SERVER-26674 Add checked_pointer_cast

1 files changed, 37 insertions, 0 deletions

diff --git a/src/mongo/base/checked_cast.h b/src/mongo/base/checked_cast.h
index 94cf5ea9c1f..e434a4c6e12 100644
--- a/src/mongo/base/checked_cast.h
+++ b/src/mongo/base/checked_cast.h
@@ -30,6 +30,8 @@
 
 #pragma once
 
+#include <memory>
+
 #include "mongo/util/assert_util.h"
 #include "mongo/util/debug_util.h"
 
@@ -73,4 +75,39 @@ T checked_cast(const U& u) {
     return checked_cast_impl<kDebugBuild>::cast<T>(u);
 };
 
+/**
+ * Similar to static_pointer_cast, but in debug builds uses RTTI to confirm that the cast
+ * is legal at runtime.
+ */
+template <bool>
+struct checked_pointer_cast_impl;
+
+template <>
+struct checked_pointer_cast_impl<false> {
+    template <typename T, typename U>
+    static std::shared_ptr<T> cast(const std::shared_ptr<U>& u) {
+        return std::static_pointer_cast<T>(u);
+    }
+};
+
+template <>
+struct checked_pointer_cast_impl<true> {
+    template <typename T, typename U>
+    static std::shared_ptr<T> cast(const std::shared_ptr<U>& u) {
+        if (!u) {
+            return nullptr;
+        }
+
+        std::shared_ptr<T> t = std::dynamic_pointer_cast<T>(u);
+        invariant(t);
+
+        return t;
+    }
+};
+
+template <typename T, typename U>
+std::shared_ptr<T> checked_pointer_cast(const std::shared_ptr<U>& u) {
+    return checked_pointer_cast_impl<kDebugBuild>::cast<T>(u);
+};
+
 }  // namespace mongo