Fix O(n²) hash collisions in DuplicateDataRowAnalyzer

[Copilot]

TypedConstantArrayComparer.GetHashCode only hashed Kind and Type, ignoring Value. This caused all [DataRow(T)] attributes sharing the same parameter type to produce identical hashes, degrading every dictionary lookup to O(n) and making duplicate detection O(n²).

Change

Include Value in the hash, matching the logic already present in Equals:

// Before
hashCode.Add(typedConstant.Kind);
hashCode.Add(SymbolEqualityComparer.Default.GetHashCode(typedConstant.Type));

// After
hashCode.Add(typedConstant.Kind);
hashCode.Add(SymbolEqualityComparer.Default.GetHashCode(typedConstant.Type));
if (!typedConstant.IsNull)
{
    if (typedConstant.Kind == TypedConstantKind.Array)
        hashCode.Add(GetHashCode(typedConstant.Values)); // recursive, matches Equals path
    else
        hashCode.Add(typedConstant.Value);
}

• Null values are skipped (consistent with Equals null-handling).
• Array-typed constants are recursively hashed to match the recursive Equals path.
• Restores O(n) behaviour for the common case of multiple [DataRow] attributes on a single test method.

Warning

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  • Triggering command: /home/REDACTED/work/testfx/testfx/artifacts/bin/MSTest.Analyzers.UnitTests/Release/net8.0/MSTest.Analyzers.UnitTests /home/REDACTED/work/testfx/testfx/artifacts/bin/MSTest.Analyzers.UnitTests/Release/net8.0/MSTest.Analyzers.UnitTests --diagnostic --diagnostic-output-directory /home/REDACTED/work/testfx/testfx/artifacts/log/Release --diagnostic-file-prefix MSTest.Analyzers.UnitTests_net8.0_Release_x64 --diagnostic-verbosity trace --crashdump --hangdump --hangdump-timeout 15m --report-azdo --coverage --coverage-settings /home/REDACTED/work/testfx/testfx/test/coverage.config --coverage-output MSTest.Analyzers.UnitTests_net8.0_Release_x64.coverage --filter DuplicateDataRow (dns block)

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[Copilot]

Pull request overview

Improves DuplicateDataRowAnalyzer performance by strengthening hashing for [DataRow] constructor arguments so dictionary lookups don’t degrade due to excessive hash collisions.

Changes:

• Extend TypedConstantArrayComparer.GetHashCode to incorporate TypedConstant.Value when non-null.
• Recursively hash array-typed constants to mirror the recursive equality logic.

Show a summary per file

File	Description
src/Analyzers/MSTest.Analyzers/DuplicateDataRowAnalyzer.cs	Updates hashing logic for typed constants (including arrays) to reduce collisions and improve analyzer performance.

Copilot's findings

• Files reviewed: 1/1 changed files
• Comments generated: 1