Auto merge of #143074 - compiler-errors:rollup-cv64hdh, r=compiler-errors

Rollup of 18 pull requests

Successful merges:

 - rust-lang/rust#137843 (make RefCell unstably const)
 - rust-lang/rust#140942 (const-eval: allow constants to refer to mutable/external memory, but reject such constants as patterns)
 - rust-lang/rust#142549 (small iter.intersperse.fold() optimization)
 - rust-lang/rust#142637 (Remove some glob imports from the type system)
 - rust-lang/rust#142647 ([perf] Compute hard errors without diagnostics in impl_intersection_has_impossible_obligation)
 - rust-lang/rust#142700 (Remove incorrect comments in `Weak`)
 - rust-lang/rust#142927 (Add note to `find_const_ty_from_env`)
 - rust-lang/rust#142967 (Fix RwLock::try_write documentation for WouldBlock condition)
 - rust-lang/rust#142986 (Port `#[export_name]` to the new attribute parsing infrastructure)
 - rust-lang/rust#143001 (Rename run always )
 - rust-lang/rust#143010 (Update `browser-ui-test` version to `0.20.7`)
 - rust-lang/rust#143015 (Add `sym::macro_pin` diagnostic item for `core::pin::pin!()`)
 - rust-lang/rust#143033 (Expand const-stabilized API links in relnotes)
 - rust-lang/rust#143041 (Remove cache for citool)
 - rust-lang/rust#143056 (Move an ACE test out of the GCI directory)
 - rust-lang/rust#143059 (Fix 1.88 relnotes)
 - rust-lang/rust#143067 (Tracking issue number for `iter_macro`)
 - rust-lang/rust#143073 (Fix some fixmes that were waiting for let chains)

Failed merges:

 - rust-lang/rust#143020 (codegen_fn_attrs: make comment more precise)

r? `@ghost`
`@rustbot` modify labels: rollup

2 files changed, 75 insertions, 0 deletions

diff --git a/library/coretests/tests/cell.rs b/library/coretests/tests/cell.rs
index 781a46c3744..c0ac66e5d2b 100644
--- a/library/coretests/tests/cell.rs
+++ b/library/coretests/tests/cell.rs
@@ -1,4 +1,5 @@
 use core::cell::*;
+use core::mem::forget;
 
 #[test]
 fn smoketest_unsafe_cell() {
@@ -477,3 +478,74 @@ fn const_cells() {
         const _: i32 = CELL.into_inner();
     */
 }
+
+#[test]
+fn refcell_borrow() {
+    // Check that `borrow` is usable at compile-time
+    const {
+        let a = RefCell::new(0);
+        assert!(a.try_borrow().is_ok());
+        assert!(a.try_borrow_mut().is_ok());
+        let a_ref = a.borrow();
+        assert!(*a_ref == 0);
+        assert!(a.try_borrow().is_ok());
+        assert!(a.try_borrow_mut().is_err());
+    }
+}
+
+#[test]
+fn refcell_borrow_mut() {
+    // Check that `borrow_mut` is usable at compile-time
+    const {
+        let mut a = RefCell::new(0);
+        {
+            assert!(a.try_borrow().is_ok());
+            assert!(a.try_borrow_mut().is_ok());
+            let mut a_ref = a.borrow_mut();
+            assert!(*a_ref == 0);
+            *a_ref = 10;
+            assert!(*a_ref == 10);
+            assert!(a.try_borrow().is_err());
+            assert!(a.try_borrow_mut().is_err());
+        }
+        assert!(*a.get_mut() == 10);
+    };
+}
+struct NeverDrop;
+impl Drop for NeverDrop {
+    fn drop(&mut self) {
+        panic!("should never be called");
+    }
+}
+
+#[test]
+fn refcell_replace() {
+    // Check that `replace` is usable at compile-time
+    const {
+        let a = RefCell::new(0);
+        assert!(a.replace(10) == 0);
+        let a = a.into_inner();
+        assert!(a == 10);
+
+        let b = RefCell::new(NeverDrop);
+        forget(b.replace(NeverDrop));
+        forget(b)
+    };
+}
+
+#[test]
+fn refcell_swap() {
+    // Check that `swap` is usable at compile-time
+    const {
+        let (a, b) = (RefCell::new(31), RefCell::new(41));
+        a.swap(&b);
+        let (a, b) = (a.into_inner(), b.into_inner());
+        assert!(a == 41);
+        assert!(b == 31);
+
+        let c = RefCell::new(NeverDrop);
+        let d = RefCell::new(NeverDrop);
+        c.swap(&d);
+        forget((c, d));
+    };
+}
diff --git a/library/coretests/tests/lib.rs b/library/coretests/tests/lib.rs
index b8a5ff620a4..0c54609260f 100644
--- a/library/coretests/tests/lib.rs
+++ b/library/coretests/tests/lib.rs
@@ -15,8 +15,11 @@
 #![feature(cfg_target_has_reliable_f16_f128)]
 #![feature(char_max_len)]
 #![feature(clone_to_uninit)]
+#![feature(const_deref)]
+#![feature(const_destruct)]
 #![feature(const_eval_select)]
 #![feature(const_float_round_methods)]
+#![feature(const_ref_cell)]
 #![feature(const_trait_impl)]
 #![feature(core_float_math)]
 #![feature(core_intrinsics)]