From 84d3741a47aed43c31349c650d6e21605588e089 Mon Sep 17 00:00:00 2001
From: Ranjit Jhala <rjhala@ucsd.edu>
Date: Fri, 22 Nov 2024 17:54:32 -0800
Subject: [PATCH] more push/scope/mysteries

---
 tests/tests/todo/issue-899c.rs | 58 ++++++++++++++++++++++++++++++++++
 1 file changed, 58 insertions(+)
 create mode 100644 tests/tests/todo/issue-899c.rs

diff --git a/tests/tests/todo/issue-899c.rs b/tests/tests/todo/issue-899c.rs
new file mode 100644
index 0000000000..8475c2dee1
--- /dev/null
+++ b/tests/tests/todo/issue-899c.rs
@@ -0,0 +1,58 @@
+use core::slice::{Iter, SliceIndex};
+
+
+pub trait Queue<T> {
+    /// Returns true if the queue is full, false otherwise.
+    fn is_full(&self) -> bool;
+
+    /// If the queue isn't full, add a new element to the back of the queue.
+    /// Returns whether the element was added.
+    #[flux_rs::sig(fn(self: &strg Self, _) -> bool ensures self: Self)]
+    fn enqueue(&mut self, val: T) -> bool;
+}
+
+
+#[flux_rs::extern_spec]
+impl<T> [T] {
+    #[flux_rs::sig(fn(&[T][@len]) -> usize[len])]
+    fn len(v: &[T]) -> usize;
+}
+
+
+#[flux_rs::refined_by(ring_len: int, hd: int, tl: int)]
+#[flux_rs::invariant(ring_len > 1)]
+pub struct RingBuffer<'a, T: 'a> {
+    #[field({&mut [T][ring_len] | ring_len > 1})]
+    ring: &'a mut [T],
+    #[field({usize[hd] | hd < ring_len})]
+    head: usize,
+    #[field({usize[tl] | tl < ring_len})]
+    tail: usize,
+}
+
+impl<T: Copy> Queue<T> for RingBuffer<'_, T> {
+    fn is_full(&self) -> bool {
+        self.head == ((self.tail + 1) % self.ring.len())
+    }
+
+    #[flux_rs::sig(fn(self: &strg Self, _) -> bool ensures self: Self)]
+    fn enqueue(&mut self, val: T) -> bool {
+        if self.is_full() {
+            // Incrementing tail will overwrite head
+            false
+        } else {
+            self.ring[self.tail] = val;
+            self.tail = (self.tail + 1) % self.ring.len();
+            true
+        }
+    }
+}
+
+// This code causes an ICE
+fn get_ring_buffer() -> &'static mut RingBuffer<'static, usize> {unimplemented!()}
+
+fn enqueue_task() {
+    let rb = get_ring_buffer();
+    rb.enqueue(3);
+}
+