Fix IsEquivalentTo to respect IEquatable<T> implementations

[Copilot]

Description

IsEquivalentTo fails for collections containing types implementing IEquatable<T> (e.g., Vector2, Uri, CultureInfo). The structural comparer attempts to reflect over properties requiring parameters (like indexers), causing "Parameter count mismatch" exceptions.

// Previously failed with TargetParameterCountException
var array = new Vector2[] { new(1, 2), new(3, 4) };
var list = new List<Vector2>(array);
await Assert.That(array).IsEquivalentTo(list);

// Now uses Vector2.Equals(Vector2) automatically

Solution: Modified TypeHelper.IsPrimitiveOrWellKnownType to detect IEquatable<T> implementations:

• Value types implementing IEquatable<T>: Always use their Equals method
• Sealed reference types implementing IEquatable<T>: Use Equals if not compiler-generated
• Records: Continue using structural comparison (preserve existing behavior)

Implementation details:

• Added IsCompilerGeneratedType to detect records via EqualityContract property
• Uses typeof(IEquatable<>) for type-safe interface detection
• Properly annotated with [DynamicallyAccessedMembers] for AOT/trimming

Related Issue

(Issue linking handled by system)

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Performance improvement
• Refactoring (no functional changes)

Checklist

Required

• I have read the Contributing Guidelines
• If this is a new feature, I started a discussion first and received agreement
• My code follows the project's code style (modern C# syntax, proper naming conventions)
• I have written tests that prove my fix is effective or my feature works

TUnit-Specific Requirements

• Dual-Mode Implementation: If this change affects test discovery/execution, I have implemented it in BOTH:
  • Source Generator path (TUnit.Core.SourceGenerator) - N/A (assertions only)
  • Reflection path (TUnit.Engine) - N/A (assertions only)
• Snapshot Tests: If I changed source generator output or public APIs:
  • I ran TUnit.Core.SourceGenerator.Tests and/or TUnit.PublicAPI tests
  • I reviewed the .received.txt files and accepted them as .verified.txt
  • I committed the updated .verified.txt files
• Performance: If this change affects hot paths (test discovery, execution, assertions):
  • I minimized allocations and avoided LINQ in hot paths
  • I cached reflection results where appropriate
• AOT Compatibility: If this change uses reflection:
  • I added appropriate [DynamicallyAccessedMembers] annotations
  • I verified the change works with dotnet publish -p:PublishAot=true

Testing

• All existing tests pass (dotnet test)
• I have added tests that cover my changes
• I have tested both source-generated and reflection modes (if applicable)

Additional Notes

Test coverage:

• IEquatableCollectionTests.cs: Covers Vector2, Vector3, Uri, CultureInfo, DateTimeOffset, custom types
• IssueReproductionTest.cs: Exact scenario from issue
• IEquatableWorkaroundTests.cs: Verifies explicit comparer still works

Verified: 1379 tests pass on .NET 8.0 and 9.0. No breaking changes to records or structural comparison behavior.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>[Bug]: IsEquivalentTo does not respect IEquatable<T></issue_title>
<issue_description>### Description

When using
await Assert.That(array).IsEquivalentTo(array2);
on a type which implement IEquatable<T>, TUnit does not use the IEquatable<T> to check item is equal or not.

Expected Behavior

Test should pass.

Actual Behavior

Test failed.

Steps to Reproduce

[Test]
public async Task Test1()
{
    var array = new Vector2[]
    {
        new Vector2(1, 2),
        new Vector2(3, 4),
        new Vector2(5, 6),
    };
    var array2 = new List<Vector2>(array);
    
    await Assert.That(array).IsEquivalentTo(array2);
}

TUnit Version

1.5.60

.NET Version

.NET9.0

Operating System

Windows

IDE / Test Runner

JetBrains Rider

Error Output / Stack Trace

Parameter count mismatch.
   at System.Reflection.MethodBaseInvoker.ThrowTargetParameterCountException()
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at System.Reflection.PropertyInfo.GetValue(Object obj)
   at TUnit.Assertions.Conditions.Helpers.ReflectionHelper.GetMemberValue(Object obj, MemberInfo member)
   at TUnit.Assertions.Conditions.Helpers.StructuralEqualityComparer`1.CompareStructurally(Object x, Object y, HashSet`1 visited)
   at TUnit.Assertions.Conditions.Helpers.StructuralEqualityComparer`1.Equals(T x, T y)
   at TUnit.Assertions.Conditions.Helpers.CollectionEquivalencyChecker.CheckUnorderedEquivalenceLinear[TItem](List`1 actualList, List`1 expectedList, IEqualityComparer`1 comparer)
   at TUnit.Assertions.Conditions.Helpers.CollectionEquivalencyChecker.CheckUnorderedEquivalence[TItem](List`1 actualList, List`1 expectedList, IEqualityComparer`1 comparer)
   at TUnit.Assertions.Conditions.Helpers.CollectionEquivalencyChecker.AreEquivalent[TItem](IEnumerable`1 actual, IEnumerable`1 expected, CollectionOrdering ordering, IEqualityComparer`1 comparer)
   at TUnit.Assertions.Conditions.IsEquivalentToAssertion`2.CheckAsync(EvaluationMetadata`1 metadata)
   at TUnit.Assertions.Core.Assertion`1.ExecuteCoreAsync()
   at TUnit.Assertions.Core.Assertion`1.AssertAsync()
   at LightProto.AssemblyLevelTests.AssemblyPriorityTests.Test() in D:\repos\LightProto\tests\LightProto.AssemblyLevelTests\AssemblyPriorityTests.cs:line 62
   at TUnit.Core.TestMetadata`1.<>c__DisplayClass13_0.<<get_CreateExecutableTestFactory>b__2>d.MoveNext()
--- End of stack trace from previous location ---
   at TUnit.Core.ExecutableTest.InvokeTestAsync(Object instance, CancellationToken cancellationToken)
   at TUnit.Engine.TestExecutor.ExecuteTestAsync(AbstractExecutableTest executableTest, CancellationToken cancellationToken)
   at TUnit.Engine.TestExecutor.ExecuteAsync(AbstractExecutableTest executableTest, TestInitializer testInitializer, CancellationToken cancellationToken)
   at TUnit.Engine.TestExecutor.ExecuteAsync(AbstractExecutableTest executableTest, TestInitializer testInitializer, CancellationToken cancellationToken)
   at TUnit.Engine.Services.TestExecution.TestCoordinator.<>c__DisplayClass12_0.<<ExecuteTestInternalAsync>b__1>d.MoveNext()
--- End of stack trace from previous location ---
   at TUnit.Engine.Services.TestExecution.TestCoordinator.<>c__DisplayClass12_0.<<ExecuteTestInternalAsync>b__1>d.MoveNext()
--- End of stack trace from previous location ---
   at TUnit.Engine.Helpers.TimeoutHelper.ExecuteWithTimeoutAsync(Func`2 taskFactory, Nullable`1 timeout, CancellationToken cancellationToken, String timeoutMessage)
   at TUnit.Engine.Services.TestExecution.TestCoordinator.<>c__DisplayClass12_0.<<ExecuteTestInternalAsync>b__0>d.MoveNext()
--- End of stack trace from previous location ---
   at TUnit.Engine.Services.TestExecution.RetryHelper.ExecuteWithRetry(TestContext testContext, Func`1 action)
   at TUnit.Engine.Services.TestExecution.RetryHelper.ExecuteWithRetry(TestContext testContext, Func`1 action)
   at TUnit.Engine.Services.TestExecution.TestCoordinator.ExecuteTestInternalAsync(AbstractExecutableTest test, CancellationToken cancellationToken)

Additional Context

If I change
await Assert.That(array).IsEquivalentTo(array2);
to
await Assert.That(array).IsEquivalentTo(array2,EqualityComparer<Vector2>.Default);
test will pass.

There are a lot of type (Uri,CultureInfo,Vector3,Matrix3x2,etc...) has this issue, not just Vector2.

Additionally, IComparable<T> should be considered as well.

IDE-Specific Issue?

• I've confirmed this issue occurs when running via dotnet test or dotnet run, not just in my IDE</issue_description>

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

• Fixes [Bug]: IsEquivalentTo does not respect IEquatable<T> #4081

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