IDE0072: False positive when using switch expression and pattern matching with "or" to default case

[seangwright]

Version Used:

> dotnet --version
6.0.101

Steps to Reproduce:

enum Greeting
{
    Hello,
    Goodbye
};

Greeting greeting = Greeting.Hello;

string message = greeting switch
{
    Greeting.Hello => "Hey!",
    Greeting.Goodbye or _ => "Not sure what to say 🤔"
};

Expected Behavior:

Does not trigger csharp(IDE0072) which states I need to "Populate switch".

Actual Behavior:

Triggers csharp(IDE0072).

Note

This is a common pattern for me because I don't want skip handling the specific case that has the same result as the default.

If I change the enum and remove Goodbye, I should get errors, but this analyzer error wants me to either duplicate the result value ("Not sure what to say 🤔") which means I have to make future changes in 2 places, or remove Greeting.Goodbye from the expression and have the default handle it, which removes an intentional reference to a specific value.

This is slightly related to this issue #50982

[CyrusNajmabadi]

@seangwright can you give a full example? The above code is illegal to begin with. I tried modifying it to make it legal, but i don't repro the problem you mentioned.

Thanks!

[Youssef1313]

@CyrusNajmabadi I can repro with the above code (just changed => to = so it does compile), and with the following .editorconfig:

[*.cs]

# IDE0072: Add missing cases
dotnet_diagnostic.IDE0072.severity = warning

Two problems I see:

• The reported false positive
  • The false positive makes sense to me per the product code:
    

    roslyn/src/Analyzers/Core/Analyzers/PopulateSwitch/PopulateSwitchExpressionHelpers.cs

    Lines 72 to 73 in d9ad24a

    	public static bool HasDefaultCase(ISwitchExpressionOperation operation)
    	=> operation.Arms.Any(a => IsDefault(a));

    
    IsDefault could be renamed to HasDefault and its implementation be modified according to the new name. This should have been done as part of Handle patterns in populate switch expressions #50984, but I haven't thought of this scenario.
• Duplicate diagnostic in IDE (If I enforced code style on build, there is only one diagnostic which is correct - so the duplication seems an IDE-only issue)