Fix MA0158 not reported when lock field is initialized in constructor

[Copilot]

MA0158 was silently suppressed when an object lock field was assigned in a constructor (.ctor or .cctor) instead of inline, even if the field was exclusively used in lock statements.

Root Cause

Every assignment to a field (_lock = new object()) produces an IFieldReferenceOperation on the left-hand side. The analyzer treated any field reference whose parent wasn't an ILockOperation as a disqualifying usage, calling ExcludeSymbol — permanently preventing the diagnostic regardless of how the field was used elsewhere.

Fix

Skip field/local references that are assignment targets — they represent writes, not reads, and carry no information about how the symbol is used:

// Assignment targets (e.g., initializations in constructors) are not usages
if (operation.Parent is IAssignmentOperation { Target: var assignTarget } && assignTarget == operation)
    return;

This correctly handles both instance and static constructor initialization:

public sealed class A
{
    private readonly object _lock; // now correctly reported as MA0158

    public A() { _lock = new object(); }

    public void Run() { lock (_lock) { } }
}

Tests Added

• Field initialized in .ctor, used only in lock → diagnostic reported
• Field initialized in .ctor, also used outside lock → no diagnostic
• Static field initialized in .cctor, used only in lock → diagnostic reported
• Static field initialized in .cctor, also used outside lock → no diagnostic

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

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

• 1s1vsblobprodcus386.vsblob.vsassets.io
  • Triggering command: /usr/share/dotnet/dotnet dotnet restore --no-dependencies /home/REDACTED/work/Meziantou.Analyzer/Meziantou.Analyzer/Meziantou.Analyzer.slnx --packages /home/REDACTED/work/Meziantou.Analyzer/.codeql-scratch/dbs/csharp/working/packages /p:DisableImplicitNuGetFallbackFolder=true --verbosity normal /p:TargetFrameworkRootPath=/home/REDACTED/work/Meziantou.Analyzer/.codeql-scratch/dbs/csharp/working/emptyFakeDotnetRoot /p:NetCoreTargetingPackRoot=/home/REDACTED/work/Meziantou.Analyzer/.codeql-scratch/dbs/csharp/working/emptyFakeDotnetRoot /p:AllowMissingPrunePackageData=true (dns block)
  • Triggering command: /usr/share/dotnet/dotnet dotnet restore --no-dependencies /home/REDACTED/work/Meziantou.Analyzer/Meziantou.Analyzer/tests/Meziantou.Analyzer.Test/Meziantou.Analyzer.Test.csproj --packages /home/REDACTED/work/Meziantou.Analyzer/.codeql-scratch/dbs/csharp/working/packages /p:DisableImplicitNuGetFallbackFolder=true --verbosity normal /p:TargetFrameworkRootPath=/home/REDACTED/work/Meziantou.Analyzer/.codeql-scratch/dbs/csharp/working/emptyFakeDotnetRoot /p:NetCoreTargetingPackRoot=/home/REDACTED/work/Meziantou.Analyzer/.codeql-scratch/dbs/csharp/working/emptyFakeDotnetRoot /p:AllowMissingPrunePackageData=true (dns block)
• pdfvsblobprodcus380.vsblob.vsassets.io
  • Triggering command: /usr/share/dotnet/dotnet dotnet restore --no-dependencies /home/REDACTED/work/Meziantou.Analyzer/Meziantou.Analyzer/tests/Meziantou.Analyzer.Test/Meziantou.Analyzer.Test.csproj --packages /home/REDACTED/work/Meziantou.Analyzer/.codeql-scratch/dbs/csharp/working/packages /p:DisableImplicitNuGetFallbackFolder=true --verbosity normal /p:TargetFrameworkRootPath=/home/REDACTED/work/Meziantou.Analyzer/.codeql-scratch/dbs/csharp/working/emptyFakeDotnetRoot /p:NetCoreTargetingPackRoot=/home/REDACTED/work/Meziantou.Analyzer/.codeql-scratch/dbs/csharp/working/emptyFakeDotnetRoot /p:AllowMissingPrunePackageData=true (dns block)
• st8vsblobprodcus339.vsblob.vsassets.io
  • Triggering command: /usr/share/dotnet/dotnet dotnet restore --no-dependencies /home/REDACTED/work/Meziantou.Analyzer/Meziantou.Analyzer/tests/Meziantou.Analyzer.Test/Meziantou.Analyzer.Test.csproj --packages /home/REDACTED/work/Meziantou.Analyzer/.codeql-scratch/dbs/csharp/working/packages /p:DisableImplicitNuGetFallbackFolder=true --verbosity normal /p:TargetFrameworkRootPath=/home/REDACTED/work/Meziantou.Analyzer/.codeql-scratch/dbs/csharp/working/emptyFakeDotnetRoot /p:NetCoreTargetingPackRoot=/home/REDACTED/work/Meziantou.Analyzer/.codeql-scratch/dbs/csharp/working/emptyFakeDotnetRoot /p:AllowMissingPrunePackageData=true (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

---

This section details on the original issue you should resolve

<issue_title>MA0158 is not reported when lock is initialized in .ctor or .cctor</issue_title>
<issue_description>### Version of the Meziantou.Analyzer NuGet package

3.0.11

Rule Identifier

MA0158

Target Framework

.NET 10.0

C# Language version

C# 14

Description

When the lock field is initialized in the instance or static constructor, MA0158 is not reported if the type of the field is not System.Threading.Lock.

Reproduction Steps

Constructor:

public sealed class A
{
    private readonly object _lock; // MA0158 is not reported

    public A()
    {
        _lock = new object();
    }

    public void Run()
    {
        lock (_lock)
        {
        }
    }
}

Type initializer / .cctor:

public sealed class B
{
    private static readonly object Lock; // MA0158 is not reported

    static B()
    {
        Lock = new object();
    }

    public void Run()
    {
        lock (Lock)
        {
        }
    }
}

Other information

No response</issue_description>

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

• Fixes MA0158 is not reported when lock is initialized in .ctor or .cctor #1032

---

🔒 GitHub Advanced Security automatically protects Copilot coding agent pull requests. You can protect all pull requests by enabling Advanced Security for your repositories. Learn more about Advanced Security.