[stable2407] Backport #5632 (#5633)

Backport #5632 into `stable2407` (cc @clangenb).

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  # To be used by other automation, do not modify:
  original-pr-number: #${pull_number}
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Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>
Co-authored-by: clangenb <37865735+clangenb@users.noreply.github.com>
Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

prdoc/pr_5632.prdoc

@@ -0,0 +1,13 @@
+# Schema: Polkadot SDK PRDoc Schema (prdoc) v1.0.0
+# See doc at https://raw.githubusercontent.com/paritytech/polkadot-sdk/master/prdoc/schema_user.json
+
+title: Fix `alloc` not found error in `format_runtime_string!`
+
+doc:
+  - audience: Runtime Dev
+    description: |
+      Fixes the macro hygiene in the `format_runtime_string!` macro to fix the `alloc` not found build error.
+
+crates:
+  - name: sp-runtime
+    bump: patch

substrate/primitives/runtime/src/lib.rs

@@ -49,7 +49,7 @@
 extern crate alloc;
 
 #[doc(hidden)]
-pub use alloc::vec::Vec;
+pub use alloc::{format, vec::Vec};
 #[doc(hidden)]
 pub use codec;
 #[doc(hidden)]
@@ -79,8 +79,6 @@ use sp_core::{
 	sr25519,
 };
 
-#[cfg(all(not(feature = "std"), feature = "serde"))]
-use alloc::format;
 use alloc::vec;
 use codec::{Decode, Encode, MaxEncodedLen};
 use scale_info::TypeInfo;

substrate/primitives/runtime/src/runtime_string.rs

@@ -50,7 +50,7 @@ macro_rules! format_runtime_string {
 		}
 		#[cfg(not(feature = "std"))]
 		{
-			sp_runtime::RuntimeString::Owned(alloc::format!($($args)*).as_bytes().to_vec())
+			sp_runtime::RuntimeString::Owned($crate::format!($($args)*).as_bytes().to_vec())
 		}
 	}};
 }