[clang] [clang][test] Add test for comma operator rejection in preprocessor conditionals (PR #155570)

[NohHyeon Kwon via cfe-commits]

================
@@ -0,0 +1,26 @@
+// RUN: %clang_cc1 -E -pedantic-errors %s -verify -std=c++98
+// RUN: %clang_cc1 -E -pedantic-errors %s -verify -std=c++11
+// RUN: %clang_cc1 -E -pedantic-errors %s -verify -std=c++14
+// RUN: %clang_cc1 -E -pedantic-errors %s -verify -std=c++17
+// RUN: %clang_cc1 -E -pedantic-errors %s -verify -std=c++20
+// RUN: %clang_cc1 -E -pedantic-errors %s -verify -std=c++23
+
+// Test 1: Top-level comma
+// expected-error at +1 {{expected end of line in preprocessor expression}}
+#if 1, 2
+#endif
----------------
swote-git wrote:

Missing test case for #elif needs to be corrected. 

Thank you for your thoughtful review!

https://github.com/llvm/llvm-project/pull/155570