Add s utility function

substrate/frame/support/src/lib.rs

@@ -117,12 +117,27 @@ pub const LOG_TARGET: &str = "runtime::frame-support";
 #[derive(Encode, Decode, Debug, PartialEq, Eq, Clone, TypeInfo)]
 pub enum Never {}
 
+/// Utility function to declare string literals backed by an array of length N.
+/// The input can be shorter than its underlaying array in which case the end of the array is padded
+/// with zeros. It can be used in const contexts.
+pub const fn s<const N: usize>(s: &str) -> [u8; N] {
+	debug_assert!(s.len() <= N, "String literal doesn't fit in array");
+	let mut i = 0;
+	let mut a = [0; N];
+	let s = s.as_bytes();
+	while i < s.len() {
+		a[i] = s[i];
+		i += 1;
+	}
+	a
+}
+
 /// A pallet identifier. These are per pallet and should be stored in a registry somewhere.
 #[derive(Clone, Copy, Eq, PartialEq, Encode, Decode, TypeInfo)]
 pub struct PalletId(pub [u8; 8]);
 
 impl TypeId for PalletId {
-	const TYPE_ID: [u8; 4] = *b"modl";
+	const TYPE_ID: [u8; 4] = s("modl");
 }
 
 /// Generate a [`#[pallet::storage]`](pallet_macros::storage) alias outside of a pallet.
@@ -820,7 +835,7 @@ pub use macro_magic;
 pub mod testing_prelude {
 	pub use super::{
 		assert_err, assert_err_ignore_postinfo, assert_err_with_weight, assert_error_encoded_size,
-		assert_noop, assert_ok, assert_storage_noop, parameter_types, traits::Get,
+		assert_noop, assert_ok, assert_storage_noop, parameter_types, s, traits::Get,
 	};
 	pub use sp_arithmetic::assert_eq_error_rate;
 	pub use sp_runtime::{bounded_btree_map, bounded_vec};
@@ -833,7 +848,7 @@ pub mod pallet_prelude {
 		dispatch::{DispatchClass, DispatchResult, DispatchResultWithPostInfo, Parameter, Pays},
 		ensure,
 		inherent::{InherentData, InherentIdentifier, ProvideInherent},
-		storage,
+		s, storage,
 		storage::{
 			bounded_btree_map::BoundedBTreeMap,
 			bounded_btree_set::BoundedBTreeSet,