dotnet/roslyn

IDE0059 is not raised inside a code block with using keyword.

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#74.219 aperta il 1 lug 2024

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Area-IDEBugFeature - IDE0059help wanted

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Descrizione

Version Used: SDK 8.0.302 (4.11.0-2.final

Steps to Reproduce:

Write the following code:

public class Sandbox
{
    public void SimpleMethod()
    {
        using var _ = new MemoryStream();

        var jsonContent = JsonSerializer.Deserialize<Json>((JsonDocument)null);
    }

    public class Json
    {
    }
}

The IDE0059 rule is not raised for the not used variable jsonContent. But if we remove the using keyword:

public class Sandbox
{
    public void SimpleMethod()
    {
        var _ = new MemoryStream();

        var jsonContent = JsonSerializer.Deserialize<Json>((JsonDocument)null);
    }

    public class Json
    {
    }
}

The IDE0059 rule is raised to indicate that the jsonContent variable is not used.

We have the same issue if we use explicit code block for using keyword:

public class Sandbox
{
    public void SimpleMethod()
    {
        using var _ = new MemoryStream();
        {
            var jsonContent = JsonSerializer.Deserialize<Json>((JsonDocument)null);
        }
    }

    public class Json
    {
    }
}

Diagnostic Id: IDE0059: Remove unnecessary value assignment

Expected Behavior:

The IDE0059 rule should be raised when a local variable is not used, even if there is a non-related using code block.

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