Version: 3.0.100-preview-009812
Commit: e3abf6e

Runtime Environment:
OS Name: Windows
OS Version: 10.0.17763
OS Platform: Windows
RID: win10-x64
Base Path: C:\Program Files\dotnet\sdk\3.0.100-preview-009812\

Host (useful for support):
Version: 3.0.0-preview-27122-01
Commit: 00c5c8bc40

Have you experienced this same bug with .NET Framework?: No

In the .Net Framework using VB.Net you can compile this Line:

Private Const TabChar As Char = Chr(9)

In .Net Core 3 Preview 1 it failes with:
error BC30059: Constant expression is required.