How to reproduce:
1. Open the attached 'iTestCase.zip' project
2. Switch Platform to iOS in Build Settings
3. Build for iOS and open the Xcode project
4. Deploy Xcode project to an iOS device

Expected result: The blue cube is displayed in the Scene and no errors are thrown to the Xcode console
Actual result: Scene is empty and 'program_source:199:50: error: assigning to 'float4' (vector of 4 'float' values) from incompatible type 'threadgroup half4' (vector of 4 'half' values) output.COLOR0 = input.cp[controlPointID].COLOR0;' error it thrown to the Xcode console

Reproducible with: 2018.4.27f1, 2019.4.13f1, 2020.1.9f1, 2020.2.0b7, 2021.1.0a1

Reproducible with:
iPhone 8+ (iOS 12.0)
iPhone XR (iOS 13.4.1)
iPad 9.7’ 6th gen (iOS 14.2)

Not reproducible:
macOS 11.0 Beta Big Sur

Notes:
- Reproducible on Metal, not reproducible on Open GLES 3
- Shader is taken from the documentation: https://docs.unity3d.com/Manual/SL-SurfaceShaderTessellation.html
- Shader works fine when the displacement feature is included #pragma
- When using displacement, Unity Shader Compiler does not include COLOR semantic to Mtl VertexOut and ControlPoint structs