Repro steps:
1. Import the attached package
2. Open the shader graph, select the float, and change its mode to 'Integer'
3. Save the graph
4. Observe the console errors:
[Worker0] Shader error in 'Hidden/VFX/New VFX/System/Output Particle Unlit Quad': 'VertVFX': function return value missing semantics at /Projects/VFX/SRP/com.unity.render-pipelines.high-definition/Runtime/ShaderLibrary/VisualEffectVertex.hlsl(18) (on d3d11)