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

[Younan Zhang via cfe-commits]

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@@ -42,9 +42,13 @@ IncrementalParser::IncrementalParser(CompilerInstance &Instance,
     External->StartTranslationUnit(Consumer);
 
   P->Initialize();
+  S.RegisterSemaProxy();
 }
 
-IncrementalParser::~IncrementalParser() { P.reset(); }
+IncrementalParser::~IncrementalParser() {
+  S.UnregisterSemaProxy();
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zyn0217 wrote:

Can we just delegate that 'UnregisterSemaProxy' to the destructor of Sema?

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