Remove closed upvalues from the open list

stack.go

@@ -106,14 +106,16 @@ func (l *State) newUpValueAt(level int) *upValue {
 func (l *State) close(level int) {
 	// TODO this seems really inefficient - how can we terminate early?
 	var p *openUpValue
-	for e := l.upValues; e != nil; e, p = e.next, e {
+	for e := l.upValues; e != nil; e = e.next {
 		if e.upValue.isInStackAbove(level) {
 			e.upValue.close()
 			if p != nil {
 				p.next = e.next
 			} else {
 				l.upValues = e.next
 			}
+		} else {
+			p = e
 		}
 	}
 }

stack_test.go

@@ -0,0 +1,29 @@
+package lua
+
+import "testing"
+
+func TestCloseUnlinksAdjacentClosedUpValues(t *testing.T) {
+	l := NewState()
+	l.stack[1] = "kept open"
+	l.stack[2] = "closed first"
+	l.stack[3] = "closed second"
+
+	kept := l.newUpValueAt(1)
+	closedFirst := l.newUpValueAt(2)
+	closedSecond := l.newUpValueAt(3)
+
+	l.close(2)
+
+	if got := closedFirst.value(); got != "closed first" {
+		t.Errorf("first closed upvalue = %v, want %q", got, "closed first")
+	}
+	if got := closedSecond.value(); got != "closed second" {
+		t.Errorf("second closed upvalue = %v, want %q", got, "closed second")
+	}
+	if !kept.isInStackAt(1) {
+		t.Fatal("upvalue below the closing level was closed")
+	}
+	if l.upValues == nil || l.upValues.upValue != kept || l.upValues.next != nil {
+		t.Error("closed upvalues remain in the open upvalue list")
+	}
+}