Compile error when trying to access StructuredBuffer

I want to access a StructuredBuffer<int>in a compute shader but I get the error:

Shader error in 'Particle.compute': array, matrix, vector, or indexable object type expected in index expression at Particle.compute(28) (on d3d11)

The code:

#pragma kernel CSMain
#include "Assets/Uplus/ZCommon/Resources/ImageProcessing/UplusDirectCompute.cginc"

struct Particle
{
    float3 Position;
    float Mass;
};

Texture2D<float2> _terTx;

ConsumeStructuredBuffer<Particle> currentBuffer;
AppendStructuredBuffer<Particle> nextBuffer;
StructuredBuffer<int> particleCount;

float3 _terPos;
float _terSize, _terPhysicalScale, _resolution;

SamplerState _LinearClamp;
SamplerState _LinearRepeat;

#define _gpSize 512

[numthreads(_gpSize, 1, 1)]
void CSMain(uint3 dispatchID : SV_DispatchThreadID)
{
    int flatID = dispatchID.x;
    int particleCount = particleCount[0];

    if (flatID >= particleCount) return;

    Particle particle = currentBuffer.Consume();

    //Commented the rest of code

    nextBuffer.Append(particle);
}

The error points the line int particleCount = particleCount[0];. Why is that?

The whole idea behind the shader is we have two buffers. We fill one with some data (we call each of them Particle) from CPU and then in the shader consume the data from the buffer, process it and then append to another buffer. then we swap buffers and do another iteration. The particleCount buffer holds the current count of Particles that the buffer holds and the if clause prevents from consuming more Particles than available.

This is an old question so I assume you solved it, but here is the answer anyway:

You are declaring particleCount as an int when it already is a buffer.

Either change the name to int currentParticleCount = particleCount[0]; or just don't use a temporary variable:

if (flatID >= particleCount[0]) return;