Why INamedTypeSymbol.TypeArguments all is INamedTypeSymbol?

[zms9110750]

if (!analyzer.AppendInterfaceSymbol.TypeArguments.IsEmpty)
{
	foreach (ITypeSymbol item in analyzer.AppendInterfaceSymbol.TypeArguments)
	{
		builder.AppendLine($"    类型实际参数：{item.Name} {item is INamedTypeSymbol} {item is IErrorTypeSymbol} {item is ITypeParameterSymbol} ");
	}
	foreach (ITypeSymbol item in analyzer.AppendInterfaceSymbol.TypeParameters)
	{
		builder.AppendLine($"    类型占位符：{item.Name} {item is INamedTypeSymbol} {item is IErrorTypeSymbol} {item is ITypeParameterSymbol} ");
	}
}

the code, T in TypeArguments ,it is IErrorTypeSymbol & INamedTypeSymbol . not is ITypeParameterSymbol.
Is this correct?

i want ITypeParameterSymbol

public class ClassAttributeAnalyzer : AttributeAnalyzerBase
{ 
	public INamedTypeSymbol? AppendInterfaceSymbol => GetCtorTypeSymbol<INamedTypeSymbol>(index: 0);
	  
protected T? GetCtorTypeSymbol<T>(int index) where T : class, ITypeSymbol
{
	if (!HasValidAttribute)
		return null;
 
	if (index < 0 || index >= AttributeData!.ConstructorArguments.Length)
		return null;

	var ctorArg = AttributeData.ConstructorArguments[index]; 

	return ctorArg.Value as T;
}
}

[ExtendWithInterfaceImpl(typeof(IList<>))]
[ExtendWithInterfaceImpl(typeof(IList<int>))]
public static class DictionaryExtensions

类名：DictionaryExtensions
  特性 #1：
    追加接口：IList
    类型实际参数：T True True False 
    类型占位符：T False False True 
  特性 #2：
    追加接口：IList
    类型实际参数：Int32 True False False 
    类型占位符：T False False True 

[333fred]

If you want the type parameters, then use the TypeParameters property. The TypeArguments property contains the substituted arguments for each parameter.

[zms9110750]

I hope to obtain actual parameters.
If he is an actual type, then get INamedTypeSymbol
If he is a type placeholder, then get ITypeParameterSymbol.
I mean, just like Reflection.

My current approach is to use Zip to connect two sequences,
Then determine which side to obtain based on 'is IErrorTypeSymbol'.
But I'm not sure what 'IErrorTypeSymbol' means.
Will the type placeholder receive 'IErrorTypeSymbol'?

[zms9110750]

i want can

foreach (ITypeSymbol item in analyzer.AppendInterfaceSymbol.TypeArguments)
{
				switch (item)
				{
					case INamedTypeSymbol namedType:
						break;

					case ITypeParameterSymbol typeParameter:
						break;
				}
}

but now all is INamedTypeSymbol

[333fred]

I hope to obtain actual parameters.

I know there's a language barrier here, but to understand the api, you need to understand the right words. Parameters are the definition, they're the names that were written by the author of the type. Arguments are the usage, that's the types written by the user of the type when they use it. This is what drives the names of the apis you see here, and what the output is.

But I'm not sure what 'IErrorTypeSymbol' means.

If you are seeing an error type symbol as a type argument, then there is an error and the compiler does not understand what was passed. The name IErrorTypeSymbol isn't a shorthand for anything else, it's exactly what it sounds like: there was an error, and the compiler does not understand what was supposed to be here.

[zms9110750]

if TypeArguments all is INamedTypeSymbol
why it return ImmutableArray<ITypeSymbol> not ImmutableArray`

[CyrusNajmabadi]

TypeArguments is not all INamedTypeSymbol. For example, you can have List<int[]>. In this case, the type arguments will contain the single IArrayTypeSymbol for int[].

[zms9110750]

@CyrusNajmabadi Hi,
I have completed him now.
My way of using it is to add OutputItemType=" Analyzer"to it in the reference project`

But if I want to publish it as nuget so that people can directly reference it without adding OutputItemType=' Analyzer , what do I need to add to the project