Question [SOLVED] RectMask2D not works with my shader! Why?

This is the vertex and fragment of my shader, what I doing wrong?

Code (CSharp):

1. v2f vert(appdata_t v)
2. {
3.     v2f OUT;
4.     UNITY_SETUP_INSTANCE_ID(v);
5.     UNITY_INITIALIZE_VERTEX_OUTPUT_STEREO(OUT);
6.     OUT.worldPosition = v.vertex;
7.     OUT.vertex = UnityObjectToClipPos(OUT.worldPosition);
8.  
9.     // Calculate the frame index over time
10.     uint index = _FrameCount > 0 ? ((int)(_Time.y / (1 / _Fps)) % _FrameCount) : 0;
11.  
12.     // Set the frame
13.     OUT.texcoord = v.texcoord * _Scale + _Frames[index];
14.  
15.     OUT.color = v.color * _Color;
16.     return OUT;
17. }
18.  
19. fixed4 frag(v2f IN) : SV_Target
20. {
21.     half4 color = (tex2D(_MainTex, IN.texcoord) + _TextureSampleAdd) * IN.color;
22.  
23.     #ifdef UNITY_UI_CLIP_RECT
24.     color.a *= UnityGet2DClipping(IN.worldPosition.xy, _ClipRect);
25.     #endif
26.  
27.     #ifdef UNITY_UI_ALPHACLIP
28.     clip (color.a - 0.001);
29.     #endif
30.  
31.     return color;
32. }

 

Update: Solved by adding built-in source (2020.1.15) to my shader.