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====== Shader Compiler ======

==== Bug: Samplers are incorrectly stripped when used with stripped Texture2D ====

Consider this code:

<code>
#pragma shader_feature_local_fragment _ _ALBEDO;
TEXTURE2D(_Albedo);
TEXTURE2D(_Normal);
SAMPLER(sampler_Albedo);

half4 Frag(v2f i)
{
   #if _ALBEDO
      return SAMPLE_TEXTURE2D(_Albedo, sampler_Albedo, i.uv);
   #endif
   
   return SAMPLE_TEXTURE2D(_Normal, sampler_Albedo, i.uv); // we share the albedo sampler
}
</code>

When compiling, two variants are created, one for when albedo is on, another for when it's off. This will throw an error saying that sampler_albedo cannot be found((Note: this error will only be thrown on some platforms (windows)) ((the spelling of the error is wrong, as it's all lowercase when the variable is not)):
''"sampler_texname not found" compile error when sharing samplers''

DX9 associates samplers with textures, and so Unity does too. When you set a Unity Texture to ''Clamp'', it sets '-''clamp'' on sampler_<TEXTURENAME>. When the variant with ''_ALBEDO'' not defined is compiled, the compiler strips the albedo texture because it's not being used.

**However**, Unity assumes that since ''sampler_Albedo'' is associated with the ''_Albedo'' texture, it should be stripped as well, even though the sampler is also being used by the ''_Normal''.

Possible workarounds:
  * Give the _Normal texture its own sampler
  * Use a sampler not associated with a texture (which means the user cannot edit it via the texture settings)
  * Make sure you always sample the texture associated with the sampler so it doesn't get stripped. Something like:

<code>
result *= saturate(1 + SAMPLE_TEXTURE2D_LOD(_Albedo, sampler_Albedo, float2(0,0), 11));
return result;
</code>

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