SERVER-40160 Remove `if_constexpr.h` header.

This header circumvented bad formatting which `clang-format-3.8`
imparted to `if constexpr`.  Now `clang-format-7.0.1` imparts
a reasonable format to `if constexpr` so this header is not
needed anymore.

1 files changed, 2 insertions, 3 deletions

diff --git a/src/mongo/executor/scoped_task_executor.cpp b/src/mongo/executor/scoped_task_executor.cpp
index 6f2b4823139..a9b4e32dde8 100644
--- a/src/mongo/executor/scoped_task_executor.cpp
+++ b/src/mongo/executor/scoped_task_executor.cpp
@@ -247,10 +247,9 @@ private:
                 // modify the status field.
                 auto args = cargs;
 
-                IF_CONSTEXPR(std::is_same_v<ArgsT, CallbackArgs>) {
+                if constexpr (std::is_same_v<ArgsT, CallbackArgs>) {
                     args.status = kShutdownStatus;
-                }
-                else {
+                } else {
                     static_assert(std::is_same_v<ArgsT, RemoteCommandOnAnyCallbackArgs>,
                                   "_wrapCallback only supports CallbackArgs and "
                                   "RemoteCommandOnAnyCallbackArgs");