[clang] [clang] Disable missing definition warning on pure virtual functions (PR #74510)

[Aaron Ballman via cfe-commits]

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@@ -18931,7 +18931,7 @@ void Sema::MarkFunctionReferenced(SourceLocation Loc, FunctionDecl *Func,
   //   constant evaluated
   bool NeededForConstantEvaluation =
       isPotentiallyConstantEvaluatedContext(*this) &&
-      isImplicitlyDefinableConstexprFunction(Func);
+      isImplicitlyDefinableConstexprFunction(Func) && !Func->isPure();
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AaronBallman wrote:

I don't understand how the function being pure relates to whether it's needed for constant evaluation. I think this should move down to `NeedDefinition` below?

https://github.com/llvm/llvm-project/pull/74510