• Loading assemblies: AssemblySymbolLoader
• Traversing assemblies and generating syntax tree: CSharpFileBuilder.cs
• Usage of Simplifier.ReduceAsync(document)

Simplifier.ReduceAsync has second parameter OptionSet? optionSet = null, but I wasn't able to find any option
related to nullability. Plus, nullability for Plain Old Data like int, bool is "simplified" correctly, but for string, user defined types, interfaces - not.

public string? AssemblyPath { get { throw null; } }
public void WithAssemblyPath(string? path) { throw null; }

After roundtrip: source -> ISymbol-> SyntaxGenerator -> source:

public string AssemblyPath { get { throw null; } }
public void WithAssemblyPath(string path) { throw null; }