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

[Corentin Jabot via cfe-commits]

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@@ -215,6 +216,16 @@ struct TypeInfoChars {
   }
 };
 
+/// Interface that allows constant evaluator to call Sema
+/// and mutate the AST.
+struct SemaProxy {
+  virtual ~SemaProxy() = default;
+
+  virtual void
+  InstantiateFunctionDefinition(SourceLocation PointOfInstantiation,
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cor3ntin wrote:

This isn't really consistent with our coding guidelines

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