I was able to get my C# to D convert to convert about 25% of the .net library v4.6

It converts the following libs:

// System.CodeDom
// System.CodeDom.Compiler
// System.Collections.Concurrent
// System.Collections.Generic
// System.Collections.ObjectModel
// System.Collections.Specialized
// System.ComponentModel
// System.ComponentModel.Design
// System.ComponentModel.Design.Serialization
// System.Configuration
// System.Configuration.Internal
// System.Diagnostics
// System.Diagnostics.CodeAnalysis
// System.IO
// System.IO.Compression
// System.IO.Ports
// System.Media
// System.Timers
// System.Text.RegularExpressions

Not all code works depending on the specific but 90%+ does.

The goal is that, one day, we can effectively replace the phobos with .NET semantics if we want. It, being a nicer library, and all the source code available through reflection, makes it a nice target.  While the source code cannot be distributed, the recompiler can. In C# maps to D farily well, it is not a difficult ask.