Allow passing slice pointer as an interface pointer to Iter.All

.gitignore

@@ -1,2 +1,2 @@
 _harness
-.vscode
+.vscode

session.go

@@ -1453,7 +1453,6 @@ type Index struct {
 // Collation allows users to specify language-specific rules for string comparison,
 // such as rules for lettercase and accent marks.
 type Collation struct {
-
 	// Locale defines the collation locale.
 	Locale string `bson:"locale"`
 
@@ -4408,10 +4407,19 @@ func (iter *Iter) Next(result interface{}) bool {
 //
 func (iter *Iter) All(result interface{}) error {
 	resultv := reflect.ValueOf(result)
-	if resultv.Kind() != reflect.Ptr || resultv.Elem().Kind() != reflect.Slice {
+	if resultv.Kind() != reflect.Ptr {
 		panic("result argument must be a slice address")
 	}
+
 	slicev := resultv.Elem()
+
+	if slicev.Kind() == reflect.Interface {
+		slicev = slicev.Elem()
+	}
+	if slicev.Kind() != reflect.Slice {
+		panic("result argument must be a slice address")
+	}
+
 	slicev = slicev.Slice(0, slicev.Cap())
 	elemt := slicev.Type().Elem()
 	i := 0

session_test.go

@@ -453,6 +453,18 @@ func (s *S) TestInsertFindAll(c *C) {
 	// Ensure result is backed by the originally allocated array
 	c.Assert(&result[0], Equals, &allocd[0])
 
+	// Re-run test destination as a pointer to interface{}
+	var resultInterface interface{}
+
+	anotherslice := make([]R, 5)
+	resultInterface = anotherslice
+	err = coll.Find(nil).Sort("a").All(&resultInterface)
+	c.Assert(err, IsNil)
+	assertResult()
+
+	// Ensure result is backed by the originally allocated array
+	c.Assert(&result[0], Equals, &allocd[0])
+
 	// Non-pointer slice error
 	f := func() { coll.Find(nil).All(result) }
 	c.Assert(f, Panics, "result argument must be a slice address")