Visual Studio 2015 appears to complie VB code with C#

Steps to Reproduce:
Create new Visual Basic Analyzer with Code Fix (NuGet + VSIX)
From VSIX project add New Item...
Extensibility/Custom Command called "CustomCommand"
Not required but helps see the issue set the following options
    Option Explicit Off
    Option Strict Off
    Option Infer On
Build Solution

Several files are added and you get 381 warnings for the ComandComand.vb and CustomCommandPackage.vb files. The warnings are "Type or namespace definition or end-of-line expected", "Newline in Comment", "Type Expected" , "Too many characters in character literal"., "Comma Expected". None of which make any sense in a VB file. If I included these 2 files in a C# project and rename them to .cs I get the exact same errors. The errors make no sense for a .VB file. There are no visible errors in the IDE Source window, the errors all appear in the Error Window.