clean up some unsafety in Slicable

substrate/wasm-runtime/polkadot/src/codec/slicable.rs

@@ -34,7 +34,7 @@ pub trait Slicable: Sized {
 	fn to_vec(&self) -> Vec<u8> {
 		self.as_slice_then(|s| s.to_vec())
 	}
-	fn set_as_slice<F: FnOnce(&mut[u8]) -> bool>(set_slice: F) -> Option<Self>;
+	fn set_as_slice<F: FnOnce(&mut [u8]) -> bool>(set_slice: F) -> Option<Self>;
 	fn as_slice_then<R, F: FnOnce(&[u8]) -> R>(&self, f: F) -> R {
 		f(&self.to_vec())
 	}
@@ -44,10 +44,11 @@ pub trait Slicable: Sized {
 /// Trait to mark that a type is not trivially (essentially "in place") serialisable.
 pub trait NonTrivialSlicable: Slicable {}
 
-impl<T: EndianSensitive> Slicable for T {
-	fn set_as_slice<F: FnOnce(&mut[u8]) -> bool>(fill_slice: F) -> Option<Self> {
+// note: the copy bound and static lifetimes are necessary for safety of `set_as_slice`.
+impl<T: Copy + EndianSensitive + 'static> Slicable for T {
+	fn set_as_slice<F: FnOnce(&mut [u8]) -> bool>(fill_slice: F) -> Option<Self> {
 		let size = mem::size_of::<T>();
-		let mut result: T = unsafe { mem::uninitialized() };
+		let mut result: T = unsafe { mem::zeroed() };
 		let result_slice = unsafe {
 			let ptr = &mut result as *mut _ as *mut u8;
 			slice::from_raw_parts_mut(ptr, size)
@@ -77,7 +78,7 @@ impl Slicable for Vec<u8> {
 	fn from_slice(value: &[u8]) -> Option<Self> {
 		Some(value[4..].to_vec())
 	}
-	fn set_as_slice<F: FnOnce(&mut[u8]) -> bool>(_fill_slice: F) -> Option<Self> {
+	fn set_as_slice<F: FnOnce(&mut [u8]) -> bool>(_fill_slice: F) -> Option<Self> {
 		unimplemented!();
 	}
 	fn to_vec(&self) -> Vec<u8> {

substrate/wasm-runtime/polkadot/src/support/primitives.rs

@@ -76,7 +76,7 @@ impl Slicable for Header {
 		})
 	}
 
-	fn set_as_slice<F: FnOnce(&mut[u8]) -> bool>(_fill_slice: F) -> Option<Self> {
+	fn set_as_slice<F: FnOnce(&mut [u8]) -> bool>(_fill_slice: F) -> Option<Self> {
 		unimplemented!();
 	}
 
@@ -122,7 +122,7 @@ impl Slicable for Transaction {
 		})
 	}
 
-	fn set_as_slice<F: FnOnce(&mut[u8]) -> bool>(_fill_slice: F) -> Option<Self> {
+	fn set_as_slice<F: FnOnce(&mut [u8]) -> bool>(_fill_slice: F) -> Option<Self> {
 		unimplemented!();
 	}
 
@@ -200,7 +200,7 @@ impl Slicable for UncheckedTransaction {
 		})
 	}
 
-	fn set_as_slice<F: FnOnce(&mut[u8]) -> bool>(_fill_slice: F) -> Option<Self> {
+	fn set_as_slice<F: FnOnce(&mut [u8]) -> bool>(_fill_slice: F) -> Option<Self> {
 		unimplemented!();
 	}
 
@@ -237,7 +237,7 @@ impl Slicable for Block {
 		})
 	}
 
-	fn set_as_slice<F: FnOnce(&mut[u8]) -> bool>(_fill_slice: F) -> Option<Self> {
+	fn set_as_slice<F: FnOnce(&mut [u8]) -> bool>(_fill_slice: F) -> Option<Self> {
 		unimplemented!();
 	}
 
@@ -271,7 +271,7 @@ impl<T: NonTrivialSlicable> Slicable for Vec<T> {
 		Some(r)
 	}
 
-	fn set_as_slice<F: FnOnce(&mut[u8]) -> bool>(_fill_slice: F) -> Option<Self> {
+	fn set_as_slice<F: FnOnce(&mut [u8]) -> bool>(_fill_slice: F) -> Option<Self> {
 		unimplemented!();
 	}
 

substrate/wasm-runtime/polkadot/src/support/storable.rs

@@ -37,7 +37,7 @@ pub trait Storable {
 /// Remove `key` from storage.
 pub fn kill(key: &[u8]) { runtime_support::set_storage(&twox_128(key)[..], b""); }
 
-impl<T: Default + Sized + EndianSensitive> Storable for T {
+impl<T: Default + Copy + EndianSensitive + 'static> Storable for T {
 	fn lookup(key: &[u8]) -> Option<Self> {
 		Slicable::set_as_slice(|out| runtime_support::read_storage(&twox_128(key)[..], out) == out.len())
 	}