[clang] [C23] Fix typeof handling in enum declarations (PR #146394)

[Aaron Ballman via cfe-commits]

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@@ -2850,7 +2870,8 @@ Parser::ParseParenExpression(ParenParseOption &ExprType, bool stopIfCastExpr,
              isFoldOperator(NextToken().getKind())) {
     ExprType = ParenParseOption::FoldExpr;
     return ParseFoldExpression(ExprResult(), T);
-  } else if (isTypeCast) {
+  } else if (CorrectionBehavior == TypoCorrectionTypeBehavior::AllowTypes) {
+    // FIXME: This should not be predicated on typo correction behavior.
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AaronBallman wrote:

This is worth noting!

This was an unfortunate surprise. However, it's a preexisting defect that I don't have the bandwidth to correct right now.

The old `TypeCastState` enumeration was introduced to help with typo correction (https://github.com/llvm/llvm-project/commit/77e21fca3cd1a9db882ac13ac5ddef3f278dfff2) and we accidentally ended up using it for parsing decisions: https://github.com/llvm/llvm-project/blob/a63f57262898588b576d66e5fd79c0aa64b35f2d/clang/lib/Parse/ParseExpr.cpp#L761

https://github.com/llvm/llvm-project/pull/146394