Fix MSTEST0037: Report diagnostic for BCL types with user-defined operators

[Copilot]

MSTEST0037 was not reporting diagnostics for BCL types like TimeSpan and DateTime because their comparison operators are user-defined. The analyzer conservatively excluded all user-defined operators to avoid false positives.

Changes

• Added IsBCLType helper - Identifies BCL types by comparing assembly public keys (same approach as existing IsBCLCollectionType)

• Updated operator recognition methods to allow user-defined operators from BCL types:

  • RecognizeComparisonCheck - comparison operators (>, >=, <, <=)
  • RecognizeEqualityCheck - equality operators (==, !=)
  • IsEqualsNullBinaryOperator, IsNotEqualsNullBinaryOperator - null checks
  • RecognizeNullCheck - wrapper for null checks

• Added tests for TimeSpan, DateTime, and user-defined types to prevent regressions

Example

Before:

var ts1 = TimeSpan.Zero;
var ts2 = TimeSpan.FromSeconds(1);
Assert.IsTrue(ts2 > ts1);  // No diagnostic

After:

Assert.IsTrue(ts2 > ts1);  // MSTEST0037: Use 'Assert.IsGreaterThan'

User-defined types remain unaffected:

Assert.IsTrue(myCustomType > anotherCustomType);  // No diagnostic (correct)

Fixes #3982

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Original prompt

---

This section details on the original issue you should resolve

<issue_title>MSTEST0037 not reported for (alll) types that implement IComparable</issue_title>
<issue_description>In MSTest v3.10.4, MSTEST0037 is currently not reported for all types that implement IComparable.

Steps To Reproduce

Compile the following code (with MSTest analyzers enabled):

using System;

using Microsoft.VisualStudio.TestTools.UnitTesting;

[TestClass]
public sealed class MSTEST0037Tests
{
    [TestMethod]
    public void TimeSpanComparison()
    {
        var ts1 = TimeSpan.Zero;
        var ts2 = TimeSpan.Zero;

        Assert.IsTrue(ts2 > ts1);
        Assert.IsTrue(ts2 >= ts1);
        Assert.IsTrue(ts2 < ts1);
        Assert.IsTrue(ts2 <= ts1);
        Assert.IsTrue(ts2 == ts1);
        Assert.IsTrue(ts2 != ts1);
    }

    [TestMethod]
    public void DateTimeComparison()
    {
        var ts1 = DateTime.Today;
        var ts2 = DateTime.Today;

        Assert.IsTrue(ts2 > ts1);
        Assert.IsTrue(ts2 >= ts1);
        Assert.IsTrue(ts2 < ts1);
        Assert.IsTrue(ts2 <= ts1);
        Assert.IsTrue(ts2 == ts1);
        Assert.IsTrue(ts2 != ts1);
    }
}

Expected behavior

MSTEST0037 is reported for each usage of Assert.IsTrue(...).

Actual behavior

MSTEST0037 is not reported at all.</issue_description>

<agent_instructions>Maybe what we can do here is exclude anything coming from the BCL from the user-defined operator check.</agent_instructions>

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

@Youssef1313 This is most likely because those operators are considered as user-defined operators, and we try to avoid false positives for user-defined operators. Maybe what we can do here is exclude anything coming from the BCL from the user-defined operator check. @Evangelink I think it would be valid for runtime team. We did the exclusion just as a safeguard because we don't know if people would implement comparison "correctly"

• Fixes MSTEST0037 not reported for (alll) types that implement IComparable<T> #6591

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