From ab7a683546c062a5f05c292fad9a4b71567fa409 Mon Sep 17 00:00:00 2001
From: River Riddle <riddleriver@gmail.com>
Date: Fri, 2 Dec 2022 00:19:28 -0800
Subject: [PATCH] [TypeSwitch] Use perfect forwarding in the cast functions

This allows for properly supporting TypeSwitch on reference
types which do not support copying/do not want copying.
---
 llvm/include/llvm/ADT/TypeSwitch.h | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/llvm/include/llvm/ADT/TypeSwitch.h b/llvm/include/llvm/ADT/TypeSwitch.h
index 044b243..523ff54 100644
--- a/llvm/include/llvm/ADT/TypeSwitch.h
+++ b/llvm/include/llvm/ADT/TypeSwitch.h
@@ -71,8 +71,8 @@ protected:
   /// Attempt to dyn_cast the given `value` to `CastT`. This overload is
   /// selected if `value` already has a suitable dyn_cast method.
   template <typename CastT, typename ValueT>
-  static auto castValue(
-      ValueT value,
+  static decltype(auto) castValue(
+      ValueT &&value,
       std::enable_if_t<is_detected<has_dyn_cast_t, ValueT, CastT>::value> * =
           nullptr) {
     return value.template dyn_cast<CastT>();
@@ -81,8 +81,8 @@ protected:
   /// Attempt to dyn_cast the given `value` to `CastT`. This overload is
   /// selected if llvm::dyn_cast should be used.
   template <typename CastT, typename ValueT>
-  static auto castValue(
-      ValueT value,
+  static decltype(auto) castValue(
+      ValueT &&value,
       std::enable_if_t<!is_detected<has_dyn_cast_t, ValueT, CastT>::value> * =
           nullptr) {
     return dyn_cast<CastT>(value);
-- 
2.7.4