WrapperOpaque: Use decode_all to decode from the Vec<u8> (#11726)

This ensures that there isn't any extra data attached that isn't used.

substrate/frame/support/src/traits/misc.rs

@@ -745,7 +745,7 @@ impl<T: Encode> Encode for WrapperOpaque<T> {
 
 impl<T: Decode> Decode for WrapperOpaque<T> {
 	fn decode<I: Input>(input: &mut I) -> Result<Self, codec::Error> {
-		Ok(Self(T::decode(&mut &<Vec<u8>>::decode(input)?[..])?))
+		Ok(Self(T::decode_all(&mut &<Vec<u8>>::decode(input)?[..])?))
 	}
 
 	fn skip<I: Input>(input: &mut I) -> Result<(), codec::Error> {
@@ -967,6 +967,10 @@ mod test {
 			2usize.pow(14) - 1 + 2
 		);
 		assert_eq!(<WrapperOpaque<[u8; 2usize.pow(14)]>>::max_encoded_len(), 2usize.pow(14) + 4);
+
+		let data = 4u64;
+		// Ensure that we check that the `Vec<u8>` is consumed completly on decode.
+		assert!(WrapperOpaque::<u32>::decode(&mut &data.encode().encode()[..]).is_err());
 	}
 
 	#[test]