From 28e290347c2e56850ed7362edb96f9a9a587688a Mon Sep 17 00:00:00 2001
From: Anton Medvedev <anton@medv.io>
Date: Tue, 21 Aug 2018 22:29:29 +0700
Subject: [PATCH] Add possibility to use "in" operator with maps and structs.

---
 eval_test.go | 35 +++++++++++++++++++++++++++++++++++
 runtime.go   | 26 ++++++++++++++++++++++++++
 2 files changed, 61 insertions(+)

diff --git a/eval_test.go b/eval_test.go
index 92066b0c4..7c62cd4f8 100644
--- a/eval_test.go
+++ b/eval_test.go
@@ -249,6 +249,26 @@ var evalTests = []evalTest{
 		nil,
 		true,
 	},
+	{
+		`"a" in {a:1, b:2}`,
+		nil,
+		true,
+	},
+	{
+		`"Bar" in Foo`,
+		struct{ Foo struct{ Bar bool } }{struct{ Bar bool }{true}},
+		true,
+	},
+	{
+		`"Bar" in Ptr`,
+		struct{ Ptr *struct{ Bar bool } }{&struct{ Bar bool }{true}},
+		true,
+	},
+	{
+		`"Bar" in NilPtr`,
+		struct{ NilPtr *bool }{nil},
+		false,
+	},
 	{
 		`0 in nil`,
 		nil,
@@ -432,6 +452,21 @@ var evalErrorTests = []evalErrorTest{
 		nil,
 		`operator "in" not defined on string`,
 	},
+	{
+		`nil in map`,
+		map[string]interface{}{"map": map[string]interface{}{"true": "yes"}},
+		`cannot use <nil> as index to map[string]interface {}`,
+	},
+	{
+		`nil in foo`,
+		map[string]interface{}{"foo": struct{ Bar bool }{true}},
+		`cannot use <nil> as field name of struct { Bar bool }`,
+	},
+	{
+		`true in foo`,
+		map[string]interface{}{"foo": struct{ Bar bool }{true}},
+		`cannot use bool as field name of struct { Bar bool }`,
+	},
 	{
 		"len()",
 		nil,
diff --git a/runtime.go b/runtime.go
index ab620b46a..43c5ed653 100644
--- a/runtime.go
+++ b/runtime.go
@@ -115,6 +115,32 @@ func contains(needle interface{}, array interface{}) (bool, error) {
 				}
 			}
 			return false, nil
+		case reflect.Map:
+			n := reflect.ValueOf(needle)
+			if !n.IsValid() {
+				return false, fmt.Errorf("cannot use %T as index to %T", needle, array)
+			}
+			value := v.MapIndex(n)
+			if value.IsValid() {
+				return true, nil
+			}
+			return false, nil
+		case reflect.Struct:
+			n := reflect.ValueOf(needle)
+			if !n.IsValid() || n.Kind() != reflect.String {
+				return false, fmt.Errorf("cannot use %T as field name of %T", needle, array)
+			}
+			value := v.FieldByName(n.String())
+			if value.IsValid() {
+				return true, nil
+			}
+			return false, nil
+		case reflect.Ptr:
+			value := v.Elem()
+			if value.IsValid() && value.CanInterface() {
+				return contains(needle, value.Interface())
+			}
+			return false, nil
 		}
 		return false, fmt.Errorf("operator \"in\" not defined on %T", array)
 	}