# Extra Clang Tools 21.1.6 documentation

## clang-tidy - bugprone-forward-declaration-namespace

# bugprone-forward-declaration-namespace

Checks if an unused forward declaration is in a wrong namespace.

The check inspects all unused forward declarations and checks if there is any declaration/definition with the same name existing, which could indicate that the forward declaration is in a potentially wrong namespace.

    namespace na { struct A; }
    namespace nb { struct A {}; }
    nb::A a;
    // warning : no definition found for 'A', but a definition with the same name
    // 'A' found in another namespace 'nb::'

This check can only generate warnings, but it can’t suggest a fix at this point.