[clang++] Unnecessary warning "non-void function does not return a value in all control paths"

[mkornaukhov03]

I have the following snippet:

int foo(int) {
    bool matched = false;
    do {
      if (matched) {
        break;
      }
        return 42;
    } while(false);
}


int main() {
    foo(42);
}

I compile it with clang++-18:

$ clang++-18 --version
Ubuntu clang version 18.1.8 (++20240731024944+3b5b5c1ec4a3-1~exp1~20240731145000.144)
Target: x86_64-pc-linux-gnu
Thread model: posix
$ clang++-18 -Wreturn-type main.cpp 
main.cpp:9:1: warning: non-void function does not return a value in all control paths [-Wreturn-type]
    9 | }
      | ^
1 warning generated.

Variable matched is effectively constant and there are no paths that "do not return a value".
The expected behavior is such that there should be no such warning.

[chrchr-github]

Reduced:

int foo() {
    /*const*/ bool b = true;
    if (b) 
        return 42;
}

const b prevents the warning.

[mkornaukhov03]

Initial snippet was something like that:

int foo(int x) {
    bool matched = false;
    do {
      if (matched) {
        label: return 0;
      }

      if (matched || x == 1) {
        matched = true;
        return 123;
      }
      if (matched || x == 2) {
        matched = true;
        return 456;
      }

      if (matched) {
        break;
      }
      goto label;
    } while(false);
}

Which shouldn't have warning, too. But I reduced it to the snippet that is in description.
In fact even this things:

int foo(int x) {
    bool matched = false;

    if (matched) return 1;
    if (!matched) return 2;
}

emits warning.