hash` since deriving it would require all generic bounds to also
+// implement it.
+#[cfg(feature = "std")]
+impl<T: std::hash::Hash, S> std::hash::Hash for BoundedVec<T, S> {
+	fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
+		self.0.hash(state);
+	}
+}
+
 // It is okay to give a non-mutable reference of the inner vec to anyone.
 impl<T, S> AsRef<Vec<T>> for BoundedVec<T, S> {
 	fn as_ref(&self) -> &Vec<T> {
@@ -907,7 +924,7 @@ where
 #[cfg(all(test, feature = "std"))]
 mod test {
 	use super::*;
-	use crate::{bounded_vec, ConstU32};
+	use crate::{bounded_vec, ConstU32, ConstU8};
 	use codec::CompactLen;
 
 	#[test]
@@ -1289,4 +1306,17 @@ mod test {
 		assert_eq!(bound, &unbound[..]);
 		assert!(bound == &unbound[..]);
 	}
+
+	// Just a test that structs containing `BoundedVec` and `BoundedSlice` can derive `Hash`. (This was broken when
+	// they were deriving `Hash`).
+	#[test]
+	#[cfg(feature = "std")]
+	fn container_can_derive_hash() {
+		#[derive(Hash)]
+		struct Foo<'a> {
+			bar: u8,
+			slice: BoundedSlice<'a, usize, ConstU8<8>>,
+			map: BoundedVec<String, ConstU32<16>>,
+		}
+	}
 }