[clang] [C] Handle comma operator for implicit int->enum conversions (PR #138752)

[Erich Keane via cfe-commits]

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@@ -11647,6 +11647,29 @@ static void DiagnoseFloatingImpCast(Sema &S, Expr *E, QualType T,
   }
 }
 
+static void CheckCommaOperand(Sema &S, Expr *E, QualType T, SourceLocation CC,
+                              bool Check) {
+  E = E->IgnoreParenImpCasts();
+  AnalyzeImplicitConversions(S, E, CC);
+
+  if (Check && E->getType() != T)
+    S.CheckImplicitConversion(E, T, CC);
+}
+
+/// Analyze the given comma operator. The basic idea behind the analysis is to
+/// analyze the left and right operands slightly differently. The left operand
+/// needs to check whether the operand itself has an implicit conversion, but
+/// not whether the left operand induces an implicit conversion for the entire
+/// comma expression itself. This is similar to how CheckConditionalOperand
+/// behaves; it's as-if the correct operand were directly used for the implicit
+/// conversion check.
+static void AnalyzeCommaOperator(Sema &S, BinaryOperator *E, QualType T) {
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erichkeane wrote:

Can we give a better name to 'T'?  Something like `FinalExprTy` or `CastToTy` or something?  

https://github.com/llvm/llvm-project/pull/138752