Fix MA0095 to not report for CRTP-inherited IEquatable<T>

[Copilot]

MA0095 was reporting diagnostics when IEquatable<T> was inherited via CRTP (Curiously Recurring Template Pattern), while CA1067 correctly does not. This caused false positives for common base class patterns:

// Base class with CRTP pattern
public abstract class Entity<T> : IEquatable<T> where T : Entity<T>
{
    public bool Equals(T? other) => true;
}

// MA0095 incorrectly fired here, CA1067 did not
public sealed class User : Entity<User>;

Changes

Analyzer logic

• Check if IEquatable<T> is directly declared (via symbol.Interfaces) vs inherited (via symbol.AllInterfaces)
• Only report MA0095 for types that directly declare the interface
• Search entire type hierarchy for Equals(object) override, not just the declaring type

Tests

• Added EqualityShouldBeCorrectlyImplementedAnalyzerMA0095Tests.cs covering:
  • Direct implementation with/without override
  • CRTP inheritance patterns
  • Mixed direct + inherited scenarios

The fix aligns MA0095 behavior with CA1067: types inheriting IEquatable<T> via CRTP are not required to override Equals(object) themselves, as the pattern intentionally delegates equality to the base class.

Warning

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I tried to connect to the following addresses, but was blocked by firewall rules:

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  • Triggering command: /usr/share/dotnet/dotnet exec --runtimeconfig /home/REDACTED/work/Meziantou.Analyzer/Meziantou.Analyzer/tests/Meziantou.Analyzer.Test/bin/Debug/net10.0/Meziantou.Analyzer.Test.runtimeconfig.json --depsfile /home/REDACTED/work/Meziantou.Analyzer/Meziantou.Analyzer/tests/Meziantou.Analyzer.Test/bin/Debug/net10.0/Meziantou.Analyzer.Test.deps.json /home/REDACTED/work/Meziantou.Analyzer/Meziantou.Analyzer/tests/Meziantou.Analyzer.Test/bin/Debug/net10.0/testhost.dll --port 34457 --endpoint 127.0.0.1:034457 --role client --parentprocessid 4269 --datacollectionport 44183 --telemetryoptedin false (dns block)
  • Triggering command: /usr/share/dotnet/dotnet exec --runtimeconfig /home/REDACTED/work/Meziantou.Analyzer/Meziantou.Analyzer/tests/Meziantou.Analyzer.Test/bin/Debug/net10.0/Meziantou.Analyzer.Test.runtimeconfig.json --depsfile /home/REDACTED/work/Meziantou.Analyzer/Meziantou.Analyzer/tests/Meziantou.Analyzer.Test/bin/Debug/net10.0/Meziantou.Analyzer.Test.deps.json /home/REDACTED/work/Meziantou.Analyzer/Meziantou.Analyzer/tests/Meziantou.Analyzer.Test/bin/Debug/net10.0/testhost.dll --port 34339 --endpoint 127.0.0.1:034339 --role client --parentprocessid 4667 --datacollectionport 42301 --telemetryoptedin false (dns block)

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Original prompt

---

This section details on the original issue you should resolve

<issue_title>MA0095 behaves differently to CA1067 with CRTP</issue_title>
<issue_description>### Version of the Meziantou.Analyzer NuGet package

2.0.239

Rule Identifier

MA0095

Target Framework

net9.0

C# Language version

C# 13

Description

Unsure if the difference in behaviour between MA0085 and CA1067 is expected, but MA0095 fires when using CRTP and CA1067 does not. I thought it was worth reporting just in-case. Thanks!

Reproduction Steps

Minimal code:

public abstract class Crtp<T> : IEquatable<T> where T : Crtp<T>
{
    public bool Equals(T? other) => true;
}

public sealed class TriggersMA0095Only : Crtp<TriggersMA0095Only>;

public sealed class TriggersMA0095AndCA1067 : IEquatable<TriggersMA0095AndCA1067>
{
    public bool Equals(TriggersMA0095AndCA1067? other) => true;
}

Other information

Updating Crtp to the following has no change on analyzers that are triggered:

public abstract class Crtp<T> : IEquatable<T> where T : Crtp<T>
{
    public bool Equals(T? other) => true;
    public override bool Equals(object? obj) => true;
    public override int GetHashCode() => 0;
}
```</issue_description>

<agent_instructions>Look at the repro and ensure MA0095 is reported</agent_instructions>

## Comments on the Issue (you are @copilot in this section)

<comments>
</comments>

• Fixes MA0095 behaves differently to CA1067 with CRTP #917

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