[clang] [Clang][ExprConstant] fix constant expression did not evaluate to integer (PR #97146)

[Timm Baeder via cfe-commits]

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@@ -15858,7 +15858,7 @@ static bool FastEvaluateAsRValue(const Expr *Exp, Expr::EvalResult &Result,
   }
 
   if (const auto *CE = dyn_cast<ConstantExpr>(Exp)) {
-    if (CE->hasAPValueResult()) {
+    if (CE->hasAPValueResult() && !CE->getAPValueResult().isLValue()) {
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tbaederr wrote:

It looks like `ConstantExpr::getAPValueResult()` will sometimes create a new APValue, so we should try ti call `getAPValueResult()` only once.

https://github.com/llvm/llvm-project/pull/97146