I write C# and rust fulltime. Native discriminated unions (and their integration throughout the ecosystem) are often the deciding factor when choosing rust over C#.

Very hard to imagine teams cross shopping C# and Rust and DU's being the deciding factor. The tool chains, workflows, and use cases are just so different, IMO. What heuristics were your team using to decide between the two?

This surprises me.

If you want the .NET ecosystem and GC conveniences, there is already F#. If you want no GC and RAII-style control, then you would already pick Rust.