[clang] [clang][CompundLiteralExpr] Don't defer evaluation for CLEs (PR #137163)

[Eli Friedman via cfe-commits]

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@@ -9125,9 +9126,25 @@ bool
 LValueExprEvaluator::VisitCompoundLiteralExpr(const CompoundLiteralExpr *E) {
   assert((!Info.getLangOpts().CPlusPlus || E->isFileScope()) &&
          "lvalue compound literal in c++?");
-  // Defer visiting the literal until the lvalue-to-rvalue conversion. We can
-  // only see this when folding in C, so there's no standard to follow here.
-  return Success(E);
+  APValue *Lit;
+  // If CompountLiteral has static storage, its value can be used outside
+  // this expression. So evaluate it once and store it in ASTContext.
+  if (E->hasStaticStorage()) {
+    Lit = E->getOrCreateStaticValue(Info.Ctx);
+    Result.set(E);
+    // Reset any previously evaluated state, otherwise evaluation below might
+    // fail.
+    // FIXME: Should we just re-use the previously evaluated value instead?
+    *Lit = APValue();
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efriedma-quic wrote:

I was thinking about it as a different thing from MaterializeTemporaryExpr... but I guess it's similar enough to a lifetime-extended temporary that we can just adopt the same semantic rules.  Which might not be what a user would expect, but I guess it's at least self-consistent.

Do we need the `Info.EvalMode == EvalInfo::EM_ConstantFold` check from MaterializeTemporaryExpr?

https://github.com/llvm/llvm-project/pull/137163