Fix ring not being removed correctly

cache.go

@@ -184,8 +184,8 @@ func (c *Cache) Evict(key interface{}) {
 	}
 	c.wg.Add(1)
 	go func() {
-		r := value.(*record)
 		defer c.wg.Done()
+		r := value.(*record)
 		value, ok := r.LoadAndDelete()
 		if !ok {
 			return

cache_test.go

@@ -300,7 +300,7 @@ var _ = Describe("overflow when setting values", func() {
 					return nil, nil
 				})
 				closer.Close()
-				Expect(c.Len()).To(BeNumerically("<=", n+overflow))
+				Expect(c.Len()).To(BeNumerically("<=", n), "capacity cannot be exceeded")
 			}
 
 			Eventually(func() uint64 {

ring.go

@@ -39,7 +39,11 @@ func (l *lfuRing) Push(key interface{}, r *ring.Ring) (lfuKey interface{}) {
 	l.cursor = r
 	l.size++
 	if l.capacity > 0 && l.size > l.capacity {
-		return l.unlink(l.cursor.Next())
+		lfuKey = l.unlink(l.cursor.Next())
+		if lfuKey == key {
+			panic("evcache: lfuKey cannot be key")
+		}
+		return lfuKey
 	}
 	return nil
 }
@@ -48,8 +52,9 @@ func (l *lfuRing) Push(key interface{}, r *ring.Ring) (lfuKey interface{}) {
 func (l *lfuRing) Remove(r *ring.Ring) (key interface{}) {
 	l.mu.Lock()
 	defer l.mu.Unlock()
-	if r == r.Next() && r != l.cursor {
-		// A single ring element not belonging to lfuRing.
+	if r.Value == nil {
+		// An overflowed ring which was already unlinked by l.Push
+		// but the record not yet evicted.
 		return nil
 	}
 	return l.unlink(r)
@@ -59,6 +64,11 @@ func (l *lfuRing) Remove(r *ring.Ring) (key interface{}) {
 func (l *lfuRing) Promote(r *ring.Ring, hits uint32) {
 	l.mu.Lock()
 	defer l.mu.Unlock()
+	if r.Value == nil {
+		// An overflowed ring which was already unlinked by l.Push
+		// but the record not yet evicted.
+		return
+	}
 	if l.cursor == nil {
 		panic("evcache: cursor must not be nil")
 	}
@@ -83,6 +93,9 @@ func (l *lfuRing) Promote(r *ring.Ring, hits uint32) {
 }
 
 func (l *lfuRing) unlink(r *ring.Ring) (key interface{}) {
+	if r.Value == nil {
+		panic("evcache: r.Value must not be nil")
+	}
 	if l.cursor == nil {
 		panic("evcache: cursor must not be nil")
 	}