[clang] [clang] fix constexpr-unknown handling of self-references. (PR #132990)

[Shafik Yaghmour via cfe-commits]

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@@ -3629,17 +3644,17 @@ static bool evaluateVarDeclInit(EvalInfo &Info, const Expr *E,
 
   Result = VD->getEvaluatedValue();
 
-  // C++23 [expr.const]p8
-  // ... For such an object that is not usable in constant expressions, the
-  // dynamic type of the object is constexpr-unknown. For such a reference that
-  // is not usable in constant expressions, the reference is treated as binding
-  // to an unspecified object of the referenced type whose lifetime and that of
-  // all subobjects includes the entire constant evaluation and whose dynamic
-  // type is constexpr-unknown.
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shafik wrote:

Please move this up to `CheckUninitReference`

https://github.com/llvm/llvm-project/pull/132990