How to reproduce:
1. Open the attached project "TestShaderPrecision.zip"
2. Select Assets/DefaultResourcesExtra/UI/UI-Default.shader
3. Press "Compile and show code" in the Inspector window
Expected results: There is no "vec4" variable in the fragment shader
Actual results: There is a "vec4" variable in the fragment shader
Reproducible with: 2019.4.39f1, 2020.3.35f1, 2021.3.3f1, 2022.1.2f1, 2022.2.0a15
Reproducible on: Windows 10
Public Tracker Link:
https://issuetracker.unity3d.com/product/unity/issues/guid/1411323/