including shadows.hlsl causes redefinition error

I'm using Unity 2021.2.0b16.
I'm also almost completely new to shaders, so there's that.

I'm trying to rewrite a shader graph into a shader since I need to do some things which I can't in shader graph

The shader graph I made used a custom function(from a youtube tutorial), and it needs a reference to
ShaderLibrary/Shadows.hlsl
The problem is, when I try to include shadows.hlsl, it gives a redefinition error of 'PackHeightmap' in Common.hlsl if I include UnityCG.cginc, and a redefinition error of '_Time' in UnityInput.hlsl (which happens even if I only include shadows.hlsl)

Am I doing something wrong?
There's more information about *literally anything else* on the internet than this.

Code (Shaderlab):

1. #ifndef CUSTOM_LIGHTING_INCLUDED
2. #define CUSTOM_LIGHTING_INCLUDED
3.  
4. void CalculateMainLight_float(float3 WorldPos, out float3 Direction, out float3 Color,
5.     out half DistanceAtten, out half ShadowAtten) {
6. #ifdef SHADERGRAPH_PREVIEW
7.     Direction = half3(0.5, 0.5, 0);
8.     Color = 1;
9.     DistanceAtten = 1;
10.     ShadowAtten = 1;
11. #else
12. #if SHADOWS_SCREEN
13.     half4 clipPos = TransformWorldToHClip(WorldPos);
14.     half4 shadowCoord = ComputeScreenPos(clipPos);
15. #else
16.     half4 shadowCoord = TransformWorldToShadowCoord(WorldPos);
17. #endif
18.     Light mainLight = GetMainLight(shadowCoord);
19.     Direction = mainLight.direction;
20.     Color = mainLight.color;
21.     DistanceAtten = mainLight.distanceAttenuation;
22.     ShadowAtten = mainLight.shadowAttenuation;
23.  
24. #endif
25. }
26. #endif

Also note that this function works completely fine in Shader Graph.

 

Nevermind. The real reason it was happening was because I was using CGPROGRAM instead of HLSLPROGRAM.
Apparently every tutorial regarding shaders is outdated.

 

If you're writing shaders for the URP or HDRP, then yes, basically every shader tutorial out there is now out of date.