False positive CA1508 with Parallel.Invoke

[rampaa]

Description

    public static bool MyAwesomeMethod(bool doIt)
    {
        string? myAwesomeName = null;
        Parallel.Invoke(() =>
        {
            myAwesomeName = doIt
                ? "Banzai!"
                : null;
        });
        return myAwesomeName is not null;
    }

The code given above triggers the following warning: CA1508 'myAwesomeName is not null' is always 'false'. Remove or refactor the condition(s) to avoid dead code.

But ideally speaking, the given code should not trigger CA1508 because at the point we check the value of the object, it can have a non-null value.

Reproduction Steps

1. Add <AnalysisLevel>9-all</AnalysisLevel> to the csproj file
2. Compile the code given in the Description section

Expected behavior

CA1508 shouldn't get triggered because at the point we check the value of the object, it can have a non-null value.

Actual behavior

CA1508 is being triggered

Regression?

No response

Known Workarounds

No response

Configuration

.NET 9

Other information

No response

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[stephentoub]

This isn't specific to Parallel.Invoke; whether Parallel.Invoke will invoke the delegate is part of Invoke's implementation, which the analyzer/compiler isn't privvy to, and thus it doesn't know that Invoke is guaranteed to invoke the delegate... this would be the case for any other such method that accepted a lambda/delegate.

That said, the analyzer really shouldn't be issuing this diagnostic here, simply because it can't know whether the code is dead or not.