Duplicate method names when inheriting interfaces require explicit interface implementation

[StevenTCramer]

Bug Description

When a class implements multiple interfaces that share method names (like IEnumerable<T> and IEnumerable), the generator creates duplicate public methods with the same name, causing a compilation error. C# requires one of these to use explicit interface implementation.

Steps to Reproduce

1. Create a class that implements IList<T> via delegation (which inherits from both IEnumerable<T> and IEnumerable):

using TimeWarp.SourceGenerators;

public partial class NuruAppBuilder : IList<ServiceDescriptor>
{
  [Implements]
  private ServiceCollection? ServiceCollection;
}

2. Build the project

Expected Behavior

The generator should detect when multiple interfaces define methods with the same name and use explicit interface implementation for the non-generic version:

// Public generic version
public IEnumerator<ServiceDescriptor> GetEnumerator()
{
    return ServiceCollection.GetEnumerator();
}

// Explicit interface implementation for non-generic version
System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
{
    return GetEnumerator();
}

Actual Behavior

The generator creates two public methods with the same name:

public System.Collections.Generic.IEnumerator<ServiceDescriptor> GetEnumerator()
{
    return ServiceCollection.GetEnumerator();
}

public System.Collections.IEnumerator GetEnumerator()  // ERROR: Duplicate method name
{
    return ServiceCollection.GetEnumerator();
}

Compiler Error

error CS0111: Type 'NuruAppBuilder' already defines a member called 'GetEnumerator' with the same parameter types

Environment

• TimeWarp.SourceGenerators: 1.0.0-beta.7
• .NET: 10.0
• OS: Linux (WSL2)

Reproduction Repository

Branch: https://github.com/TimeWarpEngineering/timewarp-nuru/tree/Cramer/2025-10-16/readme-restructure
File: Source/TimeWarp.Nuru/NuruAppBuilder.cs (lines 10, 14-15)
Generated: Source/TimeWarp.Nuru/generated/timewarp-source-generators/TimeWarp.SourceGenerators.InterfaceDelegationGenerator/NuruAppBuilder.implements.g.cs (lines 45, 50)

Impact

This prevents using interface delegation for collection interfaces (IList<T>, IDictionary<K,V>, ISet<T>, etc.) because they all inherit from both generic and non-generic IEnumerable.

Related

• Issue Interface delegation only generates IList members, missing ICollection and IEnumerable #27 (missing inherited interface members) - FIXED in beta.7! ✅
• Issue Indexer generation missing parameter in interface delegation #25 (indexer generation bug) - FIXED in beta.6! ✅

Beta.7 successfully generates all inherited interface members, but hits this C# language constraint with duplicate method names.

Suggested Fix

When generating interface members, detect when multiple interfaces define methods with the same signature (same name and parameters). Make the more-derived/generic version public, and use explicit interface implementation for the base/non-generic version.