> There are no "built-in" arrays in C++. There's C-style arrays,

They're built-in arrays. The C++11 n3290 specification calls them arrays in section 8.1. The use of "array" is used regularly elsewhere in the specification. They are built in to the language. There is no warning from clang compiling C++ code that these should not be used.

The trouble with C++ builtin arrays is they have no bounds checking and promptly decay to pointers at every opportunity. Despite the obsolete nature of them, people still use them. There's no switch to turn them off.

Where's the C++ guarantee that code doesn't use those builtin arrays?