How to reproduce:
1. Open the attached project from "halfcastBurst1358209.zip"
2. Navigate to "Jobs > Burst > Open Inspector..."
3. Observe the error of "HalfCastBurstException.Reproduce"

Expected result: "half" has an implicit operator to vectors and should act like it
Actual result: System.NullReferenceException: Object reference not set to an instance of an object error appears

Reproducible with: 1.6.0 (2019.4.30f1, 2020.3.18f1, 2021.1.22f1, 2021.2.0b12, 2022.1.0a9)

Notes:
1. In 1.6.0-pre.3 it appeared as an invalid bit cast error
2. Workaround: One can resolve the issue manually by writing:
float4 x = (float)myHalf;
instead of...
float4 x = myHalf;
3. The issue occurs with float2, float3, float4, double2, double3, and double4 but not with custom types that define implicit conversion functions