Unnecessary assignment incorrectly marks the variable as unnecessary

Version Used: VS 2019 16.8.0 Preview 2.1

Steps to Reproduce:

Have code like the following open in VS:

int F(bool condition)
{
    int variable = 0;

    if (condition)
        variable = 1;
    else
        variable = 2;

    return variable;
}

Expected Behavior: IDE0059 “Unnecessary assignment of a value” highlights the assignment of 0 to variable as unnecessary:

int variable[| = 0|];

Actual Behavior:

The variable itself is highlighted as unnecessary by IDE0059, indicating that the variable should be removed, not just the assignment:

int [|variable|] = 0;

If you actually run the code fix, it does the right thing, i.e. it only removes the assignment (and also the empty line, for some reason):

[mavasani]

I believe this is by design. Note that by attempting to fade some other location, we are trading one problem for another.

1. If we decide to fade the entire = expr, the expression on right might even span across multiple lines, so fading the entire equals value clause is also not really desirable. Additionally, user might feel the evaluation of expr is unnecessary, which is not always true as evaluating expr might have side effects. The code fix will not suggesting removing the assignment for such a case, but replace the left side with a discard.
2. If we decide to fade only the =, it will hardly be visible, if at all. Additionally, I am not sure how do we handle the unnecessary assignment for an out variable like below:

The current approach of fading the left hand side is designed to indicate an unnecessary write or unnecessary store, not an unnecessary variable. I don’t believe fading any other location would help here.

[Youssef1313]

https://github.com/dotnet/roslyn/blob/e16d3906a6d6a560da72144a942dbac7c8dc2e11/src/Analyzers/CSharp/Analyzers/RemoveUnusedParametersAndValues/CSharpRemoveUnusedParametersAndValuesDiagnosticAnalyzer.cs#L62

Probably this will be a good start in debugging. I’ll give it a try soon.