[clang] [Clang] Instantiate constexpr function when they are needed. (PR #173537)

[Younan Zhang via cfe-commits]

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@@ -75,11 +75,14 @@
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/Support/TimeProfiler.h"
+#include <memory>
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zyn0217 wrote:

People say we don't want additional headers when they review, and I assume `<memory>` was already included somewhere else...

https://github.com/llvm/llvm-project/pull/173537