[pdsl_core] Add IndexMut<u32> impl for storage::Vec

pdsl_core/src/storage/collections/vec/tests.rs

@@ -131,6 +131,24 @@ fn index() {
 	})
 }
 
+#[test]
+fn index_mut() {
+	run_test(|| {
+		let mut vec = {
+			let mut vec = new_empty_vec();
+			vec.push(String::from("Hello"));
+			vec.push(String::from(", "));
+			vec.push(String::from("World!"));
+			assert_eq!(vec.len(), 3);
+			vec
+		};
+		vec[2] = String::from("Substrate!");
+		assert_eq!(vec[0], "Hello");
+		assert_eq!(vec[1], ", ");
+		assert_eq!(vec[2], "Substrate!");
+	})
+}
+
 #[test]
 fn index_comp() {
 	run_test(|| {

pdsl_core/src/storage/collections/vec/vec.rs

@@ -338,7 +338,7 @@ where
 
 impl<T> core::ops::Index<u32> for Vec<T>
 where
-	T: parity_codec::Codec
+	T: parity_codec::Codec,
 {
 	type Output = T;
 
@@ -351,3 +351,17 @@ where
 			)
 	}
 }
+
+impl<T> core::ops::IndexMut<u32> for Vec<T>
+where
+	T: parity_codec::Codec,
+{
+	fn index_mut(&mut self, index: u32) -> &mut Self::Output {
+		self
+			.get_mut(index)
+			.expect(
+				"[pdsl_core::Vec::index] Error: \
+				 expected `index` to be within bounds"
+			)
+	}
+}