[clang] [Clang] Ensure ``if consteval`` consititute an immediate function context (PR #91939)

[via cfe-commits]

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@@ -7964,6 +7964,15 @@ TreeTransform<Derived>::TransformIfStmt(IfStmt *S) {
   // Transform the "then" branch.
   StmtResult Then;
   if (!ConstexprConditionValue || *ConstexprConditionValue) {
+    Sema::ExpressionEvaluationContext Context =
+        S->isNonNegatedConsteval()
+            ? Sema::ExpressionEvaluationContext::ImmediateFunctionContext
+            : Sema::ExpressionEvaluationContext::PotentiallyEvaluated;
+
+    EnterExpressionEvaluationContext Ctx(
+        getSema(), Context, nullptr,
+        Sema::ExpressionEvaluationContextRecord::EK_Other);
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cor3ntin wrote:

You are right, it's nicer this way, thanks.

https://github.com/llvm/llvm-project/pull/91939