Vulkan: How to use vk::BufferPointer for VBOs?

[namandixit]

I am trying to use vk::BufferPointer in HLSL (to SPIR-V) for vertex buffers like following:

struct Vertex {
    float3 position;
};

struct VertexBuffer {
    Vertex vertices[];
};

[[vk::push_constant]] struct {
    vk::BufferPointer<VertexBuffer> vbo;
} push_constants;

struct VertInput {
    uint vertexID : SV_VertexID;
};

Vert2Frag vertMain(VertInput input)
{
    Vertex v = push_constants.vbo.Get().vertices[input.vertexID];

    ...
}

But this gives error: array dimensions of struct/class members must be explicit

I am guessing that HLSL doesn't support flexible array members. So what is the correct way of using vk::BufferPointer for an array of structs whose length is not known at compile time?