SourceGenerator Get all classes which implement an interface decorated by an attribute

Question

I am trying to create a source generator for some automationg purpose. My target types are some classes which implement unknown interfaces. Those interfaces are decorated with a custom attribute. By searching everywhere, I can only find samples where people have attributes directly on target type, which unfortunately does not work in this case.

Here's that sample target code:

public sealed class SomeAttribute : Attribute
{

}

[Some]
public interface IA
{

}

internal sealed class A : IA
{

}

But in source generator ClassDeclarationSyntax does not seems to provide interfaces, instead I can only get attributes. This answer given here Roslyn CSharpSyntaxRewriter Get A List of Implemented Interfaces says that we can do following:

var root = classDeclarationSyntax.SyntaxTree.GetRoot();
var model = compilation.GetSemanticModel(root.SyntaxTree);
ISymbol? symbol = model.GetDeclaredSymbol(root.DescendantNodes().OfType<ClassDeclarationSyntax>().First())

var implementedInterfaces = symbol.AllInterfaces;

But this does not work for me as symbol does not contain AllInterfaces property. My question how can I get interface list from ClassDeclarationSyntax?

Shoaib Shakeel · Accepted Answer · 2022-11-04 21:25:43Z

3

figured it out. We need to cast symbol to ITypeSymbol like below:

var interfaces = ((ITypeSymbol)symbol).AllInterfaces

answered Nov 4, 2022 at 21:25

Shoaib Shakeel

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