Generic type incorrectly detected as unknown identifier

[WAcry]

Description

When using the DetectIdentifiers method of the Interpreter, generic type (e.g. Tuple<>) is incorrectly detected as an unknown identifier, despite being properly referenced and Eval() works.

var target = new Interpreter();
target.Reference(typeof(Tuple<>));
target.Reference(typeof(Tuple<,>));
target.Reference(typeof(Tuple<,,>));
var expression = "new Tuple<int>(1).Item1";
var result = target.Eval(expression);
Console.WriteLine(result);  // 1
var detectedIdentifiers = target.DetectIdentifiers(expression);
Console.WriteLine(System.Text.Json.JsonSerializer.Serialize(detectedIdentifiers.UnknownIdentifiers)); // ["Tuple"]

I think we can add a KnownGenericTypes, and update DetectIdentifiers

else if (_settings.KnownGenericTypes.TryGetValue(identifier, out ReferenceType knownType))
	knownTypes.Add(knownType);

, but I'm not sure if there's an better fix. Could you take a look when you have time?

[davideicardi]

Thank you @WAcry for the bug report and fix. If you could create a PR I will appreciate it. Otherwise I will try to work on it in the future.

[metoule]

Properly detecting generic types is tricky, because you need to know the type's arity, which requires parsing the type parameters. In your example, we'd want to ensure that detectedIdentifiers.knownTypes contains Tuple<>, but not Tuple<,> nor Tuple<,,>.

It's going to be difficult to implement with the current detection logic, which is based on regular expressions.