For the following code in C mode: https://godbolt.org/z/3eo1MeGhe
(There is no warning in C++ mode though).
```c++
struct B {
int i : 2;
int : 30; // unnamed bit-field
};
extern void consume_B(struct B);
void bitfield_B_init(void) {
struct B b1;
b1.i = 1; // b1 is initialized
consume_B(b1); // FP: Passed-by-value struct argument contains uninitialized data (e.g., field: '') [core.CallAndMessage]
}
```
iAs listed in the summary D77846, we have 5 different categories of bugs we're
checking for in CallAndMessage. I think the documentation placed in the code
explains my thought process behind my decisions quite well.
A non-obvious change I had here is removing the entry for
CallAndMessageUnInitRefArg. In fact, I removed the CheckerNameRef typed field
back in D77845 (it was dead code), so that checker didn't really exist in any
meaningful way anyways.
Differential Revision: https://reviews.llvm.org/D77866
