How to ask Roslyn to generate an identifier name for me?

Question

As the title says, how do I ask Roslyn to generate an identifier for me, similar to how the pattern matching code fixer or the generate method ones do?

Answer 1

Turns out there is an internal class inside Roslyn that does this, but it does much more than what I need.

Instead, I simply used the semantic model to get the list of visible symbols at the start of my block's span, named my identifier the same as my type (just starting with a lowercase letter) and started adding numbers at the end of it until I get something that's not otherwise visible:

        var symbols = new HashSet<string>(semanticModel.LookupSymbols(bes.SpanStart).Select(s => s.Name));

        var baseIdentifierName = baseType is PredefinedTypeSyntax pts ? pts.Keyword.ValueText : throw new InvalidOperationException();
        if (isArray && !baseIdentifierName.EndsWith("s"))
            baseIdentifierName += "s";
        if (char.IsUpper(baseIdentifierName[0]))
            baseIdentifierName = $"{char.ToLower(baseIdentifierName[0])}{baseIdentifierName.Substring(1)}";

        var identifierName = baseIdentifierName;
        var index = 0;
        while (symbols.Contains(identifierName))
            identifierName = baseIdentifierName + ++index;