Trailing OpTypeRuntimeArray in Uniform Struct

[spencer-lunarg]

Taking the hlsl

struct T2 {
    float4 _m0;
};

[[vk::binding(0)]]
    cbuffer ubo : register(b0) {
    int in_val;
    T2 _z0[];
}

float4 main() : SV_TARGET {
    uint x = in_val;
    float4 data = _z0[x]._m0;
    return data;
}

slangc in.hlsl -o out.spv -emit-spirv-directly -target spirv -enable-effect-annotations -entry main -stage fragment it will produce invalid spirv because Vulkan requires Uniform can't have a runtime array if inside a Block

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if ran with dxc it will give an error

in.hlsl:8:5: error: definition of variable with array type needs an explicit size or an initializer
        T2 _z0[];