Add Future and IntoFuture to the 2024 prelude

Implements RFC 3509.

library/core/src/prelude/mod.rs

@@ -54,4 +54,8 @@ pub mod rust_2024 {
  #[unstable(feature = "prelude_2024", issue = "none")]
  #[doc(no_inline)]
  pub use super::rust_2021::*;
+
+ #[unstable(feature = "prelude_2024", issue = "none")]
+ #[doc(no_inline)]
+ pub use crate::future::{Future, IntoFuture};
 }

src/tools/tidy/src/ui_tests.rs

@@ -16,7 +16,8 @@ const ENTRY_LIMIT: usize = 900;
 // FIXME: The following limits should be reduced eventually.
 
 const ISSUES_ENTRY_LIMIT: usize = 1781;
-const ROOT_ENTRY_LIMIT: usize = 871;
+
+const ROOT_ENTRY_LIMIT: usize = 872;
 
 const EXPECTED_TEST_FILE_EXTENSIONS: &[&str] = &[
  "rs", // test source files

tests/ui/rust-2024/prelude2024.rs

@@ -0,0 +1,9 @@
+// check-pass
+// compile-flags: -Zunstable-options
+// edition:2024
+
+fn main() {
+ fut(async {}.into_future(), async {});
+}
+
+fn fut(_: impl Future, _: impl IntoFuture) {}