Missing warning if variable is used in else clause of if (type_t var = ...)

[Alcaro]

int* get_something();
int* get_something_else();
int square() {
    if (int* ptr1 = get_something())
        return ptr1[0] * ptr1[0];
    else if (int* ptr2 = get_something_else())
        return ptr1[0] * ptr2[0]; // whoops, typoed!
    else
        return -1;
}

Expected: Compiler warning about how ptr1 is always null on the commented line. (Simplifying the example further returns an unused-variable warning for ptr2; that's not what I'm asking for.)

Actual: No output, just pretends ptr1[0] is 0 and optimizes accordingly. (Ideally, ptr1 would only be in scope in its then-clause, not throughout the entire if-statement, but that's not how the C++ spec looks.)

https://godbolt.org/z/118vGjE43

[arrowten]

I have created a PR for this. Please check:
#156436