Fix issue 57

Cargo.toml

@@ -2,7 +2,7 @@
 # dev-dependencies which causes 
 [package]
 name = "slice-deque"
-version = "0.1.15"
+version = "0.1.16"
 authors = ["gnzlbg <gonzalobg88@gmail.com>"]
 description = "A double-ended queue that Deref's into a slice."
 documentation = "https://docs.rs/crate/slice-deque/"

src/lib.rs

@@ -748,7 +748,7 @@ impl<T> SliceDeque<T> {
             new_head += cap as isize;
             debug_assert!(new_head >= 0);
             self.tail_ += cap;
-        } else if new_head as usize > cap {
+        } else if new_head as usize >= cap {
             // cannot panic because new_head >= 0
             // If the new head is larger than the capacity, we shift the range
             // by -capacity to move it towards the first mirrored
@@ -765,6 +765,8 @@ impl<T> SliceDeque<T> {
 
         debug_assert!(self.tail() <= self.tail_upper_bound());
         debug_assert!(self.head() <= self.head_upper_bound());
+
+        debug_assert!(self.head() != self.capacity());
     }
 
     /// Moves the deque head by `x`.
@@ -4128,7 +4130,7 @@ mod tests {
         }
         for _ in v.drain(usize::max_value() - 1..) {}
         assert_eq!(v.len(), usize::max_value() - 1);
-    
+
         let mut v = SliceDeque::<()>::with_capacity(usize::max_value());
         unsafe {
             v.set_len(usize::max_value());
@@ -4310,7 +4312,7 @@ mod tests {
             _ => panic!("invalid `Cow::from`"),
         }
     }
-    
+
     #[test]
         fn vec_from_cow() {
             use std::borrow::Cow;
@@ -4323,7 +4325,7 @@ mod tests {
 
     /* TODO: covariance
     use super::{Drain, IntoIter};
-    
+
     #[allow(dead_code)]
     fn assert_covariance() {
         fn drain<'new>(d: Drain<'static, &'static str>) -> Drain<'new, &'new str> {
@@ -5890,4 +5892,21 @@ mod tests {
             assert_eq!(v.as_ptr() as usize, mem::align_of::<Foo>());
         }
     }
+
+    #[test]
+    fn issue_57() {
+        const C: [i16; 3] = [42; 3];
+
+        let mut deque = SliceDeque::new();
+
+        for _ in 0..918 {
+            deque.push_front(C);
+        }
+
+        for _ in 0..237 {
+            assert_eq!(deque.pop_front(), Some(C));
+            assert!(!deque.is_empty());
+            assert_eq!(*deque.back().unwrap(), C);
+        }
+    }
 }