Always use the core prelude

Author: ivmarkov

.github/workflows/ci.yml

@@ -10,7 +10,7 @@ on:
   workflow_dispatch:
 
 env:
-  rust_toolchain: stable
+  rust_toolchain: nightly
 
 jobs:
   compile:

src/lib.rs

@@ -1,6 +1,11 @@
-#![cfg_attr(not(feature = "std"), no_std)]
+#![no_std]
 #![allow(async_fn_in_trait)]
 
+#[cfg(feature = "std")]
+#[allow(unused_imports)]
+#[macro_use]
+extern crate std;
+
 #[cfg(feature = "alloc")]
 #[allow(unused_imports)]
 #[macro_use]