Missing a compilation null reference warning for a particular case.

[phoeniceus]

Type of issue

Missing information

Description

When you call a class constructor and it throws an exception, it still calls the finalizer. This code throws a null reference exception, however there is no null reference warning when the code compiled. Can we get that warning added or an explanantion why it is not there?

  public class Foo
  {
    private string _name;
    private Bar _bar;

    public Foo(string name)
    {
      ArgumentNullException.ThrowIfNullOrEmpty(name);
      _name = name;
      _bar = new Bar();
    }

    ~Foo()
    {
      Dispose();
    }

    public void Dispose()
    {
      _bar.Dispose(); // This is the line throwing the null reference exception.
        GC.SuppressFinalize(this);
    }
  }

  public class Bar: IDisposable
  {
    public void Dispose() { }
  }

  public void Main()
  {
     var foo = new Foo(string.Empty);
  }

Page URL

https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/compiler-messages/nullable-warnings

Content source URL

https://github.com/dotnet/docs/blob/main/docs/csharp/language-reference/compiler-messages/nullable-warnings.md

Document Version Independent Id

df58b52a-2532-8241-72cd-f40e9096037d

Article author

@BillWagner

Metadata

• ID: 812f0144-80de-6b49-dded-97eeb7bc373d
• Service: dotnet-csharp
• Sub-service: errors-warnings

Related Issues

[BillWagner]

Hi @phoeniceus

Yes, this is a one of a number of holes in the nullability static analysis. In general, full static analysis on fields is going to have some holes. The static analysis can't predict what order public methods are accessed. And, as your example points out, static analysis can't determine if a method (like a constructor) completes without a runtime exception being thrown.

This article should reference the section on known pitfalls in the nullable reference types. In addition, that section should discuss other pitfalls, as shown in this article.