Confusing (*this) cast of a pointer

Question

This is code from Transform.h in ROS (link) in the Transform class.

/**@brief Return the transform of the vector */
TFSIMD_FORCE_INLINE Vector3 operator*(const Vector3& x) const
{
    return (*this)(x);
}

Can someone explain what this piece of code is doing? Here is what I think (for context, I have a few years experience as a C programmer, first time developing in C++.)

The function is called when the following is invoked

object_of_type_Transform * object_of_type_Vector3

It then casts the Vector3 object into a Transform object and returns that as a result (I am quite unclear about how this can be possible as the two types do not seem compatible).

But the result being returned is a Vector3... and this is where my mental model breaks down.

Additionally, the function is supposed to be transforming a Vector3 point based on the Transform class... so my understanding is definitely flawed somewhere.

I would appreciate any insights.

Thanks

EDIT

Thanks for the reply! The function right above is:

/**@brief Return the transform of the vector */
TFSIMD_FORCE_INLINE Vector3 operator()(const Vector3& x) const
{
    return Vector3(m_basis[0].dot(x) + m_origin.x(), 
    m_basis[1].dot(x) + m_origin.y(), 
    m_basis[2].dot(x) + m_origin.z());
}

/**@brief Return the transform of the vector */
TFSIMD_FORCE_INLINE Vector3 operator*(const Vector3& x) const
{
    return (*this)(x);
}

I understand, now, whats going on. Thanks again.

Answer 1

It then casts the Vector3 object into a Transform object and returns that as a result

No. No cast is taking place; this:

return (*this)(x);

is equivalent to:

return this->operator()(x);

In both cases the code is invoking Transform::operator() and passing x to it. The parentheses in the first code are necessary because () binds stronger than * so without the parentheses around *this the code would be equivalent to return *(this(x)); – a compilation error.

Incidentally, this is quite idiomatic C++ code but I can see how the syntax can be confusing for C programmers (where, after all, you cannot overload operators, let alone operator()).