[llvm] ab7a683 - [TypeSwitch] Use perfect forwarding in the cast functions

[River Riddle via llvm-commits]

Author: River Riddle
Date: 2022-12-02T00:48:35-08:00
New Revision: ab7a683546c062a5f05c292fad9a4b71567fa409

URL: https://github.com/llvm/llvm-project/commit/ab7a683546c062a5f05c292fad9a4b71567fa409
DIFF: https://github.com/llvm/llvm-project/commit/ab7a683546c062a5f05c292fad9a4b71567fa409.diff

LOG: [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.

Added: 
    

Modified: 
    llvm/include/llvm/ADT/TypeSwitch.h

Removed: 
    


################################################################################
diff  --git a/llvm/include/llvm/ADT/TypeSwitch.h b/llvm/include/llvm/ADT/TypeSwitch.h
index 044b2432b8243..523ff544a02b5 100644
--- a/llvm/include/llvm/ADT/TypeSwitch.h
+++ b/llvm/include/llvm/ADT/TypeSwitch.h
@@ -71,8 +71,8 @@ template <typename DerivedT, typename T> class TypeSwitchBase {
   /// 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 @@ template <typename DerivedT, typename T> class TypeSwitchBase {
   /// 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);