Lock analysis doesn't work with static locks that are member variables

[afoxley]

Little standalone example showing the issue: https://godbolt.org/z/6EvMbrvsr

Given:

struct B {
    int resource GUARDED_BY(mutex) = 0;
    static inline std::mutex mutex;
};

struct A {
   
    void acquire() {
        std::lock_guard lock(b.mutex);
        b.resource++;
    }
    B b;
};

int main() {
    A a;
    a.acquire();
}

We get a lock analysis failure:

<source>:17:11: warning: writing variable 'resource' requires holding mutex 'mutex' exclusively [-Wthread-safety-analysis]
   17 |         b.resource++;
      |           ^
1 warning generated.
ASM generation compiler returned: 0
<source>:17:11: warning: writing variable 'resource' requires holding mutex 'mutex' exclusively [-Wthread-safety-analysis]
   17 |         b.resource++;

Even though we are holding the lock.

Build args: -std=c++23 -Wthread-safety -D_LIBCPP_ENABLE_THREAD_SAFETY_ANNOTATIONS=1 -stdlib=libc++

[afoxley]

The issue goes away if you reference the lock via the type name instead of instance. (Thanks @paulkirth@google.com)
std::lock_guard lock(B::mutex);

The question is then whether the initial code should have compiled at all, or whether this is a gap in the analyzer.