Switch expressions cannot infer shared type

[dkmiller]

Version Used:
Visual Studio Version 16.0.3 + dotnet core 3.0.100-preview3-010431

Steps to Reproduce:

object Foo(string x)
{
    return x switch
    {
        "a" => 1,
        "b" => "hi",
        _ => throw null
    };
}

Expected Behavior:

Given the signature of Foo, the compiler should be able to infer that the return type of the switch expression is object.

Actual Behavior:

The compiler returns error

CS8506 C# No best type was found for the switch expression.

If I add a cast to object in any of the cases in the switch statement (e.g. "a" => (object)1) then the code compiles.

[svick]

I believe this is the expected behavior for the current preview version of C# 8.0. But it will almost certainly behave the way you suggested in the final version of C# 8.0, see dotnet/csharplang#2389.

[dkmiller]

@svick that's great to know, and very exciting news! I think this issue can safely be closed then.