When the "Prefer .clang-tidy file" option is checked, and the .clang-tidy file contains syntax errors, there is no warning shown in the Application Output or anywhere else. It seems to revert to the default checks, which are less strict than mine, resulting in the Analyze->Clang-Tidy command showing success when there should in fact be a ton of diagnostic warnings.

This is quite vexing when I edit the .clang-tidy file by hand. I have to artificially untidy my code to make sure that the .clang-tidy file still works, and then revert my code back to the clean version. Very error-prone for something that's supposed to detect errors!