From ebbceeb9e2f6a8f929e089d6182ab14bc24b5be6 Mon Sep 17 00:00:00 2001
From: Rapptz <rapptz@gmail.com>
Date: Fri, 13 Dec 2013 15:40:20 -0500
Subject: [PATCH] Add support for const table operator[] retrieval

---
 sol/table.hpp | 17 +++++++++++------
 tests.cpp     |  9 +++++++++
 2 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/sol/table.hpp b/sol/table.hpp
index 462bb34e..4a444e52 100644
--- a/sol/table.hpp
+++ b/sol/table.hpp
@@ -41,7 +41,7 @@ T* get_ptr(T* val) {
 } // detail
 
 class table : virtual public reference {
-    template<typename T> struct proxy;
+    template<typename T, typename U> struct proxy;
 public:
     table() noexcept : reference() {}
     table(lua_State* L, int index = -1) : reference(L, index) {
@@ -82,8 +82,13 @@ public:
     }
 
     template<typename T>
-    proxy<T> operator[](T&& key) {
-        return proxy<T>(*this, std::forward<T>(key));
+    auto operator[](T&& key) -> decltype(proxy<decltype(*this), T>(*this, std::forward<T>(key))) {
+        return proxy<decltype(*this), T>(*this, std::forward<T>(key));
+    }
+
+    template<typename T>
+    auto operator[](T&& key) const -> decltype(proxy<decltype(*this), T>(*this, std::forward<T>(key))) {
+        return proxy<decltype(*this), T>(*this, std::forward<T>(key));
     }
 
     size_t size() const {
@@ -91,13 +96,13 @@ public:
         return lua_rawlen(state(), -1);
     }
 private:
-    template<typename T>
+    template<typename Table, typename T>
     struct proxy {
     private:
-        table& t;
+        Table t;
         T& key;
     public:
-        proxy(table& t, T& key) : t(t), key(key) {}
+        proxy(Table t, T& key) : t(t), key(key) {}
 
         template<typename U>
         EnableIf<Function<Unqualified<U>>> operator=(U&& other) {
diff --git a/tests.cpp b/tests.cpp
index 10a57b80..a24e92a4 100644
--- a/tests.cpp
+++ b/tests.cpp
@@ -233,4 +233,13 @@ TEST_CASE("tables/operator[]", "Check if operator[] retrieval and setting works
     // function retrieval of a lambda
     sol::function lamb = lua["lamb"];
     REQUIRE(lamb.call<int>(220) == 440);
+
+    // test const table retrieval
+    auto assert1 = [](const sol::table& t) {
+        std::string a = t["foo"];
+        int b = t["bar"];
+        std::cout << a << ',' << b << '\n';
+    };
+
+    REQUIRE_NOTHROW(assert1(lua.global_table()));
 }
\ No newline at end of file