[clang] [libcxx] [Clang] Diagnose forming references to nullptr (PR #143667)

[Shafik Yaghmour via cfe-commits]

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@@ -10912,9 +10966,18 @@ bool RecordExprEvaluator::VisitCXXParenListOrInitListExpr(
                                   isa<CXXDefaultInitExpr>(Init));
 
     APValue &FieldVal = Result.getStructField(Field->getFieldIndex());
-    if (!EvaluateInPlace(FieldVal, Info, Subobject, Init) ||
-        (Field->isBitField() && !truncateBitfieldValue(Info, Init,
-                                                       FieldVal, Field))) {
+    if (Field->getType()->isReferenceType() &&
+        !Field->getType()->isFunctionReferenceType()) {
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shafik wrote:

I see a lot of additional checks against `isFunctionReferenceType()` but:

1) it is not obvious why
2) I don't think these additional clauses are being exercised in the testing, or it is not apparent how. 

https://github.com/llvm/llvm-project/pull/143667