[clang] better error message for while loops outside of control flow

report an error when encountering 'while' token parsing declarator

```
clang/test/Parser/while-loop-outside-function.c:3:1: error: while loop outside of a function
while // expected-error {{while loop outside of a function}}
^
clang/test/Parser/while-loop-outside-function.c:7:1: error: while loop outside of a function
while // expected-error {{while loop outside of a function}}
^
```

Fixes: https://github.com/llvm/llvm-project/issues/34462

Differential Revision: https://reviews.llvm.org/D129573

1 files changed, 2 insertions, 0 deletions

diff --git a/clang/include/clang/Basic/DiagnosticParseKinds.td b/clang/include/clang/Basic/DiagnosticParseKinds.td
index 352a050b..bad6c09 100644
--- a/clang/include/clang/Basic/DiagnosticParseKinds.td
+++ b/clang/include/clang/Basic/DiagnosticParseKinds.td
@@ -538,6 +538,8 @@ def err_invalid_operator_on_type : Error<
   "cannot use %select{dot|arrow}0 operator on a type">;
 def err_expected_unqualified_id : Error<
   "expected %select{identifier|unqualified-id}0">;
+def err_while_loop_outside_of_a_function : Error<
+  "while loop outside of a function">; 
 def err_brackets_go_after_unqualified_id : Error<
   "brackets are not allowed here; to declare an array, "
   "place the brackets after the %select{identifier|name}0">;