This helps to avoid duplicating warnings in cases like:
```
> cat test.cpp
void bar(int);
void foo(const int &);
void test(bool a) {
int v = v;
if (a)
bar(v);
else
foo(v);
}
> clang++.exe test.cpp -fsyntax-only -Wuninitialized
test.cpp:4:11: warning: variable 'v' is uninitialized when used within its own initialization [-Wuninitialized]
4 | int v = v;
| ~ ^
test.cpp:4:11: warning: variable 'v' is uninitialized when used within its own initialization [-Wuninitialized]
4 | int v = v;
| ~ ^
2 warnings generated.
```
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