[clang] [Clang] Reconsider the timing of instantiation of local constexpr lambdas (PR #98758)

[via cfe-commits]

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@@ -16983,6 +16995,30 @@ Sema::VerifyIntegerConstantExpression(Expr *E, llvm::APSInt *Result,
   SmallVector<PartialDiagnosticAt, 8> Notes;
   EvalResult.Diag = &Notes;
 
+  // Check if the expression refers to local functions yet to be instantiated.
+  // If so, instantiate them now, as the constant evaluation requires the
+  // function definition.
+  if (!PendingLocalImplicitInstantiations.empty()) {
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cor3ntin wrote:

Can you explain why we check for not having pending instantiations ?

https://github.com/llvm/llvm-project/pull/98758