sampler2d object has no methods

Hello there. I'm trying to write my shader, in order to get a depth texture that has to be assigned to the camera, in order to get a black-and-white description of the distance of the objects within the scene from the rendering camera.

This is the code ( from https://forum.unity.com/threads/camera-depth-texture-sampling-with-2018-3-and-hdrp-4-x-mip-map-issue.594160/ ):

     Shader "Unlit/DepthShade"
     {
         Properties
         {
             _MainTex ("Decal Texture", 2D) = "white" {}
         }
      
         HLSLINCLUDE
         #include "UnityCG.cginc"
         #include "HLSLSupport.cginc"
          
         #include "Packages/com.unity.render-pipelines.core/ShaderLibrary/Common.hlsl"
         #include "Packages/com.unity.render-pipelines.core/ShaderLibrary/API/D3D11.hlsl"
         #include "Packages/com.unity.render-pipelines.core/ShaderLibrary/API/GLCore.hlsl"
         #include "Packages/com.unity.render-pipelines.core/ShaderLibrary/Macros.hlsl"
         #include "Packages/com.unity.render-pipelines.core/ShaderLibrary/UnityInstancing.hlsl"
         #include "Packages/com.unity.render-pipelines.high-definition/Runtime/ShaderLibrary/ShaderVariables.hlsl"
         ENDHLSL
          
         CGINCLUDE
         #include "UnityCG.cginc"
         #include "HLSLSupport.cginc"
         ENDCG
          
         SubShader
         {
             Tags{ "Queue"="Geometry+1" }
          
             Pass
             {
                 ZWrite Off
                 Blend SrcAlpha OneMinusSrcAlpha
          
                 HLSLPROGRAM
                 #pragma target 3.0
                 #pragma vertex vert
                 #pragma fragment frag
          
                 struct v2f
                 {
                     float4 pos : SV_POSITION;
                     float4 screenUV : TEXCOORD0;
                     float3 ray : TEXCOORD1;
                 };
                    
                 v2f vert (appdata_base v)
                 {
                     v2f o;
                     o.pos = UnityObjectToClipPos (v.vertex);
                     o.screenUV = ComputeScreenPos (o.pos);
                     o.ray = UnityObjectToViewPos(v.vertex).xyz * float3(-1,-1,1);
                     return o;
                 }
          
                 sampler2D _MainTex;
                 sampler2D _CameraDepthTexture;
                 float4 frag(v2f i) : SV_Target
                 {
                     i.ray = i.ray * (_ProjectionParams.z / i.ray.z);
                     float2 uv = i.screenUV.xy / i.screenUV.w;
                        
                     float depth = LOAD_TEXTURE2D(_CameraDepthTexture, uv);
                        
                     depth = Linear01Depth (depth);
                        
                     float4 vpos = float4(i.ray * depth,1);
                     float3 wpos = mul (unity_CameraToWorld, vpos).xyz;
                     float3 opos = mul (unity_WorldToObject, float4(wpos,1)).xyz;
                     clip (float3(0.5,0.5,0.5) - abs(opos.xyz));
                        
                     float2 texUV = opos.xz + 0.5;
          
                     float4 col = tex2D (_MainTex, texUV);
                     return col;
                 }
                 ENDHLSL
             }
         }
          
         Fallback Off
     }

However, the compiler gives the following error: sampler2d object has no methods.

Any ideas?