[clang] Add more tests for _Countof (PR #133333)

[Aaron Ballman via cfe-commits]

================
@@ -144,3 +177,13 @@ void test_compound_literals() {
   static_assert(_Countof((int[2]){}) == 2);
   static_assert(_Countof((int[]){1, 2, 3, 4}) == 4);	
 }
+
+static int test_f1();
+static int test_f2();  // expected-warning {{never defined}}
+
+void test_symbols() {
+  int a[global_num][global_num];
+
+  static_assert(_Countof(global_multi_array[test_f1()]) == 34);
+  (void)_Countof(a[test_f2()]);
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AaronBallman wrote:

Sounds good! Worth adding a comment explaining that so others don't wonder as well.

https://github.com/llvm/llvm-project/pull/133333